Tuesday, October 1, 2013

My SOTA Antennas

I do not know much about a great many things. Antenna design is one of those things. There is a lot of theory behind them and over the years I have used many different types from portable loops to the USAF AN/FLR-9 (also known as the Elephant Cage).

Half the fun of SOTA for me, is trying and building different antennas. Three antennas have become my favorites, the 58 Foot Longwire, the Linked Dipole and the EFHW. I will talk about the dipole and the long wire.

So why these antennas? Well, I have a few requirements.

1. Light weight
2. Easy to deploy and secure
3. Does not cost much
4. Good Performance

For the record, I have a buddistick, buddipole and many buddipole add-ons and love experimenting with different configurations. I also built a homemade buddipole for not much cost from Budd's plans that he openly post on the Internet. The Buddipole system works great from a car or camper and that is how I use it. It falls short for most of my SOTA activations because I do want to haul up it up a SOTA summit however, I have configured a buddistick vertical that performs great that I have taken up summits when I know I will have limited space. It works great, it is easy to assemble and break down, easy to match to the specific freq you want to work but it is a little heavy and bulky.

I have used an Alexloop and although I did not do an A/B comparison I feel (only my opinion) that it would be adequate for a few contacts on the higher bands but for 30 meters and below I would not expect too much from it. I have not attempted to construct one as I feel the performance to labor, parts and cost ratio is not worth it. The commercial version cost way too much and takes up too much space in a pack and is not a solid performer so it is a no-go. I found it rather cumbersome to put together and take apart. However, some people swear by them and it is a fact that any antenna will work sometimes and at 10,000 feet a dummy load might work too. It is a personal decision on what works for you and what does not.

My home antenna changes but my mainstay is a highly modified Hustler 6BTV that also works on 12, 17 and 160 meters. Its performance on 40 meters and below is lack luster but  it performs as well as my G5RV to the point that I can rarely tell them apart with an A/B comparison.

Onto SOTA Antennas. I found that I am making antennas specifically for the radio I am using. For my 20 meter only radio, like the Rockmite, I use a EFHW feed with 6 feet of RG174 and it works great.

For the ATS4b which has 80, 40, 20 and 15 meters I use the linked dipole feed with 25 feet of RG174. Here are some pictures of it:

Center of Dipole
You can see the center connector as nothing more than a BNC connector. I picked up a few of these at a hamfest.
Center connector

The links in the linked dipole
The connectors are from Hobbyking and are 2 mm in size.
The linked separated for band changes
Here is a link to the linked dipole instructions I used. The instructions came from WA3WSJ's web site which is worth a look. I added a few inches to 20 meters and also added a 15 meter section to the end so NO TUNER required. The lack of a tuner is important because the ATS4b does not have one built in and I do not want to carry one along with extra cable.

This antenna meets most all of my criteria to some degree. It is light (number 26 teflon wire helps). It is easy to deploy, assuming you have the space for a 40 meter dipole with center support, and secure. It performs like you would expect a resonate dipole above 9,00 feet to perform, great!  There is not much cost associated with this antenna. I could most likely make 10 or 12 more without purchasing anything more than what is already in my junk box.

I do not use any type of winders, they just take up space. I butterfly all my antennas and coax using a method I learned while processing 5 level paper tape in the late 70s. Here is a short video of me demonstrating how it is done.



Winding it this way makes it easy to deploy and secure.

The disadvantage is coax is required to feed it. RG-174 is what I use due to weight and it is less bulky than RG-58 but it is lossy although it is irrelevant for my purposes.

It is great mated to the ATS4b which is why I built it.

ATS4b mated to the Linked Dipole on a SOTA summit, what fun!

The next antenna I have been using a lot is the 58 foot longwire. I cannot take credit for this (or any other antenna for that matter) as Steve, wG0AT started using this design along with the Coleman Clothes Line Winder as the device to secure and deploy it. The first time I used it I was hooked. For the KX3 this is a perfect antenna. I have never tried it below 40 meters yet but I am betting it tunes ok.

It is 58 feet of number 26 teflon coated wire secured to the winder with about 20 feet of fly fishing line. Total cost, around 4 dollars! Does it perform, you bet. Is it easy to deploy? As easy as using a fishing pole or throwing the end up in a tree.

Antenna wound up and BNC connector

Just connect the wire to the red connector (no counterpoise)
Connected tot he KX3
Rooster approved antenna
Stock winder from Coleman
Just twist to open
Tie 20 feet or so of fly fishing line to the center and the 58 feet of wire to the fly line. 
You may need to enlarge the hole a bit
Just throw it in the pack and go play radio!!!!!

I have seen those coleman laundry cloths winders for 2 to 7 dollars. I found mine at the PX on Fort Carson for around 2 dollars and bought the last one. I check every time I go there just in case more show up. You may be able to find them on-line cheaper. The wire I purchased from a local supplier but the wireman may have something similar.

So there you have it. I do not know what the theory says about any of these antennas. I do know they work and do not cost much. There are a lot of companies out there that make antennas for "portable" operations. I am sure some of them are great but their definition of portable is probably different from my definition.

Set your requirements and build or buy what you think will fill those requirements the best.

72
Frank
K0JQZ



3 comments:

  1. Very cool. Your antenna ideas are really efficient in terms of size/weight/cost! I assume you have to use a tuner with the random wire one? How do you get the dipole up?

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  2. With the random I wire I use the tuner in the radio (KX3 or KX2) and usually I just throw a line in a tree and support the center of the antenna and try to configure the ends out of the way. On a summit with no trees I use a crappie fishing pole that can be extended. 72 Frank K0JQZ

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