467.9250 and 468.8500 sound off frequency

[cartman]

From my listening location at Blacktown i can hear Channel Whiskey on the following four frequencies

467.9250 - sounds off frequency
468.3000 - reasonable signal
468.5750 - sounds superb
468.8500 - sounds off frequency

As the issue is on both frequencies 467.9250 and 468.8500, I suspect the problem is somewhere at the VKG Equipment Room at the SPC. Given that the Xray function doesn't seem to be part of the Whiskey operator, it really begs the question why we can hear Whiskey in the Sydney Metro region


Grant

For the record the transmitter locations on the ACMA are:

467.9250 - Heathcote, Condell Park, Bigola Plateau, Greenacre, Remington Building Sydney CBD, Parramatta, Hurstville, Hornsby Heights, Razorback
468.3000 - Maddens Plains, Berkeley Vale
468.5750 - Unknown location - suspected is at Remington Building Sydney CBD
468.8500 - Katoomba, Prospect, Kurrajong Heights, Blairmont, Horsley Park, Penrith, Razorback, Warragamba

[cartman]

This was posted on another forum by Jim K on 6th May 2010

"What I gather from a reliable source is that Channel X-ray no longer exists.
The channel is refereed as Channel Whisley as that is what the operator is on.
Apparently when it was Channel X-ray, they were sitting around doing nothing all day long"

[Longreach]

HI all, its been that way for years Cartman. your hearing the Heterodyne effect as multiple signals hit your scanner milliseconds apart.
i have a couple of Motorolas although dont suffer as badly but still gets effects of it.
468.575mhz seems to be the best frequency to listen on as its a lone transmitter. its usually the one i use when in sydney.
cheers
matt

[cartman]

So the 467.925 and 468.850 problem is a simulcast issue??

Grant

[citabria]

It's not an issue so much as an unavoidable side effect of having multiple transmitters. The system can be tuned to minimise the effects of multipath in certain areas, but as a scanner listener, you just gotta put up with it

[cartman]

I recall it sounded OK at the start - it has only deteriorated during 2010

[ivahri]

Antenna selection & location might help Citabria but at 400MHz having two exterior base sites so close together is gonna heterodyne if monitored outside of either coverage area. If Grant was close to one & not the other then Capture Effect would take care of the problem. I know my agency uses the same UHF freq in about 5 locations but so long as you are close to one & not the others the problem isn't serious (except for two bases discussed elsewhere that are only 7km apart- that is a disaster).

There are technical solutions like Tait's Quasisynch but that could start an argument about how effective that is.

Cheers,


Richard

[cartman]

I am just about sitting on top of the Prospect repeater and Horsley Park isn't that far away.

Grant

[ivahri]

Hi Grant,

Are Prospect and Horsley Park both operational? Wow, that is way too close if they are.

Cheers,


Richard

[citabria]

Very true ivahri, I also recall that Hornsby district RFS PRM was using simulcast until the Rubidium clocks started to drift.. then it all started to sound quite bad (it was even worse on hot days which I would guess is the heat making the clocks drift even further apart)