[dmfdmf]

Originally Posted by vt6364

I setup a dipole antenna following dmfdmf's instruction and confirmed RCH4 is available. Didn't work at first, but after some adjustments and aim it instead of just south-wall mounted, I was able to see 4.1 and 4.2. It's interesting how precise the aiming & dimension must be for this rudimentary indoor setup to get a clear picture (even from a LOS source). Simply changing the T-length by about an inch would cause it to pixelate, and about 3” would lose reception all together.

That's good news. The difficulty is probably due to a number of factors such as VHF-Lo being difficult to pickup, homemade antenna and indoor mounting (with your body right there to change the field and impedance). At least you confirmed you are not chasing a ghost.

Will get the popularly recommended ANT751 & a TVPRAMP1R, and try them out next weekend. Then will keep one antenna that works and return the other -assuming I won’t accidently drop it from the 2nd floor window, or trip and land myself on it during this many trials

This is teleview idea and what I called Plan-A, I would focus on this as this probably has the best shot.

Will also try pointing the DB8e at other mountains for reflected signals as teleview suggest; I still have some 20 days to return it.

This is a good idea to do more testing till the other antenna arrives. The more you can test the signals the better chance you have of finding a good configuration. If you can still return that antenna I'd be reluctant to do any testing or modifying for fear of damage then you'd be stuck with it.

Yes I read about FCC rulings. Attic installation is still preferred, simply because it’s a lot easier. My house is facing N-NW, and we are in small lots on a hill side, with the house to my east higher than mine. To get east channels, the antenna better be in the frontal-most part of the house to avoid having to reach higher than east-neighbor’s roof, and I don’t like having an antenna in front of the house myself, regardless of whether the HOA cares. The only pocket of attic space I have is luckily in this front part of the house, but it’s tiny.

These details are the tricky part of an antenna system as online advice can only go so far and these specifics make a difference. It sounds like the attic is so small that you could not really separate the DB8 into two DB4's anyway so the ANT751 will probably fit better in that tight space.

- Is it detrimental to put antenna on a flat roof (asphalt shingle)? I have such an area of one-story roof in the back (the front part is 2-story with gable-end tiled roof). If I cannot get anything from the attic at all, I am thinking I’d build sort of a wood stand, attach it to the roof to hold the south-aiming antenna in proper orientation; still easier than erecting a mast. My south view is mostly clear looking down hill, no need to go high (the 40/40 and 13/13 channel towers are visible from my back window).

Again, hard to judge without seeing it but is this an actual outdoor location? That would be the best. Putting an antenna right on top of an asphalt roof might not work well but you could try it. Is the area in the attic the part of the roof covered in ceramic tiles? Hmmm... that seems like its going to really block the signals inside the attic.

- After trying the DB8e outside my front window, I also tried pointing half of it at 80degT, and lost many channels. Did not record exactly which ones were lost though, just quickly concluded that I need a full DB8e, even for outdoor.

If you have the antennas coupled (per the design) and then aim them in different directions you will get multipath and trashed signals. This antenna is designed to be installed high up in free air and in a fringe area where signals are weak and reflected singles are weaker. Can you physically separate the antennas and use one as a DB4 for testing? Plug the TV directly into the balun for that antenna. Also, rezero your TV tuner once in a while because with all this testing and rescanning its going to pickup spurious parameters.

- I did try pointing the 2 halves of DB8e separately to 180degT and 80degT in the attic. But they were still right next to each other, both connected to the DB8e’s combiner. Results were pretty much the same as when they both pointing at either direction. This is probably due to reflected multipath, since I don’t see as many South channels when outdoor pointing 80degT (only the RCH40 and RCH28 I think). So the DB8e (and any reflective-disc style) is more prone to multipath than the Yagi-style 751?

A coupled antenna of any type is going to be prone to multipath. The Yagi style has a more focused beam so maybe less multipath trouble.

To dmfdmf, Do you still think it’s worth rigging up 2 DB4s (if the 751 doesn’t do)? There is very little space (that is >= 40” hi for the DB4s) in the attic, so they will not be more than maybe 2-3 Ft apart in there. I am curious how you modify it to improve VHF (at the cost of some UHF performance I assume?), but not sure I’d spend $160 on the DB8e to experiment. Is the mod reversible and I can still return it?

My Plans B & C were based on the assumption that you could not return the DB8 and didn't want to buy another antenna. Also, I was assuming that there was enough room in the attic to get at least 10 to 20 feet of separation, if you pile them up in one corner multipath will be a problem even if you notch channels. I'd return the DB8e.

That said ;-) the VHF mod is pretty simple, reversible and I'd be curious how it does. You have to start by extracting one of the DB4s as a stand alone antenna. On the back of the balun input are two set screws shown here; http://imgur.com/K9aeFDv
These are the inputs from the feed elements into the balun. The trick is to get a piece of 8 or 10 AWG bare copper wire and fold a loop on the end and smash it with a hammer so it makes a thin spade-type connector. Attached a straight piece of wire on each balun input measured for VHF reception. It should look like this;

>|<
~~
>|<

Where the tildes (~) represent VHF elements coming off the balun set screws. Be very careful not to over tighten the set screws with the attached wire, just make it snug for contact and support the ends of the VHF element at the end of the reflectors with zip ties and/or small pieces of plastic pipe or tubing you have lying around.

For RCH4 each element would need to be 3ft 5" but you could probably get away with 3ft elements and that might be short enough to get VHF-Hi channels RCH13/CBS from the south or RCH9/ABC from the east.

Thank you all. You folks are really amazing, not just because of your knowledge, but also for how you’d spend the time to read and answer people’s questions like this.

No problem. I hope it works in the end.