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1-10 of 16 messages
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Options for short attic dipole
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by KG4NMC on August 26, 2001
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I'm slowly approaching the point of investing in an HF rig. Due to the wonderful covenant restrictions so often talked about, my only options for antennas are what will fit in my far too small townhome attic. I already have a 2m/70cm vertical up there, which has worked wonderfully. Not I'm starting to wonder what sort of HF dipole would fit. My attic is not much more than a crawl space, and I can't fit anything over about 15 feet long. This puts a limit on the sort of antenna that could be used.
The first option I considered was the Lakeview Company Hamstick (www.hamstick.com). This was a nice, low cost antenna option (about $65 w/ dipole mount), but each antenna set is only good for one band. I don't really care for the idea of crawling up in the attic every time I wish to change bands.
Next, I started looking at the Spider Antenna (www.spiderantenna.com). They also sell a dipole option, and their antennas support from one up to seven simultaneous bands with per band tuning at the antenna. This looks quite nice, and many people speak well of their antennas, but the cost hurts a bit. It runs from nearly $350 for a four band option up to over $650 for the full seven band option. Pretty steep.
I'm curious what other people have done for a multiband attic dipole antenna. Has anyone come up with a great solution for a reasonable price? Also, has anyone actually tried one of the Spider Antennas in the attic? What sort of performance did you see? Your feedback is eagerly awaited.
-- KG4NMC (http://delbert.matlock.com/kg4nmc.htm) / Delbert
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RE: Options for short attic dipole
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by KB9UMT on August 26, 2001
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Hi Delbert!
You did not say if it is 15 wide by 15 long by 15 high or what size overall you have to work with...?? Anyway there are ways to HF ham in small places. Do you have a window or balcony? Is your building siding?
You might try the cheapest thing to do first and see what you can tune or work with just a wire loop all around the attic to a good tuner.
Here is a site that has a dipole you can build for little of nothing and I think you might be able to fit in your space:
http://www.nerc.com/~jdegood/coaxtrap/
Or maybe this site has a view tips for you:
http://www.cebik.com/ant2.html
Now how about some loop antennas that are for 10-30 and 15-40 meters...MFJ sells them and they are 36" loop antennas that fit almost anywhere...not cheap but go here to see them:
http://www.mfjenterprises.com/products.php?prodid=MFJ-1786
I have an old AEA Isoloop 36" loop antenna and have used it and experimented and have made many contacts on it..works great on 17 and 15 meters for sure!
Now one other solution is the Isotron antennas and you can see them here...the fit in very small spaces for the lower bands that you might not be able to fit in your space...here is the website:
http://www.rayfield.net/isotron/
And by all means go to the EHAM review section and read up on some of these antennas:
http://www.eham.net/reviews/detail/174
http://www.eham.net/reviews/detail/611
http://www.eham.net/reviews/detail/311
There are other things to suggest but this should get thinking for now. Can you give us some more detail on your attic..exact demisions, 2nd floor?, area outside, trees?, siding on building? etc...
73's and hope to hear you on the bands soon de KB9UMT (Don)
BTW I just moved and I had no antenna up and could not stand it for more than 3 days so I just took a random wire (appx 60 ft) out the basement window up about 4 feet off the ground over to a support and made many psk31 contacts to Europe on 20 meters and checked into a few nets on 40 and 80 meters so just experiment some...SWR and the like may not always mean that the thing will not radiate a signal with a good tuner!! Watch the RF limits though and the TVI....experiment!
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RE: Options for short attic dipole
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by WB2WIK on August 27, 2001
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I'll ditto the comments about the MFJ "Hi-Q Loop" antennas. They are a bit quirky, but they do work well and provide a lot of "bang for the buck." With the built-in (attached to, and part of, the antenna) tuning unit and remote tuning control box (also provided with the antenna), it only takes a minute or less to change bands and re-tune, and once this is done, the antenna efficiency is remarkable for its size.
They also seem to work just about anywhere: Low, high, indoors, outdoors, etc. I've experimented with one quite a lot and found it worked quite well just sitting atop a 6' wooden stepladder (on the top step) sitting on the patio -- in fact, in this instance, it worked better that way than it did when installed in the attic, about 35 feet above ground (but indoors).
73 & let's hear you on the air!!
Steve WB2WIK/6
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RE: Options for short attic dipole
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by N4VI on August 28, 2001
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Hi Delbert,
As mentioned by kb9umt, a better description of your attic is probably in order.
What bands do you want to operate? 40/20/15 and 10? Do you desire 80 and 160?
I have two hf antennas in my attic:
1. A cushcraft D3 dipole for 20/15/10. I just checked the cushcraft catalog and it specs a length of 25'.
However, I don't believe mine is 25' long, it's more like 20'. I can double check if you are interested.
2. For 40m I have a 22' long dipole made out of copper pipe from Home Depot loaded on each end. The
loading on the ends is an 'X' bracket made of wood 1x2" with wire wound in a spiral. It's similar to the top-hat loading you will see on Cebik's web site except it is wire wound in a spiral.
I'll be glad to supply additional information and pics if you are interested.
73
chris, n4vi
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RE: Options for short attic dipole
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by WB5NHL on August 29, 2001
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I am in exactly the same position you are in and gradually working various options to see what gives me the best antenna. I agree absolutely with starting with the least expensive. $$$ doesn't necessarily correlate with performance. My first and current experience is with a borrowed AEA ISOLOOP (no longer available but MFJ loops are equivalent). On 20 meter PSK31 with a 3 watt PSK-20 this antenna has gotten me 44 countries in about 6 months of operating. Another thought I've had is to use a St Louis vertical on my deck. This antenna would be put in place only when I want to operate (maybe with a small flag since my development seems to be flag tolerant). Thus the vertical doesn't qualify as a structure anymore than my neighbors deck mounted flag pole. An added caution that I have fixed in my townhouse attic was the use of foil-backed foam insulation. I have removed this insulation and replaced it with better R rated (for XYL considerations) non-foil insulation. I am hoping removing this foil improves the loop performace at least some directions. Unfortunely I will just have to live with any foil panels in the basic townhouse structure hi hi.
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RE: Options for short attic dipole
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by KG4NMC on August 30, 2001
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Several people asked for more details about my attic in order to make an informed suggestion. Let's see if I can paint a better picture.
When I say I don't have much upstairs, I'm not being scatter brained. My attic isn't much more than a crawl space. The full running length from wall to wall is about 15'. The working width is about 10-15', but only about 6-8' is easily reachable due to the ceiling structure I have to work around. Vertical is a real mess. There is an upper and lower area separated by cross beams for the rafters. The upper area is about 3-4' high and triangular shaped. The lower area is about 3' high and rectangular (about 4' wide).
The town house has aluminum siding, so any antenna structure must be completely in the attic. My current VHF/UHF vertical up there seems to work quite well, so the roof structure itself will hopefully not be a problem. Fortunately, there is no 'metal backed' insulation up there which will save me from having to do a lot of work with that.
Rotating structures are not going to be possible with the rafter structure in place. Anything installed will have to be a fixed position. At least, with the dipole, I should have good east to west coverage.
Thanks for the suggestions so far. Keep them coming!
--KG4NMC / Delbert
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RE: Options for short attic dipole
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by W8UR on September 5, 2001
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Put up a rectangular or delta loop using a remote tuner. You should be able to put up over 60 feet of wire by making a double loop. I've worked over 35 DXCC over the past couple of months using such an arrangement with 100 watts through an SG-230 remote tuner. I used PVC pipe and nylon rope at the corners to secure/insulate the wire.
Tuners at the transmitter don't work as well, because the high swr of an untuned antenna will cause large losses in the feedline. By tuning at the antenna, feedline impedance is matched, so there is very little signal lost. Using a loop antenna also avoids having to worry about running a ground from the antenna location.
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RE: Options for short attic dipole
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by KG4NMC on September 6, 2001
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Regarding the Delta Loop, that is one of the options I've considered. What initally turned me off of it was the cost of one of the better SGC tuners (around $600). I've also had trouble getting a good grasp of the radiation pattern for such an antenna.
Should the loop be horizontal or vertical? For a vertical loop, I would be very restricted on size (about 4' by 15'). With horizontal, I could get up to about 10' x 15'. My fear has been that the radiation pattern would be pretty much straight up.
The tuning issue has been important with me. What drew me to the Spider antenna was the on antenna tuning that would let me optimize the antenna for one area of the band (such as where the digital modes are) and then let the radio tuner handle that last little bit of optimization.
How susceptable will a loop be to the odd bits of duct work and wiring in the attic space? There is also the matter of my VHF/UHF 5/8-wave ground plane that shares the space.
I have to say, my biggest fear of the loop has been my lack of understanding.
-- KG4NMC / Delbert
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RE: Options for short attic dipole
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by N6AJR on September 16, 2001
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SGC now has a tuner in the $200.00 range the 229 i believe, soon to be going to around $239 or so.. not a bad deal.. any how that way you could put up a "dipole" of sorts zig zaging the wire as evenly as you can on both sides, or try it with coax and a tuner at the radio.. any antenna is better than none.
I also once put up a 5 band "multi" dipole a couple inches off the roof fed with a single coax, no balun. I had a 66 foot wire either side, a 33 foot wire on either side, a 16foot 6 inch wire on each side and an 8foot 6inch wire on either side. The signal see's the proper antenna as an antenna and the ones the wrong size look like a hi impeadence something or other.. this was literally on small wooden blocks just inches off the roof spread in a v shape, seperating each a bit from the other, as far as you can and still call it an inverted V. I used something along the line of kids play blocks to hold it up. My first contact was with a fellow on one side in Hawaii and the other in L.A. ( I lived in calif at the time.) if you have room this works with out a tuner, and put up what you you can.. this is invisible from the street.. there are a lot of books on Invisible antennas so keep your eye open.. and have fun Tom N6AJR
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First results in!
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by KG4NMC on September 27, 2001
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Well, for anyone still interested, the results are in. Early in the week my equipment showed up. I hooked a SGC SG-239 tuner up to a 58 foot loop of 12-gauge stranded electrical wire in the attic. This tuner was then fed from a 50 foot length of RG-8X coax to a Kenwood TS-2000 radio.
There is a fair amount of noise (which could be completely normal), but the whole thing will tune up from 10-meter all the way to 80-meter. In the first two days I've made DX contacts from Virginia to England on 10-meter and Italy and Israel on 20-meter. The very first night I even heard (but didn't try to transmit to) Kuwait using the 9K2USA call sign.
All in all, I'd call this a resounding success. The UHF and VHF antennas inside the loop don't appear to be causing any interference. I have very little electrical and no phone wiring in the attic, so this doesn't play in. The only metal ducts run straight vertical, so they don't appear to cause any trouble. As long as the tuner hold up, I should have several years of good DX'ing with the attic ensemble.
Thanks all for the help and advice.
--KG4NMC (Delbert, http://delbert.matlock.com/kg4nmc.htm)
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