Jas>>> On Sun, 27 Apr 2008 07:27:19 +1000d, Jason James Blathered on
>>> in48139e32$0$23382$ snipped-for-privacy@pit-reader.telstra.net:
>>>
>>>>> 400Mhz, future of UHF CB et al
>>>>> Discussion:-
>>>>>
>>>>
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>>> cb.html#post40513
>>>>> See Page 36 of the Pdf download re 12.5Khz channel spacing, see link
>>>> within.
>>>>>
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>>>>>
>>>>> The closing date for submissions is 18 July 2008.
>>>> Any increase in operating freq, will cause an increase in path-loss or
>>>> propagation loss. There are advantages ie more channels can be obtained.
>>>> A rough formula is: Prop-loss in dbs = 32 + 20log km (in kilometres) +
>>>> 20log f (megahertz)
>>>> To find the difference in path loss due freq increase, keep the distance
>>>> the same, then include the original freq in use. Note the answer,..then
>>>> insert the new freq. Subtract first value from the second,..and you have
>>>> your loss due freq increase in dbs. To obtain a useful value which
>>>> conveys an easily, you need to understand decibels (db). For example 30
>>>> db is 1000 times the original figure, 3db is twice the original figure.
>>>> Google up a db to linear conversion.
>>>>
>>>> Jason
>>>>
>>>> Jason
>>> But... but..
>>> The mooted idea is to decrease the channel intervals - that won't change
>>> anything but the 'requirement' for radios to be better at what they do in
>>> terms of adjacent channels being a problem.
>>
>> True, there will have to be reduced BW to stop adjacent ch splashing
>> dev.peaks into the ones either side. plus any reduction in channel spacing
>> will mean less deviation and therefore a degradation of Sig/Noise.
>Will this mean the end of those piss poor Uniden radios that have a
>front end so open you can hear every transmission in the 400-500MHz range??
Not just Unidens. GME's products are designed deliberately so that additional listen-only channels can be programmed anywhere betweek about 450 MHz and 520 MHz. Dunno if that's by design or just a 'feature' that they decided to use to commercial advantage. I'd say it's by design.
Craig.