Am To Fm Conversions In Solo Markets

In the most recent ACMA database, it’s still showing 2XXL as having an AM frequency, even though it had been switched off at the end of 2019. Most other AM-FM conversions no longer list their old AM frequencies on the database after they had been switched off & been converted to FM.

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When 2KA went to FM, the simulcast period was 12 months. Although I do believe the 783kHz transmission was decommissioned shortly after FM started but 1476kHz continued on until November 1993.

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Maybe due to reception issues to the west of the Nepean river. 1476 am cover and immediate surroundings better than 96.1FM. Id even say they should of kept the freq going.

The only problem is that 1476 used to get smashed every night by 4ZR. Some nights you could barely hear 2KA in Richmond, just 20km from the transmitter.

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There are issues here with 2CC at night due to 2GF Grafton; of course that will cease upon the latter’s conversion to FM. I think I can even null 2CC to receive a listenable signal from 2GF. (As an aside, is there any other market that aligns perfectly with another on both AM and FM? Canberra and Grafton both have 1206 and 104.7).

1008 is also a right mess with all three TAB stations (local+Brisbane and Launceston) all duking it out. 2CA has less competition and is fine.

When 5MU was still on, I often received it over the top of 1RPH.

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Hence the frequency being changed to 2EA’s old frequency 1386 after 1476 became a HPON. I don’t think 1386 ever made it to air though.

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I think 783 kHz is still in the Sydney LAP and reserved for community radio as well- but no group wants to take it up. Similar with 1386. It’s surprising that none of the main religious groups (Vision, Faith, Rhema) want 1386 as an HPON.

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I was reminded last night during some enhanced conditions what a crowded frequency 93.5 has become in coastal NNSW - 10kw PNN from Inverell was coming into Brisbane last night while 2PM Port Macquarie is also on the same frequency.

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I’ve heard that 2RE are reportedly not switching off the AM transmission. I’ve had a look at the Taree radio LAP and there are no amendments to suggest that the AM transmissions are going to continue.

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Not surprised if that’s the case, but then what is the point of the supposed FM conversion, the main reason for all this, was that AM transmissions cost too much, & FM is much cheaper to operate.

Now not everywhere there’s an AM transmitter/mast, but many places in the country, the AM site could be sold for housing developments, with the stations raking in the cash for what is effectively unusable land with a AM transmitter situated on it, though some places in the USA they have housing estates built around the AM mast, there’s a couple of places at least, that I know of, where there’s shopping malls built around the AM mast that sits in the middle of the car park.

If 2RE are to stay on AM as well as the FM “conversion” then they’ve actually increased the operational costs for very little gain.

The 2RE AM transmitter site is located on good farm (paddock) land, but probably not worth much to a developer as it’s in a flood plain not far from the Manning River bank & they probably wouldn’t be able to build on it & it’s only a small parcel of land considering the sounding farmlands also, so a neighbouring farmer isn’t going to pay much to acquire it, that’s assuming the local farmer doesn’t already own the land & 2RE just lease the land.

As someone who’s operated many transmitters, other than having to maintain the AM mast/antenna in most cases FM operations are just as expensive or more so, most FM towers are owned & maintained by others, so there’s little cost to a radio station there, only tower lease space, but the FM transmitters are higher power & use more electricity than the AM’s for similar (or less in a lot of cases) coverage.

Take Sydney for example, the commercial AM’s operate at a transmit power of 5-7kW 2CH (SEN) is licensed to 10kW, but don’t operate at that. The commercial FM’s operate at 20kW transmit power 3 to 4 times the amount of the AM’s, it’s only the ABC 50kW blow torch AM’s that are more expensive to run than the 20kW ABC FM’s.

Newcastle AM’s & FM’s run at much the same, 5kW directional Sky Racing & SBS, just over 2kW for 2HD, but then NEWFM runs at 5kW with Triple M & Hit 106.9 running at a bit over that at maybe 6 or 7kW because they have a lower gain antenna than NEWFM does. ABC local & RN AM runs at 10kW & the ABC FM’s probably also run around the 10kW power level.

DAB+ in Sydney, you have the main transmitter site at Artarmon running at just a touch over 4kW each multiplex (so times 3) & then you have 6 translator sites around the city running at 300 - 600W each multiplex (again times 3) & still don’t have full coverage of Sydney.

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If 2RE is able to keep both the AM & FM services, it just acts as evidence that the conversion is as much about locking out the opportunity for additional (competing) services. ACMA aren’t going to recycle AM frequencies (they’re simply too cost-prohibitive to operate) and the FM band is significantly congested in many locations that there are limited opportunities to have additional services without forcing a major shuffle.

While I appreciate that efforts to lower the operating costs of regional media help keep the sector going, but it shouldn’t come at the cost of poor utilisation of a public asset.

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Really, they should have found a way to allow the incumbent to offer a third service on FM with a ‘use it or lose it’ clause within a certain timeframe, say a couple of years. I know this requires amendment of the BSA etc, but it would have been the best outcome - either a third service programmed differently to the existing two, or competition by way of a new player.

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That’s interesting. The Sydney commercial FM’s are only broadcasting at 20kW while they are licensed to broadcast at 150kW?

I also thought fBI was broadcasting at 150kW, the same level as the commercial FMs.

Wasn’t DAB+ in Sydney at Artarmon increased to 50kW back in 2016? I’m surprised they are only broadcasting at 4kW.

It’s the difference between the power of the transmitter that is fed into the antenna that adds gain to give an effective radiated power (ERP) which is what is listed .

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I see, so the ERP is still at 150kW, even if the main transmitter is much lower at 20kW. Excuse my lack of knowledge when it comes to technical matters!

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And for the record to clear anything up, an AM mast/antenna has a gain of 0 - 1dB, so more or less what the transmitter power is, is what the radiated power is.

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Yeh but can you explain WTF Cyomotive force is?? I can’t work it out. Sounds like its something to do with the voltage between the mast and the earth mat measured as a field strength at 1 Km.

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Being honest, not easily, the basic definition for the non-RF engineers here reading is:

Cymomotive Force or CMF is a term used for expressing radiation intensity in volts, at lower frequencies.
It’s used in Australian legislation regulating AM broadcasting services, which describes it as: “for a transmitter, it means the product, expressed in volts, of: (a) the electric field strength at a given point in space, due to the operation of the transmitter; and (b) the distance of that point from the transmitter’s antenna”.

It’s related to AM broadcasting only, and expresses the field strength in “microvolts per metre, at a distance of 1 kilometre from the transmitting antenna”.

CMF is only used by/in Australia as a licensing regulation, Europe use a different way to measure AM radiated power & the USA just use the transmitter power for AM transmission radiation level licensing.

CMF is basically a reliable, measurable field strength, similar to measuring the field strength of FM or TV in dBuV.

I’m not 100% sure on when CMF was introduced as the Australian AM licence conditions for radiated power, but I don’t think they started using it, until the 10 - 9kHz spacing change in 1978.

For FM & TV, DTV & DAB+, ERP & EIRP are theoretical calculations, expressed as an “Estimate”, there’s no physical way to field measure an ERP or EIRP level, unlike CMF for AM broadcast.

This paper gives a more technical detail about CMF & how it’s calculated/used https://owenduffy.net/blog/?p=17255 & this paper really goes deep into engineering & calculations on CMF https://www.academia.edu/993176/CYMOMOTIVE_FORCE_OF_THE_VERTICAL_DIPOLE_ANTENNA

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Thanks for those links - an interesting read. One way to measure would be a to use a Potomac field strength meter at 1km and plug the reading into the appropriate equation.

Sounds like a lot of AM sites are not even being maintained now, so I don’t imagine it is going to be worth anyones while to invent a CMF meter.

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