[Milsurplus] BC375

[W2HX]

Excellent. Thanks for the info. Excited to play with it! I will be using a 28V 100AH battery paralleled with a 30A power supply to keep it charged. I read on that site that 28V makes the 1000VDC even stiffer. So I am hopefully. Thanks for the notes on the antenna.

73 Eugene


-----Original Message-----
From: milsurplus-bounces at mailman.qth.net <milsurplus-bounces at mailman.qth.net> On Behalf Of CL in NC via Milsurplus
Sent: Wednesday, February 17, 2021 5:13 PM
To: Milsurplus <milsurplus at mailman.qth.net>
Subject: [Milsurplus] BC375

I use the BC375, and I followed  "Using the BC375 Today" to the letter, and have no issues.  You must have a stiff 1000VDC supply, dynamotor is the easiest and you can run it with a 24 VDC 30amp switching supply with just one additional part added in, a 1 ohm 50 watt resistor across the contactor in the dynamotor control to reduce the start current demand.  Start the power supply, the dynamotor spools up, hit the power switch on the front of the TX the contactor pulls in and cuts out the resistor.  If you have an AC supply, hopefully it will handle the load.  The biggest problem if it is working is the modulation is FM instead of AM.  If you have a HF receiver that does FM, tune to your xmit freq and listen on FM while you talk.  If you hear nothing, fine, if it is FM'ing and your voice comes through loud in clear in the FM mode, remove the freq. chart and adjust the horizontal control sticking out from the panel, until FM is zeroed out, this will change your freq too.

I use a dipole antenna fed through a tuner.  so the 375 is feeding a 50 ohm load with a piece of coax hooked to the terminals on the side.  Note the controls on the front panel, they have letters assigned to them.  For mine on 3715KC I have the following numbers:

A-2, B-948, C-46, D-5, M-27, N-2, O-51, P-1. and that might be a starting point, you number for B will not coincide with mine for 3715 though.  You can play around with feeding an end fed wire, but you might make more contacts with a better antenna.

The manual has a very good treatise on just how the tuning circuits work and what to look for.  Don't push it to the red line on the meter, run about 50-70 watts of carrier out and it should do fine.

Charlie, W4MEC in NC
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