UHF CHANNEL BANDWIDTH

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Originally Posted by Lotz-A-Landies

Garry

Submissions to the inquiry only closed on October 12th just gone, so it is unlikely that any legislation/regulation on the sale of legacy equipment will yet have been gazetted.

The old equipment will still be usable although 40 channel equipment will cause interference to 80 channel reception when they are on frequencies that are overlapped by the broad bandwidth 40 ch sets. There will also be some clipping of the audio reception, not too dissimilar to that which occurs on telephones.

My advice, don't rush in to any new equipment yet and there are likely to be a few bargains on 40 ch sets in the near future.

Diana

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You may get intermodulation,if someone in on an adjacent channel and is very local to you,and your radio is one of the older types.Any of the later models,should have good enough IF filters to filter just about all but the strongest or dirtiest signals.And you won't notice any clipping of the audio.I have been using adjacent frequency operation on different bands for nearly 40 years,and at 5 watts output,you won't have a problem,unless someone has been fiddling inside the radio.

Wayne

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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.

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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

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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.

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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.

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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.

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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

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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

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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)
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41 NB (new)
42 NB (new)
43 NB (new)
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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

Ahhhh I see what you are talking about now.You are talking about intermodulation.Where the signal transmitted on channel 1 (476.425) and recieved on the to be new channel 2 (476.4375) will be attenuated.I was talking about 2 radios of different types old (25KHz) and new (12.5KHz) transmitting and receiving on the same frequency,will not be attenuated.

I already have my Alinco handheld programmed,as I don't have it set as channels as such.Just set up to transmit and receive in 12.5KHz steps between 476.425 and 477.400.

And yes,this is probably not the forum to go into the technicalities,rather just the usability of the products.

Wayne