Loop with reflector for VHF-hi - Page 2 - Canadian TV, Computing and Home Theatre Forums

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post #16 of 47 (permalink) Old 2010-09-15, 10:01 AM
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Quote:
Originally Posted by jpasadena View Post
Dimensions are roughly the same as before: 23 inch diameter loop, reflector distance about 13 inches, reflector in the box is about 27 by 30 inches.
Is that box really that big? It is hard to determine scale in a photo, but it doesn't look more than 6" deep to me.
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post #17 of 47 (permalink) Old 2010-09-16, 12:10 AM Thread Starter
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Originally Posted by roger1818 View Post
Is that box really that big? It is hard to determine scale in a photo, but it doesn't look more than 6" deep to me.
Thanks for the heads-up. I was a bit off on the box depth. It is more like 10.5 inches, which is a bit less than the 13" in the original design by holl_ands.
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post #18 of 47 (permalink) Old 2010-09-16, 10:26 AM
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A beer can/soda can would be great in photos like that.
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post #19 of 47 (permalink) Old 2011-11-11, 08:50 PM
 
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In the early going, this antenna is the BOMB!!! After the transition I was having issues in receiving RF13 CFTO. On good days I was measuring 22dB if lucky, but signal would fluctuate too frequently to make this station watchable. I was using a version of the Scatter Forager in order to try and get it. So I knew I was right on the cusp, so I decided to give this antenna a try.

After building it an testing in the early going, I've been getting a very reliable an constant 24-25dB...rock solid.

Thanks for this antenna...at this point I may build a second one of these to replace my channel-cut yagi that I'm using to try and get RF9.

The only negative thing I found out, was that the Scatter Forager was inadvertently used to pick up RF11 in the opposite direction of RF13. Now with this antenna, RF11 is blocked somewhat. I'm still getting it, but it cuts out at times.

Other than that minor issue, I'm so happy with this antenna. Great job.

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post #20 of 47 (permalink) Old 2011-11-11, 10:05 PM
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The only negative thing I found out, was that the Scatter Forager was inadvertently used to pick up RF11 in the opposite direction of RF13. Now with this antenna, RF11 is blocked somewhat. I'm still getting it, but it cuts out at times.
With less reflector, you could increase the backward gain for ch 11 at the expense of forward gain of ch 13.

If you want forward and backward gain at about the same levels you have now, you could stack two loops with no reflectors together with a Winegard SD-3700 3000hm to 75 ohm coupler.

My builds/plans (not the latest models) are located here.
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post #21 of 47 (permalink) Old 2011-11-12, 12:58 PM
 
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Thanks for the suggestion 300ohm. The other bonus noticed since putting up this antenna, was that CFTO RF9 is now coming in stronger too. I have a channel-cut YAGI pointed to get that station (about 100 degrees off of the direction the RF13 antenna is pointed), but I think the Scatter Forager was interfering with its reception (possibly the two antennas out of phase with each other cancelling signal).

I think I'm going to build another one of these to replace the YAGI, thinking the beamwidth will be wide enough to get both RF9 and RF11 in one shot. I don't need alot for RF11, but obviously do need a little bit more than what I have now.

So in summary, two stations solidified (though most times, the programming is the same between the two), one station got weaker.

This is all being tested at the TV with the longest cable run (~120 feet with both a pre-amp and distro amp involved in the path).

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post #22 of 47 (permalink) Old 2011-11-12, 08:58 PM
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Just some building ideas. If I were to build jpasadenas vhf-hi loop with reflector as in post #1, this is what I would do:



A) eliminate the tee, the cross and the middle pipe sections outlined in red. The antenna would be connected to the mast with ubolts at the points circled in green.

B) stabilize the loop more by adding pipes with slanted tees (or slip on tees) shown by the lines in blue. I would drill a hole in one end of the pipes and slip them on the hoop, the same way jpasadena did as shown by the yellow arrow.

Since crosses are pricey, this should cost less and give more bracing to the loop.


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post #23 of 47 (permalink) Old 2011-11-23, 02:06 PM Thread Starter
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Originally Posted by Marbles_00 View Post
In the early going, this antenna is the BOMB!!!
"The BOMB" is a good thing, right? Curious about your build.
Indoor or outdoor? Can you post a pic?
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post #24 of 47 (permalink) Old 2011-11-23, 02:21 PM
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Question

Curious! If you can sweep the sides of the loop back slightly, would the beamwidth increase like it does with the 'Swept back M4' and the '3D SSH II' designs?

3D SSH III with ZZ4 refl. http://imageshack.us/user/jmsdigital
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post #25 of 47 (permalink) Old 2011-11-23, 04:03 PM
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Yeah to a point, maybe 15 degrees. But a loop has broad beamwidth to begin with.

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post #26 of 47 (permalink) Old 2011-11-26, 08:53 PM
 
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Quote:
Quote:
Originally Posted by Marbles_00
In the early going, this antenna is the BOMB!!!
"The BOMB" is a good thing, right? Curious about your build.
Indoor or outdoor? Can you post a pic?
Yeah, it's a very good thing. I ended up building a second one which covers in getting both CFTO and CHCH. The one facing CKCO ended up increasing the signal reception two-fold.

I've got pictures of both builds here. The first loop, the reflector was my old Scatter Forager antenna. The second one wasn't as elegant and I used tin foil for the reflector. All my antennas are attic mounted.

I still have to add build details of all my conduit cut lengths to my site.

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post #27 of 47 (permalink) Old 2011-11-28, 02:07 PM Thread Starter
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Great job on the builds! I also like your conclusion:
"...I can't build a better antenna than what I have at this point."

Those are very sturdy looking builds that should hold up
outdoors, if needed. As I wrote earlier in the thread, if
you know it's only going to be in the attic, cardboard and
foil are just fine for this antenna.

And 300ohm is right that the build could be streamlined
by mounting on a mast flush against the reflector, eliminating
the need for the middle strut.
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post #28 of 47 (permalink) Old 2011-11-30, 11:00 AM
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Marbles_00, how did you bend such a nice circle?

Link to my TVFool results is in my profile Homepage URL. I suggest others do the same.
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post #29 of 47 (permalink) Old 2011-11-30, 12:51 PM
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Quote:
Marbles_00, how did you bend such a nice circle?
See post #13.

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post #30 of 47 (permalink) Old 2011-11-30, 01:19 PM
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Ooops. Thanks 300ohm. I missed that post.

How would this loop do with circularly polarized broadcasts? Wondering if it would do better than a horizontally polarized antenna.

Link to my TVFool results is in my profile Homepage URL. I suggest others do the same.
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