[Milsurplus] LM practical use

[howard holden]

I bought an LM-18 with a book at a hamfest, then swapped it with the NJ Naval Museum (USS Ling SS-297) so they’d have one WITH a book. I then took the one without a book, and made my own cal chart for all freqs in one Kc steps from 3500 to 3600 – I don’t do AM but the same idea would apply – in which I kept the corrector control at mid-point. I recorded the interpolation scale readings for each one KC step. For mine I got 3480.0 to 3687.4. Each one Kc step required a 2.0 or 2.1 step on the interpolation scale. This very small change in step to step enables me to easily interpolate readings down to about 50 cycles with pretty good accuracy. And having the interpolation scaler readings enables me to accurately calibrate the meter with the internal crystal.

73, Howie WB2AWQ

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From: CL in NC via Milsurplus<mailto:milsurplus at mailman.qth.net>
Sent: Wednesday, June 10, 2020 6:48 AM
To: Milsurplus<mailto:milsurplus at mailman.qth.net>
Subject: [Milsurplus] LM practical use

When I first got my BC375 up and running several years ago, thought it would be fun to do SKN on New Years.  I was on 160 meters, receiving with a BC348, heard a nice CQ and thought I would answer him.  Then it dawned on me I had no way to zero beat the BC375 to his signal with a BC348 that was wired to the 375 control relay and  fully muted when the 375 was transmitting. I could have fired up another receiver, hunted for the the CQ'er, keyed the 375 into a dummy load and walked it down to the freq, but used the LM instead.  Of course, by the time I got the LM going, that CQ caller was long gone, and I never made any SKN contacts with it, but I did practice zeroing techniques with the LM, 348, and 375 and have gotten pretty good at it now.  As a side note, I built an outboard  power supply for the LM with a one tube audio amp and speaker,  and plug that into the LM phone jack so I can hear the transmit zero.  Thought about a mute bypass switch for the 348, but this is more fu
 n.

I had one LM without a book, I tried that program that is around for making your own book, but never got it to work.  Instead, I wrote down all my favorite freqs, and using another book to give me ball park dial numbers to use, made a chart of freq. counter vs dial numbers so I knew where I was.

Charlie, W4MEC in NC
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