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Author Topic: Looking for antenna solutions for unusual location  (Read 1538 times)
KE8HH
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Posts: 2




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« on: November 16, 2002, 12:50:17 PM »

   We've recently moved to a rather unusual location and need some tips from the experts on the best choice for an antenna.

   Currently, we're living in a 40'x12' park model RV (the kind of rv that looks--and lives--like a small mobile home) in a Michigan resort. Our rv is 1-1/2 stories (it has two bedrooms in lofts upstairs) with the usual aluminum siding and shingle roof. The lot itself is approx. 25'x60', with tall trees across the back (25') side. Obviously, our only practical solution will have to include a roof mount installation.

       Obviously, a vertical is probably our most practical solution (unless someone can suggest an alternative, given the space constraints--we _can_ anchor the end(s) of a wire antenna to the trees behind us, but only if we keep the anchors high and within the 25' width limitation). Our primary questions concern the use of radials and grounding. With respect to radials, I read on the Butternut site that mounting in the center of the top of a mobile home obviates their need and provides an extremely efficient ground plane, in much the same way that mounting in the center of the roof of a car does so for a mobile installation. I've been unable to verify this claim in any of the (limited) resource works I have on hand--can anyone tell me if it's accurate and, if so, whether it would therefore allow for the effective use of an antenna such as the Butternut HF-9V coupled to a TBR-160S 160m add-on (which isn't recommended for use with the Butternut CBK kit--used to substitute for an efficient ground plane).

      We already have a (very large) DirecWay 2-way satellite Internet antenna there, which would make it difficult to use most beams on the roof w/o conflict with the dish. a few--in particular, either the Butternut HF5B "Butterfly Beam" or the Cushcraft MA5B beam may, otoh, be small enough to work since they are small enough to mount directly over the center of my roof (where they would clear the DirecWay dish) on relatively short tripods, and their turning radius would keep them over my lot. Using one of those in conjunction with a vertical or dipole for the bands it doesn't cover would, obviously, be a step up from a vertical--assuming I don't run into the same ground plane problem there, of course.

   I've also looked at a number of pre-assembled dipoles--including the Yaesu YA-30 which is only 83' long and claims to be pre-tuned for all bands (1.8-30 MHz) with a max swr of 1.9:1. Obviously, the antenna would need to be used in some form of "V" configuration, since I don't have 83' of space in any direction (including diagonally) on my lot. Because of the layout of the lot, an inverted "v" would be unworkable (the ends would have to go to the rv front & the center to a tree behind it--which would be far too narrow a spread for the "v"--in addition to which, the roof of the rv is peaked and that would put them at the low points), and I've never seen any information on a standard (non-inverted) "v" to determine if it could work that way with the center at  the top of the roof and the legs connected to two trees behind the rv.

   Adding to the already frustrating situation is the fact that, I'm partially handicapped (knee and respiration) and thus heavy roof work isn't an option--nor is having other local hams help out, since the resort (for liability reasons) won't let anyone not a member do any work on a site unless he or she is  a licensed contractor doing the work commercially (and  thus insured by his/her own firm against injury). I can get away with having my 18 year old son help (family membership), but he knows nothing about ham radio (he's a computer hobbyist <sigh>) or about installing antennas and will have to be "stepped" through the entire procedure.

   Right now my primary concerns are: (1) an efficient antenna system that will provide coverage of  as wide a range of bands as possible (I'm using an FT-920 which covers 6m-160m) with a reasonably good swr (i.e., one that can be tuned easily with either the built-in tuner in the FT-920 or, if necessary, with my external MFJ-969 tuner); (2) efficient use of space (the antenna _cannot_ extend beyond the limits of the lot size, and the less space it occupies the better); (3) reasonable wind resistance (the antenna will be exposed directly to winds from the SW, S, NW, & N but sheltered from the East) without extensive guying (space considerations); (4) reasonable cost and ease of installation (I'm a semi-retired college professor with the climbing ability of the average horse and don't expect to have any skilled assistance with the installation); (5) dependability.

   My primary questions:

   1. How accurate are the statements concerning the efficiency of a mobile home/rv as a part of the ground plane?

   2. Should the rv itself be grounded directly (it isn't currently) or will this defeat the effectiveness  of the capacitive coupling to the ground itself?

   3. What kind of antenna would work the best in this circumstance--other than a vertical are there other, potentially better, solutions?

   4. If a vertical is selected, what vertical would you recommend and--if one is available for it--would it be likely to work with a 160m kit?

   Any answers, suggestions, or comments would be greatly appreciated, either here or via email.

   73 de KE8HH, Rick
      ke8hh@qsl.net
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WB2WIK
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« Reply #1 on: November 18, 2002, 05:24:59 PM »

Sorry to hear about your handicaps, but it sounds like you've got enough help to make something work.

1.  In my experience, the roof of an RV or mobile home isn't a particularly good counterpoise for an HF vertical, and I'm surprised if Butternut claims otherwise.  An elevated, 1/4-wave vertical such as the HF9V (which is loaded to appear as 1/4-wave on those bands where it's physically too short) should have a set of tuned 1/4-wave radials to work properly.  Their CPK counterpoise kit is better than nothing, but not nearly as good as using three or four proper length radials per band.  I've tried it both ways, and the difference is rather staggering.

2.  See (1), above.

3.  Other verticals are probably more practical for your situation.  Possibly the Cushcraft MA5V, which covers 20-17-15-12-10m would be a very good start.  It has self-contained radials (so to speak) and requires nothing more than that...additional counterpoise materials seem to do absolutely nothing for this antenna, and it works well without them.  Of course, it doesn't cover 30-40-80-160.  An even better solution might be the F-12 Sigma 5, which is higher Q and handles more power, and looks nothing like an antenna -- it's small and stealthy, but highly efficient.  But, again, it does not cover the bands below 14 MHz.  Frankly, with a 25 x 60' lot, I'd strongly consider putting up a much larger, ground-mounted vertical like the Hy-Gain model AV-640, which covers 40 through 6 meters and works very well.  It requires no external radials or counterpoise at all, and seems to work about the same if it's 24" above ground or 24' above ground.  I hear a lot of strong signals eminating from these.

4.  Running 160m from a 25' x 60' lot is rather ambitious.  Why the big push for 160?  Maybe you just love the band for some reason, but I presume you know that this is a "nighttime only, wintertime only" band?  It's useless in the summer months and during daylight hours, and is much less of a useful band than 80m or 40m even at nighttime, unless one employs rather large antennas.  The minimal antenna I've ever found to work 160m at all, to make contacts beyond the next town, is an inverted-L, 165' overall wire length, with 40' vertical and 125' horizontal, installed over a large radial field on the ground.  And although that's a useful antenna, it will place you in the "bottom 10%" of the signals on the band, where the strong guys are using antennas that are much larger.  Unless you have some compelling need to work 160, I'd just forget about it.

73 & hope to hear you on the bands!

Steve, WB2WIK/6



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K1RDD
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« Reply #2 on: November 19, 2002, 09:09:11 AM »

Look at the Outbacker series. I have been lately, and have yet to find a bad review. My use will be for Field Day type operations, and some portable contesting, but they might be what you are looking for. They are a bit pricey, but, you get what you pay for.
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« Reply #3 on: November 28, 2002, 12:31:12 PM »

This is easy....Put up the highest dipole (almost anything balanced) that will fit and put a good antenna tuner like icom, sgc, ect.. at the feedpoint.  Use large gauge antenna wire (>= #10).  If the antenna is close to or at least 1/4 wave (1/8 wave each side) you will have radiation very close to a full size dipole.  These antennas will work within to an s unit of a full size dipole even down to 1/8 wave (1/16 per side) if the tuner can match it.  Use no loading coils, let the tuner tune the dipole.  Solder everything.
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JA2WWE
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« Reply #4 on: March 25, 2003, 04:39:02 PM »

MA5V is not a bad choice- I have one and it works much better in hearing and tx than my ground mount mulitband vertical in the great majority of conditions. It is a real decent antenna for 10-20M DX'ing and if you get one out of a box without all the typical Cushcraft QC issues, you will be very pleased with it- It is light weight, has a great balin design keeping RFI non-existant, and is easy for anyone disabled to fiddle with vs other heavier antennas for HF. A bit tricky to build but hey, thats the fun right?  But it only covers 10-20M and limited to 250W and has only around 130KHz of bandwidth on 20M.  But with the 920's tuner, it's no big deal.  If you have to get on 30, 40 and/or 80M, realize most radial free multiband verticals with counter-poise's attached at their base, like the R8,  are only good on 10-40M. But ground mounted verticals covering 10-80M, like the Hustler 6BTV, or Butter HF9V, work as well with just a few short radials attached and are typically quieter.  BTW, radials laying on the ground do not have to be cut to resonant frequencies...only elevated radials need to be...therefore, from a simplistic design standpoint, I would suggest the Butternut or Hustler vertical antennas for 10-80M with at least 12 radials cut to any possible length (the longer, the better) or stay with a MA5V if 10-20M is your only need- Avoid mounting anything on your roof- Big Mistake- And forget wire antennas in limited space environments.  They are horrible for RFI and work poorly unless elevated significantly above ground- Oh yeah, Gap's Titan works well 10-40M with 100KHz for 80M but the counterpoise takes up a lot of room that is poorly represented in their advertising diagrams. Many come back because the base foot print is just way to big for limited space environments- 8 feet by 8 feet......64 sq feet in other words-Screw driver antennas with a few radials are ok, but basically good on the low bands for mostly stateside contacts and are limited in power input- The Gap can take full Legal except on 80M where it is limited to 600W.  The MFJ loop is a fun toy, works very well on 10-20M, a real DX'hound, but has a problem keeping resonant after being set on a particular band and tends to fall apart after about a year of medium use. As do most other Hygain products since Martin junked the company's QC. GL- 73  Yushi    
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N6AJR
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« Reply #5 on: May 05, 2003, 10:09:20 PM »

I would reccommend a ground mounted hustler %band vertivle  ($149 at HRO) and mount it as far away from the trailer as is resonable.  I have mine in the the back yard not 15 feet from my stucco ( chicken wire) house and have made several thousand contacts on it with good reports.  

It is not a 6 element monobander at 80 feet but it does work pretty well for me. I tried it with the radials and they didn't make any difference so I pulled them back up.

 You take an 1 1/2 inch pipe  4 feet long and pound it in the ground 2 1/2 feet. Mount the antenna on that  and make a 6 to 10 coil  6 inch coax balun and run the wire into the shack.  If you need to take it down for adjustment it is loosen the bottom U-bolts  and remove the top ones and lay it down ,it only weighs a few pounds and goes up and down easily.  All and all not a bad deal. and it looks pretty good too, nice and clean looking.

 If ya need more hang a 80 meter dipole in the trees.  remember any antenna is better than no antenna at all.  

73  tom N6AJR
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N6AJR
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« Reply #6 on: May 05, 2003, 10:10:17 PM »

oops

make that a hustler 5 band vert.  (5bvt)  obiously I ain't much for typing.. tom N6AJR
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N6AJR
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« Reply #7 on: May 05, 2003, 10:11:27 PM »

and a tuner  preferably a cross needle   easier to use.  tom ( again)
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KE4ZHN
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Posts: 140




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« Reply #8 on: May 08, 2003, 03:39:43 PM »

I can certainly see where you have a serious antenna challege on your hands working with such a small lot and restrictions on top of that. I did a little reasearch on my own, and found a company in Germany that makes an antenna called a GP 160/10 vertical. The manufacture is called "Titanex" you can find them here http://www.titanex.de/frames/main.html This vertical is a 9 bander! Although it is rather tall at 41.4 feet, it covers 160-10 mtrs! For 6 and 2 and even 440, any of the Diamond triband verticals would work reasonably well. These are very small and you could easily put one up on mast. You may even elect to put up a small 3 element yagi for 6 as they are quite small. This Titanex antenna even features a tilt over base for easy tuning and mounting. I didnt read the whole spec sheet on the antenna, but I believe its designed to use ladderline as a feeder. This would make use of your tuner either in the rig or your external. Although I know of nobody using one of these, it sure would solve your problem of maximum bands in a vertical. This antenna isnt very heavy according to the specs (17.6 pounds) and Im sure you can order one through Titanex. Their contact info is posted on their website. According to the website, they even provide the radials to make this thing work.(wire type, not metal stingers) You may want to give them a call or drop them an email and get some info on this antenna. Maybe if you posted a query on some of the amateur newsgroups, you could ask europeon hams who may be using one of these if its any good. If it lives up to its claims, this may be your ticket to all band HF with one vertical. Good luck!

                                         DE KE4ZHN  
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K3ANG
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« Reply #9 on: May 18, 2003, 12:21:16 AM »

Go to http://www.naceplace.com/ppel98.html
Check the Butternut that's mounted to a TV-Dish actuator setup to automatically raise and lower the antenna.  While you're there, check out the antennas on the other "highway assault vehicles."
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