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Author Topic: AS-2 All Band Wire Antenna 70 foot long  (Read 10171 times)
WHALER13
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Posts: 43




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« on: October 01, 2013, 06:56:49 PM »

I would like to know if anyone has experience using this antenna?
Your input is greatly appreciated.

Thank you
« Last Edit: October 01, 2013, 07:06:44 PM by WHALER13 » Logged
WB6BYU
Member

Posts: 15495




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« Reply #1 on: October 01, 2013, 07:09:14 PM »

Can you provide a link to it?

OK, I found it at Spi-Ro, here:
http://www.spiromfg.com/all_band.htm
« Last Edit: October 01, 2013, 07:12:18 PM by WB6BYU » Logged
KA4POL
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Posts: 2409




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« Reply #2 on: October 01, 2013, 09:59:27 PM »

Did you check that: http://www.eham.net/reviews/detail/4763
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G8JNJ
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Posts: 595


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« Reply #3 on: October 02, 2013, 04:48:03 AM »

Hi,

I'd suggest searching the web for designs like this - it's easy and cheap enough to build your own. Loading coils should be about 2/3 to 3/4 along the wire for best results.

Some sites that offer good starting points.

http://www.worldwidedx.com/amateur-radio-antennas/30736-coil-loaded-dipole-build-photo-diary.html

http://www.i1wqrlinkradio.com/antype/ch2/chiave1045.htm

https://sites.google.com/site/vkonehw/home/antennas/radiation-coupled-dipole

http://www.nonstopsystems.com/radio/frank_radio_antenna_beam.htm

http://www.k7mem.com/Electronic_Notebook/antennas/shortant.html

Here's a review of a similar design.

http://g0kya.blogspot.co.uk/2010/08/western-hf10-multiband-dipole.html

Regards,

Martin - G8JNJ

www.g8jnj.webs.com

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W5DXP
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« Reply #4 on: October 02, 2013, 05:58:32 AM »

Your input is greatly appreciated.

The "shorteners" are no doubt loading coils so each half of the antenna is like a center-loaded 160m vertical that is 35 ft long. Such a loading coil would have an inductance around 120 uH to make the dipole resonant on 160m. If that coil is made to be high-Q, it would be gigantic. It doesn't look gigantic in the picture so it is probably low-Q with lots of self capacitance and that means a low self-resonant frequency. For efficiency reasons, loading coils should never be operated above their self-resonant frequency. In fact, between its 1/4WL parallel self-resonant frequency and its 1/2WL series self-resonant frequency, the coil has negative inductance.

As an example, my large 80m Texas Bugcatcher loading coil (75 uH) has a self-resonant frequency of around 8 MHz. That lower-Q 120 uH loading coil would probably have a much lower self-resonant frequency, probably far below 7 MHz.

Performance is considerably compromised on 160m because the dipole is so short. Performance is considerably compromised on the HF bands because of self-resonance effects in the loading coils. Personally, if they sent me a free antenna, I would use it for a dummy load.Smiley Did anyone notice that they don't publish any gain figures?

One of the reviews, using 160m, said that antenna was S5 on receive compared to an OCF which was S9+10 on receive. Assuming one S-unit is 6dB, that's 34dB difference i.e. compared to the OCF, the AS-2 was 0.04% efficient.
« Last Edit: October 02, 2013, 06:08:38 AM by W5DXP » Logged
G8JNJ
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« Reply #5 on: October 02, 2013, 08:19:32 AM »

Your input is greatly appreciated.

One of the reviews, using 160m, said that antenna was S5 on receive compared to an OCF which was S9+10 on receive. Assuming one S-unit is 6dB, that's 34dB difference i.e. compared to the OCF, the AS-2 was 0.04% efficient.

I suspect that the OCF faired better on 160m because it was acting as a top loaded vertical, due to common mode currents on the feeder. Rather than operating as a 'true' off centre fed dipole. My 100ft top doublet with 40ft ladder line feed. Is about 12dB more efficient on 160m when strapped as a Tee. Most S-Meters are notoriously non-logrithmic at the bottom end of the range.  So I'd believe the S-Meter readings, but not the interpolated value of 34dB.

In most cases I'd say the height above ground is the limiting factor for a typical 160m dipole. So additional shortening and lossy loading, although contributing to poor performance. May not be the single worst factor in terms of affecting overall efficiency.

The point raised about using loading coils near self-resonance is very valid, especially for 160m. But adding loading to a short dipole for 80 & 40m is less problematic, as the number of turns required is much reduced.

Regards,

Martin - G8JNJ

www.g8jnj.webs.com
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W5WSS
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Posts: 2226




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« Reply #6 on: October 02, 2013, 08:19:50 AM »

Their Slop er looks interesting to use with added pairs of tuned elevated radials and perhaps hung vertically from a single high point, wonder how inefficient or efficient those higher band 40m and up traps are?

I could make them. Smiley

Making them would be a function of worthwhile perceptible performance enhancement. Expressed as a ratio of cost versus time to build etc.

Yes this idea is not new to me as I have been viewing the wire and trap combination with a greater appreciation for single point and messenger line hung downwards and tethered to messenger non conductive guy rope and anchors. The messenger lines to perform strain relief while the wire can be Teflon black color tied wrapped to the messenger rope.

The multi band BTV series of verticals COULD be Hung from single point and elevated base height and used with home made radials sets. Retuning is expected in either case whether ground mounted and radials are added so no surprise there.
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WB6BYU
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Posts: 15495




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« Reply #7 on: October 02, 2013, 08:53:20 AM »

A friend put up a similar antenna from MFJ, and asked me to help improve performance.
It was pretty poor on 160m, and usable, though not very good, on 80m.

Overall, if you are mostly interested in the upper bands, and the ability to work
40m, 80m and 160m sometimes is more important than the actual performance on those
bands, it might not be too bad of a choice.

If 40m and 80m are more important to you, I'd use an unloaded 40m dipole for starters,
then see about adding some wires with loading coils hanging down at the ends for 80m
coverage.
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N6AJR
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Posts: 9930




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« Reply #8 on: October 03, 2013, 10:19:12 AM »

build your own fan dipole for probably 20 bucks in the cost of wire.
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G3RZP
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Posts: 7240




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« Reply #9 on: October 04, 2013, 03:50:39 AM »

A dipole for 160 needs to be at least 120 feet in the air, and preferably more if it isn't to have poor SWR and radiate mainly upwards. Strapping the feeders and using it as a T with plenty of radials will do better at lower heights.
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