[300ohm]

I’ m look for suggestion or improvement on this original SBGH6 with 2 narods. what should I do next build another one or modify this one.

Yeah, it looks like you need a little more gain on vhf-hi for your channels 7 and 12. You could build another of what you have for more gain and make it DBGH with NARODs, but I think ideally in your situation, you need two separate antennas.

I would build a GH10n3 for your 146 degree magnetic direction and use your existing SBGH6 for the 31 degree magnetic direction. Then run separate coax lines into an A-B switch at the TV.

I have some problem on real channel 12 and 7. As soon as it get dark outside the signal is gone.

Thats classic fading described here :
http://www.hdtvprimer.com/ANTENNAS/GlossaryA.html#fading

One possible solution is to experiment with various heights, both higher and lower.

 

[300ohm]

I’m thinking about using the antenna for 3 TV. So then which mean that I have to have A and B switch for each TV. Then I have to switch between A or B depending on what I want to watch. Is that correct?

The A-B switch method is just for one TV, just like using a rotor, except cheaper.

Or can I combine 2 antennas to one cable?.

Unfortunately, combining two antennas pointing in different directions will subtract gain from both antennas.

which one do you thing would be appropriate for my situation GH10n3 or DBgh6.

Tough decision. Do you already have NAROD reflectors on your SBGH6 with NARODs ? Do you have more 3/8" tubing on hand and in what lengths ? The original SBGH6 uses shorter reflector lengths than the GH10 models and like in my case I have more short pieces left than long ones, heh. (Sigh, I wasted quite a bit of material before I found out about 4nec2 )

Nikiml, maybe we ought to work on a n3/n6 retro-fit for the original SBGH/DBGH (with the slightly later added wider feedpoint of 89mm) since quite a few have been built.

 

[300ohm]

Actually I have a parametrized model for the SBGH.

Yeah, its in this this thread : http://www.digitalhome.ca/forum/showthread.php?t=121956

You could just start with that and optimize just for the 3 NAROD reflectors.

Then the next step for the original DBGH6n6 would be to figure out the most practical optimum minimum spacing distance between the two bays.

Then the step after that would be optimizing the phase lines. The standard 2 inch phase line spacing should work OK, or the mclapps 1 inch to 2 inch to 1 inch phase line, maybe a bit better. (either look to be superior to the AntennaCraft U8000 type method, heh.)
Personally, I would like to do phase line testing in real time when I could get the chance, and get all my ducks in a row, heh.

 

[300ohm]

Hey, it looked decent to me.

The thing is, as you've previously have noted, you can go crazy trying to optimize for every local situation, heh. Even while not perfect to the last .1 db or even .5 db, compromises always have to take place, to produce a good general practical and buildable model.

 

[300ohm]

I like to post some pics but not sure how

How to create a photo album and post pictures:
http://www.digitalhome.ca/forum/showthread.php?t=92167

 

[300ohm]

Nice work. I notice the big metal sheet around the Heatilator chimney outlet. That could be affecting reception, especially for channel 11. I would move it higher by at least a foot, preferably 29 - 30" from the last NAROD reflector.

In situations like yours, the possibility exists that the metal sheet and the Heatilator chimney could be used to your advantage, but it would take some height and distance experimentation.