Topband: Fw: Short Bogs

[ZR]

If youre building a Beverage/BOG as the thread title indicates, resonance 
does not matter, it is a nonresonant slow wave antenna.

For a resonant antenna up in the air and used for transmitting the 
insulation adds 3-5% to the electrical length.

Carl
KM1H


----- Original Message ----- 
From: "Bruce" <k1fz at myfairpoint.net>
To: <topband at contesting.com>
Sent: Sunday, December 30, 2012 1:15 PM
Subject: Topband: Fw: Short Bogs


>
> .>> 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/
>
> _______________________________________________
> Stew Perry Topband Distance Challenge coming on December 29th.
>
>
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