Re: Motorola fixed ctcss level Motorola likes the 600 to 700 Hz ctcss deviation level. One cute trick to use for setting re-rocked MSR (and probabaly Micor) tx channel elements is to target the above mentioned ctcss 650 Hz level as your initial ctcss deviation channel element start or setpoint.
What I mean is the ratio of channel element ctcss to voice audio dev. remains similar so if you preset the ctcss to the expected devitation the voice deviation will be fairly close to a desired max value. In most cases the overall channel element voice max deviation value is pretty much near/in the right ball park. Place the re-rocked channel element on frequency, set the ctcss to 650 Hz and the stock MSR-Repeater max deviation is probably pretty darn close to what it should be. If you've ever looked at the typical MSR Channel Element hard limit... you know it's not a pretty sight... nor is it anywhere close to being symetric. So I don't use/rely on the channel element for my deviation limit function. But most people do things the standard Motorola method and the above ctcss "trick" is handy to know. **** My perference is to set tx ctcss down near the 500 Hz deviation level. Note this is not the composite non-voice modulated value, which is the ctcss (sub tone) plus any noise on the tx signal. Many un-modulated carries have a bit of included unwanted noise or hum. [sidebar blurb] I sourced a lot/most of the above unwanted base hum/noise in one of my MSR Trunking Repeater Conversions to the use of a lesser quality cable/wire. I was out of the famous black Motorola repeater/remote cable and used some decent generic sheilded cable in place. Well... no cigar... I could see the direct results as quite a bit of noise (200Hz dev) on the un-modulated tx signal. Hence the main reason I found the original Motorhead black wire mfgr, became a dealer and ordered a 5K spool right away. Replacing the good wire with the better wire removed the noise/hum. So I've been sold on using the black wire ever since (and of course I now stock it). [end of sidebar blurb] Onward... Most every decoder I've tested will track a decent signal down to 100 or 200 Hz ctcss deviation. Some of the older radios (like the Icom IC-02at & IC-04at portables) don't have much of a ctcss filter... so hot sub tone deviation is a pretty bad hum in the normal speaker audio. I/we have not had any decoder drop/false problems using 500 Hz deviation as our ctcss standard. cheers, skipp > > Commercial radios also used fixed values. The Micor is one > > example of fixed values for tone deviation. > > Chuck > > WB2EDV > "Eric Lemmon" <[EMAIL PROTECTED]> wrote: > Chuck, > > You are absolutely correct! However, the specific resistor value > used for R405 in each MICOR station was deliberately selected to > result in the desired deviation level. Thus, the R405 resistor > value (nominally 33 kohms) varies from one station to the next. > Note 409 on the schematic for the MICOR TLD5320A Exciter states > that "R404 and R405 are factory selected so that Private Line > deviation falls between 500 Hz and 1000 Hz limits."
