use for such a large choke?

[NR5P]

I have two 20 henry chokes.  Specs say 125ohms and 300ma, weighs I'd say around 40lbs.  What would this have been used for I wonder?  I know it's a little impractical for an am transmitter for us, but is it usable?  I was thinking it could be used as an choke input filter in combination with a capacitor.  However someone told me that a choke that size could cause massive voltage swings at key up, up to 10kv with a 2kv plate voltage.  Am I missing something?  I know that inductors have the fly wheel effect and that is why it works as a filter.  But that doesn't sound right to me.  I'm not planning on using it right now but figured it might be worth using in the future.  I know with the higher series resistance it will have more voltage drop than a smaller choke.

[flintstone mop]

Very nice for someone building or modifying an AM transmitter. They are great as a reactor used with a modulation transformer to keep the D.C. volts off the Secondary and saturating the mod transformer with D.C. and the audio voltage. The BC transmitters used them almost exclusively to attain higher levels of modulation and wind the mod transformer for better frequency response.

[NR5P]

I found this http://www.amwindow.org/tech/htm/modheising.htm and this http://www.amwindow.org/tech/htm/tvtomod.htm 

I've read up on the modified heising before but having read in depth and didn't realize that high inductance is best.  Looks like these chokes would be perfect for that.  I may be able to use it in my home brew I'm building.  It's going to be 4 1625's modulating either 1625's or 4d32's.  I'm just concentrating on the modulator right now.  Don't get excited though it's just a pile of parts right now

[w8khk]

 It's going to be 4 1625's modulating either 1625's or 4d32's.  

You can't go wrong with four 1625s for modulators.  I modded my Valiant to use four 1625s in push pull parallel.  I replaced the entire speech amplifier, UTC A-10 input transformer with XLR input connector to connect to the audio chain.  Gain stage, phase splitter, and 6SN7 cathode follower driving the 1625 grids.  I used a UTC 120 watt universal mod transformer, and the original valiant mod transformer has all windings in series as the heising choke.  Heising capacitor is out of a dead microwave oven.  Solid stated the power supply, leaving room for all those mods above chassis.   I thought of replacing the 6146s with a pair of 4D32s, but I decided to leave the RF sections alone.  But a pair of 4D32s moded by four 1625s would rock!  

My valiant includes antenna switching relays with a solid state sequencer, and N connectors for antenna and receiver.  Edit: I almost forgot, it also includes Steve's QIX 3 diode negative peak limiter circuit.

[WD5JKO]

Rick, I love those Valiant modifications! I bet that thing TALKS!

Nathan, there is a lot for all of us to to learn from the late Fred Nachbaur. His Dog-Zilla guitar amplifier used a lot of high end tube circuits, ending with six 807's in push pull parallel. The 6SN7 cathode follower drive is especially interesting to me.

I attach the schematic here, and link to the web page:

http://www.dogstar.dantimax.dk/tubestuf/dzindex.htm

Jim
WD5JKO

[John K5PRO]

Look in the AM Window folder, under Tutorials. Two part article form GE Ham News on Power Supply Regulation. It explains why big chokes are not always a good thing.