I don't know if the lack of a log entry is significant. It only seems to write stuff to the log when it's attempting to make the initial network connection or attempting to renew the IP addresses it serves to the local computers. If it drops the connection at some other time it doesn't seem to write anything to the log.
I don't think a traditional oscilloscope would help diagnose things even if it had the bandwidth - at least not unless the operator had a thorough understanding of the handshaking back and forth, etc. It's probably better to use a specially designed bit of test equipment like [link|http://www.flukenetworks.com/us/Cabling/Copper+Cabling/CableIQ+Residential+Qualifier/Overview.htm|this] jobby from Fluke. Of course, it's about $1000, and if one needs the one of the kit packages built around it then the price nearly doubles. :-(
The drop from the pole is fairly new, and I replaced much of the wiring on the back of the house and the first 2-way splitter a few years ago - before we got the cable internet - it made a big difference in the TV image quality, and the inside wiring is recent. I'm sure the stuff on the pole isn't put together as leak tight and as carefully as I would have done it (I'm rather anal about connections at times) but it's probably fine. Having a dedicated line for the modem would be wonderful, but I don't know if Cox is willing to do that if my signal levels are high enough and within specs. :-/ Since this area just went to digital cable a couple of years ago, they probably aren't anxious to come back (I think parts of their service area still haven't been upgraded to digital yet).
I tried the Java diagnostic software but it wasn't able to find the modem. I'll probably have to tie into it directly with my laptop (and set various IP numbers on it) before I can say that it won't work. At the moment it sounds like Cox has [link|http://homepage.ntlworld.com/robin.d.h.walker/docsdiag/index.html#cispdis|disabled SNMP] so I may be out of luck in using that software to poke around in the modem.
I know what you mean about wishing cheaper cable and internet options were available. :-( My only broadband options here are cable internet which is presently a monopoly. (I'm close enough to a station for DSL but supposedly "there's fiber in the path and we can't send DSL over fiber" or some such story). Supposedly Verzion is going to be offering FiOS [link|http://www.fairfaxcounty.gov/cable/regulation/cable_franchises.htm|cable service] in a while, but it may be several years (sometime before 2012).
Be aware that the FCC is going to end over-the-air analog TV service by [link|http://www.computerworld.com/mobiletopics/mobile/story/0,10801,105970,00.html|April 7, 2009]. I don't think over-the-air digital TV has a 90 mile range, so eventually you're going to have to make the jump to satellite or cable to see TV out in the sticks. :-( I wouldn't spend a bundle on upgrading your tower just for TV.
Talking about VSWRs and Yagis and such reminds me of my Dad. He loved Ham radio - he still has his General license and 4 character call sign.
Hang in there. I'll report back later - probably next weekend - if I have more information.
Cheers,
Scott.