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Author Topic: 40 METER HAMSTICK DIPOLE FOR MARINE USE  (Read 3330 times)
KE5YKH
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Posts: 27




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« on: August 12, 2012, 12:17:35 PM »

I have been trying to install a hamstick dipole on my 34' Silverton Convertable without success.  It is driving me crazy!  Based on my watt/swr meter the antenna loads fine but It just does not get out???  Made a bracket where the driven element is isolated from ground, the dipole is about 20' high above the saltwater, swr is almost flat(with a tuner) and the meter shows about 100 watts output, but cannot make a contact???

I use the thru-hull ground plate on the boat for grounding. 

Brought the antenna home to further test it and have the same problem.....can't make a contact or it is very difficult to make one.

There must be someone out there that can HELP me.  Just don't understand why this antenna will not work?
TNX
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G8YMW
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Posts: 191




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« Reply #1 on: August 12, 2012, 01:39:29 PM »

66ft versus 14ft?
How about a wire dipole from the handrail at the front (insulator) up over the top and down to the stern.
If the dipole is too long , make it a cage dipole.
Or a vertical with the boat's bodywork as the earthy side
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KB1GMX
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Posts: 711




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« Reply #2 on: August 12, 2012, 01:48:13 PM »

First the ground side of the dipole shout not be common with
the mounting pole/plate.  It would help is the feed point and a 1:1
feeding the two hamsticks.


Next problem, Pattern!

You using an inefficient {less than 25%} dipole some 20ft off the water
and the water is salt.  That means you radiation, what there is of it,
is straight UP.

Try a vertical single hamstick with a railing for a ground and see if that is better.

The wire to the ground plate is too long to mean anything but a lighting ground.
If anything it may be the part that actually radiates.

Allison
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VA7CPC
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Posts: 2357




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« Reply #3 on: August 12, 2012, 02:11:44 PM »

I have been trying to install a hamstick dipole on my 34' Silverton Convertable without success.  It is driving me crazy!  Based on my watt/swr meter the antenna loads fine but It just does not get out???  Made a bracket where the driven element is isolated from ground, the dipole is about 20' high above the saltwater, swr is almost flat(with a tuner) and the meter shows about 100 watts output, but cannot make a contact???

I use the thru-hull ground plate on the boat for grounding. 

Brought the antenna home to further test it and have the same problem.....can't make a contact or it is very difficult to make one.

There must be someone out there that can HELP me.  Just don't understand why this antenna will not work?
TNX

As the previous post says, a 40m hamstick will never work _well_ -- it's too short to be efficient.   HOWEVER, if you can find a strong (S9+) 40m signal, and the guy sending it is using 100 watts, he should be able to hear you.

. . . What kind of tuner are you using?

. . . How is is connected to the antenna and to ground?

You say you've built a _dipole_ - - that means you're using _two_ Hamsticks, base-to-base, with one being the "hot" side (center wire of coax) and the other the "ground" side (braid of coax).   

. . . Is that your arrangement?

If you have _one_ hamstick, the previous post is right -- the Hamstick will do better mounted on a s/s rail, using that rail for a counterpoise.  Center of coax to the Hamstick, ground braid to the s/s rail.

. . . DO NOT TOUCH THE RAIL WHILE TRANSMITTING !!!!!

If you're using coax feed to the antenna, ignore the normal "marine installation" shibboleths about "seawater grounds".   They're not relevant in your situation.   I'd disconnect the antenna tuner from the thru-hull.

We need more information . . .

       Charles   / "right galah", Morgan 36 Out Island sloop

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WB6BYU
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Posts: 13017




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« Reply #4 on: August 12, 2012, 04:40:57 PM »

Quote from: KE5YKH

...swr is almost flat(with a tuner)...





What is the SWR without a tuner?

A Hamstick dipole for 40m, when properly tuned for the operating frequency, might be about
10% efficient.  That's enough to make contacts in good conditions - it's more radiated power
then when I run my QRP rig at 5 watts - but you'll have best results calling strong stations
when there isn't a lot of background interference.

When operated off the resonant frequency, the efficiency of the system (antenna + coax +
tuner) will decrease.  It's probably OK within 100kHz or so of the resonant frequency when
used with a tuner, but beyond that the efficiency can be very low, even though you may be
able to get a low SWR using the tuner.


The first step is to install it properly:  ideally both sides of the antenna are insulated from the
support mast, connected only to the two sides of the coax.  A 1 : 1 balun at the feedpoint helps,
too.  That prevents a lot of stray paths RF paths that can make it difficult to tune.

Then carefully tune the antenna to the center of the desired operating band WITHOUT THE
TUNER.  Start with the stingers inserted about 1/2" to 1" into the ferrule.  Both sides must
be as close to the same length as you can manage.  Check the SWR across the band - an
SWR analyzer is convenient, but you can just measure the SWR at various points to see
if it is resonant somewhere in the band, or off one end or the other.  You are looking for
the point of minimum SWR:  if it is to low in frequency, shorten the whips slightly and try
again.  If it is too high in frequency, lengthen them.  If you can't find a dip at all, then either
the antenna is too far from resonance or you have a short or open in your coax or your mount.

Once you get the point of minimum SWR (which might not be 1 : 1) close to your operating
frequency, then you can use your tuner for fine adjustments.  Because of the low efficiency,
you're still basically running QRP, so don't expect weak stations to hear you.

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N4CR
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Posts: 1650




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« Reply #5 on: August 12, 2012, 04:50:04 PM »

Which is why so many sailboats hook the ground on a tuner near the backstay, insulate the backstay on both ends and hook the tuner to the backstay for the driven element.

That is a combination that is proven to work. The backstay insulators are a bit pricey but it's the price of admission to sailboats. They are expensive.
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73 de N4CR, Phil

We are Coulomb of Borg. Resistance is futile. Voltage, on the other hand, has potential.
KG4RUL
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Posts: 2685


WWW

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« Reply #6 on: August 12, 2012, 05:10:41 PM »

Quote from: KE5YKH
Then carefully tune the antenna to the center of the desired operating band WITHOUT THE
TUNER.  Start with the stingers inserted about 1/2" to 1" into the ferrule.  Both sides must
be as close to the same length as you can manage.  Check the SWR across the band - an
SWR analyzer is convenient, but you can just measure the SWR at various points to see
if it is resonant somewhere in the band, or off one end or the other.  You are looking for
the point of minimum SWR:  if it is to low in frequency, shorten the whips slightly and try
again.  If it is too high in frequency, lengthen them.  If you can't find a dip at all, then either
the antenna is too far from resonance or you have a short or open in your coax or your mount.
When you are adjusting the stingers, make absolutely sure the the stinger does NOT extend into the wire coil of the antenna shaft.  If this is the case, you will need to trim the end.  The stinger is HARD metal so do not try to cut with pliers.  I use a small cutoff wheel in my Dremel tool for this.  If you let the stinger extend into the coil you may cause excessive heating and potentially destroy the wire.
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K7RBW
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Posts: 386




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« Reply #7 on: August 13, 2012, 06:49:31 AM »

It looks like it's been said before, but I'll add my comments on using a hamstick dipole @ 40 m: good luck. I haven't been able to get very far with my land-based version so, I'm guessing that there's little you can do on a boat to make a 15-foot dummy load (i.e. your hamstick dipole) radiate any better. The whips are such a small part of the overall wavelength that I'd be surprised if you had any better than 1% efficiency.

Also, even when they are working well (relatively speaking) they have a very narrow band of resonance (which is probably how they get anything out at all). Using a tuner to widen that, just means that more of your radio's power will be used to heat the tuner. It doesn't change the properties of the antenna.

The suggestions for using a vertical antenna (e.g. the backstay of a sailboat or a fiberglass whip) would seem to show the most promise on a boat that size (since it's not long enough for a full dipole). It seems like it would be more constructive to take advantage of the infinitely large, highly conductive ground plane, that you're sitting on and using it to your antenna's advantage as opposed to its disadvantage.
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W5DXP
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« Reply #8 on: August 13, 2012, 07:14:07 AM »

One more example that hamstick dipoles are dogs on 40m and 80m. I don't know of any ham who has ever been completely happy with one.
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73, Cecil, www.w5dxp.com
The purpose of an antenna tuner is to increase the current through the radiation resistance at the antenna to the maximum available magnitude resulting in a radiated power of I2(RRAD) from the antenna.
KE3WD
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Posts: 5694




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« Reply #9 on: August 13, 2012, 08:48:38 AM »

If you're using coax feed to the antenna, ignore the normal "marine installation" shibboleths about "seawater grounds".   They're not relevant in your situation.   I'd disconnect the antenna tuner from the thru-hull.

We need more information . . .

       Charles   / "right galah", Morgan 36 Out Island sloop



My first thoughts also.  The dipole is a balanced antenna and does not need an Earth Ground to function.

The dipole made from two hamsticks is what we call a Compromise Antenna.  SWR is only one part of the situation, a Dummy Load is a perfect 1:1 SWR, but don't expect it to be able to transmit and receive much. 

Efficiency of the antenna system comes into play here, as well as Capture Area, and the compromise antenna system of two hamsticks back-to-back is sorely lacking in both of those departments. 

Try removing that Sea Ground, though, and see if that doesn't help a wee bit. 


73
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W8JX
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Posts: 5444




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« Reply #10 on: August 13, 2012, 08:56:03 AM »

One more example that hamstick dipoles are dogs on 40m and 80m. I don't know of any ham who has ever been completely happy with one.

Well you do now. I have been pleased with how my 40m hamstick type antenna has worked mobile as a vertical. I cannot say same about 80 though.
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AA4PB
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Posts: 12672




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« Reply #11 on: August 13, 2012, 09:03:55 AM »

I've used a Hamstick dipole on 40M with QRP CW and made plenty of contacts around the states. I don't believe the efficiency is as bad as some people think. A 40M Hamstick dipole is about 1/4 the physical size of a full sized 1/2 wave 40M dipole.

I did not use a tuner. I had a small balun located at the feed point and about 30 feet of RG174 coax down to the transceiver. The Hamstick dipole can be adjusted to get a 1.5:1 or less SWR over a small portion of the band. I found that above 15 feet above the ground the tuning didn't change significantly so you can tune it near the ground and then raise it higher without requiring retuning.
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KE3WD
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Posts: 5694




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« Reply #12 on: August 13, 2012, 11:39:33 AM »

I've used a Hamstick dipole on 40M with QRP CW and made plenty of contacts around the states. I don't believe the efficiency is as bad as some people think. A 40M Hamstick dipole is about 1/4 the physical size of a full sized 1/2 wave 40M dipole.

I did not use a tuner. I had a small balun located at the feed point and about 30 feet of RG174 coax down to the transceiver. The Hamstick dipole can be adjusted to get a 1.5:1 or less SWR over a small portion of the band. I found that above 15 feet above the ground the tuning didn't change significantly so you can tune it near the ground and then raise it higher without requiring retuning.



Those of us who enjoy both the CW mode and QRP seem to be able to make lots of contacts, even when  loading Aunt Maude's bedspring. 

Just sayin'...

73
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W5DXP
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« Reply #13 on: August 13, 2012, 12:47:33 PM »

Well you do now. I have been pleased with how my 40m hamstick type antenna has worked mobile as a vertical. I cannot say same about 80 though.

Note that I was talking about a 40m hamstick dipole. Are you using a 40m hamstick dipole for 40m mobile operation?

I've used a Hamstick dipole on 40M with QRP CW and made plenty of contacts around the states. I don't believe the efficiency is as bad as some people think.

IMO, you can credit CW for your contacts, not the hamstick dipole. Try it for SSB and report back to us.
« Last Edit: August 13, 2012, 12:54:58 PM by W5DXP » Logged

73, Cecil, www.w5dxp.com
The purpose of an antenna tuner is to increase the current through the radiation resistance at the antenna to the maximum available magnitude resulting in a radiated power of I2(RRAD) from the antenna.
W8JX
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Posts: 5444




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« Reply #14 on: August 13, 2012, 12:51:22 PM »

Well you do now. I have been pleased with how my 40m hamstick type antenna has worked mobile as a vertical. I cannot say same about 80 though.

Note that I was talking about a 40m hamstick dipole. Are you using a 40m hamstick dipole for 40m mobile operation?

No I did say as a mobile vertical.
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