2023-01-22

PM2B and Documentation, Mini Project #3 Goes on Hold.

Having seen the receiver working, if not very sensitive, and the transmitter part with no output at all,

I am putting the mini project on hold.

First of all because I have no proper documentation, no service manual, no circuit diagram and not even a user manual. If the set would have been in proper working order I would have found out how to use it, no problem.

Second, the transceiver is so old and primitive that I find the operation too cumbersome to my kind of CW operation:

1) The receiver preselector has to be readjusted when tuning through the band, and especially if changing band.

2) The transmitter needs 2 extra adjustments after tuning over the band, or at band switching.

3) The VFO tuning ranges are too large for my use. For CW I use about 100kHz at the bottom of each band. This model covers 3.5-4.0 MHz, 7.0-7.4 MHz and 14.0-14.8MHz. On 20m the useful tuning range of 100kHz takes up very little space on the dial.

4) I have not found any way of making an offset between receive and transmit frequencies, meaning that tuning to a proper receive tone offsets the transmitter frequency. Not practical on crowded bands. Modification necessary for this alone.

5) The audio output can only drive high impedance headphones (>1kOhm). Not very practical, as I do not have those any more, though I could use a piezoelectric earphone for tests, but I would not use it regularly. In order to use the set with ordinary modern headphones or earphones, or a speaker an additional audio amplifier is necessary. This already means that  another modification is needed in any case.

For these reasons I do not find the time to restore this radio to its original state a good use of my time.

So what to do now?

Modifications are needed in any case, if I should want to use the transceiver

The casing, with some shielding at the sides will still be useful. I can build my (partly) own construction in there, and make myself a multiband CW transceiver. This is no longer a mini project, but a much larger one.

I may try to find a replacement for the PA transistor, maybe the driver if necessary, so the transmitter can be shown as operational, but that is all. Apart from that, the PM2B mini project is on hold.

I do not have any lack of mini- or smaller projects, so life goes on.


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