testing of SWR

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testing of SWR

Postby KF5CSW » Tue Oct 12, 2010 5:57 pm

Hi everyone,

I'm in the process of building my new 20 m wire dipole. I'm going to use the trees in my yard to hang it. I don't have a slingshot or anything, so I'm not sure how high I'm going to be able to get it up there. I'm wondering if I need to obtain a SWR meter to test my SWR before transmitting from my Small Wonder 20m CW QRP rig. Or is as high up as I can throw it good enough?

John
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Postby NT9K » Wed Oct 13, 2010 11:06 am

Hi John, yes you need a SWR meter to prune and tune your dipole. If you don't tune the antenna, you could damage your radio. As for the height of your dipole, there are other ways to get your antenna up in the air without a slingshot. I prefer to use that nylon twine. It's cheap at walmart. I like to use a heavy lead fishing sinker.

It's best to unroll a bunch of the string on the ground, so it won't knot up on you when you throw it. Another way is to use a tennis ball. Cut a slit in the ball and tie a metal nut on one end and slip the nut through the slit in the tennis ball. Still, the big fishing sinker works better, because it will use the weight to fall back down through the tree branches and leaves. If it isn't heavy enough, your liable to get it stuck up in the tree.

In your neck of the woods, there are lots of bow hunters. If you have some really big trees, get someone to shoot your string over top the tallest place. Then you can use it as a hoist and pull your antenna up as high as you want it.

I just checked and there is a SKCC Elmer listed in your state. He isn't that far from you, from what I can tell? I also read your QRZ bio. You mentioned using a 2m repeater, so there must be other hams that can help you with your SWR? Maybe one of them has an antenna analyzer?

Hope some of that is helpful. Good luck with your project!
73, Bill - NT9K
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Postby KF5CSW » Thu Oct 21, 2010 4:42 am

[quote="NT9K"]Hi John, yes you need a SWR meter to prune and tune your dipole. If you don't tune the antenna, you could damage your radio. As for the height of your dipole, there are other ways to get your antenna up in the air without a slingshot. I prefer to use that nylon twine. It's cheap at walmart. I like to use a heavy lead fishing sinker.

It's best to unroll a bunch of the string on the ground, so it won't knot up on you when you throw it. Another way is to use a tennis ball. Cut a slit in the ball and tie a metal nut on one end and slip the nut through the slit in the tennis ball. Still, the big fishing sinker works better, because it will use the weight to fall back down through the tree branches and leaves. If it isn't heavy enough, your liable to get it stuck up in the tree.

In your neck of the woods, there are lots of bow hunters. If you have some really big trees, get someone to shoot your string over top the tallest place. Then you can use it as a hoist and pull your antenna up as high as you want it.

I just checked and there is a SKCC Elmer listed in your state. He isn't that far from you, from what I can tell? I also read your QRZ bio. You mentioned using a 2m repeater, so there must be other hams that can help you with your SWR? Maybe one of them has an antenna analyzer?

Hope some of that is helpful. Good luck with your project![/quote]

Hi Bill,
I discovered today that Wal-mart sells slingshots (Daisy - the BB gun company) in the sporting good section :) What luck! Picked one up for $7
I'm going to try it out in the next few days. Getting closer and closer :)
I think I'm going to ask around in the local radio clubs or repeaters here. The SKCC Elmer here lives in Hot Springs, I see, which is a bit of a drive.
I wonder if there is an relatively easy solution on hooking up the key to my 2 meter transciever in the meantime - maybe thru some type of Rigblaster?
Also picked up a 555 chip today. On my way to building a code practice oscillator.

73,
John Vogel
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Postby KC9KHG » Thu Oct 21, 2010 5:21 am

What ever you do, don't tie the rope to a piece of conduit and throw it like a spear...that doesn't work very well. When the conduit comes down...it WILL leave a mark!! ha ha

What I do is use my fishing pole with a heavy lead weight tied to the line. I do fish often and I can cast fairly well,so that works much better than the conduit!

Good Luck!

Randy,KC9KHG
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Postby NT9K » Thu Oct 21, 2010 10:10 am

Hi John, Randy's idea of the fishing pole does work pretty well. You could get the XYL to hold the fishing pole with the bail open, then use your new sling shot to shoot the weight over top the trees. Fishing line works well as it doesn't have much friction. Still, the weight needs to be heavy enough to allow it to fall back to the ground. I don't know how many times I have gotten my lines stuck up in the trees and had to break them off.

Does your 2m do cw? What kind is it? It's hard to say how to hook it up without knowing more info. A rig blaster is used to hook your radio to your computers sound card. I have one, mine is a rig blaster plus.

If you just have a 2m HT, then no it wouldn't help you. If you were going to send cw on FM, then you would need an oscillator. Good for you, building your own! That is a great project to do when you're first getting started and will come in handy for years to come. Most guys, just buy a store bought one. Right now, I'm using one from kit form. I leave mine in the living room, then when I am sick I can still practice while on the couch or even in bed.

As a new amateur, you are to be applauded for building your own gear. That is an entirely separate part of ham radio and lots of fun too! There is no better feeling than to have made something and see it work and be useful! Anyway, let us know about your 2m radio and we can try and help you better. Good luck with your antenna project too!
73, Bill - NT9K
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Postby k8jd » Sat Apr 30, 2011 12:14 am

I hope you got your SWR meter and got the dipole trimmed.
Having a well adjusted antenna is VERY importaint on a QRP station.
You don't have much power to waste.
I have a newly made 20/30M Fan dipole up in trees , made last fall before the bad WX hit, only got it up about 25 ft on the first try. Now the spring WX finally is here I need to get it fine tuned and hoisted up a LOT higher.
At 25 FT it performs quite poorly.
I chart my antennas on graph paper for SWR vs Frequency and this is a great help in determining if they need to be longer or shorter when adjusting them.
I mark the SWR for frequencies from below, to above and across the band every 50 or 100 kHz and can see where the wire is resonating easily.
When you build your next antenna give this a try.
73 from K8JD, SKCC 1395, Centurion 18, Tribune 12, Band Endorsements; 160, 80, 60, 40, 30M, 20, 17, and 10M

Ham radio is real Radio, CW is real Hamming!
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