Hi Karsten,
Well, just figure that 1 meter of RG-58 represent about 93pF connected to
the T401 secondary.
In normal operation, it is not supposed to be there.
We can calculate the capacity reflected to the primary winding, but this
will not change the result.
The T401 primary cannot be made resonant at 33 MHz with that added
capacitance from your test setup.
And from my opinion, even a 1 ft length (23.5pF) is too much.
The small length of RG-179 going to the P215 (2nd mixer V203) was already
included in the calculations for the value of C431H to be used.
There is nothing defective in your R-390A, it is your test setup !!!
73, Jacques, VE2JFE in Montreal
Hello Jaques,
maybe You point in the right direction. Your questions:
* how do you probe the oscillator output ?
Connect frequency counter input to J415 on Oscillator Subchassis.
Connection is by 3 ft (1 meter) RG58. Counter input is switchable either 1
Megohm or 50 Ohm. No difference 50 Ohm <> 1 Meg.
* this will add to the C431H in the V401 circuit - Maybe the cause? I
will try a shorter piece RG58 (1 ft) tomorrow.
* 31 MHz works ok.
* Counter is being used to confirm that all Xtal frequencies work ok.
* Will study Y2K-R3 6.2.9 again tomorrow.
73 + many tnx for your thoughts
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