Survivalism & Self Sufficiency Topics > Amateur Radio How-To's

All Band Single Wire Antenna,The Zeppelin

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Carl:

--- Quote from: Canadian Prepper on February 11, 2015, 10:56:14 PM ---Quick addendum: I see now why 84-85 feet and 17 foot counterpoise was chosen, as well as the longer lengths that help versus which ones to avoid: http://udel.edu/~mm/ham/randomWire/. It's a case of trying to avoid multiples of half wavelengths which are harder for the tuner to match. There's lots of articles about the length combination above from 1936 to present, and a chart at the link above indicating which other lengths might work best for particular bands.

--- End quote ---

YEP,Random is not so random. And while I arrived at the 17 foot counterpoise during experiments with tripod mounted mobile whips for HF work (Hamstick from MFJ) I settled on 17' 6" and use a 20 meter dipole in my portable kit as the verticals counterpoise and it allows few items in a small kit to provide many antenna configurations. I rarely need to go portable now,but do advise those who do on the importance of antenna kit components.

helix2301:
I don't know if it helps but this month is QST's Yearly Antenna Issue. It might help if you have questions or need ideas for antennas

http://www.arrl.org/qst

Canadian Prepper:
The initial results are in! This antenna design looks very promising, despite a few kinks that I still need to work out. Many thanks to Carl for all of the information and links that he posted, that were invaluable.

The basic design of this antenna was first mentioned in a 1936 article in QST, where the author spoke of an antenna put together by his friend W3EDP, who used an 84 foot wire and 17 foot "counterpoise." A variation on this design is the antenna posted by Carl at the top of this thread, which gets the same 84 foot main wire by attaching 67 feet to 17 feet of ladder line, with the wire on the ladder line that's not attached to the main line playing the same role as the 17 foot "counterpoise" in the original W3EDP. Since Carl indicated that the design with ladder line can effectively work 80 and 160m with 92 feet of line, I took that as to mean that 92 plus 17 feet (109 feet total) should be my starting point. I also took note of the following line from another blog post on the subject, which suggested another slightly longer length: "If you are using a longer length of wire, perhaps as a Sloper or inverted ā€˜Lā€™ good lengths to choose are either 19.4, 22.8 or 34.3m long (112.5 feet), as these avoid high impedances on most of the Amateur bands from 160 to 6m." (Source: http://www.g8jnj.net/usingautotuners.htm). Adding another foot to play with, and a further foot to make up for any wire that will be bent back upon the balun or insulators gave me starting lengths of 114 feet for the long wire and 19 feet for the "counterpoise." The fellow who cut my 150 roll of wire seemed to add an extra foot or two for good measure, leaving me with an additional 18 feet, so I could possibly set it up with two "counterpoise" wires that would sit a short distance above the ground.

FYI, the shorter wire could also be set up with spacers to ride up on the vertical portion of the antenna just like ladder line and I'll probably do that eventually, but for now I wanted to just get the antenna installed and on the air.

And one more point about the antenna length before proceeding further to my initial results. The following link (http://udel.edu/~mm/ham/randomWire/) provides some further information about the ideal lengths for a so called "random wire" antenna, that isn't so random after all. If you look down the page, you'll notice that the author provides a colour coded chart that shows which lengths to avoid if you want to have multiple band capability. If I understand correctly, the lengths are multiples of quarter or half wavelengths that make it difficult to tune to the bands that they match.

So here's my initial results:

I set the balun and feed point to the antenna just outside my apartment with the long wire rising vertically (at a bit of an angle) up to the an insulator at the top of a second story balcony at about 17 feet). The short wire extends from the balun just above the ground to an insulator that's attached to a wooden fence. From the balcony, the long wire crosses the yard to another insulator tied off to a tree in the northwest corner at about 20 feet, and from there the wire crosses over a coach house to the northeast corner, where it passes through another insulator tied off to a tree at about 10-12 feet. I first tied the remaining length of wire to a balcony support post that only gave me ten feet in height and passed awfully close to a power line and trees along the edge of the property. After my first attempt at tuning the antenna, I took down the last leg and connected it to a tripod/crappie pole that now has the end point several feet away from the power lines and at somewhere between 17-20 feet high in an open spot in the yard. It didn't change the tuning characteristics, but at least confirmed that any problems tuning on some bands was unrelated to the power line and branches.

So far, the antenna tunes nicely onto 40, 20, 15 and 10m. Because it had gotten dark by the time things were set up, I checked into the "Brother's Net" that runs Monday-Saturday evenings from 7-9pm on 7.192Mhz. I had no trouble checking in and was 59 to the NCS in Maryland (about 500 miles away) by the time he got around to my number.

80m was a slightly different story. I've been listening on a few different frequencies, including the daily Great Lakes Emergency and Traffic Net that runs everyday from about 8-9pm EST. So far I'm able to comfortably listen to a net that's usually much harder on the ears to follow, and I wouldn't be surprised if the improvement in Rx has been a full S unit or higher. But when it comes time to tune, I'm not getting anywhere near the under 2:1 SWR that we're after.

Looking back to the chart on the link above, it looks as though the antenna with a couple extra feet for fudge factor lands within the coloured zones that occur from about 109-132/33 feet. According to the chart, I should get 40m and higher, but not 80 and 160. There is however a window from 104-109 feet (that also falls within the lengths listed in Carl's first post) within which 80 and 160m should be tunable. Though I'm not too concerned about 160m access and might find an 85 foot long wire easier to deal with, I like the stronger Rx that seems to come with this longer antenna and will probably just tune it down to somewhere between 105-108 feet, or somewhere between 100-103 feet to avoid a zone about 104 feet that I ought to avoid. The chart that I'm referring to was also for the CW portion of the bands in question, so there'll be a bit of shift for SSB that I'm after. Before I trim I'll see if adding the second 18 feet of wire as a "counterpoise" changes anything for the better (if it doesn't work I'll just take it off again) and I'll consider connecting the short wire to the longer one in twin lead fashion after I get things working with the antenna as set up.

Like any first time setup of a wire across a backyard, I can envisage better ways to position it and will endeavour to get at least the end point several feet higher, or at least tie it into the second floor balcony. For Sunday morning and early afternoon, I'll also try it on a couple of 40 and 20m nets that I regularly check into to get a better sense of how it compares to the dipole that's currently down.

So I'm not quite there yet to my goal of an effective antenna on 80m, but if I can get the length adjusted to a low impedance sweet spot, I'll have an effective 80m antenna that will also work on 40 and a couple other bands. More to follow....

Carl:
 :egyptian: :egyptian: :clap:  Testify brother...another convert to wire antennas....

Carl:
Hey Canadian Prepper...the 17' 6" length was pretty critical when using plain wire (Not ladder line)and I am guessing also 17' would be critical if ladder line were used...That second 18 feet of wire might should be carefully cut back to 17' 4" or 17' 6" ...maybe do the test first at 17' 6" for one or BOTH of your short wires.

I had the same problem when developing my BIG STICK VHF/UHF antenna and the radio of the short  to long wire is pretty critical.
Lets think 85/17  represents a 5 to 1 ratio...I would stick to a 5 to 1 ratio while avoiding the  multiple wave zones of the cut chart.

Just a though if you start scratching your head with getting the wire to tune multiple bands ....I actually did go through this with my first few versions but don't know for sure if it were my surrounding or the antenna.
And it is interesting I worked up to my 17' 6" and 35' for my 20 meter design without being aware of the W3EDP.This is still an experimental antenna for me and I want to see if our results compare.

I also found this and just want to note how he also discovered the importance of 17 feet for the short wire as antenna current is RF POWER...

http://zs6rsh.blogspot.com/2014/03/rf-current-measurements-on-long-wire.html

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