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Old 2008-05-26, 08:19 PM   #1
El Gran Chico
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Default My SBGH vs My CM4221

First off, this was really easy to build! I'm the kind of guy that has trouble hammering in a nail straight or putting together something from Ikea. And I don't have anything more than basic tools.

Here's what I used:

Element - 1/4" aluminum rods from Metal Supermarket (I wanted 3/16" but they were out of stock), about $10
Backbone - about 5 feet of 2x4 in 3 pieces, left over from a previous project. Joined in a "T" held together with 4 long woodscrews
Reflector - a piece of board from Rona, 2' by 4' (about $4) - the kind of stuff that's used for backing on a bookcase, plus ordinary tin foil. Tin foil attached to the board by duct tape, the reflector attached to the backbone by 4 nails
The rest - 6 1.5" #7 woodscrews from Home Depot ($2), 6 large washers from Home Depot ($1), one balun from my stash of 1970s tv parts

Tools Used:

Hack saw to cut the rods to length, and trim the board to 2' by 3'
Electric Drill to drive in the woodscrews to join the 2x4 pieces
Hammer from the nails to attach the reflector
Scissors to cut the duct tape
Screwdriver to attach the element and balun

I bent the rods by hand by measuring and marking the points with masking tape and found a suitable hard spot outside my house to use as a pivot to make the sharp turns (not so easy with 1/4' ).

I did some preliminary tests against my incumbent CM4221 and my SBGH is a worthy challenger. I'll post the results as testing progresses.


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Old 2008-05-28, 11:14 PM   #2
El Gran Chico
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Cool Testing: CM 4221 vs. my SBGH

As mentioned in post 446 ....

Test 1: I couldn't get my SBGH anywhere near where my CM 4221 is mounted, so I found the next best place. It was about 7 feet lower, and I eyeballed it to match the orientation.

Result: The Buffalo and Hamilton channels were all weaker on the SBGH (due to height?) while the Toronto local channels were all stronger, some by a lot, even on channels 65 and 66. I think it's possible the SBGH may have been slightly pointed closer to Toronto.

Test 2: To get it closer to where my CM 4221 is, I needed to take the reflector OFF. It was almost at the same height, but I could not orient it the same way. It was pointing roughly 15 to 20 degrees west (away from Toronto and towards Hamilton) as compared to the 4221.

Result: The Buffalo channels were just slightly weaker than the CM 4221 and the CM 4221 is pointing pretty much straight at Buffalo! myTV on channel 34 was the one exception that was significantly weaker but still had a stable lock. The Hamilton stations were expectly stronger than the 4221. The Toronto channels were generally just slightly weaker with a couple of exceptions - SRC on channel 24 was much stronger on the SBGH, and SunTV on 66 was slightly stronger. CITY on 53 was much weaker but still had a stable lock.

Hypothesis: I think if I add a reflector and mount my SBGH so I can aim it properly, the SBGH will kick the pants off my CM 4221. The SBGH seems to be performing well at wide angles that I'm subjecting it to (when I aim at Buffalo, Toronto is about 50 degrees left and Hamilton about 50 degrees right), even on channels above 51.
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Last edited by El Gran Chico; 2008-05-28 at 11:16 PM. Reason: Reference to earlier post
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Old 2011-10-18, 11:56 PM   #3
be236
 
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Location: Everett, WA
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Good posting and comparison report!

I've got a CM 4221 old style too... wonder if I can hack it for better low-UHF gain.
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