[R-390] R-390 VFO Question

Les Locklear leslocklear at hotmail.com
Wed Sep 18 10:15:50 EDT 2024 

Yes, Whoever manufactured the R-390/URR's, (Collins and Motorola) The PTO's were labeled individually. Many are missing the labels these days...
 
Les


----- Original Message -----
From: Barry <n4buq at knology.net>
To: Les Locklear <leslocklear at hotmail.com>
Cc: Bob kb8tq <kb8tq at n1k.org>, R-390 Mailing List <r-390 at mailman.qth.net>, Larry Haney <larry41gm2 at gmail.com>
Sent: 9/18/2024 9:05:21 AM
Subject: Re: [R-390] R-390 VFO Question
________________________________________________________________________________

> For the R-390/URR, are they labeled as Collins or Motorola?  In other words, 
> did Collins rebrand the Motorola PTOs or leave them branded as Motorola?  Just 
> curious so I know who made mine.  Its label shows "Collins Radio Company".
> 
> Thanks,
> Barry - N4BUQ
> 
>> On the R390/URR Collins and Motorola made PTO's.
>> 
>> On the R-390A/URR Collins, Progressitron, Dubrow, Motorola and Cosmos. There 
>> are
>> quite a few out there with Raytheon labels, but they were rebuilt under a
>> separate contract.
>> 
>> Les
>> 
>> 
>> ----- Original Message -----
>> From: Bob  Camp <kb8tq at n1k.org>
>> To: Barry <n4buq at knology.net>
>> Cc: R-390 Mailing List <r-390 at mailman.qth.net>, Larry Haney
>> <larry41gm2 at gmail.com>
>> Sent: 9/18/2024 7:20:55 AM
>> Subject: Re: [R-390] R-390 VFO Question
>> 
>> ________________________________________________________________________________
>> 
>>> Hi
>>> 
>>> Motorola most certainly made their own PTO’s for the radios they supplied. 
>>> Long
>>> ago I talked to the folks who did the linearity adjustments on them. They 
>>> still
>>> had (not so) fond memories of doing those adjustments.
>>> 
>>> Bob
>>> 
>>>> On Sep 17, 2024, at 11:29 PM, Barry <n4buq at knology.net> wrote:
>>>> 
>>>> Hi Larry,
>>>> 
>>>> Regarding the tutorials, I'm wondering which might apply to the PTO in the
>>>> R-390A/URR.  I see most(all?) of them are regarding the COSMOS units but am
>>>> wondering which PTO is in the R-390/URR and whether any of the
>>>> rebuild/linearity documents apply to that one.  Were all the R-390/URR PTOs
>>>> made by Collins and no COSMOS in that version?
>>>> 
>>>> Mine is running just a bit fat - maybe 1.5 kc end-to-end.  I have the actual
>>>> numbers written down and can post that when I get back to the workbench.  
>>>> From
>>>> what I remember, removing a turn shortens the end-to-end but perhaps 
>>>> additional
>>>> C would work as well.  I
>>>> don't know what effect that might have on linearity but I don't think it 
>>>> should.
>>>> 
>>>> The R-390A/URR PTO has an endpoint adjustment.  Does this exist for the PTO
>>>> in an R-390/URR?
>>>> 
>>>> Thanks,
>>>> Barry - N4BUQ
>>>> 
>>>>> Hi Barry,  I thought what you wrote makes sense and is correct.  It's good
>>>>> that you are understanding how it all works.  It makes diagnosys so much
>>>>> easier.  Good going.
>>>>> 
>>>>> If you're interested in more reading on the 390A PTO's, there are 3 docs on
>>>>> our website in the repair tutorials section by Tom Marcotte, Jim Miller and
>>>>> myself.
>>>>> 
>>>>> Regards, Larry
>>>>> 
>>>>> On Mon, Sep 16, 2024 at 5:51 AM Barry Scott <72volkswagon at gmail.com> wrote:
>>>>> 
>>>>>> Okay, Larry.  Thanks for the reply.
>>>>>> 
>>>>>> On further reading, the VFO is a Hartley design and, given that the
>>>>>> frequency formula for a Hartley is an inverse function of the LC values,
>>>>>> presuming that at xx 000, the iron core is "out" of the coil and a
>>>>>> clockwise turn of the KC knob causes the core to be pushed further inside
>>>>>> the coil increasing the L, then the frequency would indeed drop with CW
>>>>>> motion of the knob.  Sorry for the awkward way of stating that but I think
>>>>>> it makes sense to me.
>>>>>> 
>>>>>> Thanks again,
>>>>>> Barry - N4BUQ
>>>>>> Thanks,
>>>>>> Barry - N4BUQ
>>>>>> 
>>>>>> 
>>>>>> On Sun, Sep 15, 2024 at 11:10 PM Larry Haney <larry41gm2 at gmail.com> wrote:
>>>>>> 
>>>>>>> Hi Barry,  You are absolutely correct in your deductions.  When the KC is
>>>>>>> at its lowest of 000, the vfo is at its highest (3.455 mh).
>>>>>>> 
>>>>>>> Regards, Larry
>>>>>>> 
>>>>>>> On Sun, Sep 15, 2024 at 7:23 PM Barry Scott <72volkswagon at gmail.com>
>>>>>>> wrote:
>>>>>>> 
>>>>>>>> Looking at the simplified schematic for the 3rd mixer (V205), the output
>>>>>>>> from the 2nd mixer (V204) tunes from 3 to 2 MC and the VFO tunes from
>>>>>>>> 3.455
>>>>>>>> MC to 2.455 MC yielding a constant 455 kc mixer product.  Is it correct
>>>>>> to
>>>>>>>> interpret those numbers to mean that if the counter starts at XX  000
>>>>>> and
>>>>>>>> the KC control is rotated CW to XX +000 the VFO's output frequency
>>>>>> starts
>>>>>>>> at 3.455kc and falls 1000 kc for 10 turns CW on the KC knob?
>>>>>>>> 
>>>>>>>> I'm asking because I want to know what the frequency of the VFO is
>>>>>>>> supposed
>>>>>>>> to be when the dial is at XX  000 and I presume it's 3.455 kc but
>>>>>> wanting
>>>>>>>> to make sure.
>>>>>>>> 
>>>>>>>> Thanks,
>>>>>>>> Barry - N4BUQ
>>>>>>>> ______________________________________________________________
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>>>>>>> 
>>>>>> ______________________________________________________________
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>>>>> ______________________________________________________________
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>>> 
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