Thread: UHF CHANNEL BANDWIDTH

Originally Posted by Hamish71

I spoke to GME a couple of months ago. I was told, none of their product can, and they dont plan on doing any design on this until after the new specification is nailed down....think I have an email from them somewhere, will see if i can find it.

I guess it depends on the model.
Many of them are programmable like the 3840 that I use. I use it for CB at 5W (of course) and commercial frequencies at 25W.

The program does 36xx and 38xx radios.



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Originally Posted by LowRanger

There will be NO perceived lower volume problem.All the new radios will just have a better IF filter that will allow operation at the 12.5 KHz channel spacing compared to the 25KHz spacing now

Wayne

Hi Wayne,

Narrow Band radios (12k5 step) employ smaller FM deviation than the Wide Band (25k step) radios. A 12k5 transmission, when received with a 25k radio, is heard with a lower audio than a genuine 25k transmission due to its smaller spectrum occupancy. On the other hand, a 25k transmission, when received with a 12k5 radio, is heard with excessive audio level, up to the point that audio peaks used to be clipped.

There are some amateur radios in the market where you can select NB or WB FM in UHF (nothing to do with the WB filter for FM broadcast) so both RX and TX bandwidh are tuned to match the kind of service that you want to exploit.

Originally Posted by FFR

Hi Wayne,

There are some amateur radios in the market where you can select NB or WB FM in UHF (nothing to do with the WB filter for FM broadcast) so both RX and TX bandwidh are tuned to match the kind of service that you want to exploit.

As per my post above, GME also have that option for each channel.


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Originally Posted by FFR

Hi Wayne,

Narrow Band radios (12k5 step) employ smaller FM deviation than the Wide Band (25k step) radios. A 12k5 transmission, when received with a 25k radio, is heard with a lower audio than a genuine 25k transmission due to its smaller spectrum occupancy. On the other hand, a 25k transmission, when received with a 12k5 radio, is heard with excessive audio level, up to the point that audio peaks used to be clipped.

There are some amateur radios in the market where you can select NB or WB FM in UHF (nothing to do with the WB filter for FM broadcast) so both RX and TX bandwidh are tuned to match the kind of service that you want to exploit.

The 25KHz and 12.5KHz does not represent the width of the transmission.It is the spacing in KHz between the allocated channels.If you had a radio transmittting a signal that wide,the emitted spurious emissions would not meet FCC or Aust.Standards.

Wayne

Originally Posted by LowRanger

The 25KHz and 12.5KHz does not represent the width of the transmission.It is the spacing in KHz between the allocated channels.If you had a radio transmittting a signal that wide,the emitted spurious emissions would not meet FCC or Aust.Standards.

Wayne

Yes,

in the first line I named the NB radios as the UHF-CB having 12k5 step, and WB radios as the UHF-CB having 25k step. You'll agree with me that actual spectrum occupancy figures exceeds the scope of this forum.


On the other hand, in order to make my kenwood inter-operable between the old and new standards, I plan to reprogram it like:

1 WB (old)
1 NB (new)
2 WB (old)
2 NB (new)
.
.
.
41 NB (new)
42 NB (new)
43 NB (new)
.
.
.
80 NB (new)

... although it will take some time until I have the opportunity to test it...

Do you know if there is some amateur on-line receiver at Sydney area to experiment with?

Cheers,

Carlos