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Author Topic: 17th Floor Counterpoise for Vertical Whip  (Read 1376 times)
W3NCL
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Posts: 13




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« Reply #15 on: November 28, 2017, 02:23:03 PM »

@KK4OBI - Doing that up and over approach is a good idea. But I may just put in a 45-deg elbow in the existing antenna "mast" and sit it next to therail. That way the antenna would still go out like you suggested. But can you expand on this: "Depending on which wander lead connection to the whip, there is always some length of wire hanging from the ground connection that will make the whole thing resonate on a frequency of interest."? Not sure what you mean.

And, yes, I'm going to hook up an antenna analyzer to get me into the ballpark.

As far as the connector is concerned, I had a BNC female-to-PL-259 right-angle connector laying around, so I used that. The idea is that I would put an SO-239-to-SO-239 adapter there, to which I would then connect the counterpoise wire and also the PL-259 of the coax going to the tuner-SWR meter-xcvr. But my bigger question is - why do you say "connect a short coax between the antenna to the Xiegu X-108G"? Wouldn't a, say, 50' coax (which I already have) work, too?
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KK4OBI
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« Reply #16 on: November 28, 2017, 04:45:59 PM »

While watching analyzer sweeps while feeding out wire, I would find a point where there was a minimum SWR at the target frequency such as 14.2 MHz. The 20 meter plug would need more wire than using say, the 10 meter plug.  I would record the lengths and frequencies found for each of the plugs and use these values to guide routine operation.  My first thought is to do fine tuning by wire length rather than adjusting the whip just to keep that as long a radiator as possible.

Because the antenna is designed for direct connection I am uneasy that a longer connection may introduce complications and require a very broad range RF choke ($).  For sure I would keep the coax perpendicular to the antenna to minimize stray coupling.  I would test for interaction by body proximity or touching the connector to see if the analyzer shows any appreciable change.  If so, a choke is indicated.
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KK4OBI - the Old Band Instructor
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W3NCL
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Posts: 13




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« Reply #17 on: November 28, 2017, 04:57:49 PM »

Roger that. Thanks very much for the info!

If I may ask something else on a semi-related topic. I am now seriously considering the EndFedz EFT-10/20/40 half-wave. Thinking throwing it over the side of the balcony with the matching box at the top by the balcony. Maybe add a fishing weight to the bottom to keep it from flopping around too much.

How far should it reasonably be away from the building wall? I don't want to put up a deep-see fishing rod and whip it 20 feet out there, but I also realize it probably shouldn't touch the wall. Besides obviously not transmitting through a building, are there other considerations? Maybe use a PVC pipe for a, say, 1' to 2' distance from the wall?

As others have already mentioned previously, if I'm considering throwing a counterpoise overboard, maybe I just bite the bullet and buy yet another antenna and throw that. But would need to know caveats of doing so.

Thanks!
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AI4WC
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Posts: 29




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« Reply #18 on: December 06, 2017, 10:00:05 AM »

Like others have said, I have used a horizontal Hamstick dipole (at your height, I would use vertical OR horizontal configuration) off my second floor balcony, and I have had good results on 20 meters (into Europe and South America).  I've had no luck on 80 meters (bandwidth is to narrow and "touchy"; both local and long distance).  Finding enough "in place" metal for use as a counterpoise can be a problem, but keep trying.  You may want to try an MFJ artificial ground hooked up to a length of insulated wire in your apartment (insulated wire; on the floor).  Again, and keep in mind - the longer the wavelength, the narrower the working frequency.  You may have some intermittent luck on 40 meters, but it is not predictable.  Also, note that my comments pertain only to voice - not CW.
GOOD LUCK!
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AC2RY
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Posts: 310




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« Reply #19 on: December 06, 2017, 11:29:12 AM »

Roger that. Thanks very much for the info!

If I may ask something else on a semi-related topic. I am now seriously considering the EndFedz EFT-10/20/40 half-wave. Thinking throwing it over the side of the balcony with the matching box at the top by the balcony. Maybe add a fishing weight to the bottom to keep it from flopping around too much.

How far should it reasonably be away from the building wall? I don't want to put up a deep-see fishing rod and whip it 20 feet out there, but I also realize it probably shouldn't touch the wall. Besides obviously not transmitting through a building, are there other considerations? Maybe use a PVC pipe for a, say, 1' to 2' distance from the wall?

As others have already mentioned previously, if I'm considering throwing a counterpoise overboard, maybe I just bite the bullet and buy yet another antenna and throw that. But would need to know caveats of doing so.

Thanks!

You need to understand that your building is made from concrete reinforced with steel bars. There is a lot of metal inside walls. It means that antenna should be placed as far away from it as possible. Minimum distance should be at least 1/4 of a wave length. Thus if you are going to use dipole or similar antenna, you have to push it away from wall suing long pole. At the same time having that much of metal, may allow you to use monopole antenna pointing away from building, with metal parts of building serve as ground plane. I do not know about your local building code, but generally all metal structures inside walls are interconnected and grounded. You balcony railing should e connected to reinforcing bars in walls and thus can be used as a contact point for antenna ground. You can check this assumption by measuring resistance between ground terminal in power outlets and balcony railing. Resistance should be below 100 ohms. You may forget about 80 (and even 40) meters unless you use slopper wire antenna directed well away from the building. Do not forget to use high quality current balun between coax feed line and antenna of any kind.

« Last Edit: December 06, 2017, 11:32:21 AM by AC2RY » Logged
KENNETH
Member

Posts: 96




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« Reply #20 on: December 06, 2017, 03:48:53 PM »

Like others have said, I have used a horizontal Hamstick dipole (at your height, I would use vertical OR horizontal configuration) off my second floor balcony......

Another vote for this. WWW.bsandersen.com/resources  Download the PDF book "antennas for 100 pound dxpeditions" page 214 has it modeled with the extra wire dangling off the end of a fiberglass pole on a balcony.
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W3NCL
Member

Posts: 13




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« Reply #21 on: December 07, 2017, 08:53:05 AM »

Thank you all for the additional comments. Good info there. I like that DXpedition PDF book!

Question: Is a 20m monobander worth it at this point in the solar cycle or does it not matter? I heard it's pretty dead on there now, which is why I was looking for 80m and 40m solutions to begin with. I just didn't think it was worthwhile setting up for 10m or 20m (SSB).

Nico
W3NCL
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