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[K3] MFJ-1786 Antenna

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[K3] MFJ-1786 Antenna

Does anyone have any experience using a MFJ-1786 with a K3? I live in a 2nd floor condo in a 5 story brick building. Considering a magnetic loop on my balcony to get back up on HF.

73 de Dave KJ6CBS
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k6dgw

Re: [K3] MFJ-1786 Antenna

No experience with the MFJ but I do have an AlexLoop and it's pretty
versatile, sets up fast, is fairly immune to things around ... and
ground or the lack of it. It's definitely QRP, I'm not sure I'd want to
fool around with a mag loop at 100W. Narrow band [really] on 40 and 30
but tunes easily, I use mine mainly activating SOTA summits.

One thing you need to know if you don't already, most are resonant
transformers and *MUST* be exactly at resonance. Getting it close, like
3:1, and letting the ATU do it's thing is a recipe for a dummy load.
Bypass the ATU.

73,

Fred K6DGW
- Northern California Contest Club
- CU in the 2014 Cal QSO Party 4-5 Oct 2014
- www.cqp.org

On 9/6/2014 6:50 PM, David Guernsey via Elecraft wrote:
> Does anyone have any experience using a MFJ-1786 with a K3? I live in
> a 2nd floor condo in a 5 story brick building. Considering a magnetic
> loop on my balcony to get back up on HF.

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Kurt Pawlikowski

Re: [K3] MFJ-1786 Antenna

In reply to this post by Elecraft mailing list

Dave,

I recently purchased a used 40-15 meter version (MFJ-1788). I live
in a first floor condo and really have no place to permanently mount it,
so I use it on either a short 3 foot stand or extend it to 10 feet with
my car stabilizing the base. I've had this antenna for about 6 months
now. So, here are my impressions...

First, if you like to jump around the band or bands, don't be in
too much of a hurry! It takes a little while to get used to operating
the antenna. While it's not too bad, you can't just spin the dial and
start transmitting. The practical bandwidth of the antenna on 40 meters
is about 10 kHz. You can receive degraded signals to maybe 30 kHz, but
they get weaker and weaker the further you are from the currently tuned
frequency. The bandwidth seems to get narrower as the frequency
increases. This is just the "nature of the beast."

Performance is very good. It appears to be on par with a full
dipole, but I don't have one to compare it to, so it's all subjective.
And, since my installation is very low (3 or 10 feet), my contacts tend
to be in the first, second or third skip zones. That is, it's probably a
fairly high angle of radiation. I have not tried the antenna in
"horizontal" mode, but maybe I will some time.

In my particular case, I have a very noisy mercury vapor lamp about
20 feet from the antenna that is dieing. When it's cycling, it
obliterates most of the signals with it's own 20 over 9 signal. This
simply swamps the KX-3's noise blanker. It is for this reason that I've
been in the market for the MFJ-1026. But, in the mean-time, I discovered
that my Drake R4-C noise blanker virtually eliminates it. I've been
toying with the idea of a "better" radio (K3 or Flex) that might have
enough processing power to nullify the noise. Of course, that's a
financial consideration!

At any rate, it means that, between tuning up the Drake R4-C, TX-4C
AND the MFJ-1788, it takes me several minutes to adjust to any new
frequency. Once I get in the sweet-spot, I'm not too likely to go very
far from where I am. Yes, using the KX-3 (during the day!) works well,
but you need to keep the ATU off as it defeats tuning the antenna. I
have even used this antenna sitting on the ground surrounded by metal
shelves and a parked car with a fair amount of success. Again, I have no
basis for comparison, so no objective data.

Well, I hope that helps!

kurtt

WB9FMC
2015 Hamfesters Hamfest Chairman
Looking for my replacement since 2014!
http:\\ham-ham.org

On 9/6/2014 20:50, David Guernsey via Elecraft wrote:

> Does anyone have any experience using a MFJ-1786 with a K3? I live in a 2nd floor condo in a 5 story brick building. Considering a magnetic loop on my balcony to get back up on HF.
>
> 73 de Dave KJ6CBS
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]
>

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Elecraft mailing list

Re: [K3] MFJ-1786 Antenna

In reply to this post by Elecraft mailing list

Yes. I've owned and used one. They can be amazingly effective. I
still have an AEA ISOLOOP - a forerunner. The 1786 is surprisingly well
made. The tuner with the built-in SWR/Power meter is very handy. They
are *VERY* narrow banded - especially on 40. QSY a few KHz and you will
need to retune. After a while your ear gets good at picking out the
rise in the noise level as you approach resonance. When I was
restricted as you are, I had many, many solid, enjoyable QSO's with a
100 watts. Just be careful that there is nothing metal near by - and
most of all be sure no one touches it while you transmit. The rf burn
one can get from contact are deep and extremely painful.

73, Doug -- K0DXV

On 9/6/2014 7:50 PM, David Guernsey via Elecraft wrote: