: ON - Ottawa, Vanier, Gloucester, Orleans - OTA
2011-11-14, 10:59 AM
The only way to ensure reliable reception of Global (RF 6) is with a VHF antenna. Relying on a pre-amp to boost the signal of a VHF-LO station from the back of a UHF antenna is asking for problems. Also, those with the most problems with Global are in one of the two 10dB nulls and the Effective ERP towards streetwriter is only down about 3dB from max. Adding a VHF antenna will also solve any potential problems with CJOH (RF 13) and CBOFT (RF 9).
As for TVO and CBOT (RF 24 and 25), the CM-4221HD has a front/back ratio of about 22dB, which will put them down around the same level as CFMT and CJMT for him. Even CFGS (the weakest station from CF) should be receivable on the backside without a pre-amp.
2011-11-14, 11:05 AM
streetwriter, that tree could indeed be the problem. Not sure why it worked before but not now (could be weather related, but that is usually more of an issue for distant stations).
When tidying up the cables, could you have pinched a cable? Also, make sure the compression connections are secure and none of them have strands of braid shorting against the centre conductor (testing with an ohm meter and the cable disconnected at both ends, it should be open).
2011-11-14, 12:31 PM
streetwriter, on top of the very good advice roger1818 has given you so far, I will add paranoid & upsetting advice based on my experience from Global. Before you follow this, you should be trying out a real VHF antenna: even if you find something based on the advice below, increasing the gain on the channel you want can make the interference smaller in comparison and render it irrelevant.
Any computing device and AV equipment could affect your channel 6 reception. In my case, turning OFF my subwoofer helped reception a LOT. In OTAJuncqui's case, changing the proximity of the coax to the power supply of a PC made Global a LOT better as well.
Even though I might be trying EMI/RFI plug in line filters going forward as my power bar might not be doing a good enough of a job, I am still upset that this is even a problem.
2011-11-14, 01:35 PM
I've been thinking about the antenna mods Maple Leaf referred to and the comment:
You may find that reception will improve if you lower the antenna on the mast but keep it where it is for now and try adjusting the direction first.
Why would lowering the antenna improve reception? I thought I should be striving to get more, not less, height.
Have a look at this page to understand the concept of 'hot spots' caused by ground (and other) reflections http://www.hdtvprimer.com/ANTENNAS/siting.html.
Contrary to expectation, signal strength can be stronger a few feet lower down than where an antenna is currently mounted. Raising the antenna a little can likewise increase the signal strength by more than might be expected by simply the added height above the ground.
2011-11-14, 04:34 PM
Thanks, I'll read that tonight. In the meantime, it's possible I got better reception before because my antenna (without a preamp) was on a j-pole attached to my chimney, meaning it was lower (and possibly pointed up or down a bit) toward HC. As a result, I might have been missing that distant tree, if it's a factor. When I put the 10-ft mast on my chimney, I definitely got the antenna higher and with a clear LOS at least over my neighbour's rooftop.
I can also test my cable connections again. Generally, I make a point of carefully folding back the wire braid for good ground contact before slipping on the compression connector, but maybe I missed something.
2011-11-14, 09:09 PM
OK, I've done some thinking about this. I don't think the issue is cable or connectors because I am getting lots of channels quite clearly.
Here's what I am getting now, downstairs on the decroted projection HDTV with an iView converter:
4-1 CBC English
6-1 Global HD
6-2 Global SD
9-1 CBC French
60-1 Omni1 (with some bad pixellation)
65-1 CityTV (badly pixellated and unwatchable)
Upstairs, on the newer HD LCD with a built-in tuner, I am getting the same except no Global, Omni1, or CityTV at all.
Eliminating the splitter and bypassing the preamp produced no change in results.
After reading the article suggested earlier, I think my antenna's location or height is perhaps the likely source of my problem. (I'm pointing at HC and picking up most of my channels from CF off the back of my antenna.) That distant tree I mentioned is perhaps not so much an issue, but there's a big-ass building very close to the direction I am pointing. I looked at TV Fool again and, using Firefox, plotted the green line from HC to my antenna. It just brushes past the corner of that building before heading south down Bank St. So, a combination of aiming and adjusting the antenna height might be in order. I am limited in what I can do moving the antenna horizontally without going to some other method of mounting it. Plus, moving it one way would likely put me behind that building, while going the other could put me behind other trees that are much closer.
Is there something else I might have missed? Would pointing at CF and trying to pick up City and Omni1 from the back of the antenna make a difference?
2011-11-14, 11:34 PM
Looking at your TVFool, both towers are about the same distance away so turning it around probably won't make a difference. One possibility is that your LG tuner may not be that sensitive. Have you tried running the coax to the LG tv alone? Or just switching cables? Since you're getting it on one tv with the same source for signal it doesn't sound like the connections are a problem.
If you have a set of rabbit ears - try plugging that into the LG (by itself) and rescanning for Global. Can you manually enter a channel on the LG? Remember the 4221 is not rated for VHF, it is picking up the station on signal strength alone. If the rabbit ears work, just attach a combiner (splitter in reverse) and use both antennas on the LG.
The mods I've done on on my 4221 have improved the VHF reception but I am close to Camp Fortune, and I have a very clear LOS (line of sight). Be advised that these mods will slightly reduce the UHF reception of the antenna. Unfortunately, this isn't the time of year to outside playing with an antenna.
2011-11-15, 09:40 AM
streetwriter, I agree with Maple Leaf and turning your antenna around won't help you. Other than Global (which is a different issue), your problem stations are all towards HC so you want to point your antenna towards it for maximum gain. Given the choice, you are likely better off having the signal travel through trees than a building, so if you can move your antenna over a bit, that may help. If you can't get LOS due to obstructions, trying to catch a reflection, by aiming in a different direction may also work, though this is a trial and error process and prone to sudden loss of reception if the environment around you changes.
While you may be right about the cables and connections, don't forget that since DTV is all or nothing the fact that you have a good picture on other channels only means you have a good enough signal to get a signal lock. Cable and connector problems will often degrade the signal without blocking it entirely.
2011-11-15, 05:31 PM
It sounds like you are relying on reflections and/or multipath to receive your signal. Per post #1288 (http://www.digitalhome.ca/forum/showpost.php?p=1346609&postcount=1288) and #1289 in this thread (http://www.digitalhome.ca/forum/showpost.php?p=1346741&postcount=1289), I face very similar issues.
First, per advice from another forum member, I suggest using the TVFool "MAPS" application (open with Internet Explorer, it doesn't work with Chrome). Click on the "Show lines pointing to each transmitter" box (Chrome doesn't show this) and trace your routes to HC. Look to see if there are high buildings in the distance that may be blocking your LOS.
For me, CF comes in clearly (and the CM4221 and CM4228 both rock at receiving Global in downtown Ottawa), but LOS is obstructed by a highrise building roughly 5 blocks away. I get everything except CHCH (11) and CJOH (13) now, including a very very strong signal to Global on my CM4228HD. If I adjust my antenna just a fraction to the left, I lose CityTV and OMNI1, and then get a powerful signal for CJOH. I have yet to find a position that accomodates all HC channels in one angle.
As advice from someone who still has outstanding problems, the following link on multipath may help you:
I have some evidence that my problem may be multipath and that I am relying on reflections to pick up the signal. In my antenna experimentation (with the CM4221, CM4228, HBU22, and SS-2000), I found the HBU22 to be highly directional and helpful in receiving certain stations. One strategy which I'll try in the spring may be to use two or more antennas and multiplex them together with Join-Tennas. They have been discontinued but CM appears to have them in their online store (http://www.channelmasterstore.com/SearchResults.asp?Search=join-tenna). I may add a second and third antenna to see if I can mux 11 & 13 into one.
2011-11-15, 05:51 PM
millergd, FYI RF channel 11 is no longer being used in Ottawa (CHCH is now on RF 22, but remapped to virtual channel 11 by your TV). As a result all VHF stations are transmitted from CF so a Join-Tenna likely won't be of much help.
2011-11-16, 03:41 PM
Does any one know if TFO (channel 39 Hawksburry) is broadcasting in digital (or only analog)? Thanks.
2011-11-16, 03:42 PM
TFO broadcasts OTA only in analog.
2011-11-16, 07:53 PM
Is it just me or has CHCH been offline most of the day?
2011-11-16, 08:55 PM
CHCH works for me just fine in Alta Vista, except there's not much worth watching on it. If you're getting CityTV, I'll trade ya before Fringe on Friday.
Seriously, I think my problem has to do mainly with that big-ass Bell building at the corner of Bank and Randall. It's very close to my LOS to the HC tower. I plotted the green line from HC to the antenna on my chimney and the line just skirts the edge of that building. Plus, it has a lot of towers on its roof that could well be interfering with my reception.
I had City, nice and clear, once. I think I need to fiddle with my antenna placement. Here's hoping for decent weekend weather.
2011-11-16, 09:04 PM
CHCH was off air when I tried a few hrs ago.
2011-11-16, 10:39 PM
I hope CHCH comes back up in 720p or 1080i and a more powerful transmitter.
2011-11-17, 09:57 AM
^^^720p or 1080i could happen as that is just a business decision but a more powerful transmitter would require CRTC and IC approval.
2011-11-17, 06:14 PM
CHCH was fine later in the evening yesterday at least when I was channel surfing but I see they are offline again today.
The only one I normally have any problems with is Global, being south east of the city the signal is very week here. my vip302sr just barely picks it up (had it up on the roof for a while but the signal seems to be better for Global with it on the back deck)
My UHF antenna is pointed south right now so I am getting PBS (WCFE and WNPI) as well as Fox and CBS but oddly today for some reason CBC and TVO are not coming in off the back of the antenna when everything else local is, very strange that two of the stronger local UHF channels are not coming in so not sure if the problem with CHCH for me today isn't something with my setup.
2011-11-19, 08:49 PM
Today was a fantastic day and I took advantage of it to climb on the roof, pull down the mast, do the CM-4221 hacks/mods (except for shortening the reflector), replace the coax from the antenna to the preamp, which I discovered didn't have the best connection, lower the antenna a bit, and reinstall everything. As a result, I have CityTV again and Global on one TV. CHRO/CTV2 is gone, but both Omni channels are clear, despite being so geographically challenged. I have that big-ass building and some trees between the antenna and HC, giving me a narrow aperture to aim through, and a whole bunch of trees between me and CF. But, anyway, as I say, improvement. Oh, and I have CHCH still.
A couple of tips about the antenna mod. First, I have a wide crimper for duct work, which I found made quick work of straightening the slats behind the balun. I'm sure lineman pliers would do almost as well, but if you have a crimper, use it. Second, I drilled new holes at the bottom of the balun slats, below where the coax connects. I realised after connecting and routing the coax it would be easier if I'd drilled new holes above the balun.
Thanks, all, for the help. Learned a lot. I'm sure there's more tinkering ahead, but I am that much more informed now.