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 <[email protected]>
To: Barry <[email protected]>
Cc: R-390 Mailing List <[email protected]>, Larry Haney
<[email protected]>
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 <[email protected]> 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 <[email protected]> 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 <[email protected]> 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 <[email protected]>
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:[email protected]
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:[email protected]
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:[email protected]
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:[email protected]
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:[email protected]
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:[email protected]
This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
