logwire question

[David, K3TUE]

Because of my location issues I am going to have to resort to a longwire for my antenna.  I will have a couple of counterpoises too.  Think of it like a vertical radiator on its side (lying horizontal, about 100 - 200 feet long) with 2 radials at 90 degrees to the radiator (90 degrees from each other, and each sloping 45 degrees toward the ground, each about 10 - 20 feet long).  Yes, I know, it does not sound very efficient.

The horizontal radiator will have to pass by a tree outside my window and perhaps another on the way.  It may end up lying on one or more trees.

QUESTIONS:
1) will the RF damage/burn the tree?
  1.1) is there a power i should stay below to avoid damaging/killing the tree?
  1.2) will i have to insulate it from the tree?
  1.3) should i do my best to avoid touching the tree with the radiator?

[Ed/KB1HYS]

just use insulated wire for the entire installation. 

I've used #14 awg wire strung up in two pine trees. Lots of contact on the tree branches, needles, etc. Never a problem.   Get 500ft on a spool at the local home depot.  Personally I think stranded is better than solid. Solid has broken on me several times.

This should be ok for any of the 100w class rigs.

[WA1GFZ]

I ran the same antenna when I was a kid. My bedroom was on the second floor and had an l network in my closet. It worked great except for the RF burns. ran a pair of 811s in a linear.  Later i moved to the basement and put up a rhombic. A balanced antenna was easier on the lips. Don't close talk the mike.

[KB2WIG]

You never used a Tupperware gravy shaker as a windsock???    klc

[Jim, W5JO]

Also magnetic fields make the trees grow better.

[The Slab Bacon]

Dave,
         Try to keep the wire off of (insulated from) the tree as best as possaroo. Be sure to have a good ground / ground system. Also use a tuner capable of feeding a voltage fed antenna and let it rip! Any antenna is better than none!! As Frank said watch the lips to the mic, sometimes end feds are tough to tame the stray rf, but you should be able to work with a 100w class ba and have some fun. I need to hear you on the air!!
                                                     The Slab Bacon.

P.S. since you were last over here I have added 4 more interesting receivers to the collection for you to "road test'

[The Slab Bacon]

I ran the same antenna when I was a kid. My bedroom was on the second floor and had an l network in my closet. It worked great except for the RF burns. ran a pair of 811s in a linear.  Later i moved to the basement and put up a rhombic. A balanced antenna was easier on the lips. Don't close talk the mike.

I think we all had some form of end fed at one time. I can still hear Timtron telling me :
"I can hear ya, Frank, but yer kinda piss-weak" Anything is still much better than nothing at all!  And if ya get a little burn on the lips, just rub a little pickled eggplant on it

                                                The Slab Bacon

[K1JJ]

Hi Dave,

If you worry about tree arcing, be aware of where the high voltage points are on an end fed wire. These are the points that are more apt to burn through the wire's insulation to the tree branches.

The voltage starts at its highest point at the opposite END from the rig, no matter what frequency you are on. It then will dip to a low point 1/4 wave down the wire and then back to a peak 1/2 wave down the wire.

So, for example, on 75M, look to have high voltage at the opposite end, medium voltage 32' away from that end, low voltage 64' away, medium voltage 96' away and again high voltage at 128' away. 


For finding a good match for your tuner, here are some tips:

For 75M, if you feed it at the end of a 128' span + 64' wire lead-in, it will be a low impedance, low voltage point. Add another 64' to the overall length to feed it at a high impedance, high voltage point. Add 32' to a 128' span for a medium impedance point to feed.

Use these same wavelength principles for any length or band in case you have arcing problems or difficulty finding a good tuner setting.  ie, If you are arcing a particular branch (except for the very end) just add some feeder length to move that HV point somewhere else.

Good luck and 73,

T

[David, K3TUE]

As Frank said [...] sometimes end feds are tough to tame the stray rf

I was goning to try to keep this at bay by running a short length of coax to the window and running the radiator from the end of it outside.  I figure that a 4 - 6 ft run of good LMR-400 Ultra coax will not cause me to loose too much signal, but would help keep some of the stray RF in the pipe 'til it gets outside.

I need to hear you on the air!!

I'm inchin' along.  I hope to get there soon.

since you were last over here I have added 4 more interesting receivers to the collection for you to "road test'

Perhaps one of these Friday nights if I can steal away from the XYL for an evening I'll drive up and see what you have done lately.  I still have the D-104 I promised you.  I'll call first.

[David, K3TUE]

The voltage starts at its highest point at the opposite END from the rig, no matter what frequency you are on. It then will dip to a low point 1/4 wave down the wire and then back to a peak 1/2 wave down the wire.

Thanks for the reminder.  I think between this kind of planning, and perhaps strapping a ceramic coil form to the tree for it to run through I should be able to avoid the arcing I was concerned about.

[WA1GFZ]

Just run enough power to fry the leaves slowly. One night I had a fire ball in the oak behind the house. It was Nov. and those oak leaves hang on till spring. The trick is to operate a lot so they never get a chance to grow back in the way. Slowly qro and things get cleared and stay cleared.