C8, C8 Pro Z Wave - Any Differences (my RSSI's are way lower)

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1

So I migrated C8 to C8 Pro yesterday and it went swimmingly well, everything working, no automation issues - slick :+1:

One thing I have noticed is that my Z Wave RSSI numbers are far lower:

C8 - Previously I only had 3 or less (of 46 devices) with an RSSI below 10.

C8 Pro - Today around a third (17) are below 10, in fact 11 are 5 or below.

I remain on Z-IP Gateway. So nothing has changed from my perspective; the old hub is powered down, the new hub is identically placed. In the main most devices are still directly connected (though one device now connects directly at 9.6 kbps that was 100 kbps previously)

It's all working and I don't want to be chasing numbers but I wonder what changed:

  • Does the new hub take time to settle in (despite the Z Wave radio being restored)?
  • Are there any differences to Z Wave on the C8 Pro?
  • Are the antennae the exact same model that were on the C8 with regard to frequency and gain?

Antenna test with/without C8 Pro antenna:

Screenshot 2026-04-17 at 09.51.25
Screenshot 2026-04-17 at 09.51.25720Ă—468 10.7 KB

Antenna test with old C8 antenna:

Screenshot 2026-04-17 at 09.54.10
Screenshot 2026-04-17 at 09.54.10700Ă—526 13.4 KB

Hmmmm! I did the test with the C8 antenna twice, the first test was better still at -69. Hardly a scientific test as I'm thinking the device I was testing to may have changed route after I removed the antenna for the first test.

I've kept one of the C8 antennas on the Pro, the forward one, as I noticed the one supplied with the Pro is not straight/a bit wonky.

2

Bump

It's got a little worse - now 20 devices below 10 RSSI

3

Animated GIF

So I dumped my Z Wave details into ChatGPT and it gave this explanation:

"Thanks—that dump is actually very telling, and it lets us move from guessing to something much more concrete."

:rotating_light: The headline: your RF is fine

These three lines matter far more than the RSSI numbers:

  • PER: 0 (Packet Error Rate = 0) across the board
  • RTT Avg: 1–3 ms for most nodes
  • Almost everything at 100 kbps direct

:point_right: That is a textbook healthy Z-Wave network.

If your RF were genuinely degraded, you would see:

  • non-zero PER
  • RTT spikes (10–100 ms+)
  • lots of route changes
  • fallback to 40 kbps / 9.6 kbps

You have none of that.

:chart_with_downwards_trend: So why does the RSSI look “wrong”?

The key clue is this pattern:

  • Values range from 0 dB → ~39 dB
  • Many direct nodes sit in the 1–10 dB range
  • A few are much higher (20–40 dB)
  • No correlation with performance

That is not how real signal strength behaves.

:point_right: What you’re seeing is almost certainly:

:test_tube: LWR RSSI = “Last Working Route RSSI” (not raw signal)

On Hubitat’s newer Z-Wave stack, this value is:

  • Taken from the last successful transmission
  • Not continuously updated
  • Influenced by:
    • noise at that moment
    • retries (even if PER ends up 0)
    • device firmware quirks
    • timing of last packet

So:

  • A device that hasn’t talked much → stale/low value
  • A chatty device → more “representative” value
  • A sleepy 500-series sensor → often garbage values

:mag: Your “red flag” example explained

1m device ~45 dB vs 5m device <10 dB

Looking at your table, that fits perfectly with:

  • High-message devices (e.g. powered switches, energy meter) → higher values
  • Low-traffic or sleepy devices → low/near-zero values

Example from your data:

  • Node 0x00e2 (Energy Meter) → 27 dB, 22,000+ messages
  • Node 0x0066 (Kitchen Spotlights) → 8 dB, only 4 messages

:point_right: That’s not distance—that’s data freshness and reporting context.

:satellite: The real smoking gun

This line alone disproves an RF issue:

0x0009 (Garden Steps)
RTT Avg: 4ms, LWR RSSI: 1dB, direct 100kbps

If RSSI were truly that low:

  • it would not sustain 100 kbps
  • RTT would be much higher
  • PER would not be 0

:point_right: So that “1 dB” is clearly not physical signal strength.

:brain: What changed with the C-8 Pro

Even with “identical firmware,” you likely have:

  • A newer Z-Wave SDK build or radio firmware
  • Slightly different interpretation of LWR RSSI
  • Less smoothing / more raw last-hop reporting

Result:
:point_right: The old hub showed nicer-looking, averaged values
:point_right: The new hub shows noisier, more situational values

:balance_scale: What you should trust instead

For Z-Wave health, prioritise:

  1. PER (yours = perfect)
  2. RTT (yours = excellent)
  3. Route stability (yours = stable)
  4. Data rate (100 kbps = optimal)

RSSI on Hubitat (especially “LWR RSSI”) is:
:point_right: diagnostic at best, misleading at worst

:receipt: Bottom line

  • Your network is objectively healthy
  • The low RSSI values are not real signal degradation
  • They are artifacts of how the new hub reports “last working route” conditions

:compass: If you want a definitive sanity check

Pick one “bad” node (e.g. 1–5 dB):

  • Hammer it with commands (on/off 20–30 times)
  • Then refresh stats

You’ll likely see:
:point_right: RSSI jump significantly
:point_right: with zero change in real behaviour

4

can't compare the way it is calculated changed for the new hub.

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