44 replies to this topic

[M'bozo]

ChrisF_1, on Jan 28 2010, 12:19 PM, said:

I don't know if this is coincidence or whether perhaps they're dying as a result of the primary fault on the lines.

I would say it is probably coincidence.

[alanh]

ChrisF_1,
I don't know what type of lamp it is. Most street lights have an inductor which produces a high voltage to strike the arc in the lamp. If the lamp is aged, it continuously tries to restrike. This will cause lots of strong impulse interference.

The sodium (orange) lamps are designed to restrike if it goes out and the power is still applied.

AlanH

[ChrisF_1]

OK, it's been a while but here's an update. Firstly the streetlight was fixed the next day and things once again went back to how they'd been.

After some chasing on progress of the power pole fix, I've finally found out that it was repaired about two weeks ago. This is rather unfortunate as I've still got the interference issues. A trip up to the top of the drive with my AM radio confirmed the same noise I was hearing from the line outside our house. So another call to Radio Spectrum Management.

The RSM investigator came out today for another look and confirmed that the pole he'd previously detected was now ok. We went together to look at the line I'd identified and confirmed on his gear that it was giving off a signal. However, it turns out that it's a phone line not a power line and it seems to be just the span between the pole outside our house and the next pole up. (i.e. across my signal path) As it's not giving off a strong enough signal to wipe out an "on frequency" AM station on the investigator's gear he's advised me that he can't request a fix. Also he thinks it's unlikely to be the source of my problems as the signal is not picked up on the higher frequencies he tested. I tried to make the case that given it seemed an unusual souce of interference and that nothing else around seemed to be a problem, eliminating it may fix my issue. Unfortunately he didn't agree.

I don't know enough about this to guess how RF interference could be radiating from a phone line. We have ADSL2+ broadband to our house but I've followed the cable to cabinet end the street and the interference is only noticeable on this one segment. Also, I can still detect the radio noise on the power lines inside our house.

It seems like I'm reaching a dead end with this and my just have to live with it but I'd appreciate any other thoughts or suggestions.

Edited by ChrisF_1, 22 April 2010 - 01:58 PM.

[alanh]

Chris,
Firstly test your ADSL2+ for faults.
Go to www.speedtest.net and measure your upload, download speeds and ping time.
Find out from your ISP what speeds you are supposed to have.

As a test when the interference is bad, unplug all computer modems in your house and see what happens.

AlanH

[ChrisF_1]

alanh, on Apr 22 2010, 04:44 PM, said:

Chris,
Firstly test your ADSL2+ for faults.
Go to www.speedtest.net and measure your upload, download speeds and ping time.
Find out from your ISP what speeds you are supposed to have.

As a test when the interference is bad, unplug all computer modems in your house and see what happens.

AlanH

Hi Alan,

Thanks for the response. I've had ADSL2+ for a couple of years now and have no issues with speed and ping times etc. I'm connected to a roadside cabinet at the end of the street and get 15,000 Kbps speeds.
I've turned off the modem and my cordless phone but the noise on the AM radio off the wires is the same.

[alanh]

Chris,
What is your DTV reception like now?

AlanH

[ChrisF_1]

alanh, on Apr 23 2010, 01:30 AM, said:

Chris,
What is your DTV reception like now?

AlanH

Hi Alan,

We're still getting the periodic breakup issues. I've run some quailty logs again since the power line was fixed and I'm seeing similar occurrances of quality drop as I was seeing in December.

Chris

[alanh]

Chris,
Have you tried a piece of quad shielded RG6 cable from the antenna straight to a receiver. No amplifier, only the connection to the antenna and the receiver?

AlanH

[ChrisF_1]

alanh, on Apr 23 2010, 02:11 PM, said:

Chris,
Have you tried a piece of quad shielded RG6 cable from the antenna straight to a receiver. No amplifier, only the connection to the antenna and the receiver?

AlanH

Hi Alan, yes all of my initial testing excluded the amp and splitter from the circuit. All of my cabling is new quad shield RG6. I'm 99.9% sure that the issue is external to my set-up.

Chris

[alanh]

Chris,
The only thing left is a noisy masthead amplifier.
I would replace it with a Kingray MHU34FS which contains a filter to only pass 520 - 860 MHz. NZ UHF is 518 - 806 MHz.
Kingray's NZ address is in an earlier post in this strand.

AlanH

[ChrisF_1]

alanh, on Apr 24 2010, 08:46 PM, said:

Chris,
The only thing left is a noisy masthead amplifier.
I would replace it with a Kingray MHU34FS which contains a filter to only pass 520 - 860 MHz. NZ UHF is 518 - 806 MHz.
Kingray's NZ address is in an earlier post in this strand.

AlanH

Hi Alan, I've had the interference when the amp is not in circuit so I don't believe it's the issue but I'll look into the filtered model you've recommended.

Thanks for all of your help and suggestions.

Chris

[alanh]

Chris,
I live in an area with very strong interference.
To get over my reception problems I use a filtered high gain amplifier at the antenna so that the signal level down the cable is as strong as possible without overload. Even to the point of using a Kingray MDA20H filtered distribution amplifier at the splitting point. The equivalent for you is MDA20U.

The idea is that the quad shielding still cannot keep all the interference pickup out particularly in long lengths.

This system has been running for years and I only get the occasional burst of interference in wet weather.

AlanH

[ChaosMaster]

Alan, what you have suggested may help if the interference is out-of-band (ie. AM radio, GSM, etc) but will do nothing whatsoever if the interference is in-band and on-channel (ie. most forms of impulse noise). Filtering will only attenuate undesired frequencies that may be present in an antenna system - it won't 'repair' corrupted signals. I can say this especially in relation to my own experiences with impulse noise and filters. As pro installers on this forum keep repeating - the signal at the antenna must be good to start with, or you haven't much hope of success.

[alanh]

Chaosmaster,
If you go back to the first post, you will find he has very weak signals on a blocked path. So he installed a Hills Ultimate 36.

I agree that filters will not help with inband interference, however Chris has not mentioned any problems of inband interference when he used the digital field strength meter.

It is upto the RSM NZ and ACMA to prevent inband interference by keeping other transmissions out and have enough distance between TV transmitters to make inband interference rare.

Unfortunately the spectrum analyser sections of most digital field strength meters do not do wideband scans from AM broadcast band upwards. They only scan the TV bands only.

AlanH

[ChaosMaster]

alanh, on Apr 25 2010, 07:24 PM, said:

If you go back to the first post, you will find he has very weak signals on a blocked path. So he installed a Hills Ultimate 36.

I never disputed that.

alanh, on Apr 25 2010, 07:24 PM, said:

I agree that filters will not help with inband interference, however Chris has not mentioned any problems of inband interference when he used the digital field strength meter.

If the interference that is occurring is some form of electrical interference, it is almost certainly going to have a considerable amount of energy in-band and on-channel. Although not usually as much of a problem as at VHF, it can still in some cases be a headache at UHF, as many installers on this forum have given example over the years. Chris has said that there were intermittent periodic spikes of very poor MER while he was doing his testing, and that it seems to be the lowest channel that is worst affected. This is consistent with the behaviour of electrical/impulse noise. M'bozo seems to think this the case as well.

alanh, on Apr 25 2010, 07:24 PM, said:

It is upto the RSM NZ and ACMA to prevent inband interference by keeping other transmissions out and have enough distance between TV transmitters to make inband interference rare.

True in regards to actual transmissions, but unfortunately that doesn't prevent impulse noise affecting those frequencies...

EDIT: It has been a while since I last properly read this thread, and I just realised that all I have really done here is re-hash what M'bozo was saying earlier...  
I need to pay more attention sometimes...  

Edited by ChaosMaster, 25 April 2010 - 11:16 PM.

[alanh]

Chaosmaster,
Impulse noise energy drops as the frequency rises. On analog TV the band 1 channels of 0 -2 always suffer from a pair of horizontal bands from arcing on HV power lines. This problem is much less noticeable on channels 6 - 12. This is the reason why the ACMA states it is not allocating any DTV to RF channels below channel 6.

So if it is strong enough it can cause intermodulation distortion in masthead amplifiers making out of band noise become inband noise. Hence the need to put the filter at the input of the amplifier and not on the output. I am not suggesting you are doing this.

The higher the gain amplifier the greater the likelyhood of the impulse noise will cause the output voltage to reach near to that of the power supply, the greater the likelyhood of intermodulation distortion.

Chris has his gain turned right down to prevent intermodulation distortion, however there is insufficient gain for his very weak DTV signals.

AlanH

[ChaosMaster]

That is correct, Alan, however sometimes the impulse noise itself may have considerable energy in the UHF band (ie. not simply due to distortion in the amplifier), especially if it is a strong source, and if this is indeed the case, then filtering will be useless, as the signal has been irreversably corrupted before even reaching the amplifier.

[M'bozo]

julin, on 20 February 2012 - 02:35 PM, said:

I used to have this huge one that did everything I found it was just too intense for me, and too big!

Really?

Around here,

Long & thin, goes right in;

Short & thick, does the trick.

[DrP]

You are, of course, talking about the various types of F connectors and which type of coax is best suited to them?

[M'bozo]

various types of F connectors

Absolutely.

Male ones, of course.