开云体育

Hi all,

A while back at a hamfest I picked up a mystery radio being sold by a guy selling items from an SK's estate. He didn't know what it was at all, so I got a good price on it. Bringing it home, I found out that it's a BitX40 v3.

The builder didn't label any of the buttons or knobs on the radio, so I had to figure those out myself. Got it all sorted out except for one switch that goes to another smaller board under the main PC board, but that'll be a question for another time. There apparently have been multiple mods done by the original builder to the radio, but so far I haven't been able to reverse engineer what's been done to it. It does work great and has great receive audio as well as good transmit audio.

Right now, the things I want to figure out is how much power output the radio should have. All other Bitx's I've had are 10W output, but this one seems to only be 5W with one IRF510 final. If 5W is what I can expect out of this radio, then fine. I was making contacts on a net last night.

The radio was built without having a hookup for a CW key. I'd like to install a CW jack so I can operate CW with it. I did find a schematic but can't seem to find where to hook up a key to the circuit.

Any help appreciated.

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Tom Sevart N2UHC


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Some radios can send CW with a straight key if you select CW and then key the PTT line.

Gerry Sherman

On 4/12/2025 10:58, Gerald Sherman via groups.io wrote:

Some radios can send CW with a straight key if you select CW and then key the PTT line.

I put it into CW mode and keyed the mic, but it just transmitted in LSB.


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Tom Sevart N2UHC

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On 4/13/2025 04:25, Vic WA4THR via groups.io wrote:

If you have the option to select CW, the radio may have been updated with Munter's fantastic BitX40 software. The attached manual shows the hardware mods needed to operate CW.
=VIc=
_._,_._,_

OK, that may explain what this mess of components soldered together with a couple of unconnected wires is (photo attached). I've circled the bundle, which looks like a couple of caps and resistors, connected to the A1 dit pin. Now I'm wondering if the unconnected wires are for the dit & dah sides of a paddle.

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Tom Sevart N2UHC

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OK, I made a little bit of headway. I learned that holding the menu button down makes it go into a settings routine where I was able to change some of the parameters. I didn't know how to get into the settings or if they were available until now.

I turned on the CW capacitive paddles, and just touching the two unconnected wires I was able to make the radio go into xmit mode, but it was not sending any CW and there was no side tone. Looks like I need to connect pin 15 of connector D3 to C107 through a 4.7k resistor. Apparently whoever built this didn't care to use CW.

I also quickly learned that by turning the semi-QSK on, the radio will not switch back into SSB mode until that's turned back off. But without the semi-QSK turned on, it won't go into xmit in CW mode. Not sure if this will be fixed when I make the connection, but at least it's a step in the right direction.

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Tom Sevart N2UHC

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On 4/13/2025 11:04, Doug W via groups.io wrote:

Courtesy of archive.org, these might help.
index.php/2017/11/23/wiring-up-the-bitx40/ < web/20230321095920/ wiring-up-the-bitx40/>
index.php/2017/11/23/bitx40-circuit-description/ < web.archive.org/web/20220119131525/ index.php/2017/11/23/bitx40-circuit-description/>
Some of the wiring mods may be for PE1NWL amazing firmware.

_._,_._,_

Looks like the original builder started but didn't finish the CW mods. I went through and finished all the necessary mods to get the radio to work in CW. I installed a key jack and decided to just use an external keyer with the radio, since I can't seem to figure out where to change the CW speed in the menu. It is now working on CW, but it still has the quirk that the semi-QSK has to be turned on in order to activate CW xmit. This does, however, prevent me from changing the mode from CW-L or CW-U to LSB. However, I did learn just now that keying up the microphone makes the radio switch into LSB mode. Then keying the keyer automatically switches it into CW mode. Still working out all the quirks of this radio. But at least now I can get on CW with it.


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Tom Sevart N2UHC

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