[MRCA] M&S Net antennas

[Gene Smar]

Ray:

I also recommend using a low (<1/4 WL) dipole for NVIS work on 5.3 MHz. To seal the ends of the coax (assuming you don' t use a PL-259/SO-239 combination to terminate the coax), you can follow this process:http://lists.contesting.com/archives//html/Towertalk/2002-10/msg00391.html . One change I would make is to use solid wire for the shield connection to avoid any possibly wicking with stranded wire. 


73 de
Gene Smar AD3F


On 01/29/13, Steve Gajkowski<grasshopper at epix.net> wrote:



Start with a low dipole, easiest to make and then work from there. Also, not sacrificing any power in a tuner.



Not uncommon to get water penetration into coax, or wire for that matter. Very common to have corroded wire inside the insulation on boats where the wire is exposed to water. 

Coax seal or duct seal is a good solution to the problem.. Tape or heat shrink doesn’t keep the water out.




From: mrca-bounces at mailman.qth.net [mailto:mrca-bounces at mailman.qth.net] On Behalf Of Alex J Rokowetz
Sent: Tuesday, January 29, 2013 10:31 AM
To: Ray Fantini
Cc: Military Radio Collector's Association
Subject: Re: [MRCA] M&S Net antennas




Ray,

As the other M&S net participants can tell you, I used the AT1011 vertical with a tuner and a 100W output many many times and was heard by most stations with a good signal. When using a 20W radio and a tuned AT1011 vertical... different story. Very hard to get into the net with that setup. However when using a 20W radio and a resonant dipole (no tuner), everyone usually copied me very well. Also, a horizontal dipole antenna usually provides me with a much lower noise level than a vertical.



Alex
K2AJR


From: Ray Fantini <RAFANTINI at salisbury.edu>
To: "Military Radio Collectors Association (mrca at mailman.qth.net)" <mrca at mailman.qth.net> 
Sent: Tuesday, January 29, 2013 10:22 AM
Subject: [MRCA] M&S Net antennas




Wanted to get something up and working for the M&S Net, got lots of radios so that’s not an issue but the problem appears to be antennas. Over the last couple weeks I have discovered a couple things. First, of all the low frequency antennas I have installed at the QTH the only good antenna I have right now is a half wave inverted V cut for 160. My other two dipoles cut for 40 and 20 meters both have coax full of water. Who would have thought that if you have the ends open where they connect to the center sections that water would get in and eventually come out the end of the cable in the shack, I was surprised! Second, nothing I have appears to resonate at 5.3 Mc and antenna tuners are harder to just throw together than first thought. Third, I know nothing about antennas and propagation. can tell you all about VHF and microwave path analysis but this HF stuff is all voodoo, when everyone starts all the arguments about NVIS and the like my eyes just glaze over. So with all this in mind this last weekend I strung up a vertical wire insulated one foot out from the top of the tower down to an insulated support about thirty feet to a box with a taped coil and capacitor in it tuned for minimum reflected power back at the radio. I think this would be a vertical antenna, although do not know if it’s affected by being that close to the face of the tower. The problem is general consensus was that just about everyone who was able to copy me says my signal sucks, so now it’s time for some improvements on my end. First question: is a vertical antenna worth using? Can the poor performance be an issue on not having enough radials? Would there be an advantage to shunt feeding the antenna to the top of the tower? Or am I just wasting time working with a vertical in the first place? And that leads to the second question: would it be better to just throw together a dipole cut for that frequency and put that up? Or maybe the same antenna as a sloper or inverted V?





RF


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