[Lowfer] ARGO

Mon Dec 31 16:20:10 EST 2012

Nope, gonna have to eat some crow. That's not MP I'm seeing, so I may be
off more than I think. :-)

Still looking for MP.

73, Doug KB4OER

On Mon, Dec 31, 2012 at 4:13 PM, Douglas D. Williams <kb4oer at gmail.com>wrote:

> 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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