Jerry,
Let me join the chorus of well-wishers in the group encouraging you to take
the plunge! It's very satisfying to build your own QRO amplifier, and I
think you'd find it to be enormously educational.and fun as well. You're
fortunate that the circuit diagrams and parts layouts are pretty well
standardized for basic amplifiers, so you don't need to reinvent the wheel.
Here are a couple of suggestions. First, while I agree that a beginning amp
builder is unlikely to produce a work of art, I'd recommend you don't set
the bar too low for yourself. The biggest contributior to sloppy
workmanship, IMHO, is rushing too much rather than taking one's time and
carefully thinking through each step in advance. Try to make everything you
do look as neat and professional as you can, and if you're not pleased with
the result on a particular step, then do it over. You want to end up with an
amplifier you can be proud of.
Second, don't bite off more than you can chew. A simple triode monoband amp
is much easier to build (and get working!) than a bandswitched tetrode amp.
Furthermore, try to keep the plate voltages as low a value as is consistent
with the amp's power requirements. It's much easier to work with 2000V than
with 4000V.
Third --and I'll probably get some flak for suggesting this -- don't be
penny wise and pound foolish. When you're dealing with high voltages and a
kilowatt or more of RF, it doesn't pay to skimp on parts of dubious merit.
Without intending to insult anyone, I thought the recent QST article on
scrapping out old microwave ovens for amplifier parts went too far.There is
a risk associated with old parts, such as transformers or filter capacitors
used in ways for which they were not designed. Ditto for cutting up old
pieces of galvanized metal (in any case, a definite no-no in an amplifier).
New, nicely finished aluminum sheet metal just isn't that expensive.
Sometimes, saving a few hundred dollars when your personal safety may be at
stake, and when the reliability may not be what you need just isn't worth
it. I know that hams have a long tradition of scavenging old TV sets, etc.
for parts, but there are a lot of landmines for beginners You're going to
be spending hundreds of hours building this amp, so don't waste your time on
inferior parts. In the long run you'll regret it. End of sermon.
73,
Jim W8ZR
> -----Original Message-----
> From: Amps [mailto:amps-bounces@contesting.com] On Behalf Of Jerry
> Sent: Friday, January 17, 2014 8:10 AM
> To: Amps@contesting.com
> Subject: [Amps] Building an Amp 101
>
> I have had a long desire to build my own linear HF or VHF amp. I believe
I
> have the electronic technical skills but after looking at some completed
> projects like those on WD7S website, I realized I don't have the skills or
> tools to do a nice job on the mechanical aspects of chassis / sub-chassis
> sheetmetal work. I guess I could cram it all into an unattractive box
> behind a reasonable looking front panel but is linear amp building mainly
> for those with good metal work capabilities? How does one break into
this
> with limited workbench space other than an electronic workbench?
>
> Jerry
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