[TenTec] Paragon Reference Oscillator

[Bob McGraw K4TAX]

Pete;
If you get the reference oscillator on frequency and the BFO is off then the digital display will also be off frequency.  

The reason I keep mentioning this is that I’ve seen no evidence other than your statement “the BFO’s are working correctly”.  

I do not agree modifying the circuit will be a solution.   From experience having owned 2 different Paragon radios and repairing many many of these with various issues, this is a 40 year old radio and design.  If one ends up with a +/- 100 Hz error, I’d stop tweaking.   

Bob, K4TAX


Sent from my iPhone

> On Oct 25, 2020, at 8:00 PM, Pete Ferrand <petef at sprynet.com> wrote:
> 
> 
> 
>> 
>> The reference oscillator frequency is not related to the BFO oscillators. 
> 
> I never said it was, you mentioned it and the BFOs are working correctly. The reference oscillator is off frequency, hence the subject in the email. I want to fix that.
> 
> This may be due to age, someone's replacement part, or perhaps it was off from the factory, whatever.
> 
> My point is yes, the likely problem is the 42 MHz crystal. However, there is no way to order an crystal meeting Ten-Tec's spec because they never published a spec. Therefore the new one may be 200 Hz off as well, or a lot more. That is why modifying the circuit would be far easier and that is what I asked for help with.
> 
> Pete
> 
> 
> 
>> 
>> The BFO is 2 crystals which are trimmed by 4 switched trimmers.  From experience, the BFO adjustments do have some interaction with each other, thus the reason for going over the sequence a couple of times.  
>> 
>> If the reference oscillator won’t come on frequency then either a component has changed value due to age and this includes the 42MHz crystal.  
>> 
>> Bob, K4TAX
>> 
>> 
>> Sent from my iPhone
>> 
>>>> On Oct 25, 2020, at 7:20 PM, Pete Ferrand <petef at sprynet.com> wrote:
>>> 
>>> 
>>> Thanks for responding you guys but I don't think you understood what I'm saying.
>>> 
>>> I can't leave the reference oscillator at 84 MHz because it's not at 84 MHz! 
>>> 
>>> The best I can do is adjust it to 300 Hz lower in frequency than 84 MHz. The specs call for plus/minus 5 Hz. I thought this was clear.
>>> 
>>> Why do you guys want me to start with the BFO adjustments? 
>>> 
>>> I've aligned dozens of Ten-Tecs and I've always followed the Ten-Tec alignment procedures, which call for starting by setting the reference oscillator.
>>> 
>>> It seems absurd to tune the BFOs when the reference oscillator is off frequency!!!
>>> 
>>> Hence, I need to simply add frequency to the crystal. About 200 Hz would do it.
>>> 
>>> This is the problem. When the reference is correct the rest of the USB/LSB/CW/FM tuning is perfectly fine. But the reference oscillator can't be put on frequency.
>>> 
>>> 
>>> 
>>> Thanks.
>>> Pete
>>> 
>>> 
>>> 
>>> 
>>> 
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>>> 
>>> 
>>> -----Original Message-----
>>>> From: "Bob, WB2VUF via TenTec" <tentec at contesting.com>
>>>> Sent: Oct 25, 2020 6:20 PM
>>>> To: Discussion of Ten-Tec Equipment <tentec at contesting.com>, Bob McGraw K4TAX <rmcgraw at blomand.net>
>>>> Cc: "Bob, WB2VUF" <wb2vuf at verizon.net>
>>>> Subject: Re: [TenTec] Paragon Reference Oscillator
>>>> 
>>>> I agree. Leave the reference oscillator exactly at 84 MHz and align the 
>>>> BFO crystals instead.  They are the most likely to be off frequency.  
>>>> Yes, they must be adjusted in sequence as indicated in the manual.
>>>> 
>>>> 73,
>>>> 
>>>> Bob WB2VUF
>>>> 
>>>>> On 10/24/2020 11:23 AM, Bob McGraw K4TAX wrote:
>>>>> The first thing to check is the oscillators on the Transmit Audio/BFO 
>>>>> Board.  The procedure is on page 6-65 of the manual. From experience, 
>>>>> the adjustments are somewhat interactive and must be done in the order 
>>>>> as listed.  You should go through the procedure at least twice.  Be 
>>>>> sure the radio has been on for 1 hr to allow the temperature to 
>>>>> stabilize as the crystals are subject to drift with temperature.
>>>>> 
>>>>> As to the 42 MHz crystal, it may have aged to the point that it will 
>>>>> not be in the range needed.    Replacement is the most likely option.
>>>>> 
>>>>> 73
>>>>> 
>>>>> Bob, K4TAX
>>>>> 
>>>>> On 10/24/2020 2:54 AM, Peter Ferrand wrote:
>>>>>> I have a new-to-me Paragon 585.
>>>>>> 
>>>>>> The rig is slightly off frequency from its readout and the best I can 
>>>>>> do is adjust the reference oscillator with C1 to 300 Hz lower in 
>>>>>> frequency than the 84 MHz it's supposed to be. Ten-Tec specifies this 
>>>>>> frequency must be plus or minus 5 Hz at 84 MHz, which is the output 
>>>>>> of the frequency doubler.
>>>>>> 
>>>>>> I tried removing or reducing C2 but the oscillator stops oscillating. 
>>>>>> Rather than track down a new 42 MHz crystal, I wonder if anyone with 
>>>>>> more design skills than I have can suggest a slight redesign of the 
>>>>>> circuit to pull the existing crystal higher.
>>>>>> 
>>>>>> Thanks.
>>>>>> Pete
>>>>>> WB2QLL
>>>>>> Mount Pleasant, WI
>>>>>> 
>