774 ABC Melbourne audio problem - Page 1
Forum section: electronics / general

author: Circlotron
author_rank: Super Contributor
timestamp: June 23, 2021, 02:18:49 am
content: Could others in Melbourne have a listen to the above station on AM, not on streaming, and see if they can hear a problem with the audio? To me it sounds a bit furry or fuzzy similar to crossover distortion in an audio power amplifier, or that fuzziness you get with 8-bit audio. It is not huge, only slight. It is most apparent with voice. I sent them a text message the other day but I got no reply. I don’t think it’s my radio because other AM stations sound okay. If there are enough positive responses I’ll send them a link to this thread.Edit-> it seems more pronounced when someone is talking from the studio and not when from an external audio source e.g. when someone phones in.

author: Whales
author_rank: Super Contributor
timestamp: June 23, 2021, 04:48:59 am
content: In Sydney, sorry. Not that I have not hadmy own recent AM reception problems.Daft question: tried with a different radio? If not, then tried changing the batteries?

author: VK3DRB
author_rank: Super Contributor
timestamp: June 23, 2021, 10:34:17 am
content: Who listens to AM these days?DAB+ is far, FAR superior in sound quality and I know 774 is on DAB+ as well as the Internet. Have you tried listening to it on the car radio? That would verify whether it is your radio or a transmitter problem.Appropriate lyrics from this classic...

author: newbrain
author_rank: Super Contributor
timestamp: June 23, 2021, 10:53:08 am
content: In Rome,but to my ears the channel sounds quite good for AM.http://kiwisdr.vk3tlw.net:8073/?f=774.00amz8

author: Circlotron
author_rank: Super Contributor
timestamp: June 23, 2021, 12:40:50 pm
content: Quote from: newbrain on June 23, 2021, 10:53:08 amI think I can still hear the problem on that receiver, but I'll have a listen on the car radio tomorrow.

author: Circlotron
author_rank: Super Contributor
timestamp: June 23, 2021, 12:43:45 pm
content: Quote from: VK3DRB on June 23, 2021, 10:34:17 amSeveral other AM stations sound just fine on this radio, so I don't think it's that. I'll have a listen in the car tomorrow.

author: Circlotron
author_rank: Super Contributor
timestamp: June 23, 2021, 11:43:54 pm
content: Okay, so I'm beginning to think it might be modulation hum. I can definitely hear it on the car radio too, but it varies a bit from place to place.Quote

author: Kerlin
author_rank: Regular Contributor
timestamp: June 23, 2021, 11:45:07 pm
content: You can report any problems to B.A.I was a site maintenance tech on radio and T.V. transmitter sites for a while.They have a big network control center (NOC) and can easily check the systems at any point, including off air, by clicking a mouse.They have 24/7 operators that are very experienced and technical they control over 3,000 broadcast sites and transmitters.They do regular monitoring of field strength and reception in most areas.I assure you they are interested in reception issues, even in your area, and will check it.https://www.baicommunications.com/contact-us/I am experienced have worked in master control in a TV station and have a BOCP and TVOCP and I have listened and heard it, worth reporting, it could be just in your area, they will know.That will give you a definite solution to work with to find the answer to this reception problem.

author: Kerlin
author_rank: Regular Contributor
timestamp: June 23, 2021, 11:56:30 pm
content: Quote from: VK3DRB on June 23, 2021, 10:34:17 amWho listens to it, number of AM receivers Vs number of DAB receivers.In the Australian outback AM is king because of its wide coverage. This is the reason it is part of the emergency network.In the burbs as well it does offer excellent coverage. Listen to interstate a night with ease.Notice how the mobile reception is dropping, remember what it used to be like, what caused it?What is happening is that the AM stations are decreasing their output which will facilitate the shift to DAB.With reception the frequency plays a major part.774 Khz Vs 204 Mhz as an amateur radio operator I know which one I would prefer.DAB reception degrades very rapidly when reception is poor.

author: VK3DRB
author_rank: Super Contributor
timestamp: June 24, 2021, 01:01:34 am
content: I just tuned into 774 on the car radio. You are correct - there is definitely a background noise there that is not on other stations. The noise isn't 50Hz hum, but it is periodic. It sounds like poor shielding or a bad earth somewhere in their studio.Good find.

author: Kerlin
author_rank: Regular Contributor
timestamp: June 24, 2021, 01:45:17 am
content: It's probably a line level problem, the variance in noise would be due to the Optimod doing its thing.You would be a brave man to suggest to the ABC audio people they had a problem with shielding or earthing in their studio.The transmitter and studio are over 20Km apart so RF shielding is not normally an issue. It's more often a line level problem.

author: Circlotron
author_rank: Super Contributor
timestamp: June 24, 2021, 02:15:57 am
content: I haven't actually had a listen to a streaming version. At work right now so no sound. You can have a listen here ->https://www.abc.net.au/radio/melbourne/live/Edit -> if there is an issue between the studio and the transmitter site then it probably wouldn't show up in the streaming version.

author: VK3DRB
author_rank: Super Contributor
timestamp: June 25, 2021, 11:52:50 am
content: I contacted the ABC and gave them a link to this EEVBLOG thread. They said they will investigating the issue.Odd that half of Melbourne didn't report it, but as Tom Gleeson (Hardquiz) might say, "ABC listeners cannot hear much anyway even with a hearing aid."

author: Circlotron
author_rank: Super Contributor
timestamp: June 25, 2021, 12:50:03 pm
content: I had a listen at various locations on the way to work yesterday with the car radio and it was quite obvious. Still happening right now 10 to 11 Friday night. I was going to contact the ABC myself later on tonight but you beat me to it.

author: Kerlin
author_rank: Regular Contributor
timestamp: June 25, 2021, 11:30:30 pm
content: They will report it to B.A.

author: Circlotron
author_rank: Super Contributor
timestamp: June 27, 2021, 12:02:27 am
content: Took a quick recording last night. This is just the phone held in front of the radio speaker, but it is quite an accurate sample. The fuzz and buzz you can hear is not present on other stations.

author: vk6zgo
author_rank: Super Contributor
timestamp: June 28, 2021, 02:19:32 am
content: Quote from: Kerlin on June 24, 2021, 01:45:17 amDo the ABC use Optimods? ------Ohh, how the mighty have fallen!On the subject of the ABC:When I worked for PMG/ Telecom Aust many years back, from time to time when doing the "morning line up" at 6WF/WN, we would sometimes notice that the lineup tone from the Studio was low in level.Ringing up Master Control on the "Order wire", we would report it.The answer was "It's alright leaving here", as we watched the VU meter move up to the correct setting!It wasn't always them, though.A bit later, I was in the Broadcast Service Centre, when we received a modulation monitor from a country station, which was reported by the local Phone Techs as reading very high, so we sent them a replacement by return freight.On test, it was "spot on"!Whilst ruminating about that, the Boss received a call, saying the replacement one was "just as bad", so, unimpressed, he sent myself & another guy off to check.This was just before 5pm, so by the time we grabbed any useful gear, loaded the station wagon & headed off it was getting to be evening.Arriving around 10pm, we found that the mod mon's meter was slamming against the stop, but the programme sounded OK.Weird, so noticing a BWD CRO sitting in the disused workshop, we hung that across the RF monitor point in place of the mod mon.One look at the mod envelope had us diving for the Desk fader------ the thing was cutting carrier horribly.Waiting for the next "time pip" we set the level roughly, & waited for closedown.From time to time, a scheduled lineup was done, using a local source.8dB pads were switched into the desk VU meter, increasing their range by that amount, +16dBm was supplied from the local source, which then showed as 0VU.Next, the limiters were bypassed, so that level was fed directly to the Tx input which was adjusted so it reached about 90% modulation.The limiters were then restored to the chain, fed with the same level, adjusting them if necessary to 3 dB of limiting & their output level to produce the same approx 90% modulation.The phone guys neglected to switch the 8dB pads in, set the local source to show 0VU on the desk.This meant that the Tx were set for 90% mod at +8dBm, hence the overmodulation.-----Oops!The weird thing was, that it sounded OK off air, & nobody seemed to notice the multiple harmonics we must have been radiating.When I worked for TVW later in the day, we had a couple of community FM stations co sited with us, as part of our "good Corporate Citizen" policy.One of them had a couple of Auxilary Sub Channels (SCA in Oz talk) as a "nice little earner".The SCA folks reported interference, apparently from the main FM program, so we got dragged into it just to "stop the whingeing.".Initially, we found the SCA people had screwed up with their levels, so were under-deviating badly.This improved things markedly, but there was still "something there".Winding the poor old, complaining 7L12 spec an down to the bottom of its frequency range, we could just see an out of band signal on the composite stereo coming up the link.The Tech at the Community station eventually found it--- a switch set incorrectly on the Optimod.

author: vk6zgo
author_rank: Super Contributor
timestamp: June 28, 2021, 02:38:34 am
content: Quote from: Circlotron on June 24, 2021, 02:15:57 amBack in the day, there were people at the Tx site, duplicated analog programme lines & programme input equipment, as well as Main & Standby Transmitters & Antennas, so such a problem could be isolated fairly quickly.What happens today is obviously very different---------the penalty we pay for technological & management change.

author: Halcyon
author_rank: Unknown
timestamp: June 28, 2021, 10:00:30 am
content: Quote from: VK3DRB on June 23, 2021, 10:34:17 am4 of the top 10 radio stations in Sydney are AM with the most popular being 2GB (873 kHz) with over 12% of the listening audience.

author: VK3DRB
author_rank: Super Contributor
timestamp: June 28, 2021, 11:33:05 am
content: Quote from: Halcyon on June 28, 2021, 10:00:30 am2GB also streams and it is likely available on DAB+ as well. So how do you know if how much of the 12% are listening to AM radio?I know AM has some big advantages over other modes with long distance. For about 10 years I used to listen to 2GB on AM all the way from Wangaratta in Victoria (about 700km distance) using a big home brew loop antenna outside and an FT747GX. No problems listening to 2GB's Sunday Night Live with Gordon Moyes. Generally in the day I would listen to 2CA in Canberra. At the time, the North East of Victoria had no decent radio stations other than maybe ABC's 2CO in Cobram.In the 1990's, 2CO had announced it was going to FM when a farmer phoned up the station bitterly complaining that he only has AM radio in his tractor and he should not have to buy one of these new fangled FM radios that are all too complicated for farmers, and that the ABC can go and get stuffed. His final words prior to hanging up were, "You have lost me as a customer."