One more iron in the fire: Kaar Marine Transmitter/Receiver restoration

[k4kyv]

There was a write-up in the latest AWA Journal (Antique Wireless Association Bulletin) on the circa 1945 Kaar 25E marine communications receiver.  It covers the broadcast band and 1600 kHz-5000 kHz in two bands continuous coverage, plus provisions for 5 crystal controlled fixed channels.

I picked up a complete transmitter/receiver/power unit several years ago at a hamfest, with the hope of restoring it one of these days and putting it on the air.  I have the 25E receiver and Series 96 transmitter plus power unit, all mounted in a rack cabinet.  Reading the article fired me up to restore mine and put it on the air.

The receiver is a very conventional single-conversion superhet with 455 kc i.f. and one rf stage.  The transmitter is 5-channel crystal control and uses a pair of 807's in the final modulated by another pair.  It is in good shape, without much corrosion, so I think I could get it running fairly easily.  The air-core inductors in the transmitter have fallen apart as the plastic strips have deteriorated, as is typically the case with B&W Miniductor and similar air core coils, but I believe they are restorable.

The transmitter output network appears to be designed for a random length
end fed wire antenna, with fixed air trimmer capacitors and taps selected by
the channel switch so that the transmitter would be pre-tuned to each
crystal frequency, and the operator would merely switch to a channel and all
stages in the transmitter would automatically be tuned to frequency, kind of
like a CB rig.  It even comes with a notice on the front panel that adjustments of
the transmitter by unlicensed persons would be a violation of FCC rules.

I will probably have to build an outboard antenna tuning unit to make it
work with my present antenna system, as I prefer NOT to rip out the original
transmitter tank circuit and convert to a more conventional amateur radio style output circuit as used in tube-type ham rigs.

I downloaded the schematic for the receiver from the AWA website, and the author says he can get me the rest of the manual.  I plan to contact another person to see if he has a manual and/or schematic for the transmitter.

I'd be curious to know if anyone has ever heard of the rig.  The author of the AWA article says there are only four of the receivers known to exist, so I suppose mine makes five.

[Opcom]

You are lucky! what a find! I've heard of it but never seen one.
I had to pass on a Loraine last time I was in Chicago. Same concept, I don't know if the guy that bought it got it working or not.

[Tom W2ILA]

Donn,
I'm not familiar with the Karr but it sounds like the output is typical for that era of marine rigs (right up through the 60's).  The antennas were usually 35' whips with a few feet of additional GTO as the lead-in.  Keel bolts were the counterpoise.

My Simpson 55, circa 1968, is crystaled for 1885, 1945 and 3885.  The rig loaded fine into 50 ohms on all channels.  You'll probably find the same because all of these things seem to have built to be flexible on installation.

Tom