El 29/09/17 a las 11:10, Jerry Gaffke via Groups.Io escribi¨®:
The 41m broadcast stations are usually accurate enough, and usually on even 5khz increments.
Hi,
I have used Broadcasting signals in the 41m band for fast calibration since a few years ago, they prove to be almost within a few Hz (<5 Hz) of the stated frequency when you test it against WWV on 2.5, 5 or 10Mhz. (Just use Big ones)
My favorite is Radio Catholic Mondiale on 7.315 in the afternoon - night period (at least in the Carribean/Americas) they are zero beat with almost 0Hz error as per my measures against WWV in 2.5/5/10 Mhz.
My method:
Fldigi feed with the audio of the SSB RX (an auxiliary receiver, I use my veteran FT-757-GX ), I place the dial as I get the carrier at 1khz on the audio spectrum for example:
WWV in 10.000000 Mhz
If LSB tune to 10.001000 Mhz
if USB tune to? 9.999000 Mhz
Then use your VFO to generate 10.000000 Mhz (use it as a signal generator not as a receiver) and feed a sample of RF to the receiver "et viola" you will find a carrier near (or not) the carrier of the WWV...
Tune your hardware/software settings in a way that your 10.0000 Mhz test signal get superimposed in the WWV carrier (use waterfall zoom to get more accuracy)
Needless to say that you must make this calibration test with both receivers warmed up for at least 30 min before the test to allow settling of the thermal drift on both. This is the way a calibrate the aging XTL oscillators and freq accuracy for some old/ancient ham gears when repairing. [By checking the soundcard accuracy and then testing other freqs against that over the auxiliary/test receiver]
Please note that the audio card has it's own XTAL and may have a error, so 1.0khz in your waterfall may be off by a few hz (I had a old PCI audio card that was almost a 300 Hz off, my Desktop PC has +50 Hz or so and my Lenovo Laptop has -20 Hz or so)
So the best results are using a auxiliary receiver to receive a very accurate signal (WWV) and no matter where in the waterfall this signal is, if you match that signal for the same generated freq you will be right on spot, and no matter what is the soundcard xtal/PC error)
But for ham radio purposes just beating a broadcasting by ear will put you withing 100Hz or so of the target freq, even 50 Hz or so for the trained ear... ;-)
73 CO7WT Pavel.
