[Boatanchors] OT: antenna couplers?

[Sandy]

Firstly, you didn't say what the antenna configuration was.  That aside, a 
VSWR meter is usually engineered for a particular impedance.  The antenna, 
in this instance being an unknown entity, could be very "reactive" 
inductively or capacitively, since your SWR bridge is giving you a high SWR. 
The antenna tuner/matcher is compensating for the reactance, and should be 
used between the transmitter and the antenna tuner.  If you intalled the SWR 
meter on the output side of the tuner the SWR would still be high there. 
High VSWR on the feedline will affect losses.  Usually coaxial feeders 
exhibit higher looses with increasing VSWR than open wire or "ladder line" 
type feeders, as the cable/feedline losses are usually less with parallel 
wire feeders.

A lot of other factors come into play.  What type antenna is it? (Dipole, 
end fed wire, off center fed, vertical? some sort of "array" or "beam"? 
Etc.)  What type and length feeder is being used?  With no tuner at what 
frequency or frequencies is the VSWR high? (Over say 3:1)  What is the 
length of the antenna and height above ground?  Is the antenna being used on 
more than one band?  Etc.

73,

Sandy W5TVW



  ----- Original Message ----- 
From: <eugene at hertzmail.com>
To: "BOATANCHORS" <boatanchors at mailman.qth.net>
Sent: Thursday, January 08, 2009 8:50 PM
Subject: [Boatanchors] OT: antenna couplers?


> Sorry for the OT.
>
> This is a basic question about tuners/couplers.
>
> Hypothetical Premise: My antenna gives a "bad"match to my transmitter at
> a given frequency (say 4:1 SWR). So I put an atenna coupler/tuner
> between the transmitter and antenna.
>
> I know that if the tuner is working well and is able to match the
> impedences, I will see a very good match between my transmitter and
> antenna coupler, maybe as good as 1:1 or 1.1:1. I would see that by
> using an SWR meter between my transmitter and the antenna coupler.
>
> The question is, what would I see if I put the SWR meter between the
> antenna coupler and the antenna? What would I see Would I still 4:1 SWR?
> Or would it still look like 1:1?
>
> Thanks for indulging (and yes, I will pull out the arrl handbook, but
> its nice to chat with some folks now and then)
> 73 Eugene w2hx
> _______________________________________________


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