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Author Topic: 30L-1 RF INPUT CABLE  (Read 27877 times)
KH6AQ
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« Reply #30 on: July 20, 2016, 06:26:13 AM »

The "...lack of unregulated screen voltage..." was mentioned. The amp uses triodes - no screens here.
« Last Edit: July 20, 2016, 06:29:46 AM by WX7G » Logged
W9NVN
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« Reply #31 on: July 20, 2016, 08:13:29 AM »

The "...lack of unregulated screen voltage..." was mentioned. The amp uses triodes - no screens here.
WX7G,The reference to the screen voltage I made was for the 30S-1 which employs a 4CX1000A Tetrode in the final. I purchased a large supply of surplus NOS 811A
tubes, so I have a life time supply. I traded my Collins 30L-1 for a mint Kenwood TS-830S, so my next amp purchase will be an Ameritron 811H with 4 811a in the final. As I
looked at the design of the AL-811H IMHO, I like the fact that I can use any cable length so this entire thread becomes a non issue with the Ameritron 811H!! Who ever designed it put some thought into it. VY 73 W9NVN
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K9AXN
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« Reply #32 on: July 20, 2016, 08:18:56 AM »

Dave,

I believe Mike was referring to the 30S1 although the conversation was addressing the 30L1.

Regardless --- Mikes comment about the screen not having a regulated power supply is questionable ---- it's grounded.  I believe a grounded grid represents a regulated supply.  

Second comment from Mike regarding design faults (The 30S1 has an under powered fan and later amps were shipped with a 4CX1500 installed) .  That fan was fine for the 4CX1000 but for the 4CX1500, it did not make muster.  If the radio was purchased new from Collins with a 4CX1500 installed along with the under powered fan it came from a knockoff shop in some southeastern Asian archipelago using slaves.  

G-Day and Kindest regards Jim
« Last Edit: July 20, 2016, 09:29:05 AM by K9AXN » Logged
W8JI
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« Reply #33 on: July 20, 2016, 09:56:37 AM »

Personalities have nothing to do with technical accuracy or correctness, or being worthless in all areas because they make a few mistakes. 

Any person who understands basic circuits and amplifiers in detail would instantly know the following:

1.) Feedback between user-adjustable resonant circuits is bad news. Depending on reactance both on the operating frequency and outside the operating frequency range, there can be (and usually is) considerable phase shift. Wrapping feedback around circuits that are tuned is a bad idea. This is why bridge neutralization is that completely cancels unwanted feedback capacitance is good, and "over neutralizing" (an odd term) would be bad. The goal is ZERO feedback so tank phase shift has no effect on feedback phase, because there isn't any feedback.

I think this was the source of many Collins problems with field consistency. For example, the 32S series is PA tube critical (unlike many other radios) and it wraps feedback around the driver and PA.

2.) One length of cable cannot possibly provide a constant phase shift over a very wide frequency range. That claim is obviously wrong.

3.) Using a low value capacitor divider between cathode, grid, and ground does not provide negative feedback. It is also not a linear voltage division with varying grid impedance. That is a false claim that anyone understanding basic circuits should be able to see is false. Negative feedback in broad band resonant tank amplifiers pretty much has to added with a series cathode impedance, so as the tube draws more cathode current the voltage drop across that impedance decreases the G-K voltage. A divider does not do that at all, so the concept a divider provides linear NFB is flawed.
   
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K9AXN
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« Reply #34 on: July 20, 2016, 12:31:33 PM »

Tom,
Here is a film of an UNDER NEUTRALIZED grid driven amplifier.

http://k9axn.com/_mgxroot/img_1323988130_15155_1454557028.avi

The amp is bridge neutralized using the Bruene method.  It is under neutralized and as you see when I vary the plate capacity it remains perfect even though the plate is phase shifting.  When resonance is reached the input and output wave forms perfectly overlap; perfect negative feedback.  In a grid driven amp the plate to grid capacity is NEGATIVE feedback and the neutralizing capacitor provides POSITIVE feedback.

In a grounded grid amp the plate to cathode capacity is POSITIVE feedback and the neutralizing system is NEGATIVE feedback. 

You can achieve the same results by OVER neutralizing a grounded grid amp as opposed to under neutralizing a grid driven amp.  Did you see any instability?  I have other films of the same setup with the antenna disconnected and the plate resonated and of course at very low drive levels --- just enough to generate full ac envelopes and screen current.  I would say that’s more than a fair test of stability.

Please don’t respond with an it won’t work until you test the concept and shoot a video clip.

Kindest regards Jim 


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K9AXN
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« Reply #35 on: July 20, 2016, 05:34:18 PM »

Tom,

Regarding your point 1:
The two stage feedback system used in the 32S and KWM has long been considered the reason for the cable length issue not the 30L1.  Increasing the Q of the input tuned circuits on the 30S1 has been considered a reasonable work around but stability becomes an issue.

Regarding your point 2:
I have not seen any Collins reference to the cable length correcting ALL BANDS.

Regarding your point 3:
What you're describing could have some merit if that was how the super cathode configuration worked --- but it's not.  It does not work at all as you describe.  It is not even close

This is a simple conceptual explanation that anyone will understand.  No complex math just simple logic.

First the 30S1:

If I was to design a system to improve the linearity of a tube using negative feedback where would I place the sense probe --- on the plate right?  Is there any reason to place the sense probe on the cathode?  NO, only if I wanted to generate negative feedback for the driver.  You claim the cathode to grid capacity is the sense point.  It is not, never was, and makes no sense.

It is plate to grid capacity and if you will note this is a bridge divider about 1 to 43 --- plate to grid 5pf and grid to ground 220pf.  The plate to grid capacity in all of these tubes is approximately 5pf, a 5pf capacitor is added from plate to control grid in the 30S1.  You say the screen is grounded --- shielding the grid from the plate.  Yes it does but notice the 5pf capacitor connected from PLATE TO GRID bypassing the screen.  You say that is not part of the bridge, and just because Collins engineers say it is, doesn't mean anything.  The bridge is described in the owner's manual and engineering docs.  This is simple common circuit design --- common sense.  If it's not part of the voltage divider bridge --- what is it for???  

Your refusal to accept or understand this Fact is the reason for your incorrect conclusions.  

The plate to grid capacity will provide -23 volts when the plate swings negative 1000 volts.  This has the same effect on the tube as the feedback from plate to 180 degree phase shift transformer attached to the cathode.  We are speaking of the 30S1 at this point not the 30L1.  

If the effect looks like, feels like, and smells like neutralization is it not common sense to say that it is???  Is the inverted feedback from the plate to cathode any different than plate to grid???

If you now understand and can accept this, it will be worth explaining the 30L1.  Otherwise I'm wasting my time and need to spend more time with the family.

Kindest regards Jim    




Personalities have nothing to do with technical accuracy or correctness, or being worthless in all areas because they make a few mistakes.  

Any person who understands basic circuits and amplifiers in detail would instantly know the following:

1.) Feedback between user-adjustable resonant circuits is bad news. Depending on reactance both on the operating frequency and outside the operating frequency range, there can be (and usually is) considerable phase shift. Wrapping feedback around circuits that are tuned is a bad idea. This is why bridge neutralization is that completely cancels unwanted feedback capacitance is good, and "over neutralizing" (an odd term) would be bad. The goal is ZERO feedback so tank phase shift has no effect on feedback phase, because there isn't any feedback.

I think this was the source of many Collins problems with field consistency. For example, the 32S series is PA tube critical (unlike many other radios) and it wraps feedback around the driver and PA.

2.) One length of cable cannot possibly provide a constant phase shift over a very wide frequency range. That claim is obviously wrong.

3.) Using a low value capacitor divider between cathode, grid, and ground does not provide negative feedback. It is also not a linear voltage division with varying grid impedance. That is a false claim that anyone understanding basic circuits should be able to see is false. Negative feedback in broad band resonant tank amplifiers pretty much has to added with a series cathode impedance, so as the tube draws more cathode current the voltage drop across that impedance decreases the G-K voltage. A divider does not do that at all, so the concept a divider provides linear NFB is flawed.
  
« Last Edit: August 07, 2016, 06:11:29 PM by K9AXN » Logged
W9NVN
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« Reply #36 on: July 21, 2016, 04:14:49 AM »

Dave,

I believe Mike was referring to the 30S1 although the conversation was addressing the 30L1.

Regardless --- Mikes comment about the screen not having a regulated power supply is questionable ---- it's grounded.  I believe a grounded grid represents a regulated supply.  

Second comment from Mike regarding design faults (The 30S1 has an under powered fan and later amps were shipped with a 4CX1500 installed) .  That fan was fine for the 4CX1000 but for the 4CX1500, it did not make muster.  If the radio was purchased new from Collins with a 4CX1500 installed along with the under powered fan it came from a knockoff shop in some southeastern Asian archipelago using slaves.  

G-Day and Kindest regards Jim
Jim this is really a cheap shot! And very childish on your part!
I like this one;I believe Mike was referring to the 30S1 although the conversation was addressing the 30L1.Why can you talk about both amps and Mike can only speak to one.
Then in my first post you tell me how the late Warren Bruene will speak to me with out any math and make it easy to understand, yet you were not present for the discussion!
What's up with that?
Why is it W9NVN,W9IQ,and W8JI are always incorrect and K9AXN is exactly correct?
Is this just an incident or a pattern. I say it is a pattern. Go back to your SX115 cap rant it is exactly the same. You are right we are wrong.
Let us look at this exchange; Tom says;2.) One length of cable cannot possibly provide a constant phase shift over a very wide frequency range. That claim is obviously wrong.
And you counter with;I have not seen any Collins reference to the cable length correcting ALL BANDS. This is real simple yet you are completely unable to comprehend! Hint; sin of
omission.
None of us appreciate your condescending nature. This a place for exchange of ideas not
 one person impugning the others just like you did to me in the above quote.
When I worked so hard to show Mr. Bruene the error he made, I thought you would embrace me and say; Mike I am so glad you single handily help Mr. Bruene see the light
because he is one of my favorite engineers and I hold him in  high esteem. And what do you do, YOU SHUN ME. 
You know Jim you should take your own advice and go spend more time with your family.
(You know that's what politicians say when they fail at their job) Good line though!! 
You need to find a site with those that are your level and like minded. We grow weary of the constant put downs and your extremely childish behavior that you constantly exhibit here on EHAMS. It's not that we don't love you, its your level issue and constant sophistry. And you also like the Jack Daniels, that could hinder or help.
On behalf of my EHAM brothers and myself  we wish you nothing but the best and hope you find a site.
I would like to close with this. Your little film clip. You tell Tom;Please don’t respond with an it won’t work until you test the concept and shoot a video clip. Meaningless.
Kindest regards and have a great day  W9NVN
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K9AXN
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« Reply #37 on: July 21, 2016, 10:05:50 AM »

Mike,

I probably should have asked you for the math that you used o convince Warren of his, as you say sophomoric theory.  It's easy to denigrate a person who is not in a position to defend their legacy.  Bill Orr has been rightfully or wrongfully maligned for his narrow minded incompetence and he to is not here to defend his position.  Both inappropriate.

Clarification:  You said nothing negative about Bill ORR --- it was others.

My position regarding the Super cathode drive design is that it is not the evil configuration portrayed by Tom.

Tom's point 1 is I believe right on. The 32S and KWM series radios used 2 stage negative feedback making them vulnerable to variations in the final tank reactance.

His point 2 echoes the universally agreed upon fact that the cable length is not effective for all bands.  That to is right on.  

Tom's point 3 clearly indicates he does not understand the Super cathode drive design, yet he condemns Bill Orr for sponsoring it.

Regarding Tom:  He is a far better writer than I and can convey information far more clearly than I can.  He also has the courage to write what he knows will be scrutinized and possibly be torn to pieces.  I believe him to be technically competent and his mantra (Personalities have nothing to do with technical accuracy or correctness, or being worthless in all areas because they make a few mistakes) is as philosophically good as it gets.  He simply does not listen well and tends to say ( you just don't understand).  There are times when he simply does not understand and I have those moments as well.

Please post links to any writing that you have done.  Always interested in others experiences.  

A super day to you --- Kindest regards Jim  



« Last Edit: July 21, 2016, 10:44:40 AM by K9AXN » Logged
W9NVN
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« Reply #38 on: July 21, 2016, 12:28:47 PM »

Mike,

I probably should have asked you for the math that you used o convince Warren of his, as you say sophomoric theory.  It's easy to denigrate a person who is not in a position to defend their legacy.  Bill Orr has been rightfully or wrongfully maligned for his narrow minded incompetence and he to is not here to defend his position.  Both inappropriate.

Clarification:  You said nothing negative about Bill ORR --- it was others.

My position regarding the Super cathode drive design is that it is not the evil configuration portrayed by Tom.

Tom's point 1 is I believe right on. The 32S and KWM series radios used 2 stage negative feedback making them vulnerable to variations in the final tank reactance.

His point 2 echoes the universally agreed upon fact that the cable length is not effective for all bands.  That to is right on.  

Tom's point 3 clearly indicates he does not understand the Super cathode drive design, yet he condemns Bill Orr for sponsoring it.

Regarding Tom:  He is a far better writer than I and can convey information far more clearly than I can.  He also has the courage to write what he knows will be scrutinized and possibly be torn to pieces.  I believe him to be technically competent and his mantra (Personalities have nothing to do with technical accuracy or correctness, or being worthless in all areas because they make a few mistakes) is as philosophically good as it gets.  He simply does not listen well and tends to say ( you just don't understand).  There are times when he simply does not understand and I have those moments as well.

Please post links to any writing that you have done.  Always interested in others experiences.  

A super day to you --- Kindest regards Jim  




Jim, you are still not getting it! I am not posting anything for you. Just give it up and let it go. It is over! GREAT DAY TO YOU W9NVN
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K9AXN
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« Reply #39 on: July 21, 2016, 12:48:20 PM »

Mike,

This thing has gone off the tracks.

I would like to offer my apologies.  I was unprofessional and a bit callous.  Would like to say that I had some extenuating reasons but I didn't --- no excuse.  

This is a closed issue and hope we can disconnect as friends.  Please let me know when you do sea trials on the AL-811H.  Would like to hear your experiences.

Truly a good day to you and Kindest regards Jim    
« Last Edit: July 22, 2016, 03:23:39 AM by K9AXN » Logged
W9NVN
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« Reply #40 on: July 21, 2016, 01:20:24 PM »

Mike,

This thing has gone off the tracks.

I would like to offer my apologies.  I was unprofessional and a bit callous.  Would like to say that I had some extenuating reasons but I didn't --- no excuse. 

This is a closed issue and hope we can disconnect as friends.  Please lit me know when you do sea trials on the AL-811H.  Would like to hear your experiences.

Truly a good day to you and Kindest regards Jim   
ALL IS FORGIVEN! 73 W9NVN
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K9AXN
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« Reply #41 on: July 22, 2016, 09:16:12 AM »

Mike,

To be clear, the apology that I sent was that I incorrectly concluded that you did not correspond with Bruene.  It was inappropriate to assume this simply because it sounded out of character for Bruene to have done so.
 
The other issues with 8Ji, I stand by.  His frequent statement that the author is wrong, just doesn't understand, or any person that understands simple circuits would know this --- is improper.  This is compounded by his lack of conceptual understanding in many cases.  The film clip that I added is a clear statement that the manipulation of neutralizing can be used to generate negative feedback without causing instability.

The SX-115 thread that you mentioned changed my approach to publishing information that I believed useful or maybe interesting to others.  A while back, I placed the last article Precision Neutralizing grid driven amps to my web site rather than this list. 

This way, if there is disagreement it could be directed to my email address and negotiated to conclusion without subjecting folks to negative dialog.  So far it has worked well – not one negative comment has come back, however, several constructive responses were received to make changes for clarity.  This works well.

In the future any detailed info will be placed on the web site and a link posted here.

Have a good weekend --- Kindest regards Jim 
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W8JI
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« Reply #42 on: July 28, 2016, 05:37:28 PM »

Tom,
Here is a film of an UNDER NEUTRALIZED grid driven amplifier.

http://k9axn.com/_mgxroot/img_1323988130_15155_1454557028.avi




Jim,

Your scope pattern (film clip) shows nothing related to this thread or neutralization. All it shows is a phase variation of about 180 degrees between a stable reference and a varying phase point. It goes from -90 to about +90.  

If you are looking at the output and input, the scope pattern simply proves my point. The phase rotates a significant amount. This is why there is no such nonsense as "over neutralizing" to add negative feedback in tuned stages.

To *prove* what I say is correct, go beyond the point of neutralization and run the anode through resonance. If you see a peak of anode current higher on one side of dip than the other, the feedback is shifting phase significantly. True negative feedback will not do that.

Fabricating a fancy theory will not change how it works.
73 Tom
« Last Edit: July 28, 2016, 05:42:55 PM by W8JI » Logged
G3RZP
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« Reply #43 on: July 29, 2016, 03:12:28 AM »

I have seen transmitters with feedback over multiple tuned stages, but each tuned circuit used a servo to adjust it to resonance and the individual stages were bridge neutralised. Obviously, they weren't designed as amateur transmitters!
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K9AXN
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« Reply #44 on: July 29, 2016, 03:26:25 PM »

Tom,

That video clip represents perfect negative feedback resulting from under neutralizing a grid driven amplifier.  

The bottom trace is sensed at the plate and inverted --- the top trace at the grid.  Plate resonance is being dialed back and fourth.  Do you see anything but the grid being MUTED and UNMOLESTED at resonance???    Do you see it out of phase???  Does the peak output occur exactly with the grid depression at resonance???  Do you see the phase shift in the output shifting yet not mutating the grid drive except to depress it at resonance???  Is that not negative feed back in the truest sense?Huh??  Do you see "bumps" on either side???  

If I highly under neutralize it, distortion will be apparent when tuning the final cap back and fourth.  I know exactly what causes that effect and it's not what you claim some sort phase shift from some extragalactic source.

You claim that plate to grid capacity results in positive feedback and it's echoed in your writing --- again this is not so --- it is negative feedback.  

Thanks for the courteous response Tom  

Kindest regards Jim K9AXN

  
    
« Last Edit: August 01, 2016, 10:13:56 AM by K9AXN » Logged
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