Hello,
I have an HDHR5-4DT (firmware 20260326) in the UK, working perfectly on Freeview. I'm also a radio amateur experimenting with narrowband DVB-T2 on the 70cm band, and I have three questions I'd rather ask than guess at.
1. Are the narrow DVB-T2 modulations implemented in the demodulator?
get /sys/features reports:
t8dvbt2 t7dvbt2 t6dvbt2 t5dvbt2 t4dvbt2 t3dvbt2 t2dvbt2 t1dvbt2 (and the same ladder for DVB-T)
Are the narrow entries (t1 to t5) actually implemented in the demod, or accepted by the command parser without corresponding demod support?
What I've observed: the tuner accepts arbitrary frequencies in Hz, which is very useful. set /tuner0/channel t1dvbt2:437000000 is accepted and reported back correctly. With a 1.7 MHz DVB-T2 signal present at 437 MHz, signal strength reads ss=90, so the front end clearly hears it, but snq stays at 0 and there's no lock, even after a minute. Identical behaviour at t2dvbt2 with a 2.0 MHz signal, and across frequency offsets of ±200 kHz.
For comparison, a Freeview DVB-T2 (Crystal Palace) mux at 546 MHz locks within about five seconds: ss=100 snq=100 seq=100 bps=40427520. So the unit is healthy, and the narrowband signal is known good, it's from a BATC Portsdown 4 transmitter and locks reliably on both a Sony CXD2880 receiver and a Knucker/Ryde receiver.
The complete absence of snq movement suggests the demod isn't attempting acquisition in these modes rather than trying and failing. Is that right?
2. Is there a newer model that does support them?
If this unit's demodulator doesn't do the narrow bandwidths, is there a current or forthcoming model whose demod does? I'd happily buy one if so. Equally, if the answer is that no HDHomeRun supports them, I'd rather know than experiment further.
3. ATSC 3.0 — how flexible is the tuning?
Separately, I'd like to begin ATSC 3.0 experiments on UK amateur allocations, where we have some freedom to try modes that aren't broadcast here. I'm interested in an ATSC 3.0 model as a reference receiver, but I'd need to know:
Does an ATSC 3.0 model accept arbitrary frequencies in Hz, as the DVB models do, or is it constrained to the US channel plan?
What is its tuning range? I'd be working in the 70cm band (430–440 MHz) and potentially 23cm vi a downconverter.
Is 6 MHz the only bandwidth, or are narrower options exposed?
Would the demodulator care about anything US-specific in the signalling, or would it lock to any conformant ATSC 3.0 transmission?
The appeal of ATSC 3.0 for us is LDM, a rugged layer for weak-signal and DX work alongside a high-capacity layer for normal use, in one carrier. That's an attractive proposition for amateur television, and a network-attached reference receiver would be ideal for developing against.
For context, I'm the author of an open-source DVB-T2 receiver project for amateur use and a trustee of a UK amateur television repeater, GB3OO so this is ongoing development work rather than idle curiosity. Happy to share findings back.
Thanks for any insight.
Justin, G8YTZ
