40 channel - 80 channel

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goldy

goldy

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G’day Boys and Girls

I am looking for some wisdom from you lot again.

I am interested to know about the new arrangement with the 80 channel UHF.

As I understand it the existing channel covers 25 KHz. This will be split in two, giving 80 channels on a transceiver capable of narrow band tuning (12.5KHz).

What concerns me is if, for instance, I am on channel 1 on my old 40 channel (which is looking at a 25KHz), will it pick up someone on the new channel 41 (between 1 and 2) as well as 1???

Can anyone tell me why we needed 80 channels anyway? I live in Sydney and there are plenty of drongo’s talking crap on the radio here, but still a few you can go to out of the way so as to speak.

Just thought I put it out there, what do we all think.

Goldy
 
My new one has 80 channels, as far as I can work out the first 40 are the same as normal and yes the next 40 are in between like you say. I am assuming that if I am on channel 41, then anyone with a 40 channel radio will not hear me. and I don't believe if you are on 1 I would hear you on 1 and 41, they are different frequencies.

Did I make sense? lol
 
G'day Matt

I understand what you are saying. Your new radio will tune in a band 12.5 KHz, separating the new channels. I am thinking my old one could possibly pick up the whole 25KHz and therefore both new channels.

Purely hypothetical of course, I guess the strongest signal wins anyway !!

Goldy
 
There was a thread a few months back which had a link to the how's and whys of 80 channel and I'm sure it ruled out the "strongest signal wins" theory. I can't remember what the title was or who started it but it's here somewhere.
 
I agree with all, but Matt is right in the way the 80 channels is set up.

I have yet to upgrade mine to the 80 channels (it can be done), I am waiting for feedback on if there are issues talking between the current 40 channel radios and the 80 channels?

once I know they are glitch free I will upgrade, no need yet as everyone I talk to is on the 40 channels anyway.
 
Goldy there are a few things that will act to reduce interference on older 40 channel FM radios from new 80 channel radios operating on nearby 'half channels'.

Firstly FM radios exhibit what's known as 'the capture effect', that means that unless the 2 signals are very close in strength only the stronger one will be heard.

Secondly radios have what's called a passband, that sort of like a window through which it can listen to other signals. That window isn't as wide as the 25KHz channel spacing.

Thirdly the passband isn't square like a window, it's a sort of upside down wave shape and the closer you are to the high point of the wave the more signal comes through and the further out to the edges the less signal comes through. That means that even though the window does stretch (just about) to the next 12.5KHz channel is way out on the edge part where the radio doesn't listen well (low sensitivity).

Don't get me wrong you might still get interference, it's just that I doubt this cause will be very bad or happen very often.

Of more concern is what's called the deviation. When an FM radio signals is carrying sound the actual signal moves (or deviates) from it's centre position, with the new ones it doesn't move around as much but talking on a new one and listening on an old ones, well I expect that to cause soft audio. I might be wrong... but I doubt it.

Note, I'm talking about the older 40 channel rigs which were made before 12.5KHz channel spacing was mooted not the more recent ones, some of which can run that spacing after upgrade.
 
Thanks for your information everyone.

Geoff you dazzled me with science. Thanks. I understand much more than I did before.

Tiburn, I have a 5yo cheap Uniden. I will wait until it affects me before I change as well.

Not real good at tracing threads yet Krafty. I’ll keep trying.

Goldy
 
goldy said:
Not real good at tracing threads yet Krafty. I’ll keep trying.
Click to expand...

Gotta say I didn't think you'd have to, I'd have thought someone else would have remembered the thread by now and posted the link because from memory it did have some useful information in it.
 
Thinking my Uniden is starting to BEEP up.

Anyone got a 80 channel that has a scan feature ?
 
i have a gme tx3100 80 ch upgraded was very easy to upgrade to 80 ch seems to work good .has a open scan
 
Was talking to Matt last night and the one he has might be the go.

A mates got a Icom and its a very nice unit, Ill check that out to.

My sister's ex is a radio tech for Transgrid, so he is going to have a look at the Uniden first.

If its not feasable to fix, GME or Icom it is.
 
Geez Dave you must be made of money, you're always buying new toys, Must be good being a telstra contractor :ha:
 
I haven't bought anything big for a while, that I can remember.

I admit, I do spend to much.

Oh well, you only live once.
 
So everyone that has the 80 channel has no issues with it , on its own or talking to 40 channel sets?

have you to upgrade mine, all I need to do is take it to a dealer and they will for me. Just waiting for feedback before I do it.
 
Tiburn,
check GME websites and see if yours is listed if so instruction are on there to diy easy.

I did mine last weekend

cheers Bruce
 

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