[MRCA] 1155

[Scott Johnson]

Certainly not the Western Electric  ARC-4, which was a pre-war civil design
pressed into military service by the USN.  I think WE was trying to get the
pre-war CAA to consider VHF for ATC purposes, and this was an experiment,
and not a very successful one at that.  Surely the Collins ARC-1 could be
considered the best or the great war lot, but it came very late, and only to
the pacific theater, AFAIK.  I was used until the mid seventies though!  The
ARC-5 VHF was probably worse than the SCR -522, the ARC-3 better, but again,
a late entry.  I operate both a BC-639/640 combination and an ARC-1 on a
local 2M AM net, and receive good reports on both.  I have, however narrowed
up the IF in the 639 considerably.
The ARC-4 does not have enough sensitivity for the local net, and I don't
have the patience to lash up the ARC-3 or ARC-5 VHF set for a trial.

Scott W7SVJ

-----Original Message-----
From: mrca-bounces at mailman.qth.net [mailto:mrca-bounces at mailman.qth.net] On
Behalf Of J. Forster
Sent: Saturday, July 07, 2012 10:13 AM
To: Jack Antonio
Cc: mrca at mailman.qth.net; milsurplus at mailman.qth.net
Subject: Re: [MRCA] 1155

> On 7/7/2012 12:15 PM, J. Forster wrote:
>
> Neither the BC-348 nor the ART-13 was available at the start of WW II.
>
> Not so sure about that concerning the  -348. I have a BC-224-B which 
> has a contract date of 5 January 1939. My -348-C has a contract date 
> of 1941. At least the 348 was available very early in the war, and 
> certainly predates the AN/ART-13.

The war did not start on Dec 7 1941, but when Hitler marched into Poland.

>> OK, the SCR-522 was a POS. At the time it was introduced, what was 
>> better?
>>
>> -John
>
> After collecting and firing up an SCR-522, I feel it is actually a 
> decent set, given the technology of the time. Certainly better than 
> the WE-233A (AN/ARC-4).

I never said it was a POS. I was quoting an earlier post, trying to make the
point that the relevant question is whether it is better than the other
options.


> However, the SCR-522 has some rather interesting design "features", it
> is not a simple set to troubleshoot.  I don't know if these
> "features" were a result of its British legacy, or Bendix, who
> seemed to be fond of rather convoluted control schemes.

I think it was pretty much cloned from a British design, like the WS 19.

> First was the regulated 13V filament voltage, in both the 12 and 24
> volt versions.  The dynamotor provided the filament voltage, and had
> a carbon pile regulating the field current.

So did the R.1155. The dyno had a series regulator controlled by the
unobtainable "Londex" relay. The dyno was about 10 V and would work over a
wide input range.


> Indeed I have read
> that the original dynamotor supplies were maintenance dogs and had
> to be redesigned.  The regulated filament voltage never appeared on
> later WWII VHF radios.

OK. I know the T.1154 dynos were troublesome, but they were very high
voltage machines. The HV commutators blew over at altitude, I think.

> Second was a PTT scheme that had a relay drop out for transmit and
> energized for receive.  The entire PTT scheme involved multiple relays
> and is not a straightforward thing to trace. To me, it seemed to
> be overcomplicated, and I've wondered what the design goals were
> that warranted it.
>
> Jack Antonio WA7DIA/4

The sets were designed in a hurried run-up to WW II, in a country with far
fewer resources than the US, and built in factories and by people being
bombed daily. IMO, they did pretty well.

Best,

-John

================

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