Rogers Community

Hwaiting · ‎12-18-2022

Hi all,

TL;DR - my OFDM levels and correctable codewords seem high. Would removing the amp + splitter put the OFDM levels more in range even if it may cause QAM levels to suffer?

The cable that enters my home through the electrical box in the basement is connected to amplifier (Antronix MVRA501B). The amp was installed by Rogers during my pre-Ignite days where I had 4 cable runs throughout the home. When I switched to Ignite, the install tech didn't check any part of that so the amp is still part of the setup. I ended up disconnecting 3 of 4 lines from the amp and put terminal caps on the unused outputs on the amp.

The one active cable from the amp goes up to the 2nd floor where the XB7 is. As the signal was too strong the tech installed a splitter (-3dB) before the modem.

I've always had that QAM high frequency roll-off so I thought I needed the amp but I see my OFDM levels seem high. I also see that I have a high number of Correctable Codewords for my OFDM channels. Is this a problem?

I think I read somewhere if you have OFDM, then it's more important to keep those happy vs the QAM channels. Is the range for OFDM like QAM (+-10dBmV and around 38dB)?

Should I remove the amp & -3dB splitter and would that improve my situation? I don't have any critical issues aside from only getting 80% of advertised speeds (400Mbps on a 500Mbps plan). If I remove the amp, I think it may cause some of the high freq QAM channels to go beyond -10dBs so I'm not sure if I should. Back when I had the CODA, I was getting similar if not slightly higher speeds on a 300Mbps plan).

Any advice would be appreciated. Thanks.

Downstream

Channel Bonding Value

Index

13

1

2

3

4

5

6

7

8

9

10

11

12

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

34

33

34

Lock Status

Locked

Frequency

651 MHz

279 MHz

579 MHz

585 MHz

591 MHz

597 MHz

603 MHz

609 MHz

615 MHz

621 MHz

633 MHz

639 MHz

645 MHz

657 MHz

663 MHz

669 MHz

675 MHz

681 MHz

687 MHz

693 MHz

699 MHz

705 MHz

711 MHz

717 MHz

723 MHz

825 MHz

831 MHz

837 MHz

843 MHz

849 MHz

855 MHz

861 MHz

216 MHz

350000000

216000000

SNR

37.6 dB

39.2 dB

40.6 dB

39.8 dB

39.6 dB

39.8 dB

39.1 dB

38.4 dB

38.8 dB

38.6 dB

38.7 dB

38.3 dB

38.0 dB

38.1 dB

37.8 dB

36.6 dB

38.0 dB

37.4 dB

37.2 dB

36.8 dB

36.1 dB

35.9 dB

36.4 dB

36.5 dB

36.6 dB

36.7 dB

36.8 dB

37.2 dB

37.3 dB

37.4 dB

42.8 dB

40.9 dB

42.7 dB

Power Level

-3.0 dBmV

4.4 dBmV

1.5 dBmV

1.3 dBmV

1.1 dBmV

0.5 dBmV

0.1 dBmV

0.7 dBmV

0.8 dBmV

-1.5 dBmV

-1.8 dBmV

-2.3 dBmV

-3.0 dBmV

-3.1 dBmV

-3.3 dBmV

-3.8 dBmV

-4.4 dBmV

-5.0 dBmV

-5.7 dBmV

-6.1 dBmV

-5.4 dBmV

-5.1 dBmV

-5.0 dBmV

-4.6 dBmV

-4.4 dBmV

-4.5 dBmV

9.3 dBmV

5.5 dBmV

9.2 dBmV

Modulation

256 QAM

OFDM

Upstream	Channel Bonding Value
Index	1	2	3	4
Lock Status	Locked	Locked	Locked	Locked
Frequency	21 MHz	25 MHz	32 MHz	38 MHz
Symbol Rate	2560	5120	5120	5120
Power Level	36.8 dBmV	39.0 dBmV	41.0 dBmV	41.0 dBmV
Modulation	QAM	QAM	QAM	QAM
Channel Type	TDMA_AND_ATDMA	ATDMA	ATDMA	ATDMA

CM Error Codewords
Index	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	25	26	27	28	29	30	31	32	33	34
Unerrored Codewords	3427353530	4276686330	4276698476	4276725936	4276755056	4276770164	4276783570	4276810139	4276820842	4276825259	4276845268	4276849272	4276852299	4276854167	4276865294	4276869339	4276882412	4276898483	4276907401	4276913074	4276929965	4276936737	4230822981	4276952588	4276956256	4276961790	4276974188	4276974622	4276989424	4276991390	4276996022	4276994728	2737725724	3427353530
Correctable Codewords	251038570	0	3	0	1	2	0	0	2	0	0	1	3	4	2	5	4	10	13	43	110	296	599	653	360	235	177	164	93	79	42	43	2330990283	251038570
Uncorrectable Codewords	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	92	237	0	0	0	0	0	0	0	0	1	0

-G- · ‎12-18-2022

@Hwaiting wrote:

Hi all,

TL;DR - my OFDM levels and correctable codewords seem high. Would removing the amp + splitter put the OFDM levels more in range even if it may cause QAM levels to suffer?

Having a high number of correctable errors on an OFDM channel is not a problem. It's actually a good thing. (See this topic for more info.) The important thing is that you have zero (or close to zero) uncorrectable errors.

The cable that enters my home through the electrical box in the basement is connected to amplifier (Antronix MVRA501B). The amp was installed by Rogers during my pre-Ignite days where I had 4 cable runs throughout the home. When I switched to Ignite, the install tech didn't check any part of that so the amp is still part of the setup. I ended up disconnecting 3 of 4 lines from the amp and put terminal caps on the unused outputs on the amp.

I would remove the amp. It's probably a "zero gain" amp (0 dB gain on the output) and these are typically used where the signal coming into the home is good but a passive splitter would cause the output to drop to unacceptable levels. With a "zero gain" amplifier/splitter, the output signal should be at the same level as the input signal... so there is no benefit to leaving it installed if you only have one coax-connected device in your home. Also, while the signal will not get boosted, noise will... and that is not good.

Remove the amplifier/splitter and use an F81 barrel connect to connect the incoming coax feed to the coax line leading to your gateway. Alternatively, you can use the splitter that the tech installed as well.

I'm not sure what to make of your signals. Your OFDM channels are reading 9 dBmV but you have other QAM channels reading -6 dBmV. Will be interesting to see if things level out after removing the amplifier.

Rogers Community

Signal levels and setup question, also QAM vs OFDM

Re: Signal levels and setup question, also QAM vs OFDM