----- Original Message -----
From: "Larry Phipps" <larry@telepostinc.com>
To: "Towertalk" <Towertalk@contesting.com>
Sent: Monday, March 20, 2006 10:10 AM
Subject: [TowerTalk] LP-100 digital wattmeter with complex impedance display
>
> My LP-100 wattmeter, as featured on the cover of the Jan/Feb QEX, and
> shown at Dayton 2005 at the SteppIR booth, is now ready for sale. The
> LP-100 has excellent accuracy over a wide dynamic range (50 mW to 2500W)
> for both power and SWR. It has a unique combination of features too
> numerous to list here, including a nifty new complex impedance display.
> This screen adds Z, R and X display from 0-999.9 ohms to the long list
> of features.
>
> The LP-100 is being offered in both kit and assembled form. I am taking
> orders for the first production run through March 27, with deliveries
> expected starting in late April. I will be showing it at Dayton again,
> this time at my own booth, and taking orders there for a second
> production run as well. Sorry, I don't have the booth number yet, but
> will post it on the website when I get it from the Hamvention folks.
>
> For more info, see www.telepostinc.com/lp100.html
>
> Larry N8LP
Larry, on your website you state:
"As you can see from the above readings, it's important to
know more than SWR. An impedance of 39 + j39 ohms
is a far cry from 55 + j0 ohms.. . but both loads would read
1.1:1 on a standard wattmeter! "
I agree that 39+j39 is a far cry from 55+j0, but how do you
figure that either impedance would read 1.1:1 VSWR on a
standard wattmeter? A load of 39+j39 corresponds to
a VSWR of 2.4:1, not 1.1:1. If you connect a 39+j39 load
to a Bird wattmeter (or any other reasonable good bridge
type wattmeter), its going to read ~17% reflected power
(-7.5 dB return loss), not 0.2% reflected power (-27dB
return loss). Equal VSWRs don't imply equal impedance
magnitudes (only equal reflection coefficient magnitudes).
73, Mike W4EF............................................................
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