Most of the "cans" I used in the 50's had a flat metal disk diaphragm that
vibrated in the field of a pair of magnets behind it. They had a pronounced
"peak" in their audio response in the 1 to 1.5 kHz (kc/s to be
period-correct) range. 

I, too, often just laid them on the table while working around the operating
room at K6USA (Ft. Ord Army MARS station).

The R.O. on the SS Californian used to wind up his magnetic detector and
listen to traffic from his cans laying on the operating table while he fell
asleep in his bed after his shift ended for the night. They estimate it was
just a few minutes at most after his detector wound down and the signals
went quiet before the CQD/SOS started blasting out from nearby MGY (SS
Titanic). That's why she never responded.  

73 Ron AC7AC

-----Original Message-----
From: Elecraft [] On Behalf Of Fred
Sent: Wednesday, September 21, 2016 12:20 PM
Subject: Re: [Elecraft] Running stations with k3

OK, this is probably a good place to ask:

When trying to copy a weak-ish signal in noise and "other stuff" in the
50's, one of my crewmates at the coastal marine station told me to lay the
cans on the desk, face up.  It works.  I don't know why, maybe someone here
knows.  Surprisingly, I generally didn't need to turn the gain up much if at

The receiver I used most on our HF frequencies was a brand new Collins 51J4.
The military version was the R-388A.  It had 6 and 3 KHz mech filters, and a
separate, adjustable crystal filter.  Did not cover 500 Kcs which was
particularly noise and full of signals at night, however the trick worked on
those receivers too, so it wasn't just the mech filter.


Fred K6DGW
- Sparks NV DM09dn

- Northern California Contest Club
- CU in the Cal QSO Party 1-2 Oct 2016

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