Beginner class D design

[redhat]

Only took me two years!

PFFT!  as an RF engineer, you should have had it done in two weeks then!

+-RH

[Stretchyman]

Indeed!

I have to work as well!

However most of the time was spent doing the layout and sorting the hardware. Even punched out cheeks for the PWM inductor former. That and piddling around with a new PWM design that didn't work as expected (sortid now).

Anyway all this seems a bit mute as have offered the RF generator with no takers.

I will (eventually) have the whole thing boxed up with SWR detector etc but will double the price.

I'm happy to sell a 100W (400W pep) quad GaN RF GENERATOR for $250. Has built in AD9850 DDS with 16 programmable channels. 60V max will yield 600W and will need forced cooling. Happier passively cooled at 48V giving 400W. So Mod tranny at 24V or PWM at 48V.

This works seriously well, reports to prove!!

Str.

[Radio Station]

That's one of the reasons I just can't believe that the frankstein stuff over on the classeradio site actually works.  None of this stuff is plug and play, and I have to agree with Stretchy, a lot of the secret sauce to this is the layout design.
+-RH

Well the proof is in the operation of the transmitters for years on 160 and 75 meters putting out big power. Especially the 72 Fet one Steve WA1QIX runs. Go down to the AM window 3873 or 3885 and listen for a week and you will find out that the "frankstein stuff" really works.  It is just amazing. 

[redhat]

To each their own, but 72 fets....really?

three MODERN devices will suffice just fine, and prove just as reliable.

+-RH

[Stretchyman]

Yes I'm afraid they're somewhat behind the times, they're still Toob mad on there too.

As stated, designs on there are nearly 10 years old, nowt wrong with that but current technology has only been available for a year or so.

It's time to move on.

There's no point using bolt down FET drivers and FETs with high gate capacitance.

GaN devices easily driven with a SOIC sized driver all with 5V/8V.

AD9850 will directly drive SOIC FET drivers running at 8V which will switch GaN devices running at 150V.

That's what you should be using.

One chap on the AMFOAM (sic) website is doing just that. His name is Nigel I suggest reading his posts and looking at his designs as they are a tad more modern.

Str.

[redhat]

I will not make the jump to GaN until 1. the price comes down and 2. you can get decent power out of the devices.  Nothing personal, but if it can't do 1 KW + modulation with two devices, I don't want it.  Decent power requires beefy devices, and the GaN stuff just isn't there yet.  SiC is a good compromise, as the devices can produce decent power, and are reasonably priced.

+-RH

[Stretchyman]

True!

However vwith GaN you can drive them without using bolt down devices, I got fed up with drilling holes! That and the GaNs have a grounded tab so no washer needed.

All I wanted 400W at 48V.

I use SiC below 5MHz, GaN for 40m.

Str.

[redhat]

Your going to have to drill holes for the fets anyway...what's two more holes?

Bottom line; different design philosophy for different requirements.  Yours and mine are not the same.  I went the high voltage/lower current route, you did the opposite.

For my needs, my design makes more sense, and makes use of cheaper more readily available parts I can order from Digikey, Mouser, et al without reliance on one vendor.  SiC is available from Cree, Toshiba, Rohm, etc so at this time obsolescence is not a concern.

I just wish you would stop beating the drum for GaN, as what makes sense for you often doesn't make sense to everyone else.  There are folks out there who will be building tube linears and modulators until they'll have the make the tubes themselves.  Likewise, your going to have folks like 'QIX that think the only way to build solid state AM is their way.  I think in this case, he got lucky and wants to stick with what works, until he can no longer get the parts to build them.

 I have an eye on higher power, and for the time being, SiC is the way to get there....until something better comes along, at a reasonable cost.

+-RH

[Radio Station]

Your going to have to drill holes for the fets anyway...what's two more holes?

Bottom line; different design philosophy for different requirements.  Yours and mine are not the same.  I went the high voltage/lower current route, you did the opposite.

For my needs, my design makes more sense, and makes use of cheaper more readily available parts I can order from Digikey, Mouser, et al without reliance on one vendor.  SiC is available from Cree, Toshiba, Rohm, etc so at this time obsolescence is not a concern.

I just wish you would stop beating the drum for GaN, as what makes sense for you often doesn't make sense to everyone else.  There are folks out there who will be building tube linears and modulators until they'll have the make the tubes themselves.  Likewise, your going to have folks like 'QIX that think the only way to build solid state AM is their way.  I think in this case, he got lucky and wants to stick with what works, until he can no longer get the parts to build them.

 I have an eye on higher power, and for the time being, SiC is the way to get there....until something better comes along, at a reasonable cost.

+-RH

Very well started Redhat.

That's one of the reasons at this point I am not going into building a class E D H rig. If a really great new design comes along I may consider it. Until then I can go from 1MHz to 30 MHz with outstanding AM and SSB audio with no hassle in minutes with minimal tuning. One of the biggest limitations for me is class E D H is just AM only not SSB. SSB gets out better and can sound as good. But I still love AM too.

[Stretchyman]

Must ask, what have you built that covers the whole of HF, All mode?

Pray tell....

Str.

[TheRelayStation]

Must ask, what have you built that covers the whole of HF, All mode?

Pray tell....

Str.

in my opinion, it does not really matter whether you build it from scratch or modify and re-purpose existing equipment.
what matters is the meaning of your purposes behind it and whether you desire a high fidelity AM broadcast that is clean and spurious harmonic free.
in my case, i use a Yaesu FT-757GX2 (low level IF AM modulation mixer) that i modified and re-purposed extensively and exclusively for full duty 50W, hi fidelity AM broadcasting operation, it is no longer considered an "amateur" radio after the extensive modifications to it, it is strictly a 0-50W AM transmitter only.
since this radio includes all the necessary components to operate a clean and spurious harmonic free transmission, i purchased it on the cheap in a non-operative condition which i easily repaired and then modified, since i already have the original paper service manual, its preferred by me over building one from scratch.
this type of re-purpose and modification can be done easily to any solid state "amateur" radio up to the manufacture year of 1990 (the older, the easier) but with extreme difficulty to post millennium models due to having 2-3 layer PCB's with micro-traces, tiny surface mounted components and "all in one" integrated circuits (IC's) making target modifications nearly impossible.
in conclusion, there are many solid state older "hybrid" non-working "amateur" transceivers available dirt cheap on several market places that can be repaired, then modified at less than the total cost of building one from scratch.
i took this approach simply because i dont have the time or patience to design, fabricate and build one to the desired specifications.
FYI - the FT-757GX2 modified TX audio frequency response is 5Hz to 20Khz as tested but i broadcast with a frequency response of 20Hz to 10Khz using "Stereotool" as the final sound/modulation processor.

[Radio Station]

A another great point.

[Stretchyman]

A another great point.

I'm definitely missing out on something here!

Ah well....neh mind!

Refering to the title of the post I don't see what relevance repurposing a ham radio has at all?

Time and patience, Yes, plugging in a ham radio, anyone can do that.

We're talking about design, which you make clear you have absolutely no idea of.

I've spent years trying to get that right, I'm not there yet but will continue to try.

Str.

[Radio Station]

A another great point.

I'm definitely missing out on something here!

Ah well....neh mind!

Refering to the title of the post I don't see what relevance repurposing a ham radio has at all?

Time and patience, Yes, plugging in a ham radio, anyone can do that.

We're talking about design, which you make clear you have absolutely no idea of.

I've spent years trying to get that right, I'm not there yet but will continue to try.

Str.

You are getting confused in our old age my friend comming to the conclusion about what was said by "The Relay Station " not by "Radio Station"

I never said I have not built or designed anything . Next time before you make your comments spend the time needed to read first before you make your condescending comments.

[Stretchyman]

Another great point then?

I think not.

Str.