[Milsurplus] Opinions on ARR-7

[Ray Fantini]

With all this discussion of counter measurements receivers I would propose that the Hallicrafters designed receivers were a product line that although they filled a need was a product line that went nowhere. The entire ARR family was obsolete and surplus by the end of the war and the future was the ARP-4 series of receivers. Think the APR-4 and APR-1 was introduced around the same time as the Hallicrafters stuff and although the APR will not cover the low frequencies that the ARR-7 did all the ARR stuff disappeared after the war but the APR-4 went on well into the cold war and the APR-4Y was in service into the late sixties and early seventies. Although not popular with the Ham community due to the relatively low sensitivity and wide bandwidth I would propose that the APR-4 series of receivers may be one of the longest used and best counter measure receivers built. And was the choice receiver until replaced by the early Watkins Johnson/ CEI equipment in the sixties. But this is all just speculation on my part.

-----Original Message-----
From: milsurplus-bounces at mailman.qth.net [mailto:milsurplus-bounces at mailman.qth.net] On Behalf Of Mike Hanz
Sent: Monday, August 27, 2012 5:03 PM
To: jfor at quikus.com
Cc: ARC5 at mailman.QTH.net; Vintage-Military-RADAR at yahoogroups.com; Milsurplus at mailman.QTH.net
Subject: Re: [Milsurplus] [ARC5] Opinions on ARR-7

Well, the receiver doesn't appear to have been desensitized all that much.  The ARR-7 manual claims "better than 10uV at a 10dB S/N ratio on all bands with a 50mW output."  That contrasts with that original SX-28 spec of "2mV for bands 1-5 and 4mV for band 6", and the SX-28A claim of "6-20uV" (admittedly with 500mW output) over the receiver's entire range. No S/N figure is stated for the SX-28 versions.

I'm not sure the ARR-7 was ever used for radar work.  The VHF ARR-5 was indeed used for radar collection efforts, at least at the first part of the war when German and Japanese radars were comparatively low frequency in operation, but that changed rapidly with the Germans, and even the Japanese eventually migrated to higher radar frequencies above the range of the ARR-5.  The compendium "Radio Countermeasures", one of the classified NDRC reports issued following the war, has it listed tentatively under the category of radio communications countermeasures, which is consistent with your ELINT proposition, but more focused on identifying signals that could be subsequently jammed by airborne jammers down in the passband of the receiver.  "If you can't hear 'em, 
you can't jam 'em..." :-)   The operational history didn't seem too 
successful in using airborne platforms for radio communications jamming, however.  It appears that ground intercept and jamming was more effective, probably because it's pretty hard to get a decent sized antenna to behave in flight...  The lower frequency airborne jamming efforts quickly settled into the frequencies above 30MHz, primarily to counter missile guidance systems.

73,
Mike