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New P3 TX Monitor....unusual behavior with SWR (at times)

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Phil Hystad-3

New P3 TX Monitor....unusual behavior with SWR (at times)

Does this happy to anyone else with the new TX Monitor…?

My TX monitor sensor sits between my KPA500 and the KAT500 and since I have installed it and had it up and running I have had more than my average spurts of high SWR. For example, a key down may cause this spurt but just a moment later the SWR is fine at is usual 1.4:1 or so for this particular antenna. I have only noticed this on 80-meter band and I have my KAT500 fully programmed for each segment and also I run the KAT500 in manual mode.

I only see this on CW but that is the only thing I have done since having the TX monitor set up except for one time of saying “test, test, test” into the mic to see the TX SSB waveform.

Usually, I don’t have any hassles with high SWR spurts on this antenna with the KAT500 and that is why I am thinking there may be some new kind of interference with the sensor in line like maybe brief periods where the Load side which is input to KAT500 does not look like 50 ohms.

Thanks for your comments.

73, phil, K7PEH

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Mike VE3YF

Re: New P3 TX Monitor....unusual behavior with SWR (at times)

Phil:

I have the same setup but only 1 x P3. A K3 and P3 on my left setup
and a K3 on the right setup using a MK2R+ and I noticed what you
mention only once. I was on 80m with
the Right K3 and I saw a brief Power and SWR spike on the Left P3 and
K3. I might have had a bit of SWR on the standalone Right K3. I have
not noticed it happen since, it might
be a band/swr specific issue ie, as I was operating around 3800 and
the antenna is designed for the CW and RTTY portion of the band. The
Left side radio was on 160m Sloper

73 De Mike
VE3YF

http://www.ve3yf.com
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Phil Hystad-3

Re: New P3 TX Monitor....unusual behavior with SWR (at times)

In reply to this post by Phil Hystad-3

Mike,

Thanks for the comment. I only have one K3 with one P3. My configuration is:

K3/P3 —> KPA500 —> TX Mon Sensor —> LP100A Sensor —> KAT500 —> 80-meter Dipole

I first noticed the spike with the RED LEDs on both the KAT500 and the KPA500. I was not looking
at the SWR display on the P3 although the second time I did notice that it too spiked (max reading).

Like I said, I was operating CW and when I sent just the first dit of a QNI into a CW net the spike occurred.
I stopped, and then keyed again and everything was normal. The second time that I did this, I thought that
maybe the spike was momentary and continued keying but the second or third key down action (actually, a paddle)
resulted in fault with the KPA500.

Last night, I did not have any problems at all because I disconnected the TX Mon sensor. I will continue
experimenting though as I don’t have too many data points yet to draw conclusions.

73, phil, K7PEH

> On Aug 12, 2015, at 7:28 AM, Mike VE3YF <[hidden email]> wrote:
>
> Phil:
>
> I have the same setup but only 1 x P3. A K3 and P3 on my left setup and a K3 on the right setup using a MK2R+ and I noticed what you mention only once. I was on 80m with
> the Right K3 and I saw a brief Power and SWR spike on the Left P3 and K3. I might have had a bit of SWR on the standalone Right K3. I have not noticed it happen since, it might
> be a band/swr specific issue ie, as I was operating around 3800 and the antenna is designed for the CW and RTTY portion of the band. The Left side radio was on 160m Sloper
>
>
>
>
> 73 De Mike
> VE3YF
>
> http://www.ve3yf.com
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
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> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]

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w8fn

Re: New P3 TX Monitor....unusual behavior with SWR (at times)

I find this thread quite interesting. I too have been dealing with VSWR
"spurts". My TX lineup is similar to Phil's, but I don't have the TX
Monitor. After a recent station rewiring job I found I was having a
great deal of trouble with indicated VSWR jumping to high levels with
the amplifier on. The problem was especially bad on 80 meters --
anything above about 300W would randomly give a high VSWR fault on the
KAT500. Since the KPA500 was feeding the suddenly changed load it too
would usually fault out. The sensor for my LP-100A is on the antenna
side of the KAT500, and its VSWR indication was rock solid during these
events. My station is in an extremely difficult RFI environment, with
seven antennas crammed onto a 0.2 acre city lot. I immediately suspected
that common mode RF was getting into the reverse power sensor circuit in
the KAT500.

I installed a Balun Designs choke on the antenna side of the LP-100A
sensor and the KAT500 stopped giving the high VSWR indications right
away. That's the good news. The bad news is that now the KPA500 is doing
it, but at considerably higher power levels. I can run around 400W out
before the KPA500 begins to randomly show VSWR faults. The KAT500 is
completely stable at full power. For now, I'm living with this situation.

So I would suggest the troubles you're seeing may be the result of
common mode RF problems on the transmitter feedline. It could be that
the addition of the extra electrical length of the TX Monitor sensor and
its associated cabling changed things just enough to put a common mode
voltage node near the KAT500 output port. You might try adding an
additional piece of coax somewhere in the lineup and see if that changes
the situation. RF is funny stuff.

73...
Randy, W8FN

On 8/12/2015 10:10 AM, Phil Hystad wrote:

> Mike,
>
> Thanks for the comment. I only have one K3 with one P3. My configuration is:
>
> K3/P3 —> KPA500 —> TX Mon Sensor —> LP100A Sensor —> KAT500 —> 80-meter Dipole
>
> I first noticed the spike with the RED LEDs on both the KAT500 and the KPA500. I was not looking
> at the SWR display on the P3 although the second time I did notice that it too spiked (max reading).
>
> Like I said, I was operating CW and when I sent just the first dit of a QNI into a CW net the spike occurred.
> I stopped, and then keyed again and everything was normal. The second time that I did this, I thought that
> maybe the spike was momentary and continued keying but the second or third key down action (actually, a paddle)
> resulted in fault with the KPA500.
>
> Last night, I did not have any problems at all because I disconnected the TX Mon sensor. I will continue
> experimenting though as I don’t have too many data points yet to draw conclusions.
>
> 73, phil, K7PEH
>
>
>
>
>> On Aug 12, 2015, at 7:28 AM, Mike VE3YF <[hidden email]> wrote:
>>
>> Phil:
>>
>> I have the same setup but only 1 x P3. A K3 and P3 on my left setup and a K3 on the right setup using a MK2R+ and I noticed what you mention only once. I was on 80m with
>> the Right K3 and I saw a brief Power and SWR spike on the Left P3 and K3. I might have had a bit of SWR on the standalone Right K3. I have not noticed it happen since, it might
>> be a band/swr specific issue ie, as I was operating around 3800 and the antenna is designed for the CW and RTTY portion of the band. The Left side radio was on 160m Sloper
>>
>>
>>
>>
>> 73 De Mike
>> VE3YF
>>
>> http://www.ve3yf.com

Phil Hystad-3

Re: New P3 TX Monitor....unusual behavior with SWR (at times)

Randy,

If your LP100A is on the antenna side of your KAT500 then you are putting your LP100A in the region of higher SWR if your antenna is not close to resonance. I think you would want to put your LP100A in the inboard side of the KAT500 so that you are properly showing the “tuned” SWR on the LPA100A and your readings will be more accurate I believe.

If you want to know the antenna side of the SWR, what the KAT500 refers to as the Bypass SWR since it is the SWR you see if you bypass the KAT500, then you can use the KAT500 utility program to display that.

I am not seeing the problems you describe. For example, when I run without the TX Mon Sensor in place, there are absolutely no SWR problems at all (look again at the configuration below that I have). I should also note that today I did not see any problems with the SWR spurts I originally reported even with the TX Monitor sensor inline.

73, phil, K7PEH

> On Aug 12, 2015, at 7:48 PM, Randy Farmer <[hidden email]> wrote:
>
> I find this thread quite interesting. I too have been dealing with VSWR "spurts". My TX lineup is similar to Phil's, but I don't have the TX Monitor. After a recent station rewiring job I found I was having a great deal of trouble with indicated VSWR jumping to high levels with the amplifier on. The problem was especially bad on 80 meters -- anything above about 300W would randomly give a high VSWR fault on the KAT500. Since the KPA500 was feeding the suddenly changed load it too would usually fault out. The sensor for my LP-100A is on the antenna side of the KAT500, and its VSWR indication was rock solid during these events. My station is in an extremely difficult RFI environment, with seven antennas crammed onto a 0.2 acre city lot. I immediately suspected that common mode RF was getting into the reverse power sensor circuit in the KAT500.
>
> I installed a Balun Designs choke on the antenna side of the LP-100A sensor and the KAT500 stopped giving the high VSWR indications right away. That's the good news. The bad news is that now the KPA500 is doing it, but at considerably higher power levels. I can run around 400W out before the KPA500 begins to randomly show VSWR faults. The KAT500 is completely stable at full power. For now, I'm living with this situation.
>
> So I would suggest the troubles you're seeing may be the result of common mode RF problems on the transmitter feedline. It could be that the addition of the extra electrical length of the TX Monitor sensor and its associated cabling changed things just enough to put a common mode voltage node near the KAT500 output port. You might try adding an additional piece of coax somewhere in the lineup and see if that changes the situation. RF is funny stuff.
>
> 73...
> Randy, W8FN
>
> On 8/12/2015 10:10 AM, Phil Hystad wrote:
>> Mike,
>>
>> Thanks for the comment. I only have one K3 with one P3. My configuration is:
>>
>> K3/P3 —> KPA500 —> TX Mon Sensor —> LP100A Sensor —> KAT500 —> 80-meter Dipole
>>
>> I first noticed the spike with the RED LEDs on both the KAT500 and the KPA500. I was not looking
>> at the SWR display on the P3 although the second time I did notice that it too spiked (max reading).
>>
>> Like I said, I was operating CW and when I sent just the first dit of a QNI into a CW net the spike occurred.
>> I stopped, and then keyed again and everything was normal. The second time that I did this, I thought that
>> maybe the spike was momentary and continued keying but the second or third key down action (actually, a paddle)
>> resulted in fault with the KPA500.
>>
>> Last night, I did not have any problems at all because I disconnected the TX Mon sensor. I will continue
>> experimenting though as I don’t have too many data points yet to draw conclusions.
>>
>> 73, phil, K7PEH
>>
>>
>>
>>
>>> On Aug 12, 2015, at 7:28 AM, Mike VE3YF <[hidden email]> wrote:
>>>
>>> Phil:
>>>
>>> I have the same setup but only 1 x P3. A K3 and P3 on my left setup and a K3 on the right setup using a MK2R+ and I noticed what you mention only once. I was on 80m with
>>> the Right K3 and I saw a brief Power and SWR spike on the Left P3 and K3. I might have had a bit of SWR on the standalone Right K3. I have not noticed it happen since, it might
>>> be a band/swr specific issue ie, as I was operating around 3800 and the antenna is designed for the CW and RTTY portion of the band. The Left side radio was on 160m Sloper
>>>
>>>
>>>
>>>
>>> 73 De Mike
>>> VE3YF
>>>
>>> http://www.ve3yf.com
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
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> Please help support this email list: http://www.qsl.net/donate.html
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Jessie Oberreuter-2

Re: New P3 TX Monitor....unusual behavior with SWR (at times)

In reply to this post by w8fn

I had a similar problem -- even at low power levels, the W2 would
periodically spike a high-SWR and even show 2-3 bars of SWR when no signal
was present. I swapped out the 8-pin cable connecting the sensor to the
W2 and the problem went away. I re-crimped the connectors on the original
cable, but haven't yet swapped it back in to see if doing so fixed the
problem.

On Wed, 12 Aug 2015, Randy Farmer wrote:

> I find this thread quite interesting. I too have been dealing with VSWR
> "spurts". My TX lineup is similar to Phil's, but I don't have the TX
> Monitor. After a recent station rewiring job I found I was having a
> great deal of trouble with indicated VSWR jumping to high levels with
> the amplifier on. The problem was especially bad on 80 meters --
> anything above about 300W would randomly give a high VSWR fault on the
> KAT500. Since the KPA500 was feeding the suddenly changed load it too
> would usually fault out. The sensor for my LP-100A is on the antenna
> side of the KAT500, and its VSWR indication was rock solid during these
> events. My station is in an extremely difficult RFI environment, with
> seven antennas crammed onto a 0.2 acre city lot. I immediately suspected
> that common mode RF was getting into the reverse power sensor circuit in
> the KAT500.
>
> I installed a Balun Designs choke on the antenna side of the LP-100A
> sensor and the KAT500 stopped giving the high VSWR indications right
> away. That's the good news. The bad news is that now the KPA500 is doing
> it, but at considerably higher power levels. I can run around 400W out
> before the KPA500 begins to randomly show VSWR faults. The KAT500 is
> completely stable at full power. For now, I'm living with this situation.
>
> So I would suggest the troubles you're seeing may be the result of
> common mode RF problems on the transmitter feedline. It could be that
> the addition of the extra electrical length of the TX Monitor sensor and
> its associated cabling changed things just enough to put a common mode
> voltage node near the KAT500 output port. You might try adding an
> additional piece of coax somewhere in the lineup and see if that changes
> the situation. RF is funny stuff.
>
> 73...
> Randy, W8FN
>
> On 8/12/2015 10:10 AM, Phil Hystad wrote:
>> Mike,
>>
>> Thanks for the comment. I only have one K3 with one P3. My configuration
> is:
>>
>> K3/P3 —> KPA500 —> TX Mon Sensor —> LP100A Sensor —> KAT500 —>
> 80-meter Dipole
>>
>> I first noticed the spike with the RED LEDs on both the KAT500 and the
> KPA500. I was not looking
>> at the SWR display on the P3 although the second time I did notice that it
> too spiked (max reading).
>>
>> Like I said, I was operating CW and when I sent just the first dit of a QNI
> into a CW net the spike occurred.
>> I stopped, and then keyed again and everything was normal. The second time
> that I did this, I thought that
>> maybe the spike was momentary and continued keying but the second or third
> key down action (actually, a paddle)
>> resulted in fault with the KPA500.
>>
>> Last night, I did not have any problems at all because I disconnected the
> TX Mon sensor. I will continue
>> experimenting though as I don’t have too many data points yet to draw
> conclusions.
>>
>> 73, phil, K7PEH
>>
>>
>>
>>
>>> On Aug 12, 2015, at 7:28 AM, Mike VE3YF <[hidden email]> wrote:
>>>
>>> Phil:
>>>
>>> I have the same setup but only 1 x P3. A K3 and P3 on my left setup and a
> K3 on the right setup using a MK2R+ and I noticed what you mention only once.
> I was on 80m with
>>> the Right K3 and I saw a brief Power and SWR spike on the Left P3 and K3.
> I might have had a bit of SWR on the standalone Right K3. I have not noticed
> it happen since, it might
>>> be a band/swr specific issue ie, as I was operating around 3800 and the
> antenna is designed for the CW and RTTY portion of the band. The Left side
> radio was on 160m Sloper
>>>
>>>
>>>
>>>
>>> 73 De Mike
>>> VE3YF
>>>
>>> http://www.ve3yf.com
>
> ______________________________________________________________
> 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]

w8fn

Re: New P3 TX Monitor....unusual behavior with SWR (at times)

In reply to this post by Phil Hystad-3

Having the LP-100A on the antenna side is by design. I'm not much
interested in monitoring the antenna VSWR in real time, but I do want to
know the power being delivered at the tail end of the station RF lineup.
The "light show" on the KAT500 and the KPA500 (if it's being used) as
well as the internal indication in the K3 gives plenty of redundant
information about whether or not the antenna tuner is doing its job. The
unique vector measurement capability of the LPA-100A also makes it good
for maintenance checks. I periodically run the utility program to have
the LPA-100A measure the various antennas across their operational bands
and compare the results against historical data. This lets me see any
changes that might have occurred -- these changes would be masked by an
antenna tuner between the LPA-100A sensor and the actual antenna.

I actually use the KAT500 almost exclusively for tuning my 80 meter
inverted L, which is too long electrically but mechanically impossible
to tune properly. Although all my other antennas are resonant on their
respective operating bands I also leave the KAT500 on line to use as a
"line flattener" on 160 and 40 meters if I should operate outside of the
normal CW bands these antennas are tuned for.

73...
Randy, W8FN

On 8/13/2015 12:30 AM, Phil Hystad wrote:
> Randy,
>
> If your LP100A is on the antenna side of your KAT500 then you are putting your LP100A in the region of higher SWR if your antenna is not close to resonance. I think you would want to put your LP100A in the inboard side of the KAT500 so that you are properly showing the “tuned” SWR on the LPA100A and your readings will be more accurate I believe.
>
> If you want to know the antenna side of the SWR, what the KAT500 refers to as the Bypass SWR since it is the SWR you see if you bypass the KAT500, then you can use the KAT500 utility program to display that.
>
> I am not seeing the problems you describe. For example, when I run without the TX Mon Sensor in place, there are absolutely no SWR problems at all (look again at the configuration below that I have). I should also note that today I did not see any problems with the SWR spurts I originally reported even with the TX Monitor sensor inline.
>
> 73, phil, K7PEH

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