Great reception on laptop, bad on HTPC

[millrbrew]

I am experiencing a very odd problem. I have an HTPC with a TVW750USB tv tuner with rabbit ears hooked up. I've had issues with PBS and ABC in WMC for several years and am constantly adjusting the antenna. I've tried the MOHU Leaf and recently an amplified Terk indoor antenna too. I figured it was the room I'm, as there are no windows facing the broadcast towers. But on a whim today, I put the tuner in my laptop and presto, I got ABC, PBS, and even a few other channels I never got on my HTPC perfectly.

The laptop and HTPC were right next to each other and the antenna was not touched. I put the tv tuner back and forth five times. Each time, channels came in perfectly on the laptop but cut in and out constantly on the HTPC, all without moving the antenna. Stronger channels like NBC and CBS work perfectly on both systems. I removed then reinstalled drivers for the tuner on both machines and set up a new tv signal in WMC for both as well. I ran the signal strength utility in WMC on both computers and it seems the actual signal strength for all channels is identical. I'm not a hardware expert, but by process of elimination, it must be a difference between the two systems that is causing this issue.

Anyone have any idea what could possibly account for such a difference in reception between the two computers? I'm stumped, but obviously would really like to get a constant signal for my most watched channels.

Thanks.

HTPC - Windows 7 64 bit, 5gb ram, Asus M4a785-m with ATI HD 4200 integrated graphics, AMD Phenom x4 9650 quad core 2.3Ghz
Laptop - HP Pavillion dm4, windows 7 64 bit, 4gb ram, Intel i5 2.26Ghz, Intel HD GMA

[STC]

It could be a noisy PSU on the HTPC. That or some kind of ground loop. Ultimately a part on the HTPC, or perhaps through your house wiring inducing interference.
When you tried the laptop was it plugged in or running on battery?

[millrbrew]

Thanks for the reply.

The laptop was running on battery at the time. I could try plugging it in to check. When you say noisy PSU, you're saying the power supply could be generating interference? Any chance a pci card could get better reception rather than a USB stick?

[Crash2009]

Un-related to the PSU suggestion, but have you tried different USB inputs on the HTPC? (front VS rear)

[STC]

^ Good suggestion from crash.

You're probably in for a sh*t fight.
If it is source power related, even plugging in the laptop PSU, may not change your results due to its ability to isolate the interference if its coming from your house wiring. Some decent PSU's do this better than cheaper ones. If it does get worse though you will have found the problem.

[millrbrew]

I have tried both front and rear usb ports on the HTPC and it makes no difference. My PSU definitely qualifies as a cheap one.

I appreciate the insight folks. I'll let you know if the laptop plugged in changes the reception at all. My wife's been working on it for the last few hours so have not gotten a chance to test it out yet.

[foxwood]

My PSU definitely qualifies as a cheap one.

There's a good deal on a 430 Watt Corsair 80 Plus Bronze PSU on Newegg at the moment - only $20 after coupon and MIR.

[dmagerl]

Its a USB tuner, right? I would try moving it as far from the computer as possible. Use an extension cable to put some distance between it and the computer.

Also, I wonder if the computer is unable to provide enough power to the tuner. Maybe try using a powered usb hub between it and the computer andd see if that changes anything.

I would think its more likely to be noise generated within the PSU/htpc rather than noise coming in the powerline.

Finally, I assume its an amp'ed antenna. Make sure that both the antenna and computer are plugged into the same outlet and see if that works.

[millrbrew]

I have verified that the laptop is able to tune in more stations with fewer (no) dropouts on both battery and ac adapter.

I'll try your suggestions, dmagerl. I've used both amped and non antennas, but when amped, the antenna was plugged into the same outlet as the computer.

Perhaps it is time to invest in a new power supply.

[Crash2009]

Another suggestion on the subject of USB, and I don't know if it even makes a difference. Which USB port are you using on the laptop? I read "out there somewhere" that 1 of those laptop USB ports are "special". Have you tried all 3 and do you get the same good results?

[millrbrew]

Crash, I tried all the laptop USB ports and they all seem to get great reception.

However, I took dmagerl's suggestion of using a usb extension cord to position the tuner further from the htpc, and receptions seems vastly improved. It's still not as perfect as with the laptop, but much improved, and completely watchable. The powered USB hub did not seem to make a difference.

Thanks for your suggestions.