Nova-TD-500 Tuning issues

I wanted to watch freeview on my PC so I bought a brand new Hauppauge Nova-TD-500 card. Unfortunately I found the picture quality to be exceptionally low – There were significant image artefacts and glitches where everything is fine if I plug the same cable into a normal TV. I tried a whole load of things but the solution was to buy an attenuator. Without the attenuator the card was useless.

For reference, this was my “why isn’t my nova-t 500 card working” checklist:

1. Is there a problem with the co-axial cable? No – because if I plug it directly into TV (i.e. not via PC) I get a good picture.
2. Is the signal too weak? No – because I tried a antennae signal booster -> No luck.
3. The Nova-t 500 has two inputs, am I using the right one? Yes, I tried pugging the co-axial cable into socket 1 then socket 2 then socket 1 and 2 at the same time using a cable splitter – I get different results depending on what socket I plug the coaxial cable into but nothing solves the issue. For reference, If I plug it into the bottom input (the one closest to the IR port) I seem to get a slightly better signal on one tuner but ZERO-SIGNAL on the other but if I plug it into the top input I get equally poor signal on both tuners.
4. Is it just a problem with the software / application rather than the hardware? No, I tried DVB in different applications (I tried Kaffeine and Xine as well a MythTV) -> All give bad TV image.
5. Is my computer configured okay? I looked at whether DMA is on -> Yes, I’m using a SATA HDD. I checked that we’ve got the latest card firmware (/lib/firmware/dvb-usb-dib0700-1.20.fw). I experimented with the “force_lna_activation” and “buggy_sfn_workaround” module options -> No luck.
6. Is my computer fast enough? I compiled MythTV with VDPAU and checked CPU usage with “top” -> CPU usage is <5% so no performance bottleneck. VDPAU is only useful for HD content anyway??
7. Is there a problem with my card? No – I took it back to the shop and bought a 2nd one but got the same results. (opps!)
8. Is there a problem with electrical interference? I tried using electrical insulation tape in all places where the metal in the PCI card might be touching the metal of the PC case. Yes – This actually did help a bit which means that perhaps there’s some kind of EM interference inside the PC? Doesn’t this indicate a poor design by Hauppauge?
9. Is the signal too strong? Yes – because I tried a attenuator and it fixes the problem. 🙂 I guess the Nova-T card was being swamped and couldn’t pick out the digital signal from the analogue signal and other “noise”? With a variable attenuator you can gradually reduce the signal intensity – I think the idea is to find the correct intensity where the signal noise has dropped below the threshold that the Nova-T digital tuner can “see”. I don’t know why my cable has so much noise? Perhaps because it’s at least 20m long and runs parallel to the mains electrical circuit?

Additional actions you can take to get this fiddly Nova-TD-500 card working (relevant to UK Freeview television using a roof mounted aerial and coaxial cables).

1. Minimise the number of connections between the Nova-T card and the aerial. Each connection reduces the signal strength. I prioritise the Nova-T over other TVs because the other TVs don’t seem so fragile:
   • Path to Nova-TD-500 card: Aerial → cable → 2-way-splitter → cable → Nova-T card
   • Path to downstairs TV – Aerial → cable → 2-way-splitter → cable → 2-way-splitter → cable → wall socket → cable → Dreamcast splitter → Megadrive splitter → TV
   • Path to upstairs TV – Aerial → cable → 2-way-splitter → cable → 2-way-splitter → cable → wall socket → cable → TV
2. Use high quality cables, e.g. “WF100” coaxial cable. If possible, use as short a length of cable and avoid electrical wiring when fixing the cable. I bought some pre-made soldered cables from www.satcure.co.uk.
3. Improve the cable splitter. 2-way splitters pass approximately 40% of the signal to each output. In order to split the signal without incurring losses you need to use a powered amplifier. If you use a amplifier you need to do it at the aerial end rather than near the end-device, otherwise the amplifier also boosts the noise that has been picked up in the cable length and cable-joins. Unfortunately, I have no power sockets in my cellar so this isn’t an option for me 🙁 .