[VHFcontesting] Coax for VHF / UHF

[Marshall Williams]

Hello again to everyone.....Mike has found THE Times Microwave Chart 
that I was trying to send to everyone.  That second link is the one.  I 
could not find that chart on the web anymore, so 2 AttaBoys to Mike for 
the FB link.  Thanks Mike.

This chart has a  lot of different types of coax and the loss figures 
for each at different frequencies.  It is well worth downloading and 
storing on your own machine(in case it disappears again).  I have spent 
a lot of time learning the most important coaxes in this chart.  I use 
it whenever I teach a class to beginners on antennas, feedlines, etc.  
It is really a wealth of good information. 

The other chart that I included in the original post showing db loss vs 
how much power makes it to the top of the feedline is another one that 
is really important.  Most guys just don't think that 1db is anything to 
worry about.....but that is a 21% loss!!  It really helps to keep that 
second chart in mind when planning an antenna installation.  If you know 
that the total feedline length will be 200ft, you must plan to use 
really good feedline to avoid losing your shirt in feedline losses.  
With 200ft of 1 5/8" Heliax(LDF7) on 2M, you will lose 0.54db and if you 
run 1000W into the coax, you will get 879W out at the top....a loss of 
12.1%.  If you used LMR-400, you would lose 3db or HALF your power. 

Most new VHFers just don't realize how much they are throwing away when 
they try to use old, lossy, or just plain unsuitable feedline.  It is 
really hard to get an HF guy to understand how important this is.  They 
are so used to using RG-213 for everything, that you have to beat them 
up about the head and shoulders with a short piece of LDF5 to get them 
to understand what is going on(as Foghorn Leghorn says, "That is a joke, 
Son!"). 

Anyway, enjoy the chart.....take the information to heart.....see you on 
the VHF / UHF bands....especially in the contests.....73's Marshall K5QE

Mike (KA5CVH) Urich wrote:

>On Tue, Aug 19, 2008 at 20:12, Marshall Williams <k5qe at sabinenet.com> wrote:
>
>  
>
>>Hi Rich.....this is a serious topic and unfortunately has a lot of "IFs,
>>ANDs, or BUTs".
>>    
>>
>
>Mike wrote
>
>Marshall's comments are right on target.  The only thing I could add
>is links to a couple of charts.
>
>http://harriscountyares.org/training/training_coax_comparison_01.pdf
>http://harriscountyares.org/training/training_coax_comparison_02.pdf
>
>
>  
>