The Ham Radio technology of today takes us way beyond just making contacts or endlessly yelling into the Microphone "CQ POTA". It has become evaluative! We lust to know how our signal sounds at the other end of the circuit and those on the other end lust to tell us something is not right!
A young BB ~ Now > 80
(I'll do anything to get you to read the Blog.)
I smile when I hear signal reports: "well, you are only about a 5X7 and I can hear every word, but you are not strong!" The report somehow leaves you with an expectation that unless you are 20dB/S9 then it is not a good contact.
Last night I had the new 40M Hybrid Wireless Set on and just listening to various station, most of which were about 500 to 1000 miles away. I ran across that group that uses USB on 40M, and I switched over to USB and suddenly realized I never tried the new rig on USB.
The net control then asked would anyone like to check in. The control station was in Colorado Springs, and this would be a good test of my 20 Watts on USB.
I gave a call, and he came right back to me. In my return I gave my name, QTH, power level and that it was a new homebrew rig.
The next over the control station says you sound good BUT you are off frequency and a bit high. Give me some chatter and I will tell you exactly. I comply and he says I am using my GPS locked frequency standard for measurement and you are less than 50 Hz high. I also got reports from net stations in New Mexico and Nebraska who commented that the rig sounded very good but no mention of being less than 5o Hz high.
So, a couple of Points to Ponder (PTP). I can tell a station being off frequency at the 200 Hz level but not down to less than 50Hz. At that value (<50Hz) does it matter. Well, I guess it does if you spent $8K on a rig and then that becomes the justification for the significant sum spent for ham gear.
The other point is the settings we chose to display. The step tuning range on the Nano/Si5351 was set to 100 Hz. Basically, it says that actual frequency between 0 and 49 Hz above the dial showing 7.227.000 MHz would register as 7.227.000 but if the actual frequency was slightly greater than 49 Hz then it would register as 7.227.100.
Thus, if I was less than 50 Hz high then my dial would still show 7.227.000.
A simple cure would be once you tune in a station is to switch over the step tuning rate to 10 Hz and fine tune by ear the signal at the other end. This would then get you to within less than 10 Hz of being high in frequency.
Of course, the other solution is a recalibration of the Si5351 to get it dead nuts on frequency. I have done that using my SDR tuned to WWV and with trial and error you can zero beat WWV on the SDR with the DUT (Device Under Test).
Now a bit of boring math as we look under the hood. For some very good technical reasons I set the Digital LO above the operating frequency which also causes sideband inversion. Thus, the digital BFO for a 9MHz Crystal Filter is set for 8.998500 MHz resulting in LSB.
Then, the Digital LO is set for the sum of 7.227 + 8.8895 = 16225500 Hz (16.2255 MHz). If I were 49 Hz high in frequency that would mean that the BFO generation was off by 49Hz as that is the only variable. The BFO is actually at 8998549 Hz. But since we are reading to 100 Hz increments the dial would read spot on frequency. Recalibrating the Si5351 would generate 8998500 versus 8998549 Hz.
Them that know can make things go.
73's
Pete N6QW