Radio shack sir meter.

[Mark Flavin]

Im trying to calibrate my k 1 and bought a radio shack swr bridge.  With a  
50 ohm load I can tune without it but with it I get a dry high swr.  I  
measured the coax connectors and get a short between the two coax centers  
and the grounds.  It recieves ok but I can't get a  decent tx reading.  
Anyone know fit is just too cheap to work for this?  Thanks.

Mark. N5MF

T-Mobile. America's First Nationwide 4G Network.

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[Don Wilhelm-4]

Mark,

You did not say what part of the K1 you are trying to calibrate.  If it
the forward power reading of the KAT1, then it should be useful within
the range of its accuracy.

There are other ways to measure power and achieve good accuracy --
At the 7 watt or less power level of the K1, you can use an RF Probe
connected across the dummy load, or use a 'scope with a 10X probe.  That
will provide you with the RF voltage level being fed to the dummy load.
To calibrate the RF probe or 'scope reading - remove the KAT1 from the
K1 and set the OUT menu parameter to 4 or 5 watts and do a TUNE.  Note
the reading on your DMM from the RF Probe or the vertical deflection on
the 'scope - that is the RF voltage produced at the level indicated on
the K1 display (5 watts should indicate about 14 volts with the RF
Probe, or 44.7 volts peak to peak on the 'scope).  The internal K1 RF
detector is quite accurate as long as the load is 50 ohms pure
resistive.  Now you know how the RF Probe of 'scope react to that
particular power level - record the voltage reading and the power
indicated on the K1.

Now put the KAT1 back in.  (I assume you have already balanced the KAT1
wattmeter and achieved a very good null - if not, you must do that
first.)  With the ATU menu set for CLP, do a TUNE and tap the WPM+ or
WPM- buttons to achieve the same RF voltage you had without the tuner
installed.  Then adjust the FWD trimmer on the KAT1 so the K1 display is
the same as you had before.  That method will actually be more accurate
than using an external wattmeter.  You are using a comparison of the
indication on your RF Probe (or 'scope), so those devices do not have to
be well calibrated - the only assumption you have to make is that the
base K2 power indication is accurate, and I have always found that to be
true after working with many K1s.

73,
Don W3FPR


73,
Don W3FPR

On 11/9/2011 3:49 PM, Mark Flavin wrote:

> Im trying to calibrate my k 1 and bought a radio shack swr bridge.  With a
> 50 ohm load I can tune without it but with it I get a dry high swr.  I
> measured the coax connectors and get a short between the two coax centers
> and the grounds.  It recieves ok but I can't get a  decent tx reading.
> Anyone know fit is just too cheap to work for this?  Thanks.
>
> Mark. N5MF
>
> T-Mobile. America's First Nationwide 4G Network.
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

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