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Post by Deleted on Mar 4, 2017 16:52:37 GMT -5
I went to align this receive which seems to be the easiest of procedures I have even come across. I did it by the book.
So the receive is dead. I knocked it out. I then realize that the cans have an upper core and lower core. I adjusted the upper core. At this point, I need to start from scratch. How do I adjust 2 cores in the cans, when the procedure only lists one can?
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Sandbagger
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Post by Sandbagger on Mar 4, 2017 19:21:38 GMT -5
I went to align this receive which seems to be the easiest of procedures I have even come across. I did it by the book. So the receive is dead. I knocked it out. I then realize that the cans have an upper core and lower core. I adjusted the upper core. At this point, I need to start from scratch. How do I adjust 2 cores in the cans, when the procedure only lists one can? You need a special alignment tool that has a skinny shaft that allows you to slide through the top slug and grab the bottom one. Then you just peak them both. |
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Post by Deleted on Mar 4, 2017 19:54:44 GMT -5
I went to align this receive which seems to be the easiest of procedures I have even come across. I did it by the book. So the receive is dead. I knocked it out. I then realize that the cans have an upper core and lower core. I adjusted the upper core. At this point, I need to start from scratch. How do I adjust 2 cores in the cans, when the procedure only lists one can? You need a special alignment tool that has a skinny shaft that allows you to slide through the top slug and grab the bottom one. Then you just peak them both. I just put it on its side and did it from both ends. I peak both, correct? For whatever reason, and I use the generators, it is not working right. I am peaking by listening to a QSO and peaking their audio. My 455 KHz generator is right on the money. I am using a second CB with low output power on a dummy load to generate the CB freq. The freq was verified. |
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Sandbagger
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Post by Sandbagger on Mar 4, 2017 22:37:57 GMT -5
You need a special alignment tool that has a skinny shaft that allows you to slide through the top slug and grab the bottom one. Then you just peak them both. I just put it on its side and did it from both ends. I peak both, correct? For whatever reason, and I use the generators, it is not working right. I am peaking by listening to a QSO and peaking their audio. My 455 KHz generator is right on the money. I am using a second CB with low output power on a dummy load to generate the CB freq. The freq was verified. I don't usually bother tuning the IF with the generator set to 455 KHz. I usually just set the generator to the CB channel frequency and tune it up there. Before you do that though, you have to make sure the oscillators are all on frequency. If they are, then everything should line up fine just pumping in the channel frequency. One mistake some people make is peaking the IF's on an unmodulated carrier for highest signal on the S meter. Doing that usually results in distortion to a modulated signal. I usually use an 85% 1 KHz modulated signal, with the scope connected to the detector or audio stage, and adjust the IF's so the signal is strongest and sine wave is clean and the symmetry is correct. In order to get the cleanest sinewave, the IF may have to be detuned slightly from the strongest signal peak. That won't affect the sensitivity all that much, and the audio will sound clean and not "shattered". In order to see a clean sinewave without a ton of noise riding on it, you will have to up the generator output to about 10 or 15 uV to make the final adjustment. Note that this technique only applies to the IF. The RF section coils should be peaked for max signal with the generator set at the minimum level that can show signal deflection on the S-meter, or audio voltmeter, if you have one. On some rigs, the front end coil can sometimes show more noise on one side of the signal peak than the other, and I tune it slightly off the peak on the less noise side. The signal/noise ratio is usually better that way. |
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Post by Deleted on Mar 5, 2017 12:04:42 GMT -5
Wow! That worked great! The receive sounds great!
Do you do that often, skipping the IF and going right to 27 MHz? For both tube and transistor?
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Sandbagger
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Post by Sandbagger on Mar 5, 2017 14:30:51 GMT -5
Wow! That worked great! The receive sounds great! Do you do that often, skipping the IF and going right to 27 MHz? For both tube and transistor? I've done it that way, since I realized that it really doesn't make any difference. The main reason to align the IF with 455 KHz (or whatever freq the IF is tuned for), is to make sure the IF is peaked at 455 KHz. If you use the CB channel frequency and the L.O. frequencies are off, then you won't be tuning the IF at the right frequency. But if you make sure the oscillators are on frequency, then it won't make a difference. The absolute best way to tune an IF is with a sweep generator. That way you can tune for the proper passband. But not too many people have a sweep generator, which is why I tune for sinewave symmetry with conventional generators and the scope. |
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Post by 2600 on Mar 5, 2017 21:50:19 GMT -5
Has a lot to do with the design of the radio and the condition, both.
If it has a ceramic filter, you're stuck with peaking the IF coils to match the frequency of the filter.
For a radio like a Browning, that uses ONLY those IF transformers for selectivity, you won't typically find any of them terribly far off the proper peak setting unless someone has applied a golden scredriver. Only in the most extreme case of tweakeritis do I find it necessary to feed 455 kHz into the radio directly.
More often, feeding 455 kHz into the radio is used as a troubleshooting tool for a dead radio. But if the radio has been horribly screwdrivered, you might find it worth doing.
73
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