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Registered Member #1327
Joined: Mon Feb 18 2008, 12:13AM
Location: North Ridgeville, Ohio.
Posts: 38
No Profile is more like it. I am in a development that will not allow outdoor antennas. What they don't see doesn't exist. VHF and UHF are pretty simple to overcome. HF is my low profile need. I have thought about running a wire around the perimeter of my roof. This would give me a really large loop. I could always get a slinky antenna up in the attic. My concern with these ideas is that I don't want to be filling my house with RF.
I have a 4' wooden picket fence that runs my backyard. I have been toying with the idea of running wires on the fence as radials and putting up a birdhouse on a 15' pole. I can actually have a birdhouse on a pole but no antenna. ???wth???. My problem with this is figuring out how to isolate the pole from ground.
Any ideas or antenna projects that you have found useful may be of help to me. I need some sort of inspiration to upgrade my license. ;)
Registered Member #16
Joined: Thu Feb 02 2006, 02:22PM
Location: New Wilmington, PA
Posts: 554
Are you just looking for receiving antennas for HF? If thats the case, what you need is an AMRAD Active Whip. Chris Russell has one, and I can vouch for it. It can hear anything from about 100KHz up through 10MHz extremely well. Even up to 30MHz its usable.
If you're looking to transmit, then you have a bit more of a challenge ahead.
The birdhouse pole could work just fine. I have a 17' tall 1.5" diameter vertical with a 4'x4' capacitance hat made of 1/4" wire mesh that tunes 1.5-18MHz extremely well. The hasle there is building a motorized tuning coil to place about 4' off the ground (and hiding it effectively). I have 10 70' radials laid out in the yard, and it is extremely effective down to 80 meters, and gets out reasonably well on 160 meters.
By reducing the size of the capacitance hat, I can easily get 80 meters through 10m, and 6 meters with an additional Pi tuner.
I'll post photos of it later today. I have to go out and do some maintenance on it anyway.
Registered Member #1327
Joined: Mon Feb 18 2008, 12:13AM
Location: North Ridgeville, Ohio.
Posts: 38
Dave Marshall wrote ...
Are you just looking for receiving antennas for HF? If thats the case, what you need is an AMRAD Active Whip. Chris Russell has one, and I can vouch for it. It can hear anything from about 100KHz up through 10MHz extremely well. Even up to 30MHz its usable.
If you're looking to transmit, then you have a bit more of a challenge ahead.
The birdhouse pole could work just fine. I have a 17' tall 1.5" diameter vertical with a 4'x4' capacitance hat made of 1/4" wire mesh that tunes 1.5-18MHz extremely well. The hasle there is building a motorized tuning coil to place about 4' off the ground (and hiding it effectively). I have 10 70' radials laid out in the yard, and it is extremely effective down to 80 meters, and gets out reasonably well on 160 meters.
By reducing the size of the capacitance hat, I can easily get 80 meters through 10m, and 6 meters with an additional Pi tuner.
I'll post photos of it later today. I have to go out and do some maintenance on it anyway.
Dave
I am looking to transmit on the setup I finally build. My rig is a 706MKIIG and I have the accompanying AH-4 automatic tuner. The bird pole I think will be my best bet. Any ideas on how I can put a metal pole into the ground and keep it insulated from ground? I was thinking about a 20' pole, 5' into a caped pvc tube filled with concrete to take up the slack. provided I bury this so it is not entirely buried I think it should work. I dunno...
Registered Member #16
Joined: Thu Feb 02 2006, 02:22PM
Location: New Wilmington, PA
Posts: 554
Unfortunately, it is a flawed federal law. The FCC Part 97 stipulation that HOAs make "reasonable accomodations" for hams has been ignored by courts again and again.
The wording is very vague, and HOAs have taken full advantage of that to completely ban antenna structures in hundreds of neighborhoods. Until the FCC gets their head out of their collective asses, or the states step in (several have already), hams are on their own, and take their chances in court at their own peril.
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David, you don't want to set the metal pole straight into the ground. That will force your feed point up away from the base and could cause some matching problems, not to mention the fact that water/snow/debris could short the antenna to ground fairly easily.
The antenna is made from 4' sections of antenna mast. 2 sections are fiberglass, and three are aluminum. Total height is about 16'. I buried one fiberglass section with only about 8" protruding from the ground (I didn't set it in concrete but you can). The aluminum mast then sits on top of this fiberglass section, with the feed point about 8-10" off the ground.
There is one aluminum mast section, then a fiberglass section, then two more aluminum sections above that. The fiberglass section has a Little Tarheel II mobile screwdriver antenna in parallel with it, acting as a motorized loading coil. Any homebrew screwdriver coil will work, I just use my tarheel because its handy. In those photos, there should be a control cable going to the loading coil, I just didn't have it hooked up.
On top of the whole thing is a 4'x4' square of 1/4" wire mesh thats bolted to the top of the aluminum mast. Tuning range is from about 1.2Mhz through about 18.5Mhz. On higher bands where the radials are an appreciable fraction of a full wave, SWR may not get below 2:1, but the takeoff angle is excellent, making up for it. By cutting the capacitance hat down to 2'x2' the antenna would very effectively cover 80-10m, but I think I'd I'd have to put a larger loading coil on it to get down to 160m.
There is a ground plate buried below the antenna and 10 70' radials strung out in the yard, with plans to add 6 more this spring. The ground plate is connected to the feed point with 8" of 6 awg solid copper. The models suggest efficiency is somewhere around 35-40% for 160m (not bad for such a compact antenna) and >95% on 17m with all 16 radials in place. Overall, its an exceptional performer, and one of the most successful antennas I've yet constructed.
Registered Member #1327
Joined: Mon Feb 18 2008, 12:13AM
Location: North Ridgeville, Ohio.
Posts: 38
Thanks Dave for the pics. It definitely helps to see other work when doing my planning. I could never get away with what you have, ;) but it's nice. I plan to run 20' of black pipe. 5' encased in a pvc tube and threaded just above ground. Then the 15' section threaded into that with a birdhouse ontop of an 18-24" metal plate. I hope to do a lot of qrp and low power rtty, that kinda thing. Had a local friend who worked a guy in Denver on 20m @ 100mils. rtty.
I have toyed with the idea of getting a yaesu rig with the self tunning mobile antenna. Mounting it inside a fake stink pipe. it would stick out when working but be almost unnoticeable. The issue here is everyone I talked to said this would be a poor substitution for a real antenna and I wouldn't be happen considering the fundage needed to support the gear.
... not Russel! Registered Member #1
Joined: Thu Jan 26 2006, 12:18AM
Location: Tempe, Arizona
Posts: 1052
That sounds like a fine setup to me. With the autotuner, that should get you active on a lot of bands. You can probably add many more bands to that simply by building a matching box with some coils and caps to swap in and out.
Performance will be greatly improved if you can get a large capacitance hat up there. Any possibility that in addition to the plate, you could add, say, eight metal "perches" that extend a few feet out?
Same story for the radials. Put as much copper into your yard as humanly possible. Every radial you add will pay you back, guaranteed.
Let us know when you're ready to get on the air. I have a stealth 20m antenna of my own that I need to get back outside now that the weather is nice, and I can work any of the digital modes. Can't say I've ever used rtty, but psk31 works well, and I am trying to get people to start using msk31.
Registered Member #16
Joined: Thu Feb 02 2006, 02:22PM
Location: New Wilmington, PA
Posts: 554
PSK31, Olivia, MSK31 and QRSS are great low power modes. I've got 39 countries on 5w PSK31 so far.
If you've got the money, these Little Tarheel II antennas could easily pass for a sewage pipe. The only trick there is getting it a nice ground network.
Registered Member #1327
Joined: Mon Feb 18 2008, 12:13AM
Location: North Ridgeville, Ohio.
Posts: 38
I will let you all know when I get it going. The weather looks like it should be breaking here very soon and as soon as it does I should be building. PSK31 is what I meant when I said rtty. I do need to upgrade to work 20m but I can get on that too if I find the inspiration. Radials Radials Radials.. That what everyone keeps saying. ;)
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Low Profile Antenna Ideas.
