air traffic on ch25

[stevesperformance]

The last 2 days i have being picking up a lot of aircraft traffic on ch 25 (477.0250 mhz) . What's going on here , this is a public channel.

[stevesperformance]

As from 10 min ago its changed from ch 25 to ch 34
It sounds like commerial air traffic ie perth airport

[stevesperformance]

Did a bit off research at ACMA and found 4 mining company's are using those channels, Ch 4 and 34 duplex channels.I'm picking them because there is repeater a few km's from me.The repeater at margaret river is ch 4 - 34.
Still can't work out why there is so much traffic.It has as much air time as a commerical airport.

[vk6hgr]

Still can't work out why there is so much traffic.It has as much air time as a commerical airport.

Problem is with many scanners is that because they're so wide-band they have practically no filtering. it's possible that the frequency its showing isn't actually the frequency that they are operating on, but rather an image.

It's also possible that the scanner receiver is being overloaded and two signals are adding together to make up 477Mhz.

To see if it's an IF image, have a look in the manual for your scanner and see if it tells you what the IF frequency is. (usually 10.8Mhz) Reprogram another channel with the channel you're hearing them on PLUS the IF frequency and another MINUS the IF. If the signal is stronger one one of these two channels then you're listening to an image on 477Mhz and not the actual frequency.

[stevesperformance]

thanks gavin
Tried what you said.Heard nothing on the two freq's i program in only on ch 4 and 34

[Pty]

what brand/model of scanner do you have?

[stevesperformance]

Uniden BC796D

[frankstowing]

yes the airport do use uhf cb with subtone and yes they get very upset when you get on there subtone and tell them they are using cb as they think its a private ch they use ch 20 21 22 23 24 25 26

[vk6hgr]

yes the airport do use uhf cb with subtone and yes they get very upset when you get on there subtone and tell them they are using cb as they think its a private ch they use ch 20 21 22 23 24 25 26

That's... insane!

Fair enough if they use CB for cheap communications, but they have to REALISE that it is CB. Far better to buy a commercial channel than use CB for any business use at all, IMHO.

[frankstowing]

yeah well tell me bout it i got arrested 2 yrs ago for trying to tell them that they were on uhf cb and that any one could use it and i went down there to prove it to them and got arrested

they were using icom handhelds at the time and who ever programmed them told them it was a commercial freq and they had the right of use to be more specific VIRGIN BLUE

[vk6hgr]

yeah well tell me bout it i got arrested 2 yrs ago for trying to tell them that they were on uhf cb and that any one could use it and i went down there to prove it to them and got arrested

The problem is that anyone can use UHF CB, including commercial businesses. Unfortunately, there are a few bad egg comms companies out there that will happily respond to an order for a few "private channels" by programming up UHF CBs with CTCSS or DCS tone. The gear is cheaper and the profit margin higher.

The companies are now happy with their "private channel".

This all comes unstuck usually when the company complains to the ACMA that there are "unauthorised users" on their private channel. The ACMA will then take up their complaint and before long it will be discovered the radios they are using are on 477Mhz CB.

After the company realises they were duped they order proper land mobile band two-ways. (thereby having to pay for everything twice)

There were some problems here and in Melbourne with crane controllers using UHF CB a few years ago. This all happens far too often...

[PRC-495]

Channel 25 UHF CB is used by the Perth Radio Club. You will often hear alot of our members using it for Simplex communication.

I havn't heard any aircraft traffic on the channel as of yet. Will have to keep my ears open though!