Antenna Differences

[I_M_RadioActive]

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Howdy folks. This is my first post. I'm very new to this site and to Radio comms.

My question is this :
It's hard to see it by site ... but what's the major differences between a Sloping-V configuration and a NVIS antenna setup? Obviously I'm talking about HF. They look so similar and the internet is realtively limited in refrence to the NVIS antenna. Thank You for any help on this.

RA

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[SCPD]

NVIS antenna

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Howdy folks. This is my first post. I'm very new to this site and to Radio comms.

My question is this :
It's hard to see it by site ... but what's the major differences between a Sloping-V configuration and a NVIS antenna setup? Obviously I'm talking about HF. They look so similar and the internet is realtively limited in refrence to the NVIS antenna. Thank You for any help on this.

RA

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Well, I had never heard of a NVIS antenna before. So I did a query on the 'net.
If ya got the room, the NVIS would be better. The sloper's going to be directional, the NVIS isn't.

 

[zz0468]

NVIS refers to a propagation mode, not a specific antenna. You can use just about any antenna that has a high radiation angle. A dipole close to the ground would do that.

If you're interested in low frequency operation relatively close in, that might work for you. If you're interested in maximizing your DX capability, you 'd be better off finding something else.

 

[kb2vxa]

A sloping V is good for limited real estate BUT it's radiation pattern is quite unpredictable and gets worse as frequency goes up. Then again Amateur Radio is all about "whatever works" so it may work to your advantage.
NVIS on the other hand is like the man said, a propagation mode, specifically Near Vertical Incidence Scatter. It is useful for daytime regional coverage out to about 1,000mi and to get behind obstructions. For that reason the Army over the last several years developed an HF NVIS battlefield communications system at Fort Monmouth NJ and implimented it last year.

 

[prcguy]

The Germans in WWII had antennas optimized for NVIS and knew exactly what they were doing with them. Specific antennas for NVIS have been the US military for over 50yrs and many systems have been designed around NVIS over the same time. NVIS propagation is available day and night depending on frequency. NVIS stands for Near Vertical Incident Skywave (not scatter) and the typical advertised range is about 300mi although 500mi still may have some NVIS components depending on frequency and propagation. Most people using a dipole, G5RV or similar horizontal antenna at 30ft or less are launching NVIS signals on 160 through 40m and probably don't realize it. Above about 10MHz NVIS propagation is almost non existent. There is a Yahoo group devoted to NVIS communications which is very active and many of us test antennas and optimize the mode nearly every day.
prcguy
QUOTE=kb2vxa;1025329]A sloping V is good for limited real estate BUT it's radiation pattern is quite unpredictable and gets worse as frequency goes up. Then again Amateur Radio is all about "whatever works" so it may work to your advantage.
NVIS on the other hand is like the man said, a propagation mode, specifically Near Vertical Incidence Scatter. It is useful for daytime regional coverage out to about 1,000mi and to get behind obstructions. For that reason the Army over the last several years developed an HF NVIS battlefield communications system at Fort Monmouth NJ and implimented it last year.[/QUOTE]

 

[k9rzz]

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Howdy folks. This is my first post. I'm very new to this site and to Radio comms.

My question is this :
It's hard to see it by site ... but what's the major differences between a Sloping-V configuration and a NVIS antenna setup? Obviously I'm talking about HF. They look so similar and the internet is realtively limited in refrence to the NVIS antenna. Thank You for any help on this.

RA

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Nice article: NVIS Amateur Radio Antennas

Hams will purposely put up "NVIS" or commonly named 'cloud warmers', for either 80 meter nets or for working stations close in during contests. The sloping V will give you a lower angle of radiation and more distance in general. Not that you won't work close in stations with the V, you'll work plenty, it's just the guys running the cloud warmers are looking for that 'extra edge'.