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Author Topic: Software Pecker  (Read 9425 times)
AD5X
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Posts: 1432




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« Reply #30 on: September 03, 2012, 09:42:54 AM »

... Unless you stop half way through to stuff more tobacco in your pipe and then light it - which I've seen done!

Boy did this bring back memories.  My Elmer W3ITO used to smoke a pipe when I was a young ham in 1964.  I can still remember his Johnson Ranger/Drake 2B, and the smell of the pipe smoke in his shack.  It all seemed to be the perfect combination!

Phil - AD5X
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AD5ZC
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« Reply #31 on: September 03, 2012, 09:45:57 AM »

So much conflicting information out there.

I recently watched a youtube video from Ten Tec where they show how to tune up their amp using cw dits (like a pecker).
http://www.youtube.com/watch?v=6sV_4e7AEBM&feature=player_embedded#!

What seems telling to me is at the end, to get it right, he uses full key down because using dits had the grid current too high.

So, if I'm seeing this right, pulsing seems helpful initially to get it close so that your not full key down on some really out of tune settings?  After that though, you should know where your amp is close so...  Since it is the peaks that matter just use a straight cw tone?  

I can't tell you how many times I've read that if you don't use a pecker or some other type of pulsed tuning to tune your amp for SSB that your underloaded.
« Last Edit: September 03, 2012, 09:48:58 AM by AD5ZC » Logged
K0IZ
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Posts: 737




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« Reply #32 on: September 03, 2012, 10:06:58 AM »

I have always tried to be gentle with my equipment, and the pecker device (or pulsed CW), allows for tune up to PEP while average tube dissipation is very modest.  As some have pointed out, it is imperative that an amp be tuned up to the full PEP (or key down CW) level.  A pulsed CW is at that point, as is a pulsed audio (ie pecker).  Tuning up at a lesser PEP/CW point, and then operating at a higher power will cause operation at a mismatched point.  I enjoyed this discussion.
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W8JI
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« Reply #33 on: September 03, 2012, 02:54:49 PM »

So much conflicting information out there.

I recently watched a youtube video from Ten Tec where they show how to tune up their amp using cw dits (like a pecker).
http://www.youtube.com/watch?v=6sV_4e7AEBM&feature=player_embedded#!

What seems telling to me is at the end, to get it right, he uses full key down because using dits had the grid current too high.

So, if I'm seeing this right, pulsing seems helpful initially to get it close so that your not full key down on some really out of tune settings?

Here is the problem.........no one can be sure how close it gets things. :-)

The goal in tuning is to establish the correct operating load impedance seen by the PA device. The optimum load impedance value decreases as drive and output power levels increase. This means we need to always do the final tuning step at full drive power if we have a fixed supply voltage. We CAN tune at lower voltage at full drive power, if the system allows it, because a linear stage should increase current and voltage in about the same proportion.

One almost daily problem with customers is tuning at low power, and then changing something to cause more power to appear. Like tuning on AM at 25 watts driver carrier and then talking on AM, or tuning at 50 watts and then going to 100 watts PEP drive. Since many or most radios have loop delay in the power control systems, there is often some leading edge overshoot at the start of transmissions.

An audio pulsed tone solves absolutely nothing that cannot also be solved with dots because, within frequency response of modulation systems, the RF product is identical. The simple goal is to have peaks at maximum power, and have meters respond in a useful way.

Since a grid meter is the single most useful meter indicator of proper operation, we really should check the grid meter as a final tuning step with full drive power.

Quote
After that though, you should know where your amp is close so...  Since it is the peaks that matter just use a straight cw tone? 


CW PEP= CW average for steady carrier

So a CW carrier is also PEP at the same level. :-) The only thing the dots or pulsed audio does in reduce duty cycle and heat.

Quote
I can't tell you how many times I've read that if you don't use a pecker or some other type of pulsed tuning to tune your amp for SSB that your underloaded.

I wonder why people say that? I suppose people who have a tough time managing tuning and melt tubes down could use a pulser, but that is a heat problem. IMO using a pulser either keeps things the same or increases the chances of mistuning. I can't see why it would make things better.

Maybe someone can explain why it would make things better.

73 Tom
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G3RZP
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« Reply #34 on: September 04, 2012, 01:28:20 AM »

Tom,

>Maybe someone can explain why it would make things better.<

I certainly can't.
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W1QJ
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Posts: 1460




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« Reply #35 on: September 04, 2012, 05:27:07 AM »

Tom,

>Maybe someone can explain why it would make things better.<

I certainly can't.
Well, how about this possibility?  Many people who load up amps are anal and they might say something like this because "technically" if you load up an amp with a dead carrier and maximum drive level the power supply voltage will sag and you will be loading the amp at a lower degree than a peak in an SSB waveform.  So by a small percentage the SSB peak would appear at an under loaded tank value unless, one tends to compensate for that by slightly over coupling as a last adjustment.  Some purists would seem to think that pulser loading would be more accurate to compensate for the sag in PS voltage/current.  You'd have to use a scope and look at the wave forms of each loading method and see if you can detect one being better than another.
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W8JI
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« Reply #36 on: September 04, 2012, 06:31:07 AM »

Tom,

>Maybe someone can explain why it would make things better.<

I certainly can't.
Well, how about this possibility?  Many people who load up amps are anal and they might say something like this because "technically" if you load up an amp with a dead carrier and maximum drive level the power supply voltage will sag and you will be loading the amp at a lower degree than a peak in an SSB waveform.  So by a small percentage the SSB peak would appear at an under loaded tank value unless, one tends to compensate for that by slightly over coupling as a last adjustment. 


Actually the PA tube pretty much behaves as a linear resistance around the operating voltage range. If you reduce voltage, you reduce current by a similar amount. E/I, or the optimal load impedance, remains the same.

This is why the SB-220 Heath and some other amps told people to tune on the low voltage CW settings, and then just flip to SSB where voltage was greatly increased. This means that argument either falls totally apart, or Heathkit and others were wrong.

Quote
Some purists would seem to think that pulser loading would be more accurate to compensate for the sag in PS voltage/current.  You'd have to use a scope and look at the wave forms of each loading method and see if you can detect one being better than another.

I've heard that before. It doesn't seem to be a valid argument until HV is changed so much that tube conduction angle significantly changes.

Overcoupling is not a compensation for small HV changes, which simply increase current and voltage in the same proportion with optimum load impedance remaining the same.  Overcoupling really just prepares the system for occasional exciter overshoot, and also adds a little more negative feedback in grounded grid stages.

The linear ALS600 supply, for example, changes drain voltage from around 50 volts to around 30-35 volts in the ALS600. This maintains efficiency at reduced power for RTTY and FM, because optimum load impedance remains the same.

I think people selling tuning pulsers got off on the wrong track by accepting early articles as accurate. They do go well with nichrome suppressors, and antennas that radiate from voltage and electric fields.   :-)

73 Tom   
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N3QE
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« Reply #37 on: September 04, 2012, 07:11:41 AM »

This is why the SB-220 Heath and some other amps told people to tune on the low voltage CW settings, and then just flip to SSB where voltage was greatly increased. This means that argument either falls totally apart, or Heathkit and others were wrong.

Different folks have different expectations for "correctly tuned". Lots of people grew up expecting every digit on a 8 digit calculator to be correct. Look at the detailed spectrum analysis the other guys sent you of the audio output of the pecker for the "typical pecker user expectation" of precision vs irrelevance.
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W8JI
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« Reply #38 on: September 04, 2012, 03:31:53 PM »

Different folks have different expectations for "correctly tuned". Lots of people grew up expecting every digit on a 8 digit calculator to be correct. Look at the detailed spectrum analysis the other guys sent you of the audio output of the pecker for the "typical pecker user expectation" of precision vs irrelevance.

This is one of the best threads in a long time for improving customer understanding of how the system works. I've seen a few cases where people confuse the spectrum of audio with the spectrum of RF, and envelope peak or average power with peak or RMS power.

This whole thing developed into a copied and re-copied solution without a firm grasp of the problem.
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K5USF
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Posts: 83




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« Reply #39 on: December 11, 2012, 07:22:02 PM »

Ok, I have been busy lately so I thought I would revisit this, albeit for a short time.  I fired up the amp on 20m (into a dumb sh$% load) and tried the pecker using the W8JI pulsar method.  Used my 746pro and a signalink usb.  The software amplitude setting was 100 and the frequency was 35.  The results were very close to my RTTY mode amp settings.  The load setting was higher with the RTTY tuning approach.  Say 4 versus 3.8.  Using the pecker at 100 amplitude with the 746pro on SSB mode, the most I could get for drive was 70 watts (this could be a win 7 audio setting issue - will investigate).

This is what I want:  a step by step procedure for tuning an amp with the software pecker.  I could not find this-except for the W8JI hardware pulsar procedure.   IMHO, you need some good amp tuning procedures for the software pecker.  Can't assume everyone has used a pecker.

I may have been trying to use the software with inadequate drive levels.  Thanks!  73s Jim

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