Canadian TV, Computing and Home Theatre Forums banner

1 - 20 of 65 Posts

·
Registered
Joined
·
228 Posts
Discussion Starter #1
Picked up all the materials today...

- 6 pieces of 3/8" aluminium rod 6' long
- 1 piece of 1" aluminium square tube 102" long
- lots of 1/2" copper tube, 90 deg bends for folded dipole driven element
- 300-75 ohm balun

Debating on design between the K7MEM designs or one of the optimized designs on Holl ands site. Here's my tvfool for digital only. I'm trying to get VHF 7 better than I currently do with a dipole. My SNR on WNGS (VHF 7) is running between 16.5 to 18.0 or so (from the Hauppauge tuner), a fair bit of correctable errors, and some uncorrectable errors depending on the day.

http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%3de07c64813e606b

I built a square loop with 1/2" copper which improved my SNR by about 1.0-1.5 Db... but I'm thinking since I only need one specific channel its better to build a yagi specifically for VHF 7 for the best gain.

I'll get pics along the way! :D BTW, this is going in my attic so it'll be pre-drilled downstairs and assembled up there...
 

·
Super Moderator
Joined
·
5,074 Posts
I'm surprised that you get WNGS at all. Though an SNR of 16.5dB is borderline. Obviously just about anything will have a better gain than a simple dipole.

Are you not interested in channel 9 Toronto or channel 11 Hamilton? Both are going digital after August 31. Though given your report, I'm sure you could pull those in with just about any UHF antenna.

BTW, I envy your TVFool report. I wish I was LOS to WUTV!
 

·
Registered
Joined
·
102 Posts
I'd say with a CH7 yagi you stand a good chance of getting WNGS, 15.8 is the NM before antenna gain, system losses, etc. With the right antenna and a preamp, it should be a stable channel.

However, you have so many other strong signals, you may have to trap everything else before the amp so you don't overload it (if you intend to use a preamp, I recommend it).

Ivan
 

·
Registered
Joined
·
638 Posts
Compared to my tvfool report it looks like a cake walk. Good luck.
 

·
Registered
Joined
·
1,713 Posts
Poutanan I hope it works out for you in the attic but VHF does not penetrate very well.You may need to be outside with WNGS being 2 edge for you.
 

·
Registered
Joined
·
7,360 Posts
Performance is purposely peaked at the high frequency end of the channel, as the accumulation of water droplets will cause the peak gain to shift downwards by up to 3 MHz.
Interesting, I assume thats for vhf-hi and fm. Do you have a reference chart for uhf, or do I apply like a water coating on the wire in 4nec2 ? If so, how much ?
 

·
OTA Forum Moderator
Joined
·
24,867 Posts
Are you above or below the Niagara Escarpment in Grimsby? If you're below then there might be some recepton issues with WNGS due to reports from others in the Niagara Peninsula.

For people who don't know the area, here's an amazing photo of the Escarpment through Grimsby taken from a light aircraft flying WSW with Lake Ontario to the lower right (north) and Buffalo to the left-rear (ESE) of the airplane:

http://upload.wikimedia.org/wikipedia/commons/d/d2/Niagara-Escarpment-Winter-IMG_0626.JPG
 

·
Registered
Joined
·
228 Posts
Discussion Starter #9
I'm surprised that you get WNGS at all. Though an SNR of 16.5dB is borderline. Obviously just about anything will have a better gain than a simple dipole.

Are you not interested in channel 9 Toronto or channel 11 Hamilton? Both are going digital after August 31. Though given your report, I'm sure you could pull those in with just about any UHF antenna.

BTW, I envy your TVFool report. I wish I was LOS to WUTV!
I'm already getting CTV (9) and CHCH (11) though they're actually UHF channels. WNGS is 67.1 which is VHF Channel 7...

Stampeder, I'm above the escarpment, actually my house is in that picture! If you look at the cut/access almost directly in the middle of the picture, follow that road to the 4-way stop and I'm in that area.

We're kinda lucky up here to have an almost direct LOS to the CN tower, across lake ontario, and there's not much in the way between my house and the towers in the US.

We're in OTA heaven here! I already get WNGS reliably enough to watch it, though some of my recordings have been digitized, so I know I'm right on the cusp. The yagi should give me a good lock, or at least that's the plan.

Pretty sure I'm going with the K7MEM calcs and a 1/2" copper tube folded dipole D.E., lets see how she works tomorrow. :)
 

·
Registered
Joined
·
228 Posts
Discussion Starter #10
I'd say with a CH7 yagi you stand a good chance of getting WNGS, 15.8 is the NM before antenna gain, system losses, etc. With the right antenna and a preamp, it should be a stable channel.

However, you have so many other strong signals, you may have to trap everything else before the amp so you don't overload it (if you intend to use a preamp, I recommend it).

Ivan
For what it's worth, this will be running into my CM-7777 pre-amps VHF input. The UHF has a 4-bay facing buffalo, and I've got another amp with an 8-bay facing toronto.

Both feeds run into separate tuners in my HTPC. One's a Hauppauge HVR-2250, the other is a HVR-1250.
 

·
Registered
Joined
·
228 Posts
Discussion Starter #12
What's my design frequency? VHF CH.7 is 174-180 MHz so I've been using 177, but is the drop off so rapid from a yagi that I should be designing it for 180 MHz instead? Not a massive difference in element lengths, but I want to get this right. :D

Thanks!
 

·
Registered
Joined
·
3,396 Posts
YU1AW also did a study plotting SWR and Gain degradation vs "water" thickness.
Although conduced at 2.4 GHz (Wi-Fi), the results are normalized wrt unity element radius,
which makes it easy to understand the impact in other frequency bands:
http://www.qsl.net/yu1aw/wet_ant.pdf

Bottom line: water shouldn't be much of a problem for VHF & UHF....but ice & snow buildup could.....
 

·
Registered
Joined
·
228 Posts
Discussion Starter #16
Success!!! I started working on the DIY yagi at around 6:00 tonight and had to stop from 8:30 until about 3:00 this morning for a bowling break. :D

I just climbed up in the attic and assembled the thing. It's a monster! 106" long and over 30" wide at the reflector. I'm currently running around 23.5-24.0 S/N Ratio on VHF CH.7 so I'm getting a massive improvement from the 16-18 or so I was getting before. Very pleased with the results!

I took a few pictures along the way and I'll get a few pictures of the entire farm/array up there tomorrow when I fine tune the positioning.

Thanks for all the help! :D
 

·
Super Moderator
Joined
·
5,074 Posts
You've found yourself in a very exclusive club: Canadians who can receive WNGS! ;)
 

·
OTA Forum Moderator
Joined
·
24,867 Posts
Well done, poutanen, and others in the Niagara Peninsula and the Niagara Frontier will definitely want to see your photos for sure!
 

·
Registered
Joined
·
1,713 Posts
Poutnan great job and provides some hope for others.Post your design choice and pics.My TV fool is about 5db weaker but still thinking of trying something.
 
1 - 20 of 65 Posts
Top