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Old 03-06-2009, 03:19 PM   #5 (permalink)
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johnnyturbo
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Quote:
Originally Posted by mpctc View Post
Sorry to jump back in, but this is not correct. The GP68 can be set to 5khz, 10khz, 12.5khz and 25khz channel stepping.
I am also sorry to have to correct you, but:
frequency steps (i.e ability to tune in xxHz steps) is not the same as channel spacing!
25KHz spacing gives +/-5KHz deviation with appropriate bandwidth receiver filter
12.5KHz spacing gives +/-2.5KHz deviation with appropriate bandwidth receiver filter (this is often known as narrow mode)

So you can see that with a freq. band designed to use radios at 12.5KHz spacing (with 2.5KHz dev) the using a 25KHz radio can cause interference to a user on adjacent channel and as the receive filter is too wide, the rx audio will be low.

Also, on PMR446, apart form the power output issue, the radio needs to be able to tune in 6.25KHz steps, as although 446 uses 12.5KHz channel space, the channel freq.s are offset by 6.25KHz.

I hope this calrifies it for you.

John.
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mpctc (03-06-2009)