curing chirp ??
 

The anonymous homebrew xmtr I picked up at the AWA meet last
spring has finally make its first QSO, heard 589 in Texas by KE5HQ on 40
CW, but he reports what I sort of knew anyway...the rig has a chirp. The
oscillator is an electron coupled 12BY7, crystal controlled. What are
the cures for chirp ?? Slightly detune the buffer ?? add caps to the
power supply. Trying the easiest things first, how should I proceed ??

curing chirp ??
 

William Mutch wrote:
The anonymous homebrew xmtr I picked up at the AWA meet last
spring has finally make its first QSO, heard 589 in Texas by KE5HQ on 40
CW, but he reports what I sort of knew anyway...the rig has a chirp. The
oscillator is an electron coupled 12BY7, crystal controlled. What are
the cures for chirp ?? Slightly detune the buffer ?? add caps to the
power supply. Trying the easiest things first, how should I proceed ??

The easiest first check is to try another crystal.

-Bill

curing chirp ??
 

Is it a chirp ( as in frequency change) or a click ( as in transients caused
by keying )?

Does the power supply sag at all under load? Regulating the screen on
the 12BYZ may help considerbly.





"William Mutch" wrote in message
ell.edu...

The anonymous homebrew xmtr I picked up at the AWA meet last
spring has finally make its first QSO, heard 589 in Texas by KE5HQ on 40
CW, but he reports what I sort of knew anyway...the rig has a chirp. The
oscillator is an electron coupled 12BY7, crystal controlled. What are
the cures for chirp ?? Slightly detune the buffer ?? add caps to the
power supply. Trying the easiest things first, how should I proceed ??

curing chirp ??
 

In message . edu,
William Mutch writes

The anonymous homebrew xmtr I picked up at the AWA meet last
spring has finally make its first QSO, heard 589 in Texas by KE5HQ on 40
CW, but he reports what I sort of knew anyway...the rig has a chirp. The
oscillator is an electron coupled 12BY7, crystal controlled. What are
the cures for chirp ?? Slightly detune the buffer ?? add caps to the
power supply. Trying the easiest things first, how should I proceed ??

My DX100 had a bad chirp. Cured by cleaning the key contacts with fine
emery paper.

Mike G3IJE
--
M.J.Powell

curing chirp ??
 

In article ,
says...

Is it a chirp ( as in frequency change) or a click ( as in transients caused
by keying )?

chirp

Does the power supply sag at all under load? Regulating the screen on
the 12BYZ may help considerbly.

It's already regulared with a VR150




"William Mutch" wrote in message
ell.edu...

The anonymous homebrew xmtr I picked up at the AWA meet last
spring has finally make its first QSO, heard 589 in Texas by KE5HQ on 40
CW, but he reports what I sort of knew anyway...the rig has a chirp. The
oscillator is an electron coupled 12BY7, crystal controlled. What are
the cures for chirp ?? Slightly detune the buffer ?? add caps to the
power supply. Trying the easiest things first, how should I proceed ??

curing chirp ??
 

In article ,
says...
William Mutch wrote:
The anonymous homebrew xmtr I picked up at the AWA meet last
spring has finally make its first QSO, heard 589 in Texas by KE5HQ on 40
CW, but he reports what I sort of knew anyway...the rig has a chirp. The
oscillator is an electron coupled 12BY7, crystal controlled. What are
the cures for chirp ?? Slightly detune the buffer ?? add caps to the
power supply. Trying the easiest things first, how should I proceed ??

The easiest first check is to try another crystal.

This is the only xtal I have for 40 meters. I can (and will) try
it with others on 80 CW.

-Bill

curing chirp ??
 

Hate to tell you this, but with many classic few-tube transmitters you
get your choice: either chirp or clicking or chirp and click.

If you key the oscillator, you get chirp.

If you keep the oscillator running all the time and key the
driver/final, then you get clicks. Not to mention some backwave
(leakage of carrier when you are key-up, leakage is almost inevitable
in a tube oscillator where you running the oscillator at 10 or 20V
P-P.) Without enough buffering you also get chirps as the keying of the
later stages loads down the oscillator stage.

A 50's or 60's ARRL Handbook will have a chapter about the tradeoffs in
keying methods. Many 4 or 5-tube transmitters, despite all their
buffering and keying stages and VR tube, still have noticable
chirp/click and while you should certainly strive to understand the
issue, you will have some chirp with any simplistic TX. In terms of not
interfering with QSO's up and down the band, some chirp is preferable
to some click.

Tim.

curing chirp ??
 

The power amplifier, when keyed, causes the main HT supply volts to
change at a rate which depends on the size of the HT smoothing
capacitors. This change in HT volts also affects the DC supply to the
oscillator tube which causes the frequency to change in sympathy with
volts. Most tube oscillators change frequency with supply volts.

So stabilise the DC supply voltages to the xtl oscillator -
especially the screen-grid DC volts. It won't matter if the DC supply
volts are increased by 15 or 20 percent in the process.

Use a gas-filled voltage stabiliser tube if you can find and fit one.
They used to be available in voltages from 50, 75, 90 to 150 volts.

But a few transistors could do the job.

Adding caps to the power supply will merely slow down the chirp and
perhaps make it more noticeable.

If the DC supply to the oscillator is already stabilised then there
may be a small amount of RF feedback from buffer or power amplifier to
the oscillator. In which case you have a much more complicated
problem to solve.
----
Reg, G4FGQ

curing chirp ??
 

One more thing. If the crystal is driven heavily, it heats up and chirps.
Reducing the amount of feedback in the oscillator can help, but can be
tricky as well. No suggestions where to proceed without knowing the
circuit.
73, Steve K9DCI

"Bill" wrote in message
...
William Mutch wrote:
The anonymous homebrew xmtr I picked up at the AWA meet last
spring has finally make its first QSO, heard 589 in Texas by KE5HQ on 40
CW, but he reports what I sort of knew anyway...the rig has a chirp. The
oscillator is an electron coupled 12BY7, crystal controlled. What are
the cures for chirp ?? Slightly detune the buffer ?? add caps to the
power supply. Trying the easiest things first, how should I proceed ??

The easiest first check is to try another crystal.

-Bill

curing chirp ??
 

William Mutch wrote:

The anonymous homebrew xmtr I picked up at the AWA meet last
spring has finally make its first QSO, heard 589 in Texas by KE5HQ on 40
CW, but he reports what I sort of knew anyway...the rig has a chirp. The
oscillator is an electron coupled 12BY7, crystal controlled. What are
the cures for chirp ?? Slightly detune the buffer ?? add caps to the
power supply. Trying the easiest things first, how should I proceed ??

I always liked the sound of a chirpy signal. It never bothered me,
and when you hear one now you know there's a real ham behind the key!

Irv VE6BP
--
--------------------------------------
Diagnosed Type II Diabetes March 5 2001
Beating it with diet and exercise!
297/215/210 (to be revised lower)
58"/43"(!)/44" (already lower too!)
--------------------------------------
Visit my HomePage at http://members.shaw.ca/finkirv/index.html
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--------------------
Irv Finkleman,
Grampa/Ex-Navy/Old Fart/Ham Radio VE6BP
Calgary, Alberta, Canada