[Boatanchors] ARC 5 stuff - LIST

[jeremy-ca]

----- Original Message ----- 
From: "J Forster" <jfor at quik.com>
To: "jeremy-ca" <km1h at jeremy.mv.com>
Cc: "Jim Brannigan" <jbrannig at optonline.net>; <boatanchors at mailman.qth.net>; 
"Meir WF2U" <wf2u at starband.net>
Sent: Sunday, September 23, 2007 5:43 PM
Subject: Re: [Boatanchors] ARC 5 stuff - LIST


> jeremy-ca wrote:
>
>> When did YOU ever see a manual for most of the WW2 surplus that was
>> released? The smarter hams did a reverse engineering and wrote up the
>> circuits and conversion in a series of CQ Magazine articles in the late
>> 40's.
>> It was strange to see gear released to the public by the tons but the
>> manuals were still classified.
>
> I just looked at an original 1945 ARC-5 manual and the cover clearly 
> states it
> replaced a 1944 version and is UNCLASSIFIED. Dates and manual numbers upon
> request.


What you are looking at in 2007 has absolutely no bearing on what was 
available to the ham in 1947. These days it is all available as reprints, 
CD's or downloads.


>
> It does not take a lot of reverse engineering to figure out that a set 
> with a
> series variable inductor connected to the antenna terminal is designed to
> connect to a load that looks capacitive, or that antennas on planes and 
> tanks
> are electrically short, hence  capacitive. AFAIK, in those days you 
> actually had
> to understand a bit about circuits to get a ticket. A series LCR is about 
> as
> simple as you can get. Also, the transmitters were often tuned up for 
> maximum RF
> amps (eg: BC-442), which is a pretty obvious indication that you were 
> trying to
> resonate a series LC.


You make my point very well. In those days hams had to actually know 
circuitry to get a General and a lot more for the Advanced. These days you 
get the license at Wal Mart.


>
>> Time and again I've read about
>> > TVI and other spurious problems in WW II gear when some jerk has the 
>> > thing
>> > grossly mismatched and the B+ cranked up to several times the design 
>> > spec.
>>
>> 1500V on an ARC-5 TX? I think not. That didnt even happen with the BC375 
>> or
>> ART-13 and the famous BC-610. They were great TVI and harmonic generators
>> all by themselves since there was no government (FCC)regulation on 
>> military
>> gear.
>
> Maybe not 1500 VDC, but certainly in excess of the design spec.


If the design spec is 500V and the tube is rated at 750V and a ham uses that 
voltage along with other correct parameters then what is your problem? 
Components in the amplifier stage of an ARC-5 TX can easily handle the 
voltage and operating that way doesnt generate any more clicks than in stock 
form. Hams have had to improve the circuitry of many old military rigs in 
order to make their poor signals acceptable on the ham bands. Ive listened 
to several unmodified ones that sound like a CBer designed them.

1941 high end ham equipment was designed in 1940-41. However 1941 military 
equipment was usually of a mid 30's or earlier design, no high level 
engineering skills required to be the lowest bidder.


>
>> The designers in WW II were NOT fools.
>>
>> Nope, they just built to a spec that was handed to them for a very
>> disposable piece of equipment. The primary criteria was ruggedness under
>> combat use and easy to operate by even a Marine. (I couldnt resist)
>> OTOH, commercial gear had to satisfy a much wider criteria of use.
>
> I've seen hundreds of examples of ham hacked gear. Some was neatly done, 
> but the
> vast majority was junk. I am generally unimpressed by the capabilities of 
> the
> hams of those days.


Im even less impressed with the hams of today and since you dont use a call 
sign I have to assume that your comments are more from some personal bias 
than actual experience.


>
> Commercial gear is often loaded with bells and whistles, so as to give it 
> an
> advantage in the market place, but such additions often add little to the 
> basic
> mission. The military usually does not buy or spec such frivolities.


OH? I can think of many military items that are probably way too much for 
the SWL and many hams. There is a BIG difference between mission specific 
items for combat aircraft vs capital ships of the Navy, shore installations, 
NSA, and many other goverment organizations.

With all the secrecy involved plus the complexity of todays military 
electronics almost nothing is reaching the public. The best items Ive found 
are high power VHF & UHF amps that can be put on ham frequencies with a bit 
of work. It helps to have a VNA on my work bench.

Carl
KM1H





>
>> (OTOH, some of the early TV designers might
>> > well have been.)
>>
>> Mad Man Muntz and the Hallicrafters TV come to mind.
>>
>> Carl
>> KM1H
>
> Yeah, and poorly shielded TVs were (and in some cases still are) the root 
> cause
> of TVI. Economic pressures forced them to be cheap, and political pull 
> likely
> exempted them from EMI emission specs.
>
> FWIW,
> -John
>
>