[TenTec] Some Observations on Orion Stability/Calibration

[George, W5YR]

I'm not sure that it buys much, Mark,unless there is a problem with the rig.
But, it is sorta like a fine car and its speedometer: you really expect it
to read "right on the money."

My Icom PRO2 usually starts off within 5 Hz of WWV, as measured by observing
the 1000 Hz tone obtained by tuning the rig to 10,001.000 LSB on the dial
and looking at the 1000 Hz trace on DigiPan. Within 5 minutes usually, the
delta is down to between 1 and 3 Hz and remains there indefinitely. The
shack stays around 74 deg in the summer aided by a small air conditioner.

 I believe that the PRO2 and its predecessor use the same TCXO spec'ed at a
max of +/- 0.5 ppm. So any dial calibration delta under 5 Hz at 10 MHz is
beating the spec quite a bit.

I find the DigiPan technique for measuring dial frequency relative to WWV's
carrier very useful. You first tune in WWV in AM and set the cursor on one
of the audio sidebands and let DP measure the tone frequency. If the tone
should be 500 Hz and you read 498.4 Hz, then your soundcard has a static
error of 1.6 Hz which has to be factored into the next step. Note that this
delta is independent of your radio dial calibration. Of several soundcards I
have checked, none has been in error. Many programs provide for compensating
soundcard frequency errors.

Next tune in WWV in LSB at one kHz above the carrier frequency to produce a
nominal 1000 Hz tone.With the cursor over the track of that tone signal, DP
will read out to the nearest 0.1 Hz the actual tone frequency it perceives.
This number, +/- the soundcard delta factor, should be 1000.0. Any
difference between the actual reading and 1000.0 is due to dial calibration
error of the radio. DP is quite accurate in this frequency determination as
it measures the frequency within the 31.25 Hz  DSP bandpass filter used in
the PSK31 operation.

The PRO provides a convenient fine-frequency adjustment via a recessed
trimmer on the side of the cabinet. Although it is very touchy, it is
possible to bring the radio into exact calibration.

I have used this method for checking dial calibration for several years now
with a variety of receivers and find that it provides the most accurate and
consistent results available in the usual ham shack without special
equipment.

Although described in terms of my PRO2 operation, the method should work
equally well with the ORION or any receiver capable of receiving WWV.

73/72, George
Amateur Radio W5YR -  the Yellow Rose of Texas
Fairview, TX 30 mi NE of Dallas in Collin county EM13QE
"In the 57th year and it just keeps getting better!"
<mailto:w5yr at att.net>





----- Original Message -----
From: "Mark Erbaugh" <mark at microenh.com>
To: <tentec at contesting.com>
Sent: Wednesday, June 04, 2003 7:42 AM
Subject: Re: [TenTec] Some Observations on Orion Stability/Calibration


> What are the advantages of using an external frequency reference, such as
> from a GPS receiver with a single RX-340? How important is that kind of
> accuracy for HF reception?
>
> Also, how far off in frequency was the RX340 in normal operation vs with
the
> external reference?
>
> 73,
> Mark
>
>
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