[TenTec] Precision in Frequency displays

[Eric F. Richards]

I'd like to throw my opinion in on this as well, but first a little
background on me:  I am a ham, but the time I spend in HF is spent
listening.  I primarily listen to utility/military stations, but I
do listen to international broadcasters as well.

Up until recently, my "best" receiver was an ICOM R-8500.  Unlike many
radios, it isn't all that complex, but gets the fundamentals right --
things like having a bulletproof front end, for example.

One of the other things ICOM got right with it was the accurate calibration
of the PLL oscillator.  While it only has 10 Hz precision, checking against
WWV at 15 MHz showed no -- NO -- difference in tone when listening in AM,
USB or LSB.  This is important with the '8500, because its AM filters are
too wide and have a poor shape factor.

...and I *can* tell the difference, and when the tuning is off, even by
only a couple Hz, it gives me a headache in a hurry.  (And I'm not young,
unless you consider 40 young...)

Naturally, over time the 8500 has drifted off.  However, I don't expect
that to be a problem with my new receiver, the T-T RX-340, since I also
sprung for a surplus HP Z3801A GPS frequency standard.

While the RX-340 is not likely to be used predominantly as a int'l
broadcast receiver, it's good to have a very stable, traceable frequency
standard on it, making SSB reception a pleasure.  (Oh, yes, for the
transmitters that aren't on-the-money, the 1 Hz tuning steps help, too.
But that's not everything:  My ICOM R-75 also has 1 Hz tuning steps:
great precision, very poor accuracy.)

Just $0.02 from the peanut gallery,

73 de KB0YDN, Eric

At 12:57 AM 3/5/2003 +0000, you wrote:
>Stuart,
>
>It's not the acuracy here by displaying to a 1 hertz value that's real
>important.  It's the ability to adjust the frequency in 1 hertz increments.
>I have a mode I call SAM for sync AM that is not really sync AM.  What it is
>a LSB with a very wide filter centered on the carrier.  You can listen to an
>AM station and zero beat the BFO to the carrier.  This requires the BFO to
>be precisely zero beat with the AM carrier in order to be effective.  So, in
>this case, the ability to adjust the BFO in 1 hertz increments is important.
>I don't care if the display is really off 20 hertz, but it is nice to be
>able to do a precision zero beat for this mode.
>
>Carl Moreschi N4PY
>Franklinton, NC
>----- Original Message -----
>From: "Stuart Rohre" <rohre at arlut.utexas.edu>
>To: <tentec at contesting.com>
>Sent: Tuesday, March 04, 2003 11:58 PM
>Subject: [TenTec] Precision in Frequency displays
>
>
> > Let's get real:   1,000,000 Hz (a MHz).
> > 1 per cent is 0.01 of that, or 10kHz
> > 0.1 per cent is 0.001 of that or 1,000 Hz
> > 0.01 per cent is 0.0001 of 1 MHz or 100 Hz
> > And 0.001 per cent is the debated 10 Hz!
> >
> > Now most of the components in ANY radio are not held to tolerances of
>0.001
> > per cent!  Young ears might resolve a 10 Hz difference in tone, but
>average
> > ears probably cannot zero beat to even that difference.  Give the
>frequency
> > display designers a break, what do you need less than 10 Hz for?   IF you
> > are off a net by that much, someone will comment on your tone, and you
>will
> > talk yourself on.
> >
> > For those who need the most stable frequency source; an optional TCXO is
> > available for the Argo V.
> > 73, Stuart K5KVH
> >
> >
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> > TenTec at contesting.com
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--
Eric F. Richards
efricha at dimensional.com
"The weird part is that I can feel productive even when I'm doomed."
  - Dilbert