[TenTec] Omni 6 5.5 MHz VFO PLL alignment

[Dukes HiFi]

I am actually working on the 5.0 to 5.5 MHz PLL VFO. This is unaffected by the HF crystal aging issues.

The VCXO on the board works fine. The issue is that the IF alignment requires relatively flat gain 

If  get no replies about the specific alignment for the four coils in the IF, I will derive them with the sweep generator by calculating what the passband should be and determining which of the coils centers up at which frequency.

I will, of course, share the results.

73

Gary


> On Dec 10, 2016, at 10:20 PM, Steve Ellington <steven4lq at gmail.com> wrote:
> 
> Once you get this figured out it would be a huge help to the TenTec
> community if you would write up your findings.
> I'm sure it would help others. I've dealt with a few PLL problems and
> information is scant. I do suspect part of the problems are due to crystal
> aging. I believe they get so far off frequency that the VCO has a hard time
> pulling them back.
> 
> Steve N4LQ
> 
> On Sat, Dec 10, 2016 at 10:59 PM, Dukes HiFi <dukeshifi at comcast.net> wrote:
> 
>> Actually the synthesizer in this radio is pretty simple by synthesizer
>> standards.
>> 
>> It is also rather ingenious.
>> 
>> I have found that the CPU puts more of these in the parts bin than
>> synthesizer issues.
>> 
>> But, we all have different experiences. For me, I’d rather wrestle an
>> opponent I can beat (a PLL  synthesizer) than one I cannot (a CPU with
>> proprietary chips you can no longer get at any price).
>> 
>> 73
>> 
>> Gary
>> 
>> 
>>> On Dec 10, 2016, at 12:56 PM, Steve Ellington <steven4lq at gmail.com>
>> wrote:
>>> 
>>> Good luck. PLL problems are the reason so many Omni VI's get sold for
>>> parts. :*)
>>> 
>>> On Sat, Dec 10, 2016 at 1:15 PM, Dukes HiFi <dukeshifi at comcast.net>
>> wrote:
>>> 
>>>> I did find the Omni 5 process that Barry had referenced but this only
>>>> covers centering of the VCO.
>>>> 
>>>> I need to do the loop IF alignment.
>>>> 
>>>> There is a rectifying test point at the output of this stage and I
>> assume
>>>> that there are adjustments to be made at differing frequencies using
>> the DC
>>>> voltage developed at this test point in order to get proper gain across
>> the
>>>> entire required bandpass of the VCO.
>>>> 
>>>> That’s the process I need.
>>>> 
>>>> Thanks,
>>>> 
>>>> Gary
>>>> 
>>>> 
>>>>> On Dec 10, 2016, at 12:07 PM, Dukes HiFi <dukeshifi at comcast.net>
>> wrote:
>>>>> 
>>>>> Now that I have repaired the PLL on the 5.5 mHz board of this Omni 6+ I
>>>> am repairing, I need to align the loop IF amplifier and VCO centering.
>>>>> 
>>>>> Is there a resource where I can find this process?
>>>>> 
>>>>> Gary
>>>>> 
>>>>> W0DVN
>>>> 
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