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Broadcast Audio from your DX-60




 
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Author Topic: Broadcast Audio from your DX-60  (Read 50724 times)
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W4EWH
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« Reply #75 on: January 29, 2019, 01:50:27 PM »

I use my shack audio system - same one is used for all rigs.  This is really the only way to go if you have more than one transmitter.  Just build up an audio system with EQ, peak limiting, etc., make it line level out and then you can use it with anything.

I'm going to standardize my shack's audio that way, and I'd like to know what "line level" is in this context. I have a Ranger I, a T-60, an IC-7300, and a Class D (sorry) AM transmitter. Do you bypass the mic amps in the individual rigs?

Thanks in advance.

Bill, W4EWH
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KD1SH
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« Reply #76 on: January 29, 2019, 05:52:20 PM »

   Just bought a used hardcover copy of the 15th edition a few months back; wish I'd known about this website!  Bill Orr was awesome - I was building stuff from designs in his books back in the 70's.
    In the January issue of Electric Radio there's an excellent article by W7YAZ about screen modulated novice transmitters; some very good info and well presented operational theory.

I first saw this type of screen modulator in The Radio Handbook 15th edition (1959), Pp 290,291. Available here:
http://www.tubebooks.org/books/orr_radio.pdf
It's a good read, describing the function of the circuit. Also, it contains two potentiometers, one for carrier level and one for negative peak level. There are, of course, many ways to implement the concept. The circuit that Steve presents is a proven design. It should work as well for you as it did for him.

Don
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WA4WAX
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« Reply #77 on: January 30, 2019, 07:30:39 PM »

Trailer Trash audio for your DX-60.

https://archive.org/details/73-magazine-1964-05/page/n1
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KD1SH
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« Reply #78 on: June 22, 2020, 07:10:13 PM »

    Okay, this is an old thread, but at least threads that refuse to die don't eat your brain like zombies.
    I put Steve's nifty mod into my DX-60B over a year ago, but never really took much time to examine the results.  Here are a few scope shots.  From 20hz to 15khz, with the sine injected right at the top of the audio gain pot, as Steve indicates in his schematic.  Not exactly flat; note that I had to increase the amplitude a bit at 15khz to get the same RF envelope (chan 2 volts/div is changed; look at the readout not the trace) but from 20hz to 15khz is a long haul.
    But, it's pretty clean across that whole range.  Note the phase shift from input signal to RF envelope: the input leads at 20hz and lags at 15khz, yet is smack-on at 400hz.  Learning moment: why is this?


* at 20hz.JPG (188.9 KB, 1280x960 - viewed 46 times.)

* at 400hz.JPG (182.24 KB, 1280x960 - viewed 45 times.)

* at 15khz.JPG (189.11 KB, 1280x960 - viewed 51 times.)
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KD1SH
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« Reply #79 on: June 23, 2020, 09:20:06 AM »

   Also, Steve's schematics shows changing the screen bypass from .005uf to .001uf - I couldn't quite get a clean waveform up to 10khz with that, so I went with 500pf.
   As of right now, I don't have an audio chain capable of line level output, so I'm not putting it on the air yet, but I just ordered myself a DBX 286S and an Audiotechnica AT2020 mic, something I've been meaning to do for a while.  I'd like to start converting some of my other rigs, like my Ranger and B&W 5100B, to use line level input.  I'll probably wind up going with some EQ, too.
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Patrick J. / KD5OEI
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« Reply #80 on: June 25, 2020, 12:42:51 AM »

Audio phase shift is probably due to audio coupling imperfections. The phase shifts according to frequency based on R-C ratios. Just a guess, sans link to Steve's or your schematic.
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KD1SH
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« Reply #81 on: June 25, 2020, 07:48:33 AM »

Sorry, Steve's schematic is way back, many posts ago, at the beginning of this thread.  This one:
Mine follows his, other than my using a 500pf screen bypass, where he shows .001uf.
Yeah, I figured that my point where there's no shift at 400hz is right where capacitive reactance and inductive reactance equal out, with the shift going one way when the reactance is predominately capacitive and the other way when it's inductive.  But then, that's resonance, isn't it?  Resonance at 400hz would involve some pretty big values.


Audio phase shift is probably due to audio coupling imperfections. The phase shifts according to frequency based on R-C ratios. Just a guess, sans link to Steve's or your schematic.


* dx60_screen_modulator.jpg (82.07 KB, 800x390 - viewed 98 times.)
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Patrick J. / KD5OEI
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« Reply #82 on: June 25, 2020, 10:23:29 AM »

My fault, I must have missed that.
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W4RFM
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« Reply #83 on: June 25, 2020, 12:15:09 PM »

First, what great audio on that sample back at the beginning of the thread. Wow.
Has anyone tried this plan with a Knight T-60? The 6DQ6 gonna behave differently?
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BOB / W4RFM  "I have looked far and wide, (I also checked near and narrow)"
KD1SH
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« Reply #84 on: June 25, 2020, 12:18:29 PM »

I've got a Heathkit Seneca 6-meter AM transmitter, also controlled carrier modulated in similar fashion to the DX-60 but with two 6146's in the PA.  I plan to put Steve's mod into that, too.
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« Reply #85 on: June 27, 2020, 01:08:41 PM »


...Has anyone tried this plan with a Knight T-60? The 6DQ6 gonna behave differently?

See Electric Radio Issue #341 October 2017 for improvements.

Phil
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W4RFM
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« Reply #86 on: June 29, 2020, 12:35:00 PM »

So I bought a nice looking T-150 over the weekend, especially to apply the modulation mod. I can't wait to hear this. The 150 even has a 6DR7 as the driver, which is very similar to the 6DE7 used in Steve's drawing. I think I will use a crystal on 3880 or 85 instead of the funky VFO. Yee Haa.
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BOB / W4RFM  "I have looked far and wide, (I also checked near and narrow)"
KD1SH
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« Reply #87 on: June 29, 2020, 02:09:39 PM »

Nice looking rig.  I've passed on a number of those at hamfests over the years, before I gained an appreciation for screen-mod rigs. Now that I know better I'm regretting it.


So I bought a nice looking T-150 over the weekend, especially to apply the modulation mod. I can't wait to hear this. The 150 even has a 6DR7 as the driver, which is very similar to the 6DE7 used in Steve's drawing. I think I will use a crystal on 3880 or 85 instead of the funky VFO. Yee Haa.
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DMOD
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« Reply #88 on: June 29, 2020, 03:27:31 PM »

So I bought a nice looking T-150 over the weekend, especially to apply the modulation mod. I can't wait to hear this. The 150 even has a 6DR7 as the driver, which is very similar to the 6DE7 used in Steve's drawing. I think I will use a crystal on 3880 or 85 instead of the funky VFO. Yee Haa.

I still use mine mainly on 75 meters.

Here are mods I applied for better audio and power control into my amps:

http://amfone.net/Amforum/index.php?topic=34680.0


Phil
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W4RFM
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« Reply #89 on: June 29, 2020, 04:38:53 PM »

Very good information there Phil, Thank you. I have an old heathkit SB-200 (doesn't everybody?) I think 20 watts carrier would be safe into those 572B's don't you?  Or am I missing something?
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BOB / W4RFM  "I have looked far and wide, (I also checked near and narrow)"
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« Reply #90 on: June 29, 2020, 09:30:54 PM »

Very good information there Phil, Thank you. I have an old heathkit SB-200 (doesn't everybody?) I think 20 watts carrier would be safe into those 572B's don't you?  Or am I missing something?

10 to 15 Watts carrier max would be safer I think for an SB-200 with 2 572B's. the weak link in the SB-200 is its Full Wave Voltage Doubler power supply.


Phil
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KD1SH
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« Reply #91 on: July 07, 2020, 12:26:03 PM »

   Well, I've had the modified DX-60 on the air, and the results were even better than I'd hoped.  The first time, I'd been listening on a popular local frequency, jumped in with a quick comment, and one of the regulars replied, "Who's the station with the really smooth audio?"
   Another time I got, "That's a DX-60?!"
   Now I'll be on the lookout (assuming we ever have hamfests again) for other screen modulated rigs to try this on, like maybe a Knight T-150 or something like it.  Heck, I might even homebrew my own screen modded rig.
   Thanks again to Steve for this awesome mod!
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Steve - K4HX
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« Reply #92 on: July 08, 2020, 06:23:07 PM »

Sweet! Makes the work worth when you get compliments like that.   Smiley
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KD1SH
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« Reply #93 on: July 08, 2020, 07:28:50 PM »

  And it really reinforces the magic of AM - of tinkering and modding and building - if I was running a modern store-bought rig right out of the box, a Yaesu or Icom or something, the compliment would still have been welcome but would have rung a bit hollow.  Sure, it's Steve's mod, I didn't design it, but I bought the old rig at a hamfest, recapped and re-tuned it, put Steve's mod into it, and put together the audio-chain - now there's a personal connection to it that you just can't get by taking a brand-new Yaesu out of a box. I think that's why most of us are here.

Sweet! Makes the work worth when you get compliments like that.   Smiley
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« Reply #94 on: July 15, 2020, 06:24:21 AM »

Hi Bill,

Wow!  Looking forward to hearing that modified rig on the air from the "quiet corner" of Connecticut   Smiley
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