MFJ 40/80 dual bander

G0DZB

Member #84
Award Moderator
A few weeks ago I snaped up a second hand MFJ-1792 40m/80m vertical advertised by a local ham.

Although it had been put up it is in good condition with no bits missing and even two sets of guy wires provided.

This is a "full sized" antenna ! It's a full sized 1/4 wave vertical on 40m and on 80m it has a loading coil and capacity hat at the top to make it resonant.

I don't have anywhere to put it up at home so I bought it with the intent of using it for some /P operation. It's not ideal for this as it is made from 6 sections that need bolting together, the capacity top hat needs the spokes attaching, the base mounting arrangement is a bit fiddly, and it needs a proper set of radials. But if you've got some friends to help you put it up, and you are intending to operate for a few hours before taking it down and taking it apart again, then it's worth the effort.

I put it up for the first time yesterday afternoon. I cut 8x36ft radials that just lay on the grass, and the SWR on 40m was <1.2:1 across the whole band, and on 80m (using the spokes trimmed to length by the previous owner) is was resonant at the botom of the band. I think I'll trim the spokes a little as the SWR was upto >2:1 by 3.560.

I fed it with a short length (~10m) of coax and running 10W from my KX3 worked HB0/DL/F/G on 40m. Sadly 80m was dead during the afternoon so I didn't work anyone, but the reverse beacon network showes several spots from mainland europe stations when I called CQ. The KX3's internal ATU was able to load it up on 20m as well, and I had a couple of qsos there as well.

I have some ideas on using the top loading coil and capacity hat on an old army 27ft telescopic mast which is easier to put up.

Peter G0DZB
 

M0LMK

Member #2
Full Member
Staff member
That looks impressive Peter.

I bet it would be fantastic down by the sea.
 
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