Author Topic: HF NVIS antenna systems for regional communication  (Read 17960 times)

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DSB

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HF NVIS antenna systems for regional communication
« on: February 25, 2012, 08:41:07 PM »
For all those that are just beginning in HAM radio. You hear all of us push you to get at least to the general stage of the license. The reason is, from a preppers POV, You want local and regional information and HF radio w/ an NVIS antenna setup is the answer. VHF capabilities using repeaters is your answer if the repeater towers are active. However, if the repeaters are down, your Tx/Rx ability is drastically reduced. We push you to the general license so you can get access to HF and then utilize a NVIS setup for regional commo. Here is a slide show just scratching the surface of true independent commo

http://s3.amazonaws.com/emcommeast2008/NVIS.pdf
« Last Edit: February 25, 2012, 08:50:59 PM by DSB »
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idial1911

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Re: HF NVIS antenna systems for regional communication
« Reply #1 on: February 25, 2012, 11:35:20 PM »
I'd like to do some testing between an NVIS, and a g5rv type antenna strung up in a tree..
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DSB

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Re: HF NVIS antenna systems for regional communication
« Reply #2 on: February 25, 2012, 11:40:41 PM »
I'll tell ya, this morning was the first time I ever picked you up, even tho Hamsexy had to relay and I checked on google earth and we are 700+ miles apart. not bad for your temp. setup and my doublet at 28 ft up.
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idial1911

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Re: HF NVIS antenna systems for regional communication
« Reply #3 on: February 25, 2012, 11:44:46 PM »
I'll tell ya, this morning was the first time I ever picked you up, even tho Hamsexy had to relay and I checked on google earth and we are 700+ miles apart. not bad for your temp. setup and my doublet at 28 ft up.

Yea I don't know if it's the new radio, or just propagation today. I haven't changed my antenna at all. I was hearing all of you today, as well. So I guess it's just propagation.
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BTPost

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Re: HF NVIS antenna systems for regional communication
« Reply #4 on: February 26, 2012, 12:53:41 PM »
I would be interested in knowing where and when you guys chat on HF... just so see if I could reach you from here in bush alaska....
Bruce in alaska AL7AQ

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Re: HF NVIS antenna systems for regional communication
« Reply #5 on: February 26, 2012, 01:21:44 PM »
Id be willing to give that a shot, Be a new contact in AK for sure

Im between antennas right now, hopefully ups brings my new one next week.

AD

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Re: HF NVIS antenna systems for regional communication
« Reply #6 on: February 26, 2012, 01:22:55 PM »
BT

I can hit alaska on 20 most of the time from AZ
The only dumb question is the one that did not get asked!!

PLA

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Re: HF NVIS antenna systems for regional communication
« Reply #7 on: March 01, 2012, 08:05:29 AM »
My issues are the result of living on the south side of the mule mountains, I can work all of south america, but getting out north of me is a problem unless NVIS and the range reduction there.

Still I can hit Phx and farther north easily, I may be restricted to regional comms as least north of me, just a price I pay for living here

AD

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Re: HF NVIS antenna systems for regional communication
« Reply #8 on: March 01, 2012, 08:17:44 AM »
Still I can hit Phx and farther north easily, I may be restricted to regional comms as least north of me, just a price I pay for living here

Thats where i and a few others up north come in in an emergency.  For collecting DX or WAS, you may be SOL
The only dumb question is the one that did not get asked!!

W.Lynn

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Re: HF NVIS antenna systems for regional communication
« Reply #9 on: March 01, 2012, 07:44:02 PM »
Come any kind of harsh times, any comms will be better than none.  But I have to admit, I want some distance too. 

His mom is on the gulf coast, and my folks are in Wyoming.

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Re: HF NVIS antenna systems for regional communication
« Reply #10 on: March 01, 2012, 10:44:34 PM »
My issues are the result of living on the south side of the mule mountains, I can work all of south america, but getting out north of me is a problem unless NVIS and the range reduction there.

Still I can hit Phx and farther north easily, I may be restricted to regional comms as least north of me, just a price I pay for living here
PLA
I am going to set up a 3 masted dipole up at my farm this year, prob this summer. My goal is to hit the 400-1500 mile range, consistently on 40 meters by adjusting the dipole height. These masts will have pulleys on top allowing me to raise and lower the antenna to adjust my RF distribution pattern.
Currently I have a multi band doublet up at 28 ft (fixed) and I am getting 400-500 miles constantly on 40 meters. Idial1911 is about 700 miles from me and so I started looking into filling the "hole" between NVIS (1/4 WL) and DX (1/2 WL) and I guessed 3/8 WL should do the job. I haven't tried it yet, but take a look at the 75 Meter RF graphs on this link. Given the F2 is at 250 miles, the strongest radiation when the Dipole is set at 3/8 WL is an angle that ought to bounce at 750 miles. As I said, I haven't tried it yet, but the science looks plausible and it may help you bounce over those mountains. Of course there is still RF and significant dB, but I'm having fun trying to find some workable solutions. ....1/4 WL for up to 400 miles... 3/8 WL for 400-1500 miles... I very interested in experimenting with varying Dipole heights in terms of range.

http://www.athensarc.org/nvis3.asp
« Last Edit: March 01, 2012, 10:55:35 PM by DSB »
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RazorCityDen

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Re: HF NVIS antenna systems for regional communication
« Reply #11 on: March 04, 2012, 08:41:26 PM »
I'd like to do some testing between an NVIS, and a g5rv type antenna strung up in a tree..

Pretty much apples and oranges isn't it?

Take care, 

 

idial1911

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Re: HF NVIS antenna systems for regional communication
« Reply #12 on: March 04, 2012, 08:50:00 PM »
Pretty much apples and oranges isn't it?

Take care, 

 

Yea.. But would like to understand the differences from an actual "test" to see how much better/worse one is over the over. Just to see..
The more I learn, the less I know.

AD

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Re: HF NVIS antenna systems for regional communication
« Reply #13 on: March 04, 2012, 08:53:59 PM »
Pretty much apples and oranges isn't it?

Take care, 

 

Could be a short tree 8)
The only dumb question is the one that did not get asked!!

RazorCityDen

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Re: HF NVIS antenna systems for regional communication
« Reply #14 on: March 06, 2012, 08:17:16 AM »
Yea.. But would like to understand the differences from an actual "test" to see how much better/worse one is over the over. Just to see..

I've got a homebrew G5RV style antenna ready to go up, it's a 94' fed with 41' of 450 ohm ladder line though a 1:1 balum. It's suppose to be resonate on 40, 20, 17, 12 and 10 meters without a tuner and do the 80 meter band with a tuner since it's suppose to run a SWR of 7.6:1.

Should work good for a semi-permament antenna, but it's too long and bulky for my idea of field operating. That and a big part of my idea of 'field' operating includes NVIS mode and from what I gleam from various sources and my own experience, NVIS works best on 40 and 80 meter bands.

My favorite NVIS attennas are the Radio Wavz end fed, half waves. They are single band, full half wave wire antenna's that require no ground plane, just string them acording to how you want to operate, they go up high or inverted 'V' like a dipole or low sloped for NVIS. Pure field simplicity.

This weekend I was running portable on 40 meter and was experimenting with a semi-NVIS set up on a state park beach on the central CA coast. I stung the antenna from a scraggly tree on the access cliff face down to some drift wood on the beach, that left the antenna oriented east/west. I made multipal contacts north/south from one end of CA to the other, some as close as 50 miles. Probagation east/west not so much, I jumped into a net with the controler in Carson City, NV and he said I was 'cutting out' so an operator about 75 miles from my location relayed.

I suppose a guy coulds set up a G5RV as a low sloper, NVIS style and with a tuner transmit on the 80 meter band and depending on the style of G5RV not need a tuner for the 40 meter band. It just seems like a hard way to get to the same place.

There's another option a buddy and I or scheaming on that is based on the military AS-2259 NVIS field antenna. Here's a link to a homebrew version.

http://home.centurytel.net/w9wis/NVIS1.html

It seems as if this homebrew version can be cut to get 40 and 80 meters without a tuner after some experimenting with wire legnths. Not sure why the original builder went the way he did with the tuning. It's not as portable as a end fed half wave but it's would be useful when there's some form of load bearing gear being used in a semi-permanent set-up. Using PVC conduant poles and simple parts it won't cost too awful much to experiment with. I also want to try it without the pole, hanging the center connector from an overhead line or branch, since the poles are the heavy part.

Anywho just a few random NVIS thoughts.