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Title: Mod Transformer Info Needed Post by: W8UJX on May 29, 2013, 04:38:25 PM Anybody have a data sheet on a Thordarson T21M64 modulation transformer? Tks, Jerry, W8UJX Title: Re: Mod Transformer Info Needed Post by: W4RFM on May 29, 2013, 05:03:32 PM Hey Jerry,
All I have found so far is that it is rated for 300 watts of audio, with 250mA max on the primary and 500 mA max on the secondary, and it cost $83.00 a long time ago. Title: Re: Mod Transformer Info Needed Post by: W8UJX on May 29, 2013, 08:53:33 PM Thanks Bob,
I thought it was rated at 300 watts but I did not know the current ratings. It cost considerably more than $83 a short time ago. Hi... It has two what appear to be center tapped windings on each side and I'm not sure which side is the primary. I would guess the rating on the secondary is with both windings wired in parallel. I did a test with 110 VAC RMS applied to the primary(?) pins 1-7 with the two windings in series, pins 3 and 4 jumpered. With both windings connected in series on the secondary(?), pins 9-10 jumpered I measured 89 VAC RMS across pins 7-12. So I guess primary to secondary in that configuration is step down. Jerry, W8UJX Title: Re: Mod Transformer Info Needed Post by: kb3rdt on May 30, 2013, 12:37:31 AM Thordarson multi-match 300 watt
http://n4trb.com/AmateurRadio/RCA_Ham_Tips/issues/rcahamtips1004.pdf Title: Re: Mod Transformer Info Needed Post by: W7TFO on May 30, 2013, 12:55:31 AM The tubes recommended for use as modulators are:
HK-54 203A 211 805 808 811 838 TZ-40 T-55 35T 100TH HF-100 ZB-120 They purposely didn't publish impedances, as that is so variable under class 'B' conditions. Go with the ratio specified and try different combinations for best results. 73DG Title: Re: Mod Transformer Info Needed Post by: W8UJX on May 30, 2013, 09:49:15 PM Thanks for the link to the info for the mod transformer Carl. The one shown is the one I have.
I was thinking of building the modulator shown in K1JJ's quad 813 rig and driving it with a Heathkit Hi-FI amp. I connected the transformer as shown in the schematic and applied 120 VAC RMS 60 Hz (measured 119.2 VAC) from the wall socket to the primary. The voltage at the secondary (no load) measured 68.6 VAC RMS so I guess the way the terminals are connected (primaries in series and secondaries in parallel) is close to 2:1 step-down which was recommended by K1JJ. I'm assuming the transformer will pass the 60 Hz frequency. Jerry, W8UJX Title: Re: Mod Transformer Info Needed Post by: KE6DF on June 01, 2013, 06:43:43 PM Thanks Bob, It has two what appear to be center tapped windings on each side and I'm not sure which side is the primary. I would guess the rating on the secondary is with both windings wired in parallel. I think it's a new version of the 11M77 -- same ratings, but different packaging. Connection info on the 11M77 is available on AM Window Title: Re: Mod Transformer Info Needed Post by: W8UJX on June 02, 2013, 12:14:02 PM Thanks David, AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
119.2 VAC RMS conected to the primarys wired in series produced 68.6 VAC RMS on the secondaries wired in parallel. 119.2/68.6 = 1.737. The data on the connection info, Turns Ratio (Pri to Sec) says 1.73 so I guess that is the correct information for this transformer. Where else would I find answers to questions like that except AMfone. Jerry, W8UJX |