[ARC5] "Curing Chirp in Command Transmitters"

[Dennis Monticelli]

I have found that a mild chirp seems to encourage hams to work my signal
(it piques their interest) and it can also assist in a pile-up because of
the differentiating sound.  However, it is bad practice in a regular
contest.  Some hams will lose CO time to "help" you by informing you of a
defect in your transceiver.  Obviously a bad chirp or excessive drift is
unacceptable and even more objectionable are clicks, which our command sets
are often guilty of.  Please everyone, check your signals for clicks and
add the appropriate wave shaping as necessary.

Regarding chirp:  There is a lot of misinformation out there.  Audible
chirp can only manifest from the expression of a relatively long time
constant on the order of 10's of milliseconds.  I can think of only two
sources for such a time constant in our command sets.  The obvious one is
the filter caps in the power supplies that will sag under load.  The other
is a small thermal mass that experiences a rapid temperature change, also
due to load changes.  We are talking really small masses like a resistive
contact (relay or inductor roller or connector) or perhaps the grid of a
tube.  The latter cause chirp in my rig when the finals went soft.  All the
other time constants in our sets are either too short or too long for
audible chirp.  The short time constants can cause inaudible FSK.  Mine
does that on the order of 2KHz and I'll bet most of the sets out there do
the same, however, no real harm done.  The very long time constants produce
good ol' fashioned drift, though I have found the command sets to be very
stable after a moderate warm-up.

Dennis AE6C

On Sun, Oct 5, 2014 at 11:20 AM, Mike Feher <n4fs at eozinc.com> wrote:

> Amazing how much BS a 67 year old article can create today, along with all
> of the unknown assumptions the commenters made from the minimal information
> provided in H&K. I will refrain from adding my own. 73 - Mike
>
> Mike B. Feher, N4FS
> 89 Arnold Blvd.
> Howell, NJ, 07731
> 732-886-5960
>
> -----Original Message-----
> From: ARC5 [mailto:arc5-bounces at mailman.qth.net] On Behalf Of Kenneth G.
> Gordon
> Sent: Sunday, October 05, 2014 1:49 PM
> To: WA5CAB--- via ARC5
> Subject: Re: [ARC5] "Curing Chirp in Command Transmitters"
>
> On 5 Oct 2014 at 1:19, WA5CAB--- via ARC5 wrote:
>
> > My thoughts are that the filament voltage in a BC-459 is 24-28 VDC. As
> > his isn't, there is no telling what other probably unnecessary mods
> > had been done to the transmitter. As has been demonstrated numerous
> > times, Command Sets (and many other military sets) work quite well in
> > the unmodified state when operated as designed. The H&K is worthless
> > as he gives no information about what else had been done to the
> transmitter to screw it up. Ignore it.
>
> Absolutely.
>
> Ken W7EKB
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