The AM Forum
March 28, 2024, 07:22:13 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 [2]   Go Down
  Print  
Author Topic: K1KW 2 X 813 modulated by 2 X 572B's  (Read 17710 times)
0 Members and 1 Guest are viewing this topic.
MikeKE0ZUinkcmo
Member

Offline Offline

Posts: 444



« Reply #25 on: May 29, 2020, 08:47:49 AM »

Beautiful work, Chuck.   Very impressive!!!
Logged

Mike KE0ZU

Bold Text and PICS are usually links

https://mikeharrison.smugmug.com/
Chuck...K1KW
Contributing
Member
*
Offline Offline

Posts: 167


« Reply #26 on: July 04, 2020, 09:31:28 PM »

Update:

The HG-303 Globe transmitter is probably one on the worst rigs released!  After chasing parasitics and other stuff, it turns out that using this rig as a driver was not easy!  I have three of these things and they all exhibit the same instabilities.  No wonder they didn't sell many. 

So....the when I had time over the last few weeks I fixed it.  Too much stuff to mention, but it is an excellent starting platform for a driver, unfortunately, I had to redesign most of it.

Now the 813 rig is working unconditionally stable and in an interesting discovery, it works on 6 Meters!  While checking out performance on 12 Meters I noticed that at minimum capacity on my 813  plate tank cap there was a spike just below 6M!  The final was apparently doubling.  So...thinking that perhaps 6M was in the future for this rig, I decided to try driving it with 6M drive instead of the 24.95MHz.  Modified the HG303 to do 6M output and driving the 813's directly with 50 MHz resulted in more output!  About 450W out at 700W input, vs 200 out when doubling but very tricky tuning.  I did the series resonance trick on the screens and that fixed it.  Now if I want 6M I need to switch the screen bypassing.  Not sure yet but maybe I'll do this.  How about an 2 X 813 rig that does 160 through 6M?

NOTE: I use my spectrum analyser when tuning up new rigs to look for parasitics and harmonic rejection.  Without this I would never have discovered this!  An absolutely invaluable tool!!!


Logged

73, Chuck...K1KW
Opcom
Patrick J. / KD5OEI
Contributing
Member
*
Offline Offline

Posts: 8308



WWW
« Reply #27 on: July 04, 2020, 09:50:56 PM »

160 through 6 - I like that very much. It's great.  Smiley
Logged

Radio Candelstein - Flagship Station of the NRK Radio Network.
steve_qix
Contributing
Member
*
Offline Offline

Posts: 2599


Bap!


WWW
« Reply #28 on: July 05, 2020, 10:39:41 AM »

Hi Chuck, very nice job !!  Interesting on the capacitor failure.... something to keep an eye on.

On your 4  304TLs in parallel - I believe it will work on 40 meters no problem.  I had a rig with a pair of 304TLs and that one worked quite well on 40 meters.  Then I added a 3rd 304TL and it still worked on 40 meters.  So, I suspect yours will as well with 4 304TLs.  Watch out for parasitics (but you know all about that sort of thing).  That was the challenge with my rig.

I used a balanced grid input circuit (for neutralization) and a PI section output.
Logged

High Power, Broadcast Audio and Low Cost?  Check out the class E web site at: http://www.classeradio.org
Chuck...K1KW
Contributing
Member
*
Offline Offline

Posts: 167


« Reply #29 on: July 07, 2020, 11:32:23 PM »

Yup...running triodes is a challenge in RF service!  Many years ago I built a pair of 833A's in push pull using the B&W 1KW plug in tank coils with the swinging link. (Modulated it with a pair as well)

I used a balanced input with cross neutralization.. It worked very well on 160 through 10M

Sold that rig.  Then.....

Built another rig with a pair of 833A's in parallel instead of push pull,  Pi network output, balanced grid input to get the 180 degree shift for neutralization.  That rig worked well, but I had to put a control on the front panel for the neutralizing capacitor since neutralization didn't hold up across more than two bands! 

Anyway, that's what I'm going to try.  Four 304TH's in parallel, Pi Net output, balanced grid input using the National Radio MB-150, and a front panel control for neutralization with dial indicator to set the neutralization when I change bands.  Nothing wrong with that, more knobs on old buzzard rigs are required !  The filament heater power is crazy for 4 tubes, but this will be a room heater.

I'm not expecting anything more than a high frequency end of 40M BUT I will try for 20M!

This will be a Winter project...

Stay tuned, I've got all the components.  Color me bored with all this coronavirus crap...

Chuck

Logged

73, Chuck...K1KW
W2PFY
Contributing
Member
*
Offline Offline

Posts: 13312



« Reply #30 on: August 02, 2020, 01:25:01 PM »

Just tuning around on N1SDR's SDR and ran across Chuck operating his new 813 rig. It was about 1:10 PM today and conditions we not the best. He was talking with Glen WA3GPE  somewhere in 3 land who was a bit stronger than Chuck.


I originally posted a audio sample on here but it sounded horrible not because of Chucks rig, but because I had it set up to record via the web cam microphone. YUK! 

Maybe someone else hear him and can post the audio? He sounded very good to these ears!

Logged

The secrecy of my job prevents me from knowing what I am doing.
steve_qix
Contributing
Member
*
Offline Offline

Posts: 2599


Bap!


WWW
« Reply #31 on: August 05, 2020, 05:52:41 AM »

One design/implementation detail that is missing is anything related to the audio driver or modulator.

If the tubes in the modulator are triode connected (that is the assumption), and the mod transformer has that much inductance, it should be possible, with the proper audio driver, to achieve very good results using a direct coupled audio driver.

I have done this with excellent results - getting almost class E audio performance, at least down to about 30 cycles.  The rig would properly modulate triangle waves, which is what I use for testing.

Because the only phase shift in a proper, direct coupled modulator is in the transformer itself, it is possible to run a reasonably high amount of negative feedback and include the modulation transformer in the loop.

In my particular implementation, I included a high level, 3 diode negative peak limiter (which was of course not in the feedback loop).

Anyway, curious about the audio driver, etc.  Wink
Logged

High Power, Broadcast Audio and Low Cost?  Check out the class E web site at: http://www.classeradio.org
W2PFY
Contributing
Member
*
Offline Offline

Posts: 13312



« Reply #32 on: August 05, 2020, 01:24:47 PM »

Quote
I like the big heat-sink plate caps.
From Tom K1JJ

They are quite old buzzard and I think they were part of the 833A tube socket kit made by Eimac. I think RCA took a stab at it but their socket would not flex on the filament mount as well as Eimac. I think there are plate caps that may radiate heat more efficiently than the Eimac, but they have their own cool factor look which is more modern than the Eimac. What's this note about? To let the younger guys on here know where to source the cool old stuff Grin Grin Grin

I have some them here and one problem I have has is that some will not tighten down without using a mini vice grip. I wonder why that is. Smaller diameter caps on the tube or some other problem?
Logged

The secrecy of my job prevents me from knowing what I am doing.
Chuck...K1KW
Contributing
Member
*
Offline Offline

Posts: 167


« Reply #33 on: March 22, 2021, 12:00:14 PM »

The 813 rig fully integrated into the main operating shack.  Added a few cosmetic improvements including a tuning chart for 160 through 10 Meters.  The 51J4 is used for the receiver when using the ART-13 or the 813 rig.

The side mounted dbx 286 is the only audio processing I'm using with the rig.

I've been using it quite a bit on 40M lately.

BTW, that Atwater Kent horn speaker works and I can select it or the Hallicrafters speaker with the switch mounted at the top of the 286.  It makes for a very interesting sound, kind of like going though a narrow band audio filter which actually improves intelligibility on marginal signals.



* New 813 rig.jpg (723.82 KB, 2016x1512 - viewed 435 times.)
Logged

73, Chuck...K1KW
AG5UM
Member

Offline Offline

Posts: 114


« Reply #34 on: March 22, 2021, 08:21:48 PM »

Great picture!! Beautiful equipment. Good Job!!  Very Cooool !!!
AG5UM
Logged
W7TFO
WTF-OVER in 7 land Dennis
Contributing
Member
*
Offline Offline

Posts: 2521


IN A TRIODE NO ONE CAN HEAR YOUR SCREEN


WWW
« Reply #35 on: March 24, 2021, 12:56:22 AM »

I'm admittedly a meter freak...It is SO NICE to see all yours match Cheesy

It can be a daunting task to achieve that.

I have hundreds of just Westons and Westinghouses here, and still acquire more to be able to have complete sets for projects.

Good job!

73DG
Logged

Just pacing the Farady cage...
N0WEK
Contributing
Member
*
Offline Offline

Posts: 790



« Reply #36 on: March 24, 2021, 03:11:11 AM »

I saw this when you were building last year. Very nice to see in set up for operation.

Great job and a beautiful transmitter.

Greg
Logged

Diesel boats and tube gear forever!
WBear2GCR
Member

Offline Offline

Posts: 4135


Brrrr- it's cold in the shack! Fire up the BIG RIG


WWW
« Reply #37 on: March 24, 2021, 10:29:18 PM »

Dang!

That is one fine looking rig.
Love the switches and the jeweled pilot lights.
The whole things looks first class.

Don't forget to put your callsign on it somewhere.

                   _-_-bear
Logged

_-_- bear WB2GCR                   http://www.bearlabs.com
Opcom
Patrick J. / KD5OEI
Contributing
Member
*
Offline Offline

Posts: 8308



WWW
« Reply #38 on: April 01, 2021, 01:51:33 AM »

I'm admittedly a meter freak...It is SO NICE to see all yours match Cheesy

73DG

YES YES YES! Matching meters!
Logged

Radio Candelstein - Flagship Station of the NRK Radio Network.
Pages: 1 [2]   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 0.081 seconds with 19 queries.