Re: {Collins} Directional Coupler Problem

[Jim Simmons <orion@xxxxxxxxxxxx>]

First check the switch.  It could have dirty/corroded contacts.  If that 
checks OK, check the connections to the  meter.  If all this checks OK, 
then I would suspect the diodes.

Good luck,
Jim~N5MSJ

On 5/20/2015 9:01 PM, Richard Solomon wrote:
> I picked up a nice looking 312B-4, was touted as working ... but the 
> Power
> Measurements are wacky.
>
> Now, I have an HP Power Meter that just came back from the Cal Lab so I
> am confident my power readings are OK.
>
> Now, I put 110 watts (@ 21 MHz) through the coupler and get the following
> readings:
>
> Forward: 200 Watts   reads around 80 Watts
>               2,000 Watts  reads around 60 Watts
>
> I reverse the coax cables to read the Reverse Scale.
>
> Reverse: 200 Watts  reads around 40 Watts
>              2,000 Watts  no reading, nothing
>
> I checked the resistors in the coupler, reading from the terminal 
> strip (first
> I disconnected the leads) to the junction post in the coupler. I used 
> a cal'ed
> Keithley 196.
>
> All readings were within a few %.
>
> Any ideas what can be wrong ??
>
> Thanks, Dick, W1KSZ
>
>
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