572B Breadboard Linear Amplifier – oh, the insanity!

Filed Under (Amplifiers, DIY Electronics Projects) by Jonathan on 21-02-2011

Today I bring you a video by “bob4analog” on YouTube. His version of a breadboard is slightly different from mine!!!!

Really detailed description of his project and a great tour of it in operation. I have a 572 based amp and found this quite interesting. Others, may just find the layout utter insanity! I really thank him for posting this video, it was interesting and I did indeed learn a few things while watching this video.

From his video description:

An experimental ‘Breadboard’ Linear Amplifier for 80m, using two 572B tubes.


JBOT – An SSB linear amplifier made from Just a Bunch of Transistors

Filed Under (Amplifiers, Homebrew, QRP) by Jonathan on 10-08-2009

Since I lost some time on the site when I broke my foot, I thought I’d drop a few bonuses for you guys this week.

I have an earlier post on the BitX 20 that generated quite a bit of attention.  Farhan has done a lot of great work on that project that has a HUGE online following.

Many have noted that there were some issues with the amplification of this transceiver and it may take a bit to get it going.  Farhan has mentioned this on his site as well:

For many of us, getting hold of high power RF transistors is impossible. They are also expensive and easily blown. In the last decade, hams have pressed the power MoSFETs into use as RF devices. This has been a mixed success. The power FETs (mostly the IRF series for International Rectifiers) have very high input and output capacitance, they need higher drain voltage and they are very non-linear devices. As result, IRF device based RF power amplifiers have remained beyond easy replication for the average homebrewer.

Often, the RF power amplifiers are run flat-out without any attempt at stabilizing the performance, This has to lead to a lot of grief.

The BITX’s linear amplifier painfully illustrates both these issues. The IRF510 takes a lot to get it going. Many of those who scratch build it on their own often found themselves struggling with stability and insufficient power output.

I heard about Farhans’ new project and thought I’d mention it here as it can work pretty well for those of you that have already built a BitX 20.

His JBOT page is at:


Free vintage technical books online

Filed Under (Amplifiers, Homebrew, Radio/Comm. History, Reference Material) by Jonathan on 11-11-2008

Man, this site is a gem!

When I teach a new ham class, I usually advise the normal 3 books for a new ham.  Operater Manual (I tell them they only need this one when they get started), Handbook (I usually say about 1 from each decade is OK, no need to get one every year), and the Antenna Book (same needs as a handbook, about one a decade).  I never did understand the collecting of these books every year they get updated.

Now, that being said, I also like to look at the old books and magazines and learn.  I have about 5 Handbooks, 3 Antenna Handbooks and every QST since 1938 bound.  OK, I do enjoy pulling an old book or QST over a coffee when I wake up.  There is a feeling that pulp can give you that electrons on the monitor can’t.

That being said, I have binders of books I’ve printed out and this site was a big contributor to my addiction.  Pete Millett.  He sums up the reason for his site better than I can:

Preserving the Knowledge of the Ancients?

I’ve found that most of the technical books published before about 1964 never had their copyrights renewed, so now are in the public domain.  So I am endeavoring to digitize and post some selected books relating to the “vacuum tube age” of electronics here.

Some examples:

Amplifier Builders Guide, Hugo Gernsback, 1947, 64 pages
Audels Radiomans Guide, Edwin P. Anderson, 1945, 880 pages
Basic Radio – The Essentials of Electron tubes and their Circuits, J. Barton Hoag, 1942, 379 pages
The Cathode-ray tube at Work, John F. Rider, 1935, 336 pages
Coyne Electrical and Radio Trouble Shooting Manual, Coyne Electrical School, 1946, 612 pages
Electron-Tube Circuits, Samuel Seely, 1950, 530 pages
Electron Tube Design, RCA, 1963, 943 (!!) pages – Courtesy of John Atwood
Electronic Amplifier Circuits, Joseph Petit and Malcolm McWhorter, 1961, 325 pages
Electronic Circuits and Tubes, Cruft Laboratory at Harvard University, 1947, 994 pages – Courtesy of Jim McConville
Electronic Transformers and Circuits, Reuben Lee, 1955, 349 pages – Courtesy of John Atwood
Getting the Most Out of Vacuum Tubes, Robert Tomer, 1960, 164 pages – Courtesy of John Atwood
The Radio Handbook, William Orr (editor), 15th edition 1959, 810 (!) pages

And a whole lot more.

But wait!, if  you act now……

OK, I had to throw it in there, he has a lot of information for headphone amplifiers on his site as well.  Various homebrew amps and pictures of those that have built them.  Nice tube homebrewed amps too!

http://www.pmillett.com/index.html – This page has a lot of his headphone amp and home audio DIY amongst others.

http://www.pmillett.com/tecnical_books_online.htm – this is the link with the technical links listed above.

Great resource and I’ve gotten a lot out of reading this material.

Thanx Pete!

Homebrew six meter amplifier

Filed Under (Amplifiers, Homebrew, Six Meters) by Jonathan on 09-11-2008

I’ve had this site bookmarked for a couple years now, seems too good not to share.

G3WOS six meter, DXpedition solid state amp, packed and ready to go!

This amp is a solid state, 450W beauty that is truly light (I don’t think I’d like to carry around one of them huge solid hollow state jobbies, even though they are nice!).

WARNING!  This is not a first amplifier project.  I’m still building several small QRP amps for a reason – 4,000 volts DC can do a little damage.

Chris set about some design criteria based on several homebrew amps he had used in the past.  This criteria included:

I was determined to have a go designing one with the following key objectives. It needs to:

  • be as light-weight as possible to minimise excess baggage costs.
  • be compact so that it can be transported as aircraft hand-baggage.
    (As it turned out, the final amplifier weighed in at 39lbs compared
    to the 70lb weight of the ACOM 1000!)
  • operate from either a 120 or 240 volt mains supply.
  • be reliable.
  • run up 1,500 watts for possible moon bounce operation subject to local licensing regulations.
  • have full fault protection.
  • be able to take the blower off in transit.
  • be robust to resist damage it it gets dropped.
  • be balanced with the weight distribution centralised so that it can be hand carried.

Lofty planning ideas indeed!

I really like the way Chris laid this site out with all the planning and such (including the cardboard box stages of layout design).  He also includes a plethora of information so that someone can actually take this challenge on, on their own.


Here are a few pics and the link below.  Take your time, plenty of information here!

Top view of the finished project

Bottom view of the finished amplifier



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