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Author Topic: HF Antenna for confined space  (Read 3342 times)
K8POS
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« on: May 26, 2008, 07:43:30 PM »

I am trying to help two local hams who are blind with HF antennas for 80, 40, 15, 12, 10 meters.
We have tried Isotron antennas with very little luck.
They are on the second floor of an apartment complex so anything has to go on the balcony.  The available space is approx 30' long X 7.5' tall x 3' wide.  The balcony is made of concrete (rebar and mesh in it I am sure) and has a 4' high railing.  I stripped back about 5' of coax and hooked that up to their Kenwood and it did way better than the Isotrons. Even hooked it to the railing before I left for the night.  HF is not my forte, but there must be a way to string a long wire or dipole of some sort that would do better for them.
 
   Bob
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AD5VM
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« Reply #1 on: May 26, 2008, 09:09:05 PM »

Well, not a whole lot you can do here. 30ft long is enough to put up a great 20 meter antenna. The Par Electronics EndFedz dipole:

http://www.universal-radio.com/catalog/hamwire/4456.html

 It's 33ft long and is fed on the end. That's assuming your space is horizontal. If the space is vertical, then you're golden, just slap up a Hustler 5BTV for $150:

http://www.dxengineering.com/Products.asp?ID=141&SecID=16&DeptID=8


 cut a single counterpoise 1/4 wavelength long for each of the five bands and run them around the floor of the balcony and also attatch the ground to the metal railing. Another alternative would be using a 30 foot long wire connected to an auto antenna coupler like these:
(for any radio)
http://www.universal-radio.com/catalog/hamtune/1238.html

(for newer Yaesu rigs)
http://www.universal-radio.com/catalog/hamtune/0643.html

(for most Icom rigs)
http://www.universal-radio.com/catalog/hamtune/3702.html

And then yet another option which is great for 10/12/15/17/20 meters is the following:
http://www.twantennas.com/


I'm thinking if cost were not a big factor, I'd go with the TW antenna sitting on the ledge, and then I would also use a coupler/30 foot wire, if you connect a few radials and the metal railing to the ground side of the coupler (the coupler will go outside and connect directly to the longwire) then they should be able to use it on 80-10.

If cost is a big factor, I'd just try the coupler by itself. Both the TW and the auto coupler would be a good choice for blind hams, with the TW you just push one of five buttons to change bands and with the coupler, you just push the tune button on the rig.

I don't think an MP-1 or a Buddi-Pole would be good because they would have to change taps or move coils to change bands. Also a motorized screwdriver would require them to be able to see the SWR meter for best tuning but that may be worth looking into, again with the screwdriver it would require a radial for each band and a good ground connection.

Tarheel makes some good ones:

http://www.tarheelantennas.com/mobile_antennas

And the last option I can think of for a person in this situation is a remotely tuned magnetic loop.
MFJ makes one that gets good reviews:

http://www.mfjenterprises.com/Product.php?productid=MFJ-1788

The problem with the tuned loop is that it would make it kind of hard to tune without being able to see the SWR meter. But it would be much easier than a screwdriver because the Q is so high that the antenna is totally deaf until it comes into resonance at the operating frequency so when the band comes alive, it's close to tuned. But I would still look at the TW or the coupler ideas first.

Good luck!
73
Larry
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AD5VM
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« Reply #2 on: May 26, 2008, 09:19:45 PM »

Okay, I read your post again, I see the space is horizontal. Really the biggest problem with the apartment balcony is 1)RF shielding from all the rebar, stucco (wire mesh) etc... and then RFI from all the people and their electronics. If you could get a tiny 26ga copper-clad steel wire strung from their balcony to a nearby tree and then use the SGC coupler/radials mounted in the balcony, I think that would be the best bet. All bands, one touch tune, and decent performance with good ground and radials.

Even if all you can get is 23ft of wire in the clear, it should tune all bands from 160-10 meters.

http://www.thewireman.com/antennap.html
(scroll down to item#534)

http://www.universal-radio.com/catalog/hamtune/1238.html
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KB9CRY
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« Reply #3 on: May 26, 2008, 09:21:23 PM »

Forget 40 and 80 at that location.

Get them set up with a local contester to be guest ops.
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VA7CPC
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« Reply #4 on: May 26, 2008, 11:44:28 PM »

I hate to throw cold water on the idea, but . . .  There's a lot of grounded metal on the balcony.  

I had decent (not "good") results on 20m with a 16' aluminum "flagpole" tied to my balcony, using the balcony railing as a counterpoise.  Used an LDG Z-11 Pro autotuner.

That setup, with 100 watts, gave me pretty consistent coverage of the western US from Vancouver, BC.  I had occasional DX to South America, Japan, Alaska, Hawaii.   Using PSK31, a friend and I had very consistent contacts Vancouver BC <--> San Francisco CA.

The balcony faced SW; I was deaf to much of the US.

The flagpole was way, way better than a 20m Hamstick.  My Hamstick experience was dismal.

I think 40m is a lost cause.  My autotuner could tune the flagpole to 40m, but few people could hear me.

The only compact antennna I've heard good reports about, from a balcony location, is a magnetic loop.  I agree with a previous post -- a thin wire, shot into a nearby tree, using the balcony as counterpoise, is likely to give better results than other alternatives.

OTOH, VHF would be easy -- there are probably many repeaters within 30 miles, and you can hit those with a balcony-mounted 2m vertical dipole (almost invisible) and 5 watts.  

     Charles
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W8JI
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« Reply #5 on: May 27, 2008, 04:23:13 AM »

Bob,

If I was in your position I'd tune some sort of wire or antenna against handrails or whatever metal I could bond together on that balcony. The antenna might even be a multiband mobile antenna worked against a counterpoise.

If you can't use the handrails then lay down some foil or metal screen under carpet or a big mat as a cover, and use it as the ground or to help the ground.

The ideal thing would be to get a wire or antenna off the balcony. I work hundreds of Japanese amateurs in apartments that use fishing poles with a wire run down them as an antenna. I'd look at what some of the Japanese amateurs do.

73 Tom
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W8JI
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« Reply #6 on: May 27, 2008, 04:25:18 AM »

By the way....

 I've worked Japanese stations on 160 meters using fishing pole antennas....so don't count out any band.

73 Tom
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K8POS
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« Reply #7 on: May 27, 2008, 04:26:22 AM »

As I previously stated, I have little knowledge when it comes to HF.
Given that 1/4 wave on 80M is close to 60'.  Would a wire antenna have to be straight?
Could it be strung horizontal top to bottom of the balcony  like this /\/\/\/\/\/\ or can it be folded back.
run 30' across, drop down a few feet and then run back the other 30' ?
I know that given matching coils and balums, a 6" screw could be made to resonate, it just would not be efficient.  10-15 meters should not be that big of a problem, there is room to hang a 1/4 wave wire and use the balcony for the counter poise.  I think they really want the 40 and 80 meters.
The Kenwood rig they have has 2 coax inputs and some sort of built in antenna tuner.

 Bob
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KZ1X
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« Reply #8 on: May 27, 2008, 05:14:24 AM »

See if you can lead a meeting with some guys from Thumb:

http://w8ax.com/

They may be able to assist with this sort of thing.  
Not too far away, and a really great group.
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K8POS
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« Reply #9 on: May 27, 2008, 05:58:13 AM »

Yes I have already contacted them, I am a club member!
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W8KQE
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« Reply #10 on: May 27, 2008, 11:14:41 AM »

How about a 'Tak-Tenna' or a 'Buddipole'?  They seem to work fairly well for compact/portable antennas.
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N6AJR
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« Reply #11 on: May 27, 2008, 11:28:35 AM »

try a set of ham sticks with a good  rf counterpoise, r perhaps one of the screwdirver antenna, with an autotuner and a counterpoise.
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WA3SKN
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« Reply #12 on: May 27, 2008, 01:31:22 PM »

OK, you are the second floor.  10 and 12 meters should not be a problem, since you probably can hang a wire 15-20 ft before you reach ground.  15 meters might be reached, but the ends might have to be folded.  Also, 10, 12, and 15 meters can be set up horizontal on that 30 ft balcony too! You didn't mention 17 or 20 meters... they are the daytime workhorses at this time.
Now 40 and 80 meters are going to be harder.  But you could take that 30 ft balcony and string a wire back and forth several times.  Its better than a mobile whip! You could also fit three 10 ft sections og 4-6 in. PVC horizontally on that balcony... 30 foot of space-wound loading coil would help to match a lot!
Now most of these would need to be used with a tuner, either manual or automatic.  I would try one of the auto-tuners for the "ease-of-use".
See if any of these ideas might work!
Good Luck, 73s.

-Mike.

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KI6NUJ
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« Reply #13 on: May 27, 2008, 09:39:21 PM »

I am in pretty much the same boat as you. I have a 10 feet high, 15 feet wide and 6 feet deep balcony on a second floor apartment on a hill.

I have a MFJ-1786 Magnetic loop antenna that works great for continental US from here in San Francisco. When the 20m band is good, I can be heard with a 59 signal in the mid-west with 100 watts. I can easily copy signals from the east coast but haven't worked anyone there yet since it has been just a few days since I got this antenna setup. The loop is mounted horizontally on a tripod with the mast just 5 feet off the balcony floor. The stucco has wire mesh and the roof five feet above the antenna has metal flashing. Not a nice place for an HF antenna.

Now, I am hunting for something to work with on 80m and 40m. I am trying hamsticks clamped to the metal railing on the balcony but haven't had any success yet. I can hear people from most neighbouring states but no one hears me. I am awaiting a miniVNA analyzer to better tune the hamsticks and see if it works.

The TW Antenna option looks good though it is pricey.

So far I haven't figured out any way to throw a wire to any nearby tree without attracting some attention (got a few really nosy neighbours including an old lady who is mostly looking out of her window!!)

I think we should create a restricted space / apartment HF antenna group on yahoo or google :-)

Please do share with me about what works for you - wv6u_at_wv6u.net

73,

- Siddhartha


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