[Amps] Dummy Loads & Wattmeters

[Carl]

The Cantenna resistor was only 20% tolerance to start with and aging has 
increased it a bit, pretty common.

I also have some brand new military packaging sealed 50 Ohm 50W Carborundums 
that measured 68 Ohms upon opening.

They still make great swamping resistors or for parasitic suppressors.

Carl
KM1H


----- Original Message ----- 
From: "Steve Katz" <stevek at jmr.com>
To: <dhallam at rapidsys.com>; "AMPS List" <amps at contesting.com>
Sent: Wednesday, December 02, 2009 12:27 PM
Subject: Re: [Amps] Dummy Loads & Wattmeters


> Yep, there is.  An accurate power measurement with the model 43 is 
> P(actual) = Pf (indicated) - Pr (indicated).  With a 70 Ohm load you 
> should have a VSWR of 1.4, a return loss of about 15.6 dB, or about 3% 
> reflected power, so the Bird should read "high" by about 3% when viewing 
> indicated Pf.
>
> But I'd look into why the load measures 70 Ohms!  Check your Ohmmeter if 
> you can to verify its accuracy, and if that seems good, probably the 
> load's been overheated and the resistor should be replaced.
>
> WB2WIK/6
>
> -----Original Message-----
> From: amps-bounces at contesting.com [mailto:amps-bounces at contesting.com]On
> Behalf Of David C. Hallam
> Sent: Wednesday, December 02, 2009 9:16 AM
> To: AMPS List
> Subject: [Amps] Dummy Loads & Wattmeters
>
>
> A little education, please.
>
> I am working on restoring an old transceiver and linear.  I have a Bird
> 43 wattmeter and a Heath Cantenna dummy load.  The wattmeter is for 50
> ohm impedance and I measure the DC resistance of the Cantenna at 70 ohm.
>
> Is there any effect on the wattmeter reading from this mismatch?
>
> David
> KW4DH
> -- 
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