[R-390] Frequency Synthesis on the R-390/A

[John Vendely]

There were at least two external synthesizer arrangements developed for the 
R-390A over the years, including the one by done by TMC.  The Manson 
Laboratories version was probably the most common. Manson developed numerous 
versions of their stock multiloop serial injection PLL synthesizer for a 
variety of retrofit applications, such as a synthesized SSB version of the 
AN/FRT-24 transmitter.  They also had a line of HF receivers and 
transmitters of their own, which are seldom seen today.   Incidentally, 
Manson did a version of the 2.433-3.455 Mc R-390 synthesizer which tuned in 
100 cycle steps.

In a way, connecting an R-390A to the Manson synthesizer set was a bit like 
pearls before swine.  Few receivers, including modern ones, have L.O. chain 
phase noise as low as the R-390 series.  THe Manson synthesizers had very 
low discrete spurious levels, but phase noise was poor, and in that respect 
considerably degraded the receiver's performance.  They were also 
notoriously unreliable, though this is forgiveable to an extent, considering 
the early 60's synthesizer technology.  The Manson synthesizer arrangement 
solved the problem of long-term stability, but degraded the receiver in 
other ways.

It's often stated that the R-1247 and its companion synthesizers were 
developed for NASA for the Apollo space program.  This is a myth, often 
propagated by folks selling them.  It was developed for the AN/GRC-129 RATT 
van, which was considered a synthesized SSB upgrade to the AN/GRC-26.  NASA 
used the R-390 series for a variety of purposes, including general HF 
reception and use as a tuneable IF for various downconverters.  They did 
indeed have a few of the Manson-equipped R-390As, but they experienced 
continual problems with them, and all were removed from service after just a 
short time.  By the mid 60s, several much better synthesized receivers were 
available and in widespread use.

On a side note, TMC supplied the HF transmitters and receivers for NASA's 
worldwide tracking and communications network, under contract to Western 
Electric, the prime contractor for the network, starting with Project 
Mercury.  TMC supplied GPT-10K and GPT-40K transmitters, and DDR-6 and DDR-5 
receivers, all done up in the bilious institutional green color favored by 
NASA.  The transmitters were
in use up to the early 1980s at the Malabar Transmitter Annex  which was 
(and still is) the transmitter site for Cape Radio.   NASA green TMC 
equipment is still occasionally seen floating around...

73,

John K9WT
Malabar, FL

----- Original Message ----- 
From: "Steve Toth" <stoth47 at yahoo.com>
To: <r-390 at mailman.qth.net>
Sent: Friday, August 14, 2009 4:08 PM
Subject: Re: [R-390] Frequency Synthesis on the R-390/A





Tisha
I would also be interested in a copy of the docs you found and pay for the 
copying and postage.

I have what is possibly an R-1981. It's an early Collins with the front 
panel that takes a long Collins tag instead of the Manson Labs tag, and it 
has the 17Mhz input / output mods installed. The previous owner picked it up 
at an estate sale in Florida of a ham that worked for NASA and claimed it 
was formerly used in Vietnam. It's either a NASA R-1247 with a changed out 
front panel (most likely - although it has no Manson labs markings on any of 
the modules), or an R-1981 - I'm just not sure which.

Per the R-390A FAQ page - The R-1981.
"The R-1981 was a R-390A modified to bring out the 17 MHz, HFO and VFO 
signals to the rear panel and to insert an error correction signal for 
high-stability operation. It was a part of the TSC-25 communications system. 
The modifications were done using a kit of parts from The Technical Material 
Corporation (TMC) under contract number 14385-PC-58."

And from a past email I received off list a while ago from Tom, NU4G (thanks 
Tom!):

"I also have the two synthesizer decks for your R-1247 - I was supposed to 
also get an R-1247, but it never materialized.**

**(Which is just as well. Imagine dialing up a freq on the receiver, then 
cranking on TWO boxes - one for MC and one for KC, to tune to a freq. The 
GRC-129 system was an interesting contraption that used two of your 
receivers controlled by the synth - the pair was set up in diversity mode. 
The transmitter was a highly Manson-modified T-368 that was redesigned for 
SSB only. "Contraption" is a good system description, as is "haywire." There 
were better things in production at the time, who knows how the contract for 
that system was ever approved. heehee Nonetheless, it's still interesting.)


-- Steve






Woodinville, WA
In any hobby there is no such thing as "over kill" - just budget 
limitations.


--- On Fri, 8/14/09, Richard Green <k7yoo at yahoo.com> wrote:


From: Richard Green <k7yoo at yahoo.com>
Subject: Re: [R-390] R-390 Digest, Vol 64, Issue 21
To: r-390 at mailman.qth.net
Date: Friday, August 14, 2009, 10:28 AM


I thought that version of the R390A was called the R 1247. I have one that 
was done by Manson Labs and it has the most linear PTO of ANY Collins radio 
I have ever owned. I would like a copy of the docs on this version and 
certainly would pay for copying and postage.



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