[R-390] Capehart made R-390A Serial #312

[Jordan Arndt]

If you're going to monitor the osc. output for harmonics and level like 
that, a spectrum analyzer is likely the best way to go...

73...Jordan VE6ZT

----- Original Message ----- 
From: "David Wise" <d44617665 at hotmail.com>
To: "Jacques Fortin" <jacques.f at videotron.ca>
Cc: <r-390 at mailman.qth.net>
Sent: Thursday, April 10, 2025 12:52 PM
Subject: Re: [R-390] Capehart made R-390A Serial #312


> The 2nd xtal oscillator trimmers set amplitude (adjust for max), not 
> frequency. Sorry if everyone knew this but it seemed like it should be 
> said.
>
> Dave Wise
>
>> On Apr 10, 2025, at 11:42 AM, Jacques Fortin <jacques.f at videotron.ca> 
>> wrote:
>>
>> Hello Karsten,
>>
>> Can you explain how do you probe the oscillator output ?
>> It is a connection to your frequency meter that use any coaxial cable ?
>> What is the input impedance of the frequency meter ?
>>
>> Sorry to ask, but maybe you did not figure the implications: if any
>> additional capacitance is introduced in the 2nd crystal oscillator
>> structure, this will add to the C431H in the V401 circuit, then probably
>> preventing the oscillator to work on the 3rd harmonic of the crystal.
>> BTW, to answer a question asked by Larry Haney, the 31MHz band probably
>> works OK and that is because the stage works in doubler in that band (2 x 
>> 17
>> MHz).
>>
>> Are you trying to "tune" the Xtal outputs to the "right" frequency by 
>> using
>> the frequency meter, or did you use it just to confirm that the 
>> oscillator
>> is working on all ranges during the alignment process ?
>> From the Y2K-R3 alignment instructions, nothing specifies to do so.
>> The "trimmer adjustment"  instructions in the section 6.2.9 should be
>> followed without connecting anything, except the 2nd mixer, to the 2nd
>> crystal oscillator output !
>>
>> 73, Jacques, VE2JFE in Montreal
>>
>> I am currently working on realignment: checking and tuning Crystal
>> Oscillator subchassis. Frequencies measured with an accurate  8-digit
>> digital counter. Everything appears to be ok. One exception: oscillator
>> output on band 30 is 22 MHz (2nd harmonic), should be 33 MHz (3rd 
>> harmonic).
>> Active crystal is Y403 (11 MHz). Trimmer capacitor C431H appears to be 
>> ok.
>> Output (pin 3 of T401) is in the range of 3 to 5 volts and can be 
>> adjusted
>> by turning C431H. Band 8 (11 MHz osc. output) is ok. Band 19 (22 MHz osc.
>> output = 2nd harmonic) is ok. Any ideas why band 30 output is 2nd 
>> harmonic
>> and not 3rd?
>> Regards
>> Karsten
>>
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