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Author Topic: Antennas for a mini DX pedition to Cook Islands?  (Read 4762 times)
AG1LE
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« on: December 25, 2012, 03:13:39 PM »

I am planning a  trip to Rarotonga, Cook Islands next spring.  I am hoping to get a local ham licence and work some DX contacts while there.

I have Flex3000 and Elecraft KX3  as possible radios to take with me.  My favorite modes are SSB and digital (PSK31, JT65A, etc).
Airline only allows for luggage with max 50 lbs and  62" max total linear dimensions (length + width + height). 
I have done some internet searching for antennas  that would bring most bang for the buck. 
It looks like vertical dipole located very close to beach are most commonly used  antennas for this kind of DX peditions.

I am asking for expert advice here:

1) what bands are best for DX contacts  in early April from South Pacific?

2) what kind of antennas should I pack for this trip given these weight and size constraints?   

3) what else should I do to prepare for the trip?  Any  tips or advice ? 


73
Mauri  AG1LE

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AJ4RW
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« Reply #1 on: December 25, 2012, 05:04:58 PM »

I do a couple of one day "funxpeditions" to some coastal islands around northern Florida and southern Georgia each year.  I've been doing this for several years.  I use the Buddipole which serves me well and is very lightweight and small when collapsed plus customer service has been great.  Budd Drummond who owns Buddipole, K3FF goes to the Carribean a couple of times a year with a team and uses only his buddipole setup.  I have the 16' mast and a large carrying bag supplied by Buddipole.  You're suppose to be able to fit everything in the bag but I put the coils, guying kit, cable and small stuff in a small supplemental carrying bag.  I'd say the length is about 4 1/2' and the bag weighs less than 25 lbs just to take a guess.  I usually do well into Europe and the entire US using it in a vertical configuration.  One year I went to Jekyll Island and stayed overnight and worked a VK station any a ton of European stations using the horizontal dipole configuration, I made a lot of contacts to various parts of the world that time.  Nowadays I use just the vertical configuration for my portable work.  This is the only part of your questions I feel comfortable telling you about cause my situation is different.  I'd say whatever portable antenna you get, practice assembling and disassembling it as many times as possible to get comfortable with the antenna.
Randy
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W6GX
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« Reply #2 on: December 25, 2012, 05:33:42 PM »

Steppir has a new portable antenna called the 'CrankIR'.  There are several versions available.  One version could do 6-80m.  GL on your trip and I do hope to work you.

73,
Jonathan W6GX
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K3STX
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« Reply #3 on: December 25, 2012, 06:57:27 PM »

Ask N7OU what he does.

paul
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AG1LE
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« Reply #4 on: December 25, 2012, 07:30:06 PM »

Ask N7OU what he does.


Paul

Thanks for this  tip - there is a great interview in http://www.dxcoffee.com/eng/2012/04/16/pacific-ocean-n7ous-ham-radio-home/.
Looks like he is using Butternut HF9V and DK9SQ 10 meter fiberglass poles for monoband verticals and vertical Moxons. 
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N2NL
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« Reply #5 on: December 26, 2012, 01:32:32 AM »

You'll do well with vertically polarized antennas very close to, or over salt water.  Even if set back 20 or 30 ft - you will lose a very large percentage of the salt water enhancement. It really needs to be at the water's edge if at all possible.  I spent 5 years on the edge of salt water in Key West and verticals mounted on the dock over salt water (with one elevated radial per band) greatly outperformed the same vertical set back 30ft from the water's edge.

100w and a multi band vertical and you'll have lots of fun.  Do a Google search for K2KW and read about his elevated radials - I prefer them to radials in the water.  They worked much better for me elevated.  AA7JV on the other hand (PT0S) prefers radials in the salt water but uses remote tuners to adjust for tidal changes (which will change antenna resonance).

http://www.n2nl.net/?page_id=40  describes the dock mounted antennas I used while in Key West.
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AG1LE
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« Reply #6 on: December 26, 2012, 09:45:41 AM »

Steppir has a new portable antenna called the 'CrankIR'.  There are several versions available.  One version could do 6-80m.  GL on your trip and I do hope to work you.

73,
Jonathan W6GX
Hi Jonathan
Thanks for the tip.  I found a link with pictures of CrankIR  but no availability information other than Spring 2013. It looks like a very portable antenna but there isn't much information on radials etc. that might be needed. Having a simple manual crank mechanism to change HF bands looks attractive, though.

73
Mauri AG1LE
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AG1LE
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« Reply #7 on: December 26, 2012, 09:51:30 AM »

... I use the Buddipole which serves me well and is very lightweight and small when collapsed plus customer service has been great.  ...  I have the 16' mast and a large carrying bag supplied by Buddipole.  You're suppose to be able to fit everything in the bag but I put the coils, guying kit, cable and small stuff in a small supplemental carrying bag.  I'd say the length is about 4 1/2' and the bag weighs less than 25 lbs just to take a guess. 

Hi Randy

I did have a look at different Buddipole kits and it looks like they would be very viable antenna alternative. How long does it take to change the bands  with Buddipole?   If I understood correctly you need just to adjust the coils and length of the elements to switch bands, is that correct?   

Is there any configuration where you can work on multiple HF bands without adjustments?

Do you need to use guy wires with your 16' mast  or how do you ensure it stays up?


73
Mauri AG1LE
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AG1LE
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« Reply #8 on: December 26, 2012, 10:36:41 AM »

You'll do well with vertically polarized antennas very close to, or over salt water.  Even if set back 20 or 30 ft - you will lose a very large percentage of the salt water enhancement. It really needs to be at the water's edge if at all possible.  I spent 5 years on the edge of salt water in Key West and verticals mounted on the dock over salt water (with one elevated radial per band) greatly outperformed the same vertical set back 30ft from the water's edge.

100w and a multi band vertical and you'll have lots of fun.  Do a Google search for K2KW and read about his elevated radials - I prefer them to radials in the water.  They worked much better for me elevated.  AA7JV on the other hand (PT0S) prefers radials in the salt water but uses remote tuners to adjust for tidal changes (which will change antenna resonance).

http://www.n2nl.net/?page_id=40  describes the dock mounted antennas I used while in Key West.

Hi Dave

Thanks so much for your advice.  You had a very nice setup in Key West. 
Since I will be only on the island for 13 days I need something a bit more simple that I can assemble / disassemble quickly myself.
Also,  I am not sure if the hotel allows elevated radials on the beach - they did confirm via email that vertical ham antenna would be ok.

Thanks also for the K2KW tips - I found this page http://www.k2kw.com/verticals/learning.html that had a lot of practical information about effects of salt water on conductivity of guy wires, insulation etc.

However  if the radials are under water  it sounds like  remote tuner would be needed to adjust for impedance variation.  Both  Flex3000 and Elecraft KX3  have built-in antenna tuners  - not sure if they would be able to handle the impedance changes?  Signal loss in coax is another factor to consider. 

Based on information I got from the hotel  the beach is  about 70 feet from the building.  Since I am quite  limited with luggage weight I need to consider also the weight of coaxial cable and possible remote tuner.  Weight of 100ft RG-8  vs.  RG-58 is  13.7 lbs vs.  2.6 lbs  so better coax would add significant weight (but also reduce losses). 

73
Mauri  AG1LE
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KY6R
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« Reply #9 on: December 26, 2012, 11:12:53 AM »

Short hatted vertical dipoles are fantastic near the ocean. No radials needed . . .

Less noise due to the capacitance hats and the way they reject high angle noise, and the pattern has some slight compression keeping the angle low. They are also very efficient as compared to radial based systems, and take up less room.

The Force-12 Sigma series is a prime example. I can vouch personally for the Sigma 40, 40XK and Sigma-5.
« Last Edit: December 26, 2012, 11:15:46 AM by KY6R » Logged
N2NL
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« Reply #10 on: December 26, 2012, 12:32:00 PM »

A vertical or sloping dipole would work well for you also, and eliminate the need for radials.

You can consider RG8X - very light weight and less loss than RG58.  Cheap too.

My personal experience with ground mounted radials in salt water was not great, but it would probably work fine for you if you can lay them in the wet-but-not-submerged zone of the beach.  Don't forget the skin depth of RF - in salt water it is only a few inches.  So, if you throw a long radial into deep salt water, only the wire within a couple inches of the surface sees RF.  The rest is wasted wire.  So, in a sense, you would be loading a vertical with very, very short radials - not ideal at all!
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ZL1BBW
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« Reply #11 on: December 27, 2012, 12:07:32 AM »

Having been to Raro a couple of times, I would personally put radio at the bottom of the list.  There is the superb swimming and the beach and the sun and the sand then some eating and some drinking then guess what its the beach again.

Check with your motel about overhead power lines, they are everywhere.  Some places have very beach front apartments that could be a good choice with a couple of nearby palms a throw over the tree dipole could be good.  Vertical on the beach, its all a Lagoon, so might be able to walk out a low tide plant a pole in the sand/coral then run the coax back to the unit.

Make sure you have good headphones, apartment neighbours may take exception to ham noise.

Lovely place, enjoy your stay.
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ex MN Radio Officer, Portishead Radio GKA, BT Radio Amateur Morse Tester.  Licensed as G3YCP ZL1DAB, now taken over my father (sk) call as ZL1BBW.
K9NW
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« Reply #12 on: December 27, 2012, 09:04:11 PM »

Others have given you some good ideas.  Should you still find yourself in a weight sensitive situation you could also try what I did in VP2V a few years ago.

http://picasaweb.google.com/fininine/VP2VK9NW2008#

This started out as a 20m dipole but I only had one convenient support to work with.  After trying various stuff I finally settled on just getting one end into the palm tree, sloping it down to the feedpoint, with the other half of the dipole stretched out and buried under the sand.  As you can see this was very close to the water, with a clear shot over the salt water from W thru NE.  I let the tuner in the radio deal with matching issues.  It worked best on 17m and 20m, sort of ok on 30m.  (10/12/15 weren't really in play then so didn't bother much with 'em)

By no means was this a perfect or an ideal setup, yet, it was very simple and it got me on the air.  Over the course of the eight day work trip, mostly working an hour or so in the morning and an hour or so in the evening, about 3100 QSOs went into the log, including 370 JA QSOs - about the toughest path you'll get from the Caribbean.
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AG1LE
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« Reply #13 on: March 26, 2013, 09:07:56 PM »

My Cook Islands DX-pedition departure date is approaching quickly.   
Once again thanks everybody for your antenna advice. 

I did some VOACAP predictions that are in here:
http://ag1le.blogspot.com/2013/03/dx-pedition-to-rarotonga-cook-islands.html

I hope to make some contacts while in Rarotonga.

73
Mauri AG1LE
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W4VKU
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« Reply #14 on: March 27, 2013, 05:34:17 AM »

You might be able to take a sports equipment bag - viz a golf bag or a ski bag.
Most airlines allow 40lbs of this sports bag and is a part of your allowance.
You can easily fit in a HF9V(4ft long pieces) or HF9V-X(3ft long pieces), the coax - RG8X
in that bag. If you can pack real well, the verticals coils can go into the same bag, but
it will need to be double boxed and packed well to take the rigours of handling by the airlines.

The radio + small SMPS should go in your carry on along with the jumper cable and the
digital interface.

You might have to pay for the extra checkin bag if they will allow one.

Good luck
73s
krish
w4vku
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