Audio issue

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  • Updated 5 years ago
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After setting up DAX and getting it to somewhat work I noticed if I disable the transmit of the slice the receive noise was louder but I noticed no change in the signals on the meter though there was a significant difference in the audio output.

As I was reviewing the video on setting up DAX I have to wonder what the slider next to DAX on the transmit panel does. In addition, I noticed in the video when transmitting the RF power slider was never moved off zero yet from my experience you have to move the RF power off zero. AT one time it was said to set your power to 100% and then adjust the the audio so you did not exceed 0db on the level meter. So which is the correct way of adjusting the power out?

It sure would be nice to be able to monitor your output in the digital modes.
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Don - kx9q

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Posted 5 years ago

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Tim - W4TME, Customer Experience Manager

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"After setting up DAX and getting it to somewhat work I noticed if I disable the transmit of the slice the receive noise was louder but I noticed no change in the signals on the meter though there was a significant difference in the audio output"

All of the audio streams are "normalized" as the audio gain is distributed across all audio output sources. It is the same effect if you have multiple slices open and mute them. This is not a defect.

"As I was reviewing the video on setting up DAX I have to wonder what the slider next to DAX on the transmit panel does. In addition, I noticed in the video when transmitting the RF power slider was never moved off zero yet from my experience you have to move the RF power off zero. AT one time it was said to set your power to 100% and then adjust the the audio so you did not exceed 0db on the level meter. So which is the correct way of adjusting the power out?"

This was a demo done in the lab and the power level was reduced for demo proposes only. Whether you set you power at 100 and reduce the audio gain or set you audio gain for 0 dB and reduce the RF Power level to your target output, it really make no major difference in which option you choose. Both ways are correct.

I personally set the audio input for about - 3 dB on peaks and reduce the drive level down to my target output because I use different digital modes that have different power output recommendations (PSK vs. RTTY) and changing just the RF Drive is a little more convenient that changing the audio input gain setting since it is right there on the TX control panel rather than on the DAX Control panel.
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Robert -- N5IKD, Elmer

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Tim - W4TME, Customer Experience Manager

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Thank you, Robert!
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Don - kx9q

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Thanks. I had mine set at -3db though I am not sure how it functions. From the fldigi manual:

"It is often difficult to adjust the audio drive for the point where ALC is just barely active. Mixer controls are OK, but
not usually designed for very small changes. They are after all designed for adjusting listening levels. fldigi provides
the ability to control the audio drive in increments of 0.1 dB over a 30 dB range. This control is located in the bottom
right corner of the main dialog:
Set this control for -6 dB and then adjust the sound card mixer control for the best ALC level you can achieve. Then
adjust the Tx-level control for best "just visible" ALC on the transceiver. That should give you a very clean PSK
signal.".

There is no ALC so please enlighten me. I am sure it is clear but for the life of me I am confused.
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Tim - W4TME, Customer Experience Manager

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OK. This statement was written for analog/DSP radios, not SmartSDR. Do not drive the input signal very near 0 dB as any excursions beyond 0 dB will enable the ALC algorithm to cut back the audio input gain.
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Don - kx9q

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Ok, I assume you mean do not drive the "level" too near to 0db which is what I have been doing. Now I am trying to understand what impact setting fldigi to -3db has.
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Vern

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Did you say there is or is NOT a way to monitor, for instance, the PSK audio to help determine if distortion is present.

Vern
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jim WB5AAA

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so Vern, how do we monitor PSK,CW,RTTY when using Fldigi
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Don - kx9q

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I would think for now you would need to have a second radio to monitor your output in the digital modes.
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Greg

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I always ask the person I am having a so with. I find simply keeping the audio peaks a few dB below zero does the trick to keep a clean signal.

73
Greg
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Don - kx9q

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Greg, what are you looking at when you say you keep audio peaks a few db below zero? The "Level" bar meter doesn't provide that type of granularity unless you mean you just keep peaks below 0db or are you referring to the meter in the DAX control panel which also doesn't have much granularity.
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Greg

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On the Level Meter just above the compression meter.
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Don - kx9q

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Ok, that is what I am doing.
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Greg

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I'm not that familiar with Fldigi but I'm sure it's some kind of fine tuning but remember that it's what shows on the smart SDR display that counts ... that's what's actually going over the air not what Fldigi says.
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Don - kx9q

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I was curious since Tim mentioned it and like they say about the internet if he says it it must be true. Just kidding. I am out in San Jose for a week so no radio until I get back next week.