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[NewtronStar]

In the last months or so I have been keeping a close eye on tone 1710 as it getting a lot more noisy on FTTC, tone 1710 (4.3125 x 1710) + 2.15625 kHz = 7376.5 Khz) or 7.376 Mhz, have checked for transmitters in that frequency in the UK but can't find any that would effect this tone but something is when you look at my QLN's, would appreciate any information into the cause of this.




 

[burakkucat]

Examining the first graph, there are two almost co-incident, sharp peaks at ~ tone 1710. By graph number three, you have a veritable forest of peaks in the range of tones 1650 to 1750. That frequency range is approximately 7.1 MHz to 7.6 MHz.

Looking up that frequency range in the United Kingdom Table of Radio Frequency Allocations, I see --

[NewtronStar]

Examining the first graph, there are two almost co-incident, sharp peaks at ~ tone 1710. By graph number three, you have a veritable forest of peaks in the range of tones 1650 to 1750. That frequency range is approximately 7.1 MHz to 7.6 MHz.

Looking up that frequency range in the United Kingdom Table of Radio Frequency Allocations, I see --

I did look at those 3 transmitters but I am located in Ulster (N.I) most of them are located in the south of england which is 280 miles from me apart from Skelton which is 209 miles away could they still effect me, if I get a chance this weekend weather permitting i may set up the yagi and see what direction these signals are coming from 

[burakkucat]

. . . could they still effect me, if I get a chance this weekend weather permitting i may set up the yagi and see what direction these signals are coming from 

Difficult to say. It would be interesting if you could get a directional fix on one or more signals.

NATS -- National Air Traffic Services -- would be my prime suspect, until proven otherwise.

[NewtronStar]

NATS -- National Air Traffic Services -- would be my prime suspect, until proven otherwise.

Thankyou BC and Yes there are two Airports close by, don't know much about Nats frequencies only Aviation bands but they are 118-129 Mhz (VHF).

[burakkucat]

I understand that Belfast International Airport comes under the control of Prestwick NATS. 

[NewtronStar]

I understand that Belfast International Airport comes under the control of Prestwick NATS. 

Yes I think your spot BC, also noticed via this forum that other members have the same two peaks in the QLN tones in the DS band D2 tone 1380 (blue) and tone 1710 (red) as per my snapshot using DSLstats as it has great zoom into those tones, though other members QLN graphs seem to show a lessor extent to interference but those peaks are still there in the background.

[burakkucat]

Ah, so it would be very interesting to know what are the causes of those two peaks of interference. Clearly it is something nationwide, similar in effect to that of the Droitwich transmitter at 198 kHz.

Tone 1380 = ((1380 x 4.3125) + 2.15625) kHz = 5953 kHz
Tone 1710 = ((1710 x 4.3125) + 2.15625) kHz = 7377 kHz

[NewtronStar]

Ah, so it would be very interesting to know what are the causes of those two peaks of interference. Clearly it is something nationwide, similar in effect to that of the Droitwich transmitter at 198 kHz.

Tone 1380 = ((1380 x 4.3125) + 2.15625) kHz = 5953 kHz
Tone 1710 = ((1710 x 4.3125) + 2.15625) kHz = 7377 kHz

Checked to-day into these tones both are coming from foreign broadcasting stations, and these stations I can't understand them it sounds like Russian/polish the signal meter is higher at 76 degrees to me it's coming from Lithuanian, this beggars the question how many Kilowatts are they pumping out to effect my QLN graph   

[burakkucat]

Go back to your raw data (used to plot the QLN graph) and look up the dB values of the peaks at tones 45, 46 (Droitwich Transmitting Station), 1380 and 1710.

Knowing that Droitwich radiates at 500 kW, you should be able to estimate that effective power of those other two transmitters. 

[JGO]

Go back to your raw data (used to plot the QLN graph) and look up the dB values of the peaks at tones 45, 46 (Droitwich Transmitting Station), 1380 and 1710.

Knowing that Droitwich radiates at 500 kW, you should be able to estimate that effective power of those other two transmitters. 

Have I missed the point here ? What is the overall objective ? 
It might be possible to estimate the transmitter ERPs from a lot of other data, eg  aerial design, vertical angles, orientation of VDSL wires etc  but it won't improve the VDSL S/N for these tones. Comparing the amplitude with adjacent clear tones would be quicker and probably as accurate if the received power is wanted. 

[renluop]

Might this ve of use?

http://www.zilionis.lt/rtv/px.php?R

[les-70]

   I found very similar noise at roughly those frequencies due to a switched power supply.  It is surprising how many of these you can have around a pc setup, all give some noise but it is usually it is quite a small effect.  You may like to try switching off everything you can, ideally with a laptop direct to lan2 on HG612 and seeing what happens.  Also try moving cables about, and in particular the adsl lead if it runs near a psu. At least you can fairly easily see if this is an issue.

 I have reduced my qln noise spikes a lot by moving cables away from psu's - I have not been able to do this as well as I would like due to a need to be farily tidy.  The impact on the qln and snrm per tone graphs was good but confirming a comment above the impact on the overall snr was only 0.1 to 0.2 db.

[NewtronStar]

Might this ve of use?

http://www.zilionis.lt/rtv/px.php?R

Thankyou that is usefull can't see any stations falling into the tones of interest.

I found very similar noise at roughly those frequencies due to a switched power supply.

Cheers Les-70 I'll try your suggestion but don't have a laptop just two desktops but could test the one further away from modem and turn off this desktop and see what QLN graph it gives me.

[les-70]

 I think the QLN is only measured on a sync so you may find it easier to watch the srnm per tone as that changes "continuously".