At 03:22 AM 07/02/09, you wrote: >Hello, >Was Wondering if anyone had a link to a site that had samples of >talk thru Repeater traffic that would be considered good quality audio ? >Maybe i am expecting too much but any of the ones around here that i >have heard seem either Muffled or very Shrill, Listening on the >input frequency the Audio seems quite reasonable but the Transmit >Audio doesn't sound the same and seems a bit average. >I realize that the Audio will vary due to the normal constraints of >Radio atmospherics but i was hoping for something that doesn't sound >like a very cheap tiny AM broadcast radio >I would be really interested in discovering just how good normal >Analogue speech can sound when it is being passed through something >that is properly setup. >Apologies if this has been answered before, i searched but couldn't >find anything specific. >Any info gratefully received, >Cheers,
Where is "around here" ? From what you are saying it sounds like whomever set up the repeater(s) does not understand de-emphasis and pre-emphasis. From the article at <http://www.repeater-builder.com/tech-info/flataudio.html> ... >Another problem that rears its ugly head unless you know the equipment >you are working on intimately... If you pick off raw (i.e. not >de-emphasized) audio from the receiver discriminator and pipe it into >the microphone jack of a transmitter you will end up with an extra >level of pre-emphasis (commonly called "double pre-emphasis") that >will cause the audio to sound very tinny or shrill (take your home >hi-fi, tune to a talk radio station, center the bass and the treble >controls, note the audio characteristics, then crank the bass control >to minimum and the treble to maximum - and mentally double or triple >the overall effect). On a true FM transmitter you can sometimes >bypass the pre-emphasis network, on a phase modulated transmitter >there is no way around it without adding a de-emphasis network in >front of it to compensate. This is why many repeater controllers >have a built in de-emphasis network that can be jumpered into the >circuit or jumpered out as needed. > >Likewise, picking audio from the receiver after the de-emphasis >network (in some receivers that point is after the volume control and >the audio muting part of the squelch circuit) and piping it into a >true FM transmitter modulator can produce audio with extra amount of >de-emphasis (commonly called "double de-emphasis") resulting in a very >muffled, bassy sound with no high frequencies (same example as above, >but crank the bass control to maximum and the treble to minimum - and >mentally double or triple the overall effect). > >Either of the above two situations is instantly recognizable by an >experienced ear. Mike WA6ILQ
