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4.27 - Use with a Transmitter

4.27.1 - Transmit Squelch

Transmit Squelch TXS and associated slider TXS set a dBm level above which SdrDx will automatically mute. Even if your transmit gear mutes your antenna system (as with the Pixel Pro RF-1B) or shorts the receive antenna to ground, odds are that the SDR will still see a very large signal, larger than any you're likely to receive.

So the idea is you set the threshold using TXS to above the signal levels you're receiving, but below the signal level produced when you transmit. Then the SDR will automatically mute whenever you transmit. If the TX Squelch feature ( TXS ) is actively muting the audio, TXS will illuminate.

4.27.2 - Latency

One of the requirements of digital signal processing is that you have to look at a certain amount, that is, a portion of time, of signal reception in order to make decisions about it, perform math on it, and so on. Until that's done, the signal can't be passed on to you to listen to or otherwise made use of.

The time between when the signal arrives at the digital radio, and the time when it is presented at the radio's audio output, is the "latency." Latency can affect certain types of use of the radio, in particular those instances where it is used as the receive portion of a two way radio system.

You can adjust the amount of time SdrDx has to process the information by adjusting the size of the output buffer it maintains; if you make this buffer smaller, you'll hear the results sooner, but in turn, SdrDx has less time to process the data. The faster your machine is, the smaller you can practically make this buffer.

Now, if you do make the buffer too small (I'll tell you how to adjust it next), the audio will begin to sound choppy, with short interruptions. You'll be able to hear it immediately. In that case, make the buffer larger.

The current size is indicated in the upper info box, inside a pair of these: {} The number will be 16, 8, 4 or 2, like this: {4}. The smaller the number, the smaller the output sound queue, and the lower the overall receive latency will be. Remember, if you hear clicks and choppiness, you've made the queue too small (^ S or Left-LAT) for your available CPU power and you should make it larger (^ L or Right-LAT)



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