[Hallicrafters] DD-1 Audio amplifier |
Carl
km1h at jeremy.mv.com
Fri Feb 24 18:30:48 EST 2012
----- Original Message -----
From: "Richard Knoppow" <1oldlens1 at ix.netcom.com>
To: "Duane Fischer, W8DBF" <dfischer at usol.com>; "Waldo Magnuson"
<magnuson at mac.com>; <Hallicrafters at mailman.qth.net>
Cc: "Waldo Magnuson" <magnuson at mac.com>
Sent: Friday, February 24, 2012 4:58 PM
Subject: Re: [Hallicrafters] DD-1 Audio amplifier
>
> ----- Original Message -----
> From: "Duane Fischer, W8DBF" <dfischer at usol.com>
> To: "Richard Knoppow" <1oldlens1 at ix.netcom.com>; "Waldo
> Magnuson" <magnuson at mac.com>;
> <Hallicrafters at mailman.qth.net>
> Cc: "Waldo Magnuson" <magnuson at mac.com>
> Sent: Friday, February 24, 2012 1:21 PM
> Subject: Re: [Hallicrafters] DD-1 Audio amplifier
>
>
>> Richard,
>>
>> Per my prior post of the specifications of the DD-1 by
>> Chuck Dachis, Radios By Hallicrafters 2nd Edition, the
>> frequency response was 200 Hz to 6000 HZ. More than
>> adequate for speech communications and not too shabby for
>> general listening either!
>>
>> Because Bill Halligan, Sr., and his partner Toby, traveled
>> the world, literally, to purchase the best transformers,
>> resistors, capacitors etc. it is most likely that the DD-1
>> contained the best quality components they could procure.
>>
>> Now let me state without prejudice, that a very brilliant
>> Engineer designed the DD-1, and it did have its share of
>> proponents and opponents among the Hallicrafters powers
>> that were. This same Engineer designed two other receivers
>> that I am aware of. One was a brilliant success, the other
>> was a total flop. Primarily because the Engineer refused
>> to make several changes in the RX that other Engineers
>> told him were needed. Ego got in his way, the SX- failed
>> badly and he lost his job.
>>
>> Yes I know his name, but most of you probably know of whom
>> I am speaking of already.
>>
>> While I was performing around our country I used a HME
>> Dual Diversity receiver with a wireless lapel microphone.
>> It performed nothing short of fantastic! I suspect the
>> Engineer who designed the DD-1 might have been too many
>> years ahead of the engineering mentality of the time.
>>
> I don't have the details in mind right now but
> diversity, I think in the form of polarization diversity, is
> commonly used in microwave relay and studio to transmitter
> links because variations in the air cause preferential
> fading of one or the other path.
** First Ive ever heard of that!
They do run 2 programs or other transmissions on the same frequency by using
H and V polarization and thats also used in satellite TV and other
communications. There is a 25dB or better difference between them.
I don't remember when the
> simple expedient of using either two antennas or circularly
> polarized antennas was first used. Microwaves are subject to
> effects from water vapor in the atmosphere which can cause
> all sorts of problems.
** Its called attenuation.
Heavy rain can also cause scattering above about 10GHz and hams use it to
get over or around obstacles
Carl
KM1H
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