[Boatanchors] OT: antenna couplers?

[Bob Macklin]

Like Glen comments the old boatanchors that used Pi-Network outputs did not
need tuners. The Pi-Network is a tuner.

I always use a 1/2 wave dipole or a 1/4 vertical ground plane type antenna.
You can also make a multiband antenna using traps.

Bob Macklin
K5MYJ
Kent (Seattle), Wa,
"Real Radios Glow in the Dark"

----- Original Message ----- 
From: "Glen Zook" <gzook at yahoo.com>
To: "BOATANCHORS" <boatanchors at mailman.qth.net>; <eugene at hertzmail.com>
Sent: Thursday, January 08, 2009 7:10 PM
Subject: Re: [Boatanchors] OT: antenna couplers?


> The purpose of the antenna coupler (tuner, whatever) is to match the
transmitter to the feedline.  It has no effect on what you would "see" if
you put your SWR bridge on the output of the tuner.  That impedance does not
change.  What does change is the SWR that the transmitter "sees" and
therefore should make the transmitter much "happier".  The transfer of
energy into the antenna should be more efficient than if the transmitter is
not able to "match" the impedance of the antenna.  However, there will be
losses in the coupler so there will not be a 100% transfer of energy.
>
> Remember that the SWR bridge "assumes" (usually) that the transmitter
wants to see a 50 ohm load and then the SWR reading is a ratio of what the
SWR brige is expecting to see and what the actual impedance is.
>
> Many of the older transmitters could handle a "mere" 4:1 mismatch without
any problems (probably 200 ohms in this case) and therefore an SWR bridge
was not in general use until transmitters started having a fixed, or close
to fixed, 50 ohm output.  My WRL Globe Champion 350A can match up to at
least 300 ohms, my Heath DX-100 can match up to at least 600 ohms, and my
Hallicrafters HT-20 can match up to at least 2000 ohms.  That means at least
a 6:1 for the Globe Champ, 12:1 for the DX-100, and 40:1 for the HT-20!
>
> In the "goode olde dayes" amateur radio operators didn't worry about SWR.
If the transmitter could "load" the antenna and they made contacts they
didn't worry.  If the transmitter didn't load the antenna very well then
they made adjustments to the antenna.  From May 1959 (when I got my Novice
Class license) until after I graduated from college in 1967 I didn't even
own an SWR bridge.  After I graduated from college I eventually did build a
"monimatch" type of SWR bridge but didn't really use it for quite some time.
>
> Glen, K9STH
>
> Website:  http://k9sth.com
>
>
> --- On Thu, 1/8/09, eugene at hertzmail.com <eugene at hertzmail.com> wrote:
>
> 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)
>
>
>
> _______________________________________________
>