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Post by vanlifeson on Jun 9, 2020 14:30:44 GMT -5
I’m curious since this radio does not have a control for noise limiting, if there is some noise limiting built into the radio. And if there is can anyone tell me if there is a component inside the radio that maybe can be changed to lessen the effect of the noise limiting? It seems like it’s clipping incoming signals pretty hard. I wish I could shut it off
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Sandbagger
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Post by Sandbagger on Jun 9, 2020 21:23:12 GMT -5
I’m curious since this radio does not have a control for noise limiting, if there is some noise limiting built into the radio. And if there is can anyone tell me if there is a component inside the radio that maybe can be changed to lessen the effect of the noise limiting? It seems like it’s clipping incoming signals pretty hard. I wish I could shut it off It's common for noise limiters to have a small distorting effect on receive audio, especially weaker signals. But it should not be so bad as to be uncomfortable. There could be a weak tube or an alignment issue that's causing the excessive receive distortion. If you want to "turn off" the noise limiter in the 123b, the diode for it is marked D4 on the schematic. Simply jump the diode out and it will be "off".
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Post by vanlifeson on Jun 10, 2020 13:10:41 GMT -5
Thanks for the reply! The radio is not uncomfortable to listen to, I just rarely use any noise limiting feature on my radios as I don’t like the effect it has on the persons voice I’m listening to. I think people sound much better with it off and I would rather deal with a little more static than have them sound funny to my ears LOL . I was also looking at the schematic trying to figure out why my squelch does not work, but I cannot find the squelch labeled on the schematic. Everything else is labeled, RF gain , fine-tune etc. but not the squelch.
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Sandbagger
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Posts: 6,247
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Post by Sandbagger on Jun 11, 2020 11:46:39 GMT -5
Thanks for the reply! The radio is not uncomfortable to listen to, I just rarely use any noise limiting feature on my radios as I don’t like the effect it has on the persons voice I’m listening to. I think people sound much better with it off and I would rather deal with a little more static than have them sound funny to my ears LOL . I was also looking at the schematic trying to figure out why my squelch does not work, but I cannot find the squelch labeled on the schematic. Everything else is labeled, RF gain , fine-tune etc. but not the squelch. Squelch control is labeled RV3 on the schematic. A common fault for these radios is the loss of the -82V supply that feeds the squelch circuit. The main culprit is a nasty little .1 uF "firecracker" capacitor marked C94. That cap likes to explode when it goes bad, although sometimes it may just open. Also check C95 and 96, as these are the same type of cap and will also go leaky and drag the -82V supply down. Also make sure your PA/CB switch is not dirty.
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Post by vanlifeson on Jun 16, 2020 13:03:32 GMT -5
It's common for noise limiters to have a small distorting effect on receive audio, especially weaker signals. But it should not be so bad as to be uncomfortable. There could be a weak tube or an alignment issue that's causing the excessive receive distortion. If you want to "turn off" the noise limiter in the 123b, the diode for it is marked D4 on the schematic. Simply jump the diode out and it will be "off".
I put a variable resistor across D4. Now I have a makeshift variable noise limiter.
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Sandbagger
Administrator/The Boss
Posts: 6,247
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Post by Sandbagger on Jun 16, 2020 19:23:09 GMT -5
It's common for noise limiters to have a small distorting effect on receive audio, especially weaker signals. But it should not be so bad as to be uncomfortable. There could be a weak tube or an alignment issue that's causing the excessive receive distortion. If you want to "turn off" the noise limiter in the 123b, the diode for it is marked D4 on the schematic. Simply jump the diode out and it will be "off". I put a variable resistor across D4. Now I have a makeshift variable noise limiter. An even better idea!
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Post by 2600 on Jun 21, 2020 22:17:26 GMT -5
I put a variable resistor across D4. Now I have a makeshift variable noise limiter. The higher the resistance value of the control, the better control you'll have. Pretty sure the variable ANL control in the Tram D201 is either 2 Megohms or 5 Megs. The lower the resistance value, the less control you'll have. 73
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Post by vanlifeson on Sept 24, 2020 6:30:04 GMT -5
Thanks for the reply! The radio is not uncomfortable to listen to, I just rarely use any noise limiting feature on my radios as I don’t like the effect it has on the persons voice I’m listening to. I think people sound much better with it off and I would rather deal with a little more static than have them sound funny to my ears LOL . I was also looking at the schematic trying to figure out why my squelch does not work, but I cannot find the squelch labeled on the schematic. Everything else is labeled, RF gain , fine-tune etc. but not the squelch. Squelch control is labeled RV3 on the schematic. A common fault for these radios is the loss of the -82V supply that feeds the squelch circuit. The main culprit is a nasty little .1 uF "firecracker" capacitor marked C94. That cap likes to explode when it goes bad, although sometimes it may just open. Also check C95 and 96, as these are the same type of cap and will also go leaky and drag the -82V supply down. Also make sure your PA/CB switch is not dirty.
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Post by vanlifeson on Sept 24, 2020 6:32:42 GMT -5
So I replaced c94 and the squelch worked for a while then stopped working again. Ugh. Any suggestions? I replaced c94 with another cap and no luck.
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Sandbagger
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Posts: 6,247
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Post by Sandbagger on Sept 27, 2020 16:34:20 GMT -5
So I replaced c94 and the squelch worked for a while then stopped working again. Ugh. Any suggestions? I replaced c94 with another cap and no luck. There are other similar caps (C95 and C96) connected to C94 that are likely also bad. C94 is the one that likes to explode like a firecracker, but the other ones can get leaky and drag the voltage down.
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