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Post by Marc on Apr 28, 2010 16:15:29 GMT -5
Well the 2000 project keeps hitting a snag. This time the counter reads correct on RX but actual freq is about 1.5 KHz's high go figure.
Any body got an idea??
Marc
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Sandbagger
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Post by Sandbagger on Apr 28, 2010 17:58:16 GMT -5
Well the 2000 project keeps hitting a snag. This time the counter reads correct on RX but actual freq is about 1.5 KHz's high go figure. Any body got an idea?? Marc What do you mean by "actual freq"? Is that what you measure with an external couner on transmit? Does the internal counter and external counter agree when you transmit, but is 1.5K off from receive, or does the internal counter drop 1.5Khhz when you transmit? It's possible that if the receive and transmit freqs are off, that there's a clarifier synchonization issue, which can happen if someone unlocked the clarifier incorrectly, or the 8V regulator is not holding steady |
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Post by Marc on Apr 29, 2010 9:04:22 GMT -5
The TX tracks correctly and matches my external counter.
CORRECTION low
On RX the internal counter reads the frq of the channel selected
but in actuality it is 1.5KHz LOW had to tune up (Ch 20 reads 27.2050 but is actually 27.2035)
sorry was not thinking strait.
Marc
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Post by Tombstone (R.I.P.) on Apr 29, 2010 10:10:31 GMT -5
I'm thinking along the lines like Sandbagger suggests. I too was thinking that if the clarifier is unlocked improperly, that could be the problem. You might be able to touch up the VCO adjustment but I think that will show the change on the internal counter. This is getting into the gray area of my expertise, so I would let Sandbagger try and guide you in the right direction. Do check the regulator and see if it holds the proper 8 volts, if not, that can cause all kinds of weird symptoms. Has the radio been modded for exrta channels? If so, that might be a problem. Make your tests and any adjustments on channel 20 in the regular 40 channel band. That will tell you if the channel mod is the culprit or not. Could be a bad capacitor in the PLL circuit or the internal counter is somehow faulty if an external counter reads correctly. I wish I could help you more.
Tombstone
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Post by Marc on Apr 29, 2010 10:53:51 GMT -5
Thanks see correction in my post above
Will be sending it to Barketts
Marc
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Sandbagger
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Post by Sandbagger on Apr 29, 2010 14:07:53 GMT -5
The TX tracks correctly and matches my external counter. CORRECTION low On RX the internal counter reads the frq of the channel selected but in actuality it is 1.5KHz LOW had to tune up (Ch 20 reads 27.2050 but is actually 27.2035) sorry was not thinking strait. Marc I'm curious how you were able to determine exactly where your receiver was tuned on AM? It's hard to really see a 1.5 Khz error. On SSB it's a different story, is that where you saw the error? If it's only on AM I would check the 2nd mixer crystal 7.345 Mhz, to make sure it's not off. If all the modes are off, then there is probably a clarifier synchronization issue or something in the counter circuit which compensates for the carrier offset so the counter reads correctly on all modes. |
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Post by Marc on Apr 29, 2010 16:36:13 GMT -5
I used a low output from my sig gen just enough to get about 4 s units With no mod then tuned the clarifier to the peak then hooked my external freq counter to the radio and verified the TX output with the internal counter
RX before peak 27.2050 after peak 27.2065 1.5 KHz's
TX 27.2065 on both counters
TX with out peak 27.2050 both counters
When lessening to other stations on the air I also have to tune up 1.5 to here them clearly. so 1.5 low
Marc
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Sandbagger
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Posts: 6,247
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Post by Sandbagger on Apr 30, 2010 7:49:00 GMT -5
I used a low output from my sig gen just enough to get about 4 s units With no mod then tuned the clarifier to the peak then hooked my external freq counter to the radio and verified the TX output with the internal counter RX before peak 27.2050 after peak 27.2065 1.5 KHz's TX 27.2065 on both counters TX with out peak 27.2050 both counters When lessening to other stations on the air I also have to tune up 1.5 to here them clearly. so 1.5 low Marc How about SSB? Is your transmit and receive synchonized? If it's only on AM that you have the issue, it may be simply an IF alignment issue, or the 2nd mixer crystal that's a little off. Unfortunately, there's no trimmer to adjust it, but you can use a freq country to see if the oscillator is running at 7.345 Mhz |
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Post by Marc on May 3, 2010 9:57:07 GMT -5
Well
After more time spent SSB is also off so it will go to barketts later this month.
Marc
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Post by Timekeeper on May 4, 2010 18:57:08 GMT -5
The implied question wasn't asked - Is the clarifier unlocked? If it isn't, then the fix is just a quick and easy adjustment. There is a transmit frequency adjustment pot, in the front of the radio, I forget the pot number. Easy to find on line. Also, is the internal counter accurate? If not, then there is a trimmer cap in the counter for that, although it's a pain to get it right on as your hand being near it can cause it to be read off.
So - if not opened clarifier, then check internal counter accuracy by transmitting and comparing the displayed freq. with a good external counter. Adjust the counter trimmer cap. Then adjust the VR for transmit so that it agrees with the receive freq., then adjust the 3 transformer cans so it's all on frequency.
In fact, even if it is an opened clarifier, this may still just need a simple alignment.
Or, you can just go ahead and send it out, but think of the fun you'll be missing....
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Post by Marc on May 5, 2010 9:25:02 GMT -5
I would say the clarifire has been exspaded but not unlocked(tuning the clarifire moves both tx and rec the same amount)
I think that is vr5 or 6 But that is just for am is it not.
The ssb is off also
thanks
Marc
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Sandbagger
Administrator/The Boss
Posts: 6,247
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Post by Sandbagger on May 6, 2010 7:13:27 GMT -5
I would say the clarifire has been exspaded but not unlocked(tuning the clarifire moves both tx and rec the same amount) I think that is vr5 or 6 But that is just for am is it not. The ssb is off also thanks Marc Unlocked = The transmit and receive move together synchronously. Locked = The transmit remains at center slot, while receive moves with the clarifier. Expanded = The range of the clarifier is greater than the stock configuration. Normally a standard radio clarifier moves about +/- 1.5 Khz. Expanded radios generally move greater than +/- 5 Khz. The transmit freq pot moves the transmit frequency in all modes, but if the clarifier has been (properly) unlocked, that pot should have no effect. It's possible that the unlock mod was performed incorrectly and that could be the root of your whole problem. |
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Post by Marc on May 6, 2010 14:24:16 GMT -5
OK than unlocked and expanded
up about 5kHz down a little over 10 KHz the old A channel drop
Will check the vr when I get home.
Marc
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