AFAIK, FMFool has not been updated to use Industry Canada data, so its results are not very good for Canadian stations, so I wouldn't rely on it.Sorry to hear that. I don't know much about Canada, except what I learned when my wife and I spent our honeymoon in Montreal to see Expo '67.

I notice that GeoStar gives his tvfool report on his homepage:
http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%3d8d17d79aa5c6e9

Based on that location, I ran an FM fool report:
http://i496.photobucket.com/albums/rr328/rabbit73_photos/GeoStarfmfool.jpg

If the report is correct, it looks like CKKL on 93.9 and CIMFFM on 94.9 would cause the most trouble for CH6, all of which are coming from 307 degrees. The Join-Tenna might be enough.

GeoStar:

I must be missing something. Maybe I should read through all of your posts.

Am I looking at the right CH 6? GTN CIII-TV analog is -25.9 dBm, and CIII-DT is -38.4 dBm.

With so many strong TV and FM signals, why do you need a preamp as shown is your post #1250 (http://www.digitalhome.ca/forum/showpost.php?p=1254539&postcount=1250)?

After looking at the preamp chart by holl_ands, it seems that overload is possible, which is what roger1818 said to you after your first post.

agree, he shows a kitztech preamp, plus a distro amp in the diagram.
could see maybe 1 or the other but not both if he was trying to grab some US stations on tropo days. But if that was the case he'd be better off with a rotor, cause the US stations look to be in a different direction than the Canadian stations and the CH6 he's trying to " add".
Sounds to me like he has an issue with channel 6 now, or he wouldn't have brought up that he wants to do something with CH 6. But since that's pretty strong in his TVfool, and in the same direction as the adjacent FM stations. He probably just needs to tone down the FM band to clean up Ch 6 enough to pull it in reliably. Go back to square one with no pre-amp or distro and evaluate CH 6 from there maybe?

Thanks for the confirmation; I was beginning to doubt my analysis of his situation.

would think he'd be able to simplify it somewhat too using a diplexor. inside the house just diplex, the CH6 in to a UVSJ from a pair of rabbit ears.
Rabbit ears will ensure not too much VHF (FM band) signal gets in to the system. But then again, I'm not the one having to deal with CH 6 adjacent to FM like he is. So maybe he's already tried the simple?


/|\UHF Antenna /|\ VHF Antenna
| (outside) | (rabbit ears, inside the house)
| |
| |
| |
|------|UVSJ|----------|
|
|

to TV

GeoStar:

Using a preamp to receive the weak signals is fun, but the preamp might not like your very strong signals. Your tuner selects one signal at a time, but the preamp and the tuner input are subjected to all signals at once. That is why you need to attenuate the strong unwanted signals with a passive device (not powered) before amplification. The dynamic range of the preamp and tuner combo has an upper and lower limit for signal strength.

In your case, as you mentioned in an older post, you had enough preamplification to receive weak PBS stations from the US, but it was too much amplification when you aimed your antenna at your strong local stations. And roger told you that The problem is over amplification... (http://www.digitalhome.ca/forum/showpost.php?p=978107&postcount=1326)

You also asked if cutting the power (http://www.digitalhome.ca/forum/showpost.php?p=974414&postcount=1307) to the preamp would reduce the gain for the strong local signals, and you were told that cutting the power would block all signals.

One way that I can think of is to use separate antennas, one amplified and the other not amplified as roger and majortom suggested. Another way would be to have two relays connected in the coax to bypass the preamp and make a direct unamplified connection with a second run of coax. One of the relays would need to be between the antenna and the preamp, the other after the power inserter. And another way would be to have an attenuator between the antenna and the preamp, with a relay to short out the attenuator when you need more gain for weak signals. You wouldn't need a second run of coax, but you would need a separate low voltage DC line to operate the relay at the antenna.

There is a situation when none of the above solutions will work. That is when you have a very strong signal and a very weak signal (on different channels) coming from the same direction. With the preamp out, you can receive the strong station, but not the weak one. With the preamp in, you can't receive either because the preamp is overloaded (the difference between the strongest station and the weakest exceeds the dynamic range of the system). The solution is, as roger said, to "notch out" the strong signal. If the channels aren't too close together in frequency, you can use the bandstop section of a Join-Tenna (all-channel input to tv set output). If they are close together, you will need a custom bandstop filter to attenuate the strong signal.

If the report is correct, it looks like CKKL on 93.9 and CIMFFM on 94.9 would cause the most trouble for CH6, all of which are coming from 307 degrees. The Join-Tenna might be enough.

That FMFool report is missing all of the problem stations for Channel 6 here in Ottawa. tvlurker (http://www.digitalhome.ca/forum/member.php?u=10700) published a list of all FM stations here in Ottawa and summarized the likely problem ones here (http://www.digitalhome.ca/forum/showpost.php?p=1252781&postcount=12).

Hi,
How do I set up my two antenna's with the 7777 preamp?
I have one antenna aiming north at the CN tower and one facing south-east (Grand Island).
My preamp has 2 inputs and 1 output. Also it has a few switches, one for FM trap and the other for VHF separate/combined. I have the switches at the default settings but I am only getting the feeds from the USA and not Toronto.

robman50, the 7777 will combine a VHF antenna and a UHF antenna. Is this what you have ? If not, then you will need something else in front of your 7777 to combine them before getting in the preamp. A splitter/combiner, for example.

I have an old UHF/VHF/FM yagi that is facing north and a new CM4228HD aiming south east.

ok so?
old yagi (uhf/vhf/fm) ->combiner ->preamp?
______________________/\
new cm4228hd (uhf)-----|

robman, replace 'combiner' with 'UVSJ', and u should be OK.
That's basically what I do here except in addition I place my homemade
VHF Hi pass filter between the UVSJ output and the preamp input, to kill
the FM Band entirely. I'm not interested in anything below VHF CH 7.

I just looked at the 7777 and the yagi is on 'VHF seperate input' and the 4228hd is on 'UHF or combined' but the switch is set to Combined.
Could that cause the problem? maybe I just have to change the switch?

Keep setting as combined input since it looks like you want UHF channels from both antennas. Combine both antennas using a splitter combiner if you wish to retain VHF channels, or uvsj if you wish to filter out VHF entirely like majortom. Then input the combiner output into the UHF(combined) input on the 7777. Leave the 7777 VHF(separates) input unused.
EDIT: you'd actually want a uvsj after the combiner output to kill off all VHF. Or set the cm7777 as Separates...

Yep I didn't notice u have the cm 7777 with the input switch. Ya have to open it up to flop the switch I think. I don't have one myself but the installation notes sheet should let you know which way it is set at the factory by default. Depends on what ur trying to do as to which way to set it.

I would like to use both the VHF and UHF bands just incase after the CRTC deadline of the analog to digital switch that they may put some digital stations on the VHF band.
Also what is a UVSJ? I don't think I've heard that one before.

roger1818:
That FMFool report is missing all of the problem stations for Channel 6 here in Ottawa. tvlurker published a list of all FM stations here in Ottawa and summarized the likely problem ones here.Thanks for the link to the FM station list.The lowest high power stations are the CBC at 90.7 and 91.5 MHz with 84 kW each.That's even worse than I thought!

robman50, then use a normal 2:1 splitter to join the antennas before the cm7777. You will keep all VHF and UHF bands this way. A common splitter is also called a splitter combiner. It can be used one way to split or the reverse way to combine signals like what you'd do here.
EDIT 2: I edited my post #1294 for better clarity

If you set the input switch to "Combined" on a 7777, you will get NOTHING from the VHF port since the switch physically disconnects it...

If you combine both antennas using a 2:1 combiner, and put the output of it on the Combined 7777 input, Of course you're not getting anything from the VHF input of the 7777; you're not using it in this case.

And the combined cm7777 will amplify the VHF band that the antennas pick up.