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Author Topic: Antenna Help/question  (Read 1396 times)
KA4NMA
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Posts: 328




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« on: February 10, 2013, 09:12:00 PM »

I was planning a stealth random loop around my apartment sides and roof, which is a quadplex, but I have metal gutters on 2 sides.  So I needed to rethink my plans.  I am thinking of running a random length wire on 2 sides of the apartment.  It would be "L" shaped with the short side being zig-zagged.  I Hope to to work multiband 160 (or 75m)-6m with my SGC auto tuner.  I know I need some sort of ground.  An outside earth ground or radials is not possible.  What would be better - A set of radial(s)  in my shack (bedroom) or the MFJ Artificial Ground? The ideal would be a set of radials for each band.  Would a couple of longer random length radials work?  Any ideas or suggestions or tips?  This is a compromise antenna and the plan is to use anything to get on the air!

Randy ka4nma
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KQ6Q
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Posts: 971




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« Reply #1 on: February 11, 2013, 12:10:27 AM »

In an apartment situation you're begging for RFI in your neighbor's stereo systems. Try a reasonable band - 40m to start with, with a 33' wire on the hot side of the tuner around the ceiling, and another for the counterpoise around the baseboards. a Wire outdoors, to a tree would a be better. Or consider a 40m/20m end fed from LNR precision. A Buddipole would also be worth considering. forget 80 and 160 meters from the apartment. Do you belong to a local ham club? join one, and ask one of the elmers to come over, survey the actual situation, and make recommendatins.
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W5WSS
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Posts: 1689




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« Reply #2 on: February 11, 2013, 09:03:57 AM »

I built and installed a 14'x25' horizontal rectangular closed loop on my ceiling.The height above ground measured a low 18' but not low on 10m.

My goal for this system was simple, multi band service along with an understanding of how horizontal antennas relate to height above ground and frequency applied relative to skywave and TOA etc....I was not disappointed because I knew what to expect and when the system made contacts farther than normal happy day.

I used a wide range Tmatch tuner with the integrated 1:1 current balun' at the rig.

I attached 5'6"(just for the reason to reach the tuner terminals) of balanced line directly at the antenna and then routed it straight down using a couple stand offs because I intended to transmit and attached it to the balanced terminals of the T match tuner.

The moral of this story is: I made many strong signal contacts on the low bands from 160 and all the way to 10m.

Have fun 73



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W5WSS
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Posts: 1689




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« Reply #3 on: February 11, 2013, 09:10:21 AM »

Oh and incidentally I used # 14 insulated wire a color to match and blendwith the wall and ceiling scheme.

clipped  around the crease where the top wall junctions with the ceiling.

I even opened the loop up and had a completely different system allot of fun experimenting.

Keep the output power safe 73
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KA4NMA
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Posts: 328




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« Reply #4 on: February 12, 2013, 02:44:05 PM »

I would not be able to put such a large loop indoors.  I might could get a 9'x12' loop.  It is most likely to small for 40-6m.

Randy ka4nma
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W5DXP
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« Reply #5 on: February 13, 2013, 06:40:50 AM »

Oh and incidentally I used # 14 insulated wire a color to match and blendwith the wall and ceiling scheme.

A friend of mine put aluminum tape in a square loop around the top of the walls just next to the ceiling in his apartment and covered the aluminum tape with wallpaper border. Except at the feedpoint in one dark corner of the room, it was virtually invisible.
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73, Cecil, www.w5dxp.com
The purpose of an antenna tuner is to increase the current through the radiation resistance at the antenna to the maximum available magnitude resulting in a radiated power of I2(RRAD) from the antenna.
W5WSS
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Posts: 1689




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« Reply #6 on: February 13, 2013, 07:20:22 AM »

Yeah,Cecil The wider foil although thin should be more broadbanded.

Is good to know that the contact with the wall was not a problem with RF heating at reasonable transmitting output power levels.

I had to make small holes to pass through the partition for the 25ft run of wire and was no problem.

A putty knife and some Spackle later holes were gone.

I made allot of different size and shape loops including vertically radiating rectangles.

One in particular, worked very well on 40m skywave dx included.

The feed method transformed up from 15 ohms RR to a higher more manageable level and matched nicely.

So to those interested the vertical family of loops are effective for securing a lower manifested trajectory of transmitted power to the environment. compared to the horizontal family of either of the self contained antennas.
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KA4NMA
Member

Posts: 328




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« Reply #7 on: February 13, 2013, 10:08:45 PM »

Oh and incidentally I used # 14 insulated wire a color to match and blendwith the wall and ceiling scheme.

A friend of mine put aluminum tape in a square loop around the top of the walls just next to the ceiling in his apartment and covered the aluminum tape with wallpaper border. Except at the feedpoint in one dark corner of the room, it was virtually invisible.

Where can I find the aluminum tape?  Does it have a sticky back?
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W5DXP
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« Reply #8 on: February 14, 2013, 04:20:53 AM »

Where can I find the aluminum tape?

It's used on heating/cooling ducting and available at Lowes or Home Depot.
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73, Cecil, www.w5dxp.com
The purpose of an antenna tuner is to increase the current through the radiation resistance at the antenna to the maximum available magnitude resulting in a radiated power of I2(RRAD) from the antenna.
KA4NMA
Member

Posts: 328




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« Reply #9 on: February 19, 2013, 04:55:56 PM »

How did he feed the tape antenna?
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W5WSS
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Posts: 1689




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« Reply #10 on: February 19, 2013, 06:07:45 PM »

I can comment on an excellent method That I would use to connect a foil element to a feed line.

I would sandwich the foil between two light weight thin wall 3/32"aluminum plates large enough to span the foil width and perhaps 3"X3". LxW

Then pop a same diameter hole through the foil to allow attachment of the bolts perhaps #8- 32 Machine thread and nuts and electrical star washers for excellent bite and conductivity after tightening the plates sandwiching the foil between them.

Then attach the feed line with crimped and soldered ring terminals atop the Aluminum plate and incorporate a strain relief.
For the benefit of multi band service I would probably use 300 ohm balanced line for this antenna.

I would use a short length direct route to the tuner and utilize standoffs to keep the line away from the sheet rock by about 2-3" Mine was 5ft 6" from the antenna terminals to the tuner at desktop height.
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W5DXP
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« Reply #11 on: February 19, 2013, 06:24:08 PM »

How did he feed the tape antenna?

With about 10' of RG-8x coax.
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73, Cecil, www.w5dxp.com
The purpose of an antenna tuner is to increase the current through the radiation resistance at the antenna to the maximum available magnitude resulting in a radiated power of I2(RRAD) from the antenna.
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