A Ferrite Rod Loop for NDB DX: Generation 3

Resonant Loops (RLs) are an often overlooked form of receiving antenna, but remain my favorite, both from a performance viewpoint and also from a viewpoint of passion: I love the things! Although they are not by any means as popular as their remote cousins, the Shielded Magnetic Loop (SML), RLs can in some environments offer performance which an SML simply cannot match. With careful design and construction, RLs can exhibit a very high loaded Q which can give the loop:

1) A very high degree of frequency selectivity right in the antenna, often to the point where additional front end filtering is not necessary to protect the receiver from spurious responses. Case in point: in my area, there are a number of 50 kW MW stations, and to use my Wellbrook SML for NDB DXing, I MUST use a 9th order lowpass filter. Such a filter is not needed when DXing NDBs with a Ferrite Rod RL.

2) A very low Minimum Discernible Signal; RLs can have a sensitivity which belies their size.

3) RLs tend to be amplified loops, but a high Q in the antenna can drastically reduce the gain requirements of the following amplifier.

4) A well balanced RL will generally exhibit strong directionality. In some loops at some frequencies, an RL can discriminate reception based on the arrival azimuth. Peaks and nulls may be observed. At the very least, an RL can discriminate against local noise, and I have observed noise depression of up to 30 dB when I have had an RL mounted on a rotator.

5) An RL tends to be small, and can generally be sited in a quiet area on one’s lot to keep it away from power or utility lines, houses, etc.

As well as their advantages, RLs as a receiving antenna have a number of disadvantages.

1) Without band switching (and this is not always feasible), RLs have a finite tuning range (Fmax over Fmin), and this is generally within the range of 3:1 to 5:1. This tends to make an RL an “Application Specific” antenna.

2) The lack of commercial offerings means that you are most likely going to have to roll your own; RLs tend to be a construction project by the user.

3) There are countless gripes on the internet by users who dislike the fact that they must be re-tuned constantly as the receiver frequency is changed. They have missed the point by a country mile; the magic in a RL is in its narrowband nature and mo’ narrow mo’ better. Generally.

4) Although physically small (we are talking about small receiving loops here), to fully realize the sensitivity which a small RL can offer, the RL MUST be sited outdoors. This complicates the tuning of the loop, as the capacitance used to tune the loop MUST be located physically close to the loop winding. Using varactors to tune a loop remotely is pretty easy, but if the target Q of the loop requires the use of a mechanical variable capacitor (as this LF Ferrite Loop does), then it becomes a substantially more complicated process to tune the loop remotely.

5) RLs are generally considered to be unshielded and thus prone to signal corruption from local RFI. This is not true, and most resonant loops can be built with an effectice electrostatic shield.

Over the past winter and spring, I have been working on a prototype of a Ferrite Rod RL which would be suitable for DXing LF NDBs. Some of the progress and logs have been posted here:

http://www.hfunderground.com/board/index.php/topic,19471.0.html

http://www.hfunderground.com/board/index.php/topic,19868.0.html

http://www.hfunderground.com/board/index.php/topic,20896.0.html

I have been extremely encouraged by the performance of the prototypes, and have been working on a “Generation 3″ version of the loop which should be deployed by this fall. I cannot do much about the first 2 “disadvantages” listed above, but the G3 loop and its control system are being designed to attack problems 3 and 4 head on, and offer some functionality which will greatly aid in the DXing of LF NDBs. Some of the key points are:

1) Design of a Stepping Motor Gear Train which will allow precise tuning of a mechanical variable capacitor located out near the loop site (about 160 ft away). In the current design, there are approximately 4800 motor steps per full 180 degree traverse of the tuning capacitor, which is just about the minimum required for the loaded Q of this Ferrite Rod RL.

2) Utilization of an Arduino SBC in the loop head. The Arduino firmware implements a Server (a simple command interpreter) which will control the Geared Stepping Motor used in the gear train via a standard off the shelf Stepper Shield for the Arduino. It will also allow control of additional loop parameters from within the shack.

3) The system will be controlled (tuned) via a Client application which will run on the same computer as the SDR control app (at this point I am using SDR Console V 1.5). At this point, RC is coded against a small subset of the SDR Console CAT Command vocabulary, but more is possible in the future.

n.b. There have been a large number of design decisions to make in this project. The choice of the SDR control program to code against (at least initially) was kinda critical. I have 2 favorites: SdrDx and SDR Console, and I have been able to programmatically control both via apps I have written. As good as SdrDx is (and it is very very good), I prefer using the older version of SDR Console (the version with the infinite license) for NDB DXing. Its ability to present full screen views of the waterfall and spectrum without control clutter is a huge aid in DXing, and its ability to simultaneously display a Zoom window with a span of 2 or 5 kHz really aids in fine tuning a loop. Additionally, I really love the palette control in SDR Console; quick very fine adjustments in the palette allow the app to function as its own QRSS viewer, and the ability to visually DX piled up NDBs really lessens the fatigue you encounter when trying to hear a particular NDB in a pileup. The fact that communication with SDR Console is easy via a free Virtual Serial Port Manager (such as VSPE) is a big plus.

4) The Client app (at this point boringly named Remote Controller or RC) will encapsulate a number of functional blocks in individual Tab Pages in a TabControl in the following categories:

A) Server Connection/Transactions: This page contains the controls to open, maintain, and handle a network connection to the Loop Server out in the yard.

B) Tuning/Memory Lists: RC will implement a set of tuning controls, some of which are programmable, to accomplish Loop and Receiver tuning. RC will enable the user to create Memory Lists which are displayed in a ListView Control, and which can act as a tuning source by double clicking an item in the list. I consider this to be a very powerful feature which might help in DXing NDBs this fall. I imagine loading in a general list of NDBs at the start of a session to gauge what cards the Great Gods of Propagation has dealt out. From these “prop beacon beacons”, I might determine, for example, that commonly heard stations in Nunavut are in well, and I could then prepare (­­or load in a previously prepared) Memory List of Nunavutian NDBs to see if I can hear anything new without having to navigate through the online RNA list.

C) Station Database: In NDB DXing, I find the RNA NDB list to be absolutely indispensable. RC has the ability to import a prepared copy of the RNA Excel download file, and this list is displayed in toto on a tab page in RC. RC displays the list in a CheckedListView Control. Double-clicking an item will execute it (tune the Loop and also the Receiver to the NDB frequency). Individually selected items can be checked and exported to a Memory List. The list is searchable (by call with wildcards, by ITU country, by State/Province, etc.). Search results can be exported to a Memory List. This means that it is a very simple process to generate a custom Memory List for all NDBs in Alaska, for example.

D) Receiver: RC can open and maintain a connection via a Virtual Serial Port to the SDR Console app running on the same Windows box. Tuning the loop can simultaneously tune the SDR to the RL resonant frequency (right now the accuracy is about +/- 2 kHz), but fine tuning of the loop is easy. In fact, in NDB DXing, the RL is more often than not tuned to one of the sideband frequencies, and not the carrier referenced in frequency lists.

E) Calibration/Testing: Since a calibration curve of the antenna response (motor steps versus resonant frequency) is required, RC contains Antenna Calibration functionality which allows a semi-automated approach to antenna calibration. Calibration Curve data can be viewed graphically. RC also implements a number of built-in test suites which can be used to test the loop, receiver, and rotator performance, and can help the app to function as a tool for further development.

F) Rotator/Amplifier: Since RNA logs also contain a Maidenhead Locator field, from this Longitude and Latitude can be easily computed; this allows further computation of both Bearing to the NDB and also Range. I am adding control of a modified Antenna Rotator to the client app RC so that selecting an item in either a Memory or RNA list would (with one double-click) tune the Loop, tune the SDR, and rotate the Loop to the proper Azimuth. Rotation can then be manually controlled once it is at the proper az.

G) Profile/Settings: RC supports a Profile file, and uses it to store settings between sessions. The user can generate a profile which can be used to control various types of loops.

H) Normally, a Memory List item will contain all RNA fields, and when double clicked, the antenna and SDR will be tuned, and the rotator will be spun to the azimuth which can be computed from the RNA Maidenhead locator field. This azimuth will be the bearing of peak rod reception, but more often than not, this will not be the desired antenna bearing; one would in theory like to rotate the antenna to the bearing which will possibly give the best reception considering all of the co-channel NDBs which would interfere with the desired NDB. The loop generally has a broad reception peak and a narrow null (or depression) minima, and we would like to have these in the proper orientation with respect to co-channel interference.

RC incorporates a Scenario Visualization tool. Right clicking an item in the RNA list will open the Visualization dialog. This will present a polar plot of Bearing vs Range on which all potentially interfering NDBs will be plotted, as well as the target NDB. The plot will also render markers representing the Peak and Null beams of the antenna, and these will be rendered with variable width beam widths. The antenna patterns can be rotated with respect to the plotted NDBs, and the user can select a best guess antenna rotation for the target NDB. This target RNA entry can then be exported to a Memory List, and any time the item is double clicked in the Memory List, the rotator will be rotated to the preferred (and not the Maidenhead) azimuth. This will enable me to create Memory List of highly desired high value targets, and will allow me to efficiently check these targets in any DX session.

A Block Diagram of the system is:

Block Diagram

Well, that is an overview of what is going on here. This post will be followed up by at least 3 more posts. The first will discuss some of the technology in the Ferrite Rod RL (the wound rod, the capacitor, and the amplifier) and its tuning mechanism. That is pictured below in a weatherproof enclosure.  The rod per se is not visible, but is located within the aluminum shield above the enclosure.

IMG_0530

The second will discuss the Client app to a greater degree, and a screencap of a typical presentation (along with the typical SDR Console window) is:

Screen Shot

The third will most likely discuss interfacing strategies, as this loop is sited a fur piece from the house, and requires and RF coax, power cabling, and also some form of digital network over which the client and server communicate

I am getting lazy in my old age, but we will most likely throw up a post detailing Rack Shack Rotator modification (converting from the ghastly and slow synchronous motor to a PM DC gearmotor, adding a position feedback pot, and a simple closed loop controller based on an Arduino Pro Mini controller which may be hosted by the Loop Server).

Additionally, the Scenario Visualization tool will most likely merit its own post. This has been one of the funnest parts of this project, and I foresee this tool being a great aid this next season.
Visualization

There is also a long laundry lists of enhancements on the back burner, and we might get around to posting some of these ideas in the future.

Further on down the line we can post some results with regards to performance; there is a lot to evaluate.

This has been – and continues to be – a ton of fun, and also hard work. This antenna represents “where I always wanted to be” with regards to Resonant Loop antennas. This is a big step up from what I used last season, and there is still enormous potential, and lots of new functionality to imagine and implement.

If only the freakin’ thing works…

Liquid Radio 5/2/2015 received on Westmoast Coast

Yup, Liquid Radio’s little carrier wave usually fades in and out at my locale. Sometimes I’ll hear thumps but I’ve had to use USB demodulation in order to hear it.  But last night I could hear music using AM demodulation and I wanted to share!

It helps to use big speakers when listening.

Liquid Radio, 6925AM, 0327utc, 5/2/2015

 

 

Shortwave Pirate Radio 2014 – A Year In Review

To gauge shortwave pirate radio activity in 2014, I analyzed the loggings to the HF Underground (http://www.hfunderground.com) message board. A computer script parsed the message thread titles, as well as the timestamps of the messages. This information was used to produce some statistics about the level of pirate radio activity. Of course, as Mark Twain has written: “There are three kinds of lies: lies, damned lies, and statistics.” Still, let’s see what we can learn.

There were 12,722 messages posted to 1,975 unique threads, that’s an 11% decrease in the number of messages over 2013. Ideally, each thread represents an individual pirate station transmission. Also ideally, each message posted to a thread represents one logging. In reality, there is some error involved.

First, we can look at the transmission mode used:
AM 944
USB 776
LSB 49
CW 32
FM 16
SSTV 46
UNKNOWN 112

AM beat out USB this year, last year they were virtually tied, and if we assume (as likely) that the cases where no mode was reported are one of these, account for virtually all of the transmission.

SSTV was broken out just to show about how many SSTV transmissions there are, these of course are almost all transmitted in USB mode. Also, these are cases where SSTV is in the logging title, which means that the transmission was probably just SSTV, vs a station that also happened to transmit SSTV as part of the program.

Next, we can see how much activity there is for each day of the week:

Sunday 387 (20%)
Monday 155 (8%)
Tuesday 189 (10%)
Wednesday 223 (11%)
Thursday 230 (12%)
Friday 331 (17%)
Saturday 460 (23%)

As one might expect, Saturday and Sunday are the big winners, with Friday in third place. But don’t give up on weekday listening! 40% of transmissions are on a Monday through Thursday.

We can also look at the number of logging threads per month, to gauge activity:

Here’s a graph showing the number of broadcasts per day of the year that were logged:

Halloween was very busy this year!

We might be interested in knowing the best time of the day to try for a station. Here’s a plot of the start times of the logged broadcasts, binned
by UTC hour of the day:

As you might expect, evening Eastern Time is the best, roughly 2300-0300 UTC, with a broader peak of lower activity from roughly 2000-0500 UTC. There is some activity in the morning to afternoon time period, and very little during the wee hours.

The next question is where to tune. As one might expect, 6925 kHz was the clear winner:

3229 kHz: 18
3395 kHz: 4
6150 kHz: 7
6280 kHz: 9
6769 kHz: 5
6770 kHz: 50
6771 kHz: 6
6772 kHz: 9
6849 kHz: 4
6850 kHz: 10
6867 kHz: 5
6873 kHz: 10
6875 kHz: 19
6876 kHz: 16
6880 kHz: 26
6885 kHz: 4
6900 kHz: 7
6910 kHz: 6
6913 kHz: 6
6915 kHz: 6
6919 kHz: 16
6920 kHz: 21
6924 kHz: 102
6925 kHz: 885
6926 kHz: 6
6927 kHz: 5
6928 kHz: 6
6929 kHz: 11
6930 kHz: 117
6931 kHz: 4
6932 kHz: 4
6933 kHz: 4
6935 kHz: 103
6940 kHz: 62
6945 kHz: 31
6948 kHz: 7
6949 kHz: 27
6950 kHz: 103
6951 kHz: 10
6955 kHz: 12
6960 kHz: 10
6965 kHz: 5
6969 kHz: 4
6970 kHz: 5
6974 kHz: 6
6975 kHz: 7
9600 kHz: 9
9605 kHz: 14
9610 kHz: 4
11595 kHz: 11
15655 kHz: 15
15695 kHz: 4

6925, along with 6924 kHz, account for 50% of logged transmissions.

The most popular station logged is of course “UNID”, short for unidentified. In the world of shortwave pirate radio, there’s a number of transmissions where no ID is given. There’s also many cases where no ID could be heard, due to poor conditions. For 2014, there were 651 threads with 2,788 loggings where no station ID was given – that’s almost 33% of the threads.

Here’s the complete list of all stations with two or more logging threads:
UNID (651)
Radio Free Whatever (112)
YHWH (106)
Old Time Radio (87)
XLR8 (70)
Radio Ga Ga (45)
Undercover Radio (37)
WRR (34)
Captain Morgan (33)
Wolverine Radio (30)
The Crystal Ship (29)
Radio True North (27)
Blue Ocean Radio (26)
Liquid Radio (25)
Cool AM (24)
Channel Z (21)
KCPR (21)
Red Mercury Labs (19)
PPVR (18)
WHYP (17)
Pirate Radio Boston (16)
The Bangalore Poacher (16)
Rave On Radio (15)
MAC Shortwave (15)
Orbital Mind Control Satellite (14)
XFM (13)
Happy Hanukkah Radio (13)
Turtlehead Radio (12)
Man Cave Radio (12)
Radio Gallifrey Intergalactic (12)
Renegade Radio (11)
Make Your Liver Quiver Radio (11)
Northwoods Radio (10)
Rattlesnake Radio (10)
Generation Wild 100 (10)
Radio Ronin (9)
Insane Radio (8)
Boombox Radio (8)
WRMR (8)
CYOT (7)
Toynbee Radio (7)
COOLAM (7)
Big Dawg Radio (7)
Twangy Radio (6)
Son of the Lincolnshire Poacher (6)
WPOD (5)
Appalachia Radio (5)
Metro Radio International (5)
WAHR (5)
Vo Mongolia (5)
WMID (5)
Chairman Of The Board Radio (5)
Aggressive Policeman Station (5)
Hit Parade Radio (4)
Radio Dr Tim (4)
Looking At You Radio (4)
Peskie Party Radio (4)
L0DE Radio Hour (4)
The yodeler (4)
Free Thinker Radio (4)
Radio Jingle Bells (4)
KMUD (3)
WBNY (3)
Random Radio (3)
BZN (3)
PBS Underground (3)
Radio Paisano (3)
WJFK (3)
Radio Halloween (3)
KIKI Radio (3)
Radio Plate Current (3)
Drifting Crystal Radio (3)
Artem Radio (3)
Don’t Panic / Sirens / Ebola (3)
KIPM (2)
Chamber Pot Radio (2)
Northern Relay Service (2)
Radio Bleh Bleh (2)
Hot Legs Radio (2)
Hard Tack Radio (2)
Radio Casablanca (2)
Mushroom Radio (2)
Germany Calling (2)
Radio Azteca (2)
XEROX (2)
Pseudo Radio (2)
Hot Radio (2)
WHJR (2)
Mysterious Mystic Radio (2)
Left Lane Radio (2)
Radio Marlene (2)
Voice of Honor (2)
Pumpkin Patch Radio (2)
Satan Radio (2)
Turkey Breast Radio (2)
Drunken DJ Radio (2)
Radio Jihad (2)
Indira Calling (2)
WPDR (2)
Blues Traveler (2)
WMFQ (2)
Radio Music Bed (2)
Radio Underground (2)
The Great Pumpkin (2)
Lord Hee Haw (2)
London Calling (2)
Radio Free ADD (2)

Another thing we can look at are the number of posts in a logging thread for each station. Note that there is the likelihood of some duplicate posts by the same user for each thread, so these figures may be slightly inflated:
Radio Free Whatever (935)
XLR8 (558)
Wolverine Radio (529)
YHWH (511)
Captain Morgan (398)
Undercover Radio (372)
Radio Ga Ga (322)
The Crystal Ship (320)
WRR (312)
Old Time Radio (301)
XFM (220)
MAC Shortwave (177)
Channel Z (174)
Liquid Radio (173)
Blue Ocean Radio (159)
Radio True North (157)
Cool AM (147)
WHYP (146)
Pirate Radio Boston (133)
Radio Ronin (129)
Renegade Radio (129)
Generation Wild 100 (128)
KCPR (121)
Orbital Mind Control Satellite (121)
Northwoods Radio (116)
Rave On Radio (108)
Red Mercury Labs (104)
The Bangalore Poacher (94)
Man Cave Radio (85)
PPVR (74)
Radio Gallifrey Intergalactic (73)
Insane Radio (72)
CYOT (70)
Drunken DJ Radio (70)
WMID (68)
Happy Hanukkah Radio (67)
Twangy Radio (66)
Turtlehead Radio (62)
Big Dawg Radio (57)
Radio Jingle Bells (56)
Boombox Radio (52)
Make Your Liver Quiver Radio (52)
Vo Mongolia (49)
Chairman Of The Board Radio (49)
Peskie Party Radio (49)
Metro Radio International (46)
COOLAM (43)
Radio Marlene (41)
Radio Dr Tim (38)
WPOD (37)
Hit Parade Radio (33)
Son of the Lincolnshire Poacher (33)
Free Thinker Radio (32)
Toynbee Radio (31)
Rattlesnake Radio (30)
Indira Calling (29)
WRMR (28)
L0DE Radio Hour (28)
BZN (25)
PBS Underground (25)
Radio Paisano (25)
Pumpkin Patch Radio (25)
Radio Casablanca (24)
WAHR (22)
Drifting Crystal Radio (22)
Radio Music Bed (22)
Artem Radio (22)
Northern Relay Service (20)
Radio Bleh Bleh (20)
Radio Plate Current (20)
Don’t Panic / Sirens / Ebola (20)
XEROX (19)
KMUD (18)
Random Radio (18)
WJFK (18)
WHJR (17)
Radio Underground (17)
Appalachia Radio (16)
The Great Pumpkin (16)
Radio Free ADD (16)
Pseudo Radio (15)
Turkey Breast Radio (14)
Aggressive Policeman Station (14)
Hard Tack Radio (13)
Radio Halloween (13)
The yodeler (13)
London Calling (13)
Mysterious Mystic Radio (12)
Germany Calling (11)
Left Lane Radio (11)
Satan Radio (11)
Radio Jihad (11)
Looking At You Radio (10)
KIKI Radio (9)
Mushroom Radio (8)
Lord Hee Haw (8)
Hot Legs Radio (7)
Hot Radio (7)
WBNY (6)
Radio Azteca (6)
WPDR (6)
Blues Traveler (5)
WMFQ (5)
Chamber Pot Radio (4)
KIPM (3)
Voice of Honor (3)

Next we can calculate the ratio of logging messages per thread, to gauge, in general, how many people reported hearing each station:
Radio Free Whatever 935 112 8.34821
XLR8 558 70 7.97143
Wolverine Radio 529 30 17.6333
YHWH 511 106 4.82075
Captain Morgan 398 33 12.0606
Undercover Radio 372 37 10.0541
Radio Ga Ga 322 45 7.15556
The Crystal Ship 320 29 11.0345
WRR 312 34 9.17647
Old Time Radio 301 87 3.45977
XFM 220 13 16.9231
MAC Shortwave 177 15 11.8
Channel Z 174 21 8.28571
Liquid Radio 173 25 6.92
Blue Ocean Radio 159 26 6.11538
Radio True North 157 27 5.81482
Cool AM 147 24 6.125
WHYP 146 17 8.58823
Pirate Radio Boston 133 16 8.3125
Renegade Radio 129 11 11.7273
KCPR 121 21 5.7619
Orbital Mind Control Satellite 121 14 8.64286
Rave On Radio 108 15 7.2
Red Mercury Labs 104 19 5.47368
The Bangalore Poacher 94 16 5.875
Man Cave Radio 85 12 7.08333
PPVR 74 18 4.11111
Radio Gallifrey Intergalactic 73 12 6.08333
Happy Hanukkah Radio 67 13 5.15385
Turtlehead Radio 62 12 5.16667
Make Your Liver Quiver Radio 52 11 4.72727

One risk here is that the same transmission could be logged in two, or even more, threads, which would reduce this ratio,

We can then sort these by ratio:
17.6333,Wolverine Radio
16.9231,XFM
12.0606,Captain Morgan
11.8,MAC Shortwave
11.7273,Renegade Radio
11.0345,The Crystal Ship
10.0541,Undercover Radio
9.17647,WRR
8.64286,Orbital Mind Control Satellite
8.58823,WHYP
8.34821,Radio Free Whatever
8.3125,Pirate Radio Boston
8.28571,Channel Z
7.97143,XLR8
7.2,Rave On Radio
7.15556,Radio Ga Ga
7.08333,Man Cave Radio
6.92,Liquid Radio
6.125,Cool AM
6.11538,Blue Ocean Radio
6.08333,Radio Gallifrey Intergalactic
5.875,The Bangalore Poacher
5.81482,Radio True North
5.7619,KCPR
5.47368,Red Mercury Labs
5.16667,Turtlehead Radio
5.15385,Happy Hanukkah Radio
4.82075,YHWH
4.72727,Make Your Liver Quiver Radio
4.11111,PPVR
3.45977,Old Time Radio

Avg Ratio 7.98728

This year’s results are somewhat less straightforward, due to a station nicknamed “Old Time Radio”. It has transmitted almost 24/7 (with some breaks for a few days) since around April, usually on 6770 kHz, but also sometimes around 3229 kHz. Sometimes the same logging thread was used for several days worth of loggings. How many transmissions has it made? Sometimes it has been on for weeks at a time. Certainly in terms of the number of hours transmitted, it is the most active pirate radio station by far for 2014. No other station comes close.

Voice of Khaatumo

1700-1730 …t… 17580 VO Khaatumo – Somali
Copied 12/11/14 1700z sign on – fair to good signal. S5-8
Used USB due to AWR on 17575 – helped a lot.
Open with music into OM in Somali.
Considering the multiple mentions of Somalia during the show, I’m guessing this is targeted there – not sure of Xmitting site.
Off about 1729 after music.
Here’s the open & the close.
Hope you like,
FPE

Shortwave Pirate Radio 2013 – A Year in Review

Yes, I’m about 11 months late in getting this out… but better late than never! Your comments are certainly appreciated, as well as suggestions for additional data you’d like to see for 2014.

To gauge shortwave pirate radio activity in 2013, I analyzed the loggings to the HF Underground (http://www.hfunderground.com) message board. A computer script parsed the message thread titles, as well as the timestamps of the messages. This information was used to produce some statistics about the level of pirate radio activity. Of course, as Mark Twain has written: “There are three kinds of lies: lies, damned lies, and statistics.” Still, let’s see what we can learn.

There were 14,287 messages posted to 2,461 unique threads, that’s a 64% increase in the number of messages over 2012. Ideally, each thread represents an individual pirate station transmission. Also ideally, each message posted to a thread represents one logging. In reality, there is some error involved.

First, we can look at the transmission mode used:
AM 1077
USB 1091
LSB 26
CW 48
FM 18
SSTV 42
UNKNOWN 159

AM and USB are virtually tied, and if we assume (as likely) that the cases where no mode was reported are one of these, account for virtually all of the transmission.

SSTV was broken out just to show about how many SSTV transmissions there are, these of course are almost all transmitted in USB mode. Also, these are cases where SSTV is in the logging title, which means that the transmission was probably just SSTV, vs a station that also happened to transmit SSTV as part of the program.

Next, we can see how much activity there is for each day of the week:

Sunday 533 22%
Monday 226 9%
Tuesday 257 10%
Wednesday 228 9%
Thursday 269 11%
Friday 376 15%
Saturday 572 23%

As one might expect, Saturday and Sunday are the big winners, with Friday in third place. But don’t give up on weekday listening! 39% of transmissions are on a Monday through Thursday.

We can also look at the number of logging threads per month, to gauge activity:

Since the overall popularity of the HF Underground continues to grow, there is possibly some inflation in the number of threads as the year goes on.

Here’s a graph showing the number of broadcasts per day of the year that were logged:

We might be interested in knowing the best time of the day to try for a station. Here’s a plot of the start times of the logged broadcasts, binned
by UTC hour of the day:

As you might expect, evening Eastern Time is the best, roughly 2300-0300 UTC, with a broader peak of lower activity from roughly 2000-0500 UTC. There is some activity in the morning to afternoon time period, and very little during the wee hours.

The next question is where to tune. As one might expect, 6925 kHz was the clear winner:

6850 kHz: 14
6900 kHz: 7
6919 kHz: 6
6920 kHz: 41
6921 kHz: 17
6923 kHz: 5
6924 kHz: 116
6925 kHz: 1360
6926 kHz: 5
6929 kHz: 15
6930 kHz: 147
6931 kHz: 12
6933 kHz: 6
6935 kHz: 143
6936 kHz: 4
6937 kHz: 8
6938 kHz: 7
6940 kHz: 92
6945 kHz: 58
6949 kHz: 24
6950 kHz: 170
6951 kHz: 13
6955 kHz: 34
6960 kHz: 7
6965 kHz: 5
6966 kHz: 7
6970 kHz: 6
6974 kHz: 5
6975 kHz: 27
13875 kHz: 7

6925, along with 6924 and 6926 kHz, account for 60% of logged transmissions.

The most popular station logged is of course “UNID”, short for unidentified. In the world of shortwave pirate radio, there’s a number of transmissions where no ID is given. There’s also many cases where no ID could be heard, due to poor conditions. For 2013, there were 677 threads with 2,554 loggings where no station ID was given – that’s almost 28% of the threads.

Here’s the complete list of all stations with two or more logging threads:
UNID (677)
Red Mercury Labs (128)
Radio Free Whatever (98)
Blue Ocean Radio (87)
Radio Ga Ga (65)
Rave On Radio (63)
Boombox Radio (63)
PeePee Vagina (56)
Radio True North (52)
Wolverine Radio (43)
Pirate Radio Boston (43)
Radio TOTSE (39)
Radio Echo One (37)
Radio Ronin (33)
Captain Morgan (32)
Undercover Radio (31)
The Crystal Ship (30)
Radio Gallifrey Intergalactic (26)
XLR8 (25)
Twangy Radio (22)
Metro Radio International (20)
WGWR (20)
XFM (19)
Pseudo Radio (19)
Renegade Radio (18)
WBNY (17)
Liquid Radio (16)
Turtlehead Radio (15)
Mysterious Mystic Radio (15)
Channel Z (13)
Radio Jamba International (13)
MAC Shortwave (13)
Northwoods Radio (12)
Black Cat Radio (12)
Happy Hanukkah Radio (12)
Toynbee Radio (11)
Chamber Pot Radio (11)
Hit Parade Radio (11)
The Late Movie (11)
BOCHF (10)
WMPR (9)
WFMT (9)
Insane Radio (9)
Man Cave Radio (9)
Partial India Radio (9)
PBS Underground (9)
CYOT (8)
WPOD (8)
Radio Azteca (8)
All Aboard Radio (8)
My New Underpants (8)
The Big Q (8)
Cool AM (7)
WFUQ (7)
Rattlesnake Radio (7)
WJFK (7)
All Along The Watchtower Radio (6)
Appalachia Radio (6)
XEROX (6)
Hot Radio (6)
Rebel Radio (6)
Left Lane Radio (6)
Hard Tack Radio (5)
Grizzly Bear Radio (5)
Pirates Week Relay (5)
Vo Pancho Villa (5)
KAMP (5)
Voice of Bacon (5)
Tea Party Radio (5)
LTO Radio (5)
WAZU (4)
EAM Guy (4)
Radio Casablanca (4)
Radio Therapy (4)
SDF1 (4)
CHKN (4)
Sharon Radio (4)
Edmund Fitzgerald Radio (4)
Fruitcake Station (4)
Radio Dr Tim (4)
KAOS (3)
KIPM (3)
WPON (3)
Eccentric Shortwave (3)
Big Boobs Radio (3)
Hot Legs Radio (3)
Mushroom Radio (3)
XENU (3)
WUBR (3)
Radio Marlene (3)
Radio Paisano (3)
Voice of Honor (3)
NOEL (3)
WCS (3)
Radio Free Speech (3)
WAHR (3)
Witch City Radio (3)
The Edge (3)
KPZL (2)
Ann Hoffer Live (2)
Radio Strange Outpost 7 (2)
Radio Morania (2)
Radio First Termer (2)
Radio Whatever (2)
BZN (2)
Vo American Indian (2)
Hello Radio (2)
PPVR (2)
Radio Cinco De Mayo (2)
Radio Snausages (2)
Mouth of Mohammed (2)
WFUZ (2)
Kennedy Assassination News (2)
Voice of the Robots (2)
YHWH (2)
Turkey Breast Radio (2)
WSBR (2)
Radio Jihad (2)
Victory Radio (2)

Another thing we can look at are the number of posts in a logging thread for each station. Note that there is the likelihood of some duplicate posts by the same user for each thread, so these figures may be slightly inflated:
Red Mercury Labs (945)
Radio Free Whatever (740)
Wolverine Radio (559)
Blue Ocean Radio (427)
Rave On Radio (377)
Boombox Radio (335)
Radio Ga Ga (334)
Radio True North (318)
The Crystal Ship (308)
PeePee Vagina (268)
Radio Echo One (253)
Undercover Radio (237)
Radio TOTSE (234)
Radio Ronin (222)
Pirate Radio Boston (222)
Captain Morgan (213)
Radio Gallifrey Intergalactic (207)
Twangy Radio (206)
Renegade Radio (196)
XLR8 (188)
MAC Shortwave (150)
XFM (149)
Metro Radio International (142)
Black Cat Radio (129)
Radio Jamba International (115)
Liquid Radio (106)
Partial India Radio (103)
WGWR (99)
Northwoods Radio (91)
PBS Underground (90)
WBNY (89)
Channel Z (83)
The Late Movie (82)
Mysterious Mystic Radio (81)
Pseudo Radio (78)
Insane Radio (75)
WMPR (71)
BOCHF (71)
WFMT (59)
Turtlehead Radio (59)
WPOD (57)
Hit Parade Radio (57)
Appalachia Radio (56)
Toynbee Radio (55)
Radio Marlene (55)
Man Cave Radio (54)
Happy Hanukkah Radio (53)
CYOT (51)
Hard Tack Radio (51)
Cool AM (50)
WJFK (48)
LTO Radio (47)
Chamber Pot Radio (46)
Grizzly Bear Radio (43)
EAM Guy (40)
Edmund Fitzgerald Radio (36)
WFUQ (35)
Voice of Bacon (34)
All Aboard Radio (33)
My New Underpants (33)
Radio Azteca (32)
Left Lane Radio (32)
XEROX (31)
Mouth of Mohammed (31)
KIPM (30)
All Along The Watchtower Radio (30)
Radio Casablanca (29)
KAMP (29)
KAOS (27)
The Big Q (27)
Witch City Radio (27)
SDF1 (26)
Sharon Radio (26)
Rattlesnake Radio (25)
WPON (24)
Hot Legs Radio (24)
Radio Paisano (24)
WAZU (23)
Mushroom Radio (23)
CHKN (23)
Voice of Honor (23)
Big Boobs Radio (21)
Vo Pancho Villa (21)
Radio Cinco De Mayo (21)
Fruitcake Station (21)
Voice of the Robots (20)
Radio First Termer (19)
Hot Radio (19)
WSBR (19)
Eccentric Shortwave (17)
NOEL (17)
WAHR (17)
Radio Snausages (16)
Rebel Radio (15)
Tea Party Radio (15)
KPZL (14)
Radio Morania (14)
Pirates Week Relay (14)
XENU (13)
BZN (12)
YHWH (12)
Radio Dr Tim (11)
Radio Free Speech (11)
Ann Hoffer Live (10)
PPVR (10)
Kennedy Assassination News (10)
WCS (10)
Turkey Breast Radio (10)
Radio Jihad (10)
Victory Radio (10)
Radio Therapy (9)
WFUZ (9)
Radio Whatever (8)
WUBR (8)
Vo American Indian (7)
Hello Radio (6)
The Edge (6)
Radio Strange Outpost 7 (2)

Next we can calculate the ratio of logging messages per thread, to gauge, in general, how many people reported hearing each station:
Red Mercury Labs 945 128 7.38281
Radio Free Whatever 740 98 7.55102
Wolverine Radio 559 43 13
Blue Ocean Radio 427 87 4.90805
Rave On Radio 377 63 5.98413
Boombox Radio 335 63 5.31746
Radio Ga Ga 334 65 5.13846
Radio True North 318 52 6.11538
The Crystal Ship 308 30 10.2667
PeePee Vagina 268 56 4.78571
Radio Echo One 253 37 6.83784
Undercover Radio 237 31 7.64516
Radio TOTSE 234 39 6
Radio Ronin 222 33 6.72727
Pirate Radio Boston 222 43 5.16279
Captain Morgan 213 32 6.65625
Radio Gallifrey Intergalactic 207 26 7.96154
Twangy Radio 206 22 9.36364
Renegade Radio 196 18 10.8889
XLR8 188 25 7.52
MAC Shortwave 150 13 11.5385
XFM 149 19 7.84211
Metro Radio International 142 20 7.1
Black Cat Radio 129 12 10.75
Radio Jamba International 115 13 8.84615
Liquid Radio 106 16 6.625
WGWR 99 20 4.95
Northwoods Radio 91 12 7.58333
WBNY 89 17 5.23529
Channel Z 83 13 6.38462
The Late Movie 82 11 7.45455
Mysterious Mystic Radio 81 15 5.4
Pseudo Radio 78 19 4.10526
Turtlehead Radio 59 15 3.93333
Hit Parade Radio 57 11 5.18182
Toynbee Radio 55 11 5
Happy Hanukkah Radio 53 12 4.41667
Chamber Pot Radio 46 11 4.18182

One risk here is that the same transmission could be logged in two, or even more, threads, which would reduce this ratio,

We can then sort these by ratio:
13,Wolverine Radio
11.5385,MAC Shortwave
10.8889,Renegade Radio
10.75,Black Cat Radio
10.2667,The Crystal Ship
9.36364,Twangy Radio
8.84615,Radio Jamba International
7.96154,Radio Gallifrey Intergalactic
7.84211,XFM
7.64516,Undercover Radio
7.58333,Northwoods Radio
7.55102,Radio Free Whatever
7.52,XLR8
7.45455,The Late Movie
7.38281,Red Mercury Labs
7.1,Metro Radio International
6.83784,Radio Echo One
6.72727,Radio Ronin
6.65625,Captain Morgan
6.625,Liquid Radio
6.38462,Channel Z
6.11538,Radio True North
6,Radio TOTSE
5.98413,Rave On Radio
5.4,Mysterious Mystic Radio
5.31746,Boombox Radio
5.23529,WBNY
5.18182,Hit Parade Radio
5.16279,Pirate Radio Boston
5.13846,Radio Ga Ga
5,Toynbee Radio
4.95,WGWR
4.90805,Blue Ocean Radio
4.78571,PeePee Vagina
4.41667,Happy Hanukkah Radio
4.18182,Chamber Pot Radio
4.10526,Pseudo Radio
3.93333,Turtlehead Radio

Avg Ratio 6.88793

Yet Another Loop Post

I have been very happy with the Resonant Loop which I have been using for the last couple of years; it has served me well, and will undoubtedly continue to do so in the future. It’s time to move forward, and push it’s capabilities a bit further. My current loop has a loaded Q of approximately 250 at 6925 kHz, and this results in a 3 dB bandwidth of around 28 kHz. This allows the tuning to be rather forgiving at the expense of being absolutely incapable of doing any significant frequency discrimination right within the antenna. To do so will require a loop with a higher Q, a significantly higher Q, and that will not happen using the technology of my current loop.

The loaded Q of a Resonant Loop is primarily determined by 3 things:
– The Q of the winding inductance. To get to the Q levels required, the best practical solution would be to wind the coil with a relatively large copper tubing; stranded wire is no longer practical here.
– The Q of the tuning capacitor. While the tuning diodes used in my current loop really make life easy, they just will not have enough Q at frequencies in the funny band. A high quality mechanical variable capacitor (or vacuum variable capacitor) will be required.
– The impedance presented by the buffer amplifier must be increased. The easiest way to do this is by using the loop windings as an impedance transformer to raise the effective input impedance of the amplifier.

After a lot of number crunching and simulations, I built the following prototype:

IMG_0408

This is shown in a “testing position”, and a mast mount has not yet been built. A quick description of the loop follows.

The loop winding was built from 1/2″ OD soft copper refrigeration tubing, and was designed so that it could be fabricated from a 20′ length of tubing which is commonly available in DIY stores. The preliminary loop inductance is around 11 uH, and at 7000 kHz this winding should exhibit a Q of around 3000. The mean diameter is around 11.5″, and there are 6 turns with a 1″ spacing between turns. Note that copper sweat and brass compression fittings are used to create a solid loop mount to a bar of UHMW; these fittings are mechanical only, and are not part of the electrical circuit.

The capacitor used here is a purchase from Fair Radio Sales a number of years ago, and was a pull from a military ATU. As variable caps go, this is almost as good as it gets. The cap features solid brass construction, and is silver plated in entirety. All insulation is ceramic, and all plate joints appear to be silver soldered. The cap has a built-in 100:1 worm gear reducer with anti-backlash gearing. The measured capacitance range is 15-250 pF.

The windings and capacitor are connected by cobbled up flexible tubular pipes fabricated from some coax cable jacket over which was wound some 0.010″ pure silver foil which was held in place by heat shrink tubing. These pipes are soldered to the capacitor stator and rotor lugs. At the winding end, they are currently clamped onto the copper tubing with SS hose clamps (the clamping area was first silver plated with Cool Amp silver plating powder). At some point, these will be soldered.

Currently, the capacitor is remotely tuned by a PM DC gearmotor via a coupling made from a short length of PVC tubing and cable ties. The power supply is 3 D cells lined up in series against my logbook; I just touch the wire ends to the battery terminals and try to remember which way tunes up and which way tunes down? I have another deck built using an identical variable capacitor coupled to a 100 step/revolution stepping motor which will be used when the control circuits are built.

The white PVC tube above the chassis contains the loop buffer amp. This is just the standard JFET cascode amp used in most of my loops with the exception that the tuning diodes have been removed. A close-up of the hookup:

IMG_0411

The loop tubing was drilled in 3 places to accept the barrels of male 1/4″ quick-connects, and these joints were then soldered. The loop amplifier is connected to these lugs. Note that this connection forms a 3:1 voltage transformer to the amp which results in a 9:1 amplifier input impedance transformation. The approximately 1 Meg amplifier input resistance now appears as a 9 Meg load on the capacitor-winding tank circuit which helps to keep the loaded Q high.

In starting this project, there were some known knowns. Primarily, I was pretty confident that a loop winding could be fabricated which would give me the proper inductance while at the same time giving me a required Q of around 3000. This build has proven that to me. There was also a major unknown known. It is extremely difficult to find hard data on the real Q of a mechanical variable capacitor of this type. The tubes are littered with vague statements which describe the Q of such caps as “very high”, “excellent”, and so forth. There are a couple of sites which have detailed Q information on a particular cap (which looked promising to me). But not this cap. Having built this loop, back calculations seem to suggest that the Q of this cap is somewhere around 1200-1500 at 6925 kHz, and this figure seems realistic to me.

My goal in this build was to raise the Q of a receiving loop by a factor of 2 or 3 from its current value of 250; I would be happy for a Q of 600. This would give an 3 dB BW of around 12 kHz at 6925; good, but not good enough to pry a pesc off of a pirate’s signal. So, what did we get?

To be honest, these results are preliminary, and vary all over the place. This is to be expected for such high Q circuits. The measurements can be tricky, and the results can be skewed by environmental things such as humidity, proximity to other objects, etc. At this point, Q measurements are consistently falling into a range between around 600 and 1050. I most commonly see values around 850 at 6925 kHz, and this thrills me to no end. A Q of 850 implies a 3 dB BW of around 8 kHz at 6925; if you squint, you can imagine that with a little more Q, some serious frequency discrimination can be accomplished.

How much more Q? I would LOVE to have a loop which exhibits a real 3 dB BW of 6 kHz at 6925; this would require a loaded loop Q of around 1150. At this point it is beginning to look realistic to me.

How do you get there with the current build configuration? One can calculate that at the current operating point (6925 kHz, Q = 850) that the LC tank circuit has a total effective series resistance of around 0.57 Ohms. I have gotten the greatest Q gains in the prototype by monkeying with the 2 connections between the winding and the capacitor, and I think that there is room for improvement there. Every milliohm counts. This particular capacitor also has the same Achilles heel that many variable caps have. the connection to the rotor. In this cap, there are 2 silver buttons on a spring loaded leaf, and these buttons wipe a silver commutation ring on the cap rotor. I have yet to do a really thorough cleaning of the sulphide layer on the ring, and have left this trump card in the back pocket. When I can no longer push the Q any higher, we will look here. There is also the possibility that this wiping contact can be replaced by a flexible silver tape, soldered to the ring.

There is a backup plan. This loop was built rigidly so that it would run in a stable manner at its tuned operating point. This would be a requirement for the next step, which would be to upgrade the loop to a so-called “regenerative loop” which could possibly supply some additional Q. More about this later.

In the few nights that I have used this for DXing, I have started to become familiar with the listening characteristics of this loop as compared to my standard loop. Although my current Neanderthal tuning supply makes it hard to peak the loop on a signal, the response peaks as seen on an SDR FFT plot are much more pronounced at Q=850 than they are at Q=250. With a 100 kHz view span, the 250 loop gives you a pretty good heads up look at a wide chunk of frequency spectrum; it’s hard to miss a weak signal off to the side of the loop response peak. Not so with the 850 loop; signals off to the side may be attenuated deeply, and it is quite possible to miss stuff.

On strong signal reception (say >= S7) it appears to be a coin toss between the 2 loops; both perform adequately. On weaker signals, I am giving the preliminary edge to the 850 loop. The 850 loop appears to be giving me better S/N ratio on weak signals, but I will hold this call until we are deeper into the season and storm noise lessens.

Which brings up another observation: when I had a wire antenna up, I noted that storm QRN as heard via the 250 loop was a lot “softer” than the crashes heard via a wire antenna. In the headphones, the storm noise was still there, but it tended to be less harsh and grating on the ears, and it was easier to “hear through” the noise on the 250 loop. I am noting now that storm QRN heard via the 850 loop is even mellower than that heard through the 250 loop. There is something going on there, as there is even a difference in lightning strike rendering in the SDR waterfall.

Well, enough for now.

Beginner’s Transmitter Building Saga

A few months ago I got a shortwave radio with side band reception and a digital readout and it opened up a very interesting realm of the radio waves: the open waters that radio pirates hijack and sail upon. With their antennas raised high like the mast of a ship, they risk their butts to give you…a radio show!

I learned that some pirates make their own transmitters. And I found that its about the only way to transmit besides an official transmitter that is expensive. They also need to be kind of unlocked to use the pirate frequencies that are out of the legal transmitting band allocated to licenced ham operators. With my interests raised, another obsession began (I think I have a hobby of trying different hobbies. Its either this or I get obsessed easily.) The goal was to make a transmitter. So I found multiple plans for radios but the work required in learning electronics terminology and parts was too great. I use an interest-to-energy-required ratio. I knew nothing of electronics besides wiring up car stereos. “I dont know any of this and I don’t want to research a bunch of stuff because I’m too lazy. How do I know it will even work?”

Then I found makerf.com that had plans for a simple transmitter. And its simplicity made the interest-to-energy-investment ratio favor the project. A friend had most of the parts laying around to make it: the LM386 integrated circuit, the 2222 transistor. What a coincidence, its my destiny! I just needed a crystal and a variable capacitor. I was also given a small bread board with wires. I am indebted to my generous friend!

label parts

3 stages

First I made the LM386 audio amplifier to power a small speaker and it e-f-f-i-n-g worked! And I smelled something hot—the LM386. It felt HOT too. So the next day I learned from a coworker the electricity just flows as fast as it can unless you throttle it. It went through the LM386 too fast and made it dangerously hot. You can start a fire with this stuff. Electronics: manly toys. It flowed through the speaker too fast so I put resistors between the amp and the speaker and that slowed down the current and worked. I held everything together with 2 hands surprisingly. Just enough to make contact and see it work.

lm386 circle circuit

Then I made the transmitter. Its coil was ramshackle, made from the enamel coated wire of an old RC car motor. You just coil it around the correct number of turns on a form the correct diameter. And I ordered the 2 other vital parts, a crystal and a variable capacitor. And IT effing worked! Eff yeah! It made morse code beeps on the side band mode of my receiver! So 2 for 2.

xmtr circle circuit

Then I combined the amp and the transmitter and I had music coming out. Its easy to combine them, its just one wire from the amp to the transmitter! That makes sense! It was kind of low audio but it had promise. What if it worked better with all the parts soldered up with a pretty looking coil? So I ordered parts online. I made sure to buy the capacitors that the schematics recommended for the amp because I wanted good audio quality.

LM386 datasheet. An integrated circuit has a circuit of transistors and resistors inside of it, but at a microscopic level. This LM386 integrated circuit has a sheet that describes what it does. And I was able to generally understand it! It wasn’t all obfuscated with geek jargon. Its a product and they WANT people to be able to understand what it can do so they’ll buy it. This particular IC is worth producing because lots of people want a little amplifier for their projects. Look at the size of my metal can transistor. Its a little bigger than a pencil eraser. Can you imagine they fit transistors in there?

Then I drew out the wiring. I chose to use a socket for the transistor and crystal because I figured they might get hurt and need replacing. Its a good thing because they go bad later. I got the idea for a socket from a portable AM radio from the 60s. I wound the filter, its not that hard and kind of fun. The filter makes it so you transmit over a small area of the spectrum. Otherwise you will transmit all over the spectrum and you might transmit where somebody needs it like ambulance drivers and their dispatch. You can cause an ambulance driver to drive off a cliff without filters! Just kidding about the cliff. Winding is menial. I believe humans were created to do menial tasks like grooming, carving, and preparing food. Knitting is great! But I digress.

drawing

close xmtr filter

Lo and behold the official thing all soldered up. It looked great, just like makerf’s. But did it work? Yeah it did. I don’t remember being all “eff yeah” about this one. I think it was more “yeah, you better effing work.” I spent a lot of hours on this. About 2 full days worth of drawing, forming wire, and soldering. I adapted a 12v battery pack that plugs in to turn it on (unplug to turn it off). A switch and LED indicator light would be nice. The great thing about making it official was the ease of use. I didn’t have to hold everything together with tape and clothespins. I could turn it on and leave it now. My hands were free to turn the capacitor for tuning.

official pic

A friend loaned me an oscilloscope. The stuff you only see on TV. I was a bad-ass laboratory doctor now baby. I still want to use it in the garage with the door open and the screen facing out so the neighbors can see how much of a laboratory doctor I am….Turning the capacitor made a difference. The sine wave wasn’t very siney. I wish I made this when I was taking trigonometry. Prior, I found no use for trigonometry whatsoever. Good thing I took it twice so it stuck a bit more than the other useless crap. Too bad chemistry didn’t stick after taking it twice. Yes I’m bitter after obtaining a college degree and feeling the lack of good jobs available.

oscope

So I would “tune” it (twist the cap and watch the waves change). Nothing looked very “clean”. When I did this I also had the receiver on side band mode and the morse code beep would change tone as I adjust the cap. I don’t know what “clean” means for sure but I think it means a smooth wave with no sharp jagged points on it. Both the crystal and the transistor would get HOT sometimes. But it kept on working so I figured no harm done. Sometimes I didn’t have 50ohms worth of resistors between the antenna’s + and – output which is a no-no. Transmitting antennas have this same 50ohm property. I guess this throttles it, otherwise too much energy will go through the transistor and get it hot like it did my LM386? I don’t know. Use a non-conductor to twist the capacitor. I use a carved wooden stick. A metal screwdriver will change things when it gets near the transmitter. Just my finger will change the sound of the beep it makes as I move it around the transmitter. Pretty cool.

Here’s the first sine wave hooked up to ground and antenna out:
first sine wave

Here’s another with the oscilloscope probe touching the positive antenna out lead: (you can watch as a song with base really change the amplitude as the song plays)
latest sine wave

Tuning observations: I twist it until it doesn’t work. Then I slowly twist the other way and a nice small sine wave shows up. The audio sound is weak. Then continue twisting slowly until it jumps and gets jagged and the sound is louder and fuzzy. A little more and the sound is as accurate as it gets. Any further and the treble is lost. And if it is overmodulated I turn down the volume on my audio device.

While turning the capacitor I accidently flicked the crystal and the transmitter stopped working. There’s an actual piece of a quartz crystal inside a container. Did you know that if you compress quartz it creates a small electrical current? The conspiracy theorists aren’t so crazy now are they. In reverse, if you add electric curent to a crystal it will vibrate. Oscillate is the way the laboratory doctors describe it. And depending on the thickness of the crystal it oscillates a certain number of times per minute. So 6.925mHz oscillates a different number of times per minute than 6.935mHz. Anyhow, thanks to the hfunderground forum members I learned that I probably needed a physically bigger crystal. Its called an FT-243 style and mine looks like its 100yrs old and was exumed by Indiana Jones from a cave. I had originally used a small crystal meant for computers. It would do well for morse code. But its not cut out for continual use apparently. Or being flicked while hot and oscillating.

So it worked once again. Meanwhilst I installed a computer processor fan to the transmitter case to keep things cool. Otherwise transistor gets hot when the transmitter is on. The fan works great but if I wire up the fan to the transmitter power supply it makes a clicking sound in the received transmission! So I hooked up a 9v battery to the fan so it has its own separate power source for optimal fidelity.

pic with fan

Speaking of optimal fidelity, I didn’t like how the sound is pretty quiet compared to other stations. Its probably my coil because its not perfect. (I’m just joking, I think the coil doesn’t really have to be that perfect because my ramshackle coil worked ok). If I turn up the sound more than half way on my .mp3 player it gets all nasty sounding and its called overmodulating. You’ve heard it before. It kind of sounds like when you turn the volume up on a sound system past the point that your speakers can handle it and it gets distorted. But it happens when the volume is not very high. Well, my LM386 amp puts out a small 0.5Watts of power. So would it sound better if I had 0.75W? Well, I removed my LM386 and temporarily used a 20W amp in its place. I chose the left channel, put the black wire to ground and the red to the transmitter. Yup. But you see, I started with the volume all the way down and I slowly turned it up. But the sound was still low and nothing bad was happening so I turned it up more and then it started sounding pretty good but I smelled burning. And it stopped transmitting. And my 20W amp stopped too (it has built in protection and it still works). My transistor smelled like the culprit, but wasn’t that warm cause the fan was on it. Anyhow I was up an running with a spare I had just in case this happened. Good thing I put a socket on there. The thing is more powerful now! I think my original transistor got weakened from the heat I put it through so I’m glad I broke it and got it out of the way. However the sound is still quiet, it just transmits sound farther. Like out of the room…into the yard. Eff yeah! Then I plugged my computer sound output into the transmitter and it was louder! Not perfect but better than the .mp3. So after tests, .mp3 and discman are quieter than computer and laptop outputs. Hmmm.

How the transmitter works. 3 parts:
Audio amplifier/modulator: The .mp3 player goes into the amplifier. This makes it strong enough to send to the transmitter.
The transmitter: works by magic. Seriously, I don’t know how it works. I know the recipe for it is on makerf.com . The crystal makes the frequency. The current changes direction in the coil really fast…I’m pretty sure…
Antenna: I know that the antenna works by induction. If you have electricity in the air, a wire will pick some of it up. So you have the coil with the oscillating energy with music data added to it. Wrap a wire around the coil and it will pick up the power. Put the filter between this and the antenna. Send it on its way through the filter and out to your transmitting antenna, into the atmosphere where it bounces off of special layers of ions back to the Earth a hundred and more miles away. I heard Border Hunter radio the other day and they are in Europe! You know he uses one of these babies…not really. His has more magic.

If its working and then quits, I think the only variables that break are the LM386, the crystal, and the transistor. Or heat has melted the solder between joints. My interest grew as I made this. This growing interest fuels itself so I am willing to expend more energy into working on it. Its even more important than my internet addiction. I’m talking about general time wasting on the internet that just wastes the time. Really, how important is a blow dart gun video? (note to self: google how to increase night vision) Now I have an actual book about antennas that I’m actually reading. I can’t transmit without a good antenna otherwise I might burn out a transistor. Wow, I just realized I can put that notch in my belt. There are those that have blown transistors and then there’s everybody else. I plan to get a ham radio license and test this baby out on the air. If anything, the morse code will transmit farther than the audio. I learned morse code from an iPhone app. Use the internet for good, not for time wasting blow dart gun videos.

From start to finish my project took me 4 months and I have a part time job and an internet addiction to fight.

I will share the total price (shipping included):
small crystal $19
magnet wire $16
audio jack $6
radio parts from mouser $19
toriods and antenna jacks (not used yet) $15
more transistors $8.50 (shipping was about $6)
big crystal $12.50
crystal socket $13

Total: $109 (Dr. Phil’s audience gasps and whispers)
This doesn’t include perf board $6 and LM386 a couple dollars. And the effing time and energy I put into it $200 (more gasps)

It was worth it! :) I am proud of it. 8)

UPDATE June, 2014

Well, with my newly acquired ham license, I finally tried my transmitter with 2 antennas: an adjustable inverted V and an inverted L with a ground radial. I tried both antennas through an antenna tuner. As well as the inverted V without a tuner (because it was resonant on the frequency I wanted and therefore theoretically had a good impedance and thus no need for a tuner).  Well, it hardly transmitted out of my yard.

I think the reason could be:

-that my circuit wires are too long (they rout down to the socket with the transistor and back up)

-that my coil could be tuned better

So if I were to invest the time and effort to make this go farther I would first try to shorten the circuit wires (solder the transistor directly and don’t use the socket). And second, find out the resonance of my coil. I think a noise bridge could be used for this but I’m not sure.

 

UPDATE UPDATE: January, 2015

Some fine electronics sages at HFU have some improvements on the design! To make it louder, give it more power.  I was using the LM386 N1 which is weaker than the LM386 N3.  Wimpy wimpy wimmmmpy.

So, this wise man’s advice to make better: “my gut tells me to place a very large value capacitor (250 uf or greater) in the line between the audio chip and the oscillator and put a resistor of say 16 ohms from the audio chips output to ground.  The Capacitor will pass the audio but will keep any DC current from entering the audio chip.  The chip might (I say might) not like having DC entering the output of the audio chip.

If I were to try this circuit I would use a 380 chip and not the 386 as shown.”

There you have it, sage advice. Literally. Thanks!

My thoughts: Hmmm, this sounds like it would fix the weak audio because if you amplify the audio on my stereo speaker system, they get louder.