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Author Topic: QRP on a Kayak  (Read 3073 times)
9V1VK
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Posts: 15




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« on: July 19, 2006, 09:29:53 AM »

I have a Fujita folding kayak and an Elecraft KX1. I'd like to introduce them together and spend an afternoon as 9v1vk/mm.

I have read that running a vertical over saltwater is ideal.  So my idea is to mount a wire vertical for 20m on the rear of my kayak.  This is not too hard, as I have a longish fishing pole that i could probably get the wire up 10m or so for a 1/2-wave 20m.

The question is the radial system.  I have two options basically and I have read various things about both.

1) My fujita 480ex is 4.8m long.   I could run the 5m radial along the edge of the kayak, so it is elevated about 5-6" above the water, laying on my pvc-fabric deck.  I have read accounts that the radial should be ABOVE the water, not in or under it.

2)  I could instead drag the 5m vertical through the water behind me, suspended on tiny bobbing floats.

3) or I could do both 1 and 2.

Any recommendations/advice/experiences to suggest?
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W3JJH
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« Reply #1 on: July 19, 2006, 11:52:25 AM »

MM operation requires a location on the high seas.  How far out in the Main Strait would you have to paddle in order to be outside of the 3 nm limit claimed by Singapore and the 12 nm limit claimed by Indonesia.
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AA4PB
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Posts: 12847




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« Reply #2 on: July 19, 2006, 12:31:02 PM »

I'd suggest making the radial (counterpoise) 1/4 wavelength long and keep it out of the water. Make your vertical something a little less than 1/2 wavelength because the KX-1 tuner will have a hard time with the very high impedance of a 1/2 wavelength antenna. If you make it a bit shorter then the impedance will come down to something the tuner can handle and still be high enough to minimize loss in the ground counterpoise.
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WB6BYU
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Posts: 13251




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« Reply #3 on: July 19, 2006, 01:48:00 PM »

You don't need a 10m vertical - 5m will be more than enough,
and shorter wires will work as well.  The radiator and/or
the radial can be inductively loaded to reduce their length.

My suggestion would be to attach the radial wire to the
underside of the deck so it is out of the way.  But it
might be worth doing some experiments - compare the
signal strength between that and an insulated wire dragging
in the water astern.  If you can't tell any difference,
go for what is simple.  (You may have to replace the
radial wire after each use if it is in the water, though.)
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AA4PB
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« Reply #4 on: July 19, 2006, 05:33:48 PM »

The radiator and/or the radial can be inductively loaded to reduce their length
-------------------------------------------------
All at the cost of reduced efficiency, but certainly it will work.

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AB9LZ
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Posts: 198




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« Reply #5 on: July 19, 2006, 06:06:29 PM »

I tried this with my Nautiraid, a SWL20+ and a quarter wave whip mounted on the rudder crossbar. I didn't test different configs, I just threw an 1/8 wavelength counterpoise overboard. Unfortunately it worked too well, as my first Q from the gulf of Mexico was with Argentina... I had quickly drifted into the Tampa bay ship channel (off Egmont key) with a bad current wind combo working against me. It was too much to handle and didn't finish the QSO. In calmer waters I was unable to raise anyone else... go figure.


Have fun!

73 Mark,
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AB9LZ
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Posts: 198




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« Reply #6 on: July 19, 2006, 06:09:53 PM »

Btw even a quarter wave whip at 20m introduces an unsettling momentum in the boat, takes a while to get used to, and if there is any wind, introduces  significant amount of drag.
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W3LK
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Posts: 5639




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« Reply #7 on: July 21, 2006, 12:33:27 PM »

Having done some calm water kayaking with my son-in-law, I cannot imagine trying to operate a ham rig and paddle a kayak at the same time; especially a CW rig.

73,

Lon - W3LK
Baltimore, Maryland
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WB6BYU
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Posts: 13251




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« Reply #8 on: July 21, 2006, 03:27:33 PM »

The practical question, of course, is how tall of a support
can one manage on a kayak.  Given the good ground conductivity,
I don't think there will be much lost efficiency in using
a quarter wave rather than half wave end-fed radiator,
but a huge difference in the effect of the required mast
swaying as the kayak rocks in the waves.  A 10m mast
provides a lot of mechanical advantage compared to the
cross-sectional dimensions of a typical kayak, so it
wouldn't require a lot of sideways wind pressure to roll it.

I suspect that a more practical maximum mast height would
be 3 to 4m, which is less than a quarter wavelength.  Even
at that length, an efficient base loading coil won't cause
as much loss of efficiency as it would for a ground-mounted
vertical of the same type because the earth losses are
lower.  A better solution, though, would be to run the
wire to the top of the mast then angled forward down
towards the bow to make up any additional length required.  
(The wire shouldn't come down lower than the midpoint
of the mast, however.  If that isn't enough, some
inductive loading can be added, perhaps at the top of
the mast.)

One approach that has worked for me is to connect a base
loading coil between the antenna wire and the counterpoise(s)
after lengthening the antenna as much as is practical
up to a quarter wavelength.  In this case the radial
may be shorter than a quarter wavelength also.  Add
enough coil to bring the combination to resonance, then
make a coupling link from 2 or 3 turns of hookup wire
around the main coil and connect this to the coax.  The
number of turns on the main coil sets the resonant
frequency, while the number of turns on the link sets
the impedance.  This may not be quite as efficient as
other forms of loading, but it is fairly easy to adjust
the SWR.  I've used it for a 80m shortened vertical and
it worked well.
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AB9LZ
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Posts: 198




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« Reply #9 on: July 25, 2006, 09:08:41 AM »

"Having done some calm water kayaking with my son-in-law, I cannot imagine trying to operate a ham rig and paddle a kayak at the same time; especially a CW rig."

While a folding kayak may sound fragile and unstable, it is indeed a very capable ocean going craft. I've spent the night in mine snuggled down on the floorboards on more than one long crossing, assured my trusty boat would ride like a duck in even the worst conditions.

Under calm conditions I can even stand in mine and fly fish.

I've just refined and tested a new setup, the key slips under a bungee on the right coaming, I already have a plastic write-on chart holder, I use a grease pencil for copy. The SWL20+ is in a converted small pelican case that sits in the swampwater on the floor.
I've moved the whip from the rudder crossbar to the back of the cockpit coaming with modifications to the spray skirt. Conditions permitting (light winds) hope to run it during the 8 mile crossing to S. Manitou island on northern lake michigan next week. The freshwater may be problimatic tho as it makes for a poor ground plane. If the marine moblile doesn't work out I still plan to operate from the summit of the 500ft dune on the island.

I'll post photos when I get back.

73 Mark.
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AE6RF
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Posts: 151


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« Reply #10 on: July 25, 2006, 01:24:58 PM »

>Having done some calm water kayaking with my son-in-
>law, I cannot imagine trying to operate a ham rig and
>paddle a kayak at the same time; especially a CW rig.

Isn't it wonderful to have a hobby that isn't limited by your imagination?

Donald
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W3LK
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Posts: 5639




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« Reply #11 on: July 25, 2006, 04:42:15 PM »

<< Isn't it wonderful to have a hobby that isn't limited by your imagination? >>

Or by the (IMHO) idiocy of putting a mast taller than the vessel is long on a narrow-beamed kayak that has no keel or counterbalance to offset it. Not to mention trying to paddle with only one hand while operating a CW rig.

The FIRST priority on the water is safety.

Thanks for the really stupid remark.

73,

Lon - W3LK
Baltimore, Maryland
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AB9LZ
Member

Posts: 198




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« Reply #12 on: July 26, 2006, 07:10:21 AM »

Kayaking, along with many other outdoor pursuits, such as mountaineering, is inherently dangerous. Accepting the risks and mitigating them with skill and physical conditioning is what makes it a very exciting diversion.

If safety... the kind that is had by pure avoidance is your primary concern, look elsewhere.

That said, at my skill level, I don't feel that I could handle a CW qso say in the open ocean off of the Queen Charlottes nor would I try, but on a more protected crossing, no problem... I fish regularly out of my boat, which often requires handling the paddle with one hand and the pole with the other, and if I'm lucky I might even have a fish with big teeth between my legs(!). It's my guess that humans have been managing this scenario quite well for many thousands of years.

So a little CW action in my boat won't kill me, I can think of ten other things that might though.

73 Mark.
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AE6RF
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Posts: 151


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« Reply #13 on: July 26, 2006, 01:33:32 PM »

> The FIRST priority on the water is safety.

If that is the case, don't go there for recreational purposes.

I sail because I enjoy it. Not because somebody is forcing me to go from point a to point b.

Sailing is inherently dangerous. Does that mean I can't ragchew on a 2m HT while I'm doing it?

Fortunately, this sort of choice is left to the judgment of the individual...

... And not subject to the approval, or lack thereof, of some individual posting on the internet.

I for one am glad to belong to a hobby that frequently takes me places where my own imagination can't.

I readily acknowledge that there are folks out there that are a) smarter, b) more experienced and c) more creative than I am. And I enjoy the interchanges such people bring.

Just because *I* can't imagine something doesn't mean that somebody else, with different experience, different knowledge and different motivation can't create it (or do it safely in a manner unknown/unthought-of by me).

Having a ham license doesn't make me an authority on the entire world...

And I'm happy that way.

-Donald

(Most people wouldn't imagine pleasure sailing upwind in 25 knots and 3ft of chop either... (chuckle))
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AB9LZ
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Posts: 198




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« Reply #14 on: July 26, 2006, 02:13:46 PM »

(Most people wouldn't imagine pleasure sailing upwind in 25 knots and 3ft of chop either... (chuckle))

I would!
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