[MRCA] Field Exercises

[ersmar at comcast.net]

Rob et al:

     FWIW - Here's a URL for a Telex NVIS antenna (AS-2259/GR) that's apparently available for military use from 2-30 MHz: http://www.telex.com/Wireless/products.nsf/pages/1990!OpenDocument&c=files .  Click on 1990 Product Brochure and you'll get detailed specs; other places on the web page will give you more info.

     From what I can see this is nothing more than a low (15 feet AGL) crossed dipole array for 80M and 40M.  The mil rig's (e.g. PRC-47) internal tuner is able to match either one of the dipoles sets over the entire HF range.  

     The key is this should be easy for us hams to duplicate for field use.  Replace the fancy coaxial support conduit with a simple PVC or aluminum system and run real RG-8 or -8X up to the feedpoint.  Keep the far ends of the wires off the ground and you should end up with a pretty useful NVIS antenna.

     Also check out http://www.pacificsites.com/~brooke/AS2259.shtml at the bottom for other sources of NVIS info.  The most interesting (to me) sites are those showing NVIS antennas on vehicles, especially those used by the Wehrmacht during WWII.  The loops of tubing set atop their armored vehicles sort of remind me of a loop of PVC containing #12 wire atop my YF's minivan.  Hmmmmm......  Don't tell her.

73 de
Gene Smar  AD3F



> Hi,
> Adding VHF FM sounds great.  I would like to hear that, having none of the
> gear myself.
> 
> As for NVIS on the HF exercise, I think that using period-correct antennas
> should be encouraged, and we will learn something.  Maybe one station on
> the mountain can run Vietnam-era gear and NVIS antenna, and the other(I am
> nominating myself) can run WWII vertical style.  Hopefully we will have a
> mix of eras back at the fairgrounds and can see how the different
> configurations work out.  I think that in the absence of geological
> obstacles NVIS offers little if any advantage at that kind of distance, but
> I also thought it was improbable to hear a BC-611 at 15 miles under even
> the best circumstances.  2 years ago, we had a mix of antennas, with the
> home base running a dipole, which works well for contacting the outside
> world via ionospheric modes, and most if not all of the portables running
> verticals.  
> 
> It might be fun to have an amplified speaker to connect to the rigs at the
> Fairground so visitors and our group members who aren't wearing the cans
> can hear them.
> 
> If anyone else has infrared signalling gear, I am QRV.
> 
> Rob Flory
> 
> 
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