[Lowfer] ARGO

Mon Dec 31 16:13:04 EST 2012

John,

I'm sure you are absolutely correct. The method I described is just a quick
and dirty method, not needing a frequency counter, known calibrated audio
tone source, or any other equipment whatsoever. It has worked well enough
for me for several years now that I know when (after I allow my receiver to
warm up) I tune to a certain frequency from 10-500 kHz to receive a QRSS or
WSPR signal I'm never more than half a Hz off. Looking at MP scrolling
across now.... it looks like, now that my receiver has warmed up (and
assuming MP is right on frequency), that I am one tenth of one Hz off in my
calibration. I can't remember when I last did an Argo calibration on this
receiver+upconverter....probably early October, when the listening season
started.

I rarely tune above 500 kHz, so I don't give much thought to frequency
calibration errors at HF or above.

73, Doug KB4OER

On Mon, Dec 31, 2012 at 3:50 PM, John Andrews <w1tag at charter.net> wrote:

> Doug,
>
> Just to split a couple of hairs:
>
> You need a known audio frequency to calibrate the sound card sampling
> rate. An audio tone from a receiver that depends on a converter L.O., and
> one or more conversion oscillators (and maybe the BFO) doesn't qualify.
>
> The combination of the converter and receiver likely has a frequency
> offset that varies with receiver tuning. Calibration of that offset at 60
> kHz may be in error at other frequencies.
>
> The above applies to fussy situations like WOLF and slow PSK modes, where
> sampling rate must be nailed to keep framing consistent, and receiver
> offsets nulled out.  For QRSS use, you'll likely see cal errors between
> bands, and they MAY be small enough to ignore.
>
> John, W1TAG
>
>
>
> On Dec 31, 2012, at 2:43 PM, "Douglas D. Williams" <kb4oer at gmail.com>
> wrote:
>
> > Hi Mike. My method for calibrating ARGO is very simple, and does not
> > require any extra equipment. As someone else pointed out, first you have
> to
> > know the BFO sidetone of your receiver. Most modern receivers allow you
> to
> > vary this sidetone through some sort of menu. I happen to like to hear a
> > 700Hz tone when listening to CW, so that's what I keep mine at. I tune to
> > 60 kHz WWBV with the receiver set to CW mode (reverse CW for Icom
> > receivers), and allow the receiver to warm up for an hour. If you are
> using
> > an upconverter, then simply tune to the converter's LO frequency + 60
> kHz,
> > so in my case that would be 3.060 MHz. At this point I would set Argo to
> > some relatively fast QRSS speed such as QRSS10, and center 700Hz on the
> > right side scale. You may have to reduce the receiver's audio gain and
> > lower Argo's sensitivity slider quite a bit because WWVB is very strong
> in
> > the lower 48. If your total system calibration is within 20Hz or so of
> > being correct, you should see a bold, thick line start scrolling across
> the
> > screen, with thinner lines (sidebands, I guess) above and below it. What
> > you want to do is go into Argo's setup menu and choose Calibration. If
> you
> > see the bold line at, say 705Hz then you would enter 700 (if that's the
> > sidetone you are using) in the Measured frequency box and 705 in the
> > Displayed frequency box. That should get you within one Hz of being dead
> > on. You can dial it in even more at the slower QRSS speeds by using
> decimal
> > places in the numbers you put in the Displayed frequency box.
> >
> > What you are doing is calibrating the total receive system (receiver,
> > upconverter, computer sound card) to be correct on the Argo screen. Of
> > course, the job is easier if the oscillators in your receiver and
> > upconverter are close to the frequency they should be. If you are using
> an
> > upconverter with one of those little 4 MHz crystals about the size of a
> > child's fingernail, good luck. ;-)
> >
> > At this point, many people go a step further because they like to have
> > Argo's frequency scale (the one on the right) display the actual
> frequency
> > (in Hz) that they have the receiver tuned to. This can be accomplished by
> > using the Offset box in the Calibration window and typing in the
> frequency
> > you have the receiver tuned to, minus your BFO frequency, if I remember
> > correctly. I'm usually too lazy to do this, so my screen captures tend to
> > just have the BFO sidetone frequency.
> >
> > Well, that was a lot of typing to describe something that generally only
> > takes about five minutes to do, once the receiver is warmed up. ;-)
> >
> > 73, Doug KB4OER
> >
> > On Mon, Dec 31, 2012 at 1:58 PM, Mike Sanders <k0az at centurytel.net>
> wrote:
> >
> >> Stan, Charlie and Mark, Thanks very much for all your input.
> >> I am going to continue to follow through with this until I get it.
> >> Your help may make the difference.
> >> I am also using a converter and it is introducing minus 302 hz
> >> of aggravation from the LO. My first lowfer target is WMS only
> >> about 170 miles South of me.
> >> I have not looked through all your email info yet but will as well
> >> as checking out John's write up on ARGO set up.
> >> Thanks again and you will know when I get a good capture.  73
> >>
> >> Happy New Year
> >> Mike Sanders
> >>      K0AZ
> >>
> >>
> >>
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