Our Temple Texas ARC owns an Ericsson M3 2M repeater with 3 remote site voting receivers using GE Phoenix mobiles for 438 Mhz voting receiver link radios. We had lots of trouble with cheap ham radios chopping on voice peaks for several reasons.
Ericsson's philosophy is to use Channel Guard to prevent unwanted signals from activating the repeater. They use dsp in the system module to decode the Channel Guard tone. Ham talkies and mobiles chopped pretty badly. Commercial radios did not. I found first of all that most off the shelf talkies, Icom W32, Yaesu, etc generally had peak deviation set at +/- 6.5 Khz using voice modulation and either my HP8921 or COM 120B to measure. Another generalization, ham equipment uses tone and digital coded squelch as an after thought. No voice band filters the remove voice components below 300 hz. From the modulator causing the voice modulation low frequency components to compete with Channel Guard tones. Add to this a little excessive transmitter deviation and the system chops. Ericsson TAC provided a software patch that "AND" ed tone and carrier squelch so that once tone was detected it could drop and as long as carrier squelch was open the repeater would remain open. This patch cured the problem, except on the Phoenix voting receivers. I also find that Kenwood, TKR720's and 750's are much more tolerant of crappy signals. While on my soap box, The Texas VHF FM Society, coordinator for repeaters in Texas recommends a maximum instantaneous peak transmitter deviation of +/- 4.0 Khz. Proper mic input gain and peak deviation limiting goes a long way toward helping choppy signals. Mic Gain and Transmitter deviation are loosely related that in setting up a transmitter, turn the mic gain to max, and set the deviation limiter to say 4.0 Khz. Then reduce the mic gain to taste. Helper used to produce an instrument to measure mic gain, called modulation density - never did catch on. Anyhow, my two cents. Best 73 and Merry Christmas to all, Steve NU5D -----Original Message----- From: Jeff Otterson [mailto:[EMAIL PROTECTED] Sent: Friday, December 24, 2004 3:22 PM To: [email protected] Subject: Re: [Repeater-Builder] Help: GE M2 PL decode dropout on voice peaks and IDA control shelf Most likely, your HT is part or all of the problem. [Steve Bosshard (NU5D)] 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/
