: Channel Master OTA Gear & Antennas
2005-10-18, 02:00 PM
I have no technical reason to believe that the CM4228 is an effective AM radio antenna, nor will I bother since a simple loop antenna will do just fine for AM, as Jeffy confirmed. FM is another story, as I've already shown.
2005-10-18, 03:50 PM
when i setup my CM on Friday, I will try it out and let you know. I think on my reciever I will need to convert from 75 ohm to 300 ohm, as the AM and FM inputs are similar to speaker wire inputs...
2005-10-18, 05:03 PM
Does this added reception only apply to the CM4228, or would you get the same from the smaller CM4221?
As I only have a single HDTV and just one decoder, it would be nice to get some of the analog channels on the other TV's as a bonus. My wife likes channel 9 and it just happens to be in the direction that the antenna is going to be pointing. I don't need the distance that the 4228 offers, but the added VHF would be handy.
Also, is the mesh on the back of the 4228 a reflector? I have a second antenna pointing 90degrees the other direction behind where I want to put the ChannelMaster. I am told to get one with a back refector. Just want to make sure.
2005-10-18, 06:43 PM
Yes, the mesh is the reflector, playing a very important role in gathering signal. Without a mesh, a bowtie antenna is fine, but with a mesh the odds of getting the correct sequence of photons arriving on the bowtie are much, much higher so a digital lock is easier in fringe or low signal areas. A CM4221 is a classic bowtie reflector, while a CM4228 came about when Channel Master mounted two 4221s on the same crossbar side-by-side, feeding into the same balun. It was not their intention to provide VHF-high or FM reception, but it turns out that they were pleasantly surprised that the new dimensions did just that! :)
2005-10-19, 05:45 PM
A tip for those who are thinking of a dual antenna setup.
I have been fiddling with my antenna on the weekends because I noticed that Nbc signal has dropped to 7-8 out of 10 even though the signal is fine. Fox would fluctuate between 7 and 10 on certain days.
I have come to the conclusion that if you are going to mount a dual antenna on top of each other on the same pole then the angle between them cannot be great.
I closed the angle on 4228(Nbc) towards the 4221 until the signal started to drop off and went back a little east.
I then repeaked 4221 for Fox closing the angle.
After the repeaking Nbc now comes in at a steady 10 and Fox 9 to 10. Toronto One also shot up one bar to a steady 8. Before Sun/Toronto One was 6.
Maybe I have to much time on my hands as everytime I watch ota tv I have to check the signal strength in the menu and make sure is at max signal. :D
If you are going to use a dual antenna setup and depending on your location if the angle between Toronto and Buffalo is great, its best to have the antenna apart from each other. Make sure the RG6 cable going to the combiner/splitter(in reverse) is the same length.
2005-10-27, 12:51 AM
I'm in a similar boat with the 4228 and the 4221. Currently I have the 4221 pointing to Buffalo, and the 4228 to Toronto from South Etobicoke.
I've gotten things to the point where I am mostly happy. The antennas are very close to each other but I can't mount one on top of the other. I currently have about 20 degrees differnce between the two antennas, and they are as close as I can get them side by side.
My problem seems specific to CTV. Anything I do to increase the weaker Buffalo stations (ABC and NBC in my location) above 7 bars seems to hurt CTV. The recieve will show 8 bars for CTV, but I start to notice pixelation and then it will jump up and down from almost zero signal to 8 bars. Results are identical with the 4228 disconnected, but if I disconnect the 4221 I get a solid 10 bars.
Is it possible that CBS (39) is interfering with CTV (40)? Any other ideas? I'm thinking about phsically moving the antennas apart further but that's the only idea I have so far. How far would they have to be apart? Does the length of the cable into the splitter need to be the same if they are physically separated?
2005-10-27, 04:05 AM
I'm in a similar boat with the 4228 and the 4221. Currently I have the 4221 pointing to Buffalo, and the 4228 to Toronto from South Etobicoke.Have you tried the 4221 to Toronto and the 4228 to Buffalo?...they are as close as I can get them side by side.That's not good, given that they feed into the same line. There are formulae out there from engineers about how much lateral space must be kept between interconnected antennas on the same band, but to simplify I would suggest moving them a few more feet further apart, or if at all possible moving them to non-overlapping altitudes. Anything I do to increase the weaker Buffalo stations (ABC and NBC in my location) above 7 bars seems to hurt CTV... Is it possible that CBS (39) is interfering with CTV (40)?The ATSC standard all but eliminates adjacent channel interference. This is a case of the lobes of one antenna's reception profile negatively affecting the other antenna.I'm thinking about phsically moving the antennas apart further but that's the only idea I have so far. How far would they have to be apart? Does the length of the cable into the splitter need to be the same if they are physically separated?Glad we're thinking the same on this. Keep the cable leads identical, but definitely move them apart if you cannot make one higher than the other. Let us know how it goes.
2005-10-27, 10:04 AM
Brewmaser what stampeder said I agree with.
To fix your problem the two antenna cannot be close by, move them apart and then you can repoint them to each city.
If both antenna's are on the same pole then the angle between the two cannot be great.
I would say between a 20' window.
Make sure the cable length of both antenna's going to the combiner is the same lenhth.
Since I have closed the gap on my setup all signals are strong and stable.
Question are you using a pre amp with a Bellexpress for the atsc signals ?
2005-10-27, 01:58 PM
I saw this on Winegard's website:Identical antennas in same direction with equal lengths of lead between antennas and coupler will give 0 to 3 dB gain. Identical antennas in opposite directions will give -3 to -4 dB loss. Different antennas in any direction will result in -3.5 dB average loss.http://www.winegard.com/offair/couplers_print.htm
2005-10-27, 02:00 PM
I'm in a similar boat with the 4228 and the 4221. Currently I have the 4221 pointing to Buffalo, and the 4228 to Toronto from South Etobicoke. ... Could the problem be that you have too much signal for CTV? I found that I could get both Buffalo and Toronto from a single unit. After reading about line amps and pre-amps, I would think that if you get 100% with the 4221 disconnected, then the added signal from the 4221 might be pushing the signal too high and getting errors?
Have you tried to turn your 4228 about 10deg towards buffalo, and disconnect the 4221? I am wondering if that might work better. Also have you tried just hooking up a small amp to boost the signal (say 5-10db) with just the single antenna?
I guess it all depends on with just the 4228 hooked up, what are the signal strenghts for buffalo?
2005-10-27, 10:27 PM
I do appreciate everyone's input, but I think tonight I reached the point where I have decided that I need either an antenna switcher with both the anteanas or a rotor and dropping one of the antenas. One man can only spend so many hours going up and down a ladder.
I've tried all the suggestions listed so far, including both attenuating and amplifying the individual antennas, but there always seems to be a problem with one or more stations. I did discover tonight that there are definately some problem areas in my attic (even a foot of lateral motion would make a huge difference), but still couldn't find a location for the antennas that didn't create significant issues with one or more stations when both antenas are connected. The only staions I never have problems with are Fox, CBS (23), CBC, and PBS.
If I didn't have the antenas in the attic, and didn't have so many large trees around I'm sure this would be easier.
The last semi-permanent setup I had where only CTV was suffering is about the best I have seen, however I'd like to get CTV as well.
Thanks again. I'll update my results with the 4228 and 4221 once I finalize which way I am going.
2005-10-27, 10:29 PM
Question are you using a pre amp with a Bellexpress for the atsc signals ?Nope, I'm using a Samsung 451. I've tried both with and without the preamp.
2005-10-27, 10:39 PM
Brewmaser sorry that you are having a hard time receiving all the channels properly.
If you can get the signal in your attic, Iam wondering why cant you mount the antenna on your roof you would be even higher than in the attic ?
I would end up selling the 4221 and get a rotor to use it with the 4228. If you intend to run a few tv then keeping the preamp would be a good choice.
2005-10-27, 11:50 PM
Ahhh the elusive roof. Unfortunately that has a low WAF (wife acceptance factor). I might give things one more shot and mount the two antennas outside under the roof line with them stacked vertically. I was looking around outside tonight and I actually have a clearer line of sight if I drop things down as the trees around here are quite old and there is a good clear space below the canopy of leaves.
2005-10-28, 12:48 AM
Ohh the WAF :p
Good luck, and this weekend weather should be good for any installs.
2005-11-01, 02:48 PM
I just wanted to update the thread with a follow up on my 4228 install. Well, last week I trimmed all my cables and mounted them neatly on my fuse panel. I ended up trimming ~12 ft from my antenna feed. I also cut custom sizes for my preamp power supply, ground block, etc...
Well, it appears the interim cable I was previously using from my ground block to my preamp power supply was killing my signal levels. I once tried splitting my antenna feed in two and NBC kept dropping out; CITY and SUN wouldn't even register. You wouldn't know this cable was bad from looking at it. The connectors were Snap'n Seal compression plugs and the cable is RG6. This was easy to troubleshoot, because it was the only cable in the path that was removed.
Currently, I have a short cable from my preamp power supply going to a 3-way splitter. From there, I feed two cables to my Family Room (one for Samsung HD Box; other for Analog on TV) and one to my PC room upstairs (HDTV Wonder). The upstairs cable is another ~40 ft extra and coming off a -7db port, but I have more than enough signal to receive all channels.
The best part of all this, is I have a very strong signal on NBC and ABC (I tuned the antenna for NBC). In fact, my weakest channels are CITY (7 bars) and SUN (6 bars). All with no rotator. Me very happy!
Only downside is a slight compromise on WNYO. I get a bit of noise, thin horizontal lines in the background, on WNYO 49 and Global 41 (could it be my preamp?). I'm surprised at how good a picture I get from CHCH 11 and CTS 36. Considering I'm aiming at Buffalo, I didn't expect such clear Hamilton reception.
In conclusion, originally I was disappointed with my 4228, but I guess it wasn't the problem to begin with. One crappy little cable was the reason for my lackluster signal. All channels were fine as long as I didn't split the signal. Now, I can split to my heart's content with very little effect.
2005-11-01, 03:48 PM
Only downside is a slight compromise on WNYO. I get a bit of noise, thin horizontal lines in the background, on WNYO 49 and Global 41 (could it be my preamp?).I would guess that since those two channels are so close in the frequency spectrum yet not close geographically that there is some sort of interference in the local environment. If it was your preamp it would probably affect all channels similarly, not just two of them in a particular range. Do you get any other analog or DTV stations in or near the UHF channel 4X range? If so, are they also affected the same way? Does your preamp have a tuneable FM trap on it? If not, you might want to add one between the antenna and the preamp and just turn the trimmer to see if the picture trouble disappears.One crappy little cable was the reason for my lackluster signal.I am soooooo glad you discovered the Achilles Heel in an easily accessible place and not way up top at the antenna! ;) Congratulations on your hard work and success!
2005-11-06, 09:39 AM
"thin horizontal lines" are there 2 of them at a time moving through your picture? If so they are Hum Bars caused by a ground loop.
2005-11-07, 01:54 AM
"thin horizontal lines" are there 2 of them at a time moving through your picture? If so they are Hum Bars caused by a ground loop.
No, the picture is more like thin lines in the background. I did a screen cap on my ATI but it's hard to re-create the interlacing effect. I hope the link I used works. Picture 2 is the closest to the real effect.
I think the artifact in the picture could just be an aiming issue. Like I posted before, we were in a bit of a rush aiming the antenna so it may need a little tweaking. I was using the signal meter on my SIR-T151 to tune in WGRZ-DT. I am tempted to add a rotor in the spring.
Today's wind actually caused one of my channels to have difficulty. CITY-HD was cutting in and out. I was surprised to see CITY cut out because I thought channel 66 was weaker on my gear. I hope some of these Canadian stations reconsider and bump up their power. 1.2KW for City seems very low. Looks like Global will be the really pathetic one (3 KW on Ch. 65). Considering the high channel numbers, a little boost would help tremendously. Especially for those of us aiming at Buffalo :)
2005-11-07, 02:06 PM
Jeneral, ATSC channels like WB49 Buffalo should come in either crystal clear or not. This is called the cliff effect and if it was an aiming issue you would have pixellation and audio cutouts happening before sudden and complete failure of the signal, but not interference.
When I see the graininess of the picture quality in the screen caps you made I'm concerned that there is interference downstream of your antenna. It almost looks like weak herringbone, which is a dead giveaway for interference. As I mentioned earlier, its significant that only certain frequency zones are affected (UHF channels in the 40s) so there might be some sort of environmental interference from a nearby FM station or something else. I hope its not another crappy little cable ;)