Everyone should read the "TVFool Signal Analysis FAQ" (http://www.tvfool.com/index.php?option=com_content&task=view&id=57#how_to_read) as it gives a good description of how to interpret your TVFool results. I have read it many times now... and understand it a little more each time.

Quoting from the FAQ: "If you take the initial NM value for a given channel, add your antenna gain, subtract all the other system losses, and still end up with a value above 0, then you should be able to detect that channel."
and
"Antenna gain is the only quantity that should ever be ADDed to the NM value. "

Quoting from the FAQ: "If you take the initial NM value for a given channel, add your antenna gain, subtract all the other system losses, and still end up with a value above 0, then you should be able to detect that channel."
and
"Antenna gain is the only quantity that should ever be ADDed to the NM value. "

Exactly. Considering deep fringe antennas only provide about 10 to 15 dB of gain, I don't see how it is possible to reliably receive a signal with a NM of -39.5db.

I will also point out that there is a difference between detecting a channel and being able to receive it reliably.

Some might find this interesting... I guess it is worth a try if you are in a similar situation. I was able to receive WNPI (PBS-ch23) without any amplification, when I added a CM-7777 I was able to pick up WNYF from the same tower and WCFE -- but only when I added two splitters into the path to my TV. One splitter got me WNYF... the second allowed me to get WCFE, I have been getting both solidly through snowstorms all day long.

So the CM-7777 was able to amplify the signal enough to get it down to the TV but was probably overloading the TV tuner becase of my proximitiy to the HC/CF towers.

I plan on having a 4:1 splitter in the path to my TV for my two-tuner HDHomerun (once it come back from RMA) -- will have to get a terminator for the empty output.

I was able to receive WNPI (PBS-ch23) without any amplification, when I added a CM-7777 I was able to pick up WNYF from the same tower and WCFE -- but only when I added two splitters into the path to my TV.

Adding splitters or attenuators will sometimes help limit the signal strength of the strong locals to allow you to receive weak distant stations. If you know the specific channels causing overloading, a better approach is to notch out those specific channels. You will still be able to receive them as notches will only attenuate the signal and not block it completely. The nice thing about this approach is it balances the signal strengths nicely making things easier for your tuner. Tuned single channel notches are expensive however.

I am LOS to both towers 15.9km to CF and 10.9 to HC. I have 13 signals with greater strength than -30dBm so be a lot of notch filters. I might try a kitztech 's adjustable gain preamplifier (<1db NF) to fine-tune the amount of gain I am adding to the system.

Keep in mind there is a balance to be struck when using the Kitztech in that way. If you lower the gain, you increase the noise.

I have used this technique with success at my home.

you should not pick a KitzTech preamp for its adjustable gain feature. The minute you turn down the dial, you are increasing the noise figure it introduces - thus worsening the SNR. It is recommended to keep it with the dial at full blast. So only consider the Kitz stated noise figure vs your current preamp noise figure and that's what you would gain. If gain is similar, you'd likely still need attenuation before your TV tuner like you currently are doing.

EDIT: HWP you beat me by a minute !

I'm a Kitztech fan so I jump on any messages mentioning it.

Agreed with flavoie. When I spoke with the Kitztech owner, he specifically encouraged me to avoid using the adjustable gain unless absolutely necessary. I obeyed for about six months until this winter when I had an annoying minor problem with a channel. A small tweak on the Kitztech resolved the annoyance.

I'm sorry to report the preamp hasn't helped. I have only pulled in cbs/fox on 28.1,2 on rare occasions. I guess I will have to move the antenna to the roof in the spring.

I suppose the other option is replacing the clone 4228 with a genuine. But that would be even more disappointing if I still couldn't get fox/cbs.

Maxpower..
I had a clone antenna mounted (outside) on an antenna tower with a better TVfool signal level, but could not get CBS/Fox. Even when I added a CM7777 to the path it didn't work.

When I switched to the CM4228HD, I started receiving CBS/Fox solidly. With the CM7777 I needed to add two splitters in the path so I didn't overdrive my TV tuner.

I am very close to HC/CF so I have a problem with signal overdrive on the CM7777 and will different arrangements in the spring (I might need a CH18 bandpass filter, or ch17 notch filter).

Malcolm

MaxPower, if you want to get WNYF, just like I have suggested (with success) to malstew, I propose you replace your clone antenna with a genuine Channel Master cm4228hd or Winegard HD-8800, with your cm7777, on the roof. At -9.6dB NM for WNYF, you are close to the acceptable limit of getting it all day so you need all the help you can get. You may lose it during the day if you don't have a top notch tuner.

Maxpower - I agree with what the others are advising....get a Channel Master 4228HD or another one from stampeder's chart (http://www.digitalhome.ca/forum/showthread.php?t=97121).

There are good reasons why those with more experience strongly suggest sticking with certain brands. The clones may look identical, but the gain could be much less. In Ottawa, where we are trying to lock on distant signals, every little bit helps.

I have an attic mounted CM4228HD that I've modified per this thread (http://www.digitalhome.ca/forum/showthread.php?t=103749&page=12) with a CM7777 pre-amp. I get WNYF all day long with the odd pixelation or dropout on the worst weather days. In the spring, I'll be evaluating where/how to get this mounted outside to improve the whole setup.

I moved from Carleton Place to about 13 km west of Almonte on Wolf Grove Road. I left my old tower, antennas and rat shack preamp at the old house because there was a tower and antenna at the new place. Problem is I am getting better reception with an RCA 25db amplified rabbit ear antenna in the house than I get from the tower antenna...Here is a photo of the antenna. It has a CM 0064C preamp and a rotor that does not work. I did try rotating the antenna manually but never got any real good reception.

http://i139.photobucket.com/albums/q317/rdyck/100_4463.jpg

Questions...

1. Is there a simple way to test if the preamp is working properly and the antenna wiring and connections are good?

2. Is this a good antenna style when everything goes digital later this year or should I be looking at getting a new one? Any suggestions on what to get?

3. Here is my TVFOOL report link. http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%3d8d173300f656cf

I would be very satisfied to get CBC, TVO, CTV from Camp Fortune and Global, A channel and City TV from Herberts Corners. Right now with the rabbit ears we get CBC good and TVO and CTV is pretty good but has a little bit of snow.

4. Camp Fortune is 56 degrees Mag and Herberts Corners is 94 Mag. Do you think I need a rotor or would an antenna aimed in between be OK?

Thanks...RD

Rudster,
As you mentioned there must be something wrong with either the cabling or the preamp that is blocking the signal getting thru.

1.) Where is the preamp power supply? Is there anything between the power supply and the preamp? You can check to see if it is outputting power to the line. If everything seems to be okay I would try bypassing the preamp to see if that improves things.

2.) You should be in good shape with that antenna -- especially compared to indoor rabbit ears. Digital/Analog use the same antenna -- it is freq range dependant.

3.) You should be able to get all of the channels you mentioned -- assuming good topography between your location and the broadcasting towers.

4.) I would try pointing it at HC and see if you also pick up all of the CF stations.

I agree with what malstew says. Some other questions:

1. What type of wire is being used? If not RG6, replacing it would certainly be beneficial.
2. What is the make and model of pre-amp? If one is needed (based on cable length and use of splitters), using a good one (such as a CM-7777) would also help.

While that antenna will certainly work well for DTV, my only thought is it will be quite directional and if you can't find a single position to aim it to receive everything (though with only 38 degrees between towers, it may not be a problem), using a UHF antenna with a wider beam width (such as a CM-4221) for UHF may be better for you. Post transition, all VHF stations will be from CF, so you could either continue to use your current antenna for that or find a smaller VHF only antenna (just make sure it includes VHF-LO as Global will stay on channel 6).

Roger1818 and Malstew,

The pre amp (CM 0064C) power supply is at the TV...which is about 15 feet from where the coax exits the house and then goes up the tower about 25 feet high to the preamp connection at the antenna.

When it gets a little warmer outside I will replace the coaxial cable (it looks old and weathered) and also try bypassing the preamp. If I don't get a good picture I will try a CM7777.

What is the difference between the CM4228 and CM4221?
Does one have a wider beam than the other?

Thanks for the tips!

RD

I think that by just replacing the COAX you will be able to get everything that you want with the antenna that you have. The question is (I think): can you get all of the channels concurrently with the antenna that you have without having to rotate it?

The CM4228HD is basically 2X the size of the CM4221HD -- it is basically two CM4221HD's mounted beside each other. The CM4221HD has about 2X the beamwidth of the CM4228, and slightly less gain (2dB?). If your current antenna doesn't meet your needs, then as roger1818 mentioned the CM4221HD is probably a good choice (for UHF).

I think that by just replacing the COAX you will be able to get everything that you want with the antenna that you have. The question is (I think): can you get all of the channels concurrently with the antenna that you have without having to rotate it?

I agree with this statement.

The CM4228HD is basically 2X the size of the CM4221HD -- it is basically two CM4221HD's mounted beside each other. The CM4221HD has about 2X the beamwidth of the CM4228, and slightly less gain (2dB?). If your current antenna doesn't meet your needs, then as roger1818 mentioned the CM4221HD is probably a good choice (for UHF).

From what I have read, the CM4221 has a 3dB beamwidth of 45 degrees and for the CM4228 it is 15 degrees, so it is about 3X. As for gain, theoretically the CM4228 has twice the gain (about 3dB), but in reality it is probably closer to 2.5dB.

Rudster - I'm roughly 27 km due east of you, so I find your situation quite interesting.

Signals: At 25' you've got Line of Sight to all of the CF channels, 2Edge to all of the HC channels. The only really practical US channels are 7.1 (CBS) / 7.2 (Fox), which are at -5.1 NM.

The antenna looks like it is one of the Channel Master double-boom Crossfire antennas, but doesn't match any in my (very old) catalog. Looks to be in pretty good shape, but I'd suggest checking the feedline going from it to the CM-0064.

The Channel Master 0064 preamp is a "cousin" to the venerable 7777 mentioned here. Mine is 14 years old, and still working fine, so once you replace your coax yours may be too.

Even so, here's what I'd suggest, if you are willing to spend a bit:
Aim your existing antenna at Watertown, add a balun and connect it to the VHF input of a CM7777. Get a 4-bay UHF antenna (CM4221HD or Winegard HD-4400) and aim it at Herberts Corners (or slightly north), and connect it to the UHF input of the CM7777. Enable the FM trap on the CM7777.

With this setup, you'll probably get ghosting on analog channels, but once the digital conversion is complete, you should get Ch 6 and 13 off the back end of the old antenna, and all the UHF channels on the 4-bay. Bonus: Ch 7.1/7.2 from Watertown may be fairly stable.

The only really practical US channels are 7.1 (CBS) / 7.2 (Fox), which are at -5.1 NM.

Are you able to receive channel 7 from your location with a similar NM? While -5.1 dB NM would likely be receivable on UHF, I am not so sure about VHF. My rule of thumb is to subtract 10 dB from the NM for VHF-HI (channels 7-13) and 20 dB for VHF-LO (channels 2-6).

With this setup, you'll probably get ghosting on analog channels, but once the digital conversion is complete, you should get Ch 6 and 13 off the back end of the old antenna, and all the UHF channels on the 4-bay. Bonus: Ch 7.1/7.2 from Watertown may be fairly stable.

While 13 may be receivable off the back, I am not so sure about channel 6 as it will likely be the most challenging station to receive here in Ottawa due to the very unfavorable characteristics of VHF-LO for DTV (especially channel 6).

Edit: Looking again at his TVFool results, CF is about 120 degrees from channel 7, which will make things even worse for receiving off the back end.