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KX3/KXPA100 Power Output Difference

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KX3/KXPA100 Power Output Difference

I using a KX3/KXPA100 and I'm noticing that when I'm in TX the RF meter on the rig matches the set power of the rig, but on the KXP100 meter, it shows 10 or more watts less output. Some examples:Rig Amp50w 40w60w 50w70w 60w80w 70w
Here is what i've checked so far. The Powerwerx PS is showing 13.8v when receiving and dips to 12.9v when in TX, so I don't believe I have a voltage problem. I've moved the rig's power connection back and forth from the front of the Powerwerx PS to the top power pole connection on the back of the KXPA100 with no change.I've also re-tuned all bands from 10-40 meters with my LDG100 remote tuner and the highest SWR I receive is 1.4:1 on 30 and 40 meters. All of the other bands are 1:1 to 1.2:1, so I don't think I'm getting any power foldback because of high SWR.. Does anyone have any thoughts on what's causing this differential, and if two power output meters are never going to be in sync, which meter is the most accurate?
Also, as an aside. Is there something wrong with the KX3 group from Yahoo? I haven't recieved a digest in days and when I try to get into the group I get an error message
Thanks,Jim W7JHR
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Don Wilhelm

Re: KX3/KXPA100 Power Output Difference

Jim,

Amateur wattmeters are notoriously "famous" for their inaccuracies.
Errors of up to 20% are not unusual, and in many cases it depends on the
band because the voltage produced by the measurement diodes are
frequency dependent.

So bottom line, don't worry about the 10 watt differential. You are
like the man with two watches who does not really know what time it is!

On the KX3 Yahoo Group question, I receive individual emails (not the
digest), but something has happened, and I cannot post to any of the
Yahoo groups that I am subscribed to for the past 2 weeks. I think
Yahoo has "gone to the dogs".

73,
Don W3FPR

On 12/1/2017 9:33 PM, Jim Ruff via Elecraft wrote:

> I using a KX3/KXPA100 and I'm noticing that when I'm in TX the RF meter on the rig matches the set power of the rig, but on the KXP100 meter, it shows 10 or more watts less output. Some examples:Rig Amp50w 40w60w 50w70w 60w80w 70w
> Here is what i've checked so far. The Powerwerx PS is showing 13.8v when receiving and dips to 12.9v when in TX, so I don't believe I have a voltage problem. I've moved the rig's power connection back and forth from the front of the Powerwerx PS to the top power pole connection on the back of the KXPA100 with no change.I've also re-tuned all bands from 10-40 meters with my LDG100 remote tuner and the highest SWR I receive is 1.4:1 on 30 and 40 meters. All of the other bands are 1:1 to 1.2:1, so I don't think I'm getting any power foldback because of high SWR.. Does anyone have any thoughts on what's causing this differential, and if two power output meters are never going to be in sync, which meter is the most accurate?
> Also, as an aside. Is there something wrong with the KX3 group from Yahoo? I haven't recieved a digest in days and when I try to get into the group I get an error message
> Thanks,Jim W7JHR
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
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> Please help support this email list: http://www.qsl.net/donate.html
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Bob McGraw - K4TAX

Re: KX3/KXPA100 Power Output Difference

Don's points are very good. Add to that the resistance or load value
to which the power indicator was calibrated. Ideally it is 50 ohms R
+j0. However, being a voltage sensing circuit, any deviation from 50
ohms will impact the indication. Thus a 55 ohm load, showing a SWR of
1.1:1 can cause a 10% error as a higher power indication. And with a
45 ohm load, showing a SWR of 1.1:1, will show a 10% lower power
reading. Many ham watt meters are only accurate to about 20% of full
scale largely to the above as well as circuit components being frequency
dependent.

73

Bob, K4TAX

On 12/1/2017 10:23 PM, Don Wilhelm wrote:

> Jim,
>
> Amateur wattmeters are notoriously "famous" for their inaccuracies.
> Errors of up to 20% are not unusual, and in many cases it depends on
> the band because the voltage produced by the measurement diodes are
> frequency dependent.
>
> So bottom line, don't worry about the 10 watt differential. You are
> like the man with two watches who does not really know what time it is!
>
> On the KX3 Yahoo Group question, I receive individual emails (not the
> digest), but something has happened, and I cannot post to any of the
> Yahoo groups that I am subscribed to for the past 2 weeks. I think
> Yahoo has "gone to the dogs".
>
> 73,
> Don W3FPR
>
> On 12/1/2017 9:33 PM, Jim Ruff via Elecraft wrote:
>> I using a KX3/KXPA100 and I'm noticing that when I'm in TX the RF
>> meter on the rig matches the set power of the rig, but on the KXP100
>> meter, it shows 10 or more watts less output. Some examples:Rig
>> Amp50w 40w60w 50w70w 60w80w 70w
>> Here is what i've checked so far. The Powerwerx PS is showing 13.8v
>> when receiving and dips to 12.9v when in TX, so I don't believe I
>> have a voltage problem. I've moved the rig's power connection back
>> and forth from the front of the Powerwerx PS to the top power pole
>> connection on the back of the KXPA100 with no change.I've also
>> re-tuned all bands from 10-40 meters with my LDG100 remote tuner and
>> the highest SWR I receive is 1.4:1 on 30 and 40 meters. All of the
>> other bands are 1:1 to 1.2:1, so I don't think I'm getting any power
>> foldback because of high SWR.. Does anyone have any thoughts on
>> what's causing this differential, and if two power output meters are
>> never going to be in sync, which meter is the most accurate?
>> Also, as an aside. Is there something wrong with the KX3 group from
>> Yahoo? I haven't recieved a digest in days and when I try to get into
>> the group I get an error message
>> Thanks,Jim W7JHR
>> ______________________________________________________________
>> 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
>> Message delivered to [hidden email]
>>
> ______________________________________________________________
> 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
> Message delivered to [hidden email]

Bob McGraw - K4TAX

Re: KX3/KXPA100 Power Output Difference

In reply to this post by Don Wilhelm

And "hamfest" Bird slugs have been found to notoriously be in error.
{if they work at all} And remember, the Bird meter is a voltage
sensing instrument and any impedance deviation from the calibrated
value, normally 50 ohms, will introduce an error in the reading.

73

Bob, K4TAX

On 12/2/2017 9:01 PM, Ron D'Eau Claire wrote:

> A 20% error is not at all unusual in commercial wattmeters either. The famous "Bird" units are only accurate to 5% of full scale. That means that if you are reading 1/2 scale the accuracy is only 10% and only 20% as 1/4 scale. Since Hams tend not to buy all the slugs needed to ensure their meters read near full scale for every measurement, and do not have the slugs professionally calibrated at regular intervals (1 year or so), 20% is a pretty optimistic accuracy at almost every power level.
>
> 73, Ron AC7AC
>
> -----Original Message-----
> From: [hidden email] [mailto:[hidden email]] On Behalf Of Don Wilhelm
> Sent: Friday, December 1, 2017 8:24 PM
> To: Jim Ruff; [hidden email]
> Subject: Re: [Elecraft] KX3/KXPA100 Power Output Difference
>
> Jim,
>
> Amateur wattmeters are notoriously "famous" for their inaccuracies.
> Errors of up to 20% are not unusual, and in many cases it depends on the band because the voltage produced by the measurement diodes are frequency dependent.
>
> So bottom line, don't worry about the 10 watt differential. You are like the man with two watches who does not really know what time it is!
>
> On the KX3 Yahoo Group question, I receive individual emails (not the digest), but something has happened, and I cannot post to any of the Yahoo groups that I am subscribed to for the past 2 weeks. I think Yahoo has "gone to the dogs".
>
> 73,
> Don W3FPR
>
> On 12/1/2017 9:33 PM, Jim Ruff via Elecraft wrote:
>> I using a KX3/KXPA100 and I'm noticing that when I'm in TX the RF
>> meter on the rig matches the set power of the rig, but on the KXP100 meter, it shows 10 or more watts less output. Some examples:Rig Amp50w 40w60w 50w70w 60w80w 70w Here is what i've checked so far. The Powerwerx PS is showing 13.8v when receiving and dips to 12.9v when in TX, so I don't believe I have a voltage problem. I've moved the rig's power connection back and forth from the front of the Powerwerx PS to the top power pole connection on the back of the KXPA100 with no change.I've also re-tuned all bands from 10-40 meters with my LDG100 remote tuner and the highest SWR I receive is 1.4:1 on 30 and 40 meters. All of the other bands are 1:1 to 1.2:1, so I don't think I'm getting any power foldback because of high SWR.. Does anyone have any thoughts on what's causing this differential, and if two power output meters are never going to be in sync, which meter is the most accurate?
>> Also, as an aside. Is there something wrong with the KX3 group from
>> Yahoo? I haven't recieved a digest in days and when I try to get into
>> the group I get an error message Thanks,Jim W7JHR
>> ______________________________________________________________
>> 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 Message delivered to
>> [hidden email]
>>
> ______________________________________________________________
> 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 Message delivered to [hidden email]
>
> ______________________________________________________________
> 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
> Message delivered to [hidden email]
>