Gocoax WF-803M insertion loss?

[jea101]

Does anyone know the loss between the Moca in and TV out port on the WF-803M.
If the TV out port isn’t amplified my guess is at least 3.5 db.
I am trying to determine why I am getting low signal levels at one of the adapters.

 

[degrub]

about 3.5 dB insertion loss. Internally, no loss.
TV out doesn't affect the MOCA signal reception.
Should be about 40 dB budget for the MOCA modems, so likely an issue in a termination or cable or splitter.

 

[jea101]

Thanks
That is what I was looking for.

 

[degrub]

best bet is to draw up a sketch with all of the cable paths between the moca nodes and count of the losses for each path. Usually the cable doesnt matter too much unless it is RG59 but you may need to count it if the budget it close.Sometimes you have to use an unbalanced splitter or a powered zero loss splitter to overcome too much loss. Also, make sure you have a moca POE filter at the head end and all terminations not used are terminated with a 75 ohm cap. reflections can generate noise that drops the SNR and causes issues.

Can you get into a diagnostic page on the moca modem and see the power levels, sync, and SNR ?

 

[jea101]

I found the problem.
Cable is over 70 feet of RG59.

 

[krkaufman]

I found the problem.
Cable is over 70 feet of RG59.

Surprising, as RG59 should have under 11 dB attenuation per 100 ft, at MoCA frequencies, leaving 46 dB remaining in the budget (57 dB max loss between nodes).

See: Coax Attenuation Chart (PDF)

 

[krkaufman]

Does anyone know the loss between the Moca in and TV out port on the WF-803M.

Well, it depends on the frequency of the signal, since the adapters are using an internal diplexer (dual filters), rather than a simple splitter, to splice the signals.

TV port attenuation:

• 5-1002 MHz: ~1 dB
• 1125-1675 MHz: 35-40+ dB

So the “TV” port mustn’t be used for connecting any devices requiring MoCA connectivity. (And that you’re asking the question makes me wonder if that isn’t what you were doing.)

p.s. The other filter of the internal diplexer passes MoCA frequencies with minimal loss between the MoCA chip and the “MoCA” coax port. Sub-1 GHz signals face 40 dB attenuation at the MoCA chip.

---

There’s also the FAQ entry from the goCoax support page:

Does your MoCA adapter includes a filter inside the device already, such that connecting Modem/TV/etc to the second (marked TV) coaxial connector of the device will filter out MoCA frequencies?"​

Our adapter features two internal filters. The first filter is designed specifically for MoCA and is located between the MoCA chip and the MoCA port. This filter has a frequency range of 1125 to 1675 MHz. The second filter is for TV and is located between the MoCA port and the TV port. This filter has a frequency range of 5 to 1002 MHz. These filters help to ensure that the MoCA and TV signals do not interfere with each other, providing reliable and efficient performance for both.

 

[drinkingbird]

Surprising, as RG59 should have under 11 dB attenuation per 100 ft, at MoCA frequencies, leaving 46 dB remaining in the budget (57 dB max loss between nodes).

See: Coax Attenuation Chart (PDF)

View attachment 51849

Yeah but that's in an ideal environment. RG-59 is typically dual shield (one braid, usually something low like 90 to 95% coverage on modern cable, lower on older cable, plus one foil), so very interference prone. Those frequencies are already pushing the lmiits of 59 so adding noise in is going to be cutting it really tight. Between the cable and splitter you're going to be around 12 to 13db loss at best.

 

[krkaufman]

you're going to be around 12 to 13db loss at best.

Sure, but still leaving 40+ dB budget.

Given the OP was asking about the loss via the TV port in the context of MoCA signal issues, I still lean towards their having used it to connect additional MoCA devices — which would put a much bigger hurt on the MoCA signals than 70+ feet of RG59.

 

[drinkingbird]

Sure, but still leaving 40+ dB budget.

Given the OP was asking about the loss via the TV port in the context of MoCA signal issues, I still lean towards their having used it to connect additional MoCA devices — which would put a much bigger hurt on the MoCA signals than 70+ feet of RG59.

Assuming by hurt you mean total death yeah You'd think printing "TV Port" on it would be a clue.

 

[krkaufman]

Assuming by hurt you mean total death yeah

No, not strictly, since the attenuation is 35-40 dB, so it depends on distance and other components in the path to exceed the 57 dB budget. The typical MoCA filter is similarly rated at just 35-40 dB attenuation, which can allow communication across the filter … given the right conditions.