FW: How to set up SSB
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Another idea.
Why not some sort of RF-probe circuit? It would look just like the RF probe in the book, but with different component values to get the time constant down. The RF probe in the book gives about a 100 Hz bandwidth which isn't enough (I'd want at least 5K for SSB audio testing). It seems different values might make this work (For SSB only, no BFO for CW). However, I can't seem to get a decent audio signal off the top of my dummy load. I've tried a bunch of different RC combinations, but I believe I also need a blocking capacitor on the output. I'll continue to fart around with the junk-box parts, but someone with a bit more depth of knowledge might grap a calculator and drop in the values of the parts I'd want. Ant --- Cap (0.01) ----------- Cap (2) --- headset | | | diode R (5M) | | | | Ground ---------------------------------------- Of course, maybe my audio IS that bad, and this detector is working fine! Dan / WG4S / K2 #2456 -----Original Message----- From: John Magliacane [mailto:[hidden email]] Sent: Thursday, November 11, 2004 4:58 PM To: Dan Barker Subject: RE: [Elecraft] How to set up SSB Hi Dan. > The simple reciever sounds fun. Any ideas what besides a 9v battery and a > crystal I might need? I made one once (for the actual purpose you are describing) using 2 MPF-102 FETs and a low-noise OP-AMP (LF351). I built the thing on a protoboard. The oscillator (I used a crystal inside the 160 meter band) was a Colpitts design (common drain). The source of the oscillator fed the source of the second MPF-102 that served as the mixer. The gate of the mixer was fed by a parallel resonant circuit (tuned to the 160 meter band). The drain had a resistive termination -- something like 1500 ohms to the + end of the power supply (a 9 volt battery). This was capacitively coupled to the op-amp. I don't recall what voltage gain I had the op-amp set for, but I had no trouble driving a pair of hi-fi headphones. Someday I'll toss something like this together again. I used this receiver to run transmitter frequency response plots on my K2 last year, and after making some changes to my KSB2 board, I'd like to do it again to compare the results. There's a way to monitor your TX audio through the K2 itself, (go to CAL -> SSB BAL, and talk into the mic), but I think it bypasses the crystal filter in the KSB2, but GOES THROUGH the post IF amplifier filter (which plays no role in your TX audio response). I sometimes monitor my signal using a Grundig YB-400 portable shortwave receiver, but the DC receiver is by far the best way to get an honest on-air sample. 73, de John, KD2BD ===== Visit John on the Web at: http://www.qsl.net/kd2bd/ __________________________________ Do you Yahoo!? Check out the new Yahoo! Front Page. www.yahoo.com _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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Hi Dan.
> Another idea. > > Why not some sort of RF-probe circuit? It would look just like the RF probe > in the book, but with different component values to get the time constant > down. The RF probe in the book gives about a 100 Hz bandwidth which isn't > enough (I'd want at least 5K for SSB audio testing). This will only work for AM signals (full carrier, and at least one sideband), not suppressed carrier SSB. My guess is that even if you were to throw your balanced modulator WAY out of balance, it still would provide poor and confusing results due to the carrier attenuation provided by the crystal (sideband) filter. A simple, low gain, direct conversion receiver (oscillator, mixer, audio amplifier) will provide the necessary carrier injection (BFO) for proper audio demodulation. 73, de John, KD2BD ===== Visit John on the Web at: http://www.qsl.net/kd2bd/ __________________________________ Do you Yahoo!? Check out the new Yahoo! Front Page. www.yahoo.com _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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Hey, I just figured that out. 20K and 0.01 detect fine at a decent
bandwidth, but it's output is average envelope power. You are absolutely right that I'm detecting AM. It sort of sounds like a voice when I talk, but when I whistle, it's just a constant 3v out. Not gonna work without an oscillator. I must have known that because I said it wouldn't work for CW, but I just had to try. Thanks anyhow. Dan -----Original Message----- From: John Magliacane [mailto:[hidden email]] Sent: Friday, November 12, 2004 10:22 AM To: Dan Barker; Elecraft Subject: Re: FW: [Elecraft] How to set up SSB Hi Dan. > Another idea. > > Why not some sort of RF-probe circuit? It would look just like the RF probe > in the book, but with different component values to get the time constant > down. The RF probe in the book gives about a 100 Hz bandwidth which isn't > enough (I'd want at least 5K for SSB audio testing). This will only work for AM signals (full carrier, and at least one sideband), not suppressed carrier SSB. My guess is that even if you were to throw your balanced modulator WAY out of balance, it still would provide poor and confusing results due to the carrier attenuation provided by the crystal (sideband) filter. A simple, low gain, direct conversion receiver (oscillator, mixer, audio amplifier) will provide the necessary carrier injection (BFO) for proper audio demodulation. 73, de John, KD2BD ===== Visit John on the Web at: http://www.qsl.net/kd2bd/ __________________________________ Do you Yahoo!? Check out the new Yahoo! Front Page. www.yahoo.com _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by John Magliacane
On Fri, 12 Nov 2004, John Magliacane wrote: > Hi Dan. > > A simple, low gain, direct conversion receiver (oscillator, mixer, audio > amplifier) will provide the necessary carrier injection (BFO) for proper > audio demodulation. You can likey throw together a "pixie" style rx in less than 20 minutes out of almost /any/ junkbox. If you want something more fun, a Small Wonder Labs Rock-Mite for $25 can't be beat :). _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by John Magliacane
Finally, success!
I got on QRZ and found a ham one mountain over. We got on 12 meters and checked out USB and LSB and he said it sounded like I was on the telephone. I guess that's gonna have to do! Being at the "factory" width for the KSB2, we're not going to get studio audio. In summary, the Radio Shack 270-090 ($2.99) element goes into the MH-2 fine (my Heil element was shorted). The KSB2 sounds "horrible" if you set up FL1 for 2.2 (Thanks Jim - I really feel like Homer Simpson). Use OP1. Spectrogram makes the rest duck soup! Dan / WG4S / K2 #2456 _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by Dan Barker
The option of OP1 or 2.2, etc in the filter selection is for receive only.
However you still have to make sure that the BFO is place correct for the TX filter OP1 and the easiest way to do that is to set up with OP1 in FL1 on receive as was finally selected and match the BFO to that with Spectrogram. Otherwise the BFO can end up in totally the wrong place with adverse effects on the SSB TX audio. Unless this is a very recent KSB2, a good improvement to the SSB audio could be made by applying the KI6WX 2,2 or 2.5kHz modification to the KSB2. The BFO again would need resetting to match the new filter parameters. Believe Elecraft have now adopted the KI6WX 2.2kHz mod as standard on present KSB2 kits. An added benefit is that the filter passband ripple appears to be substantially reduced. I did the 2.2kHz mod and find the final result at about 2.3kHz bandwidth with very little passband ripple. All makes for a better sounding K2 on SSB TX. Bob, G3VVT _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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Well, you made me think, but it turns out, you are right. The CAL FIL
display says "t" for the 2.20 setting, but it's really using OP1. However, with the alignment done on 2.20 and transmit done on OP1, the filter will be very off, and the ripple is extreme. My 2 year old KSB2 seems OK in the flatness department. Dan / WG4S / K2 #2456 Bob (G3VVT) sez: The option of OP1 or 2.2, etc in the filter selection is for receive only. <snip> _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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Dan,
The 't' is on the BFO display corresponding to FL1 - and its only meaning is that this is the BFO (carrier) frequency that will be used for transmit. 73, Don W3FPR ----- Original Message ----- > Well, you made me think, but it turns out, you are right. The CAL FIL > display says "t" for the 2.20 setting, but it's really using OP1. However, > with the alignment done on 2.20 and transmit done on OP1, the filter will > be > very off, and the ripple is extreme. > > My 2 year old KSB2 seems OK in the flatness department. > _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by G3VVT
A mod kit of caps (SSBCAPKT) and downloadable instruction sheet are now
available ($15) for John's SSB mod via our parts and mod kits order form. See: http://www.elecraft.com/order_form_parts.htm The Crystal Filter Bandwidth Modification capacitor kit provides two options to change the original 2.1 kHz -6 dB bandwidth of the KSB2 SSB filter to either 2.4 kHz or 2.6 kHz. (Note: All KSB2s shipped after July 12, 2004 now include the 2.4 kHz bandwidth components.) They are intended for those who wish to optimize its performance to their personal preferences. 73, Eric WA6HHQ ------------------ > > _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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