Regular reports of my grabber activity and that of others, plus information on QRSS software, hardware and technique that comes my way

Wednesday, July 4, 2012


Here is another DDS-based MEPT for QRSS work which produces ~ 1W output on 160 thru 20m and with a different amp will go on up to 10m.  Hopefully it will provide some ideas.

Rick, NU7Z, built a MEPT similar to mine which is also based on the N3ZI DDS2 vfo.  He even used the all-band LPF from a defunct Kenwood xcvr which saves a lot of work, as well as the 5W amp kit from W8DIZ.  Even so there is much to be done to get a finished rig.

The output of the DDS2 is quite low, ~0.25V p-p into 1000 Ohm load, so needs a buffer amp to bring it up to 2.5 p-p V into a 50 Ohm load to drive an amplifier such as this one from W8DIZ.

Here is a picture of the guts of Rick's mept:

Here is the front panel:

You can look at my version from an earlier post here.  The main differece between mine and his is that I use the program QRS to key the fsk pin of the DDS2 via the computer's RS232 port and Rick uses an onboard keyer....I'm sure the one in the QRP Labs Mept's will work FB.

I should point out another source of MEPT circuits and rigs which have been developed by Dave, WA5DJJ, out in New Mexico.  His designs go from the Model 1 crystal tx, which I copied for my first mept, up thru his all-band DDS based rig which he uses today on all bands.

One thing for sure...once you have a DDS rig working you never have to search for crystals again.

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