Warning: Creating default object from empty value in /homepages/11/d132647312/htdocs/Amfone/mkportal/include/SMF/smf_out.php on line 47
4-65A as modulators




 
The AM Forum
September 30, 2023, 10:19:51 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]   Go Down
  Print  
Author Topic: 4-65A as modulators  (Read 14360 times)
0 Members and 1 Guest are viewing this topic.
WZ1M
Member

Offline Offline

Posts: 393


« on: October 28, 2009, 12:30:08 PM »

OK, now I am thinking of a pair of 4-65A's as modulators for the two 813's. Thoughts please. I cant seem to find any schematics of the 4-65A being used as such. On the other hand, didnt really dive into the research for to long.
Regards,
Gary
Logged
Jim KF2SY
Member

Offline Offline

Posts: 291



« Reply #1 on: October 28, 2009, 01:30:38 PM »


The Eimac datasheet has some data.


* 4-65A eimac.pdf (1412.6 KB - downloaded 325 times.)
Logged
W1AEX
Un-smug-a-licious
Contributing
Member
*
Offline Offline

Posts: 1488


Apache Labs SDR


WWW
« Reply #2 on: October 28, 2009, 02:17:50 PM »

This won't be much help, but I was given (in pieces) a military rig (Air Force) that used a pair of 4-65's to modulate a pair of 4-65's. I still have the mod transformer, which was quite small, and did not have much iron in it, but I suppose that would be expected as it was built for installation in various aircraft. The transmitter looked to be in the 100 - 150 watt power class. When I played around with 4-65's I found that they loved high voltage and low current, and in the end, didn't seem worth the trouble when other more plentiful tubes that could exceed their performance were floating around out there. Just my 2 cents of course!
Logged

One thing I'm certain of is that there is too much certainty in the world.
W2PFY
Contributing
Member
*
Offline Offline

Posts: 13310



« Reply #3 on: October 28, 2009, 02:40:52 PM »

I think they would be fine if you used them in push pull parallel for a pair of 813's. I would run push pull parallel for just one 813. They will add a nice glow to your rig that are otherwise boring to look at 813's do not do. Well maybe some blue glow in them. Don't get me wrong, I like 813's. There are as versatile a 30.06 hunting round. 

Here's a PDF if I can up load it. Tells you all the specs, has circuit diagram for 500 watt rig using 4-65 in the mod and final. 

* 4-65A-1.pdf (1412.6 KB - downloaded 410 times.)
Logged

The secrecy of my job prevents me from knowing what I am doing.
N2DTS
Contributing
Member
*
Offline Offline

Posts: 2307


« Reply #4 on: October 28, 2009, 03:47:15 PM »

A pair will work if you turn the 813's way down.
Figure 250 watts out of a pair and a high impiedance.

Nothing else on hand to use?

Besides the low power output, you have to build a regulated screen supply and bias the tubes, and even so the distortion is higher then some other tube choices.

811a's will do 340 or more watts without any screen or bias supply.

If I was to go to the trouble of building regulated screen supplies and bias supplies, I would opt for a good AB1 tube that has low distortion and lots of power output.
4x150a / 4cx250b type tubes, up to 600 watts out with zero driving power, work from 1000 to 2000 volts.

Brett


Logged
WA1GFZ
Member

Offline Offline

Posts: 11152



« Reply #5 on: October 28, 2009, 03:49:36 PM »

How about 813s modulating quad 4-65s. They are a high Z tube so 4 would help. They are a better RF tube above 20 meters.
Logged
W2PFY
Contributing
Member
*
Offline Offline

Posts: 13310



« Reply #6 on: October 28, 2009, 04:19:30 PM »

Quote
811a's will do 340 or more watts without any screen or bias supply.
True, they'll work but 811's while are excellent tube are another boring tube to look at. I think home brew rigs should be built for show and glow is what you would get, from 4-65's. They would run red to orange when loaded up or talked up to max. Why not triode connect them?  That is what I would do,  so forget the screen voltage. I've got bunches of them and  I'm still waiting to do something with them. Oh well, just my 3 cents worth.
Logged

The secrecy of my job prevents me from knowing what I am doing.
WZ1M
Member

Offline Offline

Posts: 393


« Reply #7 on: October 28, 2009, 05:16:02 PM »

Thanks for all the input. I do have 811's kicking around and also a nice pair of 8005's. I was just thinking of something different than the same old, same old. Now what I should do is put together the 3CX15000 driven by a 5CX1500, but think that one would get me into real hot water.
Again, thanks guys for the info.
Regards,
Gary...WZ1M
Logged
W1AEX
Un-smug-a-licious
Contributing
Member
*
Offline Offline

Posts: 1488


Apache Labs SDR


WWW
« Reply #8 on: October 28, 2009, 05:24:50 PM »

Just out of curiosity Terry, when triode connecting a tube like the 4-65, does the screen get tied to the grid, or to the plate? My thought is that since they would be grid driven with audio, that the screen would be tied to the plate, but I'm not sure. I remember asking this question a few years ago about triode connecting grounded grid 4-400's in a couple of different forums and there were good arguments for screen to grid and also screen to plate, so possibly it would work either way. I have a feeling one way may be better for the tube than the other but don't have a clue which would be best. Any thoughts?

Good luck with the rig Gary. Stay off the high voltage!

Rob W1AEX
Logged

One thing I'm certain of is that there is too much certainty in the world.
k4kyv
Contributing Member
Don
Member

Offline Offline

Posts: 10062



« Reply #9 on: October 28, 2009, 08:45:39 PM »

If you are running it as a lo-mu triode, tie the screen to the plate.  As a  high-mu triode, tie it to the control grid. 

Remember there is a maximum voltage rating for the screen grid, so if you tie the screen to the plate, the maximum plate voltage will be limited to the maximum rating for screen voltage.

With the control and screen grids tied together, the tube functions as a high mu triode, usually zero bias.  It works well with 813's.  With 807's, a 20K resistor is required between the two grids, and IIRC, the audio is fed to the screen grids.
Logged

Don, K4KYV                                       AMI#5
Licensed since 1959 and not happy to be back on AM...    Never got off AM in the first place.

- - -
This message was typed using the DVORAK keyboard layout.
http://www.mwbrooks.com/dvorak
W2PFY
Contributing
Member
*
Offline Offline

Posts: 13310



« Reply #10 on: October 28, 2009, 09:00:23 PM »

Please stand by. More to come. Please stand by.

Update:

I said please stand by, some of you out there are sitting.

Quote
The Eimac datasheet has some data
 Sorry Jim, I didn' see your pdf.
Logged

The secrecy of my job prevents me from knowing what I am doing.
w4bfs
W4 Beans For Supper
Contributing
Member
*
Offline Offline

Posts: 1433


more inpoot often yields more outpoot


« Reply #11 on: October 28, 2009, 10:01:02 PM »

they are cute little bottles but don't store very well .... about half I had in storage had lost their vacuum ... before you commit to a design, TEST
Logged

Beefus

O would some power the gift give us
to see ourselves as others see us.
It would from many blunders free us.         Robert Burns
Opcom
Patrick J. / KD5OEI
Contributing
Member
*
Offline Offline

Posts: 8242



WWW
« Reply #12 on: October 28, 2009, 10:43:43 PM »

The military T-217 UHF transmitter making 100W out on 225-430MHz used a pair of 4-65's in AB1 to modulate a pair of 4X150's. Plate voltage was 1200-1500 IIRC, and the plate to plate load was about 9000 Ohms. Mod iron was rated 120 watts. 

The 100 watt output URT-12 Coast Guard transmitter uses a pair of 4-65's to mod a pair.  The mod transformer is rated 14KCT to 12K, 90 watts RMS. I do not know the HV but the power transformer is 3500V center tapped at 0.25A so that means maybe 120mA average current for the modulator. Chokes are rated 1400 volts working in that one.
Logged

Radio Candelstein - Flagship Station of the NRK Radio Network.
W1AEX
Un-smug-a-licious
Contributing
Member
*
Offline Offline

Posts: 1488


Apache Labs SDR


WWW
« Reply #13 on: October 28, 2009, 11:41:44 PM »

Thanks for clarifying the triode connection parameters Don. That will be helpful with a little project I am working on.

My 4-65 push pull modulator carries the label "AM 773A/ARC-21" and is stamped with the RCA logo. I have never found out much about the rig it came from, but it sure was a complex chunk of gear with numerous Potter & Brumfield relays throughout. Looks kind of funny with the odd shaped pull out handles bolted to the chassis.


* 4-65 Modulator 001.jpg (54.67 KB, 640x480 - viewed 1455 times.)
Logged

One thing I'm certain of is that there is too much certainty in the world.
The Slab Bacon
Member

Offline Offline

Posts: 3934



« Reply #14 on: October 29, 2009, 08:21:29 AM »

Just out of curiosity Terry, when triode connecting a tube like the 4-65, does the screen get tied to the grid, or to the plate? My thought is that since they would be grid driven with audio, that the screen would be tied to the plate, but I'm not sure. I remember asking this question a few years ago about triode connecting grounded grid 4-400's in a couple of different forums and there were good arguments for screen to grid and also screen to plate, so possibly it would work either way. I have a feeling one way may be better for the tube than the other but don't have a clue which would be best. Any thoughts?
Good luck with the rig Gary. Stay off the high voltage!
Rob W1AEX


Rob,
      Generally speaking tying the screen and plate together is usually used for lower powered class A operation. Tying both grids together us usually used for class B or similar service where you are pushing the grids to draw some grid current. Tying the grids together will usually give a lower voltage gain, but a higher power gain, requiring more drive to kick them along.
 
                                                               the Slab Bacon
Logged

"No is not an answer and failure is not an option!"
The Slab Bacon
Member

Offline Offline

Posts: 3934



« Reply #15 on: October 29, 2009, 08:26:41 AM »

they are cute little bottles but don't store very well .... about half I had in storage had lost their vacuum ... before you commit to a design, TEST

Most of the tubes of that style envelope from that era had the same problem. I needed some 826s for an old gonstipated VHF amplifier. I must have went through a least a dozen of them to find a good pair! !   However for some odd reason 829Bs dont seem to have that problem.

                                                                  The Slab Bacon
Logged

"No is not an answer and failure is not an option!"
WBear2GCR
Member

Offline Offline

Posts: 4135


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


WWW
« Reply #16 on: October 29, 2009, 08:39:03 AM »



Dunno about 4-65s as modulators... high voltage low current = high Z - that makes the match to the primary side of the mod iron difficult. Not impossible but not that easy.

I'd run it the other way... 813s or 811s modulating the 4-65s??

Maybe some 4-125s or 4-250s might be nice, they seem to not be "desireable" and go pretty low in most cases....

Or why not a "JJ" style 813s by 813s rig??

Oh, if you strap the 4-65s as triodes the plate Z will be somewhat lower, but still if you want to make power with them the B+ will need to be rather high making the mod iron match and V rating a bit tricky... also they make less pow-air in triode.

                     _-_-WBear2GCR

Logged

_-_- bear WB2GCR                   http://www.bearlabs.com
W2PFY
Contributing
Member
*
Offline Offline

Posts: 13310



« Reply #17 on: October 29, 2009, 10:45:15 AM »

Quote
r why not a "JJ" style 813s by 813s rig??

Because they are boring to look at. His circuit would be just fine. 813's are the kind of bottles that should be hidden. Now Glow, NO Show Grin Grin Grin Wink Wink Wink
Logged

The secrecy of my job prevents me from knowing what I am doing.
WBear2GCR
Member

Offline Offline

Posts: 4135


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


WWW
« Reply #18 on: October 29, 2009, 07:26:53 PM »


Erry-Tay,

Youze needz to get ur ies chzeched?

Take a look at the pic of KC2FXE's rig that I took, I think it is in my gallery. Plenty of glow.
Ya haz ta know how to build for max gloowww!!  Grin

but whatever... bottom line is uze the toobes ya brung witcha!

                         _-_-
Logged

_-_- bear WB2GCR                   http://www.bearlabs.com
Pages: [1]   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 0.074 seconds with 18 queries.