Thanks! Antennas are a science all on their own and I LOVE to mess with them.
Any information I can get on them helps!
I like to hear how others fix/modify/build their antennas!
I know that it may seem off topic, but it IS related to Ham Radio!
Thanks again!
Rod
KC7CJO
--- On Thu, 1/8/09, Rick W <mrf...@frontiernet.net> wrote:
From: Rick W <mrf...@frontiernet.net>
Subject: Re: [digitalradio] OFF TOPIC
To: digitalradio@yahoogroups.com
Date: Thursday, January 8, 2009, 11:22 AM
J-Poles, or for that matter, SlimJims, could be built for either
portable or fixed operation from 450 ohm slotted twin lead. I have a
fixed home J-Pole constructed from 450 ohm window line and sealed in
PVC. Because the velocity factor is significantly slowed down by the
PVC, you have adjust the size of the antenna. The 450 ohm line is
available from ham dealers such as AES, etc.
There are two kinds of 450 ohm twin lead that I have used. The very
heavy duty type with multistrand 14 AWG and the much lighter single
strand 18 AWG. While I don't recommend the 18 AWG for long term use,
e.g., making an open wire fed antenna, or G5RV and ZS6BKW types, this
can work well for lighter weight portable dipoles, and making J-Poles
for VHF, either free hanging or inside a PVC. For back packing I would
choose the TV twinlead and have it as a roll up and if I used a walking
stick, would have a ready short mast.
Of course you only need the twin lead for the Q section and the main
half wave part of the antenna can be wire. I have done it both ways.
When using the 450 ohm line inside PVC it tends to stay firmly upright
and does not sag like wire is prone to do.
The reason I don't like the copper tubing designs is the exposure of the
connections to the weather. With a soldered connection on the J-Pole
encased in PVC, it seems to work well. I use a different approach with
the addition of a bottom "Tee" which is positioned so the feedpoint is
at right angles to the Q section. I hope to have a write up about this
in the files section of the hfdec yahoogroup to add to our antenna
projects section. It can never be published in QST since it is not
finessed and uses things like electrical tape to throw it together, HI.
73,
Rick, KV9U
Rodney wrote:
> I haven't been following this thread until now, but are you building
> these antennas for portability or are you using them in a base
> configuration?
>
> I've found 300-ohm twinlead to be the best as far as portability and
> ease of construction. I live in the Portland Oregon area and haven't
> seen any 450-ohm ladder line, anywhere, at least not for sale.
>
> I've never worked with it so I really can't make many comments on it,
> but it would seem to be harder to work with and the physical size
> wouldn't make it condusive to back packing!
>
> Personally, I have a copper J-Pole that I can break down and take with
> me every where I go. I also have the twinlead J-Poles that have
> served me well in most mobile situations!
>
> Just my thoughts!
>
> Rod
> KC7Cjo
>
