[Boatanchors] OT: antenna couplers?

[Nick England]

Well, not always - suppose you have a 300 ohm antenna hooked to 300 ohm
antenna lead - SWR is 1:1 (no reflected power) at the antenna tuner output -
and suppose the tuner is essentially a 6:1 impedance transformer - then the
SWR on the 50 ohm transmitter side is 1:1 also - everybody is happy.

But if your feedline impedance didn't match your antenna impedance, then you
wouldn't have 1:1 at the tuner output of course.

And if you hooked up the 50 ohm transmitter output directly to the 300 ohm
load, you wouldn't have 1:1 any more - *but*, as someone noted, with BA
transmitters, you could tune the pi-network so the xmtr output impedance was
300 ohms and you'd be happy again)

Note - I've probably introduced between 3 and 7 new errors - thinking about
SWR and feedlines always makes my head hurt.
cheers,
Nick KD4CPL

-----Original Message-----
From: boatanchors-bounces at mailman.qth.net
[mailto:boatanchors-bounces at mailman.qth.net] On Behalf Of Price Smith
Sent: Friday, January 09, 2009 12:22 AM
To: eugene at hertzmail.com; BOATANCHORS
Subject: Re: [Boatanchors] OT: antenna couplers?

Hi Eugene,

you will see 4:1 VSWR between the antenna tuner and the antenna,
The tuner only makes the mismatched antenna look good to your Xcvr or 
Amplifier.

73 Price W0RI


>
> 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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