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Alexander, DL4NO's avatar

23cm: This shows how important political representation of ham radio is! Finnish hams lost the 23cm band completely last year. In Scandinavia (SM, OZ, LA, OH) the 70cm band has been only 6 MHz wide for a long time, including the ISM band. The Scandinavian hams must operate their relays with 1.6 MHz offset, partly up and partly down. Many relay input frequencies are in the ISM band :-(

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Alexander, DL4NO's avatar

@AF7SJ: I did not talk about standard VoIP acros the Internet. I did talk about radio services like DMR, linked through massive digital networks over the Internet. In this environment, delays during a hand-over easily add up to several seconds.

The delays start with the codecs that need a certain number of samples before they can start to compress speech. The RF transmission uses time-domain multiplex (TDM), adding another few ms. This all happens in front of the VoIP transmission. Then we need the hand-over procedure that needs to flush all buffers. Then follows another TDM RF transmission. At the receiver you need a buffer to mask Internet and RF delays - this buffer must be filled before its output can be used.. Finally another codec delay.

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