Otown's Antenna Hack - Canadian TV, Computing and Home Theatre Forums

 8Likes
Reply
LinkBack Thread Tools Search this Thread Display Modes

post #1 of 69 (permalink) Old 2016-08-03, 10:13 AM Thread Starter
Veteran
 
Join Date: Jul 2002
Location: Bowmanville
Posts: 4,039
Otown's Antenna Hack

Hi, please move this if its in the wrong section.

I live between Bowmanville and Newcastle a few hundred yards from the lake. Here is my TVFoll report
Quote:
As you can see theres about 65 degress between the Toronto and Buffalo Stations.

I started with a CM4228HD attached to a J mount at the top of my roof...about 20' above ground. I also installed a CM7777 pre amp with the FM trap in.

This worked well when aimed between TO and Buffalo but no channel 9. I then pointed it at TO and got channel 9 but no Buffalo stations.
So I exchanged the antenna for an ANT7287, pointed one side at buffalo and one at TO. Channel 9 wasn't watchable.

So on to my mod.

I bought a 3/8" 36" aluminum tube from Homedepot, cut it in half, inserted a wooden dowel so that each tube was separated by 1" of wood, drilled 2 holes, and mounted the tube on the top bowtie mount using longer screws. This worked well and I can now get channel 9 with mostly no problems. There is a little breakup first thing in the morning. I tried mounting the tube on the bowtie mount second from the top but this didn't work at all for channel 9.

So overall things worked out well. Channel 9 signal strength is mostly 70-75 but was 55-60 first thing. I scan 50 channels overall of which about 25 are solid. I also get channel 11 quite well with the hack...signal strength 65-75.

I have good site lines to TO and the Buffalo site line is blocked by trees....dosn't seem to affect reception.

I would like to see channel 9 a little stronger...any comments would be appreciated.

Pictures are attached.




otown47 is offline  
Sponsored Links
Advertisement
 
post #2 of 69 (permalink) Old 2016-08-03, 10:51 AM
Veteran
 
Join Date: Jun 2011
Location: 43° N, 81.2° W
Posts: 7,864
The wood will become a conductor when it gets wet. That will reduce signal strength for all channels. A piece of PVC pipe would be better.

The channel 9 dipole would likely work better if it was cut to the correct length. A folded dipole would provide a better impedance match and further improve the antenna efficiency. There is a technical discussion at Radio-Electronics.com here and here.

Another way to improve VHF gain is to mount some reflectors about 30"-36" long on the back of the antenna. One behind each bowtie should be enough. The length could be optimized for channel 9. There are others here that know much more about antenna optimization so I'll leave the measurements to them.
ExDilbert is online now  
post #3 of 69 (permalink) Old 2016-08-03, 02:46 PM
 
Join Date: Dec 2008
Location: Mississauga
Posts: 908
CHANNEL 9 centre frequency is 189 mhz. Formula to determine half wave dipole length is 468/189 = 2' 5-3/4" long, which would make each leg of the dipole 1' 2-3/4" long. I think your measurements for receiving are close enough to the ideal size.

OTA, CM4221HD, 3410 amp, 4 way split, HW-150 PVR.
FTA, Openbox S9, 33” dish, Avenger PLL LNBF. Stab 90HH.
Jorgek is offline  
 
post #4 of 69 (permalink) Old 2016-08-04, 07:15 AM Thread Starter
Veteran
 
Join Date: Jul 2002
Location: Bowmanville
Posts: 4,039
Thanks for the responses. I'll replace the wood dowel with plastic or PVC....good idea.

It looks like the ideal dipole length for channel 9 is 30"....I'm at 37". I can change this too. I was wondering how much improvement I can expect from the length reduction...any ideas?

thx
otown47 is offline  
post #5 of 69 (permalink) Old 2016-08-04, 12:43 PM
 
Join Date: Dec 2008
Location: Mississauga
Posts: 908
I bet you will not see any difference. Also this is the wrong time of year to try and compare antenna performance. Atmospheric conditions change rapidly and time of day is also a factor. Best time for me is when the weather gets and stay cooler or consistent which is usually late fall and early winter.

OTA, CM4221HD, 3410 amp, 4 way split, HW-150 PVR.
FTA, Openbox S9, 33” dish, Avenger PLL LNBF. Stab 90HH.
Jorgek is offline  
post #6 of 69 (permalink) Old 2016-08-04, 09:45 PM
DHC Supporter
 
Join Date: May 2010
Location: S.E. VA
Posts: 932
Thanks for the excellent photos, otown47.



ch9 5540/189 = 29.3 inches; Jorgek is correct

I would put a folded dipole (with balun) just above the Toronto section and combine it with it using a UVSJ.

The output of the UVSJ would go to the 7287 combiner.

The Buffalo section would go to the other input of the combiner.

The output of the 7287 combiner would go to the input of the preamp.

The way have it now in front of the Toronto section is not optimum. And the way you have it connected to the Toronto section is a poor match that can cause losses.

Also, the balun for the Toronto section is a PC board balun instead of a ferrite core balun. It will pass UHF signals well, but it will not pass VHF signals well if you connect the dipole directly to the UHF antenna.

You will need to experiment to find the best configuration for CH 9 without doing harm to your UHF signals.
Quote:
I also get channel 11 quite well with the hack...signal strength 65-75.
Which 11; what is its callsign?

If you can not measure it, you can not improve it.
Lord Kelvin, 1883

Last edited by rabbit73; 2016-08-05 at 06:28 AM.
rabbit73 is offline  
post #7 of 69 (permalink) Old 2016-08-04, 10:22 PM
Veteran
 
Join Date: Jan 2009
Posts: 4,538
There is no such Channel 11. He is referring to RF CH 15, CHCH from Hamilton, ON.

DB8E/VHF Yagi rotor FM Bandstop ap-8700 preamp 8way split LG lcd.
majortom is online now  
post #8 of 69 (permalink) Old 2016-08-04, 11:02 PM
DHC Supporter
 
Join Date: May 2010
Location: S.E. VA
Posts: 932
Ah, so; virtual channel 11.1.

Thank you.

If you can not measure it, you can not improve it.
Lord Kelvin, 1883
rabbit73 is offline  
post #9 of 69 (permalink) Old 2016-08-05, 06:30 AM
DHC Supporter
 
Join Date: May 2010
Location: S.E. VA
Posts: 932
It might be possible to add the Antennas Direct VHF Dipole Kit to the Toronto section. There have been three versions of the kit, and I think that the latest version has a UVSJ integrated with the dipole.
https://www.antennasdirect.com/store...tenna-Kit.html

https://www.antennasdirect.com/cmss_..._201402062.pdf

http://www.obviously-marvelous.com/2...-giveaway-110/

If ADTech stops by, he can tell you.

If you can not measure it, you can not improve it.
Lord Kelvin, 1883

Last edited by rabbit73; 2016-08-05 at 07:36 AM.
rabbit73 is offline  
post #10 of 69 (permalink) Old 2016-08-05, 08:37 AM
 
Join Date: Dec 2008
Location: Mississauga
Posts: 908
AD dipole kit does include an integral UVSJ. In the GTA it sells for approx $35.

OTA, CM4221HD, 3410 amp, 4 way split, HW-150 PVR.
FTA, Openbox S9, 33” dish, Avenger PLL LNBF. Stab 90HH.
Jorgek is offline  
post #11 of 69 (permalink) Old 2016-08-05, 09:13 AM
Veteran
 
Join Date: Jun 2011
Location: 43° N, 81.2° W
Posts: 7,864
Using a UVSJ is a much better idea. They are worth about $5. Using the AD dipole retrofit is a nice solution but it's overpriced at $35.
ExDilbert is online now  
post #12 of 69 (permalink) Old 2016-08-05, 02:11 PM
 
Join Date: Oct 2011
Location: Ajax, ON (Emperor & Pickering Beach)
Posts: 99
otown, do you get 51 ok?
Maury Markowitz is offline  
post #13 of 69 (permalink) Old 2016-08-05, 02:28 PM Thread Starter
Veteran
 
Join Date: Jul 2002
Location: Bowmanville
Posts: 4,039
Yes the 6 X 51 channels are strong.

The Antennas Direct VHF Dipole Kit VHF-1 is available in the US for $20...I haven't found it in Canada. Is that the same as a "AD dipole kit"?

This weekend I plan to replace the wood dowel with plastic, trim the dipole to 30" and try the other kind of balun.

thx
otown47 is offline  
post #14 of 69 (permalink) Old 2016-08-05, 03:17 PM
DHC Supporter
 
Join Date: May 2010
Location: S.E. VA
Posts: 932
Yes, the same.

If you still don't get what you want with your modified dipole connected to the Toronto UHF antenna, you can connect it as you would the VHF KIT.

The dipole is 75 ohms, so it can connect directly to a UVSJ, but you have to waterproof the end of the coax that connects to the dipole. Do not use a regular 4:1 300 ohm to 75 ohm matching transformer balun; a special 75 ohm to 75 ohm 1:1 balun is required, but you can make a test without it.

If your dipole is a folded dipole, then the 4:1 balun is suitable.






If you can not measure it, you can not improve it.
Lord Kelvin, 1883

Last edited by rabbit73; 2016-08-05 at 08:40 PM.
rabbit73 is offline  
post #15 of 69 (permalink) Old 2016-08-05, 08:42 PM
 
Join Date: Dec 2008
Location: Mississauga
Posts: 908
Quote:
Originally Posted by otown47 View Post
Yes the 6 X 51 channels are strong.

The Antennas Direct VHF Dipole Kit VHF-1 is available in the US for $20...I haven't found it in Canada. Is that the same as a "AD dipole kit"?

thx
Antennas Direct and AD are the same.

Available at Save and Replay.

OTA, CM4221HD, 3410 amp, 4 way split, HW-150 PVR.
FTA, Openbox S9, 33” dish, Avenger PLL LNBF. Stab 90HH.
Jorgek is offline  
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Canadian TV, Computing and Home Theatre Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in













Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome