AVS Forum banner

1 - 10 of 10 Posts

·
Registered
Joined
·
53 Posts
Discussion Starter #1
Hello all,

I am thinking about putting up a second tripod and mounting antennas to point at Canada. I live about 1 mile from Lake Ontario as the crow flies. So, most of the distance between me and the stations is open water (flat).

Here is my TV Fool report for reference:

http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id=f1f02a3893b9e5

I am mainly interested in CBC (RF 12 or RF 20 - need to click on pending, also have a LP station on 20 not listed) and TVO (RF 19 or 26). I can get RF 27 for obvious reasons.

Currently, I can receive RF 12, 19, and 25 (French CBC) on mostly clear/clear days nights. On other days, when I tune and I don't get them, it seems like the TV pauses longer than usual and then says no signal - on other stations where there is definitely no signal, it goes directly to no signal, so maybe that is a good sign...

I was wondering if any company sold a hardware package to do horizontal stacking. I read somewhere that this was good for distant stations where earth curvature came into play as well as getting about 2.5db gain and a narrower beam width. I currently run a single Winegard 8200U. I was thinking about getting 2 Antenna Craft Y10-7-13's because I've seen some experiments that this had the same/slightly better gain than the Winegard 7698 (cousin of the 8200U). I also could try stacking the HDB8x as well.
 

·
Registered
Joined
·
6,327 Posts
It's unusual to see a TV Fool report with no terrain between you and the transmitters besides the curvature of the Earth. Since you're not receiving the stations 100% you're relying on the atmosphere to bend the signals a bit.

I don't know what TV you have but my Sony will spend time trying to tune in a station that's just a little too weak to decode. If there's no signal then it says "No Signal." Based on this you might get some improvement with more antenna gain. It's also possible that you won't get 100% reception no matter what you do. You're 40-50 miles beyond the radio horizon and that's hard.

The reason you're receiving the stations on clear days is that's when there are some temperature inversions which bend the signals. Stormy weather breaks up inversions so you get no atmospheric help at those times. You really want to have reception during times of no inversions. That may be impossible at 92 miles.

Besides stacking antennas, getting them up higher will likely make some improvement. Stacking antennas and the curvature of the Earth have nothing to do with each other. The best you can hope for is about 2.5 dB gain stacking two identical antennas. My avatar show my stacked 91XGs and my homemade 12 element LPDAs. Click on my link for a better image.

I'm using a near lossless combiner, no ferrite. I simply use a piece of 50 ohm coax as a 1/4 wave matching section to match two 75 ohm antennas in parallel (37.5 ohms) back to 75 ohm coax. On UHF the matching section is RG-223 coax and is 3.3" long. On VHF it is 10" long. Attached is a photo of the combiner. The coax ends are soldered together in the little box.
 

Attachments

·
Registered
Joined
·
53 Posts
Discussion Starter #3
Yeah, I'm figuring it will be hard, especially since they are so far away and weak. I believe the Toronto stations (CBLT, CBLFT and TVO) are up on the CN Tower, and it's walking distance from the lake (a couple of blocks maybe, if that).

There is a hill between me and CHEX, but other than that, it's a clear shot.

I am quite familiar with inversions from my days taking meteorology courses in college. :)

What are you using for the cross bars? Is there a company that makes those mounts? (I guess that's my main question)

I am hoping to try at least and slowly buy parts. Unfortunately, I did run reports at different heights and it looks like one does start to get into positive db, but the size of the tower quickly approaches 1000 feet in that instance. I was looking to use off the shelf parts and do it relatively cheaply ;)
 

·
Registered
Joined
·
6,327 Posts
I'm not aware of anyone selling the stacking combiner. Most people just use a 2-way combiner and 2 equal lengths of coax. I found that has 0.5 to 1 dB loss. Considering you'll only get 2.5 dB max by stacking you don't really want to lose up to 1 dB in the combiner. That's why I built a 1/4 wave matching section combiner.

If the antennas you're stacking are 300 ohms and use a standard ferrite balun, you can pick up another 0.5 to 1 dB by making a coax balun instead.

I'm sure you would have to go to 1000' to get positive NMs but I thought maybe a little higher might make the numbers less negative.

I use a 5' metal pole as the cross mast on UHF and two 5' fiberglass poles connected together with a 1' aluminum rod for VHF. Right now I'm running an extended test on an 18' boom 22 element LPDA in place of the stacked 12 el LPDAs. Performance seems to be identical.
 

Attachments

·
Registered
Joined
·
3,655 Posts
I was wondering if any company sold a hardware package to do horizontal stacking.
What are you using for the cross bars? Is there a company that makes those mounts? (I guess that's my main question)
http://www.atechfabrication.com/products/x300-db_integrated_stacking_boom.htm

http://www.atechfabrication.com/products/dual_antenna_boom.htm

http://www.bobmerritt.com/dtv/dtv.htm

Making your desired weak signals stronger by stacking or raising your antennas is certainly a good idea, but you need to consider co-channel and adjacent channel interference.

If the co-channel interference is from the opposite direction, the F/B ratio of the antenna will help you.

ATSC Recommended Practice:
Receiver Performance Guidelines
Document A/74:2010, 7 April 2010
http://www.atsc.org/cms/standards/a_74-2010.pdf

5.4.1 Co-Channel Rejection
The receiver should meet or exceed the following thresholds for rejection of co-channel interference at the following desired signal levels (Table 5.1).

 

·
Registered
Joined
·
3,655 Posts
5.4.2 Adjacent Channel Rejection
The receiver should meet or exceed the thresholds given in Table 5.2 for rejection of first
adjacent-channel interference at the desired signal levels shown above the columns therein.

 

·
Registered
Joined
·
53 Posts
Discussion Starter #7
http://www.atechfabrication.com/products/x300-db_integrated_stacking_boom.htm

http://www.atechfabrication.com/products/dual_antenna_boom.htm

http://www.bobmerritt.com/dtv/dtv.htm

Making your desired weak signals stronger by stacking or raising your antennas is certainly a good idea, but you need to consider co-channel and adjacent channel interference.

If the co-channel interference is from the opposite direction, the F/B ratio of the antenna will help you.
Thanks for the heads up. Maybe I will give them a call when the time is right.

Well, the good news is that the Canadian channels are all North West, and the locally strong signals are all South East. All the local channels are all broadcast from a hill on the other side of town.
 

·
Registered
Joined
·
53 Posts
Discussion Starter #8
I'm not aware of anyone selling the stacking combiner. Most people just use a 2-way combiner and 2 equal lengths of coax. I found that has 0.5 to 1 dB loss. Considering you'll only get 2.5 dB max by stacking you don't really want to lose up to 1 dB in the combiner. That's why I built a 1/4 wave matching section combiner.

If the antennas you're stacking are 300 ohms and use a standard ferrite balun, you can pick up another 0.5 to 1 dB by making a coax balun instead.
Are there any good resources on balun making especially for the less mechanically inclined folks like me - especially if I get 2 of the Y10-7-13's? ;)

If I went with the DB8e/HDB8x, I think I saw someone take out the combiner in them and directly connected all 4 coax cables to a 4-to-1 splitter. I'm guessing that saves some loss.


I'm sure you would have to go to 1000' to get positive NMs but I thought maybe a little higher might make the numbers less negative.
I tried at both 50' and 100' and I'd only gain a little over a DB at best.
 

·
Registered
Joined
·
6,327 Posts
Are there any good resources on balun making especially for the less mechanically inclined folks like me - especially if I get 2 of the Y10-7-13's? ;)

If I went with the DB8e/HDB8x, I think I saw someone take out the combiner in them and directly connected all 4 coax cables to a 4-to-1 splitter. I'm guessing that saves some loss.

Here's what you need to make the coaxial balun to take the place of a standard 300:75 ohm balun:

(4) Amidon ferrite beads FB-61-6873
1' - Belden 9269 (93 ohm coax)
3' - Belden 9248 (RG-59 type coax with a copper braid that can be soldered)

I found the coax on Ebay and the beads are ordered directly from Amidon.

The 9269 is the loop and is 8.5" long plus the leads. Put the beads over the 9248 pushed up as far as possible. Attached are pictures of the balun. No beads shown.
 

Attachments

·
Registered
Joined
·
3,655 Posts
I was wondering how strong your local FM signals were, to see if they might cause interference to your TV reception. It looks like most of your strong FM signals are from the southern hemisphere of the compass diagram.
 

Attachments

1 - 10 of 10 Posts
Top