In message , rickman
writes
On 10/16/2015 6:53 AM, Brian Howie wrote:
In message , rickman writes

I've a 5 foot Octagonal loop for MF. The shield is copper water pipe,
with a gap , 7 turns inside plus a coupling winding. It does a good job
eliminating local noise (mostly ASDL hash from the phone lines) compared
with a vertical. However the capacitance between the shield and turns
seems to load it quite a bit meaning I can't get the tuning range I'd
like.

I assume there is nothing to space the wires from the pipe other than
the insulation. Maybe you could use wire with thicker insulation? Or
if you are using straight pipe, could you use a fabricated spacer at
the corners? I guess that might be hard to assemble with soldering the
joints.

No just the insulation. It was hard enough to thread it without spacers .

I should have stuck to the original design that used plastic pipe with
aluminium foil stuck to the outside

I saw one receiving antenna made from a bicycle rim. Easy to thread.
I assume you only use this for receiving?


Neat idea . I used a hula hoop for a previous version. Yes receive only.
I wanted to cover 136kHz and 472Khz . In theory it should have done it ,
but for the capacitance. I had to take a lot of turns off, which also
meant the coupling winding loaded the loop a lot more, reducing the Q
factor.

Brian
--
Brian Howie