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Discussion Starter #1 (Edited)
It was mentioned that a thicker active element would increased the gain slightly. I found this copper tubing on-line at Home Depot. I already have some rectangular aluminum rod that is 68mmx2.5mm (WxT) that I plan on using for the reflectors. If I use the tubing, is it best to leave it open on the ends or crimp it like the image in post 90. I don't want to use a screen as I would like to try to capture some stations that are 165 degrees behind my main antenna farm. This will also be an attic installation.

http://www.homedepot.com/webapp/wcs/stores/servlet/ProductDisplay?storeId=10051&langId=-1&catalogId=10053&productId=100485927&N=10000003+90051"]http://www.homedepot.com/webapp/wcs/stores/servlet/ProductDisplay?storeId=10051&langId=-1&catalogId=10053&productId=100485927&N=10000003+90051
 

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For the tubing, you can leave the ends open in an attic installation. I think the main reason they crimp the ends on a commercial antenna is so that water doesnt get in, and it stops whistling from the wind.

Thats pricey aluminum bar you plan to use for the reflectors. Since the signals are 165 degrees apart, I would try it first with no reflector. If OK, then you could save the bar for some other project. Of course, build the frame so reflectors could be put on easily.
 

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It was mentioned that a thicker active element would increased the gain slightly. I found this copper tubing on-line at Home Depot.
I would recommand that you use at least a rod reflector for your antenna. Using the antenna without any reflector leads to poor gain, as my first build shown earlier. The graph made by Autofils clearly show that using the SBGH without any reflector leads to performances worse that CM4221.

So unless you are very close to the transmission antennas, use the rod reflector that allows good gain from the back (in fact, the reflector could be made of cheap wire since this is an attic installation). And wear safety goggles when installing it...
 

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So unless you are very close to the transmission antennas, use the rod reflector that allows good gain from the back (in fact, the reflector could be made of cheap wire since this is an attic installation). And wear safety goggles when installing it...
Yep, use something cheap and skinnier, like clothes hangers or fencing wire.

Using 68mm wide aluminum bar stock times 6 equals 408mm, so more than half of the reflector area is covered. Not much signal is going to come from the back with that wide stuff.
 

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Discussion Starter #5
Yep, use something cheap and skinnier, like clothes hangers or fencing wire.

Using 68mm wide aluminum bar stock times 6 equals 408mm, so more than half of the reflector area is covered. Not much signal is going to come from the back with that wide stuff.
I guess I need to measure twice and type once. The aluminum I am planning to use is 18mm wide, not 68mm (measure it from 50mm to 68mm).
 

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Galvanic corrosion risk from using different metals?

i tried to build my antenna but I seem cant find a good, easy to cut and cheap material for it. I looked at Home Depot, Rona and Canadian Tire but I was unlucky. I went to a second hand store and there I found an aluminum wire - about 2mm in diameter.
After I built it and tried it on my Sony "HDTV", I assumed I would get a digital reception, but to my dismay I only have NTSC tuner. So, I'll have to buy my ATSC receiver or buy a new HDTV with an ATSC tuner (I'll make sure next time).
But my concern right now, how is my antenna, made out of aluminum, would compare if i would have used another material like copper?

Thank you in advance....
 

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But my concern right now, how is my antenna, made out of aluminum, would compare if i would have used another material like copper?

Thank you in advance....
Copper and aluminum provide very similar performance. But for outdoor use, since there is a small electrical current, galvanic corrosion will occur with dis-similiar materials over time in the presence of moisture, ie the copper wire from the antenna lead and the aluminum.

Good time to post a galvanic corrosion chart, heh.
Code:
Magnesium-------------------------- Corroded End
Zinc-------------------------------------^
Aluminum---------------------------------|
Cadmium----------------------------------|
Steel------------------------------------|
Lead-------------------------------------|
Tin---------------------------- Metals above here ^
Nickel------------------------- protect those below
Brass------------------------------------|
Bronze-----------------------------------|
Copper-----------------------------------|
Nickel Copper Alloy----------------------|
Stainless Steel--------------------------|
Silver-----------------------------------|
Gold-------------------------------------V
Platinum--------------------------- Protected End
The farther the metals are apart on the chart, the faster galvanic corrosion will take place.
 

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But my concern right now, how is my antenna, made out of aluminum, would compare if i would have used another material like copper?

Thank you in advance....
To give another answer in addition to galvanic corrosion, heres a chart of
Wire conductivity from the NEC manual :

Below a wire conductivity table to be used for LD card type 5, wire loading

Material Conductivity
S/m
Perfect 9.9e99 (lossless)
Silver 6.29e7
Copper 5.80e7
Pure Alumin. 3.77e7
Al. 6063-T832 3.08e7
Al. 6061-T6 2.49e7
Brass 1.56e7
Phospor bronze 9.09e6
Stnlss Stl 302 1.39e6

As you can see, copper is more conductive than aluminum, but its also heavier.
 

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Aluminum Wire Is Perhaps Too Light?

I tried building an SBGH with #12 Al wire. I was hoping that it's greater sensitivity would compensate for the fact that it was aimed about 10 deg off axis without a reflector. It is mounted on a glass panel room divider and looks like a funky Aztec design.

CBUT showed a dramatic improvement. But my joy was short lived as all other channels came in no better than with my silver sensor in its less than optimum placement.

Code:
                       Silver Sensor               SBGH
                   nominal          best
KBCB                 88              91             85
CHAN                 92              95             90
CIVT                 88              89             87
KVOS                 87              98             84
CBUT                 89              97             97
The aluminum wire is perhaps too light and the antenna sagged to an overall length of 780 mm. Adjusting back to 762 mm improved reception. As did using a cookie sheet as an ad hoc reflector.

Next, I'll try mounting it properly, check all dimensions, aim directly toward stations, add the reflector elements and try twisting two lengths of wire together to obtain sturdier elements.
 

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For indoor use, taping the elements to a large piece of styrofoam would be good. Also you could use another piece of styrofoam covered in aluminum foil as a great reflector. You could keep the correct reflector to element distance with pieces of styrofoam. If you dont have any handy, Lowes or Home Depot sell damaged pieces that will work fine at a large discount. Foam board at craft stores is another option.

and try twisting two lengths of wire together to obtain sturdier elements.
I wouldnt do that for the same reasons as listed above for the threaded rod.
 

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You can buy #9 aluminum wire from places like Home Depot. It works well and is easy to work with.

Look in the ceiling department. It is used to hang T bar. I thinK I paid about $8.00 for 100 foot roll.

Larry
 

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Since I had plenty of 10 gauge copper wire, I wanted to know what kind of a performance penalty I would get using it for the second section of my DBGH gen 1 with the 2 X 4 inch mesh screen versus using the same 6 gauge copper wire that the original one has. So here are the modeling results in Net Gain not Raw Gain and AGT = 1.0 (0 db). Middle of Channel 14 at the top going down to the middle of Channel 52 at the bottom :

6over6 --10over6
Net Gain Net Gain Difference
16.2227 16.2295 -0.0068
16.2843 16.2937 -0.0094
16.3481 16.3588 -0.0108
16.4255 16.4468 -0.0213
16.5371 16.5683 -0.0312
16.6923 16.7330 -0.0406
16.8699 16.9196 -0.0497
17.0485 17.1072 -0.0587
17.1975 17.2551 -0.0576
17.2576 17.3043 -0.0468
17.3107 17.3470 -0.0363
17.3344 17.3703 -0.0359
17.3186 17.3442 -0.0256
17.2242 17.2497 -0.0254
17.1310 17.1568 -0.0258
17.1433 17.1599 -0.0166
17.1603 17.1876 -0.0274
17.1539 17.1819 -0.0280
17.1347 17.1633 -0.0285
17.1132 17.1323 -0.0190
17.0698 17.0992 -0.0294
17.0248 17.0545 -0.0296
16.9386 16.9784 -0.0398
16.7512 16.8112 -0.0600
16.5031 16.5831 -0.0800
16.7488 16.8080 -0.0592
17.2111 17.2292 -0.0181
17.3937 17.4110 -0.0173
17.5070 17.5135 -0.0066
17.6118 17.6176 -0.0058
17.7281 17.7432 -0.0151
17.8651 17.8797 -0.0147
18.0115 18.0259 -0.0144
18.1356 18.1503 -0.0147
18.2349 18.2605 -0.0256
18.2870 18.3242 -0.0371
18.2702 18.3194 -0.0491
18.1754 18.2466 -0.0712
18.0066 18.0891 -0.0825

I also wondered if having the 10 gauge antenna on top or on the bottom would make a difference. Here are the results:

6over10 --10over6
Net Gain Net Gain Difference
16.2295 16.2295 0.0000
16.2937 16.2937 0.0000
16.3588 16.3588 0.0000
16.4468 16.4468 0.0000
16.5783 16.5683 0.0099
16.7329 16.7330 -0.0001
16.9195 16.9196 -0.0001
17.1072 17.1072 -0.0001
17.2452 17.2551 -0.0099
17.3045 17.3043 0.0002
17.3472 17.3470 0.0002
17.3704 17.3703 0.0001
17.3541 17.3442 0.0099
17.2495 17.2497 -0.0002
17.1567 17.1568 -0.0001
17.1599 17.1599 0.0000
17.1777 17.1876 -0.0100
17.1719 17.1819 -0.0100
17.1533 17.1633 -0.0100
17.1323 17.1323 0.0000
17.0992 17.0992 0.0000
17.0545 17.0545 0.0000
16.9784 16.9784 0.0000
16.8111 16.8112 -0.0001
16.5831 16.5831 0.0000
16.8080 16.8080 0.0000
17.2292 17.2292 0.0000
17.4109 17.4110 -0.0001
17.5134 17.5135 -0.0001
17.6175 17.6176 -0.0001
17.7431 17.7432 -0.0001
17.8796 17.8797 -0.0001
18.0259 18.0259 0.0000
18.1502 18.1503 0.0000
18.2605 18.2605 0.0000
18.3241 18.3242 0.0000
18.3193 18.3194 0.0000
18.2465 18.2466 -0.0001
18.0890 18.0891 -0.0001

As you can see, it was pretty much an exercise in futility, heh.
 

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Buy 2x4 mesh or Build It Yourself?

Hello.

After many days of reading this amazing forum, I'm getting ready to build a curved Gray Hoverman to try and catch channel 33 in Montreal.
I would like to know what kind of store would carry the 2x4 mesh.
Both Home Depot and Reno Depot in my area have only 2x2 mesh that I believe would impair reception.

Thanks for the very interesting info on digital home !
 

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Thats odd. 2 X 4 is the most common. The extra vertical wires in the 2 x 2 mesh wont help gain, but wont hurt either. It will increase wind load, so youll have to compensate with sturdier masting.
 

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Thanks a lot 300ohm

I will start assembly tomorrow then.

Not finding the 2x4 mesh: That shows the difference between Canada and the US. Somme stuff is hard to get up here.
My summer place is near Plattsburgh NY and next summer I will build another antenna, probably different thanks to the excellent research you guys do.

All the best !
 

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DIY Mesh for GH?

It seems to me that if a person is building a Gray Hoverman mesh version with a PVC or other firm frame they should be able to string their own mesh out of wire as needed, right?

Here's the winding chart I'm envisioning (not to scale) that doesn't use any vertical lines. It starts from the bottom left going up and right, then up and left, repeat, lather, rinse, repeat...
Code:
 |------------->--------------|^
^|-------------<--------------|
 |------------->--------------|^
^|-------------<--------------|       \
 |------------->--------------|^   (wire holes drilled
^|-------------<--------------|     in frame sides at
 |------------->--------------|^    2 inch centres)
^|-------------<--------------|       /
 |------------->--------------|^
^|-------------<--------------|
 |------------->--------------|^
^|-------------<--------------|
 |------------->--------------|^
 ^ Start
What would be the best AWG size for the wire, and would copper be the best wire or aluminum or steel for reflector purposes?
 

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Mclapp did that on one of his bowties by drilling small holes in the side of the pipe. Size wise, what you have handy is dandy, heh. Youll also need some tensioners. But with the reflector gap in the GHs, it makes life more complicated.

That shows the difference between Canada and the US. Somme stuff is hard to get up here.
It may be more local than that. Sounds like more of a demand to fence out some smaller critters up where you are than here. I cant imagine what though.
Still too big an opening for most snakes, heh.
 

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DIY Mesh for GH Using 1 Spool of Wire

If the wire size is flexible enough then the lower left start point could be locked into place (screwed in?) and each weave of the wire through the side holes would really need to be pulled very tight while still keeping the frame from wanting to bend inwards like an hourglass. Hmmm... worth some experimentation but I'm starting to think that store bought mesh would be more rigid due to the vertical wires.

Maybe this DIY design needs vertical wiring too but then linking all the junction points would be a pain! An over-under weave of the vertical wires through the horizontal wires would help, with the whole winding process starting at the lower left as 2" horizontal weaves, changing to 4" vertical weaves at the top left, and ending at the upper right:
Code:
Start at bottom left

      Vertical Down
      /
^ >>>V   >>>>    >>>>    >>>>    >>> END
  _____________________________________
^ ||--|---|---|---|-<-|---|---|---|--||
  ||--|---|---|---|->-|---|---|---|--|| ^
^ ||--|---|---|---|-<-|---|---|---|--||
  ||--|---|---|---|->-|---|---|---|--|| ^
^ ||--|---|---|---|-<-|---|---|---|--||
  ||--|---|---|---|->-|---|---|---|--|| ^
^ ||--|---|---|---|-<-|---|---|---|--||
  ||--|---|---|---|->-|---|---|---|--|| ^
^ ||--V---^---V---^-<-V---^---V---^--||
  ||--|---|---|---|->-|---|---|---|--|| ^
^ ||--|---|---|---|-<-|---|---|---|--||
  ||--|---|---|---|->-|---|---|---|--|| ^
^ ||--|---|---|---|-<-|---|---|---|--||
  ||--|---|---|---|->-|---|---|---|--|| ^
^ ||--|---|---|---|-<-|---|---|---|--||
> ||--|---|---|---|->-|---|---|---|--|| ^
  -------------------------------------
\    >>>>    >>>>    >>>>    >>>>
 \
   START     Outer lines are the Frame, not Wires
It could be done with one spool of wire and only one final cut.
:)
 

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DIY mesh

Thanks for the very interesting replies.

I thought about doing some soldering to build my own mesh.
But then, since you mention the gap, what would be the best specs for a reflector grid ? 2x4 or more ? 2x6 ?

About fencing for snakes: maybe there are some outside the island of Montreal so I will take a look at some other stores.

Wiring could be strung in two parts instead of the whole width, using the center post for strength. Question: is tubing better than wire ? Or can wire scatter the waves more ?

Hmmm. Looks like i'm joining the research team... OTA THE way to watch TV
 
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