Topband: Fw: Short Bogs

[Bruce]

.>> If we want to make an antenna electrically longer through cable velocity
>> factor, it can't be done by the insulation slowing the wave inside the 
>> shield.
>>
>> 73 Tom
>>
> In my experience, external insulation (through synthetic covering or 
> frost) lowers the resonant frequency of wire antennas of a given length 
> and height above ground.
>
> For example, I typically use 453/F as a starter length for insulated wire 
> dipoles...it's higher for bare wire of the same AWG diameter.
>
> It may not be due to "velocity factor" (not sure of the reason), but it is 
> observable and repeatable.
>
> 73, Gary NL7Y


 I also have had insulated wires of the same AWG diameter resonate lower in
 frequency than bare ones of the same length.

 Think we need multiple people experiment:

 Put up an antenna with covered wire. Measure the frequency, then cut the
 insulation away (of this same piece), and re-measure the frequency.

 If we get different results from different people, then we can start 
looking
 at the insulation. Is it economy grade made for 60 cycles (600 volts), or 
is
 it  the good stuff ???
 1. If it is low grade insulation with resistance at 1.8, 3.5 MHZ, then it
 may be making the wire appear to be "fatter". If true, then that would be
 valid reason.
 2. If the insulation is high quality at HF radio frequencies,  and IF the
 frequency changes, then we need to look further

 73
 Bruce-K1FZ
 www.qsl.net/k1fz/