Chokes in series for Modified Heising Reactor?

[W7SOE]

Are there any considerations to be made, beside voltage and current ratings, when running normal PS chokes in series to form a Heising reactor?

Thanks

Rich

[WA1GFZ]

avoid swinging chokes although it may produce some interesting waveforms

[KE6DF]

Seems to me that having two or more smaller chokes in series rather than one power supply choke with twice the inductance would be better because the parallel capacitance between the windings would be in series.

I've also heard that making the first choke (nearest the plate) a splatter choke might improve peformance at higher audio frequencies because splatter chokes are designed to work at audio frequencies and have limited series capacitance.

(Splatter chokes have low inductance (e.g. 1hy) but high voltage and current ratings). Hard to find, though.

[k4kyv]

Any low-inductance choke with the required current rating would have less capacitance than a full-blown smoothing choke. The splatter choke would be more likely to use laminations designed to be efficient at audio frequencies, though.  Then, in series with that, add enough chokes to bring up the inductance to the required value.

John, WA5BXO and I, while I was living in Houston, constructed a reactor out of two 12-henry smoothing chokes, and ended up with about 30 henries at 500 ma or so.

We took the two identical chokes apart, removed  the "I" part of the E-I laminations, and butted the remaining "E" parts together, coils included.  The same paper core spacer was used as from one of the original chokes, and the two chokes, minus "I" part, were clamped into position with bolts and angle iron stock.

The coils were wired in series, and the polarity of one of the chokes was reversed and tried both ways, to find which connection gave the most inductance.  You want the inductances in the coils to add, not cancel.  If you can locate the start and finish sides of the windings, connect the plate to one of the finish leads (the ones going to the outside or top layers of wire on the coils) for minimum capacitance effect.  If both finish leads end up connected together, try connecting the start leads together instead. Preferably, the windings would be wired F-S-F-S, but F-S-S-F is OK.  In that case, you don't have to worry about how the final choke is wired in the modulator circuit.

Theoretically, the inductance should have been 48 hy,  since the inductance is a function of the square of the number of turns, and the number of turns was doubled with two chokes.  I suspect we ended up with only 3 X the inductance because of the geometry of the final coil and the missing core iron after the "I" laminations were discarded. This still was better than merely wiring the two chokes together, which would have given only 24 hy, and the finished product was lighter in weight and more compact. The increase in inductance with the clamped-together cores is due to the magnetic coupling between the coils.

One could  experiment with the thickness of the gap spacing material, to obtain the maximum inductance at the rated plate current flowing through the reactor.  A  small splatter or other kind of choke in series may still help with the high frequency response, if power supply smoothing chokes are used.

[K5UJ]

here's 20 H 300 ma but it's ending in about 16 minutes

http://cgi.ebay.com/Kenyon-S9881-20-H-300-mA-Reactor-Choke-15-KV-/220701124336

[flintstone mop]

I hope you got it!!!
You can run them in series to get near to the magic number.
But the more chokes you have in series the more the resistance will drop the B+ to the plate of the final pube. I don't think it's too serious of a drop but it is a series resistance.
Fred

[k4kyv]

The resistance will drop your DC plate voltage and thus power input slightly, but allow more positive peak headroom, since it doesn't affect audio voltage.  Acts kind of like the dropping resistor in the classic Heising modulation circuit. Some BC transmitters use a large rheostat of a few hundred ohms in series with the mod reactor as a fine adjustment of the power level.

[W2PFY]

Some BC transmitters use a large rheostat of a few hundred ohms in series with the mod reactor as a fine adjustment of the

This brings up an interesting question for me. In the schematic of the RCA mod transformer you will notice a choke (1L16) that looks like a giant RFC choke in series with the mod transformer to the coupling cap. This choke was put in there as I'm told to reduce high frequency audio components that RCA mod transformers had at the time. Apparently the transformer was able to go way beyond 15 KC's and this choke somehow was to eliminate this unwanted hi end. I have it hooked up this way on my Westinghouse MW-2. I have a problem understanding how this works when there are no caps involved in an RC arrangement to limit these unwanted frequencies. How can this stand alone choke work?This is a one KW circuit but they used in the 5 KW transmitters as well.

Another interesting feature is the feedback network. It uses a center tap in the network where sampling is done from both 833A tubes whereas most others simplify sample it from one end of the modulator feedback network.  

The picture is my Westinghouse mod iron and is the 5 KW stuff. The choke is JS dangling from the ceiling.  

[W2VW]

Hey Terry,

    Someone put a BC-610 inside your Westinghouse.

The RCA iron I got from the old Raytheon RA-5 had a choke and a mica cap network.

I have the parts list and schematic somewhere.

[KA2DZT]

here's 20 H 300 ma but it's ending in about 16 minutes

http://cgi.ebay.com/Kenyon-S9881-20-H-300-mA-Reactor-Choke-15-KV-/220701124336

I bought three of these Kenyon chokes off ebay for about 10 bucks each.  Three separate auctions, different sellers.

They're rated 20Hys at 300ma 15KV 120ohms.  The first one measured only about 110ohms and 17Hys.  Thought that there could be some shorted turns.  When I got the second one it measured the same thing.  The third one also measured the same.  So, I guess those measurements are what they are.

I plan to use two as mod reactors, maybe all three, haven't gotten that far in my rig building.

Fred

[KC2ZFA]

Hey Fred, if you don't use the third sell it to me for $30 (you can't get such
rate of return anywhere else !) 

[KA2DZT]

Hey Fred, if you don't use the third sell it to me for $30 (you can't get such
rate of return anywhere else !) 

So far I haven't sold any of my xfmrs or chokes.  I have a number of high voltage, high current chokes but, not selling any.

I have probably over a 1000 xfmrs and chokes (counting all the small ones).

About 20 years ago, I scrapped about 250 xfmrs and some chokes, mostly ones I couldn't identify, ones I thought I would never use. (big mistake, sorry I did that)  I was taking laminations to the scrap yard 800-1000 pounds at a time,  hundreds of pounds of copper.

I made a machine to unwind the cores and separate all the paper and insulation from the copper.  It was fun to watch the copper wire being wound into coils and the insulation being thrown out onto the ground.

Machine worked great,  in hindsight, destroying the xfmrs was a dumb thing to do.