[antennaware] L-match component specification

David Gould david.gould@btinternet.com
Mon, 11 Jun 2001 21:54:18 +0100

Last winter I installed a 105ft vertical at my alternative location based 
on a modified version of the titanex 160HD.  I fed it through an L-match
comprising a coil from antenna to earth and a capacitor from the antenna
to the 50ohm coax feeder.  I was able to match it easily on both 160 
and 80 and it worked very well.  

Changing bands or moving up from 1.835 necessitated going to the 
base of the antenna and changing coil taps and capacitor values.
I want to put in remote switching before next season.  

I would like some help in three questions so that I can select 
relays and capacitors that will withstand the voltages and currents
that will exist at different frequencies and power levels. 

1) I would like to be able to work out the voltage across, and current
    through the series capacitor at different power levels and at 
    different frequencies.  Are there any standard formulae I can use?

2) I know there are a few circuit analysis programs around, does 
    anyone know of a suitable shareware program? I would like to
    be able to investigate all the voltages and currents.   

3) I am also not sure how to represent the complete circuit to include 
    the antenna load and the 50ohm feed. Can anyone help?

The figures I have from modelling are as follows
1.85MHz with 400w input
Source imp =  20 - j100
Voltage = 456 @ -79deg 
Current  = 4.5A @ 0deg
Coil       = 6uh
Cap       = 560pf

3.65MHz with 400w input
Source imp  = 409 + j485
Voltage  =  627 @ 50deg
Current   =  1A @ 0deg
Coil        = 13 uh
Cap        = 202pf

Thanks in advance for any help or advice,

Dave G3UEG

FAQ on WWW:               http://www.contesting.com/FAQ/antennaware
Submissions:              antennaware@contesting.com
Administrative requests:  antennaware-REQUEST@contesting.com
Problems:                 owner-antennaware@contesting.com