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If you were going to put up one antenna this winter....




 
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Author Topic: If you were going to put up one antenna this winter....  (Read 5058 times)
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WB2EMS
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« Reply #25 on: November 28, 2018, 09:56:26 AM »

Quote
Anything that won't ice up !

Someplace, lost to the mists of time, I remember reading about a station that had an antenna that was a continuous circuit, like a folded dipole or T2FD. They kept it ice free by running power through it when it wasn't in use to keep it warm.  Grin
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« Reply #26 on: November 28, 2018, 12:49:14 PM »



A deckhand with a broom to knock the ice off........

KLC
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« Reply #27 on: November 28, 2018, 04:35:02 PM »

  In the Collins Collectors magazine "Signal" there was a story a few years ago about a system they built for the Navy that was used airborne and was very low frequency. In that article they mentioned that there was a ground station in Maine. The Maine station had two antennas and its own generation, 5 MW if I remember correctly. The antennas were huge wire arrays and in the Winter when icing would be an issue one antenna was on line. The transmitter used 2 MW and the other antenna was reconfigured as a load for the generation system's other 3 MW of capacity. They would switch between antennas as the one being used for transmitting began to ice up.
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« Reply #28 on: November 29, 2018, 10:32:36 AM »

That may have been what I read about, although I don't recall it being such a low frequency system. Those low frequency systems for talking to subs are interesting. Very narrow antenna bandwidth so the CW has to be slow and shaped to control the bandwidth. In the air they fly circles with thousands of feet of wire trailing behind down into a cone shape oriented vertically. I would have loved to have sat in the design sessions for those systems.  Grin
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« Reply #29 on: December 15, 2018, 02:13:25 PM »

Agree! the high big flat top with open wire feed is what serious folks run when they run out of patience. Very good performance - problems are few. And yes that essentially takes all the fun out of it.

So I just put up my first 80/40 Trap Dipole with old school home made traps and coax. Lots of fun understanding what was going on. Tuned em for 6.7 MHz.

I also like big vertically oriented  loops like a full wave on 80M. I have run them terminated with a balun for multiple even bands, and not for single band or open wire feed.

And I have always liked the elevated radial Groundplane idea for wire verticals for DX on 75M.
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« Reply #30 on: December 31, 2018, 02:14:31 AM »

Update,

Closed on the new QTH. W7FG 240' with 100 feedline on order. In the meantime I've hung my ZS6KBW doublet up as a temporary measure. Feeding through a DX engineering 1:1 5KW balun. The KX3 was happy with it from 40 meters up through 6 with it's autotuner. Not so happy on 3885 though. When I get a power supply and a Kenwood TS480HX setup with an AT200 tuner we'll see if it likes the other tuner better. Need to scope a better path for the big antenna when it arrives around the end of the month. I didn't realize they didn't ship from stock but built them for each order with a couple of week lead time. Should have ordered sooner.

Moving in the mud and cold is not so much fun. And it looks like I'll have to track down at least one 60 hz buzzy of some sort on the site.


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« Reply #31 on: December 31, 2018, 04:32:49 PM »

anyone have any experience with pneumatic launchers?   Need advice on launching a line into or over trees such as launch angle.  my homebrewed launcher has not been put to the test yet.  It has a fishing reel with mono filament. My fear is wind knots from any cross wind and a quick unwind from the reel.  Basically want to put a #14 THHN long wire into the woods behind the QTH.
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« Reply #32 on: December 31, 2018, 06:01:19 PM »

anyone have any experience with pneumatic launchers?   Need advice on launching a line into or over trees such as launch angle.  my homebrewed launcher has not been put to the test yet.  It has a fishing reel with mono filament. My fear is wind knots from any cross wind and a quick unwind from the reel.  Basically want to put a #14 THHN long wire into the woods behind the QTH.
Take a look at Jeff K6JCA's blog. He has done a couple of rounds of launchers and has some practical advice:

http://k6jca.blogspot.com/search/label/Antenna%20Launcher
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« Reply #33 on: December 31, 2018, 08:55:30 PM »

  Borrowed this from the Whitman Radio Club while visiting my sister in Wareham in October, uses a sprinkler valve and two 9 volt batteries. The barrel screws onto the valve and is 1 1/4 inch schedule 40 PVC, the projectile is 3/4 inch schedule 40 PVC with end caps and has something in it for weight, sand maybe. The holding tank is 3 inch schedule 40 PVC. I pressured it to 100 PSI.

  It works very well, I have used the sling shot and lead weight launchers which don't work as well. The lead weight doses not have the weight to pull the line over and down from a branch nor does it shoot as high.

  This launcher will shoot quite high and one needs to be careful as the projectile has speed and weight, it would hurt some one. I hit the tree on my first shot and shattered the projectile, second shot not that I had an idea of where it would shoot went right over the tree limb at was at 45 feet. I had trouble pulling the transition from mono filament to nylon cord over the limb, I probably should have use some plastic tape to tapper the transition so it would pull easier.


* Antenna Launcher -1.JPG (126.93 KB, 1024x591 - viewed 114 times.)

* Controls.JPG (76.56 KB, 938x768 - viewed 118 times.)
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« Reply #34 on: January 01, 2019, 02:45:50 AM »

I've used bows and weighted arrows, slingshot with lead sinkers, and I'm about to use a pneumatic launcher. Whatever you use I strongly advise making sure the line is free and won't snag. If it does, the monofilament line you use will absorb the energy by stretching and then return it by zinging the payload right back at the launch point, which with a bow or slingshot is right in front of your face. Ask me how I know this... Shocked
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« Reply #35 on: January 01, 2019, 08:02:32 AM »

Maybe a bit weird but I'd put a 140-500MHz discone on top of the tower this winter, if it were possible.
As usual, LMR-400, ugh -100 FT of it. Yuck 2.7dB loss.  why even do it.
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« Reply #36 on: January 01, 2019, 08:42:57 AM »

I've used bows and weighted arrows, slingshot with lead sinkers, and I'm about to use a pneumatic launcher. Whatever you use I strongly advise making sure the line is free and won't snag. If it does, the monofilament line you use will absorb the energy by stretching and then return it by zinging the payload right back at the launch point, which with a bow or slingshot is right in front of your face. Ask me how I know this... Shocked


I recall reading about a fisherman getting killed by a lead sinker.

https://www.fieldandstream.com/death-by-sinker
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His fear was when I turned it on for the first time life on earth would come to a stand still.
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« Reply #37 on: January 01, 2019, 02:15:52 PM »

Everyone has their own antenna erection schtick - mine is the bow and arrow.  I have used a bow and arrow since Boy Scouts merit badge.  


Some pointers:

If new at archery, then buy a cheap used recurve bow  ($20) and practice on a cardboard box target every day for a week to get good.

Stick a spinning rod handle into the ground with 6 pound test nylon monofilament line. (no more than 8 pound test to maintain accuracy and min drag)  Make sure there is plenty of line on the reel, spooled up near the lip for easy out-flow. If you lose too much line due to breakage, add a full dose because  a knot will cause flow problems.  Tie the monofilament to the arrow's end at the slot. I never had to weight the arrows - if your aim is good. They go right thru effortlessly.  Always launch the arrow from the woods >  into the clearing or back yard. Pick a tree crotch and aim carefully. There will be really bad windy days when it takes 10 tries - but most other days the first try is golden.  I can accurately thread thru 100' high crotches if needed. A minimum 25 pound recurve bow is good.

Feed a heavy string, then light rope thru the crotch and end up with 3/16" stainless aircraft cable. (Guy cable works even better because it's smooth.)  Tape up the rope feeder knots so they are smooth and will pass thru the crotch easily.  Try to support the center of the dipole and there will be little load on the end tree crotches -  and the cable will be less apt to work its way into the tree limb over time.

T
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« Reply #38 on: March 15, 2019, 11:22:50 AM »

So I finally got the spare cycles and weather to put up the W7FG antenna. It's a 240 foot long (160 meter) antenna and I had it come with 100 feet of feedline. Picked the best trees I could around the hacienda and got it running more or less NS (20/200 degrees). The trees were not as tall as I hoped, based on the feedline coming down to the ground it's about 45' up. To get the feedline to the port in the window (MFJ pass through panel with parallel feed standoffs) I ended up cutting it to 50' which was listed in the green on the hamuniverse site mentioned above.

Last night I was able to load it up with the TS480 and the AT200 pro through the 5 kw 1:1 balun and test it on the various bands. It loads up fine on all bands except 30, and 160!  Shocked

Previously I was running a ZS6KBW doublet, 102' fed by 40' of 450 brown stuff, and it loaded fine on 80-10, too short on 160. So I expected this one, twice as long, would run well on 160 and hopefully on most of the upper bands. But it's not happy anywhere on 160. The tuner can grudgingly get it down to about 2.5 to 1. It doesn't seem to matter which end of the band I'm on, I tried every 50 khz up and down.

This weekend I'll put an AIM4170 analyzer on it and see what it looks like, have to get the software on a new laptop first.

Wonder which way to go in trying to get it to work on 160 and still work ok on the other bands. I can probably shorten up the feedline 5-8 feet, I've got it pulled to the side a bit to add some length and get around a corner of the house. It did do a nice job on 60 meters this morning.

Thoughts?

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« Reply #39 on: March 17, 2019, 09:56:51 PM »

So I ran the AIM4170 on the antenna and got the following results. Looks like it's resonant quite a bit below the band around 1.575. OTOH 75 meters looks like it's high in the band, and 40 meters very low again. I'm thinking I need to shorten the antenna some.


* w7fg with 50 feet.jpg (294.79 KB, 1706x745 - viewed 61 times.)
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73 de Kevin, WB2EMS
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« Reply #40 on: March 23, 2019, 06:14:47 PM »

Talked with Brian the fellow who runs the antenna business now and he said shorten it by 10 feet by folding back the wire. Did that. It moved it about 150 khz. Did it again, now it's about 1775 khz. Arrrgh. Now I'm reading that folding back the wire (zip tied and taped at the ends) may not 'shorten' it as much as just cutting it off. I think this thing is going to be up and down 10 times before I get it to tune. I'll be on 160 just in time for thunderstorm season. :-)

Any thoughts on the fold vs cut tuning?

Thanks
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