RE: LF: VX9MRC QRV 507.77 kHz/ Arcing relays &c.

[Rik Strobbe <Rik.Strobbe@fys.kuleuven.be>]

Hello Stefan,

 

the formula for the capacitance of a vertical monopole with a height H (m) and a diameter d (m) is:

 

C(pF) = 24*H/log(1.15*H/d)

 

I got the formula from "Taschenbuch der Hochfrequenztechnik" by Meinke&Gundlach (3de edition, 1968)

 

Mit etwas Glück kannst du das Buch an der Uni auftreiben, es ist das lesen wert.

ISBN gab es dann noch nicht, aber Library of Congres Catalog Card Number ist 67-29831.

 

73, Rik  ON7YD - OR7T

 

 

 

---

Van: owner-rsgb_lf_group@blacksheep.org [owner-rsgb_lf_group@blacksheep.org] namens Stefan Schäfer [Stefan.Schaefer@iup.uni-heidelberg.de]
Verzonden: woensdag 12 oktober 2011 12:17
Aan: rsgb_lf_group@blacksheep.org
Onderwerp: Re: LF: VX9MRC QRV 507.77 kHz/ Arcing relays &c.

Hello Rik,

Interesting, haven't known that. What do you think applies for a 10mm diameter wire?

73, Stefan

Am 12.10.2011 09:30, schrieb Rik Strobbe:

I'm puzzled by the 6pf/metre rule for monoploes.  It seems the capacitance of the monopole is much higher.

 

Hi Joe,

 

based on a resonance with 3mH @137.8kHz the antenna capacitance would be 445pF.

A rato of 5..6pF/m you should have more or less 75..90m of wire up in the air (vertical and horizontal section).

But the given value of 5..6pF/m is only valid for thin wire. If you use very thick wire or maybe even a tower as part of the antenna the capacitance is larger. For a 1m diameter tower the capacitance can be as high as 25pF/m

 

73, Rik  ON7YD - OR7T