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Discussion Starter #1
I’m new here. I’m not sure where to post. If I posted in the wrong place please excuse me.I have been browsing the forum for while now. I want to thanks everyone that contributes their time and knowledge to develop and research different kind of antenna. I finally finished build original SBGH6 with Narods. I got the design from here http://mysite.verizon.net/res11d41p/id2.html. Thank you so much for the design. It is not perfect, but I got a decent result. I used #6AWG for the element and 3/8 aluminum pipe for the reflectors and ½ pvc for the frame.


Here is my tv fool: http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id=8d17e7cb42e562
I have some problem on real channel 12 and 7. As soon as it get dark outside the signal is gone. Here are all the channel that I got so far: 23,49,32,7,29,30,38,39,12,44,33,19,43,41,45,34. All of the channel received about 50% signal except 23,49 about 90% to 100%. 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.
 

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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.
 

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Discussion Starter #4
Wow, thank you both for the fast respond, I’m really appreciated. In respond to Nikiml I’m pointed at about 157 degree magnetic direction. I have question about your GH 10n3. I went to your website and look at your GH10n3, I can see all the measurement when I pointed to the elements or the reflectors, but what I don’t understand is, the 3 separate number at the end of each reflector for example on the GH10n3 top reflector with round end (-96.5,285.9,661.5). One other thing how do I figure out the space between the reflectors and the height between the reflectors and the elements (http://clients.teksavvy.com/~nickm/gh_n_uV/gh10n_6V9_14u65.html) sorry I’m real new to these.
Thanks 300ohm for your suggestion to experiment the high and the lower. I will try to do that when the weather permit. Right now I have it on the roof about 25 feet of the ground. 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? Or can I combine 2 antennas to one cable?. Assuming that I just want to have 1 antenna to avoid running 2 cables from the roof, which one do you thing would be appropriate for my situation GH10n3 or DBgh6.
 

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Wow, thank you both for the fast respond, I’m really appreciated. In respond to Nikiml I’m pointed at about 157 degree magnetic direction. I have question about your GH 10n3. I went to your website and look at your GH10n3, I can see all the measurement when I pointed to the elements or the reflectors, but what I don’t understand is, the 3 separate number at the end of each reflector for example on the GH10n3 top reflector with round end (-96.5,285.9,661.5). One other thing how do I figure out the space between the reflectors and the height between the reflectors and the elements (http://clients.teksavvy.com/~nickm/gh_n_uV/gh10n_6V9_14u65.html) sorry I’m real new to these.
The three numbers are the x, y and z coordinates of the end point. You can figure out the height distance of two points by subtracting their z values, the depth distance by subtracting the x values and the left-right distance by subtracting the y values ( just look at the coordinate system in the middle for reference).

Alternatively you can select two elements ( line and line, point and point or point and line) by mouse click - they will turn pink and then you will see x,y,z, delta_x, delta_y and delta_z info at the top of the 3d window. Double click anywhere to clear the selection.
 

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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.
 

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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.
That is probably a good idea - I pick the SBGH, which one do you pick? :D

Do you have ready parametrized models for those?

Actually I have a parametrized model for the SBGH. Just don't know the parameters values...
 

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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.
 

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Hey, it looked decent to me. :p

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. :cool:
 

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Discussion Starter #12
yes I do have some aluminum tub left about 20", but I can always get some more from the hardware store they are about $.98 a foot. I see that your guy talk about retrofit SBgh6. I just wait to see if you guy come up with something before I start the new project. thank you both so much for helping.
 

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Discussion Starter #14
HI Nikiml
I decided to build the GH10n3 as 300ohm suggested I need you help with the measurement from you site. What I did was I clicked and highlighted between the 2 point and I can see the distance on the top either say DX or DZ. For example the distance between the top reflector and the one under is 183.4 mm. Is this correct? I just want to make sure I got the right measurement before I get started. Thank you.
 

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HI Nikiml
I decided to build the GH10n3 as 300ohm suggested I need you help with the measurement from you site. What I did was I clicked and highlighted between the 2 point and I can see the distance on the top either say DX or DZ. For example the distance between the top reflector and the one under is 183.4 mm. Is this correct? I just want to make sure I got the right measurement before I get started. Thank you.
Yes, this is correct.
Just that ( I haven't paid enough attention I guess ) there is another gh10n3 which is probably better if you want to put the 3 narod reflector from the start.

PS. I plan to post some more on gh6 gen1 retrofitting later tonight.
 

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Discussion Starter #16
thanks Nikiml. this Gh10n3 that you show me is this what it call a Non-modular UHF/VHF-hi. they seem to be little smaller then you other Gh10n3. Are they better because they are higher gain?. I'm also interested in the retrofit original gh6. I want to start that project too when I finish with the Gh10n3. thank you.
 

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Discussion Starter #17
Nikiml forgot to ask you about the 3rd reflector from the top (Non-modular UHF/VHF-hi gh10n3) it doesn't seem like it has any gap in between. Are they straight reflector with no gap? or there is a gap i can't see because it is so small. thanks
 

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Discussion Starter #19
It was challenge to make GH10n3, but I finally finished. So far signal gain is improving from 50% t0 75% for most of the channel. There is no more drop out at night on channel 7, but channel 11 is still unwatchable at night. I haven’t have time to make any adjustment yet. I’m waiting for the weather to clear out. Thank you for all your helps Nikilm and 300ohm.
Here is the list of material:
½ pvc signal spin (It is a little soft, but manageable. I have made some adjust for the alignment of the spin)
3/8 aluminum pipe
6 gauge copper wire
Hot glue and screws
Flexi glass
I like to post some pics but not sure how
 
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