Subject: [NEXTEL-1] CTCSS or DCS Signaling?

From: [email-masked]
Date: Tue, 1 Jul 2003 16:06:31 -0400

Okay, stupid question time.  I need to hear from folks with specific,
real-world field experience in this.  I already have all the textbooks. 
For an FM UHF system I am designing, I need to know whether CTCSS or DCS
signaling would be the better choice.  My main interest is the robustness
of the signaling.  Specifically, I have two operational concerns:
1)  For fringe area (low RSSI) reception of the transmitted signal, which
method, if either, is more likely to keep the squelch open?
2)  For errant "doubled" (simultaneous) transmissions by two mobile
units, aside from FM capture effect (assume equal RSSI at receiving
station), is either signaling method more or less likely to open the
receiving station's squelch (assume both transmitting stations to be
using the *same* signaling method, of course)?  Okay, I admit I am
grabbing at straws on this second concern.

This system will be operating on a shared channel that is very lightly
loaded, and will have a very small number of subscribers (I am planning
on six).  Are there any other considerations of which I may not be aware,
please??  DCS inversion should not be a factor as this is a simple
base-mobile system, not operating a repeater.

Many thanks to all,
Alan Dixon

[Please copy replies to: [email-masked] <wpuc720[a]juno.com>]

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From: [email-masked]
Date: Tue, 01 Jul 2003 20:07:45 -0400

A1) I have found that DCS works better in urban (NYC) fringe conditions. I also
found DCS equipped repeaters had less chance of responding to distant stations on
the input since DCS had a larger selection of codes. Occasionally someone's voice
would resonate the exact CTCSS frequency momentarily and open the squelch on other
uses radios. Then the complaints would fly "Someone is on our channel", etc. If
you select CTCSS stay away from low tones.

A2) "doubled"- 2  CTCSS users can create some horrible noises. I can't remember
hearing the same with DCS. But that does not mean it can't happen.

If you want more info I can send you the Tel.# of a guy who manages a huge system,
and it is not Nexthell.

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