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   Home   Help Search  
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Author Topic: NVIS advise please!  (Read 3340 times)
KC5CQW
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Posts: 98




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« Reply #15 on: January 03, 2010, 02:43:48 PM »

No one has said it so here I go:
I know you don't have a tuner. These things can go very cheap on the used market. They are not hard to build with scraps of wire and sheet metal. I have all kinds of info if you want. Just email me at my callsign at gmail dot com.

Next, if you have the space and it sounds like you do, go for a loop. 560" of wire, ladder line (home made or 450 ohm), a 4:1 balun (home made or built in the tuner), some insulators 1/2" PVC pipe is cheap.

Get this up as high as you can. You will be able to work DX on the upper bands due to the higher takeoff angles and gain lobes the loop has. On the lower bands it should do just fine for getting out of the valley via ground wave and this nvis cloud warmer stuff.

Side note: an "antenna tuner" is really an impedance transformer or antenna coupler. It does NOTHING to tune the antenna. All they do is transform the impedance of the antenna and feed line to 50 ohms so the radio will be happy. Whatever the SWR of the antenna is at the frequency you are on stays the same. The antenna coupler "fools" the radio into thinking that it is transmiting into a resonant antenna.
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VK1OD
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Posts: 1697




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« Reply #16 on: January 03, 2010, 02:48:30 PM »

...
The antenna coupler "fools" the radio into thinking that it is transmiting into a resonant antenna.


Or perhaps more correctly, fools some hams into thinking that they are transmiting into a resonant antenna, as if that was important.

Owen
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KC5CQW
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Posts: 98




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« Reply #17 on: January 03, 2010, 03:02:38 PM »

Brilliant! I was trying to keep the positive reinforcement going.
Yes, they can fool the fools so to speak...
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VK1OD
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Posts: 1697




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« Reply #18 on: January 03, 2010, 03:13:25 PM »

Brilliant! I was trying to keep the positive reinforcement going.


And the explanation was so good up to that point.

BTW, did you mean 560" or perhaps 560' of wire?

Owen
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KC5CQW
Member

Posts: 98




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« Reply #19 on: January 03, 2010, 03:19:07 PM »

I'm not sure if that is an insult or what...

Anyway, yes I meant ' not"
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N7NBB
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Posts: 380


WWW

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« Reply #20 on: January 03, 2010, 03:49:58 PM »

WOW ZAC.. wish you would have an E-Mail address listed here on E-HAM or even on QRZ... would be nice to offer some helps directly, and not waste space here... but in a nutshell to start:

Have you ever tried listening to the MT Traffic Net EVERY evening at 0030 UTC on 3910 or the MT Section Net EVERY Sunday morning on 3880 at 8:00am Mountain Time ? Nothing against you listening to CALIFORNIA.. but if your main desire is LOCAL GALLATIN or JEFFERSON Co.s Why reference CA stations. ?? In the event of any disaster or emergency those freqs. (above) are the check in frequencies anyway, so that's what you would shoot for.  There is a GREAT CLUB in BOZEMAN just about 30 miles away... another club in HELENA - if "personalities" just don't mesh between you and your local club. Either of those would be a great start and wealth of experience and knowledge.
In addition to great contacts around the globe, I used to use a simple dipole cut for 75 meters and it was just 18 feet above ground.... (no NVIS intended.. that was just the only thing I could use (at that time)... It worked great for local (tri-state area) with just 100 watts.  Have you tried a COMPLETE processor reset on your radio? maybe that will clear the problem you are experiencing.. if not, the ABOVE referenced clubs may surely help.
Best of luck... Hope to hear you on the LOCAL nets.
Cam - N7NBB - (Great Falls)
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N0PWZ
Member

Posts: 9




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« Reply #21 on: March 09, 2010, 09:58:23 PM »

Zac,

Don't assume that a lot of the advise here is applicable to your situation. Try stuff out and see what works for you in your situation.

I've run a Windom as my primary antenna on a digital HFLINK station for 2-3 years. It sits ut 20-30 feet, and theoretically it would be a pretty good NVIS antenna.

Here's the problem. It has continental coverage, and has even been heard down in VK land. So how's that possible? Yeah, I'm up here at 7500 MSL, but I don't think that makes a bit of difference either. Theory says it shouldn't work for DX, but its coverage is admirable and consistent.

One of the factors that may be affecting it is that the ground that it is beneath it is quite sandy. There's ground, and then there's ground. The effective electronic height above this sort of ground could far higher than the actual physical distance. The system operates quite nicely on 20 and 40, so it's not doing what many experts would have you believe it capable of doing.

Get out there and hang the antenna up as high as you can, and you may very well be surprised as I was. Antenna performance is not terribly predictable, and the best way to see how well things work, is get your hands dirty and see how things work. :-)
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W8JI
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« Reply #22 on: March 10, 2010, 04:36:16 AM »

Some of the antenna theory being passed along is frightening. I suppose it has always been that way, antennas are always something people get way too opinionated or emotional about.
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