Chattanooga TN: Got Atlanta But Few Locals - Page 2

Since they are all VHF, that supports the noise theory and the cable leakage theory.

I don't have enough information to make anything other than wild guesses. Maybe after you catch up on your sleep you can make some tests that will tell us more.

Yeah, that is a crucial part. You need 3 things for it to work: grounding block, something to ground into and, uh, what's the third one? Oh, I don't remember, uh, oops?

I'm very impressed with the performance of your Digitenna, especially with the Tropo signals. At least you have some of your favorite shows to watch when you need a break.

If you have a coax wall plate in your apartment, I wonder if there are any cable signals present.

Hi Trip,

I came to this discussion late.

I wanted to make a point about RF grounds. Everything I've read says to get a RF ground the length of wire from what you want to ground to the actual Earth ground needs to be less than 1/4 wavelength. For all practical purposes, that's impossible at VHF, let alone UHF. A 1/4 wave piece of wire connected to an Earth ground with a gamma match makes a good antenna. You can see why the wire needs to be short. Grounding for lightning (DC) is another story.

You know I've battled multipath here and I've never been able to see any particular signature of multipath on the spectrum analyzer trace. I've seen some pretty ugly traces decode just fine and perfectly good ones not decode.

It's pretty hard to generate much noise on UHF from consumer equipment. If you're receiving distant stations okay but not a few close one, it's unlikely to be an RFI problem.

Your tests sure sound like it is multipath.

Chuck

What is even worse is dynamic multipath. No equalizer can handle that. Perhaps the cars wizzing past you on the nearby 24 freeway is the cause of your reception problems. You did mention that you decoded a station overnight. That is when the traffic is lightest.

According to your TVFool results, the 3 stations you can't decode are located at about 345 deg. and that direction has a freeway that is perpendicular to your LOS and is about a mile or two away.

I'm wondering if a full band FM trap like an HLSJ will help? The Radio Shack model only has 6db of attenuation at 88 Mhz, near where your local blow torch @ 88.9 resides.

To verify or disprove my theory that dynamic multipath is causing your reception problems, can you tune in analog stations WOOT RF6 or WYHB RF39 and see if you have ghosting that always seems to fluctuate? If so, it's the nearby freeway. I don't think any antenna (I saw your request on another sub-forum) will help since all your signals are coming from the top of the ridge via diffraction.

Is it possible to do a single scan on your spectrum analyzer and to store the result? Do this on an undecodable station a number of times and then compare each result. See if the amplitude across the 6 mHz band changes with each scan. That would indicate dynamic multipath.

Now, that is a barrel splice!

You can have all the signal strength in the world, but you need "symbol" quality. Use the HDHomerun's Config utility to tune your antenna.



You are just way too close to the towers for that very directional antenna you have. You will need something a bit less directional for the Chattanooga stations, but will need a large directional antenna for the Atlanta stations. Your best bet is two antennas with a combiner.

That doesn't sound good... sounds like you have an amplifier that is burning out those tuners.

The rev2 HDHomeRun (white, device IDs starting with 1013 and above) is probably the best tuner around for handling high signal strength. Also doesn't seem to be bothered by strong FM signals. Not particularly great at handling multipath though.

Using a highly directional antenna would reject off-boresight multipath but in my case that wasn't true for me. I get my TV signals as one-edge diffractions from a nearby ridge, so I tried using a CM4228 antenna hoping to get good reception on all the local stations but I couldn't. Replaced the 8-bay antenna with a 4-bay antenna (CM4221) and to my surprise, I got great reception on every station. According to Ken Nist, if the multipath signals from different directions all arrive approximately in-phase than they add giving you a much stronger signal. At my geographical location, I think that is what happened.

Congrats on the new gig, Trip. I've had dealings with both Henry Luken and Cliff Goodgame and they seem like good people. Last time I was at the building on 8th St they were just getting the dishes installed on the roof, and things were progressing nicely.

A little better on the multipath, but not all that much since it's just a newer rev of the same demod. Really strong signal handling isn't quite as good because of the powered splitter. Adjacent channel filtering seems to be better, probably from the switch from cans to silicon tuners.

Is that Digitenna the largest fringe version they make? I am looking to order one myself when I can locate a suitable vendor online. They appear to be a bit pricey but that large Duv element looks similar to the old Channel Master diamond elements that provided good distant UHF reception. For some reason, I don't think Solid Signal carries Digitenna, so will look for another vendor.

If you go with the Georgia Tech option, you might want to try something smaller. If defeating multipath or noise is the key, the antenna inside of the blind may not need to be full size for adequate reception. How big would the antenna need to be? I don't know. I'll guess bigger than a paper clip but smaller than your vhf bowtie. The smaller the antenna, the smaller the blind. A smaller blind "sees" fewer degrees for reception. I've been tempted to buy the Leaf antenna to try this indoors here.

You might try rotating your antenna to vertical to see if the multipath signals are polarization sensitive.

There is a blog at:

http://forum.tvfool.com/showthread.php?p=14434

that suggest rotating your antenna might reduce multipath interference. WRCB and WTVC are transmitting vertical polarization as well as horizontal polarization.