Fwd: [R-390] Synthesizers, was 390() vs 390(A)

[William J.Neill]

One other proposed USN dual-diversity radio receiving set was, I think, 
the AN/FRR-49.  It is pictured in the "radio receiving sets" section of 
an original nine-volume compendium of USN communication equipment dated 
around 1956 that I obtained from the USN Publications Distribution 
Center in Philadelphia about two decades ago.  The set consists of two 
R-390( ) receivers coupled to, of all things, a AN/URA-8.  Because 
there's a photo of the proposed set, I can only presume that someone 
somewhere thought this sucker would work.  There's lots of other nifty 
things throughout the nine volumes and every piece of equipment is given 
a superficial description of its capabilities as well as FSN number, 
proponent agency (USN, DA, USAF, NSA, etc.) and appropriate TM's.  Of 
course, where proposed equipment is depicted, there is a statement "no 
TM published.

Bill Neill
Conroe, Texas

Begin forwarded message:

> From: "John KA1XC" <tetrode at comcast.net>
> Date: Wed Dec 29, 2004  08:28:56  US/Central
> To: "William J. Neill" <wjneill at lcc.net>
> Subject: Re: [R-390] Synthesizers, was 390() vs 390(A)
>
> Yes, that's it! I knew there was another converter that was like the 
> CV-116
> but I couldn't remember the model number, never seen one either.
> Thanks Bill,
> John
>
> ----- Original Message -----
> From: "William J. Neill" <wjneill at lcc.net>
> To: "John KA1XC" <tetrode at comcast.net>
> Sent: Wednesday, December 29, 2004 8:52 AM
> Subject: Re: [R-390] Synthesizers, was 390() vs 390(A)
>
>
>> There's one more item that made use of the tuning loops:  the CV-115.
>> It's basically one-half of a CV-116.
>>
>> Bill Neill
>> Conroe, Texas
>>
>> On Tuesday, December 28, 2004, at 10:42 , John KA1XC wrote:
>>
>>> Well, a communications frequency synthesizer must not only generate 
>>> the
>>> desired frequency but must do it cleanly, meaning without adding noise
>>> sidebands AND reference sidebands. In a typical synthesizer the PLL
>>> bandwidth is usually made sufficiently high to knock down the VCO 
>>> phase
>>> noise, but this is exactly the opposite of what is needed to attenuate
>>> the
>>> reference from frequency modulating the VCO; this would require 
>>> using a
>>> loop
>>> bandwidth MUCH smaller than the reference frequency. It's the classic
>>> engineering example of  conflicting requirements which in turn leads 
>>> to
>>> increasing design complexity. Good modern synthesizers must use two 
>>> and
>>> even
>>> three loops to achieve small tuning increments without generating all
>>> kinds
>>> of garbage off the side.
>>>
>>> Sounds like the guys who designed the crystal synthesizer were able to
>>> make
>>> good reference frequencies, but they were probably full of mixing
>>> products
>>> and thus unusable directly. But by locking a high Q (thus low noise) 
>>> LC
>>> VFO
>>> (not VCO) to them with an electro-mechanical feedback loop, it
>>> completely
>>> isolated the VFO from being modulated by the reference frequency. I 
>>> bet
>>> the
>>> whole thing probably had an effective loop bandwidth of just a few
>>> hertz!
>>>
>>> Electro-mechanical PLL's and FLL's are classic 1950's and 60's
>>> technology,
>>> just like the R-39x mechanical RF deck. Other related gear that made
>>> use of
>>> electro-mechanical tuning loops were the CV-116 FSK converter and
>>> CV-157 SSB
>>> converter.
>>>
>>> John
>>>
>>>
>>> ----- Original Message -----
>>> From: "Dave Maples" <dsmaples at comcast.net>
>>> To: "Michael Murphy" <mjmurphy45 at comcast.net>; <paul at pdq.com>; "Barry
>>> Hauser" <barry at hausernet.com>
>>> Cc: <r-390 at mailman.qth.net>
>>> Sent: Tuesday, December 28, 2004 9:30 PM
>>> Subject: RE: [R-390] 390() vs 390(A)
>>>
>>>
>>>> All: I once had an ARC-38A and associated 180L-3 automatic tuner.
>>> Autotune
>>>> mechanisms in both of those were typical Collins.  The most bizarre
>>>> part
>>> of
>>>> the operation was the frequency control for the ARC-38A.  They used 
>>>> an
>>>> electromechanical phase-locked loop.  It was strange: the VFO 
>>>> frequency
>>> was
>>>> compared to a crystal-synthesized reference switched by the autotune
>>>> mechanism, and the VFO shaft was driven with a motor to match the
>>> reference.
>>>> The control loop was a proportional / integral loop!  Very
>>>> strange...they
>>>> had crystals to synthesize the reference in 500 Hz steps...why not 
>>>> just
>>> use
>>>> that to control frequency???
>>>>
>>>> Dave Maples
>>>>
>>>
>>>
>>> _____________________________________________________________
>>> Win a new Icom IC-756PROIII and help QSL/QTH.net
>>> Details at: http://mailman.qth.net/index.html
>>> _____________________________________________________________
>>> R-390 mailing list
>>> Home: http://mailman.qth.net/mailman/listinfo/r-390
>>> Help: http://mailman.qth.net/faq.htm
>>> Post: mailto:R-390 at mailman.qth.net
>>> Unsubscribe: http://mailman.qth.net/mailman/options/r-390
>>>
>>
>
>
>