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Author Topic: Vertical and buried cable  (Read 1075 times)
KD5PME
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Posts: 32




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« on: November 05, 2001, 08:52:05 PM »

I got my General ticket last month and I am now ready to put up an HF antenna. Due to CC&Rs I plan to put up a vertical and am looking at the HyGain AV640 for several reasons, primarily no radials (I don't have the room, otherwise the Hustler antennas look good) and HyGain claims that guys are not needed (again, I have no room for them.) I have looked at the reviews here and they seem pretty favorable. Anyone have any experience with this antenna or its "little" brother the AV620? I would like to mount this antenna as close to house as possible to avoid a long cable run but I am a little concerned about detuning due to the cool-ply decking in my roof.

Also, Texas Towers has suggested that if I need a longer run of coax that I can connect regular LM400
cable to a shorter run of the more expensive direct-burial version with a barrel connector and save some money. Any idea of the additional loss I could incur?

Thanks in advance for the advice,
Dana Ferguson KD5PME
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WB2WIK
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Posts: 20545




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« Reply #1 on: November 06, 2001, 12:24:59 PM »

The AV-640's not bad, I recently installed one for a friend and it worked well on a rooftop.  How it might be detuned by your roof decking is a question I can't answer.  I wouldn't trust it to be self-supporting in high winds, there's a lot of weight towards the top of these antennas (15-20-30-40 meter capacity hats).  Also, you can't get "too close" to a building with one because the base has six permanently attached radials protruding in all directions.

As for LMR400, I think the concept of using "low loss" coax to feed a 50 Ohm antenna for HF is hilarious, unless your transmission line needs to be awfully long -- like 250+ feet.  Ordinary RG213/U, which is lower cost, more rugged, more flexible, and more impervious to weather than LMR400, has almost no measurable loss at all in the HF spectrum.  The "improvement" in going to LMR400, at, say 100 feet length and 28 MHz, is less than half a dB.  Not worth it.

The direct-burial RG213/U from Cable X-Perts is about 49 cents per foot and very strong.

73 de Steve WB2WIK/6

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KD5PME
Member

Posts: 32




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« Reply #2 on: November 06, 2001, 01:05:16 PM »

Thanks for the advice, Steve.

I think I can get away with the antenna being close to the house since I plan on mounting this on a 10 ft mast. I thought I saw a statement from HyGain that this vertical is self-supporting. However, when I look for it on their website I don't see it. That was a big selling point for me. My HOA has reluctantly given me approval for the antenna and I want to put up one that is a stealthy as possible as well as taking up as little space as possible (small back yard.) If you have any suggestions along these lines I am all ears.
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KD5PME
Member

Posts: 32




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« Reply #3 on: November 06, 2001, 01:15:10 PM »

I found the reference to self-supporting - it is in the latest QST ad for Hy-gain verticals. The ad claims all of Hy-Gain's verticals do not need guys.
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WB2WIK
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Posts: 20545




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« Reply #4 on: November 06, 2001, 04:21:15 PM »

Yep, I know the ad.  Then, in the assembly manual you get when you buy the antenna, guys are "recommended."  Slick advertising, but it's not just them -- it's everyone.

Having installed the AV-640 recently, and feeling how top-heavy it is when handling it, and inspecting the diameter, wall thickness and alloy of the aluminum used for the main vertical support element, I'd recommend a set of rope guys 1/2-way to 2/3-way up the antenna for all but temporary installations.  However, this can be said for most tall vertical (25') antennas, not just the AV-640.

If you want a low-impact vertical that definitely requires no guys, take a look at the Force-12 verticals.  They are very unique, center-fed, very low-profile antennas that work well when ground-mounted.

73 de Steve WB2WIK/6
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KD5PME
Member

Posts: 32




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« Reply #5 on: November 06, 2001, 08:12:19 PM »

Many thanks for the heads-up. I guess I will have to rethink my installation. I will definitely look at Force12.
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KL7IPV
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Posts: 984




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« Reply #6 on: November 07, 2001, 02:58:39 PM »

You might consider the new Anttron 8001B antenna. It covers 10 thru 80 meters and breaks down into three parts. Look here: http://anttron.tripod.com.
Good luck and welcome to amateur radio.
73
Frank
KL7IPV
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KD5PME
Member

Posts: 32




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« Reply #7 on: November 07, 2001, 03:15:08 PM »

Thanks for the reminder, Frank. I've been meaning to check them out.
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N8EMR
Member

Posts: 234




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« Reply #8 on: November 14, 2001, 03:57:37 PM »

The annaton 8010-B is just a 18ft high vertical. Basicly a big CB antenna. It covers whatever your tuner will tune to it to. They claim 80-10 with a tuner.
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