EMRFD Message Archive 8011
Message Date From Subject 8011 2012-12-30 18:50:10 davidpnewkirk 70 years ago in amateur radio frequency control From a Stray on page 52 of January 1933 QST:
Not long ago W9DKD tuned up his transmitter on about 3560 kc. in the early part of the evening. Coming back three hours later, he let out a CQ and raised a chap who reported him on 3450 kc., although the transmitter hadn't been touched in the meantime. A clamor from the back yard attracted attention to the antenna, and there, upon investigation, were some fifty blackbirds roosting on the sky-wire. After shooing off the birds W9DKD went back to the set and the frequency was back in the band again!
Bird loading notwithstanding, just such an LC-oscillator-only transmitter--the little breadboard single-201A TNT ("tuned, not tuned") rig visitors passed in its display case in walking down ARRL HQ's main hallway--gave us the bright idea of putting together a "spectral purity then and now" cover pic for QST's 75th anniversary in 1991. We knew it still worked, as I had already made a few contacts with it in a recent Antique Wireless Association contest, so we duly moved it to ARRL Lab's RF screen room and powered it up into a lightly coupled 50-ohm load, and prepared to chuckle as we put the spectrum analyzer into play.
Our big idea fizzled then and there. Although the frequency stability of a 1930s "self-excited oscillator" rig might well have been for the birds, an LC oscillator's tuned circuit makes a good filter. Our 201A TNT met FCC's 1991 requirements for spectral purity.
Yes, Virginia, not only is there a Santa Claus, but once upon a time radio amateurs actually "tuned the band"--even tuned _outside_ the band--for calls and replies.
amateur radio W9VES
8013 2012-12-31 06:54:00 KK7B Re: 70 years ago in amateur radio frequency control Hi Dave,
The real need for baking about half of those blackbirds (4 and 20 according to the lore) into a Pi-Network comes when you use that oscillator to drive an efficient 2nd stage.