The ABCs and Nova stations are a similar strength here, all are better that what ARN and SCA stations are when operating from Gore Hill. But when from Artarmon, ARN and SCA are the strongest of all Sydney stations (with 2MBS close behind).
2 Likes
It used to usually be 20Kw for most ABC and SBS FM services - the original transmitters were 20Kw NECās and by the time the JJJ rollout happened they purchased 20Kw R&Sās tube transmitters. Obviously they have replaced the old tube transmitters with solid state although 20 years ago there was a lot of resistance to solid state FM because the efficiency was poor. Looks like that has improved. Gore Hill analog ABC TV was two 20kWās in parallel which was fairly unique, so Gore Hill would likely still be the highest power possible for FMās.
1 Like
If the ABC national fm transmitters are only rated at 15KW compared to 20KW would this put the ERP below 150KW / 25KW after antenna gain?
2 Likes
Theoretically yes, but I canāt for the life of me remember what the Nationals FMās at Gore Hill actually do run at, it probably is 20kW.
I donāt think the ERP is probably 150kW anyway, I sort of remember reading documentation for the Artarmon FM antenna that design was 18kW TX power was 150kW ERP, Gore Hill would be about the same, but there more services been added to the antenna arrays since then & more combiner filters inserted in the chain so more losses, even at 20kW TX power today mightnāt actually reach 150kW ERP?
Also reading documentation for the Artarmon FM Antenna & that what I posted somewhere around here about the power levels around the various points of the array thereās nowhere that actually transmits an ERP of 150kW, it falls short in a number of directions, even where the licence allows 150kW ERP.
Getting off topic here now though, Iāll see if I can find where I posted the Artarmon figures & we might have to move the conversation.
EDIT: Found the post, wow it was 12 months ago, time flies. https://forums.mediaspy.org/t/fm-spectrum-replan-general-discussion/17507/77?u=rfburns
3 Likes
Doing some mathematics for the Gore Hill site
If the Nova / Smooth transmitter is 20KW, and to get to 150KW would mean the main lobes would have an antenna gain of 7.5.
So would a 15KW transmitter only output a maximum of 112.5KW from the main lobes based on this antenna gain?
Obviously there would be other losses in the chain such as when the signals are feed into the combiner etc which probably would throw out my numbers above.
Would the reason Artarmon is below 150KW is because of losses in the chain from the 20KW transmitters to the arrays on the tower? Or are the transmitters set at slightly lower output?
3 Likes
Your figures look about right - a really big FM array has about 13dB of gain but you often lose half(3dB) on the way up there over a long feeder, so 20Kw in loses half on the way up - so 10kw gets up there and that gives 200Kw ERP. If the antenna gain is a bit lower than 13dB and the feeder and combiner losses are a bit more than 3dB then 150Kw ERP sounds about right.
Having said all that even if you halved the ERP hardly anyone except right on the fringes would notice - its not uncommon for someone to have to put a 100W exciter direct to air during a fault and hardly anyone even notices or complains.
4 Likes
That would be meā¦ I can tell when ARN or SCA are at Gore Hill or Artarmonā¦
4 Likes
Losses in the chain, the Artarmon transmitters output pretty much 20kW on the dot, day in day out.
2 Likes
Likewise. I am always suspicious when a signal that I know to be 3 bars in strength drops to 2 or belowā¦I think itās my preamp (sometimes it isā¦)
2 Likes
I used to look after some 5kw BE FM transmitters - they have a 9V battery that clips to the control board to keep the settings in memory if the power fails. If the battery goes flat and the power then gets interrupted the Tx comes up at its lowest power setting - 200W (I didnāt know about this at first). One day I go up there and sure enough its only running 200W. It had likely been at that for a while - no complaints and was perfectly listenable at my place 50Km away. Only indication back at the studio would have been the sig level on the monitor Rx which was usually left on the modulation monitor display.
High site with high gain antenna needs very little RF even when the other end is a consumer grade Rx.
3 Likes
Illawarra ABC National fmās from Knights Hill are now back to full power again, and my non tropo reception is probably the strongest I have had so far.
95.7 Classic at local strength with perfect stereo (no hiss) equivalent to 92.9 Classic Sydney
98.9 Triple J, close to 105.7 Triple J strength, slight hiss.
News Radio and ABC Illawarra also very strong at similar strength pre maintenance or better.
The ABC frequency finder says that some services will continue to go off air overnight between now and mid July but none will be on reduced power.
I wonder if they replaced the arrays on the tower?
5 Likes
I listen to footy on the shower radio had it on 97.3FM Thursday didnāt worry turning it back to 702. Reception perfect.
4 Likes
ā¦on his brand-new song, Superhuman.
The stomping Irish folk-pop song tells the story of a couple who become superhuman by escaping the mundane and following their dreams.
Damienās co-host Jade Tonta has made it her mission to create the greatest music video ever, despite having zero experience.
Elsewhere, it appears that i98 has dropped ā90 Minutes of the 90sā, which aired from 4pm Sunday afternoons, as itās no longer listed under the Shows menu on their website.
1 Like
Hopefully itās a move for i98 to shift younger skewed.
2 Likes
Meanwhile, Wave FM are looking for a new Announcer/Operations Assistant after their previous one has accepted a role in Sydney.
3 Likes
Who is that person and to what role and station have they moved to?
I must say I am so far impressed 2st 91.7 coverage from Gerringong, but the Kiama repeater is needed. For me it does a better job than power fm covering the Shoalhaven especially the northern end. I admit though 94.9 does have to cover a lot more ground. There isnāt much coverage (north of Gerringong) it is patchy.
2 Likes
And at the proposed 5 watts of power, 88.5 2ST Kiama isnāt going to get far.
2 Likes
According to the ACMA register the licence is still waiting for approval.
The past Nautel coverage maps I posted up on Mediaspy showed that coverage would be Rural Grade at best. 5W across Kiamaās hilly terrain is way underpowered. 200-500W is what is required , but then you have significant overspill into Wollongong.
4 Likes
Yeah itās really needed though. 999 had superior coverage at Kiama (from memory).
1 Like