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Old 16th Nov 2019, 10:20 am   #21
simpsons
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Default Re: What FM aerial to install?

For what it's worth, the original BBC Television Sutton Coldfield 405 line transmitter Service Area, attached, at 61.75 mHz with an ERP of 32kW indicates an average 1.2 mv/m field strength in Shrewsbury. I'm unable to find the 250 kW FM field strength contour map and of course Shrewsbury has moved from Salop to Shropshire but nevertheless its all still positive for FM reception at 100 mHz.

Chris
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Old 16th Nov 2019, 4:04 pm   #22
paulsherwin
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Default Re: What FM aerial to install?

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You will get maximum fidelity using the 320k AAC internet stream, as even top grade FM reception has inherent limitations.
I'd have clean 15kHz bandwidth and 65dB s/n over lossy compression any day of the week. Granted, spectrum space restricts the number of BBC services available, but for top quality FM is worth the effort, in spite of Optimod, which is at least used sensibly on R3. Mind you, some of the R3 balances seem a bit odd these days, but perhaps that's just me - harrumph, harrumph...
To a large extent it comes down to personal preference (and prejudice ), but 320k AAC is very difficult to distinguish from an uncompressed CD even using very good equipment. The trouble with even perfect FM isn't the 15kHz frequency limitation, it's the noise floor.

Some people simply don't have access to a strong clean FM signal even with a good aerial though, and for those people the internet stream is always going to provide the best fidelity.
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Old 16th Nov 2019, 4:06 pm   #23
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Default Re: What FM aerial to install?

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... of course Shrewsbury has moved from Salop to Shropshire but nevertheless its all still positive for FM reception at 100 mHz.
Salop is the old name for Shrewsbury, so nothing has moved! Moreover, when boundary changes occur, nothing physically moves around!
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Old 16th Nov 2019, 4:11 pm   #24
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Default Re: What FM aerial to install?

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Those 'horizontal halo' omnis are popular with installers because they are easy to fit on the mast and don't need aligning with the transmitter. They can actually perform acceptably well in strong signal areas simply because they are mounted high up, but you definitely don't want them if reception is difficult.

I still don't get it. Most VHF/FM transmitters use mixed polarisation, and the rest are purely vertical, so the obvious choice for an omni is a vertical dipole.

Sure, if the mast is in the way there will be a nul, but a halo natively exhibits a similar nul anyway.
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Old 16th Nov 2019, 4:18 pm   #25
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Default Re: What FM aerial to install?

I very much agree, but the halos don't take up much space in the van, are easier to mount on the mast, and don't stress the mast as much in high winds. They're also cheap. The typical customer will know nothing about FM reception and will just ask for 'an aerial'. Righto says the rigger, and reaches for another halo. Job's a good 'un.
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Old 16th Nov 2019, 8:13 pm   #26
Ted Kendall
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320k AAC is very difficult to distinguish from an uncompressed CD even using very good equipment.
Difficult, but not impossible. The pity is that the BBC could put the matter beyond question as far as quality is concerned by using FLAC, as they did experimentally for a Proms season a couple of years ago. It still doesn't deal with internet glitches, but you can't otherwise argue with a lossless digital link from continuity.

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Old 16th Nov 2019, 10:25 pm   #27
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Default Re: What FM aerial to install?

Terry, I'm not as green as I am cabbage looking!!

Down South, some, myself included still send letters to Middlesex. Sad to say all we now are is a Post Code.

Chris from Harrow, Middlesex
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Old 16th Nov 2019, 11:07 pm   #28
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Default Re: What FM aerial to install?

Your local installer should have a clue - I'd go 3 element or 5 element yagi. My dad uses a 3 element for reception from Hedgehope for RNZ Concert, and we use a 5 element for relay between our Gore and Mid Dome Life FM sites.

Here I cut down our old band I/III VHF TV aerial to band II after VHF analogue shut down in 2013, but you guys have had no VHF for a lot longer so I doubt that's an option

Good quality coax is essential. Everything here is quad-shielded RG6.
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Old 17th Nov 2019, 9:23 am   #29
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Default Re: What FM aerial to install?

Plenty of food for thought here. I didn't expect so many responses to my question so thanks to all.
I liked this - 'If any of them suggest an omnidirectional aerial that's a good sign that they're incompetent cowboys'
I tend to concur with Ted's comment ' I'd have clean 15kHz bandwidth and 65dB s/n over lossy compression any day of the week'....but I will do another comparison of a live BBC3 concert broadcast between internet stream and FM. If FM is the winner I'll speak to some local installers and report back.
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Old 17th Nov 2019, 9:39 am   #30
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Default Re: What FM aerial to install?

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Originally Posted by simpsons View Post
For what it's worth, the original BBC Television Sutton Coldfield 405 line transmitter Service Area, attached, at 61.75 mHz with an ERP of 32kW indicates an average 1.2 mv/m field strength in Shrewsbury. I'm unable to find the 250 kW FM field strength contour map and of course Shrewsbury has moved from Salop to Shropshire but nevertheless its all still positive for FM reception at 100 mHz.

Chris
Interesting reading (attachment). Thanks
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Old 17th Nov 2019, 10:07 am   #31
Ted Kendall
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I will do another comparison of a live BBC3 concert broadcast between internet stream and FM. If FM is the winner I'll speak to some local installers and report back.
In the context, this is a circular argument - we started from the point that your s/n ratio on FM stereo is unsatisfactory, so as things stand it isn't going to give of its best against streaming - I'd just do it.
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Old 17th Nov 2019, 10:49 am   #32
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Default Re: What FM aerial to install?

I take your point Ted but actually I want to remind myself what the internet stream lacks for me.
I remember when I owned a Little Pink Thing (Pink Triangle) turntable and I bought a PT 1 deck. The latter turned out to have a damaged jewelled bearing but still sounded head and shoulders above the LPT.
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Old 17th Nov 2019, 4:58 pm   #33
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Default Re: What FM aerial to install?

Avinunca, I would be very interested, as I am sure others, in your Internet v FM comparison as I did one a few years back listening to the Proms. My comparison was based on:- FM/amp - Beomaster 8000, Internet Laptop, Freeview - Sony TV and SKY - Thomson box.

All this through Celestion Ditton 44's and with analogue audio. I found the timbre of the sound different on each platform but to say it was a true A/B comparison wasn't strictly true as the delay on each transmission made it tricky but nevertheless interesting. Getting the audio levels similar was on another level. No pun intended.

Which was true to the source is another matter and perhaps having personal experience in the theatre is necessary.

In conversation with the BBC, they put it down to the different feeds each platform received but did not elaberate.

Chris
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Old 17th Nov 2019, 5:05 pm   #34
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Default Re: What FM aerial to install?

The Freeview transmission is only 192k MP2, so I would certainly expect that to sound worse than both the internet stream and a good FM tuner.
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Old 26th Dec 2019, 1:14 pm   #35
Avinunca
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Default Re: What FM aerial to install?

Just a quick update to say that I did install my 3 element aerial in the loft. Not ideal as it still points toward the end of the party wall. Reception is quite good albeit with a little noise heard on quiet passages but good enough, especially at lower volume listening. Classic FM is a much better signal than R3 devoid of noise.I've no idea why as they are both from Sutton Coldfield. I haven't yet made a comparison between FM and internet but will do so. The new toy - Teac X1000 has my attention at the moment. I'm currently listening to a recording from last night at 7.30 of the BBC Proms Prom 71 : Bach Night. Sounds pretty good.
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Old 26th Dec 2019, 1:59 pm   #36
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Default Re: What FM aerial to install?

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Classic FM is a much better signal than R3 devoid of noise.I've no idea why as they are both from Sutton Coldfield.
Because Classic FM is compressed, Radio 3 is not. Regardless, my advice is to get the aerial ouside. You can diplex it with the TV download if it is decent stuff, saves running additional feeds.
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Old 26th Dec 2019, 2:55 pm   #37
Avinunca
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Default Re: What FM aerial to install?

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Originally Posted by Avinunca View Post
Classic FM is a much better signal than R3 devoid of noise.I've no idea why as they are both from Sutton Coldfield.
Because Classic FM is compressed, Radio 3 is not. Regardless, my advice is to get the aerial ouside. You can diplex it with the TV download if it is decent stuff, saves running additional feeds.
We hope to move house next year. The performance is good enough for now but I will definitely have a roof mounted aerial at the next house.

Why does compression affect noise? I thought it only affected audio. Isn't what I hear an RF issue?
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Old 26th Dec 2019, 3:06 pm   #38
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Default Re: What FM aerial to install?

Greater compression masks a high noise floor, but it's also true that signals from the same transmitter location can vary a lot in strength, particularly in marginal reception areas. The stations may use different physical transmitters and/or antenna arrays, and indoor aerials are very vulnerable to frequency selective effects. You may find you can improve reception by experimenting with the aerial position and alignment rather than just aligning it towards the transmitter using a compass. Good reception with a loft aerial is very much a black art.
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