DVB-T/T2 tuner for weak signals

[NumberFive]

Hi,

Does anyone have a recommendation for a DVB-T/T2 tuner that is good at receiving weak multiplexes? When I am I can receive about 10 multiplexes on both a Panasonic TV (2012) and a Samsung TV (2014), all without a problem. Most of the multiplexes are strong (100 kW) and so are received with 10 signal strength, 10 quality, 0 Bit-error-rate. Two of the multiplexes are weak (3 kW), but are received with middle signal strength, max signal quality by both TVs (0 BER).

However, I have a Hauppauge Nova-T and an AstroMeta USB Stick, neither of which can receive the weaker multiplexes. They will on occasion pick up the channels on a scan, but can't lock a channel.

I've put a lot of effort into outdoor TV aerials, good Labgear distribution amplifiers, and good quality coax cables throughout the system, so I'm confident that what is getting to the back of the tuners is a good signal, just the TV sets seem to have better tuners than the PC does.

I appreciate that the Nova-T is really old at this stage and probably well surpassed by modern chipsets, and the AstroMeta is really cheap, so suggestions welcome!

[Graham]

A long time ago, the signal here was weak and the Nova-T was as good as anything else that I used. I still use a couple of ten year old Nova-Ts and I haven't seen anything to suggest that they get worse with time. My view is that if it can't be received with a Nova-T then it can't be received. But I haven't had reception problems since the transmitter power was boosted at about the time of digital switchover so I may not be the best source of information.

[NumberFive]

Hi Graham,

I'm not suggesting that the Nova-T cards get worse with time, I'm suggesting that more modern chipsets have better performance than older ones.

As evidenced by the fact that TVs from two different manufactures can receive my weak multiplexes with zero BER and the Nova-T cannot, despite my best efforts to avoid all obvious sources of interference, then the Nova-T must be behind the curve these days.

Interestingly the AstroMeta tuner seems to use good brand name ICs, but suffers from crummy RF design. Can't complain, was about £17 inc. P&P, but willing to spend more for good performance.

[bgowland]

Technically the tuning / locking of a signal doesn't have much to do with chipsets bearing in mind the UHF carrier is analogue. Yes, there will be analogue chips involved as well as discrete analogue components, *but* RF tuners and their theory have been around since radio transmitters / receivers were invented. The "best", most stable, most sensitive tuning circuitry was invented a long time ago - as to whether any manufacturer chooses to implement the "best" of course depends on limitations as a result of design / manufacturing costs.

I have four Nova-T (90002) cards and they've always behaved fine but then again I've always lived in a good reception area originally 20 miles away from Crystal Palace, now just a few miles from the Idle transmitter in W. Yorkshire (it's huge and on top of a blinking great hill). Interestingly, according to UKFree.TV Idle only broadcasts at 50W for each MUX.

Dumb-ass questions - do you have the correct aerial for the recommended band/group? Are you sure your distribution amps aren't adding to the problem, i.e., boosting the signal too much and causing increased noise-to-signal ratio?

[NumberFive]

Hi bgowland, thanks for the reply but that's not quite right. The technology used in DVB-T/T2 (high order QAM) is something that continues to be refined in modern radio ICs. This isn't a technology that has been long term stable. It's not just me saying so, for example:

"Second Generation DVB-T2/T/C Demodulator IC with
Substantially Improved Functionality and Performance
and Designed for Ease of Use"

http://www.sony.net/Products/SC-HP/cx_ne...34ER_R.pdf

I don't have a problem with my TV signal, I designed the amplifier/distribution system myself. Two modern TV sets are able to lock the signals just fine and demodulate them with zero BER. The Nova-T demonstrates that it is less sensitive (be that due to an inferior radio IC, or poor RF design), in that it cannot reliably lock the weaker multiplexes, and when it can the BER is so high the channels are unwatchable. I've tried a cheap DVB-T2 stick, but I've read elsewhere that it suffers from poor PCB design allowing the other chips on the board to cause interference with the radio IC.

I'm really hoping to hear experience receiving fringe signals. I do intend to buy a few different tuners myself, test them and report back, but would be helpful to avoid dead ends.

[martint123]

From reading on here over the years the conclusion I've come to is that domestic TVs are more sensitive than all computer tuners and no one can really say why.
It may not be by much but shows itself just at the boundary of signal/no signal. I've had mast head preamps, amplifying distribution boxes and new coax.
The only thing that got me a reliable signal from Belmont was to site the aerial on a 20 foot pole.

[NumberFive]

I've read similar observations on the forums over the years. I suspect the PC stuff suffers from poor RF design. Might crack open one of the AstroMeta sticks and see if there are any tweaks I can make that make a difference. I'll report back later when I break the AstroMeta.

[martint123]

I was up in the shack this morning where the headless server sits, coverless. One thing that leaped out was that the nova-t-500 is sat less than 1/2 an inch away from the video board with all it's highly strung and clocked devices. I haven't got access to a spectrum analyser any more, but there must be huge amounts of RF noise generated by the video card (and others).
The actual tuner on the nova-t, after removing the lid, seems to be as well constructed and laid out as a TV tuner.

[NumberFive]

Hi Martin,

Indeed, back before analogue switch off I had to wrap the Nova-T-500 in foil to get some of the weaker multiplexes. I'm reluctant to go back to that though I might experiment if I get time (mainly reluctant because at least one of the weak multiplexes now is a DVB-T2 one). I'd have thought the USB tuners would stand more chance being out of the RF soup inside the PC chassis, but then I've read reports of the PCB in the AstroMeta I have been poorly designed, and it's in a plastic box anyway. Might try putting it all in a metal box first (in case the noise is external), then if that fails I'll see what happens if I put a piece of foil around the radio IC. I might be able to borrow a spectrum analyser, but I know if I do I'll spend huge amounts of time on this!