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Author Topic: Rigid Dipole using Hustler Mobile HF Antennas for Apartment in the Bronx  (Read 19108 times)
WB6BYU
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Posts: 13029




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« Reply #15 on: November 14, 2012, 01:24:07 PM »

If you just want to get on a narrow section of 75m, then putting a shunt matching
coil across the feedpoint should allow a good match to coax.  You can leave the
coil in place and operate other bands by changing the resonators.  That would allow
you to operate without an external tuner.
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KQ6Q
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Posts: 965




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« Reply #16 on: November 16, 2012, 09:48:36 PM »

I use Hustler masts and resonators, vertically on a metal roof, and a Hamstick dipole on 40m horizontal.
The KW hustler resonators are pretty heavy - recommend hamstick dipoles for whatever band you must work,
just tune them for your chosen freq. Your matchbox will give you a bit more useable bandwidth
 If you must have all bands, either a buddipole or the SuperAntennas equivalent will give you all the bands,
for a larger investment - but you'll have to pull it in to change bands.
A warning on the adapters to use more than one hustler resonator on a mast. I've tried that, and have a cautionary note.
Do not put a combination of resonators on the plate or the same feed where one band is 3 times the freq of the other.
I had 80, 40, and 30 meters on a plate, and the 30 meter resonator burned out. I have 20-18-15-10
resonators on another mast (two adapter plates) and it worked fine, until I put a single mast with a 40 meter
resonator on it, on another mag mount, with a t-connector in the coax feed. the 15 meter resonator burned out!
I've since gone to a remote coax switch so I don't have to parallel the mag mounts, just select them one at a time -
my wife 'asked' me not to make any more holes in the side of the house to run coax!

Good luck!

Fred, KQ6Q
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W5WSS
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Posts: 1652




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« Reply #17 on: November 17, 2012, 12:33:42 AM »

I just relocated and have to use an indoor antenna sort of a mixture actually. I built a vertical doublet. The tuner is a wide range T-match with a 1:1 current balun and a deskserving as a platform is perfectly located or aligned in that I can center feed the antenna.

The operating position can and is far removed from the antenna located in another room since the coaxial cable connecting the equipment to the antenna is in the tuned zone and operating in a matched condition.

The tuner is directly connected to the center of the antenna or as stated another way the two halves of the antenna directly connect to the balanced terminals of the T-match.

The Tuner is at the center of the vertical doublet and the balun is integrated but is a retrofit balun design brand and there is no coaxial cable or balanced line feedline.

The topmost wire is driven by the center conductor and travels vertically upwards to the interior ceiling.

The bottom wire travels downwards along the outside of the exterior wall and is deadended using an non conductive Teflon anchor.

Just thought to share the ideas.

The antenna is long enough to be utilized on 20m-10m where I expect longer distance utility via skywave outside North America.

Perhaps the aforementioned concepts can be adapted for your location.

For the leg that drops down outside:

I matched the wire insulation color to the exterior paint white.

The solution is simplified and stealthy while following best performance convention and very inexpensive from a second floor shack.

 
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W2WDX
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Posts: 188




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« Reply #18 on: November 18, 2012, 03:11:40 AM »

Trust me if could go the wire route indoors I'd go that way. Unfortunately, nothing will come into this building. It's a concrete and steel high-rise and inside we can't even get cell phones to work until we had an internal cell phone "repeater" put into the building. Indoors it's an RF free zone.

I was kidding about using the multiple Hustler resonators. I will not need that. I can just swap out the coils easy enough.

Just for giggles I ordered a couple of those MFJ 75m fiberglass jobbies, just to do some experimenting.

I have just completed the dipole mount. It uses a 2"x 8" Delrin bar stock with 3/8-32 3" long  steel thread inserts. It gets mounted onto a 8" x 10" .25" thick aluminium mounting plate with 4 DXEngineering 2" SDS-200P Super-Duty Saddle clamps. (http://www.dxengineering.com/parts/dxe-sds-200p) I like these clamps for this application because they have a 1" wide flat surface completely around the Delrin (vs a 1/4" circular rod like most clamps) which should reduce stress on the mount for the antennas. Unfortunately they are mondo expensive!!! But I plan on having this dipole for a longtime (using it for field day and mobile DX stuff, etc). This plate also has the two SAD-200A clamps to mount it on a 2" masting perpendicular to the dipole.

One of my many concerns is the metal plate near the feed point adding capacitance. (Might be useful if there is an inductive reactance component) I will have to see and can always change to some poly/composite plate, if need be. I also have four of the DX Engineering Resin Support Block Clamps RSB-I20000 (http://www.dxengineering.com/parts/dxe-rsb-i20000) just in case the aluminium clamps present a similar capacitance problem. (Once I get around to it I'll take some images and post a link. It's a nice dipole mount, if I say so myself)

Now I do realize this makes the feed gap about 8", but since the feedpoint impedance is probably going to be on the low side of 50ohms anyway, this may actually raise it up a bit. Sort of like the idea of a "delta match". I'm gonna play around with this and see what happens. I have decided to use LMR-400 and a 1:1 balun (Balun Designs LLC #1116ds) which I happen to have but never used. Nice low-band current balun. I just want to use it (since I have it anyway) for common-mode issues, if any.

Now the trick is to get the antenna resonant, tune out whatever ever reactance I may have (either with caps or inductors depending on which type of reactance I have) and get it as close to 50 ohm impedance as practicable. Then connect the balun and coax and try it on air. I'm gonna work with the MFJ toys first and once I see what's going on there, use the experience to go onto the Hustlers.

On 75m I usually only operate in a 50kHz range anyway so narrow bandwidth isn't a problem. On 20m ... hmm ... that may be a challenge. We shall see.

See it's funny how this goes. I didn't want to spend money (I have it, but that's only because I am a cheap SOB in the first place). But I get on a project and whammo!!! Never fails!!!

John, W2WDX
« Last Edit: November 18, 2012, 03:37:00 AM by W2WDX » Logged

W2WDX
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Posts: 188




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« Reply #19 on: December 04, 2012, 03:31:17 PM »

Hi again,

I thought I would post an update to my problem ... A wonderful solution has presented itself ... completely due to desperation on my part!

I have been going through everything I could find on the web about this issue. I've been at this for weeks, everyday. I found that doing anything like this will give me an antenna system that just wasn't efficient enough to make me happy.

So ... out of shear desperation I went to the building superintendent and asked about the possibility of putting a dipole up on the very top of the building. It's a twenty-five story build on top of one of the highest hills in the Bronx, NY. The roof is rectangular in shape when viewed from the top down, and measures about 320' by 130'. A large structure is located in the center and it rises about 30' high above the concrete roof. It is brick.

Well ... I figured it couldn't hurt to ask, thinking that no way in hell he would be agreeable to it. Well, it turns out his two brothers are both Hams. He never bothered to get a ticket but totally understands my need and my desires. He said, "Sure ... What do want to put up ... a dipole. I'm not sure you should put up a Yagi, but I see no problem with a dipole. Plenty of room up there for a big one." I was being calm and collected on the outside, but inside I was going, "HOLY CRAP"!  Shocked

Then he hit me with this. "You of course will have to put it through the board of directors of the Co-OP and get its approval. I'll come to the meeting if you like". Oh oh!

Well ... I just got back from the meeting. Two of the members where once Hams, and another two had the experience of being in the Caribbean through hurricanes and thought having a Amateur Station in the building would be a good idea. Especially "... after everyones recent experience with Sandy". The board approved 6 yea, 2 ney.

They said I would need approval from a PE (State certified Professional Engineer), of which I happen to be one. I showed them my certificate and they said that's great, go right ahead. I made them put their decision in writing and we all signed it. MINT!

So now ... I am planning a 300' doublet (inverted V) with 450ohm ladder line tuned on my Johnson Kilowatt Matchbox. It will be using steel copper clad aircraft trailing antenna wire. The wire has three groups of seven strands woven together then twisted into one cable .162" in diameter. This weave makes the cable much more flexible and easy to handle than a 6 AWG solid copperweld would be. Extremely heavy copper plating allows for wear and tear as an antenna. Break strength is about 2200lbs. It gets a bit windy up there, so I think this will be a good choice.

I am currently working out the finer details like the center insulator and mounting issues. I will be putting the antenna under a bit of tension to reduce droop and movement, so the mounting has to be substantial. I'm going to look at some commercial installations tomorrow for the HF system used by the local ATC here in NY used for aircraft communication, to look at its mounts and systems.

The design also calls for both large bleeder inductors (DC static discharge) and full size horn gap static/lightning dissipaters. The system will be grounded and bonded to the steel structure of the building itself. An image of the horn gaps can be seen here.

Horn Gap Dissapaters

The feedline will be brought down the side of the building along the brickwork and through feed-thru's going into the wall just outside a window. The Johnson Matchbox will be on the other side of the wall, just a few inches from the feedthru's. The wire will be terminated with connectors on the outside to allow the ladderline to be completely disconnected during a storm. No matter what kind of protection devices, or how large, disconnection is still the best way to prevent lightning from entering the building.

The superintendent is going to help me install everything when the time comes and is actually interested in seeing it done well and how well it will perform. DAMN! I got lucky on this one. So in a few months I should have a big balanced doublet about 160' above ground level.

So much for the balcony idea.

John W2WDX
« Last Edit: December 04, 2012, 03:41:18 PM by W2WDX » Logged

WB6BYU
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Posts: 13029




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« Reply #20 on: December 04, 2012, 04:15:16 PM »

That's great!

I'd recommend a bit of research or modeling on the expected radiation patterns
of such a long antenna before you put it up, however, as it will have various
lobes and nulls, especially on the higher bands, and you may find that you have
a null in a desired direction.

But it should be good for NVIS contacts on 80m and 160m, specially if there is
a metal roof underneath.

(I have run into problems with metal roofs before - an 80m dipole 10' off of
a large roof had a very low feedpoint impedance.  I think we added a 1uH
coil across the feedpoint for a beta match and that improved it.)
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W2WDX
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Posts: 188




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« Reply #21 on: December 05, 2012, 08:03:07 PM »

It's not a metal roof, it's poured concrete. Obviously it has steel structure underneath. It's a typical 1960's era high rise.

I'm not to concerned about patterns, and I don't think models accurately predict patterns off the top of narrow concrete buildings anyway. There is no way to predict the reaction to unknown I-beams, wiring, railings, the slope off the building and down the hill I'm on. My experience tells me, having had antennas in similar situations, that the models are way off and the patterns are more like an antenna on top of a tall hill with sharp cliffs or off a very large tower. I think the models tend to predict much higher ground losses, to very great degree, than actually exist in this type of installation. A metal roof is a different situation, of course.

The launch angles are fairly long, considering the narrowness of the building on the broadside, and the hill sloping down sharply away from the building, especially towards the west. So I suspect ground losses are not anywhere like a metal roof building on a flat terrain. I think it is more like a dipole with its center mounted at the top of a 250' tower on flat terrain.

The antenna is basically a double extended Zepp. As I'm sure you know, a DE Zepp is a dipole consisting of two collinear 0.64 wave length elements fed in phase by a balanced feed-line and Transmatch. I gave approximate values before. To be more specific, I figure around 309'-311' antenna length (depending on trimming) and the ladder-line feed length works out to be around 95', so its a rather good 80m double-extended Zepp. It should also have very good characteristics on other bands, except 160m (which I don't generally use). Like I said before I'm using a Johnson Kilowatt Matchbox, perfect for this type of antenna.

However all that being said we shall see. I am more concerned about the mechanicals of the design. I want this to be excessively durable. I don't need a 150' long piece of wire dangling precariously from the building if it breaks. That's the reason for the .162" aerial copper-weld steel wire with the 2200 lb break strength rating. Much lower chance of it breaking and better loss figures particularly at lower frequencies at these lengths over standard 12awg copperweld.

John
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N2CJ
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« Reply #22 on: December 28, 2012, 07:03:06 AM »

Have you considered roof mounting a remote antenna tuner, such as the MFJ-998RT, and feeding it from the shack with coax? That would be an even more elegant solution than tuning the ladder line with a matchbox.
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AC4RD
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« Reply #23 on: December 28, 2012, 01:09:23 PM »

"Sure ... What do want to put up ... a dipole. I'm not sure you should put up a Yagi, but I see no problem with a dipole. Plenty of room up there for a big one." I was being calm and collected on the outside, ... everyones recent experience with Sandy"[/i]. The board approved 6 yea, 2 ney.

John, that's FANTASTIC.  You worked within the system, followed the rules, and you've got a BIG payoff!  Smiley  Congratulations!  Please post a follow-up when your antenna is up and you've had a chance to try it out!
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W9FIB
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« Reply #24 on: December 28, 2012, 02:05:56 PM »

I know you didn't want to spend any money so this is for the rest of the folks.

JDC Antennas from Canton Ohio makes some great antennas that would work great in an apartment set up. I was next to their booth at Dayton for a couple years. Great people, and nice products. Check em out!
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W5WSS
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Posts: 1652




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« Reply #25 on: February 10, 2013, 04:11:43 AM »

I know this is a late reply, I think since you CAN go out away from the balcony try adding some sloped radials parallel to the balcony length fan them in an axial route traveling sloped downwards towards the deck/or floor of the area.

End feed the Mo-1 and  attach the shielding to drive the radials work out the wx proofing of the connections etc.

The quarter wave pushing against the radials will then be center feed and more effective the higher in frequency where the radials are closer to quarter wave lengths themselves, whether you consider the system to be an elevated or ground mounted only as a definition, is only relevant to the completion of the system relative to common mode displacement currents and system balance,

The best option would be to match the floor dimension of the balcony with a conductive mesh mat and connect to the system under some resonated radials use resonators try it from that high height you may be pleasantly surprised.
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