10-24-2016 5:24 AM
I recently installed a Motorola HPNA 3.1 Adapter (from the Xbox 360 Hardware Kit) to connect a computer to my coax-based HPNA network. I noticed that CRC errors increased dramatically especially when my 2 IPTV receivers are active. I suspect that the HPNA adapter cannot handle multicast flooding leading to increased CRC errors.
Has anyone else experienced this and, if so, is there a remedy?
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10-24-2016 11:23 AM
When you installed the new HPNA adapter, how did you get the coax connected? I'm envisioning a new splitter. Is it rated to carry the traffic? Did you find one with only the correct number of ports or is there an open (i.e. unterminated) connector? Could also be an issue with the cable.
Can you try restoring the wiring to the original configuration and placing your PC where an existing box is and seeing if it works like that? That will tell you if it's an issue with the adapter use or with the cabling.
10-24-2016 12:51 PM
Thank you for the reply and suggestions.
The coax used is RG6 (not quad shielded) with compression connectors. The run to the HPNA adapter is quite short (probably less than 100 feet).
I tried 2 different splitter setups both using approved Holland HPNA splitters. The first was a 4-way splitter with the one unused port terminated with a 75 Ohm terminator. The second setup used two 2-way splitters in cascade (with the low loss connection feeding the longest cable run). Both of these configurations resulted in high CRC errors,
One additional test was done using a coaxial isolator (TII220) placing at the input to the HPNA adapter in an attempt to prevent ground loops. Unfortunately, use of the coax isolator resulted in an even higher number of CRC errors (I suspect that the isolation was bandlimiting the HPNA signal).
I haven't tried switching of the HPNA adapter with one of the set top boxes. I'm a little skeptical since I had similar results when testing the HPNA adapter at another (unused) location in my apartment.
I'm aware that managed Ethernet switches often provide a so-called IGMP snooping feature to eliminate multicast flooding (especially over WiFi). Unfortunately, the HPNA adapter has no configuation options. I suspect that the adapter may receiver multicast traffic since software running on the Xbox 360 was designed to emulate a set top box.
In the end, this may be a limitation of the adapter itself rather than a cabling or splitter issue.
10-25-2016 9:29 AM
Hearing that you knew to terminate the splitter resolves large amount of my concern. An interesting paper on HPNA over home coax may be found here:
It describes typical loss characteristics with splitters. AT&T usually used splitters rated for use with HPNA during such installations.
Yes, I'm sure the HPNA adapter will deliver to your PC multicast packets from streams subscribed by either TV receiver.
10-25-2016 11:34 AM
Thanks very much for sharing your expertise.
I'll leave the network as is for the time being. Although the CRC errors have increased, I'm not seeing pixelation (tiling) or freezing for IPTV.
BTW, I looked into Gigabit switches that provide VLAN and IGMP snooping capabilities. The Netgear GS108TV2 seems recommended. I could use the switch to split the Internet and IPTV VLANs suppressing multicast for the Internet portion. Since the Motorola HPNA 3.1 Adapter can function as an HPNA master, I could use the existing coax run to connect my PC but would need a second adapter to bridge HPNA back to Ethernet.
10-25-2016 2:40 PM
I think I might be tempted to use your coax as a pull string for a couple of cat 5e cables.
10-25-2016 4:13 PM
Thanks for the suggestion. I'll definitely consider running Cat5e (or Cat6) cabling should we ever renovate our condo.