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Author Topic: 30L-1 RF INPUT CABLE  (Read 28361 times)
N6QWP
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Posts: 778




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« Reply #15 on: July 18, 2016, 05:20:17 PM »

If modification is indeed necessary ("Ground the grids and over neutralization"), can you enlighten all of us on exactly how to do that?  Thanx for an in depth explaination.
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W9NVN
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Posts: 12




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« Reply #16 on: July 18, 2016, 09:49:13 PM »

I must agree with Tom W8JI on the Collins 30S-1 20.5 cable length. When I first read the owners book,
I said to myself how can this be!? So I contacted Warren Bruene the designer of this amplifier to explain to me how he arrived at his most sophomoric conclusion, and after numerous letters from him laced with
faulty math, and using his equations to prove he was totally wrong, he finally relented and came clean, indicating if it worked at all it would only work on one band! Unless I pointed out to him the error of his
way, he would still think his magic cable would be a 5 band wonder! I am glad I was able to help him.He
seemed like a nice guy, just slightly trying to over engineer..Please note my good friend Reid, former
applications engineer for Eimac was a witness to the entire banter between Mr.Bruene and myself.
 The amplifier had other engineering defects, such as under powered fan, lack of unregulated screen voltage, and poor serviceability, just to name a few.
I also questioned the late Bill Orr W6SAI,who was a good friend of mine about the wisdom of using a
4CX1000A tetrode with a whopping 0 grid dissipation and he said that was before Eimac new what they were doing. They quickly engineered the 4CX1500B and please note ladder day 30S-1s arrived from the factory with 4CX1500Bs installed. VY 73 W9NVN
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G3RZP
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« Reply #17 on: July 18, 2016, 11:05:05 PM »

Neutralisation is done by having an overwind on the filament choke and a capacitor to the plate. One dual 572B amplifier did this by having a plate adjacent to the tubes and connected to the overwind on the filament choke.
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W8JI
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« Reply #18 on: July 19, 2016, 03:43:52 AM »

So....what is the solution(s)?  Simplest first, please. 

The only solution is to make the 30L1 like almost all other 4 tube 811 amplifiers by adding a proper neutralization circuit and nulling out the feed-through capacitance of the 811's.

The same circuit Heathkit, RCA, Gonset, or Ameritron used would work in the 30L1.

All of those amplifiers use bridge neutralization, inverting feedback 180 degrees from anode to cathode through an adjustable capacitor. This way the intentional new neutralization capacitance, being inverted 180 in phase, exactly cancels the unwanted cathode-anode capacitance of the 4x 811 tubes.

Again, this is not some fictitious "over-neutralization" system (which would have similar ill effects). It is a simple nulling out of feed through.

Ameritron inverts phase in a separate transformer and uses a flapper plate near the tube anodes as a capacitor. Most of the other amplifiers use an isolated third winding in the filament choke to invert phase. The phase of that winding must be opposite phase in the filament winding.

If the turns ratio is 1:1, the feedback capacitance has to equal anode-cathode tube feed through capacitance. When properly adjusted the dip in plate current is very close to maximum RF output, allowing tank resonance to occur simultaneously with maximum output and maximum grid current on all bands. (If neutralizing capacitance is too small or too large, or if phase shift through that path is not 180 degrees, this will not occur.)
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WA1RNE
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« Reply #19 on: July 19, 2016, 08:56:36 AM »

 Don't key the amplifier on 15 and 10 without drive, a proper load and near zero tuning capacitance and you should avoid the issue.

 Meanwhile you can figure out what neutralization circuit you want to use and gather the parts.

 I've never tried this and don't own a 30L1, but a small bifilar wound transformer on a mix 31 or 43 ferrite phased correctly and using 5-8 pF of series capacitance for each winding might be a suitable way of getting the required feedback.


...WA1RNE
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K9AXN
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« Reply #20 on: July 19, 2016, 11:59:09 AM »

Mike,

Your assessment of Warren Bruene is way off.  He was one of the select few that truly knew how things worked.  Put him in the league of Dr Gerry Johnson and close to Terman magnificent engineers.  If there was dialog with Warren he would have explained the concepts surrounding the cable length in a way anyone could understand without the use of equations.  If it was not understandable perhaps a revisit with the books is in order.  

A great day to you Kindest regards Jim
« Last Edit: July 21, 2016, 01:07:59 PM by K9AXN » Logged
W9IQ
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« Reply #21 on: July 19, 2016, 01:15:38 PM »

Never the less, the 20.5 foot cable was a completely bogus specification. There is no engineering justification for this requirement.

- Glenn W9IQ
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- Glenn W9IQ

I never make a mistake. I thought I did once but I was wrong.
K9AXN
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« Reply #22 on: July 19, 2016, 02:18:56 PM »

Not true Glen,

You can't possibly believe they simply found 10,400 21.5ft coax cables in a warehouse and decided to demand that you take a few just to get rid of them --- or maybe you can?Huh  I guess those things are not unheard of.  Do you play pokeymon?? 

The cable problem was not the 30L1; it was the 32S and KWM series radios.  Those radios had trouble with any GG amp that used a low Q input design.  That's a discussion in and of itself.

The cable problem is band/configuration sensitive.  It affects the 32S and KWM series radios more so than others.  Know of no other drivers that experienced problems with the 30L1.  It is a result of return current from the 30L1 plate tank passing over the shield of the coax to the driver and back to the 811 cathodes.  There's a lot more to the story but the net of the issue is the Q of the input system could have been raised by a point or two to relieve the problem.  This would require the 30L1 to be neutralized and I believe management just couldn't swallow the disclosure.

Both the 30L and 30S when driven by the 32S or KWM series radios had the problem.  No problem when driven by other transmitters.

Kindest regards Jim

I have no use for Collins the company because of the arrogance of management but Warren Bruene was top of the line. 
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W9IQ
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Posts: 3558




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« Reply #23 on: July 19, 2016, 02:38:19 PM »

I stand by my statement. Show me the calculations that show pairing a 32S or KWM with a 30L-1 using a 20.5 foot cable will solve the problem across all bands involved. It was a commercial band-aid at best.

I have a manual  by B&W that says their 10-80 M trapped dipole had to be fed with a 66 foot coax cable to operate properly. Another example of marketing <> engineering.

-Glenn W9IQ
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- Glenn W9IQ

I never make a mistake. I thought I did once but I was wrong.
K9AXN
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« Reply #24 on: July 19, 2016, 02:58:17 PM »

I didn't say that nor did Collins.  That was manufactured information.  Where did you hear that?  
The G5RV antenna has coax and length requirements to.  Maybe nobody knows what they're doing.  

Kindest regards Jim
« Last Edit: August 07, 2016, 06:32:18 PM by K9AXN » Logged
W9IQ
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Posts: 3558




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« Reply #25 on: July 19, 2016, 03:15:14 PM »

To quote from the Collins 30L-1 manual, 5th edition, copyright 1961/62(1):

Section 1.3.1 "The 30L-1 is particularly applicable to traveling station use in conjunction with portable transceivers such as the KWM2/2A. Refer to figure 1-1."

Section 1.3.2 "Connect the KWM-2/2A, KWM-1, or S-Line as shown in figures 1-2, 1-3, and 1-4."

And what do these diagrams show?

Figure 1-1: Cable call out "RG-58C/U 20.5 ft long"
Figure 1-2 Note 1: "This cable is furnished with the 30L-1 in 20.5 foot length. [SIC]"
Figure 1-3 Note 1: "This cable is furnished with the 30L-1 in 20.5 foot length. [SIC]"
Figure 1-4 Note 3: "This cable is furnished with the 30L-1 in 20.5 4' foot length. [SIC]"

And then finally this gem at the end of section 1.3.4:

"Note: The RF cable supplied for connecting the 32S-1, KWM-2/2A, or the KWM-1 to the 30L-1 is 20.5 feet long. This length results is slightly less system distortion than normally is obtained with other lengths of cable; however, a shorter length may be used for convenience."

If you wish to defend these cable selections in the context of the radios involved, I invite you to show the math. They appear to be nothing more than marketing band-aids that would have no usable affect across all of the bands involved.

Whether or not Bruene was involved in this hyperbole, I have no idea.

- Glenn W9IQ

(1) http%3A%2F%2Fcollinsradio.org%2Farchives%2Fmanuals%2F30L-1-Manual_5th-ed-06-62_Sec1.pdf





« Last Edit: July 19, 2016, 03:33:54 PM by W9IQ » Logged

- Glenn W9IQ

I never make a mistake. I thought I did once but I was wrong.
K9AXN
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Posts: 442


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« Reply #26 on: July 19, 2016, 05:07:11 PM »

Glen,

This is my last response.  It's going nowhere.  Posting denigrating remarks about a deceased engineer who cannot defend his legacy is inappropriate.

I've heard the same indictments of Bill Orr and others who have had the courage to publish technical information knowing that it will be torn to pieces by people with agendas.  What have you or Michael published.  This is a chance for either of you to explain in detail why you think the cable became necessary.  Explain the concept without using complex math --- if you can't your not qualified to comment.  Michael should know he spoke in depth with Warren.

Is there anything in your following quote that refers to all bands???

Is there anything that refers to any driver except the 32S and KWM series radios??

Fact --- the problem is not the 30L1 but the drivers noted.  The 30L1 can be driven successfully by OEM radios without undue regard for unusual cable lengths.

So now we know it's in the drivers.  What did Warren say the problem was with the drivers --- explain please since he shared that???

Btw, there was a 2.5 ft extension for the KWM1 making the cable 23ft.  Guess they found some 2.5ft cables they needed to get out of the way. 

I'm wasting my time --- you get last podium --- case closed.  Going to chow and a Jack Daniels.  Have a great day!

Kindest regards Jim     


To quote from the Collins 30L-1 manual, 5th edition, copyright 1961/62(1):

Section 1.3.1 "The 30L-1 is particularly applicable to traveling station use in conjunction with portable transceivers such as the KWM2/2A. Refer to figure 1-1."

Section 1.3.2 "Connect the KWM-2/2A, KWM-1, or S-Line as shown in figures 1-2, 1-3, and 1-4."

And what do these diagrams show?

Figure 1-1: Cable call out "RG-58C/U 20.5 ft long"
Figure 1-2 Note 1: "This cable is furnished with the 30L-1 in 20.5 foot length. [SIC]"
Figure 1-3 Note 1: "This cable is furnished with the 30L-1 in 20.5 foot length. [SIC]"
Figure 1-4 Note 3: "This cable is furnished with the 30L-1 in 20.5 4' foot length. [SIC]"

And then finally this gem at the end of section 1.3.4:

"Note: The RF cable supplied for connecting the 32S-1, KWM-2/2A, or the KWM-1 to the 30L-1 is 20.5 feet long. This length results is slightly less system distortion than normally is obtained with other lengths of cable; however, a shorter length may be used for convenience."

If you wish to defend these cable selections in the context of the radios involved, I invite you to show the math. They appear to be nothing more than marketing band-aids that would have no usable affect across all of the bands involved.

Whether or not Bruene was involved in this hyperbole, I have no idea.

- Glenn W9IQ

(1) http%3A%2F%2Fcollinsradio.org%2Farchives%2Fmanuals%2F30L-1-Manual_5th-ed-06-62_Sec1.pdf






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W9IQ
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Posts: 3558




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« Reply #27 on: July 19, 2016, 10:03:46 PM »

Jim,

You have your wires crossed. I was not the one that posted comments about Breune or Warren. That was another poster.

The OP asked if a special length cable input cable is needed with the 30L-1. To this, I responded:

Quote
Never the less, the 20.5 foot cable was a completely bogus specification. There is no engineering justification for this requirement.

Now you have stated:

Quote
The 30L1 can be driven successfully by OEM radios without undue regard for unusual cable lengths.

So on this narrow point we are in agreement. I will leave it there.

- Glenn W9IQ

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- Glenn W9IQ

I never make a mistake. I thought I did once but I was wrong.
W9NVN
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Posts: 12




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« Reply #28 on: July 19, 2016, 11:36:07 PM »

Mike,

Your assessment of Warren Bruene is way off.  He was one of the select few that truly knew how things worked.  Put him in the league of Dr Jerry Johnson and close to Terman magnificent engineers.  If there was dialog with Warren he would have explained the concepts surrounding the cable length in a way anyone could understand without the use of equations.  If it was not understandable perhaps a revisit with the books is in order. 

A great day to you Kindest regards Jim
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W9NVN
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Posts: 12




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« Reply #29 on: July 20, 2016, 12:17:20 AM »

Jim, my  assessment of Mr.Bruene is exactly correct,and since I corresponded with him I
am aware of how he unsuccessfully tried to justify his position. In due respect you should study my first post, as every thing is explained in detail. However, I agree with you in that I helped him revisit the books as it was in order for him so he doesn't make the same mistake twice! The great W9IQ is most correct with his first post. Just because Mr.
Bruene was in error, there is no one saying he is a poor engineer, he is not perfect, and
that is not bad.. So have a nice day and keep studying..
   
       73 W9NVN

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