[Amps] Old Tubes and IM numbers

[Roger (K8RI)]

In "the old days" we used to build amps out of most anything available, 
but back then tubes were cheap! So were my wages.  Big tubes were 
expensive back then compared to the average wage.

Rigs were simple AM & CW with a smattering of SSB in 61.
Rigs have become very sophisticated, but Top end rigs now are not as 
expensive as the simple  top end rigs back then.  Today's  lesser rigs, 
which are still complex, are far cheaper, and do more than the old rigs.

Back then, the bands were not crowded and no one worried about IM 
numbers.  Splatter and key clicks were the main items to be avoided.

Then came the sweep tube craze and we'd just stack up the tubes.  At one 
time I had a GLA1000B IIRC.  I wonder what the IM numbers were for that.

The mention of the metal 6AG7s used in an amp brought back memories.  I 
never had one, but I think a couple of the hams in the Gratiot County 
club did.  I remember talk about how much power they were getting with a 
bunch of them, upside down in a bucket of water.  Then I think it was 
the 1625 mod where you cut a chunk out of the base and turned them into 
a triode.  I don't remember that mod well, but there were several here 
in Midland when we lived here the first time. One had six 1625s in it. 
4CX250Bs were plentiful, cheap, and still in the vacuum packed military 
can.

There were sideband adapters for AM rigs, and low power SSB generators 
for the high gain amps of the day.  Few even had scopes and a few more 
might listen to their own signal.  The only protection the receivers had 
was the lowly NE-51 across the input. One thing most receivers and 
transmitters had in common was they were big, heavy, and hot. 
http://www.rogerhalstead.com/ham_files/boat1.htm  I think the photo was 
from the mid 70s .  It was while Ten Tech was selling the Omni D

IIRC that room was 13 X 21 feet.  After an hour, I'd need to open the 
door and let the heat out into the basement.  That is about the same 
time I had the 600 watt amp on 144 into a pair of 14L KLMs.

As I've often said, those old top end rigs put out a clean signal that 
today's SS rigs are just getting around to and that's in the top end rigs.

73

Roger (K8RI)

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