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Mic distortion
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I have not used a linear with my uBitx, however the OCFD that I have from MFJ has a lot of RF on the shield.? This got back into the mic, and caused a significant amount of distortion.? You may have the same issue, as it seems that the uBitx audio is susceptible to RF.? I would suggest shielding and ferites on the mic cable.? Could also try a snap on ferite over the coax between the uBitx and linear.
Just suggestions, again, I do not have any experience using a linear to go on. 73 Evan AC9TU |
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I use a balanced antenna and I don't have that issue. If your antenna is unbalanced, you may consider the MFJ-815 line isolator. Or a coax choke around a ferrite core with a material like 43, NiZn permeability around 800. Il 26/mar/2019 18:08, "Sam Tedesco" <stedesco619@...> ha scritto: Hi everyone, any ideas on cleaning up the mic distortion when using a linear? I tried turning rv1 down to a few watts out on 40 but still distorting. I really don't want to affect the cw power. I thought about bring rv1 to the front panel...but, thinking against it now. Ideas? |
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Btw which amplifier are you using as that might add distortion too. Il 26/mar/2019 18:40, "iz oos" <and2oosiz2@...> ha scritto:
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How far is the antenna from your shack? I am asking this as a friend was complaining about his AV640 because RF in the shack. He did add an RF isolator an nothing changed. The antenna was on the roof but the shack was just too close to it. There was nothing wrong with the antenna itself. Il 26/mar/2019 20:33, "Evan Hand" <elhandjr@...> ha scritto: I was just pointing out to SAM that RF getting back into the mic circuit will cause distortion, and that the uBitx seems to be very susceptible to that issue? Since the questions started with using a linear with the uBitx, I thought that RF feedback could be an issue. |
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Is the problem only with the amp connected?? How is the signal running "barefoot".
Since you have another receiver, I would load the uBitx without the amp into a dummy load and verify the signal with your Kenwood.? If that does not have the distortion, then would check the linearity of the amp or the SWR between the uBitx and the amp. I also had issues with distorted audio when I had a miss adjusted BFO.? Put the output right on one of the edges of the filter, causing high frequency cut off on one end, and excessive carrier on the other. I have read some posts where multiple pots with relays were used to adjust the drive setting based on band selection.? As long as you shielded the connections with appropriate RF cables, I would think that you could have a switch with a resistor/pot to change value of drive. Again, these are my experiences and ideas, yours may be different. 73 Evan AC9TU |
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The 0.001 mfd bypass at the microphone cartridge was sort of standard way back in the early days of BITX.? It worked then, so should be something to try now. Arv _._ On Tue, Mar 26, 2019 at 4:41 PM Martin Potter <ve3oat@...> wrote: I wonder if an RF by-pass capacitor (disk 0.01 uF) at the mic connector would do the job.? Anyone tried that? |