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+--- Thread: FT817nd xtal osc pins...which are output? (/thread-525.html)
FT817nd xtal osc pins...which are output? - VK3LU - 04-03-2018
My ft817nd is a tad off frequency at 144mHz, at least 100Hz.
Now, that's not much on ssb but on WSPR it's a lot, half the bandwidth actually. Therefore I need to check the frequency of the 22.625 mHz osc in the little beast.
Does anyone know the pinout of the osc unit so that I can measure the freq.?
Thanks in anticipation
Nev
RE: FT817nd xtal osc pins...which are output? - VK4RW - 04-03-2018
Nev
Is this helpful? http://www.ka7oei.com/ref_unit.gif
Looks like the output is on pin 2, if I am looking at it correctly.
Cheers
Ron
RE: FT817nd xtal osc pins...which are output? - VK4ADC - 04-03-2018
Nev
Be aware that any device you connect to the test point (ie osc output) is likely to load the oscillator and alter the frequency.
A second point : the device you want to measure with (eg freq counter) must be extremely accurate at 22MHz... Like less than 1Hz in error given the 22MHz LO is probably multiplied by 6 to serve as the injection at 2M. Take that 100Hz error you have noted, divide it by 6 = 16.6Hz of actual error at the crystal frequency.
You are actually better off measuring a precise 2M frequency (eg GPS locked beacon) so that the dial frequency is correct for the emission mode and measuring the resulting tone frequency using a sound card plus DigiPan or Spectran software eg gives (for example) a 600 Hz tone - and then adjusting the LO frequency so that the correct audio tone frequency is generated.
For instance: the 432MHz VK4RBB beacon up here is zero beat at 432.440000 (USB) so the radio dial is set for 432.439400 (on USB) to provide a 600 Hz tone and that is measured via the software. If you want easier adjustment, slip the dial down to 432.438400 so that the tone generated is at 1600 Hz.
Hope that helps
Doug
RE: FT817nd xtal osc pins...which are output? - VK3LU - 04-03-2018
Ron,
Thanks for the info. That is just what I was looking for.
Doug,
Thanks for that. Unfortunately there is not a beacon within a bull's roar of me, let alone a GPS locked one.
I will have to trust my HP counter and use the trial and error method.
Cheers all
Nev
Edit... Of course I could get an ebay TCXO-9 and see how that goes.
RE: FT817nd xtal osc pins...which are output? - VK3LU - 19-03-2018
Doug,
I have found that I can hear the Mt. Anakie 2m beacon, faint but producing a solid trace on Spectran. Why I can hear it is a puzzle, given the distance to it and the terrain, but I am not going to complain!
I also discovered it is gps locked, so I checked the ft817 and found it a bit high so duly tweaked the reference osc.
Will have to wait until I get some 2m spots on WSPR to check the adjustment.
73
Nev
RE: FT817nd xtal osc pins...which are output? - VK4ADC - 19-03-2018
That's great to hear. The known frequency of the GPS locked beacons makes it far more accurate to achieve setup to frequency than the outcome of reading the LO injection with an long-ago calibrated frequency counter. I will be interested to hear how far off it actually is, keeping in mind that it could still drift over time.
It doesn't matter if it isn't overly strong provided you get a clear trace with Digipan or Spectran to make your measurements.