[Amps] Building an Amp 101

Sat Jan 18 15:16:50 EST 2014

> -----Original Message-----
> From: N1BUG [mailto:paul at n1bug.com]
> Sent: Friday, January 17, 2014 10:44
> To: Jerry; 'Amps'
> Subject: Re: [Amps] Building an Amp 101
>
> Jerry,
>
> It often seems at though the only builders here are those who turn out works
> of art.

I've seen many well engineered and laid out amps on here, but being a 
perfectionist, Ive seen none that I'd call works of art. Unpainted with 
stick on labels along with awkward enclosure shapes all say unfinished 
to me.

There is actually a preferred length, width, and height ratio that can 
easily be maintained.

My perfectionism is probably why so few projects actually ever get 
finished and my scrap bin is filled to over flowing.  That and whether 
Plastic, wood, Aluminum, or steel, I have this " That's large enough I 
might be able to use it some day" built into me so I have a hughe pile, 
or I should say oiles of materials consisting of small bits and pieces. 
  Just ask any of the local hams or my neighbor who offers to help me 
clean up the shop every time he comes over.<:-))

That's the same neighbor I showed the 25 G project to and explained my 
plans to. When I came back out after a snack, I found that he and his 
wife had dug the hole for the dirt base.  Photos of the base follow.
http://www.rogerhalstead.com/ham_files/Dirt_Base.htm

>But there are some who build functional amplifiers that aren't
> pretty. My main reason for amp building is  insatiable desire to push the
> limits of propagation and DXing on some of the more challenging bands. I
> would love to have something that looks great too, but that's not in the
> cards.

As has been mentioned, you probably have most of the tools including the 
most important; two hands and a mind with the desire to build.
If you are willing to take the time to learn to use the hand tools 
properly, you can build as good a looking amp as the commercial.  Copy 
the physical layout of some of the amps with better reputations.  You 
can design the circuit if you want to, but why "reinvent the wheel" so 
to speak when it comes to the cabinet and physical layout.  BTW you can 
purchase the chemicals to alodyne (put that gold color and protective 
layer) on the Aluminum chassis for a reasonable price from Aircraft Spruce.	

Today's amps are all of a much more basic physical design and 
construction than those of days gone by.  Look at the cabinets. They are 
more a simple, 3 sided piece of flat stock that you could make using 
simple tools such as a vise, angle iron, C-clamps, a file, emery cloth, 
a drill, and wood block and hammer.  A good quality paint and you have a 
cover to match the best of today's amps.  Admittedly, few of us can use 
a durable powder coat although small pieces are easy enough to do in the 
oven "over a pan".  The pan is to maintain domestic tranquility and the 
division of your assets.

BTW use a harder alloy than the typical soft aluminum we usually see in 
home brew.  It's stronger and easier to work with.  I use 6061-T6 but 
there are better and cheaper alloys available.  Ask the supplier for 
suggestions. They are often quite willing to help pick the proper 
material..

Peter G3RZP has an excellent post on what's handy and how to do good 
work with simple tools.

I have neither the money to buy commercial amplifiers nor to outfit a
> shop to produce works of art nor to hire out the metal work. I have seen
> others make works or art using simple tools.

> I either don't have the skills,
> the patience, or I start with less than ideal raw materials to cut cost.
> All of my amps were low budget projects. My early amplifiers were built
> using only simple hand tools. In recent years I have acquired a drill press
> and table saw (which I use to cut aluminum). I don't have space for a work
> shop. For the messy parts of a project I often work outdoors on a folding
> work bench - even if it happens to be winter with snow on the ground. Over
> the years I have built (for myself and others) amplifiers for all bands
> between 1.8 and 432 MHz with power ranges from a few hundred watts to 1500
> watts out. None of them were pretty.
>

If you have the patience to build those with simple hand tools, you have 
the patience to learn how to use those tools to their limits. It's 
probable taking the time to learn, but not seeing physical results.  We 
often run into that building aircraft.  The builder reaches a stage 
where they work for hours (maybe over a hundred hours) with little 
physical results to show for it.  The reinforcements on the firewall for 
the engine mounts (more properly, engine mount attach point 
reinforcements).  These required 96 individual layups of fiberglass 
cloth and Vinyl ester resin.  Page 10 on
  http://www.rogerhalstead.com/G3_files/GIII_Diary.htm

This thread contains many instructions on how to get good results with 
simple tools. Again I refer to one of the posts by Peter G3RZP, but 
there are several others and I apologize for not remembering who made 
them.  There are also some that I'd not recommend, but they are trying 
and that's what counts. One that comes to mind was cutting metal sheet 
by scribing it, clamping the sheet, breaking it along the scribe line 
and then finishing the edge using a file and emery cloth.  This can 
produce an edge as good as any commercial cut. It just takes time, but 
there are some very good construction practices in this thread.  There 
is a learning curve and it'd be good to sacrifice a few pieces of scrap 
for practice.  You will be amazed at how well you can do with a bit of 
properly directed practice.

> It's a matter of what you want. If you want to build a functional amplifier
> you can certainly do that without the beauty. If you want something that
> looks professional then you must explore options to achieve it.

Agreed, although it takes little extra time to get good results once you 
know how.

Mark the comments in this thread on metal working with hand tools.  They 
are well worth rereading and learning. I've learned several new 
techniques. The larger tools are nice to use and make chassis building 
faster and easier, but they are not necessary and the time required to 
learn how to get the most out of hand tools is not great.

Good Luck!

73

Roger (K8RI)

>
> Paul N1BUG
>
>
> On 01/17/2014 10:10 AM, Jerry wrote:
>> 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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