04-03-2018, 06:09 PM
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
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
Doug VK4ADC @ QG62LG51
http://www.vk4adc.com
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If you have a comment or question, post it as it may trigger or answer the query in someone else's mind.
http://www.vk4adc.com
This Forum is only going to be as interesting as the posts it contains.
If you have a comment or question, post it as it may trigger or answer the query in someone else's mind.