[AMRadio] would like to build a little homebrew project


Brett gazdzinski brett.gazdzinski at verizonbusiness.com
Mon Aug 6 10:42:01 EDT 2007


Look at fests and ebay for handbooks from the
early 50's to the early 70's, both Bill Orr and
arrl.  I like the red and yellow Bill Orr handbooks,
forget what year they were exactly.

You don't need to get a lot of them, say one every
4 years or so, as they did not change a lot from
year to year.

Then you take parts of designs and put them together,
no need or reason to build something just like any book says,
you just need a basic circuit and experiment from there.

Like the 3x4D32 rig, there IS no design anywhere for that rig,
but its just your standard beam power tube rig.
Take a 4D32 tube and multiply everything by 3, 3x screen current,
3x grid drive, 3x power input, etc.
For the tank circuit I just wound copper tubing then shorted turns
till I had a good Q, good plate current dip, good efficiency, etc.

Then you think about the modulator....how much power do you need?
In the 3x3D32 rig, its about 300 watts...my rule of thumb is to have
at LEAST as much audio drive as power output (for a clean signal).

What gives 300+ watts of audio at 1000 to 1250 volts?
Why 811A's do nicely, zero bias to!

You can do the same thing when building receivers, mine have circuits
out of Bill Orr, ARRL, the detector came off some web page, some design
was taken from the old Scott SLRM I used to have, etc.

Everything gets broken down into little chunks:
RF only deck,
Bias supply,
Screen supply,
Metering and lights,
Protection circuits,
Keying circuits.

You can mix and match those to get what you want/like.
Adjustable bias? Variac? Grid leak resistor fixed or big pot?
Meter for voltage and current? Decouple grid leak bias from fixed
bias with a diode?

You can then build exactly what YOU want, complexity gives
more options, and maybe more safety, but gets bigger and more expensive.

It sure is FUN to homebrew!


Brett
N2DTS



  

> -----Original Message-----
> From: amradio-bounces at mailman.qth.net 
> [mailto:amradio-bounces at mailman.qth.net] On Behalf Of Jason Buchanan
> Sent: Thursday, August 02, 2007 9:58 AM
> To: Discussion of AM Radio in the Amateur Service
> Subject: Re: [AMRadio] would like to build a little homebrew project
> 
> 
> On Jul 31, 2007, at 9:11 PM, crawfish wrote:
> 
> > I just received a copy of the 12th Radio handbook(1949). After  
> > WWII, 160m
> > was given to LORAN for the most part, and you had to go to the pre- 
> > war Radio
> > Handbooks to find amps for 160m.
> 
> I may scrounge around for some of those books - do you know what  
> years might be good books to look for?  I probably won't find them  
> for sale so probably will have to borrow...  If you know what 
> year of  
> publication had good ones i'll try to find those years.
> 
> thanks a ton................
> 
> --
> 73 Jason N1SU
> http://n1su.com/
> 
> 
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