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Author Topic: Getting the antennas right the first time, well ma  (Read 1176 times)
KD7SIX
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Posts: 24




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« on: November 23, 2002, 01:49:04 PM »

Hello all you antenna gurus, can you help a new tech out?
I have been setting up my ham shack and I just want to make sure I get the antennas right. I have an IC-706MKIIG and have set up a 6meter Diamond A504HB 4 elm yagi on my roof. It is mounted to a 20' mast & rotor (it is about 35' from the ground) with the base strapped to the roof mount AC unit I have it guy wired 4 wires in the middle and 4 at top (very sturdy)
(1)Will the metal guy wires cause any type of problems? Seems to be working fine. After I put it up I was told that metal guy wires could cause problems?
(2)I have my Diamond X510MA dual band vertical mounted to the same AC unit about 2' away from the 6 meter mast, is this a bad application?
I am diligently studying Morse code as I listen to the mostly silent 6 meters usb and plan to take the general/code test Jan. 4th 2003. So a HF antenna will be required in the very near future. With my existing set up what type of antenna should I be looking for? I like sticking my 706 in my truck and was thinking about a High Sierra screw antenna, I see that they come with quick detach mounts, would this antenna be a good choice to use on the roof too?
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WA4PTZ
Member

Posts: 528




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« Reply #1 on: November 25, 2002, 05:55:03 AM »

You did not mention any earth grounds.
You also did not mention if the mast
was sitting on the roof materials or
on a plate. (wood , metal or other)
You also did not mention if you were
interested in a HF beam or dipoles or
both. If you decide to use a HF beam it
will need to be light weight due to the
light weight set-up. Remember Newton's
Law...for every action there is an
opposite and equal reaction.
73 - Tim
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WB2WIK
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Posts: 20560




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« Reply #2 on: November 25, 2002, 05:25:55 PM »

The guy wires under the 6m beam probably are affecting the beam's pattern to some degree.  It may not be bad enough for you to notice.  If you're concerned about it, it would be easy to replace the metallic guys, one by one, with strong rope, appropriately stretched by turnbuckles.  For such installations I'd recommend double-braided Dacron rope as a minimum, or kevlar-core Phillystran if you want something very strong and permanent.

I don't like "wire" guys, because they'll always resonate *somewhere,* and it's often difficult to predict where.  On large (tall) and heavy towers, often times there's no choice but to use wire guys, but in those cases, the guys can be broken up by insulators every several feet to prevent resonances in the amateur HF bands.

As for the screwdriver antenna as a "home station" HF system, I wouldn't go this way.  For one, it's a rather expensive vertical antenna considering it's not a particularly good one (fine for mobile work, but very small for home station use).  For another, it will require not only a feedline but also a 12Vdc power line.  For still another, if attached to a roof mounted A/C unit, the vibration from the screwdriver as it "tunes" might get really LOUD, and be annoying to anyone living directly below the A/C unit.  In fact, the screwdriver might send that annoying whine sound through the A/C ductwork and sound pretty bad all through the house.  Remember, this is an antenna that makes quite a lot of noise as it tunes.  You don't notice that when it's mounted to a car, especially if you're inside the car!

Also, the screwdriver, in order to work worth a darn, requires an extensive counterpoise system.  Just bolting it to a rooftop A/C unit will provide a bit of a counterpoise, but it will work a lot better with many quarter-wave (cut to resonance) radial wires under it, and those wires will occupy more space than the screwdriver antenna itself -- not to mention providing quite an obstacle course to walk around when you're on the roof.

With a roof available for a home station, I'd recommend something more efficient and self-contained like possibly one of the large, half-wave vertical antennas made by GAP, Hy-Gain, Cushcraft, et al.  The other advantage to such a system is that it will provide you with "instant bandswitching" capability, which the screwdriver will not -- the screwdriver takes a while to tune from one band to another, and going from 40m to 10m can take quite a long time.  Frustrating, when you have little time to operate as many of us do.

WB2WIK/6



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KD7SIX
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Posts: 24




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« Reply #3 on: November 25, 2002, 09:46:21 PM »

Tim the mast is strapped to the corner/side of the AC unit it also sets on one of those Radio Shack adj. mast mounts. It has no other grounding. Should I run additional grounding?
WB2WIK, well I guess I'll need to replace those guy wires, I'm just going to have to add something above the 6 meter yagi to make it worth wile, hi hi. Maybe put the Diamond X510MA dual band vertical that I have on top? Or since the screwdriver idea was not so good would it be a good place for a HF vertical? I was looking in my AES catalog and Diamond has the CP6A just under 10 lbs. Or would these antennas mess with the yagi below it or vise a versa?
---
Scott KD7SIX
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WB2WIK
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Posts: 20560




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« Reply #4 on: November 26, 2002, 04:28:53 PM »

If you put a Diamond CP6A atop that Radio Shack 20' telescoping mast, along with a rotor and a six meter beam, you won't have to wait long to see it all very close up, as it collapses on your roof.

The R/S slip-up masts are not nearly strong enough to support a CP6A, regardless of how well the mast is guyed.  The CP6A may only weight 10 lbs, but it's a huge wind load at over 15' tall, and when it starts to whip in the wind, it will buckle the R/S mast section immediately below it.  It will buckle it even faster if the mast is tightly guyed, as the guys alone are already pulling down on it with considerable force.

The CP6A isn't too bad, but I'd install it down on the roof, not up on a 20' mast.  Or, at least not that particular 20' mast.

Frankly, for the same cost, I'd go with a different HF vertical like a GAP Titan, Hy-Gain AV-640, something like that.  Those are better built antennas (albeit heavier ones) that will handle legal limit power, should you ever have occasion to run that.  The CP6A is very light duty and won't handle any power.  But if you do install a multiband HF vertical, don't put it on top of a 20' R/S telescoping mast!

WB2WIK/6
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KD7SIX
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Posts: 24




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« Reply #5 on: November 27, 2002, 04:03:10 PM »

I'm sorry for the confusion... the mast is 2" steel pipe, it only sits on a Radio Shack mast mount. The pipe is 20' tall and guyed in 8 places, 4 in the middle 4 on top. I put it up in hopes of it never coming down. So if I do take it down to replace the guy wire, I was wondering what I could mount above the 6 meter beam? Or would it just be more chance of causing some type of interference also.
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W5WJP
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Posts: 157




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« Reply #6 on: December 02, 2002, 09:17:38 AM »

If you have a good rotor (something like Yaesu G-450 or better), you might want to consider a Force 12 C3S. It is a triband yagi similar to thier C3 except that it only has a 12 foot boom, not too much bigger than your Diamond 6m. Mount the 6m on top of you mast, then about a 1/2 wave length (for 6m) down mount the C3S. Force 12 has built quite a reputation for excellent antennas and soild construction. All pop rivet assembly and very solid. Our club has a C3 on a 100 ft tower. We routinely get questioned if we really are QRP.


73,
W5WJP
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N2MR
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Posts: 13




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« Reply #7 on: December 03, 2002, 06:51:28 AM »

"It has no other grounding. Should I run additional grounding?"

Have you considered lightning appeal?

                         Mark N2MR
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KD7SIX
Member

Posts: 24




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« Reply #8 on: December 03, 2002, 09:52:18 PM »

Can I just run a ground strap and put an 8' rod in the ground, wich would be at least 50' away from the antenna. Should I not have the mast strapped to the AC unit?
That's why I posted this topic, I would like to set it up right.
BTW the wire guys don't seem to be bothering the 6 meter yagi, the band opened yesterday for about 30 min. and I talked to Texas, Oklahoma and Louisiana from Las Vegas NV. My very first DX contact was WW2R in Texas, what a blast.
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N6AJR
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Posts: 9913




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« Reply #9 on: December 17, 2002, 12:07:21 AM »

Remember, none of us have the perfect antenna instlation, although some are better than others.  first priority is safety, then performance and cost and so on.  new theory of thought on grounding, ,,good grounds tend to send up "streamers" which draw lightning strikes ( new info in the last year or so.) so not all of us believe in lightning grounds.  all of do belive in electrtical grounds for the equipment.

remember any antenna is better than no antenna and the most expensive is not always he best.  look into a wire antenna like the WIndom (look at buxcommco.com    he has a great design there and all you need is some wire and a 4 to one balun which he sells for $15 or so). its an off center fed dipole good on most of the hf bands with out a tuner, and the rest with a tuner, cost is less than $30 and it is a BOOMER of an antenna..higher is better with this one but it will work ok low to.. do what you can.

I suggest buying lots of books on home brew antennas when you see them and go from there, its a hobby, not rocket sience.  just follow the other guys directions and the work..


have fun and enjoy  73  tom N6AJR
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KD7SIX
Member

Posts: 24




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« Reply #10 on: December 17, 2002, 01:24:26 AM »

Thanks, it is confusing!
I am checking out the Gap TitanDX, they say not to ground it. I do have my radio and power supply grounded to an 8' copper covered rod hammered in the ground, with very short braded cable leads. Thanks for that web site; I'm asking Santa for a KentTP-1 Twin paddle Morse key for Christmas, an expensive HF antenna will have to wait a wile. That Windom looks like just the ticket till then!
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W1JQ
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Posts: 3




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« Reply #11 on: November 02, 2003, 08:26:06 PM »

If you want an all-round HF antenna for as little effort as possible, go with a G5RV.  It's easy, it gets you on just about all the bands.  There are articles all over the place that tell you how to make one, or you can buy one.

Now, there are plenty of BETTER antennas.  I've just taken down my G5RV; I'm now using half a dozen wire antennas, all of which do the particular things they're supposed to do much better than the G5RV ever did.  But if you want a simple beginner's antenna, I don't think you can do better.  You'll outgrow it in a year or two, but that's part of the fun.

73 and good luck,

Mike
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