[Boatanchors] AM rig

[Bob W5UQ]

This is long so if you don't like long emails, don't read it... but if 
you like stories about "the old days" 1950's and 60's, (& early 
70's)then read on:

In the old days, we got the old military amplifiers.  I can't remember 
the model numbers... but would recognize them.  (BC455 was the 
receiver....and wasn't the transmitter something like BC696 or 
similar?)  My mind can't seem to find the numbers tonight... Oh well... ;-)

Anyway, they had two 1625's in them and we either use the 1625(cutting 
into the side of the bakelite base and modifying the tube from 12 volt 
to 6 volt filaments) or just modified them to take the 807's.  (required 
changing out the tube sockets from 7 pin to 5 pin.) (the driver was a 
1626 tube I believe........ funny,  I remember that and can't remember 
the model numbers :-[ )

We built outboard modulators and power supplies.  The TOTAL size of 
these rigs were smaller than the Viking II I had.  At least it seems 
like they were.... Okay.. I'll admit that it was so long ago that I 
don't really remember... :-)

Then we started converting the 1625 amps to SSB linear amps and the 
power supplies GOT bigger until we learned to make them better.   I 
remember going from  choke input filtering and capacitor on output of DC 
line.  I also remember having to put much larger capacitance in the 
power supplies to keep the B+ from varying with the SSB modulation 
causing the amplifier to AM (audio distortion of signal).  It worked but 
the power supply seemed to HUM a lot more... HOWEVER,  I was impressed 
and thought it sounded "neat" ........until.............one day, they 
started huuummmmmming VERY loudly.

I found out that if I turned the supply off, then turned it back on 
before the caps bled off, then turned it off again and back on before 
they bled off again, then modulated the rig with SSB signal,   that the 
build up across the caps would be so big that they would hum LOUDER, of 
course that was cooler yet.   Then one day.... one day...... when I was 
going for a more cool sounding rig,  one of the caps built up way toooo 
much and shorted out, going off like a shotgun, scaring the #### out of 
me and spraying oil and aluminum foil everywhere.  The cap was 2 1/2 to 
3 inches in diameter and dented the top of my case.  But it only had to 
happen once for me to figure out how to keep it from happening again... 
that is "after I changed my pants"...... :-[ 
We put bleeder resistors across the caps to bleed off the "build up" 
_and_ didn't turn them off and on, off and on... etc.... We gave the 
caps time to bleed off. 

Okay... alright... I was a young squirt then.... :-D .   I still say it 
really sounded NEAT. 

Anyway, we used them for 100 watts or so output amplifiers and AM 
modulated them...... or used them for CW rigs, then later for SSB linear 
amps.  Hence power supply changes had to be figured out.... we learned 
the hard way a lot of the times... HI.

Pushed them with our lower power rigs... like Heathkit AT-1 or Viking 
Adventurer or similar rigs.  Then later, we used Central Electronics 
10A, 20A or 20B SSB exciter rigs.  My 10A worked great for SSB pushing 
the 1625's.  Worked a lot of SSB on the upper part of 75Meters... the 
FATHEAD NET was at 3995KHz and in those days, it was dangerous to work 
so close to the band edge... but we had fun and talked from midnight to 
sun up every night. 

Anyway, back to the main story.  The PI network coils and tuning caps 
were not anything much different to some of the rigs today. We changed 
out some of the other caps due to higher voltage ratings needed.  
Changed some of the resistors out, changed biasing, etc.  But they worked.

I even used a Heathkit audio amplifier once to modulate my 1625's 
amplifier.  It was a 50 Watt amp and I used another output transformer, 
BACKWARDS, to match the 16 ohm output to around 5k to 10K ohms for 
modulating the 1625's.  It worked too, sounded pretty doggone good 
too...  It had "tone controls" that made a real difference to my sound.  
Got lots of comments about that.   Seems like I used a JT30 Astatic 
Microphone too.  Probably had RF on the mike and it bit my lip.... 
REMEMBER????  It happened to you too, RIGHT?  Also, remember having to 
flip several toggle switches to go from receive to transmit? 

I get the idea the this is what Doc wants to do,  "IS LEARN like we 
did"...  Man did we do it and boy did we learn.... for one thing, I can 
remember the white RF burns on my fingers and hands from touching the 
plates or output coils while transmitting....of course accidently...
Yep it hurt and I am lucky, but we LEARNED....
 
Anyone remember putting florescent lamps near the output coils to see 
them light up?  How about on the  top of a 1/4 wave vertical?  Or even 
at the voltage point on a dipole?  I got burned many times that way too. 

Doc wants to do those things .....I think.  Play around and experience 
the things we did when that's ALL we had...something called TUBES...  
with no idea what a transistor or solid state was...  I really miss 
those days... however, I'm having fun now too.  I'm a HAM.

Sorry to get so wordy...  hope some enjoyed it though... Bob... W5EUQ... 
now W5UQ...  sure having trouble getting used to that new call... after 
53 years using it. :-D





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