Re: [IRCA] Antenna experiment

["Craig Healy" <bubba@xxxxxxxxxxxxxxxxxxxx>]

>> I made a new loop antenna today, and initial results are very
encouraging.
>
> And then you'll build one for those of us on the list who are technically
> challenged and ship it to us at a nominal cost...

Heh!  If you can solder plumbing pipe, you can build this.

I had a chance to do a bit more testing.  I wound five turns of #16 wire
tight through a ferrite toroid.  The toroid is the FT-240 size (2 1/2") of
unknown composition.  A SO-238 was soldered to it.  It was then slipped over
the copper pipe. I had 50' of RG-8 cable which I used to hook it to the
homemade tuner I mentioned in my last message.  Then, a few feet of smaller
coax to the truck radio.  It's a Blaupunkt MP74 which is a good radio.

At the moment, the copper loop is leaning against a fence next to my tower.
Hardly optimum as one side is sitting on wet ground and it's a number of
degrees off vertical.  I tuned through from 530 to 1710, and had good
signals on every frequency not blocked by a local.  Far better than the whip
antenna on the truck..  Some directionality was noted.  Boston stations were
weaker as they were broadside to the way the loop was aimed.  Signal
strength was almost too strong, especially on the low end of the band.
There is no amplifier, all components are passive.

Having a loop which could potentially be turned with a rotor, and tuned at
the receiver end is something I've been looking for.  I imagine this would
work exceptionally well with the PalStar MW550P tuner, if I had one.

Tomorrow in the daylight I'll solder up the last connection, now that the
toroid is on there.  I'll get some rope and hang the thing from some high
point in the yard.  Then I'll bring out the R8B and see just what it can do
on nulling.  At 10' to a side, it's fairly unwieldy.  If I build a permanent
one, I'll use bigger tubing.  Less floppy when moving it.  Maybe 1.25"
copper..

All in all, this was a heck of a lot less work to build than the usual box
or spiral loop.  If it continues to work like the initial crude tests show,
it's going to be a useful piece.

After I have a chance to do some further tests, I'll make a duplicate.  Then
I will mount them at 90° angles and connect them to my MFJ phasor.  It may
not even need to be rotated.  With one aimed north-south and the other
east-west, a decent null ought to be possible around the compass just by
phasing.

Sorry if this is rambling a bit.  I'm sorta thinking out loud as I write.

Craig Healy
Providence, RI


_______________________________________________
IRCA mailing list
IRCA@xxxxxxxxxxxxxxxx
http://dallas.hard-core-dx.com/mailman/listinfo/irca

Opinions expressed in messages on this mailing list are those of the original contributors and do not necessarily reflect the opinion of the IRCA, its editors, publishing staff, or officers

For more information: http://www.ircaonline.org

To Post a message: irca@xxxxxxxxxxxxxxxx