[Milsurplus] APN 9 and DBS Loran A sets

[boeing377 at aol.com]

  I used APN 4 and APN 9 sets on commercial fishing boats. The Navy 
shipboard APN 9 (which Wm. Donzelli says was the DBS) was highly sought 
after because it had a power xfmr that could take 60-400 hz 115 AC 
input. 400 hz power was hard to come by on boats. Rotary inverters 
(with the exception of the hard to find PE 109) took 28 VDC and most 
boats ran on 12 VDC. Linear Systems in CA made a 12 VDC to 110 VAC 400 
hz solid state inverter which sold for around $225, a lot of money back 
then. Topaz made one too. The DBS could be run on 110 VAC 60 hz which 
was easy to get using cheap 12 volt inverters made for trailers. Some 
enterprising techs rewired the suprplus Loran sets to have the 
filaments run off DC and that dramatically lowered the current rqmts 
for 400 hz. They made small two transistor inverters to supply the 
power for B+. Meshna had the cheapest APN 9 sets. A few NIB APN 9s were 
found in the UK but I never saw a US set that hadnt seen heavy mil use. 
APN 4A sets were available NIB. in the US. The APN 9 was favored 
because of its dramatically smaller size. The protruding magnifying 
visor on the APN 9 caused a few bruises in heavy weather. Nobody had 
the rubber hood which was designed to prevent this injury. A ham with 
the last name of Wagner in Sebastopol CA was the local APN 9 Guru. He 
could fix anything quick and sold sets that he recapped. My sets had 
all original caps and never had problems other than an occasional tube 
failure.m