Simple SiC TX

[Stretchyman]

Having designed what I think is the limit of my skills (40W Gan, programmable DDS) I've decided to build a much simpler Tx to reduce cost and increase interest! (Hopefully...?)

Having recently discovered CARDINAL CPP oscillators (thank's to someone on here, Cheers!!) it greatly simplifies design.

I now have a Simple SiC TX with ONLY 17 components.

I've found a UK company to wind Mod Tranny's for me and will get the cases milled at source for a decent finish.

Frequency changing is as simple as plugging in a new oscillator and as they're <$5 I think it's a good way to go.

I've had one on the air and no complaints of any sort, rock steady and very efficient with class D Modulator and class E RF stage using C3M CREE SiC mosfet.

Should be ready in a month or so and will advertise on eBay but please get in touch directly and save yourself some $/£.

ALL the Best and Happy New Year.

Stretchy.

[Monophonia]

Being able to order those oscillators from Digikey on frequency is a plus, If I ever make something that is truly fixed frequency I may explore those.

[Stretchyman]

Just counted up the amount of components it has replaced, =41!

Current design has programmable DDS which SW needs to be written for etc (at cost as I didn't write it myself), that and a filter and an amplifier and a squarer to drive the driver, lots of bits!

For anyone wanting to build a simple TX just use the 'usual' class E design replacing the 74HC240 with a CPP oscillator and the FET driver of your choice.

I'm trying to find a source for cheap 'unprogrammed' oscillators (DUAL ones preferably), ANYONE?

DK seem to charge more for those than programmed ones, which is weird. Programmers aren't cheap either but will get one if I can get the OSCs cheap!


Str.

[Echoqueen]

For anyone wanting to build a simple TX just use the 'usual' class E design replacing the 74HC240 with a CPP oscillator and the FET driver of your choice.

Hi!

I can only source TC4422? Are those drivers ok for 7 MHz?

Thanks
EQ

[JimIO]

I think so. I had looked into it and ordered some from china on ebay but I never got them. 

   http://www.ece.ualberta.ca/~ee401/parts/data/TC4421.pdf

[redhat]

I have not had good luck with 4422 above medium wave.  4452's work, but you'll need the to-220 versions to get rid of the heat.  The DIP-8 versions will smoke...been there.

+-RH

[Stretchyman]

Why not use something a tad more modern?
 
NCP81074ADR2G.

It's what I use in this design.

Please forget the ones you mention as they're old, slow and obsolete. FET drivers have moved on a lot. Even smpsu's are running at 4 MHz now!

Str.

[Stretchyman]

Images here;

https://www.ebay.co.uk/itm/133036900946?ssPageName=STRK:MESELX:IT&_trksid=p3984.m1555.l2649

Check out the PCB, small, simple & class E so rather efficient.

You wont find a simpler or more efficient design, rugged too!

Quite happy to sell bare (or populated) PCB's, if you want to sort out your own modulation scheme.

Please ignore the inflated eBay prices, much cheaper if you buy direct!

Str.

[redhat]

Please forget the ones you mention as they're old, slow and obsolete. FET drivers have moved on a lot. Even smpsu's are running at 4 MHz now!

I take it you forgot how to read again?  He said...

"Hi!  I can only source TC4422? Are those drivers ok for 7 MHz?"

The parts you mention are not usable by the average hobbyist without reflow equipment.  The ones I mentioned are available in through hole and also a TO-272 smd package which is with care practical for most folks.

+-RH

[Stretchyman]

The older devices aren't very good, just generate a lot of heat and aren't very fast either.

The NCP's are available in a SOIC 8, 'bout half the size of a DIP 8 so fairly easy to solder with the naked eye. X4 eyepiece is however the preferred method, no reason to be shy of small things!

Look, I'm nearly 60 years old, my eyesight ain't that good! I guess the main issue is most folk don't have a decent soldering iron?

METCAL being the tool of choice.

Str.

[Echoqueen]

HI folks

Ok, undestood. Thanks for the advice.

The main issue is not the size of the components but the fact that I cannot buy the new-and-faster ones here. They are unobtanium for me right now.

There are some ixys that are mentioned elsewhere in the forum that maybe I could get.

Cheers.

[OgreVorbis]

HI folks

Ok, undestood. Thanks for the advice.

The main issue is not the size of the components but the fact that I cannot buy the new-and-faster ones here. They are unobtanium for me right now.

There are some ixys that are mentioned elsewhere in the forum that maybe I could get.

Cheers.

I know from personal experience that the 4422's are no good above 5 MHz. The NCPs I am about to test in a few days.
If you can't source those, then get the IXDN614's. I know these work at 7 MHz if the board is done right.

[Stretchyman]

I can send you some, no problem.

You can buy anything from anywhere surely?

As long as you're on the same planet!

Where are u bud?

Str

[redhat]

Granted, a lot of the suitability will depend on how large of a gate structure your trying to drive...but I've found with most of the SiC and conventional mosfet below 1000pF work fine to 7 MHz with the '614s and '4452's  I eventually settled on the 614's largely because the tab is tied to ground, and this simplified mounting and heatsinking.

Stretchy, your rambling are unfounded.  The IXDN614's have nearly identical switching times to your specs of dust, and are easier to replace.  I also worry about the longtime durability of a part that does generate heat and can't get rid of it.  For the same reasons I had DIP-8 versions of the 4452's melt down while the tabbed versions were fine.

Sometime in the future a new PA layout is in order...2 RF fets for 1.5KW, 4 for 2.5KW...carrier that is.  5KW in 5 rack units, for the power modules anyway....wow.

+-RH

[Stretchyman]

Well I must apologize!

I have an unfounded attitude to make things small!

The 'Specs of dust' don't get that hot BTW...

Regards.

Stretchy.