[R-390] R-390 VFO Question

Les Locklear leslocklear at hotmail.com
Wed Sep 18 10:31:17 EDT 2024


That's correct. I had many Motorola contacts years ago a few that worked in development at Wright Patterson AFB.
 
Bob is right, Motorola made their "own" PTO's. But finding a Collins or Motorola R-390/URR or R-390A/URR these days with the original PTO that
was with the receiver when manufactured, would be akin to finding the "Holy Grail."
 
 
Les


----- Original Message -----
From: Bob  Camp <kb8tq at n1k.org>
To: Les Locklear <leslocklear at hotmail.com>
Cc: Barry <n4buq at knology.net>, R-390 Mailing List <r-390 at mailman.qth.net>, Larry Haney <larry41gm2 at gmail.com>
Sent: 9/18/2024 9:25:43 AM
Subject: Re: [R-390] R-390 VFO Question
________________________________________________________________________________

> Hi
> 
> AFIK, Motorola never made PTO’s for anybody else. They had “way too much fun” 
> just making them for their own production radios. 
> 
> Based on chat’s with the folks at Collins, everything that went into their 
> radios came out of their factory. They obviously sourced many (but not all …) 
> components. All the assemblies got done “in house”. 
> 
> Bob
> 
>> On Sep 18, 2024, at 10:15 AM, Les Locklear <leslocklear at hotmail.com> wrote:
>> 
>> 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
>>>>>>>>>> ______________________________________________________________
>>>>>>>>>> R-390 mailing list
>>>>>>>>>> Home: http://mailman.qth.net/mailman/listinfo/r-390
>>>>>>>>>> Help: http://mailman.qth.net/mmfaq.htm
>>>>>>>>>> Post: mailto:R-390 at mailman.qth.net
>>>>>>>>>> This list hosted by: http://www.qsl.net
>>>>>>>>>> Please help support this email list: http://www.qsl.net/donate.html
>>>>>>>> ______________________________________________________________
>>>>>>>> R-390 mailing list
>>>>>>>> Home: http://mailman.qth.net/mailman/listinfo/r-390
>>>>>>>> Help: http://mailman.qth.net/mmfaq.htm
>>>>>>>> Post: mailto:R-390 at mailman.qth.net
>>>>>>>> This list hosted by: http://www.qsl.net
>>>>>>>> Please help support this email list: http://www.qsl.net/donate.html
>>>>>>> ______________________________________________________________
>>>>>>> R-390 mailing list
>>>>>>> Home: http://mailman.qth.net/mailman/listinfo/r-390
>>>>>>> Help: http://mailman.qth.net/mmfaq.htm
>>>>>>> Post: mailto:R-390 at mailman.qth.net
>>>>>>> This list hosted by: http://www.qsl.net
>>>>>>> Please help support this email list: http://www.qsl.net/donate.html
>>>>>> ______________________________________________________________
>>>>>> R-390 mailing list
>>>>>> Home: http://mailman.qth.net/mailman/listinfo/r-390
>>>>>> Help: http://mailman.qth.net/mmfaq.htm
>>>>>> Post: mailto:R-390 at mailman.qth.net
>>>>>> This list hosted by: http://www.qsl.net
>>>>>> Please help support this email list: http://www.qsl.net/donate.html
>>>>> ______________________________________________________________
>>>>> R-390 mailing list
>>>>> Home: http://mailman.qth.net/mailman/listinfo/r-390
>>>>> Help: http://mailman.qth.net/mmfaq.htm
>>>>> Post: mailto:R-390 at mailman.qth.net
>>>>> This list hosted by: http://www.qsl.net
>>>>> Please help support this email list: http://www.qsl.net/donate.html


More information about the R-390 mailing list