The maximum distance for a single Ethernet, Fast Eternet, or Gigabit Ethernet cable is 100 meters which comes to 328 feet. So, a 20 feet cable is well with the acceptable range. The cable that you have may have poor crosstalk attenuation. You might consider a higher quality cable if that's the case. A category 6 ethernet cable is much better than 5e which is better than 5. Basically, each higher category has more twists per inch to reduce crosstalk interference.
However before you go buying yourself a new anything, you should check the connectivity directly to your router with the shorter Ethernet cable that came with your Slingbox. That way you can use a process of elimination to determine if the problem is with your 20 foot cable or the Slingbox.
Oh but by the way if I buy a SlingLink or other ethernet wireless bridge, then it will work fine. So wireless is going to give me a stronger signal than a 100mbps wired cable?
LOL. No, that's what's called an upsell. The SlingLink isn't a wireless btw, it uses PowerLine Network Adapters to allow network connectivity over your electrical lines.
Thanks for the reply. I know I should have gotten the Cat 6, but there were good reviews for this one from MonoP****. It's a 100ft Cat5e 350MHz, not 20 foot. Not sure if 350MHz is good or not to handle the video.
My plan tonight was to do what you said, try it at the router. But before I went ripping everything apart, I wanted to make sure if anybody out there is using a long cable with their SlingBox. If it works fine at the router, that doesn't necessarily mean it will work with a 100 foot Cat 6 cable either if tech support is correct that you can only have a maximum of 20 feet.
BTW, this is an old house with aluminum wiring so I'm not sure how those bridges would even work, I still think a direct cable has to be better. Especially since there's enough problems getting one device working, I can't imagine throwing two more devices into the picture and hope they work too.
Just so you know:
My router and internet connection is on the second floor of my home. I have two computers on this floor connected to this router. I have a 100 foot cat 5e cable also running from this second floor router up to my attic then down to an ethernet switch in my basement. (I live in a 18th century historic home and cabeling issues can be challenging.) From the switch in the basement I have another 25 foot cat 5e running to my Slinbox Pro HD located on the first floor.
I have no problems with slingbox access and connectivity from either of my computers on the second floor (just can't watch from both of them at the same time of course - a slingbox limitation)
I only have the switch in the basement because I have a wireless access point also attached to it to give better wireless service on the first floor. I did not install the switch because it was necessary to reamplify the signal (which is a way to get past the 100 meter distance limitation, by the way.)