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What is considered good DSL line attenuation ?

Line attenuation (loss) is a measure of how much the signal has degraded between the DSLAM and the modem. This is largely a function of the distance from the exchange. The lower the dB, the better for this measurement. Attenuation is logarithmic and each 3dB of attenuation halves the strength of the signal power received.

20dB and below is outstanding
20dB-30dB is excellent
30dB-40dB is very good
40dB-50dB is good
50dB-60dB is poor and may experience connectivity issues
60dB or above is bad and will experience connectivity issues

The standard signal attenuation spread for a given speed is somewhere in the region of 15-20dB for ADSL2/2+ speeds and 25-30dB for ADSL1 speeds. The following is a "guesstimate" of the line attenuation and maximum attainable speed based on distance:

Less than 1km = 24Mbit
1.0km = 13.81dB = 23Mbit
1.5km = 20.7dB = 21Mbit
2.0km = 27.6dB = 18Mbit
2.5km = 34.5dB = 13Mbit
3.0km = 41.4dB = 8Mbit
3.5km = 48.3dB = 6Mbit
4.0km = 56dB = 4Mbit
4.5km = 62.1dB = 3Mbit
5.0km = 69dB = 2Mbit

You may also want to try our SG DSL Speed Calculator

Note: ADSL1 and ADSL2 S/N Margins and Attenuation figures may be different despite being delivered from the same DSLAM port over the same copper/filters/etc. to the same modem. This may be due to measurement across only the frequencies actually in use, vs. measurement across all available frequencies.

Below is a detailed table of line attenuation (loss) and the corresponding attainable ADSL/ADSL2+ speeds:


Line loss (dB)Line length (km)ADSL2/2+ speed (Mbps)ADSL speed (Mbps)
10.07248
20.15248
30.22248
40.29248
50.36248
60.43248
70.51248
80.5823.98
90.6523.88
100.7223.78
110.823.58
120.8723.38
130.94238
141.0122.78
151.0922.48
161.1622.18
171.2321.78
181.321.48
191.38218
201.4520.68
211.5220.28
221.5919.78
231.6719.38
241.7418.88
251.8118.28
261.8817.68
271.9616.88
282.0316.28
292.115.78
302.17158
312.2514.48
322.3213.97.9
332.3913.47.9
342.4612.97.9
352.5312.37.8
362.6111.87.8
372.6811.27.7
382.7510.57.5
392.82107.3
402.99.57.1
412.9796.9
423.048.56.7
433.1186.5
443.197.56.2
453.267.15.8
463.336.75.6
473.46.35.4
483.4865.2
493.555.65
503.625.34.8
513.6954.6
523.774.74.4
533.844.44.2
543.914.24
553.983.93.8
564.063.73.6
574.133.43.4
584.23.23.2
594.272.92.9
604.352.72.7
614.422.52.5
624.492.32.3
634.562.12.1
644.6322
654.711.81.8
664.781.71.6
674.851.61.4
684.921.51.2
6951.41
705.071.30.8


  User Reviews/Comments:
    rate:
   avg:
by anonymous - 2017-03-01 15:41
what if mine is like this
DSL Attenuation: 236 dB
by anonymous - 2017-04-26 12:37
If you are looking at the value on your router, there may be a multiplier. For example, mine has a (0.1dB) next to the value.
by anonymous - 2017-07-07 13:31
High value Line Attenuation very poor.
by moda1560 - 2017-10-30 03:26
SNR margin Downstream: 9.2 db
Line Attenuation Downstream : 44.0 db
Downstream Speed: 7808 kbps

I'm not satisfied with this speed.
 
 
by EHZ_115 - 2018-01-30 01:40
SNR Downstream : 4 dB
SNR Upstream : 18 dB
Attenuation Downstream : 63 dB
Attenuation Upstream : 31 dB

please : /
by ma3toog Kanshello - 2018-05-19 08:55
mine is 34.1 and max speed is 9.2 Mbs
by anonymous - 2018-07-05 13:26
if you guys have low SNR check your phone lines to the box. if all good then its provider problem.
by anonymous - 2018-09-08 21:19
hi
i am getting 23.0 attenuation on downstream and 50.2 on upstream
i am like 4km away from my exchange i am getting 4mbps max but i have. a 20mbps package what can i do to improve my speed.
should i shift from adls2+ to vdsl2+ will that improve my speed
please let me know
by anonymous - 2020-01-24 09:08
VDSL is more sensitive to distance and not recommended for more than 1 KM distance from DSLAM.
by anonymous - 2020-03-23 16:54
COUNT YOURSELVES LUCKY I HAVE D/S OF 600kbps AND U/S OF 700kbps!THATS NOT EVEN A 1MB CONNECTION! LOL
by anonymous - 2020-05-20 15:37
Yeah, I have a TpLink brigde router and it has a 0.1dB multiplier next to it!
by anonymous - 2021-09-11 19:47
Mine is like this, is that good or bad, please?

Actual Rate(Up/Down) 758/12390 kbps
Attainable Rate(Up/Down) 2277/14388 kbps
Noise Margin(Up/Down) 28.9/7.4 dB
Line Attenuation(Up/Down) 16/26.6 dB
Output Power(Up/Down) 11.3/20 dBm
by Philip - 2021-09-21 08:51
Please use our forums for additional help and personal questions.
by anonymous - 2022-04-27 12:22
Line Attenuation(Up/Down) 3.7/14.4 dB
by tkalfaoglu - 2023-08-29 09:39
My Upstream values are much more different than my download for some reason.

Download Power 14.3 dbm
Upload Power 0.4 dbm

Download Rate 12921 kbps
Upload Rate 315 kps

Download Attenuation 22.6 dB
Upload Attenuation 47 dB

Any ideas why uploads suck?
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