NVIS, Near Vertical Incidence Skywave

[W5LZ]

Nursecosmo,
This isn't a criticism, just curiosity. Why would you want a NVIS antenna on a mobile?
- 'Doc

 

[Nursecosmo]

Nursecosmo,
This isn't a criticism, just curiosity. Why would you want a NVIS antenna on a mobile?
- 'Doc

As part of an emergency com group, we use VHF for A and B entry teams into disaster zones. The B teams are used as VHF simplex or mobile repeater relays back to the "C" HQ location. VHF is used for the entry teams because vertical HF antennas often have a pretty extensive skip zone. Skip zone - Wikipedia, the free encyclopedia If HF NVIS were to be used by the A team, then there would be no need for the relay teams. The C location will never be more than 200Km out, so NVIS would be an attractive option in many situations.

Plus one of those tied down whips would look really cool on my jeep.

 

[W5LZ]

Nursecosmo,
Okay, I think I see where you are going with that NVIS thingy. Have you considered that by correctly picking the HF band you can pretty well do away with any "skip zone" problems? It's a quite common way of doing things.
- 'Doc

 

[Nursecosmo]

Nursecosmo,
Okay, I think I see where you are going with that NVIS thingy. Have you considered that by correctly picking the HF band you can pretty well do away with any "skip zone" problems? It's a quite common way of doing things.
- 'Doc

Positive reliability is what we are after. If it were as easy to make contact between 50Km and 300Km as you claim, simply by using the appropriate frequency, the military would not have to use NVIS for Battle field over-the-horizon communication. Remember that, that mobile rig only has a 3 meter high antenna at most, so OTH communication is much more difficult with a vertical antenna. Not to mention the difficulties of communicating from one valley to the next in mountainous, or even hilly areas. As you mentioned above, proper frequency selection is still required, but is much more effective for regional communication, when a high take-off angle is used.

I'm know that reliable communication is possible with verticals in most situations with a little fiddling, but I want good communication in all situations with as little tweaking as possible. Thanks for the suggestions.

 

[hookedon6]

As part of an emergency com group, we use VHF for A and B entry teams into disaster zones. The B teams are used as VHF simplex or mobile repeater relays back to the "C" HQ location. VHF is used for the entry teams because vertical HF antennas often have a pretty extensive skip zone. Skip zone - Wikipedia, the free encyclopedia If HF NVIS were to be used by the A team, then there would be no need for the relay teams. The C location will never be more than 200Km out, so NVIS would be an attractive option in many situations.

Plus one of those tied down whips would look really cool on my jeep.

here ya go: a mobile NVIS antenner Loop Antenna - Mobile / Transportable NVIS Series

 

[Nursecosmo]

Thanked Hooked. That is a pretty cool antenna. I wonder where I can find plans for a home brew. SMC doesn't even list the price which is a good indication that I wouldn't be able to afford it.

 

[Moleculo]

the other cool thing about NVIS while mobile is that if you're really doing NVIS, it's darn near impossible to DF the transmitting station. That's the other reason that the military uses it.

 

[Moleculo]

This site has a really good, thorough article on NVIS propagation and antennas:

NVIS Amateur Radio Antennas

 

[Nursecosmo]

Thanks Mole. I read that article a while back but it doesn't have much info on mobile operation.