HFU HF Underground
Technical Topics => Part 15 AM and FM Station Operation => Topic started by: ChrisSmolinski on May 16, 2020, 1123 UTC
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I was rather annoyed with the poor bass response of the TH transmitter (Rev 4.6). OK, poor is an understatement, pretty much everything below 700 Hz or so was missing. I ended up putting a non polarized 1 uF capacitor in parallel with C301 (located near the center of the PCB, it's a green capacitor) which improved the bass response down to around 40 Hz. I also put an equalizer in the audio chain, to help boost the bass a bit more. Thanks to Dave Richards for pointing me in the right direction.
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Glad you were able to improve the bass response somewhat Chris. I suppose that, given the original intended purpose of these units, we shouldn't be expecting too much in the way of quality audio from them. I have never used one, but picking up a used TH seems like it might be a good way to dabble in Part 15 without breaking the bank. I nearly fell off my chair when I first discovered the price of a Rangemaster!
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I use a TH transmitter around the homestead and have always felt the bass was weak, so I am grateful you posted your improvement. Just for clarification, by non-polarized, you mean a non-polar (or 'bipolar') electrolytic type, right? Or could one use a common ceramic (or mica or mylar, etc.) fixed, non-polarized type?
Mike
N0TLD
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I use a TH transmitter around the homestead and have always felt the bass was weak, so I am grateful you posted your improvement. Just for clarification, by non-polarized, you mean a non-polar (or 'bipolar') electrolytic type, right? Or could one use a common ceramic (or mica or mylar, etc.) fixed, non-polarized type?
Mike
N0TLD
Correct. Not sure what type I used, it was found in one of my junk boxes :)
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Oh yes, I'm sure I have something usable in the MANY junk boxes around here as well! :) Thanks for the clarification.
Mike
N0TLD
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Yeah, really nice Youtube VID on how to stop audio distortion above 2kHz and to improve the auto-tuner. But, what I wanna' know is where did this guy get the schematic for the I Am Radio / Talking House transmitter? I've been wanting that for years. And, of course he's using a nice 100MHz o'scope and what was a $15k Orban optimod. https://www.youtube.com/watch?v=7mSZn5cPX5E&feature=youtu.be
UPDATE: Boomer just linked me into the thread for that here, https://antiqueradios.com/forums/viewtopic.php?f=12&t=131621