[ARC5] [Milsurplus] Dual Inspections (on USN DZ)

[Mike Morrow]

Mike wrote:

> I have a somewhat different opinion, Mike.  The DZ was a pretty 
> sophisticated design in the antenna area with the nested goniometer 
> loops - better than the simple loops that Bendix used, especially at 
> lower frequencies.  Remember that this receiver covered 15kHz to 
> 1,750kHz, not the smaller range of the Bendix products.

There was a small gap in coverage fron 70 to 100 kHz. :-)

One wonders why, by 1939, RCA did not design a dial calibrated directly
in frequency for the DZ.  Robert's wonderful SHIPS 242A from January
1945 lists all DZ-* units as obsolete, and the list of equipment
installed on various USN aircraft on your website that came from a
1943 USN training publication shows the DZ only on a few older patrol
craft.  OTOH, there are many photos showing the SCR-269 ADF on USN
aircraft in WWII.  It seems to me that the few positive points for
the DZ over the SCR-242 and later USAAF DF sets were not of practical
value by WWII.

>In any case, the seller obviously mistakenly linked the DZ rather
>than the ZB-2 and ZB-3 he should have said. 

I failed to notice the obvious, even though I have a ZB-3 switch unit
identical to the one shown just a few feet from me now!

I wonder if the auction unit actually has an RE-1/ARR-1 nomenclature.
Many R-1/ARR-1 units have both USN and USAAF stamps.  My aircraft manual
for the B-29A describes the use of the AN/ARR-1 with the AN/ARN-7 ADF,
and requires repositioning a control switch to the "ZB" position.  So
maybe the USAAF did use ZB-2 or ZB-3 units in the early days.

>> The USAAC's 1937 SCR-242-A (BC-310, BC-311) RDF by Bendix is a far
>> more modern design than the USN's 1939 DZ-series RDF by RCA.
>
>It was certainly more mainstream in its concept than the DZ, but 
>performance has to be defined carefully when comparing two dissimilar 
>receivers.  The performance of the BC-310 loop is pretty miserable at 
>15kHz...:-)

Yes, but I'll bet it worked well above the 150 kHz for which it was designed!

The BC-310 front panel is interesting since it essentially has the controls
that are on the BC-311 remote control box built in.  I suppose that allowed
a navigator to control from the front panel of the BC-310, while allowing
the pilots to control from the BC-311.

The Bendix BC-310-A from 1936/37 and the RCA BC-224-A from 1936/37 seem to
have been years ahead of their time, much like the ATC a few years later.
It's really remarkable what could be accomplished with clever design.  And,
I'd still like to know how GE made the GO-4, -5, and -6 in 1938 and 1938
that operated to 26.5 MHz.

> The only other thing I would add to the list would be a BC-AA-191 transmitter
> to cover the entire spectrum.  The BC-307 was really only a command type of
> transmitter from a power output perspective.  A pair of 801's in parallel
> don't go very far...

But the 801 pair in the BC-307 had to be better than the 45 pair in the
SCR-*183.  :-)

Mike / KK5F