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Author Topic: Highly Portable Antenna for Elecraft KX3  (Read 11580 times)
NI0Z
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« on: April 19, 2012, 05:01:19 AM »

Just looking for input, wanting something that packs up like the buddipole and has best gain.  Is the answer a buddipole?  I do not want to throw any wires, so a self standing solution is what I really want including tripod.  Ultra light is also a requirement.  160-2M if possible but if not then 40-2M will work.

Thanks in advance for your input.
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K2DC
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« Reply #1 on: April 19, 2012, 05:09:53 AM »

If you're looking for a single antenna for that wide a frequency range, the answer may well be a tripod and one of the Outbackers, although I don't know if they go as high as 2M.  I have used a Hamstick on a homebrew tripod before with reasonable success.

73,

Don, K2DC
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WX7G
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« Reply #2 on: April 19, 2012, 06:32:23 AM »

The MFJ-2299 telescoping dipole covers 20-10 meters and is full size (up to 33'). It will tune 80 meters with a 50 uH inductor on each side.

The Buddipole covers 40-10 meters and is 16' long. The MFJ 16' telescoping whips can be used on the Buddipole for higher efficiency and it will tune 40-10 meters but not 80 meters.

« Last Edit: April 19, 2012, 06:42:07 AM by WX7G » Logged
K5LXP
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« Reply #3 on: April 19, 2012, 06:57:51 AM »

Is the answer a buddipole?

Was the question "how could you spend the most money on the most mediocre antenna available"?  Otherwise, I can't think of any other questions where Buddipole is the answer.


Quote
I do not want to throw any wires,

Consider when QRP you're already 13dB down from anyone running 100W, and to toss another 12 to 20dB handicap on top of it by running crappy antennas isn't adding any value.  A crappie pole, some wire and a tuner will really make the difference running QRP/P and will be a lot more compact, efficient and easy to set up than those spendy contraptions like Buddipoles.


>  160-2M if possible but if not then 40-2M will work.

Consider optimized solutions for the bands you're really going to work, rather than a single compromised solution that covers all of them.


Mark K5LXP
Albuquerque, NM
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NI0Z
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« Reply #4 on: April 19, 2012, 09:07:28 AM »

Consider when QRP you're already 13dB down from anyone running 100W, and to toss another 12 to 20dB handicap on top of it by running crappy antennas isn't adding any value.  A crappie pole, some wire and a tuner will really make the difference running QRP/P and will be a lot more compact, efficient and easy to set up than those spendy contraptions like Buddipoles.

Fair enough, let's say 20,15 &10, I can always carry a separate antennas for 2&6.

Again, the reasons quoted above is why I am looking for something that's loss is minimal.  I should tell you that I will probably use this setup for QRP CW, RTTY and PSK.  I may buy the 100 Watt amp some day depending on cost for SSB.

Yes, 10 Watts is a challenge, but quite a thrill when you make a QSO.  If I had to go one band, then I guess it would be 20 since that's one of the most popular.

Thanks again for any ideas people have.  I already know there won't be trees in many cases to hang a wire where I will be operating so that's the reason for wanting something that self stands.

So, given I'll have 10 watts, the real request is what ideas do folks have to minimize the loss?  I am trying to get something that could handle the amp if I get it as well.
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AA4PB
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« Reply #5 on: April 19, 2012, 10:20:29 AM »

If you have rulled out wire then you have ruled out all the reasonably efficient portable antennas. A physically short antenna like a mobile whip or a buddypole with 100W puts out about the same signal as 10W with a 1/2 wave dipole. I've made plenty of 40M CW contacts with a buddypole and 5W, but it's NOT efficient by any means. SSB or RTTY will be an additional handicap. CW or PSK31 would be better suited for low power and an inefficient antenna.
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NO9E
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« Reply #6 on: April 19, 2012, 10:26:13 AM »

There is a line of fiberglass poles that folds to 2.5 ft. One that extends to 20ft costs $20 and weights about 10z and a 15ft pole costs even less and weighs half as much. Both fit into a 24 inch suitcase. See Amazon.com and my review on eham.

A vertical with such a pole plus 1-2 radials direct to KX3 with AT will most likely do very well on 6-30m. Adding some wire to form an L would help on 40 and 80m. With thin wires (gauge 24-28), this setup weighs very little.

Ignacy, NO9E
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WB6BYU
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« Reply #7 on: April 19, 2012, 11:04:34 AM »

My choice would be one of the telescoping fiberglass poles to support a wire dipole.
Yes, you have to tie off the ends to something (could be a brick or a bunch of grass)
but they also serve to guy the pole.  Without guys of some sort you can't keep up
a light weight antenna unless you have a sign post or fence rail to clamp it to.

Wire is still lighter per unit length than aluminum tubing, so turns out to be the best
for light weight.  The same setup will cover 80m or 160m, depending on how much
wire you want to carry.  You can cut dipole wires for each band and install them in
any combination you want each time you set up, or use a single wire dipole with
small connectors to choose just the sections for a particular band.  Feed it with
RG-174 coax and you don't even need a tuner.  Total weight is probably less than
an antenna tuner, and efficiency is very good.

If you are mostly interested in 20m - 10m, then a vertical wire attached to a fiberglass
pole with a tuner at the base isn't a bad approach.  Probably even work well enough
on 40m.  Performance of vertical antennas is greatly dependent on ground conditions,
however, even with elevated radials to reduce losses right at the base of the antenna.
If you can erect it close enough to salt water then it can give excellent results.  In
other conditions an inverted vee at 20' will outperform a vertical using the same support.
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NI0Z
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« Reply #8 on: April 19, 2012, 11:57:27 AM »

I like this last idea, basically I can setup my own tripod, find a decent folding or telescoping pole solution and raise an inverted V and along with some long tent stakes for the leads and guying and setup something pretty decent.  Heck, I guess a person could even do this with a G5RV and get decent results.

Thanks
NI0Z
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G7MRV
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« Reply #9 on: April 19, 2012, 01:15:17 PM »

I like this last idea, basically I can setup my own tripod, find a decent folding or telescoping pole solution and raise an inverted V and along with some long tent stakes for the leads and guying and setup something pretty decent.  Heck, I guess a person could even do this with a G5RV and get decent results.

Thanks
NI0Z

Google 'Linked dipole', as used by many SOTA operators. A telescopic fibreglass fishing pole can be got that goes up 7, 10, 12 or even 15m (dont use the top couple of meters as these are too thin, unless you get a heavy duty one), fold down to about 1m long, weigh a few pounds. A few bungee cords or velcro straps will hold it to a fence post etc. A link dipole is very efficient, coax fed. You simple make the connections for the band you desire at the time. How long it is depends how many bands and how low in frequency you build it for.

Im building yet another of these to cover 40m and up, to use at work, as it can be up and down in 5mins flat, leaving me 55mins of lunch break to play radio!
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NI0Z
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« Reply #10 on: April 19, 2012, 01:42:16 PM »

Yup, here is what I came up with as a possibility.


Home-brew portable 20-10M inverted V

http://www.allfishingbuy.com/Fishing-Pole/Pole-A1-71-2-8013.htm.               $120
Should be cheaper options on this, just need to google more.

Base to be determined, something simple like spreadable legs with a nub or cup to insert and secure pole. Maybe $10

Wire Antenna Design based off the follow article http://www.norcalqrp.org/norcaldoublet.htm.  Maybe $20 for wire, hook, ect

I am wanting opinions since I am by no means any sort of antenna expert if taking the ends and bringing them down into an inverted V would still allow with work achieving resonance at 14Mhz.  I think that a little tuning work might be needed on this since my pole wouldn't quite be 30'.

I am very open to wire type suggestions as well, this design seemed really slick including the little fish hook I would need to secure the antenna to the top of my super duty fishing pole.  That pole collapse to 30", not perfect but not bad either.  Was thinking that if it were not windy one might even be able to use some elastic sewing band tied to a rock stick on one end and the inverted leads for the inverted V and some crude guying  for the pole.

This artitcle here helped as well, which got me to googling more where I found the design above.
http://www.w1npp.org/events/2010/2010-FieldDay/Antennas/Wire/0202036-twinlead-20m.pdf

These poles here are really cool, although not very portable: http://www.geodatasys.com/carbon.htm

Thoughts?

Thanks!
NI0Z


« Last Edit: April 19, 2012, 02:16:21 PM by EVERSTAR » Logged

AA5TB
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« Reply #11 on: April 19, 2012, 02:44:40 PM »

I use my 20' fiberglas crappie pole with an end fed half wave antenna for 40 m which doubles as a fullwave on 20 m.  The pole is supported with three guy ropes that are tied to the top of the first section and anchored with stakes at a distance from the base measured using the collapsed pole (~3 ft).  Ty-wrapped a couple of feet up from the ground is a waterproof box containing my link coupled tuned circuit used to feed the high impedance antenna.  A switch changes capacitors which changes the band of operation from 40 m to 20 m.  I single 1' stake at the base is used for the return.

No fence needed and it has easily withstood constant 30 MPH winds.  Very inexpensive.

73,
Steve - AA5TB
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G7MRV
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« Reply #12 on: April 19, 2012, 03:41:44 PM »

Linked dipole, no tuner needed
http://www.cqhq.co.uk/2011/03/linked-dipole-for-portable-sota.html

DX Wire, German site, source of excellent fibreglass masts and accessories
www.dx-wire.de/brit/

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WB6BYU
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« Reply #13 on: April 19, 2012, 05:58:37 PM »

Quote from: EVERSTAR

Wire Antenna Design based off the follow article http://www.norcalqrp.org/norcaldoublet.htm.  Maybe $20 for wire, hook, ect



Using speaker wire, zip cord, or ribbon cable has higher loss than RG-174 coax, and you may
not get as good of a match because the impedance isn't necessarily 50 ohms.  The plastics
used aren't optimized for RF.

Using such feedline at a high SWR with a tuner is even worse.  (You did want an efficient
solution, right?)

The 20m dipole fed with a half wavelength of 300 ohm twinlead will be reasonably efficient on
ONE band.  Well, maybe 10m as well, where the length is a full wavelength.  The SWR will be
much higher on most other bands (though there might be some serendipity, as is the case with
the G5RV and relatives.)

Using 50 ohm coax gives you a good match and reasonably low losses on all bands of
interest with out the bother, weight and expense of a tuner.  You can use RG-58 if the weight
isn't an issue, but you probably can't support it as high up the mast as you can the RG-174.
(Use a combination of the two if you need a long run from the base of the mast.)
The rest of the construction, including providing a loop or hook of some sort to attach it to
the mast, can follow the general principles shown in the various articles.



Quote

I am wanting opinions since I am by no means any sort of antenna expert if taking the ends and bringing them down into an inverted V would still allow with work achieving resonance at 14Mhz.  I think that a little tuning work might be needed on this since my pole wouldn't quite be 30'.



For best performance you want to keep the ends of the wire as high off the ground as possible.
That usually means tying them off with a rope at least as long as the antenna wire itself.  You
certainly don't want to bring the wire ends down to the ground.  Some knot tying practice
helps if you are gong to tie the ends off to a fence post or bush.

Mason's twine is convenient, or dental floss can be pressed into service if you want the ultimate
in light weight and a convenient dispenser.  My favorites are hard-braided line that I found in a
commercial fishing shop in Alaska, but it really doesn't matter that much.

You do need to learn to wind it up so it doesn't tangle, however, if you want to set the antenna
up quickly.

There are many sorts of light wire that will work.  I'd typically use something like #22 or #24
stranded, insulated hookup wire.  (Whatever I have on hand or can get cheap.)  Solid wire
tends to kink badly, but some thin solid aluminum fence wire might work out.



I've never heard the term "linked dipole", but I have built several such devices over the years.
The concept certainly isn't new.  The real question is what sort of multi-band capability you
want:  the linked / switched / sectional version means you only have a single dipole to put
up, but requires that you lower the ends and move the jumpers to change bands.  That's fine
if you stay on one band most of the time.  I use multiple dipoles on a common feedpoint
(sometimes mis-termed a "fan dipole" - that's a different antenna).  That allows me to use
multiple bands without changing the antenna - quicker if you want to operate multiple bands
without having to go outside.  I have a center insulator on the end of my coax and tie on
the dipole wires for whatever band(s) I think I'm going to use each time I set it up.  If you
build the sectional dipole using the plastic electric fence insulators that look like small
carabiners it is easy to remove sections that you won't be using.

Either approach works with good efficiency - the choice depends on your constraints of
weight and setup effort vs. operating complexity.
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KC8QVO
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« Reply #14 on: April 19, 2012, 07:20:19 PM »

I am a backpacker and I have found the most effective antenna so far for me is a jumper dipole. I didn't read through all the replies, so it may have already been mentioned or perhaps by another name.

My design evolved from 26 gauge copper speaker wire to 26 gauge "silky" wire, stranded copper clad steel with a black teflon-like jacket. It covers 6 through 40 meters in a full size dipole. The way it works is there are spade connectors at each segment. I start with 6 meters, tune to low SWR, then add a jumper on for the next consecutively lower frequency band, all the way to 40 meters.

This antenna is light, compact, and easy to string up. Most of my backpacking trips are around trees so its easy to set it up as an inverted V.

I also have a KX3 on order, I put my order in late on day 2 so I am still probably a few weeks out, at least. I can't wait!!! When the 2m module comes out I'll get that too, so far I have everything coming except the roofing filter and mic. 
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