[R-390] R-390 VFO Question
Bob Camp
kb8tq at n1k.org
Wed Sep 18 10:25:43 EDT 2024
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
>>>>>>>>> ______________________________________________________________
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>>>>>> ______________________________________________________________
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