[Milsurplus] Just had to comment - chirp
howard holden
holden7471 at msn.com
Mon Aug 19 21:30:16 EDT 2024
The first rig I built for the BK 1929 AWA contest, around 1991, was a MOPA, a 37 tube in a Hartley self-excited oscillator driving a 10 amplifier. It was RELATIVELY clean, but there was a little chirp and some drift. Nowadays I use some push-pull self-excited, some Hartleys (they're the easiest to get going), some TNTs. For 80M I use a pair of UV202s parallel in a Hartley design from 1921 QST. On 40 I use a push-pull TNT with a pair of 10s, and on 20 I use a single 211 Hartley.
I believe MOST of the 50s Novice transmitters were of the MOPA type, oscillator ( plus maybe a buffer) and amplifier. Not sure how they view the AC-1 though, that uses a 6V6 oscillator driving the antenna system directly. The Philmore (at least the NT200) used a 6V6 oscillator and 6L6 amplifier. My Novice transmitter in 1961 was a Heath AT-1, 6AG7 driving a 6L6.
73, Howie WB2AWQ
________________________________________
From: milsurplus-bounces at mailman.qth.net <milsurplus-bounces at mailman.qth.net> on behalf of B. Smith via Milsurplus <milsurplus at mailman.qth.net>
Sent: Monday, August 19, 2024 6:02 PM
To: milsurplus at mailman.qth.net
Subject: Re: [Milsurplus] Just had to comment - chirp
The MOPA circuit is very popular during the AWA 1929 Bruce Kelly contest.
But I prefer a single tube Hartley as it is easier to "tame". Lots of chirps and other keying sounds can be heard during the contest. The type 10 tube is very popular. Its a roll your own - - you have to build something including winding coils which seems to be a dreaded task by most hams. See attached for one of my transmitters. Its pretty chirpy until adjusted just right and then sometimes has a little unique buzz to it.
K4CHE
https://www.antiquewireless.org/homepage/bruce-kelley-1929-qso-party/<https://www.antiquewireless.org/homepage/bruce-kelley-1929-qso-party/>
[cid:part1.HI0OotRn.mYCGnMct at comcast.net]
On 8/19/2024 8:12 PM, mstangelo--- via Milsurplus wrote:
How does one eliminate chirp in a master oscillator power amplifier, MOPA design? Lightly couple the crystal to the tube, regulate the voltage, or design a separate oscillator?
Thinking back I had issues with the Ameco AC-1 which was my first transmitter with a MOPA design.
Besides the Ameco or CONAR transmitter does anyone recall another MOPA transmitter used by Hams?
Mike N2MS
On 08/19/2024 7:13 PM EDT Ken Gordon <kgordon2006 at frontier.com><mailto:kgordon2006 at frontier.com> wrote:
Well, IMHO it depends very much on the AMOUNT of chirp. Sure, al little is fine, but a yoop
can make it hard to copy at speeds greater than 20 WPM.
Personally, I will make great efforts to remove as much chirp as possible...and I want NO
clicks.
Minimizing chirp isn't really all that difficult for most rigs....even for the Conar.
Ken W7EKB
On 19 Aug 2024 at 21:21, sbjohnston--- via Milsurplus wrote:
Clicks can take up a lot of bandwidth so it is understandable that
they would be of concern. Same with hum on the carrier. But chirp
or yoop takes up only a little extra bandwidth and I've never felt it
was too a big deal for routine contacts. Actually helps discern one
signal from another and gives character, right?
I'd love to have a time machine to go back and hear how the bands
sounded in the decades before I was a ham. I bet they were more
interesting than today.
The only Official Observer card I ever received was for operating "out
of band". I was on 40m CW with my crystal controlled HW-16 and he
was hearing me 455 or 910 kHz away from my actual frequency (I don't
recall which).
Even as a Novice I remember thinking that this seemed more likely a
receiver problem on his end than a transmitter issue at my station.
I was in QSO with another station at the time the OO report mentioned,
so clearly at least some of my energy was inside the band.
I set up my station to match my logged conditions of that date and
time and listened with my Knight R-100 shortwave receiver (my only
other piece of gear in those early days) for a spurious out of band
signal - nothing heard. It is not impossible that I had a spurious
emission that he heard, but it would be a remarkable coincidence that
it was 455 or 910 kHz from the main signal.
If he was having a receiver problem, I bet he wrote a lot of cards
that day for all those stations he was hearing out of the band.
Steve WD8DAS
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