QRP Operation with the
MFJ-9020 / MFJ-9040 revisited
This summer I wanted to take some ham radio gear on
holiday, I suddenly remembered my MFJ Transceivers, unused for several years so
rather than buying new equipment I checked to see if they still worked
My MFJ-9040 worked strait away, no problems but the MFJ-9020 seemed to have an 'intermittent ' fault where it would, after a while reduce its volume / sensitivity. Also it would not go into transmit mode.
I found that R23 had a dry joint one one end which meant the transmitter could not be keyed I re soldered it and transmission was restored
For the reception problem I measured the voltage at TP-2, it was not correct so adjusted 'REG' pot for 10 volts
Then measured on TP-1 also not correct (so without the ant connected) I adjusted the 'AGC' pot for 4.3 volts and the receiver then worked correctly.
If you buy a second hand unit it might be worth while doing these simple checks if things seem not to work as they should . I used the transceivers with the MFJ-971 which is a nice ATU for portable use. You may find new units somewhere, but I'm not sure it would make economic sense ( maybe a Xiegu G106 would be a better choice) If you can buy a second hand unit it hopefully will not be to much effort to get it working again, my MFJ-9020 had not been used for 7 or 8 years and was not to much trouble to get working again. I managed to work a VK4 station from Spain with it. ( *The G106 does not appear to have a headphone socket * )
The ‘REG’ pot is the one on the left and the
‘AGC’ the one on the right – consult the serviced manual and only adjust if you
actually have the afore mentioned problems, do not adjust anything else, and
definitely do not adjust the ferrite slugs in the transformers because you risk
putting the calibration etc beyond the stage where you can recover things i.e.
you have a dead transceiver now. If you still have a similiar problem then look
at the QSK pot and see if that has been incorrectly adjusted. The above
picture shows the two optional PCB’s the
one to the left is the 'electronic keyer' unit and the one to the right is the
Audio band pass unit, which really does make a difference.
FRG7 COMMUNICATION RECEIVER
I found my old FRG7 receiver in the attic and thought
I would check to see if it still worked after about 5 years laying there neglected.
It came to life immediately and after about an hour to let it settle down and
see if there were any issues with it, I tuned it to the H.F Acars
station at Shannon on 8.942 MHz and checked the stability ( hfdl needs to be
tuned to within about 100 Hz to decode
correctly ) and to my surprise it was still stable and able to decode the
signals without having to continually retune the receiver.
These receivers can still be found for sale despite their age and seem to go on and on
without problems, you need to buy one that has not had any silly modifications
done to it or preferable none at all. I did modify mine years ago and put a
different filter in it which as I remember was easily done and made the
receiver better on SSB and CW, I used the receiver for years off and on with a homemade
14 MHz transmitter with about 100 watts output ( two old 807 valves in the pa )
and had successful contacts all over the world, even working the Christmas
island expedition many many years ago.