At 12:41 pm ((PDT)) Sun Jun 17, 2007, ewdawso_1 wrote:
In the photo section under passin_thru2 ther is a loop antenna, 3rd
and 4th photo that shows an octagon loop antenna.
Seems to be these two:
(I hope those links hold up ;-)
In the photo it shows a coil, just looks like heavy gauge wire coiled,
that is between the antenna and the variable capacitor. Does anyone
know what this loop is for or what it could possibly be used for?
This was asked about and partially answered in the thread
"i posted 2 pictures of a loop i found surfing, what is the little coil ?"
on Nov 16, 2006, messages 2867 and 2868:
The whole tuned circuit seems to be made out of heavy-duty
parts, so I suspect it is a small transmitting loop, though the
capacitor appears to be air-spaced and hence not able to
withstand a very high peak voltage, so it must be QRP.
The coil at the base is clearly in series with the loop antenna,
so it lowers the resonant frequency compared with the loop
and capacitor alone. However, contrary to the suggestion that
the alligator clip is for varying the inductance, I believe it is
at the end of what appears to be a coaxial cable which enters
from the lower right rear, which means the small coil is a
matching/loading coil.
To me, this makes it seem more likely that this is a transmitting
antenna, since it is usually not necessary to match a receiving
loop with any exactitude.
As to what frequency it's on, I suppose one could estimate the
dimensions from clues in the photographs and guess the value
of the capacitor, but at a glance I would say it looks a bit small
for MW BCB and the capacitor is nearly fully open - and what
frequencies may one legally transmit on anyway?
So I would guess that it is for 1.8MHz or 3.5MHz - it doesn't
really matter, because if you want to copy it, it is fairly easy
to start from scratch with the basic mechanical idea using
standard loop and coil design programs.
Regards, LenW
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