Brian, I am very familiar with this problem. There are several possible contributing factors:
1. The users speak too soon after keying the mike. 2. The repeater may be slow in responding to incoming PL. 3. The PL frequency may be well below 100 Hz. 4. The PL deviation may be too low (not likely). 5. The radios may not be on-frequency. Let's look at these issues one at a time. 1. In my experience, which covers Ham, commercial, and public safety, the untrained users invariably start speaking at the same instant they press the PTT button. This annoying habit seldom responds to pleading or threats. It sometimes helps if other users are not afraid to rebuke the offenders by responding with a direct instruction: "I'm sorry, but the first part of your transmission didn't make it. Please do not start talking until a half-second or so after you press the PTT button. Try again." The most effective solution was my imposition of MDC1200 coding on all portable and mobile units in the fleet. I set the units for beginning of PTT and a short sidetone beep. Once it became obvious to all users that nothing said before the beep was heard, all users wait for the "pre-beep" before speaking. It took only two weeks or so to "educate" the users! 2. You didn't specify the make and model of your repeater, but some models are simply sluggish in responding to incoming PL, and may also be sluggish in generating the outgoing PL. Some repeaters that use reeds are incredibly slow, but MICOR Vibrasponder and Vibrasender reeds are fairly quick acting. Tone decoders and encoders that use PLL technology can often be optimized by setting the idle frequency carefully so that the lock-up time in minimized. 3. The CTCSS (PL) frequency has a great influence on decode time. The TIA-603B standard specifies that the CTCSS decode time shall not exceed 250ms for tones above 100 Hz. Below 100 Hz, the decode times become much slower; at 67.0 Hz, the maximum decode time is 373ms. A third of a second is an eternity to some people. So, using higher frequency PL tones will usually speed up the process. 4. The standard CTCSS deviation specified in TIA-603B is 500 Hz. Most commercial radios have this parameter set in the 650-800 Hz range, and this is fine. The majority of repeaters and portable or mobile radios I work with are responsive to PL deviation as low as 100 Hz. Shoot for PL deviation in the 500-700 Hz range and you'll be okay. 5. If the repeater receiver is not exactly on the same frequency as the user transmitter, the symmetry of the demodulated signal is impaired, and this may affect the operation of the CTCSS decoder. Since the HT1000, HT1250, and CDM1250 radios are very good performers, I'd check to see that the repeater was set correctly on frequency. 73, Eric Lemmon WB6FLY [EMAIL PROTECTED] wrote: > > I have a mixture of HT1000's, HT1250's and CDM1250's in service. My > problem is a delayed opening of the squelch on all of the radios, making > us miss the first part of the message. We are using a UHF repeater with > PL. The Minitor pagers and scanner hear everything fine, so I'm thinking > it has to do with the PL. > > Any thoughts? > > Thanks in advance, > > - Brian > - [EMAIL PROTECTED] > > > Community email addresses: > Post message: [EMAIL PROTECTED] > Subscribe: [EMAIL PROTECTED] > Unsubscribe: [EMAIL PROTECTED] > List owner: [EMAIL PROTECTED] > > Shortcut URL to this page: > http://www.yahoogroups.com/community/radio-programming > 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/
