Early Zachary T- no Tx or Rx, VCO problem.

nomadradio said:

I'm accustomed to watching the tuning voltage on a 'scope, to see what the tuning voltage is on channel 1 and 40. For that radio, also seeing the transmit tuning voltage at each end also matters. If it's getting too close to zero, or too close to 5 Volts, tweaking the VCO coil to keep the max-to-min voltage range right beats setting it with a voltmeter on channel 20.

Then again, you can check the max/min extremes with a meter, too. Way cool you got it under control. I tell customers it's like the cruise control on your daily driver, but for frequency, not speed.

73

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That's a great point, I didn't think of that. On a Cobra 29, L22 is the balance coil for ch1 and ch40, and it comes off of the 1/2 Ref Osc pin 10 of the PLL. ON this 858 PLL it would be pin 8, but it's not used in this radio. I assume that's why it wasn't in the synthesizer alignment section, that would make sense though. Just checking the voltages with my scope, ch 1 = 2.26v, ch 19 = 2.93v and ch 40 = 3.69v after just powering on the radio. The voltages were basically the same in transmit. That's is one nice thing about these digital scopes today, being able to see the voltages plus the signal is very nice. Also another plus is, when I checked Pin 11 per your recommendation, the scope showed the frequency around 1.4Mhz, and my old 1900a Fluke freq. counter wouldn't register the frequency at all. Just another reason to use a scope.