Posted by
Elecraft mailing list on
Aug 31, 2017; 2:42pm
URL: http://elecraft.85.s1.nabble.com/Is-it-my-KX3-antenna-or-is-it-lousy-band-condx-tp7633243p7633906.html
I prefer to use the end fed wire in an inverted "L" configuration with the vertical leg running down a FG pole to the radio.
Mel, K6KBE
From: Barthold Lichtenbelt via Elecraft <
[hidden email]>
To: 'Walter Underwood' <
[hidden email]>; 'Reflector Elecraft' <
[hidden email]>
Sent: Thursday, August 31, 2017 7:28 AM
Subject: Re: [Elecraft] Is it my KX3/antenna or is it lousy band condx?
Walter,
This was a super informative writeup, thank you!
I have one question for you. If you throw a 26-29 foot wire in a tree, but it is impractical to sit right at the end of the wire (too many branches in the way, or whatever) to operate, how would you extend it? For example, operate from a table 20 feet away.
Thanks!
Barthold
AD0RM
-----Original Message-----
From:
[hidden email] [mailto:
[hidden email]] On Behalf Of Walter Underwood
Sent: Sunday, August 13, 2017 10:10 AM
To: Reflector Elecraft
Subject: Re: [Elecraft] Is it my KX3/antenna or is it lousy band condx?
In July, five SOTA operators put up seven different antennas on a summit and compared their performance with WSPR. Six of the antennas were mostly within 3 dB of each other. The EARCHI antenna (end-fed with transformer) was between 6 and 15 dB worse than the others. So in one experiment, the 9:1 transformer did not help.
http://reflector.sota.org.uk/t/seven-sota-antennas-compared-using-wspr-on-a-summit/15635 <
http://reflector.sota.org.uk/t/seven-sota-antennas-compared-using-wspr-on-a-summit/15635>
When the antenna is connected directly to the KX3, there is no transmission line, so there is no need to match the antenna to the transmission line. It is putting the ATU at the feed point of the antenna.
The 26-29 foot length is chosen to avoid very high or very low impedances in the ham bands down to 40 m Especially, it is not a 1/2 wave on any band. That makes it easier to match. If you want to work 80 m, use a 53 foot wire.
The 16 foot wire on the ground is a radial “system”. One radial is a lot better than none, but you could use more. The length isn’t especially important because it is capacitively coupled to the ground. Ground resistance swamps any resonance.
I first heard about this antenna on this list. It was recommended by Wayne, N6KR. It is documented on page 9 of the instructions for the KXAT1 antenna tuner, “...for backpacking use on 40/30/20 meters, a wire length of 24-28 feet will generally provide good results. […] Ground system: Use a at least one ground radial, cut to at least 1/8th wavelength on the lowest band used (16' on 40 meters). When possible, use two or more radials, with one cut to 1/4 wavelength on each band."
http://www.elecraft.com/manual/E740054%20KXAT1%20man%20rev%20B.pdf <
http://www.elecraft.com/manual/E740054%20KXAT1%20man%20rev%20B.pdf>
There is similar advice on page 10 of the KX2 manual.
http://www.elecraft.com/manual/E740282%20KX2%20owner%27s%20man.pdf <
http://www.elecraft.com/manual/E740282%20KX2%20owner's%20man.pdf>
Finally, stop trying to think about “balanced” and “unbalanced” because those words are used in bizarre, inconsistent ways. Voltage, whether DC or RF, is always between two terminals. With a center-fed dipole, the two terminals are the elements. With this setup, the two terminals are the wire in the air and the wire on the ground.
wunder
K6WRU
Walter Underwood
CM87wj
http://observer.wunderwood.org/ (my blog)
> On Aug 13, 2017, at 5:31 AM, rich hurd WC3T <
[hidden email]> wrote:
>
> Hi all, particularly Walter (since he mentioned it):
>
> I've been bedeviled by a question with multiple possible answers.
>
> I'm a fan of the idea of using a field antenna as Walter describes by using a BNC - to binding post connector directly to the radio.
>
> I'm leery of that because it flies in the face of what I've been told about these antennas: I'm assuming the radio BNC connection is unbalanced and the wires form a balanced antenna, more or less. I've seen deployments with end-fed 9:1 baluns and without, even documented on YouTube with great successes.
>
> I can tell you that the 9:1 balun setup doesn't seem to be working for my current field deployment but I'd sure like to understand why a balun isn't recommended in this setup. I'd love to just take the wire and put it on my WonderPole and go for it, but I'd like the understanding first. Why does this work? :)
>
> Thanks.
>
> On Fri, Aug 11, 2017 at 13:19 Walter Underwood <
[hidden email] <mailto:
[hidden email]>> wrote:
> You can get a quick look at band conditions at
>
http://bandconditions.com <
http://bandconditions.com/>
> <
http://bandconditions.com/ <
http://bandconditions.com/>>
>
> Using Buddistick on 40 m is a real challenge. I would not be surprised if that was an S-unit or more below a full-size dipole.
>
> Try the simplest field antenna for the KX3, two wires connected directly to the rig. Get a BNC to double binding post adaptor. Get a wire 26 to 29 feet long, throw it in a tree and hook one end to the red post. Get a 16 foot wire, lay it on the ground and connect it to the black post. Let the ATU tune it and see you can hear.
>
> wunder
> K6WRU
> Walter Underwood
> CM87wj
>
http://observer.wunderwood.org/ <
http://observer.wunderwood.org/> (my
> blog)
>
> > On Aug 11, 2017, at 9:54 AM, Tommy <
[hidden email] <mailto:
[hidden email]>> wrote:
> >
> > The band has been really crappy lately. Keep tuning around and listening.
> >
> > 73!
> >
> > Tom - KB2SMS
> >
> >
> >
> > On 08/11/2017 12:33 PM, Mike Parkes wrote:
> >> Okay I am reaching our to the Elecraft enthusiasts here for some
> >> feedback if anyone cares to chime in.
> >> I am just getting back on the air after years away from the hobby,
> >> so I am not that familiar with band conditions in general. It looks
> >> like the sunspot cycle is heading for the cellar (if it isn't already there).
> >>
> >> Recently bought a KX3 and a Buddistick vertical (like, 2 weeks
> >> ago). Love the KX3 it is a great radio... however... so far my
> >> efforts to hear much of anything, much less make a contact with
> >> someone, has been frustrating to say the least. I live in an
> >> apartment and am surrounded by power lines for one thing. The
> >> background noise level on 40 is pretty bad varies but is
> >> s7-9 mostly. I took my setup to a nearby park and the bands were
> >> definitely quieter. So the local manmade noise level is an issue
> >> (and one reason I chose the KX3 was the hope that its rcvr and
> >> filtering could help with that.)
> >>
> >> Have yet to make a single contact, so I am just wondering if I just
> >> happened to choose a really lousy period of solar conditions for
> >> HF? Or is the base loaded vertical a joke?
> >>
> >> I would love to be able to find another ham even close by just to
> >> try and get some sort of an HF QSO even if it is with someone down the block.
> >> ...I can tune down to the AM broadcast band and was able to hear
> >> some local AM stations. :)
> >>
> >> Mike AB7RU
> >>
> >> (On a side note the tuner in the KX3 is great!. That thing was able
> >> to get a match for 80 meters on the Buddistick which was showing
> >> something like
> >> 25:1 swr. The KX3 tuner clicked and rattled for a while and found a
> >> match to <2:1. Not sure how much actual RF is going out, probably
> >> not much... but I was amazed it could tune to that high an SWR.)
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> 73 (or 72 for the QRP folks),
> Rich Hurd / WC3T
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