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hpr2648 :: Explaining the controls on my Amateur HF Radio Part 1

I attempt to explain the controls on my Kenwood TS940S HF Amateur Radio.

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Hosted by MrX on 2018-09-26 is flagged as Explicit and is released under a CC-BY-SA license.
Amateur, Radio, Ham. 2.
The show is available on the Internet Archive at:

Listen in ogg, spx, or mp3 format. Play now:

Duration: 00:27:26

HAM radio.

A series about all things Amateur Radio/HAM Radio.

In this episode, I cover the transmit section controls.

Further info and clarification

Below I’ll cover some of the items I missed or didn’t understand when I recorded my off the cuff episode. If I miss something you may find it in the user manual link above.

Full and Semi break-in mode is used when operating in CW mode (Morse Code). In full break-in mode the radio jumps back into receive the moment the mores key is released this way you can hear if the station is trying to contact in-between each press of the key. This is very demanding on the radio as it must switch very quickly back into receive mode it can also be distracting for the operator hearing hissing noise between each dot and dash. Semi break-in mode is a bit like using VOX mode in speech the radio goes silent between each dot and dash but will return to receive after the mores key is released for a predetermined time interval.

The digital display used on the main display of the TS940S is apparently a Vacuum Fluorescent Display not the more usual LED of the time.

The TS 940S was manufactured around 1986, so unbelievably that means my wonderful radio that to me looks fairly modern is around 30 years Old! I believe this HF radio was top of the line for Kenwood back then.

The Auto and thru button is used to connect the auto tuner in line with the antenna. When AUTO is selected the radio is connected to the Auto internal tuner and then to the antenna. In THRU the radio bypasses the auto tuner and connects the radio directly to the antenna.

The Speech Compressor

During SSB operation it is desirable to increase the relative “talk power” of the transceiver by using speech processor circuitry. The speech processor control is set by using the in and out rotary control. The in control level is set by putting the meter into Comp and adjusting the in control to no more than 10 dB of compression. The out control level is set by putting the meter into ALC and adjusting the out control to ensure the meter stays within the ALC section of the meter.

IC meter position indicates the power transistor collector current

VC meter position indicates the power transistor collector voltage

Noise Blanker 1 (NB1)
For pulse type noise, such as generated by automatic ignition systems.

Noise Blanker 2 (NB2)
For long duration pulse noise, like the Russian woodpecker.


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Comment #1 posted on 2018-09-28 23:11:17 by NYbill

Thanks pal

Yea, do continue this series. I recently got my Tech license. I'll go for the General soon. Its nice to have someone explain what you might see if/when you get an actual radio. Because, walking into this cold, it just looks like a lot of buttons!

Comment #2 posted on 2018-10-03 16:05:08 by MrX

Re Thanks pas

Hi NYbill many thanks for the comment glad you liked the show, yes as you could tell from the show I didn't know what a few of the controls did, so it will indeed be bewildering to start with. I've tried to fill in some of the gaps in the show notes,

All the best


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