[ARC5] interesting ?

[Tim]

Hi Mike - Interesting stuff....I have an APR-4 with several tuning units.
It operates on either 115V 400 or 60 cps AC power (plus 28VDC for the motor
I think) , 60 cps is something I always wondered about.  For an airborne
set anyway.
Perhaps that was a holdover from the GR Lab instrument design?  Or maybe
for shipboard ESM work?

Tim
N6CC

On Fri, Feb 23, 2018 at 7:51 PM, Michael Hanz <aaf-radio-1 at aafradio.org>
wrote:

> On 2/23/2018 4:28 PM, Roy Morgan wrote:
>
> Am I right in assuming that these things (the Ebay frequency converters)
> preceded the APR-4 and APR-4Y?
>
>
> Slightly (mid 1943 versus early 1944), but definitely not the APR-4
> predecessors mentioned below, which were all derived from the General Radio
> P-540 microwave receiver.
>
> THE APR-4's were in use in the 50's into the 60's I would guess.
> I have where I am an APR-4Y (which runs on 400 - 800 cycles) but I think
> no plug-ins.
> Elsewhere I do have some plug-ins for this thing.  I may have to lash up a
> big audio amplifier to run it.
>
>
> If you have a hefty 28v power supply, you might look for 400~ aircraft
> inverters.  Occasionally you will find one for a reasonable price.  The
> APR-4 takes about 110 watts of 400~ power.  I have found them at hamfests
> for $5 to $10.
>
> These things are interesting to me because they originated from a General
> Radio device meant to be used with slotted lines and the like that produced
> an "IF" frequency of 30 mc.  It *may* have been an MIT Rad Lab project to
> upgrade the GR thing.
>
>
> Yes to both subjects you raised.  Dr. Alfred Price, for his Doctoral
> Thesis in 1985, documented an interview he had with Dr. Don Sinclair:
>
> "At about this time [circa late 1940] Dr. Don Sinclair, a Canadian
> working with
> the General Radio Company at Cambridge, Massachusetts, began
> work on the receiver portion cf a field strength measuring set
> intended to cover the band 100 to 3,000 MHz. To achieve the required
> broad tuning range, the receiver used the novel ' butterfly' tuning
> device which Sinclair himself had invented. It soon became clear that
> the unusual receiver might be suitable for a role quite different from
> that for which it had originally been intended, however, and in July
> 1941 the Radiation Laboratory placed an order with General Radio
> for prototypes of an intercept equipment based on Sinclair's
> receiver. The device, which received the General Radio prototype
> designation P-540, was to become the first purpose-built US radar
> intercept receiver. During tests the P-540 continued to show promise
> and the Army Signal Corps placed an order for a hundred receivers
> of this type, now designated the SCR-587, with the Philco Corporation."
>
> The SCR-587 was also nomenclatured by the Navy as the "ARC" (think ARA,
> ARB, ARD...etc.), and then quickly, the "ARC-1", with some minor (Navy)
> improvements.  By then, we were into 1943 and it was obvious that the 587
> and ARC-1 needed improvement, especially in the tuning area, which did
> *not* have single knob tuning.  It was like tuning an early superhet
> receiver, with separate oscillator and RF amplifier dials.  The APR-1 and
> APR-4 were the result of that need, but I would not call the APR-4 an
> upgrade from the APR-1 - full scale production came about the same time in
> early 1944 for both - the APR-1 driven by Navy requirements, and the APR-4
> driven by USAAF specifications.  There were some IF step attenuation
> capabilities on the APR-4 that proved useful in the long run, so the APR-1
> became another piece of flotsam in the sea of countermeasures receivers
> that became obsolete.  The APR-4 was re-nomenclatured again in the
> AN/ALR-5, this time with the CV-253/ALR tuning head, which covered
> 38-1000MHz in four bands and greatly improved sensitivity, and the 400Hz
> powered APR-4Y being the only changes,.  The other two APR-4 tuning units
> that covered up to 4GHz still worked in the mainframe.
>
> What is lost in all this summary was the fever of research and rapid
> improvements in the hardware, pretty much on a monthly basis.  Talk about a
> release version documentation nightmare!
>
>           73,
>  - Mike  KC4TOS
>
>
>
>
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