[Elecraft] Experiences using a portable HF loop

[David Orman]

I would agree with the portable lossy versions. Definitely not the properly
constructed versions. The loop on the left is for transmitting, and is 2"
diameter tubing. Yes, I have some weed removal due. :) Not all loops are
created equal, with minimal resistive losses and a well designed
capacitor/tuning mechanism they can be relatively efficient. This one is
quite good on 20, and better on 40 than any traditional wire antenna I
could setup with the yard and lack of trees. A halfwave dipole a halfwave
up on 40m would outperform it by 4dB or so. No way I could get an antenna
like that setup. The trade-off is of course being extremely high q, a very
narrow bandwidth. Hence the RX loop on the right.

https://goo.gl/photos/PExWyEYZmtVQDSgf7

The downside is the weight and bulk, a small transmitting loop made out of
some coax is going to be down on efficiency significantly, and even low
wire antennas probably will outperform them. Sure are easier to setup when
you don't have trees around, however. Just wanted to make sure people
understand STLs are not necessarily low efficiency, just certain designs
are, and the portable models I've seen all fall in that category.

On Apr 21, 2017 22:02, "Ron D'Eau Claire" <ron at cobi.biz> wrote:

> The very BEST magnetic loops are incredibly inefficient, yet like any
> "incredibly inefficient" antenna one can make amazing contacts on them when
> conditions are right.
>
> The problem is with resistive losses. The day we have room-temperature
> superconductors, we will have efficient small transmitting loops. Until
> then, only a few percent of the power applied is radiated.
>
> For now, they are great when simplicity of setup allows operation where
> otherwise nothing could be done.
>
> 73, Ron AC7AC
>
> -----Original Message-----
> From: Elecraft [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Phil
> Hystad
> Sent: Friday, April 21, 2017 7:45 PM
> To: Eddy Avila
> Cc: Elecraft
> Subject: Re: [Elecraft] Experiences using a portable HF loop
>
> The May 2017 QST not only does a review of the Elecraft KX2 but it reviews
> the Alpha Antenna, 10-40 meter support.  This is a magnetic loop antenna
> and
> I think it retails (basic model) for $299.
>
> 73, phil, K7PEH
>
> > On Apr 21, 2017, at 6:24 PM, Eddy Avila <k6sdw at hotmail.com> wrote:
> >
> > Greetings all, I'm curious to hear from anyone using a portable HF
> magnetic loop. I've read the theory behind them so I'd like to hear your
> opinion about them? How efficient these antennas are, especially running
> qRP.
> >
> >
> > Thanks all,
> >
> >
> > 73
> >
> >
> > ed
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