2m NVIS Plans

[Osprey1163]

I'm trying to find specs for a 2 meter NVIS antenna that I can build myself. I've looked around online and in my own library for plans but all I get is plans for HF. I asked around at the last club meeting & a couple guys have seen plans but can't remember where.
Does anyone know where I might find them?

 

[prcguy]

NVIS is a propagation mode that usually fades out and it not useable above 10MHz most of the time. There will be no NVIS propagation on 2m, that's why there are no 2m NVIS antenna plans. BTW, most any low horizontal HF antenna is an NVIS antenna and in my opinion about 30-35ft high is ideal to cover the bands from 160 to 40m being about 1/4 wavelength above ground on the highest NVIS band of 40m. Using it lower will reduce noise, distant lightning static and DX signals but at the expense of reducing efficiency.

 

[Lauri-CoyoteFrostbite]

Hi Osprey

I am curious why you are interested in a NVIS antenna for 2 metre's- that's quite unusual.
Vertical radiation like that is going to penetrate everything and be lost into the ether-sphere, unlike what happens at HF frequencies--- though if you really want to achieve this, simply point a 2 metre beam straight up--- you'll become like a miniature HAARP** station !!


Lauri



.

** About HAARP | HAARP

.

 

[RFI-EMI-GUY]

A friend of mine who worked for Northrup Death Systems Division designing laser sighting systems for weapons, once worked on a prototype communications device that utilized a UV laser directed skyward to bounce signals off of clouds and moisture in the atmosphere. A sort of lightwave NVIS. The purpose was to provide low probability of intercept communications.

 

[Osprey1163]

NVIS is a propagation mode that usually fades out and it not useable above 10MHz most of the time. There will be no NVIS propagation on 2m, that's why there are no 2m NVIS antenna plans. BTW, most any low horizontal HF antenna is an NVIS antenna and in my opinion about 30-35ft high is ideal to cover the bands from 160 to 40m being about 1/4 wavelength above ground on the highest NVIS band of 40m. Using it lower will reduce noise, distant lightning static and DX signals but at the expense of reducing efficiency.

Well, that certainly makes sense once you explained. Thanks.
I was looking for a wire antenna project and wondered why I'd never seen plans. I thought maybe it didn't work well so nobody bothered. Technically, I guess it really is something that doesn't work well.
Chris

 

[Osprey1163]

Hi Osprey

I am curious why you are interested in a NVIS antenna for 2 metre's- that's quite unusual.
Vertical radiation like that is going to penetrate everything and be lost into the ether-sphere, unlike what happens at HF frequencies--- though if you really want to achieve this, simply point a 2 metre beam straight up--- you'll become like a miniature HAARP** station !!


Lauri

View attachment 130759

.

** About HAARP | HAARP

.

I was looking for a wire antenna project of some kind and wondered why I couldn't find plans anywhere. Once again, thwarted by physics!! LOL

I moved to the Grand Valley in Colorado about 2 1/2 years ago. I was curious to see, since an NVIS radiates straight up, if an antenna would be able to bounce a signal up & back to earth to make contacts above the valley rim, which is something 600 or 800 feet high. There are repeaters up there that I can hit with no problem, I just wanted to try something different.

Point the 2 meter up and *poof* a personal HAARP station you say??? Good The weather would be mine to control!!! Stewie Griffith would be SO proud!

Chris

 

[Lauri-CoyoteFrostbite]

I hope you caught the tongue-in-cheek reference to HAARP Chris--- (I once was involved with that project years ago.)
Along that line however, if you are looking for an unusual twist to two metre's you might try directed signals off the ridges of your nearby buttes--- aka knife edge refractions.

If I have your geography correct, you are out in the Colorado western slope country where you might try some experiments. I live considerably to the east of you- where I am surrounded by 13-14,000 foot peaks (Arkansas-San Luis Valley confluence.) Here I can use highly directional antennas and 'knife edge' VHF signals across the Sangre de Christo mountains to the eastern plains.
When the gods are smiling, on sideband, this will reach +200 miles. By turning the beams towards the other mountain ranges I can bounce signals off them as 'passive repeaters.'
You might give the 'refraction and/or passive repeater' experiments a thought. It could give quite a twist to your hamming; certainly more promising than 2 metre NVIS .

Lauri




.

 

[MUTNAV]

I hope you caught the tongue-in-cheek reference to HAARP Chris--- (I once was involved with that project years ago.)
Along that line however, if you are looking for an unusual twist to two metre's you might try directed signals off the ridges of your nearby buttes--- aka knife edge refractions.

If I have your geography correct, you are out in the Colorado western slope country where you might try some experiments. I live considerably to the east of you- where I am surrounded by 13-14,000 foot peaks (Arkansas-San Luis Valley confluence.) Here I can use highly directional antennas and 'knife edge' VHF signals across the Sangre de Christo mountains to the eastern plains.
When the gods are smiling, on sideband, this will reach +200 miles. By turning the beams towards the other mountain ranges I can bounce signals off them as 'passive repeaters.'
You might give the 'refraction and/or passive repeater' experiments a thought. It could give quite a twist to your hamming; certainly more promising than 2 metre NVIS .

Lauri

View attachment 130777


.

Like Troposcatter

Thanks
Joel

 

[ladn]

I've used a similar technique in California's Eastern Sierra. The repeaters I want to hit are on Mazourka Peak and Silver Peak---both about 30 and 60 miles (respectively) north and >1000 feet higher than my location in an 8400' "hole" in the Inyo Mountains at the east side of Owens Valley. I've had generally good results with a simple (homemade) 2-element beam aimed west to the Sierras which are about 10 miles across Owens Lake.

Depending on atmospherics (and sometimes equipment issues at the repeater sites) I had a near full-quieting signal to Mazourka and a readable signal to Silver using about 25W output to the antenna.

If you want to homebrew VHF antennas, give simple beams a try. A Nano VNA, antenna analyzer or Nano SA are affordable and take a lot of the guesswork out of antenna building.

 

[Osprey1163]

I hope you caught the tongue-in-cheek reference to HAARP Chris--- (I once was involved with that project years ago.)
Along that line however, if you are looking for an unusual twist to two metre's you might try directed signals off the ridges of your nearby buttes--- aka knife edge refractions.

If I have your geography correct, you are out in the Colorado western slope country where you might try some experiments. I live considerably to the east of you- where I am surrounded by 13-14,000 foot peaks (Arkansas-San Luis Valley confluence.) Here I can use highly directional antennas and 'knife edge' VHF signals across the Sangre de Christo mountains to the eastern plains.
When the gods are smiling, on sideband, this will reach +200 miles. By turning the beams towards the other mountain ranges I can bounce signals off them as 'passive repeaters.'
You might give the 'refraction and/or passive repeater' experiments a thought. It could give quite a twist to your hamming; certainly more promising than 2 metre NVIS .

Lauri

View attachment 130777


.

I got your reference to HAARP. I guess I can expect the Back Helicopters any moment. I remember the conspiracy theories about HAARP. "They" are trying to control the weather, "They" are using it to control peoples behavior, probably a whole lot more I've never heard of. Every time I see a reference to HAARP I think of the movie "Remo Williams: The Adventure Begins". By today's standards its kinda politically incorrect, but a fun movie. The good guys are trying to find out if HARP works, except in the movie HARP is a satellite-killer that's way over budget etc. Pretty sure it's a satire of the actual project.

I'd completely forgotten about knife-edge, thanks! I learned about it when I got my Tech license but it didn't stick. I probably didn't remember because it wouldn't have been very useful in Maryland. I've got a portable Elk Radio 2 meter/440 beam that should work well for that kind of thing. Yes, I can see where it might work out better than a 2 meter NVIS........

I'm in Grand Junction, to be specific. We're about 600 feet down in the bottom of the valley. I lived in relatively flat Maryland before moving here and I'm still trying to get an idea of where my handheld will work. There are (I think) 19 repeaters around here. Some in the valley & there's a nice antenna farm on Black Ridge on the western side of the valley.

Chris

 

[kc5uta]

although NVIS is an "HF thing" wouldn't get much results, the concept of using a vhf signal straight up made me think of a biquad antenna for some reason.... now I'm thinking of building a 1.2 ghz one when I get my new toy (Icom9700) .....thanks!

 

[MUTNAV]

This thread started me to thinking, if its possible to measure wind speed and direction by transmitting radio waves at somewhere around 30 to 300 Mhz vertically, then it should be possible to use those frequencies for communications.

It wouldn't be NVIS, but a form of scattering.

Thanks
Joel

 

[prcguy]

There would be nothing to scatter off of except airplanes. If the radio waves encounter something like a temperature inversion layer at a very slight glancing angle they can reflect or refract a little but going straight up will not affect them at all. You can talk to a satellite 23,000mi straight up or even to the moon with just a few watts, so the signals remain unaffected going through the atmosphere at a right angle except for the square law.

Or if you have enough power like HAARP to actually make changes to the atmosphere.

This thread started me to thinking, if its possible to measure wind speed and direction by transmitting radio waves at somewhere around 30 to 300 Mhz vertically, then it should be possible to use those frequencies for communications.

It wouldn't be NVIS, but a form of scattering.

Thanks
Joel

 

[MUTNAV]

There would be nothing to scatter off of except airplanes. If the radio waves encounter something like a temperature inversion layer at a very slight glancing angle they can reflect or refract a little but going straight up will not affect them at all. You can talk to a satellite 23,000mi straight up or even to the moon with just a few watts, so the signals remain unaffected going through the atmosphere at a right angle except for the square law.

Or if you have enough power like HAARP to actually make changes to the atmosphere.

Atmospheric backscatter is real, its how the wind samplers/profilers work. Although it may be more complicated than what the original poster is thinking.

PSL Wind Profiling Instruments: NOAA Physical Sciences Laboratory

US Department of Commerce, NOAA, Physical Sciences Laboratory

psl.noaa.gov

Thanks
Joel

 

[prcguy]

Yes but they are not pointing not straight up.

Atmospheric backscatter is real, its how the wind samplers/profilers work. Although it may be more complicated than what the original poster is thinking.

PSL Wind Profiling Instruments: NOAA Physical Sciences Laboratory

US Department of Commerce, NOAA, Physical Sciences Laboratory

psl.noaa.gov

Thanks
Joel

 

[MUTNAV]

Yes but they are not pointing not straight up.

The idea still has substantial merit. Of course it would be more like a small research project to get it to work, and data rates would be very slow.

If a large searchlight were pointed straight up, even on an almost completely clear day, it would be visible from the side.

Thanks
Joel

 

[jhooten]

The closest thing you are going to get for a 2M NVIS antenna is a Turnstile with a reflector. An antenna normally used for satellite communications.