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Title: 25M90 Modulation Transformer Post by: W5FH on November 25, 2022, 03:59:37 PM Hello-
I have in my stock a modulation transformer in a sealed housing with a schematic drawing on the side of housing showing the primary and secondary taps. However, they are not identified as to turns ratio or impedance. It is marked "25M90" and "55w". Does anyone here have any data on this unit? It appears as a "poly-pedance" type with many taps. Thanks, Byron W5FH Title: Re: 25M90 Modulation Transformer Post by: WBear2GCR on November 26, 2022, 11:12:13 AM pictures?
You can determine the turns ratio by applying say 10volts AC and measuring the voltages on all the taps. Apply the formula to convert turns ratio to impedance ratio and get a very good idea what it is/does. _-_- Title: Re: 25M90 Modulation Transformer Post by: K9MB on November 26, 2022, 02:20:43 PM Yes, impedance ratio is the square of the turns (voltage) ratio. AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
If you have a good inductance meter, measure the inductance of the high impedance winding. The higher the inductance, the better the low end response. Ideally, it should be 8H or more, though, for example, an A3894 100watt Stancor is only about 4H maximum. If you taylor audio response to cutoff at the low end a bit higher, you can get more power out of it, but give up 50Hz range. Most of these small trannys are not high fidelity. 73, Mike |