[Milsurplus] AN/APR-4 and SPA-1

[Mike Hanz]

J Forster wrote:

>Has anyone played with the combination of the AN/APR-4 Sweeping
>Receiver  and the SPA-1 Radar Pulse Analyzer ? It seems like an
>interesting combination of a pulse rate meter and scope.
>

Yup.  The SPA-1 was the "shipboard" version of the AN/APA-6 that I have 
on my countermeasures pages - 
http://aafradio.org/countermeasures/index.htm, under the surveillance 
and analysis subpage.  The only difference appears to be a steel case 
vice the aluminum one for the APA-6, as well as a heavier shock mount.  
It was a gapfiller, frankly - a small step up from the typical 1930s 3" 
lab oscilloscope used in early 1942 
(http://aafradio.org/flightdeck/early.htm), and required the same 
Hewlett-Packard sine wave oscillator to be useful in determining pulse 
repetition rates and durations.  It isn't a complete set without the 
O-10/APA-6.  The meter was notoriously unreliable because QRN tends to 
make it go bonkers, thus the dependence on the HP oscillator for decent 
pulse characterization.

>It should clearly see something like the ASB series radars and the
>AN/APN-2 Rebecca, but will it also see things like the AN/APN-1 Radio
>Altimeter?
>

It portrays any signal obtained from the wideband video (detector) 
output of any of the surveillance receivers of the time.  The bandwidth 
is about 2MHz. 

>Does anyone have any doc on the SPA-1 ? The internet seems to be largely
>silent about it, except for a pic here:
>http://www.maritime.org/radio-rcm.htm
>

August Link has a manual on auction at the moment 
(http://cgi.ebay.com/_W0QQitemZ300164726825), though an excerpt is on 
the documents page of aafradio.org.

73,
Mike de KC4TOS