Why use a modulation reactor?

[KM1H]

I dont know if I should trust my little hand held Wavetek but it claims it is 84H. It does read the Gates PS 16H choke as 15H however and Ive always found it to have acceptable accuracy at those low Henries.

Reading further the Gates Part is 476-0423-000; made by SNC Mfg Co Part P-6641

I also have a military GE choke at 75# that reads 32H on the Wavetek and is marked, 2750V and 375ma which Im guessing is military conservative to be ignored by hams Havent hi-potted it yet.

[k4kyv]

The inductance will almost certainly be higher with no DC flowing through it, than with full rated current.  84H sounds pretty reasonable for a non-swinging 60H choke with no DC load. What is the physical size and weight?  If feasible, a photo would be interesting.

[KM1H]

10H, 7W, 7D across the windings. Weighs 72#.

No easy way to get a photo where its located plus the data tag needed a magnifier to read.

[Steve - K4HX]

Pick the right tubes and operating parameters, set the modulators up in a totem pole configuration and you can get rid of the modulation transformer.

John/WA5BXO came up with another idea, if you are using a reactor, and a 1:1 modulation transformer and/or a common B+ supply.

This setup uses the entire secondary as an 'autoformer' and will certainly add a lot more 'kick' to the audio.
It will over-modulate quickly but should add a healthy current kick in the actual modulator.

In my case, the modulation transformer has a primary Z of 20,300 ohms, and a secondar of 9,100 ohms.  In order for me to get decent audio (no modulator flat-topping on voice peaks) I had to run 2x the B+ on the 250TH's in the modulator as I did in the final.  1500v @ 200mA is 300w DC Input and 7500 ohms in the final.  I find that I can get more audio onto the B+ line if I pull the link out, and guess what?  1500v @ .150mA is 10k Ohms.

Just for fun (and since I'm using a 60Hy @ 400mA choke and 4uF @ 5kVDC coupling capacitor and a common supply) I'm gonna tack in my RCA 1:1 5,500 ohm mod transformer and see what happens.

[K1JJ]

Pick the right tubes and operating parameters, set the modulators up in a totem pole configuration and you can get rid of the modulation transformer.

The Apache, Mohawk and Chippewa Warriors of Benton Harbor are known to be experts in totem pole modulation.

T

[kb3ouk]

Pick the right tubes and operating parameters, set the modulators up in a totem pole configuration and you can get rid of the modulation transformer.

John/WA5BXO came up with another idea, if you are using a reactor, and a 1:1 modulation transformer and/or a common B+ supply.

This setup uses the entire secondary as an 'autoformer' and will certainly add a lot more 'kick' to the audio.
It will over-modulate quickly but should add a healthy current kick in the actual modulator.

In my case, the modulation transformer has a primary Z of 20,300 ohms, and a secondar of 9,100 ohms.  In order for me to get decent audio (no modulator flat-topping on voice peaks) I had to run 2x the B+ on the 250TH's in the modulator as I did in the final.  1500v @ 200mA is 300w DC Input and 7500 ohms in the final.  I find that I can get more audio onto the B+ line if I pull the link out, and guess what?  1500v @ .150mA is 10k Ohms.

Just for fun (and since I'm using a 60Hy @ 400mA choke and 4uF @ 5kVDC coupling capacitor and a common supply) I'm gonna tack in my RCA 1:1 5,500 ohm mod transformer and see what happens.

Ok, so what's that look like exactly? I'd like to see a schematic.

[W1ATR]

I remember Timtron saying that he used a BC1-T mod xfmr without a reactor, and he couldn't tell any difference in low frequency response.  Don't know if he checked it for waveform distortion at the bottom end, though.  But one thing he did say was that it talked back horrendously when he ran the DC through it. I believe he lost that transformer in the fire.

I think the mod xfmr and reactor in the BC1-F each weigh in at about 200 lbs.  One person, in reasonably good physical condition, could walk across the room carrying a BC1-T transformer under one arm and the reactor under the other.  I don't think one could do that with BC1-F or RCA BTA1-R iron.

This is certainly accurate Don. I have the iron from a 1F here and I can say that if I try to carry that mod trans, it feels like it's trying to rip my fingers right off my hands. Forget getting the mod trans lifted off the floor unless you one of those musclehead competition guys that can lift and throw a grand piano through a third floor window. The reactor is a bit lighter, but not by much.

From my gallery pics.

http://amfone.net/Amforum/index.php?action=gallery;su=user;cat=47;u=1019

[KM1H]

Everything looks bigger in a can and weighs more when we get past 50-60-70... take your pick!

I know way too many hams much younger than me that cant even carry an average size BA receiver or a modern desktop amp.

[W1ATR]

Everything looks bigger in a can and weighs more when we get past 50-60-70... take your pick!

I know way too many hams much younger than me that cant even carry an average size BA receiver or a modern desktop amp.

That's the lazy tv watching video game playing "i don't wanna work for it" society we live in these days. I'm not that old (40), but I can remember when we were little, after school or weekends, we WANTED to be outside. If we were inside in front of the tv, first come the 'request' from the old lady, "Go outside". 10mins later if we didn't move on that one, the 'warning call' came with a little different tone in her voice "GO OUTSIDE and play!". Now the ass whoopin' clock is ticking and everyone knew it. There was no third warning or otherwise. WE would hear her feet charging down the stairs and we would scatter in fear for our lives. Head for nearest door, out a window in your pajamas, hell, run straight through the wall if you had to. Just don't caught by the kung foo grip in your hair, otherwise it was your turn to be the example.

[k4kyv]

I have the iron from a 1F here and I can say that if I try to carry that mod trans, it feels like it's trying to rip my fingers right off my hands. Forget getting the mod trans lifted off the floor unless you one of those musclehead competition guys that can lift and throw a grand piano through a third floor window. The reactor is a bit lighter, but not by much.

From my gallery pics.

http://amfone.net/Amforum/index.php?action=gallery;su=user;cat=47;u=1019

Wonder if that was the stock iron for the 1F, or a  replacement set.  Never before heard of the Maloney transformer company in St. Louis.  I know some 1Fs used Thordarson Tru-Fidelity iron, and others used Chicago Trans. Co. iron. The later models like the 1T used iron by Electro-Engineering.  Much lighter weight, but maybe improved lamination material.

Another odd-ball xfmr manufacturer was Kuhlman in Michigan.  I use one of their 50H 700MA reactors in my 1T, because the original talked back intolerably.

[Opcom]

Everything looks bigger in a can and weighs more when we get past 50-60-70... take your pick!

I know way too many hams much younger than me that cant even carry an average size BA receiver or a modern desktop amp.

I'm not sure they can't - they don't want to or have been taught by decades of workplace signs that anything over 50LB(?) is a 2-man lift.
There's also a difference between lifting and carrying that might not be appreciated.
 

I have the iron from a 1F here and I can say that if I try to carry that mod trans, it feels like it's trying to rip my fingers right off my hands. Forget getting the mod trans lifted off the floor unless you one of those musclehead competition guys that can lift and throw a grand piano through a third floor window. The reactor is a bit lighter, but not by much.

From my gallery pics.

http://amfone.net/Amforum/index.php?action=gallery;su=user;cat=47;u=1019

Wonder if that was the stock iron for the 1F, or a  replacement set.  Never before heard of the Maloney transformer company in St. Louis.  I know some 1Fs used Thordarson Tru-Fidelity iron, and others used Chicago Trans. Co. iron. The later models like the 1T used iron by Electro-Engineering.  Much lighter weight, but maybe improved lamination material.

Another odd-ball xfmr manufacturer was Kuhlman in Michigan.  I use one of their 50H 700MA reactors in my 1T, because the original talked back intolerably.

Those Moloney modulation units look like they would be from the same thing as the Moloney plate and filter iron here. Looks very similar in profile, or maybe all Moloney parts were that style. This stuff came from up North a ways, not from around here.

I never heard of Moloney until last year but their stuff seems really stout. Seems sealed but no oil sloshing, maybe it is potted. You can tap on the side, and it sounds dead solid until you get almost to the top, then sounds empty above that.

The plate unit is a 323 lb Moloney transformer with 115/230V 6.7KVA primary to a 4430-0-4430 sec. and it is about 12x14x14 block. The two Maloney chokes that are with it are rated 5H @ 1.5A /10KV are about 8x8x10 and probably weigh 80-90 lb.

Can anyone confirm or deny the plate iron rating for the 1F transmitter? It would be interesting to know what this Moloney B+ iron came from.

Kuhlman iron I have never seen in this area. Got any pics of it?

[W1ATR]

I have the iron from a 1F here and I can say that if I try to carry that mod trans, it feels like it's trying to rip my fingers right off my hands. Forget getting the mod trans lifted off the floor unless you one of those musclehead competition guys that can lift and throw a grand piano through a third floor window. The reactor is a bit lighter, but not by much.

From my gallery pics.

http://amfone.net/Amforum/index.php?action=gallery;su=user;cat=47;u=1019

Wonder if that was the stock iron for the 1F, or a  replacement set.  Never before heard of the Maloney transformer company in St. Louis.  I know some 1Fs used Thordarson Tru-Fidelity iron, and others used Chicago Trans. Co. iron. The later models like the 1T used iron by Electro-Engineering.  Much lighter weight, but maybe improved lamination material.

Another odd-ball xfmr manufacturer was Kuhlman in Michigan.  I use one of their 50H 700MA reactors in my 1T, because the original talked back intolerably.

I can't say with any certainty if these are the original chunks or not as I didn't actually remove them myself. I was working on a kw build and put a call in to Dave in Kingston (the same Dave S you got a driver tranny for your 300 rig from) and of course he had what I needed and 10 times more. I left his place with a suspension snapping load of iron and a big ol Cheshire cat smile that day. That poor old Blazer was never right after that again, lol.

There is a video on youtube of a 1F in operation and if you pause at 0:26sec, theres a glimpse of a Maloney type trans in the modder section.
http://www.youtube.com/watch?v=XFCT6TV1_ig

A look around the net turned up some history and apparently The company was bought up by another in the usual form back in 1965, but they still operate today producing distribution iron in St louis under Central Maloney.
http://www.centralmoloneyinc.com/transformers/about_us.aspx

Op. The two that I have are def potted units. Id be willing to bet those two you have are potted as well.

Nice stuff there. Good iron is hard to come by these days. Anybody that has anything decent is holding on tight and i can't say I blame them. I've been an iron hoarder for a long time and I have a nice little collection now so when I retire at 80, maybe i can have a good year or two of tinkering.

73   

[k4kyv]

The batteries are crapped out in my digital camera, but the Kuhlman reactor is a grey box a little less than a cubic foot in size  with a couple of white ceramic feed-through insulators on top.  A station in Nashville had three of them, back in the early 80s.  I picked up two @ $50 each.  Should have picked up the third; it probably ended up in the landfill.  So now I have one in my BC1-T and the other one as a spare.  It is rated, stamped on the case, 50H, .670A, 10 kv.  I didn't even mount it on stand-off insulators as I usually do with mod and PS filter reactors.

[KM1H]

Reading further the Gates Part is 476-0423-000; made by SNC Mfg Co Part P-6641

So since the one I have above has Gates right on the tag with their part #, who was SNC Mfg Co who built it as their part P-6641?

[Steve - K4HX]

Here is the schematic.

Pick the right tubes and operating parameters, set the modulators up in a totem pole configuration and you can get rid of the modulation transformer.

John/WA5BXO came up with another idea, if you are using a reactor, and a 1:1 modulation transformer and/or a common B+ supply.

This setup uses the entire secondary as an 'autoformer' and will certainly add a lot more 'kick' to the audio.
It will over-modulate quickly but should add a healthy current kick in the actual modulator.

In my case, the modulation transformer has a primary Z of 20,300 ohms, and a secondar of 9,100 ohms.  In order for me to get decent audio (no modulator flat-topping on voice peaks) I had to run 2x the B+ on the 250TH's in the modulator as I did in the final.  1500v @ 200mA is 300w DC Input and 7500 ohms in the final.  I find that I can get more audio onto the B+ line if I pull the link out, and guess what?  1500v @ .150mA is 10k Ohms.

Just for fun (and since I'm using a 60Hy @ 400mA choke and 4uF @ 5kVDC coupling capacitor and a common supply) I'm gonna tack in my RCA 1:1 5,500 ohm mod transformer and see what happens.

Ok, so what's that look like exactly? I'd like to see a schematic.

[AB2EZ]

I wonder if the circuit, as shown, has an error. I would think that one would need two (2) separate secondary windings on the driver transformer:

a) One winding between the grid of the top tube and the point where the cathode of the top tube connects to the plate of the bottom tube.

b) One winding between the grid of the bottom tube, and the cathode of the bottom tube (phased to produce push-pull operation

Stu

[Steve - K4HX]

You are correct. Two separate windings and two separate bias supplies are required. The corrected drawing is attached.

I wonder if the circuit, as shown, has an error. I would think that one would need two (2) separate secondary windings on the driver transformer:

a) One winding between the grid of the top tube and the point where the cathode of the top tube connects to the plate of the bottom tube.

b) One winding between the grid of the bottom tube, and the cathode of the bottom tube (phased to produce push-pull operation

Stu

[W2XR]

Reading further the Gates Part is 476-0423-000; made by SNC Mfg Co Part P-6641

So since the one I have above has Gates right on the tag with their part #, who was SNC Mfg Co who built it as their part P-6641?

I have the same modulation reactor sitting on the shelf here, made by SNC. I got it along with the Electro Engineering Works modulation xfmr from a Gates BC-1G that was being parted out somewhere down south. Gates sourced these mod reactors from several suppliers, with Electro Engineering Works being their primary supplier for most of the magnetics used in the BC-1T thru the BC-1G when these transmitters were in production, and to a lesser extent, from Basler Electric.

I believe the SNC reactor was supplied by Gates as a spare/replacement part, long after these transmitters were discontinued. At some subsequent point, they referred all customer requests for replacement magnetics for most of their vacuum tube transmitters to Peter Dahl.

SNC is still very much in existence, as I called them (about 3 years ago) upon my acquiring this modulation reactor, to obtain the specs for the unit, etc. The engineer I spoke with was most helpful, and answered all of my questions pertaining to this device. They are located in Wisconsin.

73,

Bruce

[AMLOVER]

    very interesting schematic though......
   
    what is the best Rload matching between AF and RF? 1:1?
    is the grid bias the same voltage as the B class requirements?
    should the B- be floating or grounded at the supply side?
    if cathodes are the center of filament transformers, do they suffer from HV?
   
    It's obvious that i'm looking for a simple brute force modulation sircuit and the 
    totem modulation could be a solution as far my Af pp load matches the Rf mod load
    by a ratio of 1:1.....

    Stefano
   

[AB2EZ]

As a further minor comment on the totem pole circuit

a. The average current that flows out of the cathode of the upper tube must flow into the plate of the lower tube. It is probably better to place a capacitor (e.g. 100uF) between the bottom of the upper secondary winding and the point where the cathode of the upper tube connects to the plate of the lower tube; and to connect  a high value resistor (e.g. 10k ohms) between the grid and the cathode of the upper tube. Doing so will force this capacitor to charge up to a voltage that causes the average cathode current in the upper tube to equal the average plate current in the lower tube. Therefore, there is no separate grid bias power supply would be required for the upper winding.

b. Since both tubes will draw grid current on their respective positive audio peaks, there needs to also be a resistor (typically around 10k ohms) between the grid and the cathode of the upper tube to provide a DC grid-to-cathode current path. This would be satisfied by the resistor in the biasing circuit (described above).


Stu

[KL7OF]

lots of variables....what's your favorite flavor?

[Opcom]

#2 and #4 would create similar tessitura. #2 seems like it could have less average stress on the insulation at the given voltages, only 750V vs the 1250V in #4.

#3 has the audio return fighting the power supply's output impedance and transient surge voltages.

#1 is our friend with DC in the winding.

[W7TFO]

#2 is pretty popular in BC transmitters.

73DG

[KC2ZFA]

Here's #5

http://www.813am.qsl.br/artigos/moduladores/paralel-fed_plate_modulation.png

[k4kyv]

Here's #5

http://www.813am.qsl.br/artigos/moduladores/paralel-fed_plate_modulation.png

I'm not sure what purpose is served by having two blocking capacitors instead of one, but it should work if each cap is twice the capacitance you would use with a single cap. However, I don't think the mod reactor alone would act as a load enough to afford significant protection to the mod xfmr in case the final amp load is lost.

But in case # 3 in the previous set of diagrams, the blocking cap can be wired in series with either end of the mod xfmr secondary, as in either C1 or C2.