Re: Croiset claims 4 = 1
- From: "DAB sounds worse than FM" <dab.is@dead>
- Date: Sat, 03 Feb 2007 12:07:28 GMT
DAB sounds worse than FM wrote:
And not content with a Nobel prize-winning discovery, he then goes on
in the same post to try and justify why he claimed that DVB-H
requires 30 dB higher transmitter powers than T-DMB when DVB-H is
transmitted at UHF and T-DMB in Band III. Remember that 30 dB is a
factor of 1,000, so if you take a typical BBC DAB transmitter using
10 kW he's claiming that DVB-H would need to use plenty of 10 MW
Can you provide a link to the highest power DVB-H transmitter, please?
There's lots of DVB-H trials and services now, so for your claim to be
correct then surely it should be easy to find some documentary evidence of
10 MW DVB-H transmitters?
You can start on this page, which lists lots of DVB-H services, usually with
transmitter powers listed on the individual pages for the services:
For example, there's this:
1000 transmitters from 5 W to 2.5 kW covering 75% of the country - about 40
So absolute worst-case (i.e. assuming 2.5 kW for each of the 1000
transmitters, which plainly isn't actually the case) works out to be 2.5 MW,
but that covers 75% of the country.
Other than that, the highest DVB-H transmitter I could find is 80 kW
covering the whole of Greater Sydney:
although I gave up looking by the time I got down to Poland, so maybe you'll
find your elusive 10 MW DVB-H transmitter in the P-Z countries?
The 80 kW transmitter in Sydney is interesting, though, because, well, it's
similar in dB terms to what the EBU predicts is the difference between DMB
in Band III and DVB-H at UHF, because the difference between a 10 kW BBC DAB
transmitter and an 80 kW DVB-H transmitter is around 9 dB (2 x 2 x 2 = 9
dB), and the EBU is predicting that the difference is around 12 dB.
You on the other hand are predicting that the difference is 30 dB, and you
even had the audacity to claim that the difference is 34.5 dB:
"12.7 + (16.6-15) + (19-12) + (17-2.2) = 34.5 dB"
Might I remind you that 34.5 dB equates to a factor of 2,818, which would
mean that comparing with a 10 kW BBC DAB transmitter than DVB-H would need
to use transmitters with power levels of 28 MW.
So far the highest is 80 kW, which means that your prediction is:
10 log (28 MW / 80 kW) = 25.4 dB incorrect, or incorrect by a factor of 350.
Out of interest, did you actually pass your mathematics exams at school,
I would normally in such circumstances suggest that you don't give up your
day job, but the incredible thing is that your day job is actually to do
with broadcasting transmitter powers and such like!!!!!!!!!!!!!!!!!
Steve - www.digitalradiotech.co.uk - Digital Radio News & Info
Find the cheapest Freeview & DAB prices:
- Croiset claims 4 = 1
- From: DAB sounds worse than FM
- Croiset claims 4 = 1