Warning: Creating default object from empty value in /homepages/11/d132647312/htdocs/Amfone/mkportal/include/SMF/smf_out.php on line 47
How much peak power can a class C 6146B put out?




 
The AM Forum
October 16, 2019, 09:22:29 PM *
Welcome, Guest. Please login or register.

Login with username, password and session length
 
   Home   Help Calendar Links Staff List Gallery Login Register  
Pages: 1 ... 5 [6]   Go Down
  Print  
Author Topic: How much peak power can a class C 6146B put out?  (Read 58744 times)
0 Members and 1 Guest are viewing this topic.
N2DTS
Contributing
Member
*
Offline Offline

Posts: 2307


« Reply #125 on: April 27, 2014, 10:34:46 PM »

The 4D32 is a great tube for the money.
Tough, I run three at 1250 volts on the plate, get 300 watts carrier out, with no color and they do not seem to get hot at all.
1200 to 1500 watts pep, do it all day long for years.
Logged
steve_qix
Contributing
Member
*
Offline Offline

Posts: 2450


Bap!


WWW
« Reply #126 on: April 28, 2014, 12:00:27 AM »

Hi Tom,

I was interested in the parameters mostly because I was trying to calculate the efficiency of the modulator.  The total supply current SHOULD be related to the ratio of the total power supply voltage and the voltage supplied to the load.  So, in theory a 50% duty cycle waveform should result in half the power supply voltage at twice the power supply current at the output of the PWM filter if the modulator were 100% efficient - which it is not (and none are).  So, more current is added to the supply side and that additional power is used up in the form of heat in the modulator.

Ok, to solve your screen dissipation problem use analog compensation on the modulator screens (I had to do this with the 4-400 PWM modulator screen grid for the same reason).  In this way, the average power dissipated by the screens will be a whole lot lower and it will be averaged out over the modulating waveform.

You provide a higher screen voltage when it's needed (under high positive peaks), and a lower screen voltage when it's not needed.  In fact, it will probably help to further linearize the modulator.  The quiescent (no modulation) modulator screen voltage can be reduced and keep the dissipation at a safe level.

Use a source follower MOSFET preceded by a MOSFET voltage amplifier, etc..  make the DC level and audio gain of the screen analog compensation independent of each other so you can get everything adjusted to a fine degree.  Such a system should work FB!
Logged

High Power, Broadcast Audio and Low Cost?  Check out the class E web site at: http://www.classeradio.org
K1JJ
Contributing
Member
*
Offline Offline

Posts: 7866


"Let's go sailing, Tommy!" - Yaz


« Reply #127 on: April 28, 2014, 04:08:18 PM »

Hi Tom,

Ok, to solve your screen dissipation problem use analog compensation on the modulator screens (I had to do this with the 4-400 PWM modulator screen grid for the same reason).  In this way, the average power dissipated by the screens will be a whole lot lower and it will be averaged out over the modulating waveform.

You provide a higher screen voltage when it's needed (under high positive peaks), and a lower screen voltage when it's not needed.  In fact, it will probably help to further linearize the modulator.  The quiescent (no modulation) modulator screen voltage can be reduced and keep the dissipation at a safe level.

Use a source follower MOSFET preceded by a MOSFET voltage amplifier, etc..  make the DC level and audio gain of the screen analog compensation independent of each other so you can get everything adjusted to a fine degree.  Such a system should work FB!


Yo Steve -

That sounds like a great idea to lower the screen dissipation and provide some analog compensation.

Could you draw up a circuit using 11N90 MOSFETs and post it here?  If so, I will build it up and give it a go.  There are a few others who have contacted me regarding schematics for this project, so it could be a benefit for them too.

Thanks.

T

Logged

Frank / WA1GFZ says when he's working near high voltage, as a warning he sings this song by Jay and the Americans: "Come a little bit closer, you're my kind of man, so big and so strong, come a little bit closer, I'm all alone and the night is so long."
K1JJ
Contributing
Member
*
Offline Offline

Posts: 7866


"Let's go sailing, Tommy!" - Yaz


« Reply #128 on: April 29, 2014, 06:05:59 PM »

After adding the four 4D32s, the rig started having key-up instability problems on 40M.  I figgered it was time to add a little vacuum variable neutralizing cap to get the rf final neutralized.

I sampled some RF off the 4D32 plate and fed it back thru the 30 pF 10KV cap -  and into the bottom of the broadband input toroid, which then feeds the grids. It worked like a charm and I was able to "cold neutralize" it by tuning out most of the feedthru signal from grid to plate.

The rig keys very cleanly now on all bands, though it needs slightly move RF drive since neutralization is really negative feedback.  I can now take out some of the grid swamping that kept it stable before.

Neutralization is always a good policy, especially when using multiple tubes.

T

Look for the tiny vac variable mounted on a Plexiglas board with a tuning knob, to the left of the tubes.  I have been experimenting using three final tubes instead of four.  


* DSCF0004.JPG (323.71 KB, 1280x960 - viewed 506 times.)
Logged

Frank / WA1GFZ says when he's working near high voltage, as a warning he sings this song by Jay and the Americans: "Come a little bit closer, you're my kind of man, so big and so strong, come a little bit closer, I'm all alone and the night is so long."
W3GMS
Contributing
Member
*
Offline Offline

Posts: 2964



« Reply #129 on: April 29, 2014, 07:34:35 PM »

Seems like the latest JJ project is almost a rap!  I am sure its been very rewarding and as always, I like to follow along with what your doing.  Everyone learns from tracking your progress.   

As I have said before, its nice when a problem is found a solution is developed rather than totally switching gears.   

Joe, GMS 
Logged

Simplicity is the Elegance of Design---W3GMS
AB2EZ
Member

Online Online

Posts: 1720


"Season's Greetings" looks okay to me...


« Reply #130 on: April 29, 2014, 07:35:06 PM »

Tom

The plate bus-to-ground voltage is AM modulated RF.

Capacitive coupling between the plate bus and the grid bus (due to each tube's plate-to-grid capacitance) puts AM modulated RF between the grid bus and the cathode bus.

So controlling this via neutralization (or other means) becomes even more important in an AM modulated transmitter.

It is also important that the input (grid drive) circuitry, including the grid-to-cathode, etc. capacitance of the tube(s), not make the grid bus-to-cathode bus impedance too high...and definitely not inductive.

The is why, in transmitters (for example, a Ranger or a Valiant) with a tuned circuit on the input side of the tubes (i.e. on the output of the preceding driver stage), one must use a relatively small value of coupling capacitance (typically 2 or 3 times the combined grid input capacitance of all of the parallel tubes) between the input tuned circuit and the grid bus.

Stu
Logged

Stewart ("Stu") Personick. Pictured: (from The New Yorker) "Season's Greetings" looks OK to me. Let's run it by the legal department
K1JJ
Contributing
Member
*
Offline Offline

Posts: 7866


"Let's go sailing, Tommy!" - Yaz


« Reply #131 on: April 30, 2014, 11:36:28 AM »

Seems like the latest JJ project is almost a rap!  I am sure its been very rewarding and as always, I like to follow along with what your doing.  Everyone learns from tracking your progress.  
As I have said before, its nice when a problem is found a solution is developed rather than totally switching gears.    
Joe, GMS  

Joe,
Yep, we think it's a wrap and then another problem or inspiration rears its head.  Jeff / W2NBC hit home when he said it pays to refine - refine - refine.   It took more patience than I had in the past to continue working on the same rig. It was always "NEXT!"

This time I built Fabio II, got it working well and then came back six months later and spent another 3 months refining it. Same with this Dual Quads rig... finished it and later came back and made some major improvements. That's the key... make it a work in progress and it will result in a very nice product in the end.



Stu:  Interesting on RF neutralization reducing the plate voltage from undesirably modulating the grid. I never heard that before.


Your comment about isolating RF driver stages better...  I am using an MRF-150 solid state amp to drive a broadband toriodal transformer into the grids of the 4D32s.  Do I still need to take some isolation precautions using smaller capacitors?  Due to the isolation from HV requirements, I now use 500 pF doorknobs to couple both transformer leads to the grids and the common floating metal plate.

T
Logged

Frank / WA1GFZ says when he's working near high voltage, as a warning he sings this song by Jay and the Americans: "Come a little bit closer, you're my kind of man, so big and so strong, come a little bit closer, I'm all alone and the night is so long."
AB2EZ
Member

Online Online

Posts: 1720


"Season's Greetings" looks okay to me...


« Reply #132 on: April 30, 2014, 01:28:51 PM »

Tom

I think that since your RF driver presents an impedance from the grid bus to the cathode bus that is less than the impedance of the sum of the input capacitances of the tubes... you don't have to use a smaller input coupling capacitor.

Also, the neutralization will greatly reduce the amount of modulated RF coupled from the output to the grids.

Somehow, in the case where the voltage between the grid bus-to-cathode bus (i.e. the input voltage) is provided by a driver having an output tuned circuit with a high impedance, the use of a relatively small coupling capacitor keeps the impedance from grid bus-to-cathode bus from getting too high. Too high an impedance will result in too large a fraction of the plate bus-to-ground RF voltage appearing between the grid bus and the cathode bus. I.e. there is a voltage divider formed by: the impedance of the tubes' plate-to-grid capacitances (adding in parallel), in series with the grid bus-to-cathode bus impedance.

I'm not entirely sure why this works as well as it does. I think that it may be a non-linear effect that involves the diode between the grid and the cathode.

In any event, using a 33pF coupling capacitor between the input tuned circuit and the grid of the amplifier tube... instead of a 330pF coupling capacitor... fixed an oscillation problem in a 2-tube transmitter that I built recently. That transmitter employs a 6CL6 crystal oscillator, with a tuned output, driving a plate modulated 6550.

That little transmitter works great, with 300V B+ and 8W of RF output at carrier. The modulation is very linear. I use a modulator with a negative peak limiter. Positive peaks easily exceed 125%.

Stu
Logged

Stewart ("Stu") Personick. Pictured: (from The New Yorker) "Season's Greetings" looks OK to me. Let's run it by the legal department
K1JJ
Contributing
Member
*
Offline Offline

Posts: 7866


"Let's go sailing, Tommy!" - Yaz


« Reply #133 on: May 01, 2014, 01:49:38 AM »

Sounds good, Stu.  

I'm finding the neutralization required more than just a cold neutralization alignment.  When I decreased drive on 40M I saw some fuzziness on the carrier.  By fine tuning the neut cap trial and error, I was able to eliminate this last remaining instability. A few extra pF was required.

The 4D32 broadband input works FB, but it is not always 1:1 across all bands. So I made up an unbal to unbal T-match tuner that takes the solid state amp and matches it to the broadband input. This tuner previously had a smaller bandswitch that smoked, so I added a bigger one and more strapping coils. 

The 4D32 rig is putting out the same power on all bands now and is sounding sweet. Really pleased with the rig.  I still think the 6LF6 modulators are limiting the quad 4D32s somewhat, but not by much.

T

The input tuner - still needs labels. Bandswitched 160 - 40M:


* DSCF0001.JPG (322.97 KB, 1280x960 - viewed 488 times.)

* DSCF0004.JPG (318.38 KB, 1280x960 - viewed 463 times.)
Logged

Frank / WA1GFZ says when he's working near high voltage, as a warning he sings this song by Jay and the Americans: "Come a little bit closer, you're my kind of man, so big and so strong, come a little bit closer, I'm all alone and the night is so long."
K1JJ
Contributing
Member
*
Offline Offline

Posts: 7866


"Let's go sailing, Tommy!" - Yaz


« Reply #134 on: May 25, 2014, 06:54:02 PM »

Here's a fitting epitaph to complete this project.  

I added a CRL SEP-400 multi-band compressor followed by a CRL PMC-300A  independent negative and positive peak limiter to the PDM rig. These are 1982 vintage processors.    

Here's a short recording made by Jeff/ W2NBC on 75M today.   For once, I am very satisfied with what I am hearing and plan to call it a wrap.  The processing was the final touch needed to this transparent PDM audio platform.   Just what I've been trying to achieve.  (Assuming what I hear on my own playback computer speakers is accurate.)

T

* K-SLAM SEP4.mp3 (1203.75 KB - downloaded 212 times.)
Logged

Frank / WA1GFZ says when he's working near high voltage, as a warning he sings this song by Jay and the Americans: "Come a little bit closer, you're my kind of man, so big and so strong, come a little bit closer, I'm all alone and the night is so long."
W1AEX
Un-smug-a-licious
Contributing
Member
*
Offline Offline

Posts: 1474


Apache Labs SDR


WWW
« Reply #135 on: May 26, 2014, 10:19:07 AM »

There's nothing like a professional quality W2NBC air check to reveal the truth. Sounds real clean Tom. I always favor a nice push in the presence rise area that adds clarity and you've got that just right in my book. Sounds very natural and well balanced. So... now that it's perfect, once it has an official "Vu" name we probably will never hear it again since you always tear your creations apart once the challenge is gone!

Rob W1AEX
Logged

One thing I'm certain of is that there is too much certainty in the world.
K1JJ
Contributing
Member
*
Offline Offline

Posts: 7866


"Let's go sailing, Tommy!" - Yaz


« Reply #136 on: May 26, 2014, 12:12:22 PM »

Hola Rob -

Tnx for the "smooth" report. Glad it's not "tubby."   Grin


Yes, Jeff / W2NBC has helped immensely with setting up my audio chain and dialing it in.  As he says, it can become a hobby within a hobby.   Those who have advanced to the point of setting up low level audio easily can forget how difficult it can be for those of us who still struggle.  There are so many techniques required that we should probably have some more tutorials posted.

Though, it depends on the person and many are happy with a D-104 and that's it. Whatever makes us happy.

One thing I notice:  When I listen to TV and FM announcers, (and many good sounding commercial AM stations) I hear very muted sss's and ch's. It's like these consonants are barely there and are VERY compressed.  In contrast, if you listen to most hams and my own recording, you will hear vary hard ss's and ch's.  What's that all about?   Is it my own imperfect teeth structure - while announcers are selected for perfection?    My own sss's are not spitting and sound clean, but are still very harsh in contrast.

Maybe they are hammering on the D-esser. I have one here but try not to use it.

Or maybe this is the difference between tailoring our audio for communications in marginal conditions vs:  rock-crushing broadcash signals for hi-hi FB entertainment.


T

Logged

Frank / WA1GFZ says when he's working near high voltage, as a warning he sings this song by Jay and the Americans: "Come a little bit closer, you're my kind of man, so big and so strong, come a little bit closer, I'm all alone and the night is so long."
W2NBC
Contributing
Member
*
Offline Offline

Posts: 299



« Reply #137 on: May 26, 2014, 01:11:47 PM »

If you listen closely to current AM broadcast, the audio processing model is to cram as much spectral energy into NRSC standards and poke a hole in your speakers while driving to work.. The bottom line $$ is to be HEARD. The result is some pretty grungy sounding stations, even the flagships from NYC:

All were recorded on an SP-600 off the diode load at 13 kHz- The first is CBS 880, followed by 660 WFAN, and then a familiar voice.. There is no comparison  Wink

Hi-Fi isn't on your AM dial any more. It's found on your HAM dial!

* Comparisons.mp3 (2593.13 KB - downloaded 185 times.)
Logged

Vintage Radio Pages- http://www.dealamerica.com
W2PFY
Contributing
Member
*
Offline Offline

Posts: 13108



« Reply #138 on: May 26, 2014, 02:57:17 PM »

I guess the only way I can explain AM broadcast audio on the male voice, is that it always seems to have a metallic note superimposed on every word, as if all energy is directed to the tweeter. 

Here in the Albany area we have WGY AM/FM. It's a 50K station. The FM side sounds a little better but has the same note. I never heard anyone sound like that in person and have only heard two hams stations sound like that.


Your super smoooooooooooooooooth on your audio Tom Cool Cool Cool Cool Cool Cool

You get six COOLS, My max rating!
Logged

The secrecy of my job prevents me from knowing what I am doing.
W1AEX
Un-smug-a-licious
Contributing
Member
*
Offline Offline

Posts: 1474


Apache Labs SDR


WWW
« Reply #139 on: May 26, 2014, 03:21:49 PM »

Jeff and Tom,

I listen to WCBS 880 in the mornings and now and then throughout the day if I want to catch one full loop of the news. When Pat Carroll does the station ID during her part of the news loop she hits the "C" in WCBS really hard and it comes searing through in such a way that it sounds a lot like the sibilant sound that a station makes when you are tuned off frequency slightly. I've often thought that the station engineer must cringe every time she does that. He probably has to lift his headphones off his ears to let the blood drip out as well.

Rob W1AEX
Logged

One thing I'm certain of is that there is too much certainty in the world.
W2VW
Contributing
Member
*
Offline Offline

Posts: 3489


WWW
« Reply #140 on: May 26, 2014, 09:50:36 PM »

TV audio pretty much has a ton of compression.

Most of the FMs out of NYC are using a gizmo to make the highs have more fuzz.

Eddie Van Headache would be proud.  

The worst thing someone can do IMHO is to boost bass when they don't have the pipes in the first place.

If you don't have the pipes start smoking or embrace your inner Mickey Mouse.

Sorry, life is nought fayr.   
Logged
K1JJ
Contributing
Member
*
Offline Offline

Posts: 7866


"Let's go sailing, Tommy!" - Yaz


« Reply #141 on: May 28, 2014, 10:10:48 PM »

Thanks for the comments, guys.  Jeff, that comparison to the AM broadcash stations using the heavy processing is quite an ear opener....  Grin   I definitely prefer a more mellow sound for ham radio.

Well, after a lot of time trying various audio chains and running lots of tests on and off the air, I've finally settled on a simpler lash up.

I tried running a 528E > 31 band EQ >  CRL SEP 400 multiband compressor > CRL PMA 300A limiter >  PDM generator or solid state audio driver.  This chain worked very well, but was a handful to keep optimized and I found it stunted the  positive peaks. This was probably due to all the EQ/ phase changes in the chain.  I currently prefer higher positive peaks vs: symmetrical audio.  There was also a lot of background fan noise and a "busy" processed sound that comes with compressors.  I also diddled with a Berhinger 9024 digital multiband processor. It worked "OK," but gawd, the menus are a nightmare... give me knobs.

Bottom line is I recently replaced the SEP 400 and PMA 300 with a simple multiband limiter called the Dominator II. It is an extremely fast, transparent, multi-band peak limiter.   Now I can easily dial in moderate density in a flash, keep high positive peaks - and I like the cleaner natural sound. And most importantly, I do not need a negative peak limiter. With -95% negative, my voice naturally produces + 120-140%  positive peaks, depending on frequency. So I can run reasonable audio levels and be clean without banging on an NPL.  

The chain now is:   528E preamp > 31 band EQ  > Dominator II multi-band peak limiter  >  MOSFET audio driver or PDM generator

I like the natural sound very much now and feel like I have full control with less knobs. In addition, the tube PDM rigs takes exactly the same audio settings as the 4-1000A plate modulated rig. This has never occurred before and makes life much easier to switch rigs.

Just wanted to update the overall progress. As Jeff says, audio can be a hobby within a hobby.   Wink

T

Logged

Frank / WA1GFZ says when he's working near high voltage, as a warning he sings this song by Jay and the Americans: "Come a little bit closer, you're my kind of man, so big and so strong, come a little bit closer, I'm all alone and the night is so long."
Pages: 1 ... 5 [6]   Go Up
  Print  
 
Jump to:  

AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
 AMfone 2001-2015
Powered by SMF 1.1.21 | SMF © 2015, Simple Machines
Page created in 0.058 seconds with 18 queries.