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Discussion Starter · #1 ·
I've been playing around with the AD 91XG and the Extreme Signal HDB91X. Something about those antennas I think just a great design. A lot of questions have come up about durability in the past guys finding X elements and their yard after a windstorm etc etc....

I discovered this antenna. It's made in China but sold by an Australian company DigiTek.



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The interesting thing about that antenna is,
it looks like the active element is actually an X element too
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Ness Electronics out of Minnesota was selling these for a very, very reasonable price plus shipping. So I bought six of them. I just want to experiment. I'm probably going to make an extra long version and then try ganging four of them.

I get to put one completely together simply because I am documenting with pictures how this antenna is constructed.. it appears to be a 91xg clone but only in appearance. First of all the Boom is only two sections not including the mounting brace. The Boom is also constructed from Steel and is powder-coated. It almost looks like the old finish they put on typewriters "back in the day"..

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Cross section. I believe there's a little bit of powder coating hanging over the edge but it does look a bit wavy:
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Note the finish. I believe it's powder coating but it's textured also.
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Here's the kit. Four bags of 5 X elements + one bag of two elements. 2 booms plus the mounting support. Also some screws were loose in the bag. Did I mention that this doesn't come in a box? 馃摝

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This is how they come. I'm not so sure I agree with the packaging. Obviously this is a package for mass shipment. Maybe when they're sold individually in Australia they come in a box?
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Another unique thing about this antenna where the X elements mount, there is a plastic mount riveted to the steel boom. For the life of me I can't figure out why they just don't clamp them to the Boom unless it's some sort of patent infringement? :

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In the next couple of posts, I'll post some close up pictures of the X elements and the driven element and later I'll assemble one.
 

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Discussion Starter · #2 · (Edited)
Here's the Digitek director. It truly is a copy of the Antennas Direct 91XG down to the shape & size but the mounting / attachment is slightly different because the boom has an adapter riveted on:
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Here's the DigiTech SX-91 aluminum director:

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Here's the 91XG director:
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Here is one over top of the other;
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Here is a comparison:

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Here you can see the two directors compared to the Digitek SX91 driven element. I was thinking how convenient it would be to use the driven element as directors for a repack design...
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Another interesting thing about these directors although they are similar and designed the actual metal part is encased all the way around with plastic so it would be much harder for them to pop out.

In other words, on the antennas direct design the metal element that can pop out of the plastic bracket easily but not on this design. You would have to melt the plastic or cut it with a saw to get the metal element out as they are actually molded in:

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I believe these are the DVB-T freqs they used in Australia once upon a time. They use 8 MHz channels with DVB-T.
Like here they carved some spectrum for other uses from UHF TV. So even there, ideally one would wanna re-scaled design to match the new TV spectrum.
Code:
ch 21    474
ch 22    482
...
...
ch 68    850
ch 69    858
 

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Discussion Starter · #4 · (Edited)
Here's some pictures of the active element:

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I use the blue Loctite gel. A little excessive but I wiped it and added it to the other stud and some other fasteners.
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Discussion Starter · #5 · (Edited)
I believe these are the DVB-T freqs they used in Australia once upon a time. They use 8 MHz channels with DVB-T.
Like here they carved some spectrum for other uses from UHF TV. So even there, ideally one would wanna re-scaled design to match the new TV spectrum.
Code:
ch 21    474
ch 22    482
...
...
ch 68    850
ch 69    858
expand...
Thanks Major Tom.
You read my mind already. Since I'm already working on the 91XG repack design, I wonder about this one also, so I'll probably apply what I learned on the 91XG to the SX91.

Since I have six of these, now I'm thinking about making one extra long like I did my 163 XG. Once you get past the last few elements at the front of the antenna how important do you think the X element spacing is?

Seems like the spacing is similar to the 91xg and odd spacings not always incremental in the mostly 5 1/2" in the last third of the antenna towards the front.

I have the spacing measurements written down maybe I can post them here.
 

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Discussion Starter · #6 ·
I tried to put spaces in between the CM and Inches but the forum automatically takes the spaces out, sorry.


CM. Inch"
0. 0............Reflector.
19.5. 7.25"..........Active element
21. 8.25" 1st element rod
23.5. 9.25" 1st X element
26.8. 10.5" 2nd
30. 11.75" 3rd
35. 13.75" 4th
39.5. 15.5" 5th
45.5. 18" 6th
50.5. 19.8" 7th
55.5. 21.8" 8th
61. 23.9" 9th
67. 26.25" 10th
75.5. 29.75" 11th
86. 33.8" 12th
98. 38.5" 13th
111.2. 43.75" 14th
125.3. 49.3" 15th
139. 54.6" 16th
153. 60" 17th
167. 65.7" 18th
180.8. 71.2" 19th
195. 76.9" 20th
210.8. 83" 21st
224.5. 88.4" 22nd


 

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I tried to put spaces in between the CM and Inches but the forum automatically takes the spaces out, sorry.
You can do this with BBCode. Wrap the list with 'Code' statements.
Type an opening square bracket (i.e. [ ) followed by the word Code and then a closing square bracket ( ] ), then type out your list, then end with another opening square bracket and a backslash with the word Code ( /Code ) and a closing square bracket.
I know it's not really 'code' but this will maintain spacing and give you a monospaced font.
 

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Discussion Starter · #8 ·
Thanks maybe I'll try that BB Code thing later later when I get some time if there is any interest in this.

Right now there doesn't appear to be much interest. It's more of an informational post anyhow. I have six of these SX91s. I do plan to gang four of these. I also plan to make one super long.
 
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