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bitx40 v3 cw mods

dave
 

starting from the bottom here my bitx 40 does not have a digital dislay and at the minute i do not want one i would hoever like to get it onto cw  any ideas most welcome  dave c gw0nvf

Jim WB2LHP in MI
 

Download Allard's v1.29 firmware for the BitX40...In the body of the .ZIP file there are schematics and descriptions for his CW mods...That will give you an idea of what is involved for CW operation...You could do it with a manual T/R switching arrangement without the Raduino or other controller but you would have to determine how best to implement it...Mods I think you would have to implement are Manual PTT (TX) and CW Carrier (KEY) ...You would have to come up with your own sidetone arrangement unless you have an external keyer that provides it...All in all it shouldn't be that difficult...Jim WB2LHP

On Thu, Jan 23, 2020 at 11:21 AM dave <dgclifford@...> wrote:
starting from the bottom here my bitx 40 does not have a digital dislay and at the minute i do not want one i would hoever like to get it onto cw  any ideas most welcome  dave c gw0nvf

Jim WB2LHP in MI
 

Also, the CW Carrier (KEY) signal would have to go to +5 volts and the PTT (TX) signal to ground...

On Thu, Jan 23, 2020 at 11:21 AM dave <dgclifford@...> wrote:
starting from the bottom here my bitx 40 does not have a digital dislay and at the minute i do not want one i would hoever like to get it onto cw  any ideas most welcome  dave c gw0nvf

Don, ND6T
 

Dave,

Not anything good. For one, it drifts like nobody's business. For another, about the only way to make it transmit CW is to put a tone into the transmit audio instead of the microphone. That results in a bunch of nasties being transmitted. Suppressed carrier remains, the suppressed sideband tone, and several intermod spurs within the passband. Sure, they are down 20 dB or so but folks nearby won't be pleased. You could always use just the receiver and a separate transmitter. Or you could build another, separate VFO in there, mute the original transmitted signal back near the balanced mixer, and use the new VFO signal as a source. But why? Easier to spend ten quid and digitize it, in my opinion. For what that's worth.
73,
Don

Don, ND6T
 

Yes! The unbalanced first mixer works! But don't forget to move the VFO off frequency by an offset difference (like 700 Hz). That could be accomplished by another voltage to the tuning varactor diode, possibly from a divider from the TX voltage bus. Still, don't forget to mute the transmit audio signal.

Jim WB2LHP in MI
 

Don's right...It probably can be done but why would you?...Better to get all the advantages and automation provided by a Raduino or similar controller/VFO...There are several of them out there...However you can usually find a BitX40 V3 board set used for around $50 US...Just wire it up and go...Unless you just really want to tinker this would be the best way to go...I like the BitX40 a lot...It's a fine radio...Jim WB2LHP

On Thu, Jan 23, 2020 at 11:52 AM Don, ND6T via Groups.Io <nd6t_6=yahoo.com@groups.io> wrote:
Dave,

Not anything good. For one, it drifts like nobody's business. For another, about the only way to make it transmit CW is to put a tone into the transmit audio instead of the microphone. That results in a bunch of nasties being transmitted. Suppressed carrier remains, the suppressed sideband tone, and several intermod spurs within the passband. Sure, they are down 20 dB or so but folks nearby won't be pleased. You could always use just the receiver and a separate transmitter. Or you could build another, separate VFO in there, mute the original transmitted signal back near the balanced mixer, and use the new VFO signal as a source. But why? Easier to spend ten quid and digitize it, in my opinion. For what that's worth.
73,
Don