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Old 02-19-2012, 12:45 PM
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Default TPL vs DPL tones

Curious;
Are there any circumstances as to where a TPL or DPL tone would be preferred over each other in a narrow banded VHF or UHF repeater system or simplex system with the following factors involved.
Mountains, Trees, buildings, ext...

Last edited by camsdad; 02-19-2012 at 12:51 PM..
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Old 02-19-2012, 8:43 PM
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bump to the top!
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Old 02-19-2012, 11:22 PM
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No. DPL and PL behave identically under those circumstances.
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Old 02-20-2012, 9:14 AM
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Quote:
Originally Posted by zz0468 View Post
No. DPL and PL behave identically under those circumstances.
In general, I agree.

There is some belief that PL is more susceptible to "roll off" (when a voice or other background sound masks the analog PL, causing subscribers to drop audio unless they have an anti-roll off feature programmed). Supposedly DPL (which is a series of 1s and 0s transmitted at a rate of about 131 Hz) is less susceptible to roll off. I don't know if there are any serious studies to confirm the foregoing.

DPL should be avoided (at least on repeater outputs) in situations where the pool of subscribers includes radios of different makes and models. In such a case, you may find that some subscriber radios use a different convention for "zero departure direction", causing a DPL not to be decoded. The solution in such cases is to program the subscriber's Rx DPL for "invert," but this can play havoc with a "direct" button feature.

If two co-channel users of a repeater frequency pair are close enough that the receivers of one can hear the subscriber inputs of the other, you will have a problem if the PL user uses 131.8 and the other user uses DPL. The DPL system mobiles, when they unkey and send the DPL disconnect code, will cause the 131.8 system to key up momentarily.
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Old 03-05-2012, 9:36 PM
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Thank you for this information.
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