[MRCA] MRCA Meet Communications Readiness Bulletin II

[Radio Station KW1I]

Rob,

I agree that the dipole we use is probably a good vertical radiator, but we 
could actually have a better one to compare against.   From the reading I 
have done the experts say the NVIS antenna should be .15 to .2 wavelengths 
high.  Other sources say .05 wavelength to enjoy some gain reduction but 
overall s/n improvement.  The antenna I put up is approx. .25 wavelength 
high, but I would like to have second antenna, a lower NVIS dipole at the 
Gilbert base with maybe three parallel interconnected counterpoise wires 
under the antenna.   That way we could switch from the higher dipole to the 
lower with counterpoise and see if there was any difference.  The only 
problem lies in having two tuners matched to the GRC-19 such that the power 
level from the transmitter is the same into both antennas.

I may have some suitable wire around here for a counterpoise for at least 
one of the NVIS antennas.

Dale


The   ----- Original Message ----- 
From: "Rob Flory" <robandpj at earthlink.net>
To: "Military Radio Collectors Association" <mrca at mailman.qth.net>
Sent: Friday, August 31, 2007 10:44 AM
Subject: Re: [MRCA] MRCA Meet Communications Readiness Bulletin II


> The dipole that we always set up at base is a perfectly good NVIS antenna.
>
> RF
>
> -----Original Message-----
>>From: Radio Station KW1I <kw1i at earthlink.net>
>>Sent: Aug 31, 2007 10:20 AM
>>To: Military Radio Collectors Association <mrca at mailman.qth.net>
>>Subject: [MRCA] MRCA Meet Communications Readiness Bulletin II
>>
>>MRCA Meet Communications Readiness Bulletin II
>>
>>On the Friday afternoon (Sept. 21) group field exercise to Big Pocono 
>>there
>>will be an opportunity to test Near Vertical Incidence Skywave propogation
>>over the 19 mile path between the field site and base at the Gilbert
>>Fairgrounds.  The access road to the top of the overlook point is on the 
>>far
>>side of the mountain.  Setting up a NVIS antenna equipped station near the
>>bottom of the access road would present a significant communications
>>challenge back to base with the bulk of the mountain shadowing normal
>>antenna take off angles.
>>
>>I propose that one team on the way up the mountain separate from the 
>>convoy
>>and set up a short way up the mountain's access road.  The team should be
>>equipped with VHF set for coordination through stations on top of Big 
>>Pocono
>>back to Gilbert. This team will be in place when the main communications
>>convoy reaches the top, sets up and commences tests.  Upon completion of
>>NVIS testing the station at the bottom of Big Pocono can pack up and join
>>the main body on the mountain top.
>>
>>This experiment will require two NVIS antenna set ups.  One remote and one
>>at the Gilbert base.  The simplest and probably the most effective 75m 
>>NVIS
>>antenna is a low dipole 15-20 ft off the ground, with typical sag in the
>>middle and with at least one counterpoise wire running under the antenna
>>attached to the HF rig ground.   Two end support masts should be planned,
>>though it is likely a tree can be used for support at one end.
>>
>>VOLUNTEERS NEEDED:
>>
>>1.  A 2-3 person comm team to set up and man the remote Big Pocono NVIS 
>>test
>>station.
>>
>>2.  One of more Individuals who can provide NVIS antenna kits, one for the
>>base at Gilbert, one to be erected at the Big Pocono remote NVIS 
>>experiment
>>site.
>>
>>Commenters and volunteers send mail to kw1i at earthlink.net.
>>
>>Complete MRCA Meet information at http://www.mrca.ar88.net/
>>
>>
>>
>>
>>
>>
>>_______________________________________________
>>MRCA mailing list
>>MRCA at mailman.qth.net
>>http://mailman.qth.net/mailman/listinfo/mrca
>
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