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Author Topic: 6146??? 6146B - w  (Read 35910 times)
K8BYP
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Posts: 256




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« Reply #60 on: December 15, 2017, 01:22:56 PM »

"replacing the neutralizing cap with one having a greater range I was able to neutralize the rig properly. Clearly, this is not a situation limited to 6146s."

yes, not limited to 6146. Neut capacitance is a function of Miller capacitance which is a function of (A+1) (gain plus 1) and with a different Miller capacitance, the neut cap wasnt the correct range.

Its not so easy to get small HV air variables at a wide range..
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K9AXN
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« Reply #61 on: December 16, 2017, 09:08:08 AM »

Dave,

Your story along with a large number of others having to increase the value of the neutralizing capacitor and the neutralizing capacitor melting in the Collins radios when using the 6146B would seem to confirm the tube data sheets are incorrect for the 6146B.

The data sheets claim that the Plate to grid capacity is .22pf MAX for both the 6146 and 6146B.  If you take six 6146's and six 6146B's and insert them in your radio, the neutralizing feedback and bias required collectively will be higher for the B version. 

The 6146B was deliberately designed to compete with sweep tubes especially in class AB1 mode.  What do you do to a beam type tube to accomplish this.

Use different diameter wire for the screen or control grid or slightly misalign the SG and CG.  The misalignment happens in the production of beam type tubes without exception.  That is what causes the 2/1 range of operational values and the need to hand pick matched pairs.  The higher the bias required, so to will be the achievable increased output in AB1 mode ---- but so to will be the CG to P capacity. 

Glens observations were correct.

Have a great day Dave. 

Regards Jim       
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KM1H
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« Reply #62 on: December 16, 2017, 12:14:55 PM »

There is a lot more than simply reading a spec sheet and stumbling blindly ahead in amplifier design. Collins and Motorola were far from technical leaders with the 6146/6146B interchangeability while many more companies had no to minimal trouble.

Matched pairs was not necessary for most products and the 2:1 issue is at the extreme edge of a bell curve and when US tube manufacturers were building thousands of quality tube the majority were well within the middle. RCA started the migration to garbage quality but one person has tried to convince everyone it was a never shall the two meet compatiblity issue to start with which is PURE BS. I use that "paper" as an example of Hammy Hambone at its worst.
K1DA made a good point to remember.

Carl
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K9AXN
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« Reply #63 on: December 16, 2017, 01:04:21 PM »

There you go again partner, take it easy you should take a nap and read a good book.

A good day to you --- your friend jim    
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KM1H
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Posts: 5298




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« Reply #64 on: December 16, 2017, 01:22:42 PM »

Quote
There you go again partner, take it easy you should take a nap and read a good book.

A good day to you --- your friend jim 

Still cant take anyone not in lock step with you I guess and have to resort to insults; no surprise you havent changed over the decades, it is sad also.

You are no friend of mine either.
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K9AXN
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« Reply #65 on: December 16, 2017, 03:08:59 PM »

Carl, it wasn't an insult.  Also, I wish you a happy birthday.

Regards Jim
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KM1H
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« Reply #66 on: December 16, 2017, 05:09:53 PM »

Just go away Jim I dont believe you and want nothing to do with you..OK, got it?
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K9AXN
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« Reply #67 on: December 16, 2017, 05:45:37 PM »

Just go away Jim I dont believe you and want nothing to do with you..OK, got it?

Carl, No I don't got it!  I was simply trying to find a way to have a friendly conversation with you.  If this can't be done I would suggest removing me from your read list and cease writing sarcastic comments to my posts.  I won't be going anywhere soon and will continue to submit material to this and many other lists.

Have a good evening

Regards Jim
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KM1H
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« Reply #68 on: December 16, 2017, 06:11:07 PM »

You have never had a friendly conversation with me and many others, just syurpy words to mask your deviousness and hate when ANYONE dares to question you and/offers alternative comments.
The real you is very transparent.

Stop the "have a great day" or similar phony comments when replying to me, they make me want to barf.

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G3RZP
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Posts: 1284




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« Reply #69 on: December 17, 2017, 02:25:48 AM »

Transmitters that I designed were made in sufficient quantity to have used about 9,000 6146Bs, while those done by colleagues used about another 6,000. Generally speaking, tubes from the same batch matched reasonably well when new, but mixing batches could give problems, and separate bias controls for each tube made life much easier. Especially for a marine radio that might need work doing on it in some small fishing village where spares are hard to come by.

'Used' 6146Bs that still meet spec on RF output power can have a wide variation - I have measured plate currents of 4 to 28 mA over 13 of them, all except 2 with different date codes. Those two with the same date code matched reasonably well.
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K9AXN
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« Reply #70 on: December 14, 2018, 10:19:38 AM »

The following url contains information that may help to explain the differences in the 6146 tube family.

http://k9axn.com/_mgxroot/page_10935.html

It should help to decide what tube to use in what class of service and what benefits and risks are involved.


This post does not suggest that you choose any specific course of action; it simply provides factual data and time lines to make common sense choices available. 

A Merry Christmas and Happy Holliday season to you!

Regards Jim K9AXN
       
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KD0REQ
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Posts: 2390




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« Reply #71 on: December 15, 2018, 08:48:36 AM »

neutralization of the finals in most rigs will drop the output slightly at 10 meters due to feedback. I would try another driver tube. if that doesn't do it, there might have been Golden Screwdriver visits to the band coils, and it's worth considering a realignment.
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K1DA
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Posts: 744




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« Reply #72 on: December 30, 2018, 11:52:26 AM »

Google "Glen Zook  The 6146 family of tubes"   One tidbit is that a 6146W could be a 6146B.   They have a bit higher gain and the neutralization circuits of some early S Lines could not keep them stable on the higher bands.  I stick with 6146A tubes in mine. 
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G3RZP
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« Reply #73 on: December 30, 2018, 02:29:45 PM »

Quote
One tidbit is that a 6146W could be a 6146B.

Not if you believe the RCA data sheet.....or the Mazda Belvu one.
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WA5VGO
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Posts: 74




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« Reply #74 on: December 31, 2018, 07:17:37 AM »

I get my information from the manufacturer’s data sheets. Never had a problem.

Darrell
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