[Hallicrafters] DD-1 Audio amplifier


Carl km1h at jeremy.mv.com
Fri Feb 24 21:19:19 EST 2012


There were a fairly large number of FRR contracts that never made it into 
ham lore as it was way too sophisticated to say nothing about 4 tall 
equipment racks heavy with each individual rack panel being just one part of 
the radio.

Think WRR-2 on steroids.

Now its all something that fits on a desk

Carl
KM1H



----- Original Message ----- 
From: "Lloyd Godsey" <kk7iz at cox.net>
To: "'Carl'" <km1h at jeremy.mv.com>; "'rbethman'" <rbethman at comcast.net>; 
<hallicrafters at mailman.qth.net>
Sent: Friday, February 24, 2012 8:13 PM
Subject: RE: [Hallicrafters] DD-1 Audio amplifier


> Not to mention the Hammarlund AN/FRR-12
>
> Thanx
> Lloyd Godsey KK7IZ
> kk7iz at cox.net
> 480-620-7145
> http://www.lloydsdipsydumpster.com/
> http://antiqueradioarchives.com/
>
>
> -----Original Message-----
> From: hallicrafters-bounces at mailman.qth.net
> [mailto:hallicrafters-bounces at mailman.qth.net] On Behalf Of Carl
> Sent: Friday, February 24, 2012 4:09 PM
> To: rbethman; hallicrafters at mailman.qth.net
> Subject: Re: [Hallicrafters] DD-1 Audio amplifier
>
> National had  a diversity model of the NC-183 around 1947 and 
> Hallicrafters
> SX-28's were used during WW2.
>
> National also built big racks full of special diversity receivers under 
> some
> FRR-nn contract.
>
> Carl
> KM1H
>
>
> ----- Original Message -----
> From: "rbethman" <rbethman at comcast.net>
> To: <hallicrafters at mailman.qth.net>
> Sent: Friday, February 24, 2012 4:21 PM
> Subject: Re: [Hallicrafters] DD-1 Audio amplifier
>
>
>> Long before the SP-600-JX series, there was a Northern Radio Diversity
>> version of the SP-600 J-11(No X), that was on a Navy '51 contract.  It
>> required two receivers and also the Northern Radio LMO to keep both
>> receivers in sync frequency wise.
>>
>> I've got one, I've seen a few others.  One could select either the
>> internal LO or the external LMO.
>>
>> Bob - N0DGN
>>
>> On 2/24/2012 3:50 PM, Richard Knoppow wrote:
>>>
>>>       Fascinating!  Its possible to adapt many receivers for
>>> diversity. You need two of the same receiver and must
>>> provide access to the AVC and detector load. The SP-600-JX,
>>> especially the JX-17, came with the necessary connections.
>>> The JX-17 allows the use of an external LO source which
>>> keeps both (or more) receivers synchronized. Its helpful if
>>> the overall gain can be trimmed so that one receiver does
>>> not dominate the combination. There are special diversity
>>> combiners which provide more sophisticated switching from
>>> one to another signal. The crude arrangement possible with
>>> the SP-600 simply ties the two AVC busses and detectors
>>> together, which ever has the loudest signal predominates but
>>> the other signal is still present. A true diversity combiner
>>> switches from one to the other.
>>>       The article above gives a good survey of the history of
>>> diversity systems but I think does not mention some other
>>> anti-fading techniques such as the steerable antennas
>>> explored by Bell Labs. These were based on the discovery
>>> that the vertical angle of incoming radio signals varied
>>> with time so that a significant improvement in reliability
>>> could be achieved by making an antenna whose vertical angle
>>> could be steered to follow it. I am not sure these "MUSA"
>>> antennas were very widely used but they were described in
>>> detail in the Bell System Technical Journal and, I think, in
>>> the Journal of the IRE. I don't have citations readily
>>> available but suspect a Google search might find some.
>>>
>>>
>>> --
>>> Richard Knoppow
>>>
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