[Icom] IC756 SWR meter compared with FC902 or DAIWA CN101

[George, W5YR]

You win, Larry . . . in almost all situations, the meter *inside* the rig is
the one to believe. It is actually not measuring a physical SWR but rather
is indicating the extent to which the actual load impedance differs from
50+j0 ohms. It is calibrated in terms of SWR for convenience of use and in
the interests of familiarity to most operators.

73/72, George
Amateur Radio W5YR -  the Yellow Rose of Texas
Fairview, TX 30 mi NE of Dallas in Collin county EM13QE
"In the 57th year and it just keeps getting better!"
<mailto:w5yr@att.net>





----- Original Message -----
From: "Larry" <larry_w@attbi.com>
To: <icom@mailman.qth.net>
Sent: Friday, March 21, 2003 10:14 AM
Subject: Re: [Icom] IC756 SWR meter compared with FC902 or DAIWA CN101


I suspect the difference lies where in the chain of events the SWR meter
for the 756 is located.

I bet the order of the equipment is: 756 final >> 756 SWR circuitry >> 756
tuner >> 756 antenna connector >> external SWR bridge. If that's the case,
when the 756 tuner has done it's thing, the 756 SWR circuit will see a
reduced SWR as a result of the 756 tuner while the external SWR bridge does
NOT see the the same thing. It sees the actual SWR that exists on the
coax/antenna.

73 - Larry W�NFU
larry_w@attbi.com



At 02:16 PM 3/21/2003 +0100, you wrote:

>Hi,
>
>I have a IC756 and building an antenna I was comparing the values provided
>by IC756 SWR meter and other meter such as the one that comes with FC902
>Tuner from Yaesu or DAIWA CN101 METER and I see some differences. For
>instance, when IC756 points out 1.5:1 the FC902 is indicating  that the
>SWR is 3:1. I'm quite concerned because I can not trust on the numbers
>provided by IC756 SWR meter and a bad mismatch with the antenna could
>provoke the blowing up of the PA finals.
>
>How could I adjust the SWR meter of the IC756 to be sure that I can trust
>on its values?
>
>Thanks
>
>73s Juan