[MRCA] static discharge reel for antenna

[Gene Smar]

Eugene:

     I'd go with the uninsulated cable reel.  That way, the wire left on the 
reel is nothing but a blob of conducting material and not a choke - or 
loading coil.  I believe there is a similar wire reel that is used with 
manpack HF radios.  Maybe someone here can identify the A/N number.  This 
device makes one half of a dipole or it can be used singly for an end-fed 
wire.  The reel s hung onto a support by a non-conductive cord of some kind.

     You can even make up one of these by using a plastic camping clothes 
line reel as trhe container.  I bought one at a local sporting goods store a 
few years ago with the thought of replacing the nylon string with bare wire. 
There also is a hints-and-kinks article in the November QST that describes 
using a framer's chalk reel to hold the wire.

     Good luck and let us know what you decide and how it works.


73 de
Gene Smar  AD3F


----- Original Message ----- 
From: "W2HX" <w2hx at w2hx.com>
To: <mrca at mailman.qth.net>
Sent: Sunday, October 13, 2013 1:46 PM
Subject: [MRCA] static discharge reel for antenna


Hi folks.

BACKGROUND
I have an 8m mast on the back of my 72 land rover. When I deploy, I either 
run a wire up it for a vertical (which seems to work fine) or hang a dipole 
on it as an inverted V.  I am always trying to make deployment as simplified 
as possible. So I was thinking of using one of these retractable reels used 
for static discharge in situations like fueling etc.  Basically it's like 
the old laundry line in the back yard. Spring loaded, retractable. The idea 
would be to mount it on the land rover and have the cable attached to the 
top of the mast. Then, all I need to do is raise and lower the mast and the 
wire is already in place.

There seem to be two main types of these reels that I can see. One type uses 
un-insulated wire and uses the body of the reel to complete the connection 
to ground. Meaning the paint is removed from the mounting points of the reel 
to make electrical connection to something metal as ground.  The second type 
uses an insulated cable and the internal end of the cable connects to the 
outside of the reel, making the internal end accessible. In turn, again, the 
reel is grounded.

In the first case, I would need to mount the reel in such a way that it is 
insulated from the body of the vehicle so that I can use it as an antenna 
radiator. This will be some small challenge to accomplish.  The base of the 
reel body, insulated from the vehicle body, would then connect to the output 
of the antenna coupler.

In the second case, when the cable emerges from the reel, I was thinking of 
putting on a single-conductor connector (like a single power pole) when the 
cable is fully reeled out, I can then connect a wire from the antenna tuner 
to this power pole.  By disconnecting the internal end from the reel and 
connecting to the power pole, the reel and reel housing are no longer part 
of the circuit and can mount on the body as needed.

QUESTION:
The second type of reel (with insulated cable) seems to come in 50-foot 
lengths. This means that about 25 feet will remain on the reel in a loop 
about 3-4 inches in diameter. I am worried that this will create an RF choke 
and reduce the performance of the radiator. Or, it might make some kind of 
base loading, I really don't know.

Of course an alternative would be to cut down the cable to 25-26 feet or so, 
but I was wondering if anyone had thoughts about the effect of having this 
25' coiled before the vertical radiator.

Thanks for the bandwidth of a very wide band email!



73 Eugene W2HX




______________________________________________________________
MRCA mailing list
Home: http://mailman.qth.net/mailman/listinfo/mrca
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:MRCA at mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html