Flexradio and OCF 80-6m multi-band (Windom) - thoughts/experience?

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Not yet an owner but seriously looking!
I live in a deed restricted/hoa area so an attic antenna is path of least resistance.  Two story with a peak of 30ft.  Upstairs attic fairly open except within it the cube/shell of my upstairs mancave/shack (just 1 room upstairs).  I can fit an OCF Dipole that spans 68 feet if I invertVee it and fold the ends by a few feet.  Can't quite get it to best mount of 35ft for SWR minimization but it will be close.

Question:  Is that a good type of antenna to feed a Flexradio to get band coverage across 40-6m?  I realize there's lots of options but looking to maximize the hearable bandwidth with such a capable radio and just don't yet have the need for dual antennas/diversity.  Or is there a better attic antenna for maximizing a Flexradio?

I'm liking the OCF/Windom so I don't have to have traps and can get the multi-band out of a dipole since it's unbalanced.  Mag loops look intriguing but don't quite cover the bands I want - maybe in the future.

I can't think it's a bad idea but looking for a blind spot in my research/logic.  Ideally someone who's done this and any learnings/concerns would be greatly appreciated.  

Thanks!
Dave


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Dave Egan

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Posted 1 month ago

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Bill English

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I have an OCF for 80-6m that has given me good results. Made a lot of QSO's on 30m using the ATU, not a bad antenna. I put it up mostly for 80 and 40, but have made a lot of QSO's with it on 6m. You won't be disappointed.  
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Dave

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Had a 80-6m OCF up for about 3 years with the vertical radiator. Tuned great 80-6. (with internal ATU) including 60m. Took it down because I moved. Of course, mine was outside up about 50'.
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Bill English

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I had one of those as well some years back, with the vertical radiator. It was up about 90 feet and worked surprisingly well. It was a good one.
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Wayne

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I have an amerirton sda100 1200 watt screwdriver antenna mounted on my roof. Its only about 6ft tall and remore tuned via control box from my shack covers 80m thru 6m all you would need is a few counterpoise wires from the base of ut across the attic, does really well on my roof and with just the antenna i get about 1.5 to 1 swr then i occasionally use the flex tuner to further match it to 1.2 swr or better. Had it up ther for over a year outside with no issues so in the attic it should do even better out of the weather. The only downside is it is about $450 new with everything needed.
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N8SDR

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An OCF with a vertical radiator isn't really an OCF its a windom
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Dave

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Did not know that. Learn something new everyday.
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Rick - W5FCX

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I’m using the Ni4l OCF Windom and it works very well. The Buckmaster is also quite popular.

Make sure you don’t have aluminum backed heat shielding in the attic, as it would negate your efforts (my new HOA house has it).

Inside the attic steer clear of large metallic objects and house wiring, if possible, to prevent SWR and RFI issues (even if it means not running elements perfectly straight). I’ve had severe issues with GFCI breakers popping on 40 meters above 75 watts.

Also if you’ll be running any power, antenna element insulation and clearance matters to prevent arcing and potential fire hazards. As always, verify maximum permissible exposure levels inside the rooms below the attic for safety, esp if running power, as the antenna will radiate inside the attic and beyond.

Good luck. Let us know how it works out.
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Dave Egan

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I've been eyeing the Ni4L as well.  I basically have a plywood deck but noticed two sections along the ridge that have aluminum foil about 1x4 ft - not sure why it's there but worries me for blocking part of the signal close to the balun.  The only other worry in the attic is the large volume of foil air duct (It's Texas) piled up onto the top of the mancave cube, a bit close to the peak....

I plan on a max of 100w but the concerns are valid to consider.

Thanks so much for the response and input!
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KF4HR

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OCF antennas work fine.  I tried an attic antenna years ago.  I wasn't impressed with its performance.  I switched to a flag pole vertical (well in the clear) and achieved considerable better reports.  Part of the issue with attic antennas are they are in fairly close proximity to house wiring, gutters, and such. 
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Dave Egan

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Thanks for the observations.  I suppose with an OCF I'd at least be on the air but with band conditions it might be quieter than I'd hope.  Ugh....  Great input - just what I'm looking for - real world input vs all the debates/information.  Thanks!
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N8SDR

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I have a 40M OCF and it works very well, HOWEVER- OCF's are prone to RF issues esp when there inside and near other types of metal objects, with that in mind I would recommend you build you own and use the Balun Designs Hybrid OCF balun, I currently use this balun as one leg on my OCF is only around 12 feet from an attached carport. and the other side horizontal except the last 4 feet which hangs horizontal over a tree limb ( using insulated wire), I find this balun which has a doubled Stacked design of a 4:1 followed by a 1:1 RF choke works very well in odd or less then optimum installs. And possible another 1:1 RF choke balun at the rig:  Give Robert of Balun Designs a call and ask his advice,  The best advise I can share  with you when using a OCF is the BALUN will Make or break antenna performance use a good balun there are many cheap baluns which when put under pressure such as you intend to do will cause high voltages on one side and possibly lead to saturation of the balun, you'll notice increasing SWR. The Balun Designs products are well made but there a bit more costly, again you get what you pay for.

https://www.balundesigns.com/model-4116-4-1-hybrid-balun-1-5-54mhz-3kw/
(Edited)
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Dave Egan

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Wow great stuff.  Thanks.  I'll check it out.  I wasn't aware of the RF issues so the 1:1 RF chock would be good input to have!

Thank you.
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Stan, K4SBZ

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I swear by OCF dipoles. I have three, 2 80-6 and a 160-6. The 80-6's work VERY well with SWRs  below 2:0 on most bands. I do not use a tuner other than the atu on my 6600M. They are easy to build. Use a good 4:1 balun at the top and a 1:1 at the shack. Even better at the top is an rfi choke. I have worked the world (DXCC) with 100 watts.
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Bill -VA3WTB

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I tried one for a while and found it to be noisy,,not sure why... I went back to my linear loaded 40 and 80m dipole.
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N8SDR

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Like SZawrotny- I have had very good results with OCF's but like I mentioned they require the correct and a well made balun to work well. If its nosier than you dipole hung in same location its the balun your using, a good well made balun will help negate noise
(Edited)
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AA0KM

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Search here on the forums:

Stealth antenna


Hoa antenna


TX antennas

Antenna for Restricted

And any other combination of antenna searching. 

Lot of user experience in the forums.

Good luck.

73 Jeff



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Mark WS7M

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Hi Dave,

I also live in an HOA and have managed to slide by with an outslide wire loop.  A large one actually 280 feet of wire strung between trees.

While I think we all do what we can do I suspect you will be disappointed with an attic antenna.  If it is your only option then so be it.

Another thing to consider is to buy simple wonder poles from Amazon and build yourself a 20m vertical for the back yard.  They are almost invisible and with a reasonable tuner you can load it up on 40m as well.

https://www.amazon.com/Shakespeare-TSP20-Six-Piece-Wonderpole-Fishing/dp/B000FFQOSW/ref=sr_1_4?ie=UT...

You simply run a wire up to the top of it and provide some radials, upto 16 would be great but 4 will do.  It can mount on a simple stake pounded into the ground.  

Just giving you some options!

Another reasonable option is the EF antenna. These work well:

https://myantennas.com/wp/product/efhw-8010/

You can mount the feed point near your house and run it as a sloper up into a tree.
(Edited)
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N8SDR

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Or make/buy a couple bird houses and build a tall wooden support for them staple the wire on the outside of it, place your ground radials and a 4:1 UNUN under at feed point and your good 6-20 M, Optionally you could use say a metal fence top rail for the support pole and some good PVC tubing and a mount for the base to insulate it from ground and load it up as well,  
(Edited)
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Dave Egan

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Mark-
Hmm..  I do have a 30ft peak and could do a sloper from there out to the yard.  It would have to bisect to trees (18ft) that are only 17ft apart.  They themselves aren't great for hanging wires from (Chinese Pistachios) and are not marked by a tall single structure like an evergreen or even a big oak.   I greatly appreciate the input -stuff I haven't yet come across and will research!

I do like the idea of having the wire outside of the house...

Thanks!
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Rick - W5FCX

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Yeah. Have had one breakage incident in 2 years but in Houston area ice is quite rare (except in our iced tea and occasional libation).

The most I have run is 100 watts. Anything more and I get GFCI breakers popping, touch screen lamp ghosts and whistling gun safes.

Signal reports are good, too :)
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Stan, K4SBZ

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Why use 26 ga. It has a breaking point of only 25 lbs. 18 ga - 280 , 16 ga 381, 14 ga - 550 lbs. 18 or 16 ga is hard to see.
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Rick - W5FCX

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It’s stealthy and strong enough. The key requirement in this use case is stealthiness, not strength. The wind load against #26 wire is negligible. It’s field-proven at this point.
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Ken - NM9P, Elmer

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You can use a length of mini bungie cord as a stretching strain relief and reduce the risk of breakage, too.
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Rick - W5FCX

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Interesting idea.  That's why I chose the 8 pound monofilament line as the insulator to bridge from end of #26 wire antenna elements to the fence - it stretches easily and rebounds with quite a bit of elasticity.  A bungee cord might be better except for how visible it is.

The one breakage incident I had was before I started using monofilament. I originally used 30 pound Spiderwire, which has virtually zero elasticity, because it was all I had available at the time.  After the break incident, I switched to the monofilament and no more issues since.
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Jim Ricker

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Dave
two thoughts. I served in the Marine Corps for over 30 years and used the following two antennas very successfully .

Dipole  running on the inside of the facia .  You can use small electrical tie/ties and a staple gun I  would use a small 1to 1 balun the size of a old film canister. I would use small coax with bnc on both end. Kept the power down to about 65 watts.Ran the coax back to the shack via a side vent.

A single wire from the roof to a supporting pole or tree in the back yard. I used small 16 gauge black wire. Yes it would break, Just restrung it . Watch your neighbor hood. If its retirement community and everyone is home all day. Do your work (safely) at night. If your neighbors all work during the day Take a day off and install NEVER NEVER do any major work on a  weekend everyone is home. 
Pushed my luck on this one and a neighbor turned me in. I was off the air for over a year. Also if you can a wire on the top inside of the fence these work great. 


Jim
K6CEF

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Stan, K4SBZ

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You can string wires around facia and fences around Christmas time without too much suspicion, as long as you add some decorations too. Plan ahead.
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Dave Egan

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Inside the fence is a great idea.  However half the fence has metal poles (Vertical) supporting the wood fence.  The other half is community stone wall...  Seems both would mess with the wave being emitted...
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Stan, K4SBZ

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True. That can be mitigated a bit if you keep in mind that only the short side of the antenna actually radiates. The loss might not be that great if you can position it well. And I'm not sure the vertical poles would hurt too much. The stone would block the signal in one direction (broadside).
(Edited)
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Ken - NM9P, Elmer

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??? Only the short end of an OCF dipole radiates? Where’d you get that? The OCF is simply a standard half wave at its lowest frequency, but since the feed is at the 1/3 point, (or 20% or 40% depending upon the particular design) the feed impedance is at anywhere between 200-600 Ohms. Not only for the fundamental frequency, but at most of its harmonically related bands. This is why the 4:1 (or sometimes a 6:1) current Balun is required. The balun enables the antenna to be matched at the higher impedance feed point on multiple bands...something that a Center fed dipole cannot do.

The whole antenna is active and radiates. The main differences between the two are:

1) feeding at a higher impedance point with a suitable balun allows multiband operation.

2) being an inherently unbalanced antenna, it also requires good feedline isolation to prevent common mode radiation in the shack, and common mode feedline currents disrupting the radiation pattern.

I have made my own OCF dipoles, using a Balun Designs 4:1 balun (about $75). I have used them as 80 and as 160 Meter dipoles, requiring only swapping the short section (45 ft.) of the 80 Meter Version for a long section (180 ft) to make it a 160 dipole. The 90 ft section stays the same — being the long section when designed as an 80 meter antenna, and becoming the short section when designed as a 160 meter antenna. (These measurements are approximate, subject to tuning). The antenna(s) have performed superbly for several years, being transformed several times for seasonal needs, in order to accommodate other antenna projects in my limited space.

I certainly agree that it is more economical to build your own. BUT...my first experiments with an OCF dipole were dismal, because I did not use a 4:1 balun, and the impedance mismatch killed its real usefulness.

The thing I first noticed with a proper design was how much better it received on the harmonic bands than a Center fed dipole. At the fundamental frequency they were both great, but the difference when going to the higher bands was staggering...

But taming the common mode RF was a little challenging until I wound some coaxial “ugly baluns” at each end of the coax. Problem solved...at least at low power.
(Edited)
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Dave Egan

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I'm thinking not only the 4:1 but also a 1:1 RF choke between the balun and the coax feedline to keep things out of the shack.
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Dave Egan

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Now I'm thinking outside is better than inside the attic.  I have a HOA wording that says "only approved by board" and no neighbors behind me so chances seem higher.  So OCF with coax feed seems best for what I want.  The latest questions are:

1)  I only have about 8 feet of clear space between brick veneer of house and the tree.  I hope to hang a messenger wire from peak of roof (30ft) to tree (15 ft) and midpoint the balun along that at appx 20 ft.  That would give me about 4 feet from brick.  Not perfect but not a showstopper right?

2)  I worry about having an eyebolt drilled into the veneer/stud at the peak and tied to a moving tree.  I will build a shock system into it but don't want to rip a weak part of the fascia or something else off with a big tree hanging off the roof.  Any ideas on a small mount idea that has some give?  Maybe I use Rick's monofilament tip for hanging the brick on the end of the messenger wire that will yield at some point beyond normal storm sway?  Or something up top that would give appropriately?

3)  I worry I can only get the ends of the antenna 9ft high.  The rope/monofilament from that point would go to a 6ft pole as that's the height of the fence.  9 ft seems a tad low - everywhere I look it seems 10ft is prudent.  The answer to #1 might sway hanging it closer and getting more height.  Is 10ft above ground for antenna end the target I need to stick to (100w max)?

Thanks all- really great bunch of answers and support - I appreciate it!


(Edited)
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Stan, K4SBZ

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Dave,

To compare an OCF Dipole with an end-fed: I bought a well-known EFHW 80-6 M antenna and put it up at the same height almost side-by-side with my 80-6 M OCF dipole. I did an A/B comparison with them between my station in northern Florida and a ham in Netherlands. He said my signal was "considerably stronger" on the OCF dipole than the end-fed. After similar reports, I took down the end-fed and have used OCFs exclusively since.

Regarding height: Several years ago, I lived in a HOA community and I ran my antenna along the bottom of the top rail of a 10 ft fence. I worked a lot of DX with PSK31 at the time.

I also used a 20 meter dipole in my attic successfully back then.

But the OCF dipole is my recommendation. If you don't have room for an 80M, use a shorter 40M at 66 feet. Be sure to put a 4:1 CURRENT balun at the top feed point.

If you can, build it yourself. They are very simple and inexpensive. Just wire, insulators and a balun. Don't spend $200+.

Good luck.

Stan, K4SBZ


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Mark WS7M

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Hi have to agree with this completely.  I make no claim the EF antennas work as well as OCF.  The only difference is hide-ability as the feed line from OCF will have to come down some point off center of the wire.

The EF antenna certainly will work WAY better than his original idea of an attic antenna.

It all comes down to what he wants to do, how much effort he wants to put in, and the realization that most antennas are a compromise in some way or another. 

But I totally agree Stan.  OCF way way better.   EF way way better than attic.  

Mark - WS7M
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Stan, K4SBZ

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I agree about the EF being easier to hide because the lead-in is at the very end rather that conspicuously dangling from the center, especially with a big white balun in the air (see my QRZ page - K4SBZ)

Stan
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Mark WS7M

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Dave:  

Your specific questions:

1) 4 feet from brick - I think this will be better than anything in the attic.  I think you need to presume you will have to try something, so best not make it permanent until you have tried it.  You may need to make small adjustments or even re-position stuff.

2) Eye bolt and brick veneer.  Bungees work well but require replacement about yearly.  There is a guy selling these shock absorber type things for wire antennas but when I looked at them they were fairly large and quite visible.   Once again I suggest you start with bungees and adjust as you learn more.  You might have to rehang things a few times but you will eventually figure out something that works.

3) For me, height = good.  The higher the better.  This is why Remote Ham Radio, as an example puts even dipoles up at 100 feet when they can.  But you will have to work with what you can.   One thing for sure:  9 feet outside is better than 50 feet in an attic.  Again, give it a try, adjust and perfect.

Mark
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Dave Egan

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I reality the brickwork is on the bottom part of the antenna so I should be ok as it's outside and better than inside and various electrical shields/interferences.  

As of know I've submitted my plans to the HOA.  I have a mockup of it built via paracord across my yard and with the black cord approximately the black antenna I'm planning on using, it is amazingly hard to see unless you are in my yard looking at it.  I'm situated in such a favorable position (no neighbors to the west of my house where antenna will be) and only the HOA pool/grass area there with their/my trees between it can't be seen.  I am on the board but have to obviously recuse myself from the decision.  I think they are very reasonable and am hopeful for approval in the next few weeks once the discussion occurs.  

Thanks again for all the great feedback and thoughts.  It helped me refine what I wanted to do.
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Rick - N4RZ

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Dave, outside antennas, and generally speaking the higher the better, are the way to go.  But, if that turns out not to be possible, an attic antenna can work wonders.  W9BS lives in a condo in south Florida and works all HF bands 80-6M very well with an antenna in the attic.  His antenna is an 80M dipole with two 90 degree bends in each leg fed with 33' of 450 ohm window line.  (See his qrz.com page for additional details)   We have a weekly sked on 75M SSB with some of us over 1000 miles away and his signal in most cases is equal to or better than others using outdoor antennas in the same area.   The antenna works on other bands as well since he has used it to accomplish 5 Band DXCC and needs 1 more state for 5 Band WAS.  
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Dave Egan

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Rick- good points and will be my fallback if I can't sway the HOA.

It's really my major hurdle - no sense buying a radio if I can't get it out.  Of course I have many options still.....  Oh then I gotta start studying for my General ticket!
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Dave Egan

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FYI - Making progress with HOA.  Heads are nodding and no one is flinching.  I'm expecting written approval in the next week or two!
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Dave Egan

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FWIW passed my General and HOA approved the antenna. Score one for the good guys! Thanks again all.
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Ken - NM9P, Elmer

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Well done!  Congratulations!