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Author Topic: Thin wire/ "Invisible Antennas"  (Read 35795 times)
AJ3O
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Posts: 124




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« Reply #15 on: July 25, 2012, 02:23:57 PM »

I was told by an old ham that the BEST color for wire, guy rope, etc. is a slightly darker shade of purple. Anyone ever try this? Worth a shot with some 18-22 gauge wire, it may be just about invisible...
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KJ6ETL
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Posts: 43


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« Reply #16 on: August 11, 2012, 05:46:41 AM »

I have had a 100mtr long dipole made out off thin welding wire running 60ft high over a public green zone. It was impossible to see and worked great :-)
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KD4SBY
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Posts: 223




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« Reply #17 on: October 01, 2012, 07:32:33 AM »

I know a Ham who lives in a HOA controlled community, and he uses two end-fed antennas made from Radio Shack 20AWG wire. He uses a buried coax cable that runs to a small tree in the yard, a small bucket underneath by the tree trunk with a balun, and wires running up into the tree to a yard fence no more than 30 feet in the back of his property. That together with a linear + antenna tuner, enables him to push 500 Watts on four bands with excellent results and good receiving capabilities. He claims that he never had the need of spending more than $20 on his antennas to get on the air and make contacts all over the world.(using CW)
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KB2FCV
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Posts: 1139


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« Reply #18 on: October 01, 2012, 10:30:18 AM »

I had a long wire up with magnet wire and fishing line for a while when I lived in my apartment. It came down once, and when I put it back up I didn't have any magnet wire available and it was hours before CQWW. I put it up with some heavier wire/rope for a weekend but got "discovered" by the apartment people before the weekend was out.. no more antennas allowed. That fishing line/magnet wire antenna was up for quite a while though!
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N0HC
Member

Posts: 7




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« Reply #19 on: October 13, 2012, 03:21:45 PM »

I used magnetic wire for years - I supported it with fishing line through pulley and tensioned by springs..

I ran into an interesting problem - birds could not see it either and ran into it, one morning I woke up to a lot of noise and opened my curtains to see an owl had pulled the whole thing down and was stomping on it on my deck! He did not look happy. I ran a thicker wire after that..

N0HC
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AD0AE
Member

Posts: 76




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« Reply #20 on: November 04, 2012, 12:57:39 PM »

Hi All-

I just wanted to come back to this forum.  First off, thank you all for the many posts I got back about this topic!  As it turned out I have been experimenting with some thin wire antennas from my apartment.  I have at least made a few JT-65 contacts, so that has been successful! 

What has been bothering me a lot is that I have the wire antenna(dipoles or end feds) hugging the side of the building.  I can even attach the wire to a fence across the parking alley.  In both cases, I am getting a TON of noise above 10 MHz.  It mainly sounds like hum.  It is S-9 or so on anything above 10 MHz.  I am also seeing a  dominant 'line' (in the JT65 waterfall) at about 14.077 MHz.  I am wondering what that might be from. 

This result surprised me because I thought getting the antenna outside might modestly reduce the amount of noise I am hearing with indoor antennas, not increase it.  So I am really perplexed why it seems to have gotten worse, not better.

I plan to post onto the RFI forum, because I did notice I have a utility transformer about 25 feet from my operating location and the antenna - could that be hosing me?

Thank you all and 73s
Steve
AD0AE
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TANAKASAN
Member

Posts: 933




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« Reply #21 on: December 23, 2012, 02:05:08 AM »

I also operate invisible antennas due to the neighbor acceptance factor. I'm not sure of the gauge but to make it invisible (and I mean REALLY invisible) I used white insulated wire and painted it at random intervals with gray and sky blue auto paint. The human eye expects to see a continuous line and the change of color against a gray, blue or white sky breaks this up.

The wire has been up for seven or eight years now and I've never received a complaint.

Tanakasan
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N3LCW
Member

Posts: 133




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« Reply #22 on: December 23, 2012, 11:40:09 AM »

Steve,

Give us more of a description of the antenna installation.

Consider using something like the Timewave ANC-4 Noise Phase cancellation filter or the MFJ-1026 equivalent.  They do work against local noise if you use a real noise sense antenna and not the short whip (unless the noise you are trying to filter is in the same room as the rig is).  I've used this filter successfully when I used an attic wire antenna and picked up all sorts of noise from the house.

Andy
N3LCW




Hi All-

I just wanted to come back to this forum.  First off, thank you all for the many posts I got back about this topic!  As it turned out I have been experimenting with some thin wire antennas from my apartment.  I have at least made a few JT-65 contacts, so that has been successful! 

What has been bothering me a lot is that I have the wire antenna(dipoles or end feds) hugging the side of the building.  I can even attach the wire to a fence across the parking alley.  In both cases, I am getting a TON of noise above 10 MHz.  It mainly sounds like hum.  It is S-9 or so on anything above 10 MHz.  I am also seeing a  dominant 'line' (in the JT65 waterfall) at about 14.077 MHz.  I am wondering what that might be from. 

This result surprised me because I thought getting the antenna outside might modestly reduce the amount of noise I am hearing with indoor antennas, not increase it.  So I am really perplexed why it seems to have gotten worse, not better.

I plan to post onto the RFI forum, because I did notice I have a utility transformer about 25 feet from my operating location and the antenna - could that be hosing me?

Thank you all and 73s
Steve
AD0AE
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K0JEG
Member

Posts: 631




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« Reply #23 on: December 25, 2012, 08:56:33 AM »

Steve,

Give us more of a description of the antenna installation.

Consider using something like the Timewave ANC-4 Noise Phase cancellation filter or the MFJ-1026 equivalent.  They do work against local noise if you use a real noise sense antenna and not the short whip (unless the noise you are trying to filter is in the same room as the rig is).  I've used this filter successfully when I used an attic wire antenna and picked up all sorts of noise from the house.

Andy
N3LCW

From the specs of the ANC-4

"Signal Loss, Main Ant. to Radio: 6 dB"

That seems like a lot of loss to me. Have you used one? I have a serious noise problem on 80 Meters and I'd like to see if it would help.
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K9SRV
Member

Posts: 121




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« Reply #24 on: December 25, 2012, 11:40:33 AM »

Ignored this thread first time around, but then purchased a Johnson Matchbox
with a post for a long wire. Sat,, for a camping trip or vacation, do you guys hace and tips as to height, lenghts to avoid, flat vs. sloping etc? I would like to test it here at home where I can put up about 220 feet straight. Also, since its going to the matchbox single wire terminal, I assume I do not have to drive an 8 foot ground ros just for this, although, I "Could" be wrong.  Roll Eyes

Any help, input appreciated.
John
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N3LCW
Member

Posts: 133




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« Reply #25 on: December 25, 2012, 11:42:41 AM »

Yes, I use the ANC-4 very successfully.  The 6db figure will vary, but not by more.  It will absolutely pull a signal out buried in local noise.  If you really want to exploit this filter to its fullest you can use it for diversity reception using 2 separate antennas; one dedicated for receive, on all bands.  For example if you are listening to a signal on a frequency with no interference, you can adjust the phase and gain of the two antennas and increase the amplitude of the desired signal.

You really need to read the manual and play with the controls to fully take advantage of what this filter can do.

Timewave recommends a technique of listening on the main antenna and noting the noise level, then switch to the noise sense antenna ( I use my antenna tuner's antenna switch to REMOVE the main antenna from the filter) set the NOISE PHASE fully CCW, and adjust the NOISE GAIN control to match the noise noted on the main antenna.  Switch the main antenna back into the filter (again, using either your antenna tuner or actual antenna switch) and now adjust the NOISE PHASE pot and alternately play with the PHASE RANGE and FREQ RANGE switches until the noise either disappears or is attenuated.  I get better than 35-40db noise nulls, and the signals buried beneath come alive.  

This may sound tedious but if you're stuck in a bad noise situation this works.  I still use it to eliminate the S9 birdies from my cable modem on 30M.  It wipes them out completely.

I hope this helps.

Andy
N3LCW


Steve,

Give us more of a description of the antenna installation.

Consider using something like the Timewave ANC-4 Noise Phase cancellation filter or the MFJ-1026 equivalent.  They do work against local noise if you use a real noise sense antenna and not the short whip (unless the noise you are trying to filter is in the same room as the rig is).  I've used this filter successfully when I used an attic wire antenna and picked up all sorts of noise from the house.

Andy
N3LCW

From the specs of the ANC-4

"Signal Loss, Main Ant. to Radio: 6 dB"

That seems like a lot of loss to me. Have you used one? I have a serious noise problem on 80 Meters and I'd like to see if it would help.
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K0JEG
Member

Posts: 631




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« Reply #26 on: December 26, 2012, 05:43:43 AM »

Yes, I use the ANC-4 very successfully.  The 6db figure will vary, but not by more.  It will absolutely pull a signal out buried in local noise.  If you really want to exploit this filter to its fullest you can use it for diversity reception using 2 separate antennas; one dedicated for receive, on all bands.  For example if you are listening to a signal on a frequency with no interference, you can adjust the phase and gain of the two antennas and increase the amplitude of the desired signal.

You really need to read the manual and play with the controls to fully take advantage of what this filter can do.

Timewave recommends a technique of listening on the main antenna and noting the noise level, then switch to the noise sense antenna ( I use my antenna tuner's antenna switch to REMOVE the main antenna from the filter) set the NOISE PHASE fully CCW, and adjust the NOISE GAIN control to match the noise noted on the main antenna.  Switch the main antenna back into the filter (again, using either your antenna tuner or actual antenna switch) and now adjust the NOISE PHASE pot and alternately play with the PHASE RANGE and FREQ RANGE switches until the noise either disappears or is attenuated.  I get better than 35-40db noise nulls, and the signals buried beneath come alive.  

This may sound tedious but if you're stuck in a bad noise situation this works.  I still use it to eliminate the S9 birdies from my cable modem on 30M.  It wipes them out completely.

I hope this helps.

Andy
N3LCW

Thanks. After reading this thread I checked out reviews of this and other units. I think I might have to give it a try. Most of what I get is broadband hash from overhead power lines, not a single birdie, but it might help a little.
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WB6BYU
Member

Posts: 13005




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« Reply #27 on: December 26, 2012, 11:50:16 AM »

Quote from: K9SRV
Ignored this thread first time around, but then purchased a Johnson Matchbox
with a post for a long wire. Sat,, for a camping trip or vacation, do you guys hace and tips as to height, lenghts to avoid, flat vs. sloping etc? I would like to test it here at home where I can put up about 220 feet straight. Also, since its going to the matchbox single wire terminal, I assume I do not have to drive an 8 foot ground ros just for this, although, I "Could" be wrong.  Roll Eyes


There are many factors to consider, depending on what bands you want to work, your
available supports, etc.  But here are some general points that I've found from my
experience using long wires, especially for portable operation:

1)  The same RF current flows into both your antenna wire and your ground system.  If you
don't provide an intentional ground system then the outside of your coax, the chassis of
your rig and tuner, and any wiring for headphones, mic, battery cables, etc. will be your
ground system.  That isn't always desirable.  But an 8' ground rod is actually a pretty poor
RF ground (besides being inconvenient for transient operation) so isn't a good approach
anyway.

I've operated without an intentional ground system on several occasions, and sometimes
I've gotten by with it, especially at QRP.  Other times I've had problems with RF feedback
causing quirky symptoms (keyer running amok, panel lights blinking, garbled audio, etc.)

Usually a quarter wave radial wire for each problem band attached to the back of the
tuner will solve such problems by giving the RF somewhere to go.


2)  Using an antenna wire that is a multiple of a half wave makes a high impedance, so the
currents at the feedpoint aren't as large for the same output power.  This makes ground
losses less of a problem.  (The simple radials used in step 1 are not usually sufficient for
this purpose.)  Personally I've had good results with wires around 130' - 135' for 80m
through 10m (at least the pre-WARC bands), though some people don't like using a high
impedance feedpoint.

3)  At a minimum try for 3/8 wavelength of wire on your lowest band.  More is better. 
But I haven't been impressed the times I've used a really long wire, as the pattern tends
to get more directional on the higher bands, and this can be counterproductive.  We tried
a 600' long wire one year on Field Day and it wasn't any better than a dipole (and often
worse.)  Also the MatchBox will do better with higher impedance loads, and may not be
able to match a wire if it is too short.

4)  Height is important for DX on the higher bands.  But if you are mainly interested in
relatively local coverage (within 500 - 1000 miles) on 40m and 80m, then low height
isn't as much of a problem.  In order to get as much of your wire as high as possible, I'd
suggest an inverted-"L" arrangement, where most of the wire is strung horizontally between
two supports, with the remainder serving as a lead-in dropping down to the rig.  But
to a large extent the wire configuration will depend on what supports are available to
you.  A long vertical wire (over about 5/8 wavelength) may not be as effective as a shorter
one, though you can use up to 1 wavelength or so with adequate results.

5) Make sure your MatchBox has been modified to jumper around the receive relay: 
they date from before transceivers were common, and are designed for a 600 ohm output
to a separate receiver when the relay isn't energerized.

6)  The Matchbox does not provide a DC path to ground from the antenna terminal.  I had
one situation where there was enough static charge picked up on the antenna wire that
the capacitors in my tuner were arcing over.  A 100K 10W wirewound resistor from the
antenna to ground (I used a BBQ skewer - it doesn't need a low resistance) will help to
dissipate the charge.  On the other hand, if the high static level is due to nearby
thunderstorm activity, quit operating and disconnect everything.  You aren't going to
be able to create a ground system capable of handling a direct lightning hit in a temporary
portable station.


Probably the best performance I ever got from a long wire was on Field Day from southeast
Alaska with my old Ten-Tec Argonaut.  I had a sloping long wire running from a tall tree
on the shore out over the tide flats to a post I had put up at low tide.  When the tide came
in the sloping wire over salt water gave me an effective low-angle radiator (though I still only
made about 40 contacts.)  Among other things, that requires the right combination of slope
angle and wire length in wavelengths.

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K5TED
Member

Posts: 690




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« Reply #28 on: December 26, 2012, 12:48:19 PM »

I just picked up another SGC auto-coupler and "Stealth Kit". They are truly the Antenna Restricted Ham's friend. The MFJ Noise Canceller is also a good investment. The SG-237 and Stealth Kit can be used to make a nice, compact, 4 or 5 turn wire loop on about a 50" square frame or just suspended wire loop.

To the OP, the SG-237 or other SGC auto-coupler would work well in conjunction with your wire strung around the entire perimeter of your eaves. Put the SGC right at the loop feedpoint.

Keep in mind, though, the radiation pattern of a horizontal wire loop of this sort. Not great for DX, but good out to several hundred miles as it is quite a high angle pattern.

The advantage of the SGC, and it may well be the same with the Icom AH tuners, is that there is no button pushing to tune or clear memories, and no control cable needed. Fully automatic operation. Some other remote tuners will require manual intervention from time to time.

I have an SG-230 mounted outside in a sheltered spot under the eave, driving a 40' horizontal wire. It's powered with a small wall wart transformer plugged into an inexpensive outdoor rated remote control power switch. If I need to reset the SGC to clear memories, I just power cycle it with the remote switch. It does well on 40m - 10m, somewhat useable on 75m and I've actually made a few phone contacts on 160m with it.

As for the MFJ Noise Canceller, I've had mixed luck with it. Certainly, the noise sense antenna needs to be able to see the same signals as does the main antenna or it simply doesn't work. There are also some spacing considerations between sense and main for optimal performance. Be sure to use the hard PTT port, not rely on the RF sensing.
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WX7G
Member

Posts: 5915




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« Reply #29 on: December 27, 2012, 12:20:36 PM »

Hi All-

I just wanted to come back to this forum.  First off, thank you all for the many posts I got back about this topic!  As it turned out I have been experimenting with some thin wire antennas from my apartment.  I have at least made a few JT-65 contacts, so that has been successful! 

What has been bothering me a lot is that I have the wire antenna(dipoles or end feds) hugging the side of the building.  I can even attach the wire to a fence across the parking alley.  In both cases, I am getting a TON of noise above 10 MHz.  It mainly sounds like hum.  It is S-9 or so on anything above 10 MHz.  I am also seeing a  dominant 'line' (in the JT65 waterfall) at about 14.077 MHz.  I am wondering what that might be from. 

This result surprised me because I thought getting the antenna outside might modestly reduce the amount of noise I am hearing with indoor antennas, not increase it.  So I am really perplexed why it seems to have gotten worse, not better.

I plan to post onto the RFI forum, because I did notice I have a utility transformer about 25 feet from my operating location and the antenna - could that be hosing me?

Thank you all and 73s
Steve
AD0AE

The end fed antenna another half and that half is the AC wiring in the apartment building. Half of your antenna is inside and half is outside.

How about the dipole? If decoupled with a common-mode choke (1:1 current balun) the entire antenna is outside.

How are you feeding the dipole?
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