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KX2/3 w/tuner owners: what antenna do you use?

I have been using a 20/40 trapped dipole from http://www.qrpkits.com/dualbanddipole.html feed point about 18’. I just made and yet to try a 25’ wire with a 25’ counterpoise as per the KX2 manual. I plan to try on Friday. I’ve tried a random wire end feed but for the life of me I could get good results with it with shorter lengths of wire…

Malen
VE6VID

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A unun is unnecessary with the KX2 or KX3 internal tuners. I routinely use a 58-foot radiator and a 13-foot counterpoise connected to the radio with a BNC-to-dual-post adapter without a coaxial cable. Make sure the radiator does not touch the ground, including boulders. If you can lob the radiator really high over a tree branch, this antenna system will cover 80 m through 10 m okay. If you cannot get the radiator very high, then the antenna still works fine from 40 m through 10 m. To get coverage on 80 m and 60 m with the radiator relatively low above the ground, then an 84-foot radiator and a 17-foot counterpoise works best for all HF bands. You’ll have lower losses if the leader and not the radiator rests on the tree branch. For less wear and tear on the tree, remove the rock or the fishing weight which you tied to the brightly-colored lobbing leader before retrieving the antenna. I tie the leader to a fist-sized rock using a scaffold knot (Google it!). If there is snow on the ground or if I’m operating in a mature forest with heavy organic material covering rocks, then a brightly-colored fishing weight is worth the extra pack load. I use a figure-eight loop which I thread through the heavy wire loop in the fishing weight and lock with a girth hitch. Since I value my brain, I wear a helmet for the David-sling-style lobbing operation. I chose an orange climbing helmet so I can wear it during the hunting season. In a treeless area you need something to elevate the radiator. Check sporting goods stores for a nesting pole. I bought a Chinese-made one from the internet, but I can’t find a URL for it. The labels include DIAO BUDUAN and 720 and TXDU. Perhaps somebody else can locate it and post the URL. 73, Bruce Prior N7RR

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Joe,

The 9:1 un-un and wire is a great antenna with KX2/3. The quick setup will get you on the air fast and be making contacts while a (possibly) more efficient (i.e. dipole) install would be wrapped around every sticker bush in the county! Plus the band switches are instantaneous. Bottom line, more contacts in a short amount of time with that antenna vs dipole/buddipole/etc (IMHO).

One comment would be to lengthen out your antenna to 35.5 feet. See the numerous “best long wire length” charts on the web. Recommended lengths are: 35.5 41 58 71 84 107 119 148 203 347 407 423 (all feet). Going with 35.5 vs 30 does mean it is slightly longer than a 10M SOTAbeams pole, but I just slope the bottom end out. Note I tape the wire to the top and then about 7 and 14 ft. down from the top.

As far as coax goes, it is recommended to have a 25 ft of coax as the coax acts as the counterpose (info here: https://kx3helper.com/endfed-40-6m-antenna/). I started with 25ft of RG-58, but now use RG-174 for my ultralight setup. Can’t really tell the difference (58 vs 174) and solid into the skimmers as always. http://www.cablesondemand.com/pcategory/20/category/CO50OHM/URvars/Catalog/Library/InfoManage/50_OHM_COAXIAL_CABLES.htm has been a good source of both.

In the end, the KX2/3 will tune up without an antenna connected (the tuner is amazing). Like N7RR said (also see WG0AT setup) you can direct connect wire to the KX2/3 and it works great. I think you will like the endfed for ease of setup, band changes and it really does get out great from a summit. Even works with it laying on the ground with the mast falls over :wink:

73, Jim/K7MK

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Exactly the set up I use Bruce, works really well

Terry G4POP

What’s an “end insulator”? :wink:
I use short loops of woven Dacron fishing line, preferably in fluorescent orange so they are harder to misplace. And/or plastic Nite Ize S-Biners. Occasionally the larger #275 paracord. Never 550 paracord for portable work.
I often clip things together (guy lines, support lines, stuff to squid poles like transformers, etc) with stainless steel Nite Ize S-Biners, size #1, sometimes size 0.
I find that size #1 are easier and quicker to operate while still being light and low bulk. Fast setup, even faster bugout. I always pack a few spares.

In the US, Home Depot carries an assortment locally or mail order them from your favorite online vendor.

I also use the Nite Ize plastic Mini CamJams with #275 paracord (fluorescent orange of course) for tensioning ropes and attaching squid poles to various objects.

No association to Nite Ize, just a very happy repeat customer.

BTW Homebrew: 67 feet 24 gauge Tefzel EFHW, 64:1 FT140-43 transformer, 30ish feet LMR195, coax/counterpoise, squid poles, etc.

I sometimes get reports of RF in my audio (band and coax length/position specific). Moving the coax around often solves the issue. 3 turns of coax through a large type 31 clamp-on ferrite solves the problem but adds weight.

73,
Bruce W2SE

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In a recent SOTA antenna test, all the wire antennas were pretty much the same except for the EARCH antenna, which was much worse.

wunder

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This is one of the bits of info which gave me pause. That said, even the tester notes that the EARC setup was sub optimal. He was running 10m of RG174 to it. I don’t know where that leaves the comparison.

Hmm, 58’ with 13’ counterpoise. Off I go to cut more wire to give it a try on Friday. Use a golf ball with an eye bolt in it, bright green as a throw weight.

Pretty hard to lose that many dB in 10m of coax, even with a bad match.

I’m guessing that the EARCH transformer is lossy. That would make it broadband, but at a cost.

wunder

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Hi, i am operating. KX2, 10 W SSB, with variou antennasc, eg. AlexALoop, EF 20/40 m, CH Vertical with extension and Un-Un 9:1, upper/outer 5 m wire/ fishing -rod,
I notice practically no difference between these antennas, actual conditions matter, in my opinion, more then the typ of antennas. As an example I made a contact in Ssb from Switzerland to Australia, this is a rare exemption in my opinion.
Just keep on trying and experimenting, in my case, when I get the impression , that few Contact may be due to the wrong antenna, I select for the next activation an other typ of my antennas, the result my be better, but why this is the case, I don‘t know.
So if you are „Hercules“ carry all different antennas along, else consider Weight an use an Endfed wire and 5 m fishing rod.k
Ed. hb9zap

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Yes. The spool of wire, roll out on a wire winder taken from a kite. The wire length is about 40m long (~130 ft) and I use the longest possible. Never had a problem with KX-2 (or KX-3) to tune the antenna.

Sometimes is use a L configuration but sometimes I don’t.

L configuration

Sloper

The wire winder

All wire in it

Note the plastic ring used to be sure there are no stress on the terminal

The last version of 9:1

Top antenna insulator (from SOTABeams) + keyring

Vy 73 de Pedro, CT1DBS/CU3HF

I dumped using 550 cord for portable ops a while back and go with this:

Rated 100lbs strength. And somewhere’s around here I do have an Atwood roll that says rated to 350lbs. Never tested, yet. :wink:

Works great…

Later,
Todd KH2TJ

2 Likes

Hi Barry

Sure. You could use RG-213 or RG-8… :wink: Less dB loss in the cable but a little bit more weight and not so manoeuvrable…

That’s why I bought the best RG-174 in the market. And tested it, of course.

I want a compromise between weight and functionality.
It works ? FB and move on to activate summits ASAP. :slight_smile:

I agreed with Ed, HB9ZAP

73

If I can, I use a linked dipole. If I can’t use that, I’ll fall back to either a monoband vertical with elevated ground-plane, or to a 42ft end-fed wire (with counterpoise on the ground of about the same length) fed almost directly into the rig.

You can see this last lot in this thread --> Stapellager Berge DM/NW-089

You’ll notice there are two short lengths of coax. One is about a foot long and fitted with a right-angle BNC. The other has a ferrite choke, and is handy if RF starts to get back into the rig in un-wanted ways.

Hi Joe, you can’t go wrong with a SOTABeams band hopper linked dipole and a fibreglass fishing pole. You can even build the antenna yourself if you prefer (calculator is on the Sota Mapping Project website).


http://www.sotamaps.org/extras.php

I’m sure you will have - or will - get lots of other suggestions.

The linked dipole requires no ATU by the way.

My second choice would be a HF “J-pole” antenna but these are single band antennas but small, light and again need no tuner.
http://www.lambdahalbe.de/drahtantennen/kw-amateur-monoband/index.html

73 Ed DD5LP.

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Dipoles and inverted Vees are hard to beat but harder to set up in the field. You might want to look at the 49:1 end fed half wave. This is a resonant end fed vs the random non-resonant 9:1 EARC. I’ve built and compared both on WSPR with an inverted Vee at the same height and the EARC was averaging about -6 dB across 10 stations in a 1 hour period. The 49:1 EFHW was about +3 dB over the inverted Vee but I think that might have been coax loss (~ 150 feet additional for the inverted Vee) and a lower takeoff angle of the sloper configured EFHW.

The 9:1 EARC is also pretty finicky… I could get decent results at home but when deployed for FD, it never worked very well. The 49:1 seems to work the same at home or in the field.

As an added bonus, since it’s a resonant antenna the 49:1 EFHW doesn’t require a tuner. I get a fairly flat SWR (1:1-2:1) on 40/20/15/10. SWR on 30m is around 3:1 so an internal can tune it or you could use a halfway length wire on 30m for better results.

73 Gene KJ4M

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I was reading about these last night. Two questions:

  1. How long of a feed line do you run? Ie how far is it from the place the wires split back to your radio?
  2. How high do you generally elevate the ends of each end of the antenna?

The feed line is 28 feet. I split the wire to make the legs, then tied a simple overhand knot around a SotaBeams top insulator to keep it from pulling apart farther. I crimped and soldered some fork-shaped terminals (like this) at the end, which I screw onto a BNC to binding post adaptor which goes right to the KX3 (or tuner). Most of the time 28 feet is more than enough feed line, and some of it lies on the ground while I operate.

For the ends, I have two ropes that I use. I have not measured their lengths. If there is a tree or bush, I’ll tie the ends up as high as I can, but sometimes they are just staked to the ground. I have a pole that will get the center up about 17-18 feet, and I use that unless there is a convenient tree branch. I’ve found the KX3 rarely needs to retune for different setups.

New photo by Jeffrey Kabel
Here you can see one of the legs tied to a fence, at the last post before it goes into the bushes. It is probably about waist high. The pole and other leg are similarly attached to the fence. (Barbed wire fences are great antenna supports) W6/NC-402

New photo by Jeffrey Kabel
Here in a free-standing setup. There are three support ropes to hold up the pole, then the two legs staked to the ground. Mt Misery, W6/NC-197

If you peruse my blog, you can probably find more pictures of the various ways I’ve set up. In the end, simply being on a summit give you a huge advantage, so I don’t worry about eliminating every last fraction of a dB of loss.

Hi Gene,
what is the difference between a 49:1 and a typical 81:1 EFHW in terms of radiator length?
Martin

Hi Martin,
I’m not familiar with the 81:1 but that would transform 50 Ohms to about 4 kOhms. The EARC, (27T secondary/9T primary)^2 for a 9:1 impedance transform so 50 Ohms to 450 Ohms. The impedance at the end of a half wave dipole is roughly 2500 Ohms so the 49:1 (14T secondary/ 2T primary)^2 gets close (50 Ohms*49= 2450 Ohms).

Wire lengths that I used for the EARC were 31, 54 and 71 feet. I found a list of lengths online for these “random” lengths but they really aren’t random if you need to tune them…

For the 49:1 transformer, the same half wave dipole calculation can be used. I’ve tested ~33 ft for 20-10m, ~67 ft for 40-10m and ~134 ft for 80-10m length wire with good results.

Gene