Topband: Capacitor for Inverted L

[Wes Attaway (N5WA)]

The question of "matching" an Inverted-L comes up every now and then, and
under some circumstances it may be necessary to install some kind of
matching network, particularly if you want to operate across the entire
band.

However, for most situations I do not think a matching network is necessary
because the SWR will likely be easily "controllable" by simply adjusting the
length of the horizontal wire.  Even if you don't want to try this the
native SWR of a normal Inverted-L will be less than 2:1 for about 100KHz of
bandwidth.  Feedline loss is negligible on 160 and, in any event, most
transceivers and amps can easily match whatever impedance you encounter.

If you model a simple Inverted-L you can see that adjustments of a few feet
for the horizontal wire will put the low SWR point just where you want it in
the band and the radiation pattern is not changed to any meaningful extent. 

So, for most people, fooling with a matching network won't buy you anything
but a lot of trouble and it adds another place for things to go wrong.  In
my opinion, the best thing to do is to put up the antenna, check the SWR,
make a length adjustment if you think it is necessary, and then go get on
the air and make some QSOs.

If you want to spend some time "fiddling" then my recommendation would be to
spend it on your ground radial system, not worrying about a matching
network.  As your radial system improves the matching will change, but you
can still make horizontal wire adjustments as well.

----------------- Wes Attaway (N5WA) ------------------- 
1138 Waters Edge Circle, Shreveport, LA 71106 
    318-797-4972 (Office) - 318-393-3289 (Cell) 
        Computer Consulting and Forensics 
-------------- EnCase Certified Examiner --------------- 


-----Original Message-----
From: topband-bounces at contesting.com [mailto:topband-bounces at contesting.com]
On Behalf Of Lup Schlueter
Sent: Thursday, October 13, 2011 9:49 AM
To: topband at contesting.com
Subject: Re: Topband: Capacitor for Inverted L

Hans Gatu SA7AUY had a very cool idea for a selfmade variable power 
capacitor.
It has about 300pf, but as you will agree, there is no limit for 
higher values.The material
will surely agree every flash over!

See self:   http://www.heathkit.nu/heathkit_nu_AMU.html

55 Lup, DJ7SW



Am 13.10.2011 13:05, schrieb Gary Smith:
> I used to use an ugly, beat up 500pf vac variable at the base of my
> 160M inv-L&  used the MFJ SWR Analyzer to adjust it. The CAT-5 cable
> I used for wire was brought up over a tall tree and chafing from the
> wind blown branches wore through it 1/2 times a year. After the
> antenna came down the last time I used a more rugged wire and cut it
> 135' long and have it connected to a radial plate which serves as a
> common tie-in for my separate 160, 80, 40, 30 meter vertical wires
> but also my butternut HF9V which I use for 20&  up.
>
> The 160M ant will not cover the whole band but as I rarely go above
> 1.9 Mhz, it's perfect and needs no base loaded cap.
>
> YMMV.
>
> 73,
>
> Gary, KA1J
>
>> I plan on adding an Inverted L soon, and have seen a few websites that
>> recommend about 1000pF at the base to tune it.  What voltage cap should I
be
>> looking for if I am going to run about 600W?
>>
>> -- 
>> *Clint Talmadge - W5CPT - *
>> _______________________________________________
>> UR RST IS ... ... ..9 QSB QSB - hw? BK
>>
>
> _______________________________________________
> UR RST IS ... ... ..9 QSB QSB - hw? BK
>

_______________________________________________
UR RST IS ... ... ..9 QSB QSB - hw? BK