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Author Topic: Amplifier output and antenna tuner issues  (Read 11659 times)
WX7G
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« Reply #30 on: September 15, 2012, 12:50:53 PM »

The focus still seems (erroneously) to be on the THP amp while the problem appears to be the Palstar tuner.
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W5WSS
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« Reply #31 on: September 15, 2012, 03:37:03 PM »

Yes I got side tracked clarifying the other part but yes I think the issue can be the inaccuracy of the meter in the Palstar tuner but that can easily be verified and then corrected.
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WA9UAA
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Posts: 311




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« Reply #32 on: September 15, 2012, 09:18:40 PM »

Good Day,
The only way I can verify, seriously, is to compare the other meter readings. I have an older Palstar mobile watt meter with a 2KW full scale. It agrees with the THP meter on the amplifier easily +/- 10 % I'd say. I got into a qso on 75 meters a couple of days ago, mentioned the problem and while I also got a bunch of suggestions as to enhancing the audio one fellow looked at the signal on his scope, saw a trapezoid pattern and said it was clean. If I have a spur somewhere else that not going to be detectable. I wouldn't be surprised to find one in any case. The question would be what does it measure in dBc.

I've got a lightning ground outside the shack that is connected to the house ground at the meter. There are 4 ground rods between the ends of the ground system with the lightning ground at one end. What bothers me about grounding the station is that any large strike dumped into the ground is going to light up the equipment to the same potential abet for a short time. The house ground being 30 some feet away may be enough delay to still develop some nasty potential difference in the shack. BTW, The amp is wired split 220 so it's chassis is grounded via the neutral. (I hope) So, are my grounding concerns valid? What else can I do to verify that the amp is clean. Again, thanks to all for the concern, help and suggestions.
73,
Rob WA9UAA 
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KC4MOP
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Posts: 729




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« Reply #33 on: September 16, 2012, 04:30:02 AM »

Good Day,
The only way I can verify, seriously, is to compare the other meter readings. I have an older Palstar mobile watt meter with a 2KW full scale. It agrees with the THP meter on the amplifier easily +/- 10 % I'd say. I got into a qso on 75 meters a couple of days ago, mentioned the problem and while I also got a bunch of suggestions as to enhancing the audio one fellow looked at the signal on his scope, saw a trapezoid pattern and said it was clean. If I have a spur somewhere else that not going to be detectable. I wouldn't be surprised to find one in any case. The question would be what does it measure in dBc.

I've got a lightning ground outside the shack that is connected to the house ground at the meter. There are 4 ground rods between the ends of the ground system with the lightning ground at one end. What bothers me about grounding the station is that any large strike dumped into the ground is going to light up the equipment to the same potential abet for a short time. The house ground being 30 some feet away may be enough delay to still develop some nasty potential difference in the shack. BTW, The amp is wired split 220 so it's chassis is grounded via the neutral. (I hope) So, are my grounding concerns valid? What else can I do to verify that the amp is clean. Again, thanks to all for the concern, help and suggestions.
73,
Rob WA9UAA 
Hey Rob
You posted this a couple of pages ago.
How can someone, in a QSO, be able to analyze your signal looking at a trapezoid pattern? That measurement is done at the transmitting end.
This is a link to a commercially made product, but it explains the process:

http://www.icycolors.com/nu9n/scope_your_audio.html

And grounding your station will not do anything for RFI or common mode problems. There must be a problem with imbalance in your RF system that currents are getting back into the amp., which seems susceptible to CM.
And I think you are on the path of discovery that the Palstar watt meter in the tuner is inaccurate. Your Palstar mobile watt meter is agreeing with the amp's metering somewhat.
Put off the temptation to enhance your SSB audio until you get these other problems settled. The extra range of audio for hi-fi SSB may send that amp to its grave.

Fred
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W8JI
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« Reply #34 on: September 16, 2012, 05:09:32 AM »

Good Day,
The only way I can verify, seriously, is to compare the other meter readings. I have an older Palstar mobile watt meter with a 2KW full scale. It agrees with the THP meter on the amplifier easily +/- 10 % I'd say.

This issue is much different than absolute power.

The issue, if there is one, could be reflected power null settings on the tuner compared to other meters. It does not matter if the meters are all 50% off from actual real power. What matters is if they consistently behave the same in relationsip to each other as impedance changes.


Quote
I got into a qso on 75 meters a couple of days ago, mentioned the problem and while I also got a bunch of suggestions as to enhancing the audio one fellow looked at the signal on his scope, saw a trapezoid pattern and said it was clean. If I have a spur somewhere else that not going to be detectable. I wouldn't be surprised to find one in any case. The question would be what does it measure in dBc.


This shows why we have to be very careful soliciting help!!!

The person handing out those tests, while having good motives, is wasting a great deal of time and misleading people. It is impossible, at the receiver end of a system, to make a trapezoid linearity test and pronouce someone else's signal clean.

To make a trapezoid test, one axis has to be at a stage or system input and the other axis at a stage or system output. He cannot possibly have access to that from his house, so his test is clearly meaningless.

You should politely but formly tell him that, so he quites misleading people over the air. He is claiming he is checking things he cannot possibly be checking.

Whatever pretty display he is looking at cannot possibly be measuring spurious, linearity, or distortion of your transmitter.

Quote
I've got a lightning ground outside the shack that is connected to the house ground at the meter. There are 4 ground rods between the ends of the ground system with the lightning ground at one end. What bothers me about grounding the station is that any large strike dumped into the ground is going to light up the equipment to the same potential abet for a short time. The house ground being 30 some feet away may be enough delay to still develop some nasty potential difference in the shack. BTW, The amp is wired split 220 so it's chassis is grounded via the neutral. (I hope) So, are my grounding concerns valid? What else can I do to verify that the amp is clean. Again, thanks to all for the concern, help and suggestions.

I would figure out where and what the problem is as a starting point.

Changing things that are not the problem until we stumble on a positive change does not always fix the actual problem.

There are logical procedures for locating the source of problems.

73 Tom

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WA9UAA
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Posts: 311




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« Reply #35 on: September 17, 2012, 10:53:08 AM »

Thanks for the updates, I understand that the band aid fixes don't get rid of the problem. Would substituting another power meter/ tuner-metering-system lead to some sort of verification of whether or not the amplifier is faulty, depending upon how it behaves? 
73,
Rob WA9UAA
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W8JI
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« Reply #36 on: September 17, 2012, 04:54:54 PM »

Thanks for the updates, I understand that the band aid fixes don't get rid of the problem. Would substituting another power meter/ tuner-metering-system lead to some sort of verification of whether or not the amplifier is faulty, depending upon how it behaves? 
73,
Rob WA9UAA

Rob,

This has gone on so long I can't easily put together all the clues. I do hope you told the guy giving trapezoid reports they are meaningless on a SSB receiver. X axis compared to Y axis will always be linear if taken from the same point. :-)

I'm not sure what the problem is or even if you have a problem at this point.

You could just have a meter or meters out of calibration, or it could be an amplfier problem. I'm sorry I can't be more help.

Apparently you have three meters, the tuner meter, an external mobile meter, and a meter in the amplifier. Did I miss one?

Connect all the meters in line and run into the dummy load and make sure SWR is 1:1 on all meters. What is the power on all meters just into the dummy load with a 1:1 SWR? ?



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N4BCD
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Posts: 8




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« Reply #37 on: September 18, 2012, 05:50:30 AM »

W8JI's suggested test of all your meters in-line into a dummy load should be done. 

I used that test to identify a faulty dummy load (reactive) so the amp was not loaded into 50 ohms.  When switching from the dummy load to a tuner fed antenna (that was nulled at low power using the exiter SWR meter) my power was way off.

73, Mark
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WA9UAA
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Posts: 311




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« Reply #38 on: September 18, 2012, 06:51:09 AM »

Here you go, all readings through the tuner into the DL with the tuner tuned to 1:1 SWR

Frequency                3550 KHz                    3950 KHz
THP Meter                 600W........................600W
Palstar Mobile meter  650W........................675W
Palstar Tuner meter   600W........................550W

Thanks and 73,
Rob WA9UAA
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KC4MOP
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Posts: 729




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« Reply #39 on: September 18, 2012, 04:34:03 PM »

Here you go, all readings through the tuner into the DL with the tuner tuned to 1:1 SWR

Frequency                3550 KHz                    3950 KHz
THP Meter                 600W........................600W
Palstar Mobile meter  650W........................675W
Palstar Tuner meter   600W........................550W

Thanks and 73,
Rob WA9UAA

whoa! Hold up a minute here....Can you put the tuner in bypass?? And let's see theses readings with the tuner in bypass, not tuned for 1:1. A DL should not need any tuner influence.

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W8JI
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« Reply #40 on: September 18, 2012, 05:08:06 PM »

If you have a good load, the tuner should NOT be needed to adjust SWR.

Do ALL three meters say 1:1 SWR? If they read SWR, what do the ones that read SWR say the SWR is?

Are your coaxial cables all good?
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WA9UAA
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« Reply #41 on: September 19, 2012, 06:34:40 AM »

Hi All,
In checking the power through then tuner I made the adjustments as the setting for one end of the band was not the same as the other.  With the THP meter I am simply reading forward power. Here are the readings with the tuner in the bypass position.

Frequency     3550 KHz                               3950 KHz
THP meter     580 W...................................590 W
Mobile meter 610 W....................................610W
Tuner meter  600 W....................................590W

The Palstar meters are cross needle type, in each case with the above readings (today) the reflected power was ~~ 1/2 watt.
73,
Rob
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W8JI
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« Reply #42 on: September 19, 2012, 08:05:58 AM »

It seems to me there is no problem, except perhaps with tuner settings not being to the null settings on meters.
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WA9UAA
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« Reply #43 on: September 19, 2012, 09:55:53 AM »

Thanks Tom and all who contributed, I appreciate the time spent.
73,
Rob WA9UAA
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KC9TNH
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« Reply #44 on: September 20, 2012, 01:13:25 PM »

This has been an interesting read. (A slight deviation at lower power exacerbated with the amp sounded familiar.)
Although only an anklebiter barefoot, the difference on my Palstar AT2K's meters was notable once the AL-80B was up & running - the AL-80B agreeing with 3 other owned/borrowed meters incl one "borrowed overnight" from the nearby calibration shop. So to rid the irritant I used pg. 16 in the AT2K's manual and did a very slight adjustment. The term "slight" is relative since the adjustments interact and doesn't mean it only takes a couple seconds; it takes time to do right and the adjustments are very twitchy. But my AT2K also displayed some slight metering issue, now fixed. But it can happen. As much as I love the thing, it's man-made.

Certainly not in the league of the OP's amp, a little THP SS 45w companion amp for my FT817 is pretty finicky and is always a good check to see if there's any common-mode gremlins around.  (The old AL-80B on the other hand is just a happy Clydesdale.)
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73
Wes -KC9TNH
"Don't get treed by a chihuahua." - Pete
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