Kaar "Standard Dummy Antenna"??

[Steve Harrison]

Finally got the time (and put aside the procrastination last night) to fire
up my newly-acquired Kaar KE-23A multiband receiver, obtained from Peter
Brickley (excellent packing, shipping-across-country, and as-advertised
condition; thanks, Peter!). This one was built in Palo Alto on Feb. 22,
1945 according to the original factory "QA" tag that I found inside.

As with my very first KE-23A back in 1964, this one seemed as deaf as a
doorknob...so I thought. But I have a later manual for the KE-23AT and the
KE-23A (dated Dec. 1949) which has complete alignment instructions; and
that, after a lil thought, allowed me to tweak the machine nicely. Even the
14-42 MHz D band seems to have reasonable sensitivity (after replacement of
a broken and missing antenna coil padding capacitor), and I was able to
trim and pad the 6K8 local oscillator nicely to the right spots on the
dial; the tracking is right on.

Need to go find some model airplane cement to reseal the coils, though. The
machine seemed to be somewhat outta tune; but now, I can actually hear the
BC band full of signals, and the other bands yield lightning crashes. Still
need to figure out whether the low atmospheric noise level is normal, which
is probably a function of my crummy HF antenna(s) (I have nothing else to
use but the feedline shields of my 432 or 1296 yagis through a tuner!).
Still can't hear WWV on any freq over the computer noise, but that's normal
for my antler/QTH. Back in 1964, I was barely outta grammar school so had
no idea what I was really doing as I tweaked all the neat little trimmer
caps and transformers until they squeaked. Last night, the tweaking became
very critical to get the last microvolts of sensitivity; no wonder I never
got that poor first receiver working right wheb I was an impatient kid!

And I found something having apparently drifted way off in the BFO, which
wouldn't oscillate at first. Finally had to replace a shunt 100 mmF ceramic
cap with a mica trimmer to get it to work. Having an HP 8640B to use as a
stable signal source sure reduces alignment uncertainty! The BFO isn't very
stable for a 455 kHz oscillator; I will have to think about that a bit, it
could be due to slightly-varying power line voltage. I don't want to modify
this thing substantially, just be able to use it for casual listening. But
I DO want it working as well as it must have when it came from the factory.

The instructions called for a "standard dummy antenna" to feed the signal
generator to the receiver. Not knowing any better and not finding any info
on this circuit either in the manual or in a couple of pre-war and
war-vintage ARRL HBs, I finally settled on a series 15 pF disc ceramic to
the "hot" antenna input terminal with the other antenna terminal grounded
as for a doublet. I figured the small cap would avoid any detuning effects,
resonances, etc. A better solution would probably be to wind a broadband
300-ohm to 50-ohm impedance-matching transformer; the manual states that
the receiver was designed for 400-ohm doublets connected to the two antler
terminals, or for long wires with one terminal grounded.

So, the question: what was the circuit of the "standard dummy antenna"?
Something like a series cap or resistor with a shunt 300 ohm resistor??

This machine was designed to operate from 117 VAC, and my line voltage is a
mite bit high at 124. But according to the manual, that should be
acceptable. However, after a couple of hours, the power transformer was
hot, not merely warm. Since the receiver jumpers the filaments and B+ to
the rear panel through an octal plug (for use with MOBILE supplies, if you
can picture a rack-mount receiver in one of today's cars), I think I'll
build an external PS (complete with VR tubes) to let that old transformer
rest. The audio output XFMR has already been replaced with a non-original
Triad and was merely warm, about right, it felt. All the original bypass
and electrolytics had already been replaced except one section of the
original dual-section can electrolytic. I happen to have a replacement if I
want to get ambitious, so that's not a problem.

Another question: the RF amp is a 6SK7. If I remember right, the 6SH7 could
also be used and was hotter, sort of like the difference between the 6AU6
and 6SH6 in Heath SB-series receiver front ends? Will hafta look through my
tube boxes...otherwise, I can just bite the bullet and use a (GASP!!
SACRILEGE!!) broadband solid-state low-noise MMIC amplifier as a
preamplifier until I build a Q-multiplier from the HB. Anyone have a
suggestion for such? Heck's bells: I could combine the Q-multiplier with
the new regulated power supply in the same box...

Finally, despite words and advice from Walt, K1RTS, that he couldn't find
any reference to an accompanying transmitter to this receiver (and my
manual also makes no reference to a Kaar transmitter), I wonder whether
anyone else knows/remembers whether Kaar ever did make an HF transmitter? I
believe Kaar, at least later, apparently specialized in low-VHF band mobile
and base station equipment up through at least the early 1960's and thought
that I'd seen some sort of large rack-mounted transmitter at a swapmeet once.

73, Steve Ko0U/1

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