FM Band Frequencies ending in an even number?
Glenn P
frequencies ending in even numbers eg. .0, .2, .4, .6, .8 MHz not used in
Australia?
The only 3 stations to use them are 88.6 a community station in Plenty
Valley Vic., 97.4 a community station in Melbourne's Western suburbs & 103.2
a community station in Sydney.
There aren't many or any used in the USA either, Great Britain seem to use
the even numbers quite a lot, I don't know about the rest of the world I
haven't looked into it that much yet.
Is there any particular reason?
If not, as long as the spectrum's organised properly, Aus can fit a lot more
FM stations in the band still.
Wombat Lover
> Does anyone know why (with the exception of 3 stations) are the FM band
> frequencies ending in even numbers eg. .0, .2, .4, .6, .8 MHz not used in
> Australia?
Don't know the reason mate...but you shouldnt forget an ABC Local Radio
station thats on 107.0 in the Northern Territory. Along with the LPON
stations
>From Robert | Wombat Lover | Seymour | http://www.surfnetvic.cjb.net |
Glenn P
"Wombat Lover" <sn...@bigpond.net.au> wrote in message
news:1118636740....@g14g2000cwa.googlegroups.com...
> Glenn P wrote:
> > Does anyone know why (with the exception of 3 stations) are the FM band
> > frequencies ending in even numbers eg. .0, .2, .4, .6, .8 MHz not used
in
> > Australia?
>
>
> Don't know the reason mate...but you shouldnt forget an ABC Local Radio
> station thats on 107.0 in the Northern Territory. Along with the LPON
> stations
>
FM, Radio National or Parliamentary Radio) on 107.0 in the Northern
Territory.
There are no stations registered on this frequency on either ABA or ACA
registers.
There are also no HPON stations on the ABA & ACA registers using frequencies
ending in even numbers.
Edward Thirkill
all us odd &even numbers
"Glenn P" <pleas...@tonewsgroups.com.au> wrote in message
news:42ad01cd$0$15763$afc3...@news.optusnet.com.au...
Reubot
~ Reubot
Wombat Lover
website. It definately DID exist if it doesnt now.....What the hell made
them close it?
Also..I didnt say HPON mate...It was LPON. You know those stations on 87.6,
87.8 and 88.0
--
From Robert | Wombat Lover | Melbourne | http://www.surfnetvic.cjb.net |
Frank
"Reubot" <.> wrote in message
news:42ad3cae$0$14817$afc3...@news.optusnet.com.au...
> It's becuase station spacing is .8MHz in Australia.
>
> ~ Reubot
What has that got to do with it ?
A FM channel is .2MHz wide. It depend on where the country involved decided
to start the sequence of channels.
Many European countries started at 88.0Mhz so it goes 88.0/88.2/88.4 etc.
Australia and the US started at 88.1 so the sequence is 88.1/88.3/88.5 etc
Frank
Abunyip
In general, stations need to be some distance apart on the dial, in
order to avoid interference from stations on adjacent channels. Where
stations are broadcasting on medium or high power, the technocrats
have decided that they should be 0.8MHz apart, so that they can be
picked up clearly without interference, even on poor quality
receivers.
The channels have been spaced 0.2MHz apart to set a consistent
standard around the country. Why .1 .3 .5 instead of .0 .2 .4 ? It
probably seemed a good idea at the time :) and it works.
In the case of 2CBA in Sydney, they were to be on 107.3 when they
started (as Sydney's third FM station) in the late 70s, but when they
commenced test broadcasts, their signal interacted with ABC Classic
FM's signal on 92.9 such that the Classic could be heard anywhere you
tuned across the band between 92.9 and CBA's own signal. They quickly
changed to 103.2. I have no technical knowledge, so don't have the
foggiest idea why this happened!
Wombat Lover
numbers, like Auckland being the obvious one. Others in odd numbers like
Christchurch
It gives variety I reckon
kevcat
why get hung up on why they started at 88.1
does it have to start at an even number?
what have you got against ODD numbers?
it is probably so that there was no bleed over/interference into the
commercial radio spectrum below 87.6 or what ever the band limit is
back when there where many more commercial users of low band VHF there
may have been some allocated right on the band edge
Kev
Frank
"kevcat" <kev...@dodo.com.au> wrote in message
news:42AD9104...@dodo.com.au...
I didn't make any comment suggesting that I "got hung up on why they started
at 88.1" .
I assume that the USA would have started at 88.1 because their TV channel 6
goes right up to the FM band.
Frank
oldtimer
being set up in the mid 70's. The ABA (I think it was) did a lot of work
with test transmissions from Mt Dandenong exactly to work out what was the
closest channel spacing that the cheapest, nastiest little portable receiver
could resolve. Given that the FM band was internationally agreed as being
88-108MHz, that gave 100 200KHz channels, but not all could be used in any
one area because of technical considerations such as Capture Effect and
Adjacent Channel rejection. I can remember looking at an HP Spectrum
Analyser showing FOX-FM's bandwidth back in the early 80's; nominally 200KHz
it often extended to 250KHz. So the powers that were decided that for the
nominal 200KHz bandwidth there needed to be a "guard band" of 200KHz just to
avoid reception problems of co-sited transmitters, particularly high power.
In the end the decision was 800KHZ channel spacing for high-powered local
transmitters. Why not start counting channels from 88.0 MHz rather
88.1MHz - not sure here, but remember that for a long time there was
scarcity of FM frequencies owing to the FM band being shared by TV channels
3, 4 and 5.
Oldtimer
"Wombat Lover" <Wo...@Lover.com.au> wrote in message
news:_Jfre.15740$F7....@news-server.bigpond.net.au...
Mark
I was wondering what the reason for 2CBA being on 103.2 rather than 103.3
was.
103.3 would maintain the standard 800khz spacing between them to 2MBS &
2DAY.
Regards,
Mark.
"Abunyip" <abu...@hotmail.com> wrote in message
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Frank
"Mark" <b...@froggy.com.au> wrote in message
news:42ae5e01$0$22895$5a62...@per-qv1-newsreader-01.iinet.net.au...
>
> I was wondering what the reason for 2CBA being on 103.2 rather than 103.3
> was.
> 103.3 would maintain the standard 800khz spacing between them to 2MBS &
> 2DAY.
>
> Regards,
> Mark.
2CBA was allocated 103.3 but had to change to 103.2 as it was causing
interference to another service (I can't remember but possibly channel 9 ).
Frank
Abunyip
wrote:
> they were to be on 107.3
Should have read: they were to be on 103.3
Frank
2SER were originally on 107.5 then moved to 107.3 to bring it into line with
the .8MHz spacing. This allowed 2GO to be allocated 107.7 instead of a
frequency (anyone remember) next to 2CFM 101.3 which caused interference to
TV services.
Frank
dk4875
I think 2CBA were allocated 103.2 because of the existance of a
community radio station 2CGR at Goulburn (only 200km SW of Sydney) on
103.3.
2CFM were originally to be on 100.5, but that was changed as it was
realised that it would cause interference to Channel 9 TV reception on
the Central Coast. 99.7 was originally mooted as the new frequency for
2CFM, before it was changed again (for some reason) to 101.3, where it
still is today.
Also, I think the reason for Australian FM stations ending in 'odd'
numbers rather than even is because the FM band 'officially' starts at
88.1 in this country (88.0 is considered 'off-band' like 87.8 and 87.6
are) and the 800khz "spacing" policy.
I can understand the need for 0.8 mhz spacing as:
1. On some rotary dial pocket radios, I used to find that stations
would be difficult to tune in properly if they were any closer
together.
2. In strong signal areas, FM stations could be heard across a 700 mhz
range on some receivers eg. in Sydney, 2MMM's 104.9 signal would start
to make it's presence felt from 104.55mhz right up to 105.25mhz (if you
have a receiver that operates in .05 mhz steps - or from 104.6 to 105.2
if not). There'd then be static at 105.30mhz, then JJJ's signal on
105.7 could be heard from 105.35 up to 106.05 (or 105.4 to 106.0).
Frank
"dk4875" <dken...@bigpond.net.au> wrote in message
news:1118744900.9...@g44g2000cwa.googlegroups.com...
Mark
that the first & last frequencies on the band would be 88.1 & 107.9 so that
no station would have any significant emissions below 88MHz or above
108MHz.
2CBA started in 1979 & community stations were still in the test
transmission stage then. If 2GCR was active at the time I would think that
their frequency would have been chosen so as not to interfere with Sydney's
bandplan rather than the reverse.
The interference with Ch 9 suggested for the 103.2 allocation is very
interesting. Ch9 is allocated 195 to 202 MHz so the only FM stations whose
second harmonic would be in that range would be those from 97.5 to 101 MHz.
The second harmonic is greatly suppressed too so that very little is
radiated but if the TV's receiver becomes overloaded by the FM signal, the
second harmonic will be regenerated and interference will result.
This happens in Sydney on Ch 7 where some receivers have 'wriggly lines'
on them due to overloading of that receiver by ABC-FM.
I think the 103.3/CH 9 problem must also involve cross-modulation and
inter-modulation as there is no direct harmonic relationship.
Mark.
"dk4875" <dken...@bigpond.net.au> wrote in message
news:1118744900.9...@g44g2000cwa.googlegroups.com...
>
Frank
> As FM Broadcast stations have an allocated bandwidth of 200khz, it follows
> that the first & last frequencies on the band would be 88.1 & 107.9 so
> that
> no station would have any significant emissions below 88MHz or above
> 108MHz.
>
> 2CBA started in 1979 & community stations were still in the test
> transmission stage then. If 2GCR was active at the time I would think that
> their frequency would have been chosen so as not to interfere with
> Sydney's
> bandplan rather than the reverse.
>
> The interference with Ch 9 suggested for the 103.2 allocation is very
> interesting. Ch9 is allocated 195 to 202 MHz so the only FM stations whose
> second harmonic would be in that range would be those from 97.5 to 101
> MHz.
>
> The second harmonic is greatly suppressed too so that very little is
> radiated but if the TV's receiver becomes overloaded by the FM signal, the
> second harmonic will be regenerated and interference will result.
>
> This happens in Sydney on Ch 7 where some receivers have 'wriggly lines'
> on them due to overloading of that receiver by ABC-FM.
>
> I think the 103.3/CH 9 problem must also involve cross-modulation and
> inter-modulation as there is no direct harmonic relationship.
>
> Mark.
>
change.
The Goulburn station opened about 8 years after 2CBA.
Frank
Justin
for 0.2MHz stepping for tuners in the US market, our regs call for 0.05. As
the US started at 88.1, they had no choice but to skip even numbers. As with
all technologies, we lumbered in later with a different standard & then it
was realised that we would be sourcing tuners that would be common to the US
standard, so we adjusted our standard to suit (& they say history never
repeats...)
Now days, most tuners would step 0.05, so odd numbers could be used, but
aren't (due to history). It would be nice if personal FM transmitters (like
the ones that hook up to Ipods) could transmit on the even numbers to avoid
interference. In Sydney, if you have a sensitive tuner, it's next to
impossible to find a completely free odd number in the ranges these things
work in (the 2 ends of the FM band).
Just my 2 cents worth (with rounding, that comes to 0 cents).
Justin
"Glenn P" <pleas...@tonewsgroups.com.au> wrote in message
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