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Author Topic: SB-220 Integrated HV fuse & Glitch Resistor Images (2)  (Read 25022 times)
KM1H
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« Reply #165 on: January 28, 2018, 12:23:57 PM »

Quote
When it comes to neutralization, a good place to start is the article in QST for June, 1946, by W1JPE. It's appropriately titled "No Neutralization Required".

What it does is to provide a real-world equation which shows whether an amplifier should or should not require neutralization. Although aimed at grid-driven amplifiers, the same principles apply to grounded grid.

It's interesting to note how many factors are involved, and how changing any of them can make a big difference in stability.

A decent article for its time and it appears to target the 807 which had a stability reputation all over the place. Many still shy away from that tube and look to the easier controlled 6146.

It also mentions what may be the first time that resistive grid loading, later called swamped grid when no RF coils were used, was mentioned in QST.

I have mentioned several times in the past that I abandoned PP triodes for HF amps back by 1957 due to the required plug in coils (overly complicated bandswitching was not an option) altho I continued to use the AM/CW Class C PP 250TH amp at my parents home while in the USN until late 1963 when it was sold off very cheap and was considered completely useless for SSB and was poorly TVI suppressed. Besides hauling everything in a 57 Chevy to MA, even with a trailer, was considered a waste of time/money/effort.

One big plus with those PP triodes was the ease to cross neutralize that held on all bands once set for the highest frequency used. I used 10M but TVI was so bad it was rarely used. 15M was better since I had a 3 el coax fed yagi (made from a storm damaged 2 el 20M Gotham freebie) and a Johnson TVI filter. Twinlead traps for 21 mc TV IF's were built and handed out throughout the neighborhood plus I didnt operate there at night. The Viking I was extensively TVI suppressed and another Johnson LPF from it to the amp so 20M and lower seldom got complaints.
Im sure the low gain tubes and deep Class C bias helped and parasitic suppressors were pretty much unheard of with those style tubes.

Enter the single or parallel pair tetrode, for many years, swamped grid driven as in the NCL-2000 or GG as in 4-400A and 4-1000A home brew amps when BCB station pulls with a lot of life were free.
No neutralization required in AB1/AB2 service but parasitic suppressors were mandatory and still are in current Tetrode and high gain GG triode amps.

About 20 years ago I got interested in QRO AM again and quickly found a pair of NIB 250TH's and sockets. That new amp used them in parallel, fully bandswitched, and heavy resistive grid loaded which satisfied my need of no neutralization plus I could use my 100W exciters without having to reduce power by much if at all. Rock stable at any tuning point on all bands.

With commercial 2 x 6146/6146B rigs from Collins, Kenwood, Yaesu, and others measuring in the mid -40's dB for IMD3 and above there is no need to even discuss efforts in the low -30's unless they were marginally engineered to start with and with a small incremental improvement ....Heathkits maybe? I never measured any of those.

Carl
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KM1H
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« Reply #166 on: January 28, 2018, 12:28:02 PM »

Quote
f the Flying Monkeys attack, I'll launch a barrage of harsh language that will make a sailor blush.  I'll speak about their Mothers and question their dubious heritage.  If that doesn't work I'll ask Carl and Susie to help.  That would be withering fire for any Flying Monkey.

de......KD9IQO

I wouldnt dare use some of the words and phrases in several languages I learned in the USN on here. However I think them often to a Chosen Few Shocked Roll Eyes

Carl
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AF6LJ
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« Reply #167 on: January 28, 2018, 01:07:39 PM »

Quote
If it wre up to me, Every Ham would have to pass a comprehensive theory test.
Good thing they don't let me make the rules, the hobby would be dead....

I wouldnt go that far Sue.

What really annoys me is that the REAL FCC exams of the 50-60's were not very hard at all. Ive known personally, on the air, or thru the Internet in modern times, many that had no exposure to electronics before or after and made a decision to use the study materials available. Even the later Bash books were helpful in the long term.

When Incentive Licensing arrived in 68 the Extra only portions of the bands were far from empty and the slight breathing room was welcome on CW. SSB was as packed as ever and contests then just added to the QRM as they do today.

Carl
My comment was made in light of my frustration regarding how some people acquire knowledge.
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Take Care
Sue,
AF6LJ

Don't Kalifornicate My Life
K9AXN
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« Reply #168 on: January 28, 2018, 04:12:08 PM »


With commercial 2 x 6146/6146B rigs from Collins, Kenwood, Yaesu, and others measuring in the mid -40's dB for IMD3 and above there is no need to even discuss efforts in the low -30's unless they were marginally engineered to start with and with a small incremental improvement ....Heathkits maybe? I never measured any of those.

Carl

Mid -40's???  Yaesu claims -40 and who else?  All those that claim -35 or better have copied the two stage feedback system that Collins developed.  Additionally, Kenwood sports equalized progressive swamping.  Anyone measured the IMD on all bands?  I believe Yaesu states 20 Metres.  Two stage feed back can render an additional -10db and neutralizing all bands approximately -4db; but a large number of vintage radio's neutralize only 10 Metres leaving the lower bands to progressively positive feed back.

Most of the boat anchors did not have two stage feed back, using precision neutralization to increase the -26db 6146 to -30+.  The only marginal designs were those that did not use two stage feed back and only neutralized 10Metres saying a prayer for the rest.

I have not seen any radios that implement sweep tubes, use two stage feed back.  Kinda gives the 6146 a false leg up.

Regards Jim 
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N2EY
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« Reply #169 on: January 28, 2018, 06:10:44 PM »

The real problem is that Amateur Radio today encompasses an enormous number of bands, modes, technologies and activities - more than ever before, and the scope just keeps expanding.

For example, look back to the mid-1950s in US amateur radio:

There were far fewer bands - no WARC bands, no 60 meters. The vast majority of hams were on the bands between 160 and 2 meters, a few on 220 and 432, a handful on the microwaves. The vast majority used CW, and/or AM, some had SSB and some with connections were on 60 wpm Baudot code RTTY, with CW ID - almost always with surplus teleprinters. A hardy few tried out TV. Equipment was all hollow-state and American made.
 
There were no repeaters, no amateur satellites, no computers in ham shacks, no "digital" modes except the above-mentioned RTTY. No antenna modeling software, fancy digital meters or frequency counters (unless you were super-rich or had "connections".)

On-the-air activities consisted of traffic handling, contesting, rag-chewing and DXing. New, manufactured equipment was very expensive once you got beyond the simplest stuff - and even the simplest stuff wasn't cheap. OTOH, there was WW2 surplus all over, and lots of old radios and TVs that could be parts sources. Plus kits were coming into their own.

In those days the typical amateur had to have a certain level of know-how, simply because the equipment available demanded it. Even so, plenty of amateurs had all sorts of problems due to lack of knowledge and skill; their boo-boos just didn't get as much publicity, because there was no Internet. If someone asked a dumb question, only a few would ever know of it.

As for the license tests....

I have old ARRL License Manuals from 1948, the early 1950s, 1962 and 1971. The study guides in them are interesting in what they cover - and in what they do NOT cover.

For example, the 1962 General guide has a few questions on Ohm's Law, a few on resonant circuits, a few on tube-type power supplies, a few on oscillators and transmitters, a few on various spurious-emission-reduction techniques......and a few on other subjects. And those questions are somewhat in-depth.

But in that 1962 General guide there is NOTHING on repeaters, satellites, transistors of any kind, ICs, synthesizers, RF exposure safety, digital logic, receivers, antennas, transceivers, computers, SSTV, data modes, and many other subjects. The 1962 General didn't have to know ANYTHING about a whole bunch of subjects that are now in the General test.

IOW, you needed to know about a few things in some depth, whereas today, you need to know a little bit about a lot of different things.

And in 1962, the General (and Conditional, Advanced and Extra) gave you full US amateur privileges. All bands, modes, full power. Sure, the Extra existed and a few actually got them, and there were Advanceds who had gotten them back before the end of 1952. But the vast majority of US hams were Generals or Conditionals.

Compare the simplicity of the past to today's range of activities, bands, modes, technologies, etc. There's so much that no one can do it all, or even most of it. And it's natural for those who focus on one small slice of the enormous pie to think they're being left out - or that those who don't know a specific thing are ignorant about everything.

As to how this relates to tube-type linear amplifiers......

In those long-past days, most new US hams started out as Novices, on HF CW, with simple gear. We learned tube basics by actually doing - oscillators, amplifiers, power supplies, TR changeover, etc. When we upgraded to General or beyond, VFOs and 'phone were added. Those who ran high power either had lots of dough (to buy a high power rig) or lots of time and other resources (to build/convert/restore). Often there were many steps along the way.

And there were no competing technologies. Tubes were the current state-of-the art.

But, over the decades, all that has changed dramatically. Most today start out with sophisticated manufactured VHF/UHF gear that requires no tuneup or technical skill at all, other than knowing how to tell it what frequencies to use.

More than 40 years ago, it was possible to run the legal limit on amateur HF with all-solid-state. The last manufactured amateur HF transceivers with tube finals went off the market 30+ years ago.

Tubes are  a niche thing today. For many of today's hams - including many who have been licensed 30+ years - the very first piece of tube gear they've ever had is a linear amplifier.

So it's a bit understandable if there are some misconceptions.

Jim, N2EY
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W9IQ
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« Reply #170 on: January 28, 2018, 06:18:25 PM »

Well stated, Jim!

- Glenn W9IQ
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- Glenn W9IQ

I never make a mistake. I thought I did once but I was wrong.
N2EY
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« Reply #171 on: January 28, 2018, 06:26:35 PM »

Quote
N2EY wrote: When it comes to neutralization, a good place to start is the article in QST for June, 1946, by W1JPE. It's appropriately titled "No Neutralization Required".

What it does is to provide a real-world equation which shows whether an amplifier should or should not require neutralization. Although aimed at grid-driven amplifiers, the same principles apply to grounded grid.

It's interesting to note how many factors are involved, and how changing any of them can make a big difference in stability.

A decent article for its time and it appears to target the 807 which had a stability reputation all over the place. Many still shy away from that tube and look to the easier controlled 6146.

The 807 was perhaps the most popular amateur screen-grid transmitting tube of the times, and the 6146 would not appear for at least 4 more years.

In many RF applications, screen-grid tubes could be used without neutralization and no problems. The trouble was that some hams got the idea that screen grid tubes never needed neutralization......not so!

It also mentions what may be the first time that resistive grid loading, later called swamped grid when no RF coils were used, was mentioned in QST.

That's probably because the classic 1920s/30s transmitter problem was getting enough drive. Using hard-earned RF to heat swamping resistors didn't sell well.

One big plus with those PP triodes was the ease to cross neutralize that held on all bands once set for the highest frequency used.

The classic cross-neutralized push-pull triode amplifier tends to be well behaved like that because:

1) The overall gain is low (compared to what screen-grid tubes can do)

2) There are no RF chokes or other components in the signal/neutralization paths whose characteristics change radically with frequency.

3) The coils, and to a certain extent the capacitors, are optimized for the band in use.

TVI problems in those days were compounded by the fact that many TVs had front-ends that were easily overloaded (even by clean amateur signals far from the TV channel), and that TV signals were often quite weak due to low transmitter power and distance from the broadcast antenna (so even a tiny amount of harmonic RF caused major TVI).

So very different now.

Jim, N2EY
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N2EY
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« Reply #172 on: January 28, 2018, 06:32:43 PM »

Well stated, Jim!

- Glenn W9IQ

Thanks, Glenn!

Here's a bit more:

Take a look at QST for May 1957. Almost 61 years ago, back when hams were supposedly SO knowledgeable.....

First check out an article called "Who's Afraid Of A Receiver?" starting on page 26. It describes a condition that was apparently common in those days: "Receiverphobia" - hams who were afraid to do anything inside their factory-built-and-aligned receivers, for fear of doing irreparable harm! Several pages of really, really basic info - but clearly it was sorely needed.....

(I particularly like the classic cartoon with the caption "He tightened all the loose screws". Shows how old that saying is!)

Next, flip to page 53 and read "The Careless Consumer (or, "Instruction Manuals Are Only For Beginners")". It tells fascinating stories of mistakes made by hams, as told by the technical-service departments of various manufacturers of the day. All sorts of really dumb things done by licensed hams, usually with General or higher licenses!

Some of them pretty amusing. For example:

The ham who bought an NC-57 receiver, hooked up antenna and power, plugged a microphone into the PHONES jack, flipped the SEND-REC. switch to SEND, and called CQ. Kept trying for two weeks and finally wrote National asking why his set didn't work.

Other stories of hams complaining that their rigs didn't work, and then finding they weren't plugged in, or the RADIO-PHONO switch was in the PHONO position, or that an optional SSB adapter wasn't installed, etc. Also failure to understand meter readings on transmitters, failure to read instructions and remove packing material, failure to install tubes, and much more.

Kit manufacturers have all sorts of stories, too - the classic "spaghetti" one is in there too.

So.......what else is new?

Jim, N2EY
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W9IQ
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« Reply #173 on: January 28, 2018, 06:49:04 PM »

Jim,

Quote
So.......what else is new?

As one of my colleagues said, "These are the good old days!".

- Glenn W9IQ
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- Glenn W9IQ

I never make a mistake. I thought I did once but I was wrong.
KD9IQO
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« Reply #174 on: January 28, 2018, 07:01:31 PM »

So.......i'm sitting in an upscale Italian restaurant in Louisville this evening.  I'm with 10 other couples and the women are beautiful and vivacious, the food is to die for, and the Cabernet is a good year.  What am I thinking about, you ask?   -Neutralization circuitry-  Thanks-a-bunch to K9AXN!

http://cubeupload.com/im/KD9IQO/22154167946361425501.jpg
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W9IQ
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« Reply #175 on: January 28, 2018, 07:17:24 PM »

Ah, the ripe black cherries notes of a Tuscan Cabernet...

- 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 #176 on: January 29, 2018, 08:03:45 AM »

So.......i'm sitting in an upscale Italian restaurant in Louisville this evening.  I'm with 10 other couples and the women are beautiful and vivacious, the food is to die for, and the Cabernet is a good year.  What am I thinking about, you ask?   -Neutralization circuitry-  Thanks-a-bunch to K9AXN!

http://cubeupload.com/im/KD9IQO/22154167946361425501.jpg


Never read how to stuff before retiring for the evening or have a date with your wife/best girl.  Comes to no good end. 

Regards Jim 
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K9AXN
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« Reply #177 on: January 29, 2018, 08:12:20 AM »

Well spoken Jim N2EY,

Magnificent those early years were.  Well spoken narrative.

Regards Jim K9AXN
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N2EY
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« Reply #178 on: January 29, 2018, 09:12:29 AM »

Jim,

Quote
So.......what else is new?

As one of my colleagues said, "These are the good old days!".

- Glenn W9IQ

Well spoken Jim N2EY,

Magnificent those early years were.  Well spoken narrative.

Regards Jim K9AXN

Thanks to both!

I'll go a step further....

One can take any period in US Amateur Radio history (except the two World Wars) and describe it as a Golden Age.....or a time when everything was going downhill, things were falling apart, and the end was near.

Example: Some folks see the 1950s as "the Golden Age". And in some ways they were - our numbers were booming, sunspots were all over the place, lots of new companies and new rigs were coming on the market, WW2 surplus was plentiful and cheap, new technologies right and left, prosperity and a growing middle class, suburban growth, no CC&Rs, and more. A General or Conditional license got you full privileges, too! (And after 1954, you only needed to live 75 miles from an FCC exam point to get a Conditional).

OTOH.....

The 1950s began with the Korean War, and there was even talk of shutting down Amateur Radio. Then the Cold War, Conelrad, RACES, fallout shelters, duck and cover, ham gear with CD logos on it. Articles in QST about hams who'd built their shacks into their fallout shelters. Then Sputnik and Muttnik and more.....and US hams were looked upon by some as inferior to their Soviet counterparts in know-how...

TV was The Big New Thing all over the USA - and woe betide the ham even suspected of "causing" TVI. 21 MHz IFs, anyone? On top of AM BCI, of course. And if the oven burned the roast, or the new washer oversudsed - must be that ham next door!

Much of the new gear was so expensive that the average ham could only read the catalogs and dream. The less expensive stuff often wasn't very good at all. Surplus and homebrew could mean lots of work just to get on the air with old technology, and much of it didn't cover all the ham bands. Test gear and information were relatively expensive and hard to get - no internet back then. A single transistor cost a couple of dollars and couldn't do very much.

There were lots of hams but most of them were new and inexperienced. Lots of resentment from those who'd worked hard to get to the top, only to get there and find newbies there who'd gotten a "free ride". "No kids, no lids, no space cadets...."

The 'phone bands were much narrower than today, and full of newcomers. Plus all sorts of odd-sounding modes such as "NBFM" and "SSB", provoking....some disagreements.....between amateurs.

And then in 1958, we lost 11 meters and it was taken over by......other folks, who made a mess.

All depends on perspective. You can make the same kind of case for any time period.

73 de Jim, N2EY





« Last Edit: January 29, 2018, 09:18:30 AM by N2EY » Logged
KB2WIG
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« Reply #179 on: January 29, 2018, 10:01:24 AM »



Short talkers. No phonetics.

KLC
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EXTRALight  1/3 less WPM than a Real EXTRA
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