Hi to all
The best way modeling a short antenna is to use a good
software as EZNEC (on the way, the new 6.0 version is on the W7EL site).
But also you can have a look at one of all time best paper
speaking about the short antennas on low bands : the Rick ON7YD here :
http://www.strobbe.eu/on7yd/136ant/
You can easily found that a 2 meters long 2 cm OD vertical whip has 23 pF
Best 73 - Andy F6CNI.
P.S. Again sorry about my poor english...
-----Message d'origine-----
From: John Rabson
Sent: Thursday, May 28, 2015 4:24 PM
Subject: Re: LF: MF mobile ?
> I recall a few years one of the British Telecommunications journals
(POEEJ/BTTJ/IBTE/TCNJ - I forget which name it was using at the time) had an
item about a low-loader mounted LF/VLF station which had a radiator supported by
a helium balloon. Or was it the Navy's definition of mobile: anything you
can move around with a battleship?
John F5VLF
>
> Hmm, i find someone should do a real mobile (mobile-mobile, with a
velocity > 0) experiment. A 1.5 m long CB antenna with a special preparated
feed point should work. And i think that the wire works better with a fixed C in
parallel, even if this reduces the efficiency. But it stabilises the SWR or
better said, the voltage on the wire. Corona? Where is the problem with corona?
:-)
> Markus, could you calculate the ERP when 10 kV rms is applied to a
1.5m high antenna on a car roof? I bet you have all the formulas in your mind
:-)
>
> Maybe the antenna has 10 pF. I remember i
have a 470pF/16kV capacitor at home. So if C = 470 pF and f = 475 kHz, L = 239
uH With 470 pF parallel to the antenna, a moving wire (= changing C) does not
make a significant effect i think.
> 10 kV at 239 uH at 10 kV is 14A. If P = 200 W, the losses must be 1
Ohm !
> With a good RF litz wire, this is possible :-)
>
> What would be the ERP and possible distance?
>
> It would be interesting to try that in WSPR / QRSS-60 :-) I would also
drive to someone for making a CW QSO but most likely there is a LOT of QRM when
driving...
>
> More ideas?
>
> 73, Stefan
Researching history of RABSON, BLACKSHAW, GAUNTLETT, VERLANDER and
ROBSONNE
