[Elecraft] K3 SWR Accuracy - reprise

[Wayne Burdick]

The KAT3 cannot be completely removed from the circuit. When it is in  
"BYPASS" it uses very small L/C values to attempt to compensate for  
its own strays. There is not an actual bypass relay.

73,
Wayne
N6KR

On Nov 4, 2009, at 6:10 AM, Stewart wrote:

> Of course Robert, the ATU was OFF. My typing error.
> Any measurements made with it ON would be meaningless.
>
> 73
> Stewart G3RXQ
> On Wed, 4 Nov 2009 07:14:43 -0600, Robert Naumann wrote:
>> After reading your table and comments again, I'm also curious
> why you are
>> using the antenna tuner in these measurements?
>>
>> Shouldn't the internal ATU be OFF in order to evaluate the SWR
> meter?
>>
>> With the tuner on, the K3's SWR meter is showing the results of
> the tuner
>> doing it's job - no? I would hope that the K3 SWR meter would
> read different
>> in this case.
>>
>>
>> -----Original Message-----
>> From: elecraft-bounces at mailman.qth.net
>> [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Stewart
>> Sent: Wednesday, November 04, 2009 2:45 AM
>> To: Elecraft Reflector
>> Subject: [Elecraft] K3 SWR Accuracy - reprise
>>
>> Hi,
>> Now traffic on the new K3 Macro functions has somewhat died
> down,
>> I would like to raise again the issue of the K3's SWR
> measurement
>> accuracy.
>>
>> I did some tests using dummy loads and a LP-100 meter as
> follows.
>>
>> The dummy load is a precision 100W one which I measured with a
> VNA
>> and has a VSWR of <1.03 from 1 to 30 Mhz. To simulate a 2:1 VSWR
>> I used another dummy load (not quite as good) in parallel.
>>
>> The K3 output was from ANT1 using the internal ATU. The ATU was
>> automatically tuned to 1:1 on all bands.
>> The results I got for 2:1 VSWR are as follows:-
>>
>>              LP-100           K3
>> 160         1.99                1.8
>> 80           1.99                1.8
>> 60           1.99                1.8
>> 40           1.95                1.8
>> 30           1.97                1.6
>> 20           1.97                1.4
>> 17           1.97                1.3
>> 15           1.96                1.2
>> 12           1.96                1.5
>> 10           1.96                1.4
>>
>> As can be seen my K3 SWR indication consistently under reads.
>> However, it really gets bad on 20,17 & 15.
>>
>> From previous replies I understand that this under reading would
>> be compensated for in the firmware, sometime in the future .
>>
>> Is this still on the list of problems to be addressed ?
>>
>> 73
>> Stewart G3RXQ
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