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Title: Anybody know how this modulation transformer scheme works? Post by: K8DI on February 18, 2021, 10:29:47 AM So I occasionally type things like "modulation" into the eBay search box to see what comes up.
https://www.ebay.com/itm/Modulation-transformer-Chicago-transformer-vintage-ham-25-watts-military/124546101720?hash=item1cff86b1d8:g:dtQAAOSwL7xgEJVJ&shqty=1&isGTR=1#shId (https://www.ebay.com/itm/Modulation-transformer-Chicago-transformer-vintage-ham-25-watts-military/124546101720?hash=item1cff86b1d8:g:dtQAAOSwL7xgEJVJ&shqty=1&isGTR=1#shId) This is described as a military aviation transmitter modulation transformer. But it isn't...in the conventional primary/secondary sense. It is shown with a single winding, having B+ to the center tap, a pair of P/P audio plates (829B tube, a dual section tube designed for P/P operation) on the ends, and a tap off the top plate to go to the RF class C section. How did this work? Anybody got a schematic? Ed Title: Re: Anybody know how this modulation transformer scheme works? Post by: w4bfs on February 18, 2021, 10:39:48 AM Timtron described this in some transmitter mods awhile back .... no transformer but an autotransformer .... not sure if this can make 100% positive swing
Title: Re: Anybody know how this modulation transformer scheme works? Post by: k7pp on February 28, 2021, 09:05:11 PM Looks like a PP arrangement made for a Heising application. Not able to obtain 100 percent as indicated by previous poster. IMHO.
Title: Re: Anybody know how this modulation transformer scheme works? Post by: W2PFY on March 02, 2021, 03:13:41 PM The way to obtain 100 with that transformer would be to put a dropping resistor in series with the plate of the final tube. It has been done many times and it should be on line somewhere. I don't know if you can get over 100 percent but someone on here knows the dope! That transformer had a lot of other uses, Too bad there wasn't two of them, I would have snatched them and put them into my new project chest. It could have also been used in a circuit where you would have a higher voltage on the modulator tubes with that transformer capacity coupled to a heising choke with a lower voltage feeding the plate final of the circuit. It probably would have been great for low distortion while maintaining excellent highs and lows.
Title: Re: Anybody know how this modulation transformer scheme works? Post by: w1vtp on March 02, 2021, 08:55:41 PM "Turbo connected" modulation transformer. Works great except limited matching capabilities. Yes, needs a dropping resistor going to the class C stage along with an appropriate cap across the dropping resistor to achieve 100 + positive peaks AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
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