: ON - Ottawa, Vanier, Gloucester, Orleans - OTA
2010-06-25, 04:28 PM
That reminds me...for some reason if I point my antenna right at camp fortune I get lots of MB on CBC (unwatchable really)...when I point it 180 degrees the other way with the signal coming in the back it seems just right. I havn't tried it without the preamp though. I am assuming the bowtie side is the "front" of the antenna and the jail bars are a back reflector(?).
As flavoie mentioned, the strong signals being amplified by your CM preamp may be overloading your tuner, but I suspect it may in fact be the CM preamp itself that is being overloaded first. I've probably been looking in all the wrong places here (i.e., search terms...), but I haven't seen much mention of this.
There is a spreadsheet posted online (not sure if rules permit linking) by holl_ands that analyses preamp overload characteristics, and some are not suitable for handling very (very) strong signals (e.g., CM 7777).
This is something I've been trying to wrap my head around lately, and have been planning to put together a description of my situation for input by the gurus here.
So, aiming away from Camp Fortune may be required when you have the preamp inline.
2010-06-25, 10:19 PM
So, aiming away from Camp Fortune may be required when you have the preamp inline.
Especially if you have a high gain antenna (like a CM4228), a high gain pre-amp (like a CM7777) and are reasonably close to Camp Fortune.
2010-06-26, 12:29 AM
According to TVfool I am 12.2 miles from the CF tower. I am near the highest point in the beacon hill area as well with a roof mounted cm4228.
The first time I noticed the overload was actually with CITY TV when I point the antenna toward watertown. If the preamp isn't helping with the weaker digital signals then I don't need it.
I'll try a few more tests. I'm not getting watertown tonight like I did last night.
2010-06-26, 10:51 AM
The preamp will help you when you split the signal for multiple tuners, and should help getting WNYF more reliably (hopefully their tower will transmit within the end of this summer). How is WNYF showing in your tvfool ? You can post the link here, your location remains anonymous.
2010-06-26, 11:39 AM
Here are my tv fool results
2010-06-26, 02:07 PM
I have re-attached the preamp with splitter and two tuners and I don't seem to get any overload. The signal performance seems to be the same as with no splitter/no preamp.
I have noticed that i need to actually point my antenna toward camp fortune in order to get sunTV with no MB. CBC french and english don't have this problem.
I think I like the two-tuner config (although it was a heck of a time getting all this to work with windows media center). I can now watch and record two programs at once...and stream the recordings to any pc on my home network.
On another note I have noticed some (blank?) channels coming up on the mountain lake pbs ie 57.6, etc. There doesn't seem to be any broadcast or station ID...just a channel detection. Whats that about?
2010-06-26, 02:33 PM
First...wow, thanks to all for all the info and questions, feeling a little sheepish because I thought we were the only ones in Ottawa watching TV without cable or satellite...just a indoor amplifier antenna. We have been thinking about an antenna for the roof, laziness on our side, the getting up to adjust the antenna (not for every channel -but often enough) is sometimes a pain...not being permanent coach potatoes is the up side, but I can use the stairs at work to compensate :-)
...we have an old, + or - 3 foot, parabolic satelite dish in the shed...I plan on checking the AR&D forum link above to see if we can re-purpose it, but may be way off...if anyone is aware of best link please feel free to point us in the right direction. Presently we get almost all the channels identified in the "read this first" listings except the CBS and PBS...thanks again.
2010-06-26, 03:10 PM
Hi, regarding satellite dishes, there is unfortunately no way that one of those will do for OTA, even at 3 feet diameter or so. It is best to build your own DIY antenna. Please read through all of the links at the bottom right of this post.--->
2010-06-26, 04:13 PM
Thanks...got that about the dish on further investigation into the associated forums...have downloaded the antenna pdf and went to the tvfool site to figure what we should and could get...may even consider one of the DIY antennas given all the info...will keep an eye on recommendations here and will post if we follow thru. Thanks again, fairiequeenArch
2010-06-26, 10:19 PM
According to your tvfool results, you have very good chances of getting WNYF when it gets on the air. I find this by clicking "Pending applications included". Did you give WWNY - Watertown (7.1) a try ? I wonder if you picked it up when you were seeing WWTI. The 4228 is not the best for VHF, but it's still got decent gain for VHF-HI channels, and it is showing -6dB in your tvfool. I also have a windows media center setup with a splitter connecting 2 ATSC tuners, except right now it only has an indoor antenna connected to it.
2010-06-27, 12:37 AM
I have not EVER seen wwny even on nights when wwti comes in quite strong (60-80% tonight for example). I am going to try to raise my antenna another 5ft and maybe get a rotator for the antenna as well as the trips to the roof are getting old.
I am hoping WNYF will come in no trouble...as I said before WNPI is always on with plenty of signal and WCFE is no trouble on any night so long as I point the antenna in that direction. I get wwti about 40% of the time so far...when I do it works really well.
I have been using Peter Near's hack to get WMC to work for the digital stations, but I am having trouble getting guide data for the USA stations (tried his USGuide hack, but it doesn't see the mountain lake pbs). Any ideas?
2010-06-27, 02:11 AM
I am hoping WNYF will come in no trouble...as I said before WNPI is always on with plenty of signal and WCFE is no trouble on any night so long as I point the antenna in that direction. I get wwti about 40% of the time so far.
Mike, I think you are in a great position to get WNYF-LP (18/28.1; FOX-SD/CBS-HD), WNPI (23/18.x; PBSx3), WCFE (38/57.x; PBSx3) as well as all the locals. But WPBS (41/16.x; PBSx3; -20.3 dB Noise Margin), WWTI (21/50.x; -21.8 dB NM), and WWNY (7/7.x; CBS-HD/FOX-SD; -6.3 dB NM but VHF-HI) will be big challenges to get more than intermittently, unfortunately. Recent weather conditions have allowed much better signal propagation than normal. (I've been picking up channel 35/28.1 FOX from Watertown occasionally over the past few weeks -- definitely abnormal.)
Back to that CM-7777 preamp: Please check out this chart (hope this link works -- if not, see the first post in the Signal Amplifiers thread):
The CM-7777 maximum input for two strong VHF channels is -29.8 dBm, -35.8 for UHF. (Reduce by 3.6 dB if 3 strong signals, 5 dB for 4, 7 dB for 6, etc.) Your tvfool report shows channel 4, 9, 13, and 6 all above the VHF levels, and several of the UHF channels also coming in hot. Once the preamp is driven into overload, results will become unreliable and unpredictable.
Here are some suggestions, and I hope the forum experts will chime in with feedback and criticisms:
a) Depending on the cable length from your antenna to your splitter/tuners, consider eliminating the CM-7777 completely.
b) If you are mostly interested right now in just the digital channels, I'd suggest that you get a UVSJ and a 75 ohm termination. Aim the 4228 between South Colton (151 degrees) and Plattsburg (122 degrees). Connect the 4228 to the UHF port on the UVSJ, and the 75 ohm termination to the VHF port, and connect the joiner output to the CM-7777 input. This should help attenuate the hot VHF signals from CF.
c) If you also really want the analog VHF channels, get a low-gain (simple dipole?) VHF antenna, and run a separate cable for it down to where you have your splitter/tuners. Connect this to the VHF input of another UVSJ, the tv-side feed from the CM-7777's power supply to the UHF input, and this joiner output to your splitter/tuner input.
A long post, but I'm really hoping to get some feedback/discussion on these suggestions.
2010-06-28, 04:43 PM
About option b) Since Mike has a CM-7777, instead of the UVSJ to cut off the strong VHF, I assume he could also just reconfigure the CM7777 for "separate" VHF and UHF inputs instead of "combined", and keep the current cable connection to the "UHF/Combined" and this would do the same job ? Just plug the 75ohm termination to the VHF input of the CM-7777 ?
2010-06-28, 04:47 PM
flavoie: That is certainly an option!
2010-06-28, 07:34 PM
another idea for b)
channel 4, VHF analog, is the strongest channel by far coming in from CF in your tvfool.
Use an HLSJ to filter it out along with the VHF-LO channels and keep the CM7777 in combined input.
2010-06-28, 08:21 PM
To be honest though it is tough to make recommendations right now as everything will be changing in a little over a year and we don't know for sure what will be happening then.Thanks for this feedback
2010-06-29, 01:18 AM
A couple of follow-up comments on my earlier suggestions for Mike:
Yes, the CM-7777 does have a separate UHF input available, and I suggest that you use this. However, I think that your situation calls for very aggressive attenuation of some of the VHF signals, and I'm not sure what the effectiveness of the CM-7777's internal bandpass (or hi-pass?) filter is on this input. Posts in other threads have indicated that a good UVSJ can provide a very effective filter for VHF signals, so this is what I've suggested.
Also, although Ch 4's power level immediately sticks out (-14.4 dBm), based on charts I've seen for its predecessor 4228, the 4228HD's gain on VHF-lo may be quite poor (to negative). However, its gain on channels 9, 11, and 13 could be 4-6 dBd, depending on antenna orientation, so all of these signals (4, 9, 11, 13) must be considered for CM-7777 overload.
Golly, this gets complicated :eek:
2010-06-29, 01:20 AM
I think that your situation calls for very aggressive attenuation of some of the VHF signals, and I'm not sure what the effectiveness of the CM-7777's internal bandpass (or hi-pass?) filter is on this input. Posts in other threads have indicated that a good UVSJ can provide a very effective filter for VHF signalsYep, there are some great examples of that in here:
Splitters, Attenuators, Filters, Diplexers, Other Signal Gear (https://www.digitalhome.ca/forum/showthread.php?t=42428)
2010-06-29, 10:48 AM
I'm not sure what the effectiveness of the CM-7777's internal bandpass (or hi-pass?) filter is on this input. Posts in other threads have indicated that a good UVSJ can provide a very effective filter for VHF signals, so this is what I've suggested.
I haven't seen the specs, but I would expect the CM7777 would be as if not more effective at filtering out VHF than the UVSJ as I believe it has filters on both the input and output stages (one of the nice things about the CM7777 is it has separate amplifiers for VHF and UHF to eliminate harmonic distortions of VHF causing interference on UHF so it needs filters on the input to ensure it is only amplifying signals from the desired band and filters on the output to effectively combine the bands together).
Having said that, if you are only wanting to amplify UHF, you would be better off using a dedicated UHF amp that will either block or bypass VHF (depending on whether you are using a separate VHF antenna or not). If you do decide to stick with the CM7777, be sure and put a 75 ohm terminator cap on the VHF input to ensure no signal leaks in.
2010-06-29, 11:02 AM
Connect the 4228 to the UHF port on the UVSJ, and the 75 ohm termination to the VHF port, and connect the joiner output to the CM-7777 input.
If you do this, I higly reccomend connecting the UVSJ the other way around with the antenna connected to the combined port and the UHF port to the CM7777 to ensure no signal leaks from the VHF port to the amp. I would still terminate the VHF port though.
run a separate cable for it down to where you have your splitter/tuners. Connect this to the VHF input of another UVSJ, the tv-side feed from the CM-7777's power supply to the UHF input, and this joiner output to your splitter/tuner input.
To avoid the need for a second downlead, you can get a band combiner (such as the EU385-CF) that has power pass on the UHF port, allowing you to put it between your pre-amp and power injector.