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Author Topic: Need info for building solid state HF amplifiers  (Read 6671 times)

Posts: 339

« on: October 27, 2005, 06:30:31 PM »

I like solid state HF amps and would like to be able to construct my own.

I have seen the inside of several solid state HF amps and there isn't a lot of parts in there. It really looks like something that could be constructed at home.

So I am looking for a recomendation for a book or website on solid state amp building, something that also covers band filtering etc...An information source that is comprehensive but not too advanced would be great !

How difficult could it be ?

There has to be something out there.


Posts: 380

« Reply #1 on: October 28, 2005, 03:49:45 AM »

See: They can sell you either a complete kit for an amplifier or just the rare parts that you might not have. They also have Motorola datasheets for download. A rather large 600 watt solid state amplifier. Home of the Packer Amplifier, a 35 watt unit designed to give QRP rigs a bit more power.

And finally.............. Someone who has built a kilowatt solid-state amplifier.


Posts: 21764

« Reply #2 on: October 28, 2005, 09:31:55 AM »

There's a lot going on inside the "good" solid state HF amps.  It's not about the transistors, splitters and combiners, which can all be broadband enough to cover 160-10m (or sometimes 160-6m) fairly easily.

It's about all the bandswitched filter networks, and in the better (higher end) SS amps, the automatic antenna tuning networks.  If you look inside the Yaesu Quadra or the Icom PW-1, these are not "simple" amplifiers at all.   They have a lot more parts than equivalent tube amplifiers.


Posts: 2198

« Reply #3 on: October 28, 2005, 08:48:14 PM »

 Keep in mind, that the circuits you find from manufacturers (Engineering Bulletins, Application Notes, etc. etc. etc.) are almost always SUGGESTIONS, to spotlight the use of their device(s) and are usually NOT complete projects in and of themselves.  For example, while the Motorola EB 104 shows a circuit for a broadband 600 W. HF amp, it would NOT conform to (current U.S. FCC) Amateur standards for spectral purity and harmonic suppression; additional filtering would need to be included.  And THAT is sometimes the most difficult part of a project.

Posts: 3160

« Reply #4 on: October 29, 2005, 10:36:08 AM »

Richard -

Some complicated solutions can appear to be easy ("how difficult can it be") ..

Modern Solid State RF amplifier design and development can be traced to Motorola and most notably the theory to practical application work of Helge O. Granberg, K7ES/OH2ZE.
Helge was a Finnish-American amateur and ARRL
Technical Advisor for many years, passed away at his home in Phoenix, Arizona, January 16, 1996.  He was 63.

Helge wrote many technical articles on RF subjects for
amateur and industrial radio publications worldwide.  While living in his native Finland, he was one of the earliest pioneers in SSB technology (sometimes refered to as the "Arthur Collins" of Finland).  He also was an accomplished inventor and is well-known for the ''Granberg Transistor,'' on which he holds one of his many patents.

Communciation Concepts has many of the Motorola Application notes (bipolar and MOSFET RF transistor designs).

The January 1992 issue of RadCom (European amateur magazine) described a 150W HF linear amplifier by Mike Grierson, G3TSO.
This used another of Helge Granberg’s designs, with the actual amplifier being supplied in kit-form by Communications Concepts of Ohio, U.S.A.

Pieter Ibelings, N4IP 1 kW design, based on Helge's work:

RF Electronics


Posts: 9749


« Reply #5 on: October 30, 2005, 12:16:41 PM »

If you opened a solid state amp and it did not appear "complicated" it was probably a ratty dirty signal solid state CB amplifier without proper padding, filtering, combining , and bias.

I hope that crummy CB stuff never becomes popular for Ham bands, or we will all be in trouble!!!!

The suggestion about application notes and application kits being starting points is correct. They are just that, rough starting points. Virtually every one I've built, and I've built several, have required extensive changes to be stable and to meet FCC requirements.

73 Tom


Posts: 1146

« Reply #6 on: November 03, 2005, 05:00:18 PM »

I would like to see this thread go a little farther (or, is that further)...

I am also interested in solid state amps and I am currently pondering whether to buy one (the Icom IC-PW1) or build one.

From what I have read so far they are not simple.  I mean, they are not simple if you are going to extend the designs a bit -- this calls for a good understanding of solid state transistor performance plus the various other circuits that you want in such a creation.  Also, from what I have read, the construction techniques are possibly more demanding than building a tube amp.  Of course, the only tube amp I ever built was dual-811s and that was back in 1966.

Most of the cited references I have read or seen before.  They are good to acquaint you with enough knowledge to dispel that "simple" idea about solid state amplifiers.   Maybe we can get Tom, W8JI, to run an on-line tutorial over a period of several weeks on designing and building an amplifier.  In fact, if he treated it as an on-line class and charged money I would probably sign up.

Posts: 81

« Reply #7 on: November 10, 2005, 08:27:56 PM »

I have built the two transister (2sc2879) amp from the PCB from RF PARTS ($7.95) and you can get the manual for about $15.00 from them also. you get a parts list in the manual and you have to round them up yourself.
As you said not much to them and took about 2 days to build and get on the air.
I have built my own LP filter and will install in a few days.
Total cost was about $150.00
Not a beginner project but not too hard eather.
Good luck

Posts: 4380

« Reply #8 on: November 11, 2005, 10:01:03 AM »

See the latest QST (Dec. 2005) page 31-37 for "The SuperPacker HF Amplifier."  This is a 100 watt solid state amplifier using the Motorolla application notes design and the printed circuit board from Communication Concepts and more readily available transistors from RF Parts.  There is also a low pass filter setup using FAR Circuits pcb and switching relays and a built in SWR meter.
If you are interested in building a solid state amp and don't have great technical skills this looks like the place to go.  
I haven't built this one so my opinion is strictly "it looks pretty good."  But YMMV!

Posts: 2

« Reply #9 on: December 16, 2005, 08:30:50 AM »

Hi Rich...

I have begun a 600-Watt, solid-state, HF amplifier project.  I purchased the EB-104 from Communication Concepts, along with the copper spreader and the heatsink.  I have a transformer and power components from an old Ten-Tec killowatter that I bought used.

I chose 600 watts as the power output for two reasons: cost and power requirements.  I may upgrade it later, if it's successful, to 1kW, or more.

I plan to add cooling circuitry, including two 5-inch quiet, brushless fans, which  purchased from All Electronics for about $10.00 each.  They will be controlled by a circuit that will regulate their speed, rather than turn them on and off, to keep the noise to a minumum.

I have a plan for low-pass filters for all of the bands it will be used on, as well as protection circuitry "ideas".

I also have designed it to accept the 100-watt version, should I desire more power, without having to build the whole thing from scratch again.

I believe it will be an exciting project and I'm not discouraged by any design issues that are common - adressing those really is half the fun.

Don't get dicouraged if you really want to build one.  Just take your time and plan it out.  Ask a lot of questions and listen carefully to the answers.

My advice to you is to make sure you have the test equipment handy to test the output signal.  If you don't own it, borrow it, so you stay out of trouble.


Posts: 2

« Reply #10 on: December 16, 2005, 10:13:50 AM »

My previous messgae should read 1000-watt, not 100-watt.


Posts: 30

« Reply #11 on: May 06, 2006, 12:13:37 AM »

Hi Jim
I see you are building an amp from EB-104 design
I have also built one and are now looking for a good protection circuit that reacts fast enough to protect the xsistor life in case of any antenna fault or bandswitch error. I made one as per the  used in my previous amp project from CCI (300 W out from a pair of MRF422) but in EB104 (600-700 w)it seems not to be enough performant and some MRF150 finished its life.
the circuit is the classic with a directional coupler and the REF voltage applied to he gate of a tyristor cutting down the transistor which drives the TX relay.
I have come into the circuit used by Ameritron in ALS-600 similar amp, and are no great differences.

Tks  73's
Jose Miguel
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