Mate For The Mighty Midget...
gswynar at DURHAM.NET
Thu Aug 24 07:06:32 EDT 2000
Just yesterday I elected to blow the dust off my little version of the "...M.F.T.M.M." receiver, & fire it up just to see how it held up in storage for the past couple of years...
After a bit of tweaking of the IF coils---and getting myself re-acquainted with the different control functions (funny how quickly you forget!)---I amazed myself again at just how effective a little rig this is...
I made several worthwhile several mods to the original circuit, which I'd like to share with others:
-MIne covers both 160- and the bottom 400-KHz of 80-meters.
-I added an extra stage of IF amplication (6BA6).
-I made the first IF stage regenerative (what a great way to secure "free" IF gain! Just like having a built-in Q-multiplier, only without the extra tube & L/C components).
-I "...cheapened" the cost of things by NOT employing the crystal filter (selectivity is fine with the regenerative IF).
Some things I'd like to do over again, if I had the chance...? Just one: I'd increase the spacing between the link coils & the main coils in the RF & mixer stages. I think mine are a bit too close, resulting in too tight coupling, resulting in an overly B-R-O-A-D front end response (especially noticeable on 160 meters: I can listen to AM on 1888-KHz and strong CW signals at the bottom of the band during contests, at the same time!).
This was partially remedied by the inclusion of a double-tuned, adjutable circuit, ahead of the RF amplifier (alas, yet another control to fiddle with!).
These things sure are a ball to play with (the FT-980 & IC-751A sit idly by, while my XYL scratches her head in wonderment)...Sure would be nice to know if others are still building this rig, & how they might be "...hot rodding" their versions of this classic...
~73~ Eddy VE3CUI - VE3XZ
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