Fw: Fw: Re: [Antennas] 450 Ohm Ladder Line

[Sandy and Kees Talen]

Here is experiment #1. I still need to find a milli-wattmeter so I
can make measurements using my signal generator, so power loss
will have to wait.

Test to be done at 15Mhz and 30Mhz on 50ft of Wireman type 551 
ladder line which consists of 2 #18AWG solid wires separated by 
0.80". If this was open line, the impedance would be very close to 
450 ohms. Since this has the polyethylene dielectric, the impedance 
will be less as has been pointed out by testing others have done.
Larger wire will also lower the impedance.
 
I did measure capacitance, which has a direct bearing on line loss
(among others).  

Original 551 ladder line DRY capacitance 2.96 pf/ft
                                       WET capacitance 10.32 pf/ft

551 ladder line with 7/16" holes in all webs (see below)
                                       DRY capacitance 2.92 pf/ft
                                       WET capacitance 7.10 pf/ft

551 ladder line with 7/16" holes in all webs and every other web
      removed (see below)
                                       DRY capacitance 2.86 pf/ft
                                       WET capacitance 5.20 pf/ft

The 7/16" holes were made with a gasket punch in the drill press
(running) ....real easy and fast. Cut the web down to 1/8" between 
holes. The number of holes will vary from 2 to 4 since the webs 
are different sizes. No observable loss of required mechanical 
rigidity.

Removing every other web results in webs at 6.5" (on average)
intervals. More than enough to maintain mechanical spacing.

The line, as a result of the above, is also less wind sensitive.

73  Kees K5BCQ