The AM Forum

Here are two pictures of a transformer that I picked up in Missouri this past weekend. Can anybody tell me what I have here? I think it is a modulation transformer, but the numbers are given in volts, not ohms, so I'm not sure. Thanks, Ron W8ACR

Looks like it's a biggun....

But, instead of impedance, it gives (what I would assume is working) voltage ratings....

A 750 watt modulation xformer.

1800 volts in the rf deck.

2450 on the mod tubes.

Looks like it's set up for big positive peaks!

--Shane
KD6VXI

agreed ... also nice small tertiary windings for screen modulation or system feedback...

not sure if it requires a mod reactor but usual practice would be yes .... maybe not at lower power ... worth a try

Its nothing more than a plate transformer.
Regards,
Gary

Gary,

Very odd that a plate transformer would include a 40-15,000kc specification?!?

                       _-_-

It's a modulation transformer out of a Gates BC500T.

It does need a reactor.

--Shane
KD6VXI

Maybe that Kim Jong-un has a reactor for Ron?

klc

Agree that it is a mod transformer from a BC-500T. Does anybody know what were the final and modulator tubes in that transmitter? And what were the plate voltages and currents for those tubes?

Thanks, Ron W8ACR

http://amfone.net/Amforum/index.php?topic=28009.0

There is another thread on it but I ain't got time to find it right now.

Perhaps a bit more detail on the AMWindow:

http://amwindow.org/tech/htm/modtran/misc/am30469.htm

Perhaps redundant info ...   but,   nice find Ron.

73,   Vic

Sorry, my bad, I should of said mod iron.
Gary

Lol.  It's all good, Gary.  We are all entitled to a slip up a year. 😀



--Shane
KD6VXI

Pair of 833 and single 833 for RF probably in Gates BC500T.

Hi Ron, This is a mod transformer from a Gates BC 1-T BC1-H and others. Also used in the 500 watt models as well . It is not a bad piece of iron. Just keep the B+ down to 2500 V or less. Must use a modulation reactor. Years ago I used one in an 813 rig. A single 813 modulated by a pair of 811 s. I did pass the DC through the secondary. It did work well under those circumstances. Clean high end to 15 Khz !For some reason Gates did not put any protective arc gaps across the primary. Very important. I have worked at a number of stations that had a BC-1T or BC-1 H with a couple of pieces of broken mod iron hanging around. The voltage ratings on the name plate are just another way to express the turns ratio. The bakelite terminal block is a tertiary winding used to partially modulate the RF driver ,pair of 807 s, with the PA tubes. This was a system developed by RCA to get away with full modulation using enough drive to push the 833 s into class C for CW or FM service, but not quite adequate for full plate modulation. As long as the transformer is not blown it is a good piece of iron. I have installed one in a KW-1 with modulation reactor. It worked well.
Good luck, Tim WA1HnyLR

figuring off the voltages and VA ratings gets this:
2450CT 764VA 0.312A 7856 Ohms CT
1800V 750VA 0.417A 4320 Ohms
80V 2VA 0.025A 3200 Ohms
110V 4VA 0.03636A 3025 Ohms
155V 8VA 0.0516A 3003 Ohms

interesting three 3K? windings. The partial BC-1T diagram I have shows a single extra winding for modulating the dual 807 drivers stage. Also, those three VA ratings are low for that, or seem like it. That makes it more interesting.