Starting a new thread on this subject as the old one had drifted.
I have been investigating the problem with Patrice's reception of the 1.7 MHz DVB-T2 Paris repeater, and I think that I have the explanation.
During early Knucker testing, I tried to make it receive 1.7 MHz bandwidth DVB-T generated by the Portsdown and I was unsuccessful. On further investigation, it appeared that the tuner clock parameters were being incorrectly set for 1.7 MHz DVB-T/T2, so I corrected then amd the Tuner then worked well with 1.7 MHz bandwidth DVB-T. I included this "correction" in the production software for both Ryde and Portsdown and thought no more of it.
Patrice noticed that the Ryde software did not decode the Paris repeater; eventually, we found that the original "uncorrected" tuner clock parameters would successfully decode that repeater. I was mystified because they were not for 1.7 MHz bandwidth, but for 1.614 MHz bandwidth.
I have now found this table in the DVB-T2 standard:
Comparing the "Elementary Period" values with the Bandwidth values, it appears that the real bandwidth of 1.7 MHz DVB-T2 is actually 1.61443662 MHz. Perhaps it is called 1.7 MHz bandwidth to appeal to the DAB community, whose bandwidth slots are 1.712 MHz wide?
So, if setting up a "1.7 MHz" DVB-T or DVB-T2 transmitter, the actual bandwidth should be set to 1.614 MHz. I have confirmed that setting the Portsdown to transmit 1.614 MHz DVB-T results in a successful decode with the original unmodified software when "1.7 MHz" bandwidth is selected on the receiver.
Can anybody in the industry confirm my findings?
I will restore the original software in the next update of both the Ryde and the Portsdown, and so bring back compatibility with so called "1.7 MHz Bandwidth" transmissions.
Dave, G8GKQ
The DVB-T2 "1.7 MHz" Standard
Discussion about the Knucker DVB-T Tuner DVB-T Receive Software. See also https://wiki.batc.org.uk/Knucker
Return to “The Knucker DVB-T Tuner and Receive Software”
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