We are attempting to define an audio level setting procedure for the Asterisk/app_rpt internet linking project. (See www.zapatatelephony.org).
All analog audio is converted to signed linear PCM in our controller; even the local repeater receiver to transmitter audio path is digital. Since the links are digital and there should be little difference between nodes, but standardizing on a common reference level will allow us to set audio levels on all nodes consistently, and to have similar audio levels between nodes. We just added some code to app_rpt to implement a control operator command to generate a -10dbm 1004Hz (in signed linear PCM format) test tone digitally. Our proposed procedure is to do the following: 1. Disable any TX CTCSS source. 2. Turn on the tone generator, and crank the tx level pot on the repeater interface all the way up. 3. Adjust the transmitter deviation pot for a hard limit on peak deviation at 5KHz. 4. Back off the tx level pot on the on the repeater interface until it reads 3KHz (60% of full deviation). 5. Turn off the tone generator. 6. Apply a 1KHz tone frequency modulated to 3KHz on the repeater receiver. (No CTCSS is preferable, but the codecs attenuate all frequencies below 300 Hz and with a low PL tone we don't see much difference). 7. Adjust the rx level pot until we see 3KHz peak deviation on the repeater transmitter. Does anybody see any problems with this approach? Steve WA6ZFT On Saturday 29 January 2005 00:39, bradley glen wrote: > Hi > > I do not think there is a standard accross all radio > systems. > My experience comming from a telecommunications/ > microwave background I still use 600 Ohm feeds to my > repeaters. > My standard is -10 dbm for 60% system > deviation(excluding PL)Remember PL tones are generally > attenuated due to the standard telco spec of > 300-3400hz band pass-anyfrequency outside of this is > not guarenteed.This stems from the old analog > multiplexed systems where guard bands were needed to > elliminate crosstalk. > The reason is simplicity and generally before each > inpur/output I have balanced pads so I can use my audi > test units accurately. > Most commercial systems have a wide manual setting > allowing the user to chose their own standard. > > Perhaps mention what make of system you are putting > together. > > Most of my uhf linked systems are all 600 / balanced > and uniform. > > If you are going this route remember to be careful > between terminated /unterminated reading-difference of > 6dB . > > Regards > > Bradley Glen zs5WT node:8300 > UHF linked repeaters linked on UHF.(Naturn) > > --- [EMAIL PROTECTED] wrote: > > When connecting a transmitter and receiver to a TDM > > circuit with E&M termination, what is the TX > > deviation setting for 0DBm of drive at 1004Hz? > > > > Most TDM circuits will go to +5dbm before clipping, > > so is this extra headroom into account, or is 0DBm > > supposed to generate 5KHz of deviation at 1004 Hz? > > > > Thanks, > > > > Steve > > WA6ZFT > > > > > > > > > > > > > > > > Yahoo! Groups Links > > > > > > [EMAIL PROTECTED] > > __________________________________ > Do you Yahoo!? > Yahoo! Mail - Find what you need with new enhanced search. > http://info.mail.yahoo.com/mail_250 > > > > > > Yahoo! Groups Links > > > Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
