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Author Topic: Does anyone have a spare BT80A-RF2 ?  (Read 3047 times)

H4rry

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Re: Does anyone have a spare BT80A-RF2 ?
« Reply #15 on: January 26, 2017, 12:54:35 PM »

I thought that when I put in the passive ADSL filter but then wondered if DSL being absent was preventing the filter from doing it's job... It may be the case that the RFI could be coming from another source... through AC wiring maybe. In which case, if the RF2 and active filter don't fix matters I am going to go systematically through all nearby wiring and maybe introduce some ferrite rings to see if that helps.
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burakkucat

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Re: Does anyone have a spare BT80A-RF2 ?
« Reply #16 on: January 26, 2017, 06:23:13 PM »

Although we do not know of your location and the immediate topography, I am assuming you are not located near the top of a hill with direct line of sight to the aerial of the relevant broadcast transmitter.

I wonder, on what type of telephone do you experience that RF breakthrough?  :-\
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H4rry

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Re: Does anyone have a spare BT80A-RF2 ?
« Reply #17 on: January 27, 2017, 08:33:27 AM »

No, situated in North London 6 miles from the transmitter (Saffron Green Mast).

I'm starting to get the feeling that this is a mains power problem. I think there's an AC adaptor somewhere picking up the radio station and then feeding it through the power wiring.

What confused me though, was that I completely shut down the house power from the master switch on the consumer unit, connected to the master socket test port and still got the rfi, but it wouldn't happen as often as when on the extension wiring. The very fact that it happened at all on the providers wiring with no power connected (using a simple corded telephone - no psu) is what has thrown me and I have been drawing my attention away from the local environment...

I'm running Quiet Line Tests when I can and systematically changing things until I hit on it... It can't hide forever :)
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Dray

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Re: Does anyone have a spare BT80A-RF2 ?
« Reply #18 on: January 27, 2017, 11:02:19 AM »

Is your phone wiring using twisted-pair, because untwisted will enable rfi?
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H4rry

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Re: Does anyone have a spare BT80A-RF2 ?
« Reply #19 on: January 27, 2017, 11:58:42 AM »

Yep, twisted pair all the way, I disconnected the bell wire from the master socket a few days ago since that is not part of a balanced pair and wondered if it was the culprit. Unfortunately not.
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burakkucat

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Re: Does anyone have a spare BT80A-RF2 ?
« Reply #20 on: January 27, 2017, 05:02:53 PM »

Ah, Saffron Green [1][2]. Unfortunately you are situated in the target location, specified to receive the broadcast transmissions!

[1] http://tx.mb21.co.uk/gallery/saffrongreen/
[2] http://wiki.tx.mb21.co.uk/index.php?title=Saffron_Green
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H4rry

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Re: Does anyone have a spare BT80A-RF2 ?
« Reply #21 on: January 27, 2017, 06:05:09 PM »

Yep, right in the firing line...

The RF2 arrived but it hasn't made any difference [sigh].

I've done more Quiet Line Tests via the test port and the interference is there even after unplugging the surrounding power cables. This problem is happening on BT's side. I told the initial engineer that the interference started when Broadband was removed from the line but he said that is likely to be a coincidence.

The most frustrating problem I am facing is that it's an intermittent interference that only happens about 5% of the time. When an engineer shows up there's no way to ensure that it will be happening and most engineers so far have arrived run HR/PQ/AC etc tests and just said that the line is fine and left. The only engineer to have made any changes was the initial one that changed pairs from the cab to the exchange after finding that it failed a PQ test at the cab and then came back to the house where it failed again but subsequently passed on a further test so off he went.

I've booked a further engineer for Monday.

Since the RF2 did not filter it out I'm now wondering if the RFI is happening at the exchange and then encoding it before I receive it? If it was in it's analogue form wouldn't the filter handle it? Listening to the interference it's not a continuous radio station but rather flashes of a station (always GOLD though).

I've attached a (zipped) mp3 of a typical quiet line test whilst the interference is happening. This was recorded today, it lasted for an hour and then disappeared again.
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burakkucat

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Re: Does anyone have a spare BT80A-RF2 ?
« Reply #22 on: January 27, 2017, 06:21:00 PM »

The RF3/RF2 are constructed for common-mode rejection, i.e. to reject spurious signals that appear on both legs of the pair. If the pair shows poor AC balance then common-mode rejection will be degraded.

Listening to your sample mp3 file, I noticed a brief heterodyne whistle. (Silly question time: Exactly how, with what, did you make that recording?)

I'm now leaning towards the possibility of a developing HR fault at a joint or at least a joint that is starting to show semi-conductive tendencies. Such a non-linear joint would obviously rectify any induced RF and also be the source of all sorts of intermodulation products.
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H4rry

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Re: Does anyone have a spare BT80A-RF2 ?
« Reply #23 on: January 27, 2017, 06:36:56 PM »

I see, so an imbalance on the lines (maybe due to a sudden HR fault - damp?) would prevent the said filters from filtering properly.

I made the recording using an ATA via an Asterisk PBX.

I'm hoping the engineer that comes on Monday is UG certified. Hopefully he can change pairs from the house DP to the cab (D-Side?) whereby I think that would constitute a complete change of all pairs to the exchange and hopefully resolve any HR fault along the path.
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burakkucat

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Re: Does anyone have a spare BT80A-RF2 ?
« Reply #24 on: January 27, 2017, 06:48:42 PM »

I see, so an imbalance on the lines (maybe due to a sudden HR fault - damp?) would prevent the said filters from filtering properly.

Yes, that is a possibility.

Quote
I made the recording using an ATA via an Asterisk PBX.

Ah, I understand. So that particular quiet line test was not performed from the test socket with nothing but a basic wired telephone connected. (I like to know all the details so as not to make any false deductions.)

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I'm hoping the engineer that comes on Monday is UG certified. Hopefully he can change pairs from the house DP to the cab (D-Side?) whereby I think that would constitute a complete change of all pairs to the exchange and hopefully resolve any HR fault along the path.

Yes, that is the D-side of your circuit. Do you have an underground service-feed to your property? Or is it via a final aerial drop?
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H4rry

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Re: Does anyone have a spare BT80A-RF2 ?
« Reply #25 on: January 27, 2017, 07:20:22 PM »

Yes, the quiet line test attached was via the ATA however it is indicative of tests done via the corded phone in the test socket.

I have a handheld recorder I could use next time I have the interference happening via a simple corded phone in the test socket.

The house is served via an underground service-feed. (no aerial-drop)

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burakkucat

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Re: Does anyone have a spare BT80A-RF2 ?
« Reply #26 on: January 27, 2017, 09:05:20 PM »

So the first joint, Openreach side of the NTE5/A, may be under a grey capping (or something similar), low on the external wall of the house. That one is always worth a (visual) look . . . just a few screws to undo.

The next joint will probably be at either an underground DP or just where your service feed connects to the larger D-side cable. And so on, to the PCP.
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H4rry

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Re: Does anyone have a spare BT80A-RF2 ?
« Reply #27 on: January 28, 2017, 03:15:14 PM »

The block terminal has already been checked, I got excited when I saw that there was green corroded contacts hoping that was the cause. But, after cutting back and re-terminating, the problem was no different. Btw, is the block terminal (grey capping) sometimes referred to as the DP? (Distribution Point) or is that label reserved for the branch of connectors under the first pavement cover?

I'm going to ask the engineer that arrives on Monday to change the connectors up to the PCP and hope that will sort it.

I've made another recording today (attached) that was done on a handheld mp3 recorder held next to the earpiece of a plain and simple corded telephone plugged into the master test socket. All other devices where unplugged.
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burakkucat

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Re: Does anyone have a spare BT80A-RF2 ?
« Reply #28 on: January 28, 2017, 04:03:10 PM »

. . . is the block terminal (grey capping) sometimes referred to as the DP? (Distribution Point) or is that label reserved for the branch of connectors under the first pavement cover?

The distribution point would be the latter for an underground feed. If an aerial feed was being considered, the DP is the terminal block at the top of the pole from whence all subscribers' drop-cables fan out to each property.

Quote
I've made another recording today (attached) that was done on a handheld mp3 recorder held next to the earpiece of a plain and simple corded telephone plugged into the master test socket. All other devices where unplugged.

Having listened to it, it does sound as if there is one (or more) defective joint(s) . . . HR or semi-conductive (non-linear).
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H4rry

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Re: Does anyone have a spare BT80A-RF2 ?
« Reply #29 on: January 28, 2017, 05:52:10 PM »

Thanks for your invaluable input burakkucat. I'm guessing former BT Engineer?.... or if your avatar is anything to go by, taste tester at Whiskas or Bird Catcher.
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