XV222 Local Oscillator
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The local oscillator on the XV222 will not generate a sufficient
signal level. The voltage measured at TP1 is 0.45VDC. When first tested, TP1 read 0VDC. Seeing posts about a balky oscillator being sensitive to L4A, I adjusted the slug while watching at TP1. Sure enough, as the slug was adjusted, TP1 rose from 0VDC to 4.5VDC and then started back toward 0VDC as I continued to turn the slug into L4A. I backed out the slug until TP1 read its maximum of 0.45VDC and then continued out until the voltage at TP1 returned to 0VDC. When oscillating, the frequency measures at 193.995, which is well within the accuracy of my frequency counter. I checked all components and voltages at Q1 & Q2, everything was correct. I'm sure there are some clues buried in the above observations, but I'm unable to sort them out. Does anyone have any clue as to how I get the voltage at TP1 up over 1.0VDC? PS I know we are suppose to use non-metallic tools to adjust inductor slugs, but L4A is so tight that the adjusting tool that came with the kit is useless, its nylon shoulders promptly rounded off. Having spare slugs, I tried adjusting L4A slug with a thin metal screwdriver. Do we use non-metallic because 1. metallic screwdrivers will physically damage the slug? 2. metallic screwdrivers will magnetize the slug? 3. metallic screwdrivers affect the readings while adjusting? 4. other? I do have spares from L10, L11 & L19, so I can replace the slug if needed. _______________________________________________ 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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Matt Osborn wrote:
> Do we use non-metallic because > > 1. metallic screwdrivers will physically damage the slug? > 2. metallic screwdrivers will magnetize the slug? > 3. metallic screwdrivers affect the readings while adjusting? > 4. other? Mostly 3 and 1. -- "Nosey" Nick Waterman, G7RZQ, K2 #5209. use Std::Disclaimer; [hidden email] I'm a forgotten man in his (Bobby Robson's) mind. _______________________________________________ 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 |
RE: XV222 Local Oscillator
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In reply to this post by Matt Osborn
Matt asked:
The local oscillator on the XV222 will not generate a sufficient signal level. The voltage measured at TP1 is 0.45VDC. When first tested, TP1 read 0VDC. Seeing posts about a balky oscillator being sensitive to L4A, I adjusted the slug while watching at TP1. Sure enough, as the slug was adjusted, TP1 rose from 0VDC to 4.5VDC and then started back toward 0VDC as I continued to turn the slug into L4A. I backed out the slug until TP1 read its maximum of 0.45VDC and then continued out until the voltage at TP1 returned to 0VDC. When oscillating, the frequency measures at 193.995, which is well within the accuracy of my frequency counter. I checked all components and voltages at Q1 & Q2, everything was correct. I'm sure there are some clues buried in the above observations, but I'm unable to sort them out. Does anyone have any clue as to how I get the voltage at TP1 up over 1.0VDC? --------------------------- Is the local oscillator transistor mounted up off the board with a Teflon spacer on one lead as shown in the assembly manual? Ron AC7AC _______________________________________________ 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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On Fri, 24 Mar 2006 14:53:26 -0800, "Ron D'Eau Claire"
<[hidden email]> wrote: >Matt asked: > >The local oscillator on the XV222 will not generate a sufficient signal >level. The voltage measured at TP1 is 0.45VDC. > >When first tested, TP1 read 0VDC. Seeing posts about a balky oscillator >being sensitive to L4A, I adjusted the slug while watching at TP1. Sure >enough, as the slug was adjusted, TP1 rose from 0VDC to 4.5VDC and then >started back toward 0VDC as I continued to turn the slug into L4A. > >I backed out the slug until TP1 read its maximum of 0.45VDC and then >continued out until the voltage at TP1 returned to 0VDC. > >When oscillating, the frequency measures at 193.995, which is well within >the accuracy of my frequency counter. > >I checked all components and voltages at Q1 & Q2, everything was correct. > >I'm sure there are some clues buried in the above observations, but I'm >unable to sort them out. Does anyone have any clue as to how I get the >voltage at TP1 up over 1.0VDC? > >--------------------------- > >Is the local oscillator transistor mounted up off the board with a Teflon >spacer on one lead as shown in the assembly manual? > Hi Ron, Yes, Q1 is mounted 3/8" high with the teflon spacer. I was thinking that the crystal is OK because it oscillates at the correct frequency. How critical is the MPS 918? Could I substitute a 2N2222 in place of Q1 just to check out the operation of Q2 (BFR96)? Is that a sensible thing to do? _______________________________________________ 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 |
RE: XV222 Local Oscillator
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Hi Ron, Yes, Q1 is mounted 3/8" high with the teflon spacer. I was thinking that the crystal is OK because it oscillates at the correct frequency. How critical is the MPS 918? Could I substitute a 2N2222 in place of Q1 just to check out the operation of Q2 (BFR96)? Is that a sensible thing to do? _______________________________________________ You've run flat up against all I know about the L.O. I would suspect a flaky transistor or, possibly, a low-activity crystal. They can be on frequency and still not provide the drive needed. As you probably know, overtone oscillators are finicky things. I'm not the engineer on that project so I can't answer your question about substituting Q1. I'd suggest dropping Gary a line at [hidden email]. He may have dealt with that issue already for someone else! Ron AC7AC _______________________________________________ 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 |
Re: XV222 Local Oscillator
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In reply to this post by Matt Osborn
The local oscillator on the XV222 will not generate a sufficient
signal level. The voltage measured at TP1 is 0.45VDC. When first tested, TP1 read 0VDC. Seeing posts about a balky oscillator being sensitive to L4A, I adjusted the slug while watching at TP1. Sure enough, as the slug was adjusted, TP1 rose from 0VDC to 4.5VDC and then started back toward 0VDC as I continued to turn the slug into L4A. I backed out the slug until TP1 read its maximum of 0.45VDC and then continued out until the voltage at TP1 returned to 0VDC. When oscillating, the frequency measures at 193.995, which is well within the accuracy of my frequency counter. ------------------------------------------------------------------ As I don't have an XV222, I am assuming that the local oscillator is an overtone oscillator. In most overtone oscillators there is a tuned circuit that selects the required overtone frequency, in this case 193.995 MHz, and I am guessing that L4A is part of that tuned circuit. If all the components and DC voltages are OK, the result that you are getting is typical if the tuned circuit cannot be tuned properly. It sounds as though the inductance of L4A is reaching its maximum as you turn the slug in, but not enough inductance is obtained, and as you continue to turn the slug into L4A its inductance starts to decrease again. Another possibility is an out of tolerance capacitor in the tuned circuit which if on the low side would require greater inductance than usual from L4A, and L4A can't provide it. A "maybe" possibility is that the crystal you have is "sluggish" at the overtone used.. If however the LO is an oscillator followed by frequency multipliers and L4A is in one of the tuned circuits, then what I said about the position of the L4A's slug and the capacitor tolerance would also apply. Metal tuning tools are a no no when the tool must connect with the slug. Very easy to break slugs and the tool has its own effect on tuning by just being near or in the coil. Hope that this helps. 73, Geoff GM4ESD _______________________________________________ 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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