Almost certainly a spur as mentioned. If it’s in the morning then the path towards NZ is in full daylight, so we can safely rule out Hamilton.
I don’t think I’ve ever had a genuine signal mixing with 2RN whilst in Sydney. You can very occasionally hear Hamilton very weakly in behind 2RN down here at night.
It’s around 8:20am when I go through that area and it happens every morning.
Possibly a harmonic of SEN 1170, since 576 just below half of 1170.
I’m not sure that harmonic is the correct term for whatever this is. I thought you could only get a harmonic as a whole number multiple - you could get the second harmonic of 576 at 1152. The only harmonic on 576 would be from 288. This could be an example of mixing of strong signals within the receiver (as opposed to harmonics that are real transmission). Possibly worth tuning around the rest of the band to see if there are any other mixing of signals.
I’ll give a theory/guess a try.
The proximity to the commercial transmitter site as @Radiohead mentioned is a probable factor here combined with a possible rusty/corroded downpipe or guttering join on one of the old buildings. I recall one of my RF theory teachers reciting a similar example where the corrosion at a join on long length of guttering or downpipe was producing a diode frequency multiplier curve effect which occurs when injecting signals into the non linear part of a diode. I wonder if it was copper piping? Most likely a MW TX mixing product from the corroded join & a/many MW signals where the pipe acts as both the RX/TX antenna & the corrosion as the frequency mixer multiplier? Just a theory.
Or maybe some faulty or crap piece of electronic equipment from one of the businesses ‘spewing out’ high levels of RFI when it shouldn’t.
You could use a laptop, SDR & software with a small MW loop around the area to track down the source if not perturbed by weird looks from other pedestrians 
. ACMA also offer a Interference Investigation service.
The correct term is PIM - passive intermodulation. It really becomes a problem with wideband receivers like mobiles bases where they use specialised PIM testers that generate two carriers in the band of interest and it scans across the band for low level intermods. Even poorly fitted coax connectors can generate PIM at 800Mhz. Early crystal sets used the principle with a Wilkison Sword razor blade and a thin piece of copper wire touching the surface. A bloke I worked with was in WW2 as a wireless Op and was shotdown over Germany and held prisoner and had the job of making a receiver to listen to BBC in the POW camp using a razor blade detector - he even made a crude loudspeaker until some headsets were smuggled in.
Anyone in the greater Sydney area preferably coastal please try 91.8 now. I am getting some very faint More fm Auckland… On the peaks, the very few of them it just pops above the noise floor… you have to listen very carefully.
The songs matched on the web stream. Unfortunately the TCL on 91.6 has just come on to make reception even more difficult. Any chance of 91.6 More fm Northland are now gone.
Unfortunately being close to 50kms from the coast doesn’t help with these NZ ducts.
There are some intense echoes off the coast of Sydney on radar so I’m not surprised that NZ tropo is making an appearance. A howling NW’ly here which will eventually kill the tropo in Sydney too I think- best to make hay while the sun doesn’t shine.
94.2 The Edge Auckland also just getting above the noise floor on peaks, similar to 91.8 More fm Auckland. Thanks to Today Country being completely nulled.
Some inland troppo today with strong Mt Dowe signals though only ABC so far.
99.1 WS Translator at Winmalee is currently off air, maintenance ???
I had ABC Local Radio from Mt Dowe rise up from the noise floor on a few occasions on the car radio. Quite unexpected considering the strong NW winds here in NW Sydney.
@RFBurns do you have any knowledge of what’s happening??
No, mains power outage at site, (Winmalee & Hawkesbury Heights area) Winmalee DAB is off air also from there & the UPS has gone flat so it’s taken out the microwave link to Mt Badgally DAB, so it’s off air as well.
Estimated restore time from the power company is 5pm today.
99.1 WSFM now back on air, ,so power mains outage has been resolved.
I assume the DAB network is back on air?
yes it sure is.
One wonders how many listeners 99.1 (and 88.3) really attract. There’s little to no promotion of these repeaters by WS FM. I’d wager that the majority of listeners stumble across them accidentally through in-car AF.
The justification for these repeaters is ropey at best in 2023. They might have made sense if WS FM remained a Western Sydney only station with a lower powered main transmitter at say Horsley Park, but that (beached) ship has long since sailed. Have any of the other commercial FMs cried foul and demanded their own Western Sydney repeaters?
Heading back up home this morning on the M7 near Prestons in Sydney, I had reception of 90.7 JJJ and 91.5 News Radio… other possibilities (88.3, 89.1 and 89.9 were blocked by Sydney suburban stations)… I may also have had weak Hit93.1 Wagga, but can’t be sure of that.
It’s commonly heard into Western Sydney via As on a car radio (even Oatley). I had it at Dural last week, though that was in an optimal location.
That post got me thinking, I haven’t mucked around trying for aircraft scatter in a while. We’re near a regular flight path so it’s not like it’s tough here either.
The Wide Bay nationals are regulars to fade up when a plane flies over (99.3 JJJ in particular as it’s not blocked by others), as do the Gympie ones. 93.7 goes from rock music to classical which is quite the change.
Down in Melbourne, Shepparton, Albury and even Swan Hill would fade up quite regularly when planes were in the right part of the sky.
The best example of AS at my location in NW Sydney is Eagle fm. If there is no enhancement it is below the noise floor. But if an aircraft passes to the north of us, Eagle fm will come up strong in stereo, and just below RDS strength. As soon as the aircraft passes the signal drops back to nothing.
I am on the Sydney Asia flights path, with the larger wide body aircraft’s ascending past around 12,000 feet.
When Sydney West International opens we will have flight paths much closer to us and a lot lower. Luckily we are not directly under any of them., but there will be a lot more AS.
I do remember AS on analog tv, the picture would shake and create a ghost image. I remember people close to the runways of Sydney Airport had terrible interference, , but digital tv fixed all of that.
