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Author Topic: Gap Antenna Products  (Read 611 times)
VE4HST
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Posts: 88




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« on: November 05, 2001, 08:03:06 PM »

I am ordering the Gap Challenger antenna and will be ground mounting it using a ground counterpoise of radials ( they suggest 3) but I will use at least 6 or more.  Will this make a difference, or should I go with the recomended 3??  Also has anyone used their Quick-Tilt for ground mounting.  It appears on page 160 of the Nov. issue of QST.  It is expennnsive, but very neat and a easy way to raise and lower an antenna. Also is there such a thing as "the best wire to use for radials"?  I have over 500 feet of 16 guage solid vinal covered wire.  Will this do or is their something out there that is better.  I plan to bury the radials just under the grass.  Also the coax feed line, I plan to put that into a PVC pipe for the 20 feet to the house, and also bury it under the grass. Is there a special coax to use underground, taking into account I live in Winnipeg Canada and it gets very cold here in the winnter. I also must protect it from moisture of course.  Also, has anyone used Gap's Guy Material Kit?

All ideas, suggestions, and or comments would be appreciated.
Thanks

VE4HST
73's
Harry
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N6AJR
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Posts: 9913




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« Reply #1 on: November 05, 2001, 09:00:24 PM »

Well, I'm not the expert, but here goes. The wire should be fine, copper last the longest buried, and some folks say the more radii the better,( is plural of radial radii? i hope so) and some folks say they don't help at all, my observence is they help and the more the better up to around 100 or 120 and then its a bit much. I think I would go for at least the 6 on the longest freq you plan on using (quarter wave) or 6 of the longest that will fit.

 Some folks also put multi contact point copper ground wires on big pieces of chicken wire and burry them in an attempt to make it a grounded area, not just radials. You mow the grass real short, hook the wires to the chicken wire and then to the ground on the antenna, you use coat hanger U's to pin the wire to the ground then cover with an inch of dirt or potting soil, and the grass grows back through it and not so much digging that way.

I am not familar with the specific tip over mount, but I losen the clamps on my 5 band vert here and lift it off the pipe( I undo one guy rope first) and then lean it against the other two guy ropes an "walk" it down to work on it, so this should be even more convienient. I use rope to guy it as it gets windy where I live, and rope guys seem to help.

If you put the pvc pipe in with turn down ends to keep the weather out you can probably get away with  regular coax, but that short of a run, you should spend the extra couple of bucks and get direct burial wire and put that in the pvc pipe, it will last longer (seal the ends well on the coax connectors, prevent water intrusion. It will also probably have less loss than standard coax and that also helps in recieving and transmitting.  Remember that if you have stucco on your house ther is most likely chicken wire under neath so set the antenna as far as you can over that-a-way.

 Remember the rules on the antenna...,any antenna is better than none, the bigger the better, the higher the better, the cheeper the better.  If you don't have to shoo penquins off the roof it ain't cold enough for antenna work, if it is still standing in the spring it ain't big enough, some one elses is always bigger, better, more expensive... ad infum ....

I hope this helps, and I didn't even mention the word counterpoise..hi hi.  Have fun, play with this and see what works best for you.  You don't have to worry about birds roosting on a verticle.Smiley

tom N6AJR
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KE9IN
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Posts: 10




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« Reply #2 on: November 05, 2001, 09:06:34 PM »

Well Harry, the Gap Challenger is actually more of a vertical dipole and those three radials are what tune the antenna on 40 meters. They are supposed to be insulated and capped on the ends so they do not contact ground and de-tune 40 meters. If you call the factory, they will give information to lengthen or shorten those three wires to get 40 meters where you want it to resonate. Mine was extremely sensitive to nearby objects, so much so that I never was able to find a satisfactory location to get all the bands resonate where they should be. Good luck and 73, Ron
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N6AJR
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« Reply #3 on: November 05, 2001, 09:14:09 PM »

Re : my previous post.  This would apply if you were using a "normal " verticle, so ...  never mind Smiley  tom  N6AJR
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VK5CC
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Posts: 5




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« Reply #4 on: November 06, 2001, 07:53:21 AM »

The challenger is a vertical dipole and as such the 3 25' wires are used to resonate the antenna on 40m. This is a wonderful antenna and mine is ground mounted and goes like a train. If you want 17m just cut the bottom out of a standard coathanger(approx 5inches)and attach it onto the higher of the 2 lower dipole elements--this will give you an swr of around 1.5to1 and watch the dx roll in.This antenna is best on 15/17/20/40m--80m is ok for what it is and 10/12m it is not fantastic however when certain conditions prevail these 2 bands do go very well. I have found on 40m that my dipole at 50' is up to an s unit stronger on tx but the sig to noise ratio on the challenger is so good that i can hear mobile stations stateside on the gap that are barely audible on the dipole but as the night rolls on the gap keeps me with the dx that has long gone on the dipole. Have a great time with this outstanding vertical--i know i have and continue to--cheers from chris vk5cc
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N1OU
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Posts: 70




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« Reply #5 on: November 06, 2001, 11:26:26 AM »

Harry,

I've had my Challenger up for several months now and I think its great!  Pretty much any insulated wire will work for the counterpoise.  I suggest you don't bury it, just lay it across the grass and peg it down with plastic tent stakes.  As the other replies mention, this is a counterpoise for 40M, not a set of radials, so follow the Gap instructions.  If you have problems, call Richard at Gap--they are great to work with on the phone but don't answer e-mails.

As to coax, use "direct burial" type and either lay it out flat across the lawn or bury it a few inches.  Its pretty rugged stuff.  Seal the ends with heavy duty tape or coax-seal to keep moisture out of the connections.

I hope you'll read my reviews of the Challenger under the product review section of eHam.  They are a bit long, but I think they'll help you.

Enjoy your Challenger.  Its one of the best verticals available.

Gordon, N1OU (formerly WD4FGH)
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N1OU
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Posts: 70




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« Reply #6 on: November 06, 2001, 02:22:42 PM »

(for the post from Chris, VK5CC)

Can you give more/better details about your coathanger mod for 17?  I'd love to have the band and, in my opinion, its the only big problem with the Challenger.

Gordon, N1OU
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VK5CC
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« Reply #7 on: November 06, 2001, 11:16:36 PM »

yes mate to get 17m on the challenger you just extend the 12m dipole which is the shorter of the 2 dipole elements running down the mast from the gap feedpoint by about 5inches or use the bottom section of a standard coathanger and clamp that on to the 12m dipole element which extends it by about 5 odd inches and you will be on 17m which is another great dx band. I have told rich and george about this as all they need to do is extend the length of the aluminium tube and then 17m would come as well on the challenger.There is no benefit to adding more radials to the 3 recommended as these wires are not radials or a return path for ground currents, they simply extend the bottom half of the antenna to achieve resonance on 40m--hence an assymetric feed vertical dipole. the challenger has no competition in the vertical market--it is the best option for an efficient multi-band vertical dipole! cheers for now feel free to write to me at  christo@senet.com.au if you need any further assistance. best 73 from chris vk5cc
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WB2WIK
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« Reply #8 on: November 07, 2001, 06:36:23 PM »

The Challenger is indeed a great antenna.  I had one of the first that GAP ever sold, I think, back in 1990.  At least, at the time I didn't know anyone else who had one, and never heard one on the air, ever, prior to my installing one at home.

It worked splendidly, although I did fuss with it quite a bit regarding the exact location.  First installation was ~25 feet from a metallic chain link fence that seemed to detune the Challenger.  I moved the radials all around and did other silly things which had no effect, until I finally moved the whole antenna, to be about 40 feet away from the same fence, and that solved the problem.

Weak links (at least they were weak links on the Challenger DX-VI, don't know if they've strengthened these lately):

-The insulated wires which interconnect the elements that are supported off the main vertical element are not strong enough for severe UV (sun) radiation, or for birds landing and pecking on them.  With my Challenger, the wires were all broken within about three years from a combination of the insulation literally falling away from the wires (UV did that) and birds.  Had to replace them all, and when I did, I used stronger wiring.

-The PVC (or whatever they are) standoff insulators which hold those side elements away from the main vertical element are apparently also not very immune to UV, as they, too, started to crack and fall off after about four years.  This caused a nasty byproduct, which was that the lower end of one of those elements blew around in the wind and shorted against the main vertical radiator while I was transmitting with 1500W, and caused arcs, sparks, blue flashes of light, bits of aluminum being burned away, and some interesting results in my amplifier.  No permanent damage resulted, but I did have to replace those standoff insulators.

-And I think everyone knows about the frailty of the top loading capacitor which resonates the Gap on 80m.  Mine never failed, but one must be rather careful with it.

73 de Steve WB2WIK/6

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NI0C
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« Reply #9 on: November 08, 2001, 01:02:20 PM »

I'll address the issue of the coax feedline to your vertical.  I've had my Cushcraft R-7000 vertical up for 5 years now, with 185 feet of coax feedline.  I used a combination of RG213 and LMR-400 (connected together with connectors sealed with liberal amounts of Coax-Seal).  At first, I had the cable on the ground, but squirrels chewed through a section of the LMR400, nearly severing it.  This happened after only a few weeks.  I replaced the damaged section and put most of it in 3/4 inch PVC electrical conduit.
If I were doing it again, I'd use a larger size conduit to make the elbow bends easier.  In summary, I'd recommend using the best coax you can afford, and protecting it with the PVC pipe.  Good luck with your installation.  
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N1OU
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Posts: 70




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« Reply #10 on: November 15, 2001, 02:54:38 PM »

(back to Chris, VK5CC)

Thanks for more info on the 17 meter mod.  I tried it and ultimately found that, for my installation, a piece of clothes hanger wire extending down 14 inches on the lower tuner rod did the trick -- 1.4 SWR across the band!  Called CQ and got a quick response from W0LAV in Missouri, about 1400 miles away.

Just for the fun of it I ran a quick SWR check across the bands and found no changes at all, not even on 12 meters.  

Thanks again, Chris, maybe we'll meet up on 17M one of these days!

73's

Gordon
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