[Hammarlund] sp-600 2nd osc

[Richard Knoppow]

    It should be 3.5 Mhz. You are not far off, this is only 0.3% 
off. I don't know how accurate the crystals are supposed to be.
    If you are making a direct connection to the oscillator you 
may be pulling the frequency slightly.
    Note that the 455 Khz crystal filter will be very slightly 
off too. It establishes the 455 Khz IF frequency. The high band 
conversion uses a second IF at 3955 Khz. If the second conversion 
oscillator is at 3.49 Mhz its one Khz off. I don't think that is 
enough to affect the dial calibration.
    The manuals say to adjust both IF strips by injecting a 
signal at the grid of the first converter tube. That would insure 
that both IFs are tuned to very close to the correct frequency. 
The final frequency is set by the crystal filter frequency so 
when you have done the preliminary tuning you must go over it 
again to make any small corrections.
    I am not sure if the high frequency IF can be tuned off 
enough to get on the wrong side of the second conversion 
oscillator but tuning the IF using an injected signal of known 
frequency will eliminate that if it turns out to be possible. I 
don't think the conversion crystal error is enough to cause a 
problem.

On 11/13/2019 2:37 PM, wb3fau55 at neo.rr.com wrote:
> I measured the xtal in the 2nd osc. as measured on 2 different freq
> counters it is 3.49 mc. is this too low? Russ.
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-- 
Richard Knoppow
1oldlens1 at ix.netcom.com
WB6KBL