Re: Tuned loop antenna


I would like to hear more about your spiral loop antenna, such as the wire you used, and the spacing between turns.

I also experimented with diamond weave and rook wound coils of 10-12 inches on both AM and LW. Mostly I was hoping for TA LW, but it never happened. Each coil acted differently, that is for sure. I have pretty much given up trying for TA LW on a ULR without an amplified antenna. Now I am more interested in AM BCB. - FARMERIK

P.S. - Was that a typo about the 310 being worse than the 380 regarding soft mute? I thought it was the other way around, but I can easily be confused.

--- In ultralightdx@..., Rick Robinson <w4dst@...> wrote:

Hi Nick,

If you are handy with a soldering iron, the PL-310 is very simple to
modify for external antennas. See the group files section for the
"Laurie" mod to the PL-310. The PL-380 mod is more involved but is a
better radio due to its lack of extreme soft mute and AGC issues that
the '310 has. I have modified my '310 and 2 '380s for use with external
antennas. The Si4734 will tune any antenna in the 180uH to 400uH range
with its built-in 500pf - 20pF varactor. No need to purchase bulky
tuning capacitors, it's all in the radio. I used 1/8" stereo jacks on
my PL-380s, and depending on the type of jack you use,you can keep the
internal ferrite bar in place and usable when the external antenna is
not being used.

I use a 24 inch spiral wound loop antenna with an inductance of 260uH
with my ULRs. BTW, a spiral wound loop has much sharper peaks and nulls
than ferrite bar and "box wound" loops and is much quieter than ferrite
bar antennas. However it is somewhat more difficult to construct than a
"box wound" loop and is not as easily transported as a ferrite bar.

I've been using these modified ULRs for almost a year with no problems
at all. The Si4734 is a robust chip and does an excellent job of tuning
external MW antennas without use of external capacitors.

Good DXing,

Rick W4DST

On 6/27/2011 6:47 PM, g4irx_uk wrote:

I've looked at some of the amazing ferrite rod antennas for ultralights.

Has anybody tried a tuned loop antenna in place of the ferrite rod, letting the si4734 do the tuning rather than a capacitor on the loop? I have a large hexagonal loop and I'm considering mounting the PL-380 on the loop frame itself, disconnecting the internal ferrite.


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