[Elecraft] K3 Internal Tuner Question

[Don Wilhelm]

Buck,

You are like the man with 2 (or more) watches who never knew what time 
it was!

Was your LP-100A calibrated to NIST traceable standards (Larry's 
calibration tools)?
If the answer is yes, I would use the LP-100A as the "standard" to 
calibrate the K3 wattmeter (see instructions in the manual).
After having calibrated the internal wattmeter in the K3, then run the 
TX gain calibration with K3 Utility.

73,
Don W3FPR

On 1/3/2012 8:50 AM, Buck k4ia wrote:
> Well here's one for you:
>
> My setup is K3 to wattmeter to dummy load.
>
> The K3 says 100w
> If the external wattmeter is:
> MFJ 949E tuner/SWR meter (tuner out of circuit) it says 100w
> cheapo Radio Shack SWR meter 100w
> LP 100A digital wattmeter says 70 watts
> Elecraft W2 says 70 watts
>
> Yes, I have run the transmitter calibration routine in the K3 Utility
> program.  SWR in all three cases is nominal 1:1
>
> The result is the same to a real antenna although the SWR is not 1:1
>
> What could be causing the external-sensor type wattmeters to read low?
>
> Buck
> k4ia
> K3 # 101
>
> On 1/2/2012 10:14 PM, Ron D'Eau Claire wrote:
>> Quite right.
>>
>> There a couple of impedance transformations that occur between the
>> collectors (or plates) of the power amplifiers and the antenna. The first is
>> done by the output filters. In modern rigs, they are fixed tuned and
>> designed in common Ham rigs to convert the impedance at the collectors to 50
>> ohms, resistive.
>>
>> If your antenna presents that impedance, no further conversion is necessary.
>> But many antennas don't.
>>
>> In the "old" days the output network was adjustable and we simply did the
>> necessary adjustments and all was good.
>>
>> Nowadays, with fixed tuned amplifier output networks, we need another
>> matching network to handle the conversion when the antenna doesn't present a
>> 50 ohms resistive load.
>>
>> Enter the "antenna tuner" that converts what the antenna shows to the 50
>> ohms needed by the output filter. The built in SWR meter displays the SWR on
>> the link between the tuner and the output filter.
>>
>> Ron AC7AC
>>
>> -----Original Message-----
>> From: elecraft-bounces at mailman.qth.net
>> [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Tom Azlin N4ZPT
>> Sent: Monday, January 02, 2012 6:19 PM
>> To: elecraft at mailman.qth.net
>> Subject: Re: [Elecraft] K3 Internal Tuner Question
>>
>> Thanks Matthew. I should not have spoken like that. Should just
>> have said the meter in the line would not change just because a radio
>> tuner transformed impedance to make the radio happy. 73, tom n4zpt
>>
>> On 1/2/2012 9:11 PM, Matthew Pitts wrote:
>>> Tom,
>>>
>>> All an antenna tuner does is show the radio the load it expects; the
>>> SWR will still be high at the output of the tuner, and an SWR meter
>>> in the coax at that output will show it as it actually is at that
>>> point, not as it is on the input of the tuner/output of the radio.
>>>
>>> Matthew Pitts N8OHU
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