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Author Topic: 40 meter Hamstick dipole  (Read 5421 times)
W3PY
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« on: January 27, 2008, 12:24:45 PM »

I live and travel in a 40 foot diesel pusher and am trying to come up with a small 40 meter antenna I can use when parked. The folks at HRO suggested I purchase 2 hamsticks for 40 meters, configure them as a dipole,  and also sold me a bracket for screwing in the hamsticks back to back horizontally and attaching a coax. I mounted this on a hand rotatable PVC mast which is attached to the ladder at the back of my motorcoach. I am driving it with a Yaesu 857D.

For some reason I am not able to find a resonant frequency. Even my receive capability is way down compared to my ATAS-100 vertical that is on my car.

Is a balun required with the hamstick dipole?

Do I need an antenna tuner?

I have been looking at the MFJ 929 automatic tuner.

Any help on these topics would be greatly appreciated.

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K7RNV
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« Reply #1 on: January 27, 2008, 12:59:20 PM »

Hello from Reno Nv.. Just get a good screwdriver antenna and not the atas 100. Make sure you have a good ground and good coax..You will not be disappointed. You do not need an antenna tuner...73 good luck..Oh yes is you do use the ham sticks, you will need the tuner...73 Bob K7rnv
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WA9FZB
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« Reply #2 on: January 28, 2008, 06:15:31 AM »

I've used a 40-meter Hamstick dipole in a fixed location (middle of Chicago winter -- had to wait for ground to thaw. . . ) and it actually worked better than I was told to expect.  The whips need to be adjusted for the frequency you plan to operate at, and the bandwidth is rather narrow.  If you do not have the whips adjusted to be equal and of the correct length, then it is anybody's guess where it will resonate.

One serious caution with Hamstick antennas -- if you adjust the whip section too far down into the fiberglass section, you could break the helical coil wire inside the section.  I am told that these wires often are installed in such a way as to cross the open center bore of the fiberglass section, and that if you force the whip too far down, it breaks the wire and renders that antenna useless.

Barring that, you should be able to resonate the whipe.  I used an old manual tuner with mine so I could cover all of 40 CW, and was able to work effectively over a radius of about 700 miles on 40 CW, with the dipole only up 5 feet on my patio.

I would recommend the "poor man's balun" of a choke coil of 7 to 10 turns of coax, scramble-wound, at the feed point of the antenna to ensure that the RF stays out of the shack.
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W5GA
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« Reply #3 on: January 28, 2008, 09:47:23 AM »

How about a foldover mount for a 4-BTV.  A friend of mine had one like this years ago on his camper.  Hold it down on the roof with a bracket while traveling.
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N3OX
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« Reply #4 on: January 29, 2008, 09:34:34 AM »

"I live and travel in a 40 foot diesel pusher and am trying to come up with a small 40 meter antenna I can use when parked."

Does it *really* have to be small?  A twenty foot telescoping fishing pole is about $25 bucks:

http://www.bnmpoles.com/index.cfm?fuseaction=category.display&category_ID=8

You could install 33 feet of wire on it inverted-L style if you used light wire, or even easier, load it and match it with a homemade coil at the bottom.

Something like 14-16 turns #10 wire on a 3 inch form spread out over 4 inches of length will work as a low loss loading coil and matching coil on 40m.

You connect the coil between the bottom of the antenna wire and your truck ground.  Coax shield also goes to the truck ground, coax center conductor gets tapped up a couple turns on the coil.

To adjust, you can move the antenna tap up and down the coil near the *top* of the coil.  this will change your antenna resonant frequency... this will be the frequency where the SWR bottoms out.

Moving the coax center conductor tap will allow you to get the SWR down low at the resonant frequency.  By juggling both taps you should be able to get nearly 1:1 at the resonant frequency and cover maybe 70kHz-100kHz of the band under 2:1.  If you want to cover more, move the antenna tap...

The extra height of the antenna will really make it more efficient, but the fishing poles are cheap, light and easy to telescope up with a wire along the side!

Only takes a few seconds to deploy once you're parked and you'll have a lot better time with it than you would with a hamstick dipole.

73,
Dan
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73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
W3PY
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« Reply #5 on: January 30, 2008, 05:50:58 AM »

Thanks much for the info from Chicago. what does "scramble wound" mean?

Also, is there a way without an antenna anlyzer to check and see that I have not broken the wire you referred to. There is a possibility I have done that on one of the elements.

The other folks suggesting other kinds of antennas, I appreciate your effort, but would like to restrict this particular discussion to the hamstick dipole.

I have the Yaesu ATAS120 in addition to the hamstick and am currently not interested in other antennas.
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W3LK
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« Reply #6 on: January 30, 2008, 04:41:40 PM »

<< I have the Yaesu ATAS120 in addition to the hamstick and am currently not interested in other antennas.>>

With all due respect, you are fixated on two of the poorest performing mobile antennas on the market - especially on 40m.

I second the suggestion to use the Hustler vertical. Even bolted to the roof ladder (if you have one) it will far outperform the hamsticks AND the ATAS 120.

Lon - W3LK
Naugatuck, CT
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W3PY
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« Reply #7 on: January 31, 2008, 08:05:58 AM »

Lon:

I am trying really hard not to let this thread turn into a discussion on what antenna is the best antenna for a 40 foot motorcoach.

I am well aware of the virtues of a Hustler. I do not dispute its excellence.

I also have an ATAS120 vertical.

But right now I am exploring the hamstick dipole for 40 meters. I was puzzled by the initial poor results and I am interested in exploring what I can do to improve them. Perhaps such a discussion will prove all the points you are making. But it won't prove a darn thing if you keep trying to divert the subject to a different subject.

Right now I am interested if a balun is required on the hamstick dipole, and also what improvements an antenna tuner might make. Let's try to stay centered on that topic if we might.

I am wondering what the addition of a balun and an MFJ 929 automatic antenna tuner might make?

Smoky
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W3PY
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« Reply #8 on: January 31, 2008, 08:07:25 AM »

Another question I have is how does one test a hamstick to insure that the center wire has not been punctured by inserting the end too far?

W3PY
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W3LK
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« Reply #9 on: January 31, 2008, 08:19:23 AM »

<< I am trying really hard not to let this thread turn into a discussion on what antenna is the best antenna for a 40 foot motorcoach.>>

But if you want decent performance, you DO need the discussion.

<<But right now I am exploring the hamstick dipole for 40 meters. I was puzzled by the initial poor results and I am interested in exploring what I can do to improve them.>>

HamSticks are pretty poor performers on 40m and there's nothing you can do to improve them.

<<Perhaps such a discussion will prove all the points you are making. But it won't prove a darn thing if you keep trying to divert the subject to a different subject. >>

No one was trying to divert the discussion. Excuse me for trying to keep you from wasting your time. BTW, are you going to post a nasty response to the other ham who offered you options to the Hamstick dipole?

I won't waste any further time on this matter.

Lon - W3LK
Naugatuck, CT
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W3PY
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« Reply #10 on: January 31, 2008, 08:34:44 AM »

Lon:

I apologize if my message came across as nasty. I certainly did not intend it that way. I was just getting frustrated that instead of a discussion on hamsticks, I was getting so many other suggestions. You were just the straw that broke the camel's back. I am sorry I chose your post as the point where I tried to make clear my intentions. I understand how you might have felt singled out and I am sorry about my bad timing.

Two years ago I DID ask for help on what would be the best antenna for a motorcoach. I got tons of suggestions and many of them were very helpful, as yours would be if I were still investigating that topic.

I now have several types of antennas I now use that work well on my coach and I am happy with.

There is a long story why I am now interested in seeing what a hamstick dipole can do from a motorcoach, and this is not the time or place for me to go into that.

But I am very interested in exploring the hamstick dipole, not to find the best antenna for my situation, but to address my interest in researching that type of antenna.

Sorry you feel I wasted your time. I appreciate your interest in trying to provide information you felt would help me.

In the meantime, if there are any folks out there who have knowledge about hamstick dipoles, I am quite interested in hearing from you.

Smoky - W3PY - Quartzite Arizona
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W3LK
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« Reply #11 on: January 31, 2008, 02:16:32 PM »

Apology Accepted.

Lon - W3LK
Naugatuck, CT
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W8BNL
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« Reply #12 on: February 10, 2009, 07:22:49 PM »

IT really amazes me how so many people want to "help" others by offering their advice instead of answering the question asked. If someone wants to try an approach that "they" haven't tried yet - let them. And if you have an answer to their questions - answer them. Some of us rely on these forums to be our "Elmers". Sorry for ranting, but I see this sort of discussion in far too many threads.

I for one will be experimenting with Hamsticks soon because I am unemployed and live in a trailer park that won't allow me to hang my G5RV of other long wire. I can't afford anything over $50 and I'll be darned if I am going to quit trying to use my hobby just because of poor economics or logistics.

With that said, I would like to "re-ask" the original question. Has anyone tried to use a balun with hamsticks? I too - need to know!!

many thanks de w8bnl
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WA9FZB
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« Reply #13 on: February 20, 2009, 05:32:36 AM »

I did not use a balun, but I did use a common mode choke at the feedpoint and another where the cable entered the house.  These were just some turns of the coax, scramble-wound and taped.  I had no RFI problems, even though the antenna was out on the patio on a 5-foot mast, close to phone lines, power lines and TV coax.  As I said before, not a great antenna, but I was on the air and did make many contacts.
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AA4PB
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« Reply #14 on: February 20, 2009, 07:14:25 AM »

I've used a HamStick dipole on 40M running 5W CW for a portable setup and it worked quite well. I was able to get the SWR down to 1.5:1 with an antenna analyzer. It takes some patience with a tiny bit of adjustment each time making sure that both ends are identical lengths. The benefit of the analyzer is that you can see what frequency it is resonant on and know which way to go and get an idea of how much of a change to make rather than just hunting for minimum SWR.

I've used it with and without a small QRP balun and didn't notice any difference.

To test a HamStick, I'd test one at a time mounted over a counterpoise as a vertical. See if you can adjust it to resonance.

73, Bob
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