Question: Channel Master CM4221-HD - performance data

DW-77

DTVUSA Member
#1
I have a particular combination of local and distant stations, that requires a certain antenna radiation pattern (gain variation over the frequency range wold be helpful, too). Based on reviews, the CM4221-HD looks like it might be a good candidate, but I cannot find any credible technical / performance data for it. The manufacturer web page managed to confuse me.

4-bay HDTV/UHF Digital Outdoor TV Antenna-Channel Master CM 4221HD (CM4221HD)
states: "Designed for UHF/VHF reception from 470 to 700 MHz" and "Antenna Size: 4 x 20 x 36 in"
BUT
http://support.channelmaster.com/attachments/token/0l9p6mcidnys3eg/?name=CM4221HD+Data+Sheet.pdf
states: "Reception Range Channels 14 thru 69" and "Antenna Size (L x W x H) 5.5 x 24.5 x 33 in"

I emailed the manufacturer for clarification, but received no answer. I called technical support asking for radiation pattern and gain variation vs frequency. After putting me on hold and checking with product management and engineering they came back saying that CM does not have such information (I suppose they did design and/or test it, didn't they ???). Someone in the CM sales team told me that the CM4221-HD is being sold for 5 or 6 years, so it seems unlikely that the inconsistencies and lack of data are a "glitch" like the ones that sometime appear while transitioning to a new model...

Enough said. If someone has such documentation (or links to it) and can share, I would appreciate. Thank you.
 
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MrPogi

Moderator, , Webmaster of Cache Free TV
Staff member
#2
I can tell you that this type of antenna is not DESIGNED for VHF, but oftentimes they do pick up strong signals in the VHF-hi (Channels 7-13).
 
#3
I don't think anyone has bothered to investigate that model since manufacturing moved to China 4-5 years ago.

If you want comprehensive tech data, Antennas Direct takes that prize for most of their antennas.
 
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#5
:welcome: to the forum, DW-77.

Here is a chart that comes from Channel Master. A respected poster on another site pulled teeth to get it, and verified the numbers are in dBd, so to get dBi figures you would add 2.15. (BW stands for beam width in degrees, and F/B is front to back ratio in dB).

ChannelMasterChart.jpg

There's also a ton of simulated information, which approximately agrees with the CM chart:
UHF 4-Bay Bowties with Reflector - ImageEvent

If you get the 4221HD (not saying you should), you will definitely want to do the two very simple hacks (not including the reflector modification) they came up with here:
CM4221HD Hardware Hacks - Page 15 - Canadian TV, Computing and Home Theatre Forums

rabbit73 confirmed a marginal improvement for the 4221HD over the original 4221 after the two simple hacks. He did not do the reflector resizing (I wouldn't either). rabbit is a member here, but haven't seen him lately.

Sorry it's so hard to get data out of these people. I had to wade through a dozen broken links to find the above.

If you would post your TV Fool report, with your actual address and antenna height, along with pertinent data about your location, such as trees or buildings in line-of-sight, we can try to help you find the best antenna. TV Fool

Rick
 
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#6
email sent to Channel Master support:

Greetings,

I'm a contributor on dtvusaforum.com and have recommended your 4221HD antenna many times. I notice there is an apparent change in the specifications of that popular antenna, but I've seen no notice from Channel Master to that effect. Your recent ads reflect the new model, while many documents on your site still reflect the old. Here is the new data:
• Antenna Size: 4 x 20 x 36 in
• Designed for UHF/VHF reception from 470 to 700 MHz
• UHF reception range: 65 miles
• Average gain (dB): 3.5/10.2 VHF/UHF
• Turning Radius: 10”

And here is the old data from your own 4220 series PDF manual online:
- Reception Range, Channels 14 thru 69, Up to 45 miles
- Antenna Size (L x W x H) 5.5 x 24.5 x 33 in.
- Turning Radius 12.25 in.
- No gain was ever listed for VHF

As you can see, these specs are quite different. Also, Amazon has the 4221HD listed as "discontinued by the manufacturer"! Any news you care to share? Is this a new model??

Thanks in advance,
Rick XXXXXX
 

DW-77

DTVUSA Member
#7
Thank you Rick,

I am aware of the "hacks", and I agree with you about the reflector: it's good the way it is. I also called / emailed CM tech support about all the issues / inconsistencies we both noticed, but they did not seem to care.

My goal is to be able to receive the channels that are clustered around 243 deg; both UHF and VHF, so I am thinking to point the antenna there. Then, whatever is strong enough to come in from the back and sides, I will take as a bonus. No "antenna rotator". I would prefer to put the antenna in the attic, and the NM data is for that height. According to TVFool, raising the antenna another 10 or 15 feet would not buy me any NM improvement (other than being in open air).

Main concerns / challenges:
1. Co-channel conflicts on 31 and 33 (calls for good front to back separation).
2. Strong local station on channel 49 (makes amplification impractical, unless the antenna has a deep notch at 141 deg with respect to the main lobe).
3. A pretty diverse combination of VHF and UHF channels.

The StellarLabs 30-2440 looks like a good solution (if the specs published on the MCM site are real; which MCM was not able to verify). The alternative would be separate antennas for UHF/VHF, and in that case I would consider the DB4e for UHF (seems to be on par with the CM4221HD, but the support + warranty offered by Antennas Direct leaves CM in the dust).

With that being said, I am open to your suggestions and advise.
Once again, thank you for offering to help.
 
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#8
Well, looking over your homework I don't see any stations in the green (NM>34) at 243 degrees, so I think you've set yourself a tough challenge. Have you had antennas working well for you in the attic? If not, it's very hard to predict whether this plan will ever get off the ground. It depends entirely on the building materials in your roof and attic. The pink stations (NM < 15 or so) are probably a lost cause with an attic installation. With that in mind, it looks like WABC RF7 is the most important VHF station for you, so I wouldn't be looking at the 4221HD. 4-bay bowties are generally designed for UHF, and any high VHF tends to come from 10-11-12-13. Don't know about the "new" 4221HD -- if it is new -- if you can get that model -- if it has gain figures specific to frequency. Too many questions there.

I have an unusual suggestion. Can you get a small TV up in the attic and test it with a cheap dipole / loop combination? You can get an RCA 111R or equivalent from Walmart for about $10, and we often recommend that as a kind of poor man's signal meter. Idea being, if you can't get anything from the attic, then a stronger antenna isn't going to create signal out of vapors. In other words, if you can't get WHPX RF26 at 33 NM, you won't get anything below 20 NM with the best antenna ever made. You probably won't even get anything below 25 NM, which wipes out 243 degrees completely.

If you want further advice, I would plead with you to copy the link that appears toward the top of your TV Fool Report and share that with us. There's a lot of information missing from your copies, and we're just used to dealing with the reports sorted by signal strength (NM). Your exact address is automatically withheld to protect your privacy.

Are you aware of any trees or buildings in line-of-sight to 243 degrees? Anything like that would definitely put a crimp in the attic plan. Not kill it, necessarily, but a crimp, for sure.

Rick
 
G

Guest

Guest
#9
Sure, here it is: TV Fool

I realize that attic installations are far less predictable, and I do not expect miracles. Here is the other side of "homework" I did so far:

Tried the Philips SDV2950 antenna, which is made of 2 pretty basic dipoles - one for VHF / one for UHF - combined on a pre-Amp with separate inputs. Put it in the attic, with a 20ft cable run to my TV downstairs, and had pretty stable reception down to channels that have NM of 20dB in the list (inlcuding channel 7). Occasionally, I was also able to see channels down to 15dB NM (inlcuding channel 13).

I also tried a non-amplified (Antennas Direct) Clear Stream 4. With that, most of the stations that show a NM above 10dB are quite stable. This phase began 3 weeks ago, and re-confirmed the commons sense theory that antenna gain is better than amplification. I have solid reception on channel 13 now, but lost channel 7 (no surprise here, since the CM-4 is rated as a UHF only antenna).

Yes, there are trees, and I am about to find out what impact they have as soon as the leaves come out and it rains :).

While I am not opposed to putting the antenna outside, I would like to try the attic first, as it seems to be somewhat "RF friendly". My next step would be to find an antenna that has moderate gain for VHF, as well as good UHF gain. The Stellar Labs 30-2440 looks good "on paper".
 

DW-77

DTVUSA Member
#10
Sure, here it is: TV Fool

I realize that attic installations are far less predictable, and I do not expect miracles. Here is the "hands on" side of the homework I did so far:

Tried the Philips SDV2950 antenna (which is made of a VHF dipole and a UHF dipole, combined on a pre-Amp with separate inputs). Put it in the attic, with a 20ft cable run to my TV downstairs, and had pretty stable reception down to channels that have NM of 20dB in the list (inlcuding channel 7). Occasionally, I was also able to see down to 15dB NM (inlcuding channel 13). Kept that up for about 1 month.

Then tried a non-amplified (Antennas Direct) Clear Stream 4. With that, most of the stations that show a NM above 10dB are quite stable. This phase began 3 weeks ago, and re-confirmed the common sense theory that antenna gain is better than amplification. I have solid reception on channel 13 now, but lost channel 7 (no surprise here, since the CS-4 is "UHF only").

There are trees, and I am about to find out what impact they have, as soon as leaves come out and it rains :).

While I am not opposed to putting the antenna outside, I would like to give the attic a fair chance first, as it seems to be somewhat "RF friendly". My next step would be to find an antenna that has 6 to 8 dBd gain for VHF, and UHF gain at least as good as the Clear Stream 4. From that perspective, the Stellar Labs 30-2440 looks pretty good "on paper". If that fails, I would consider separate antennas for UHF and VHF, connected via a combiner.

Again, thank you for your comments and suggestions.
 
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#11
Tried the Philips SDV2950 antenna (which is made of a VHF dipole and a UHF dipole, combined on a pre-Amp with separate inputs). Put it in the attic, with a 20ft cable run to my TV downstairs, and had pretty stable reception down to channels that have NM of 20dB in the list (inlcuding channel 7). Occasionally, I was also able to see down to 15dB NM (inlcuding channel 13). Kept that up for about 1 month.

Then tried a non-amplified (Antennas Direct) Clear Stream 4. With that, most of the stations that show a NM above 10dB are quite stable. This phase began 3 weeks ago, and re-confirmed the commons sense theory that antenna gain is better than amplification. I have solid reception on channel 13 now, but lost channel 7 (no surprise here, since the CS-4 is "UHF only").
Excellent! Did you return the CS-4? Seems a shame to waste it if you still have it.

Yes, there are trees, and I am about to find out what impact they have as soon as the leaves come out and it rains :).

While I am not opposed to putting the antenna outside, I would like to give the attic a fair chance first, as it seems to be somewhat "RF friendly".
Absolutely. I like your strategy and your flexibility.

My next step would be to find an antenna that has 6 to 8 dBd gain for VHF, and UHF gain at least as good as the Clear Stream 4. From that perspective, the Stellar Labs 30-2440 looks pretty good "on paper". If that fails, I would consider separate antennas for UHF and VHF, connected via a combiner.
Combining UHF and VHF doesn't cost you anything. It's not the same as combining two UHF antennas. I'm a little tired right now, but tomorrow I'll look over your TV Fool link and pretend you never mentioned 243 degrees -- just to see what I come up with. I might come up with ignoring everything but 243 and buying a Stellar Labs 30-2440!! Stranger things have happened ... :cheers:

Rick
 

DW-77

DTVUSA Member
#12
Thank you Rick. The CS-4 is up there, doing a pretty good job, pointed at 243deg-M. It also "happens to have" (read: "I scrubbed many radiation patterns to find this one"), a notch at 24deg-M, to lower the level of channel 49. (The idea is to reduce the gap between the strongest and the weakest channel, so that I can add a pre-amp or a distribution amp, if needed.)
Since most of the channels of interest, in both bands, are in the same direction, I think having a single antenna would make sense and is worth trying (as long as the UHF side of that antenna is at least as good as the CS-4). Should that fail, I can keep the CS-4 and combine it with a VHF only antenna. :)
 
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#13
email sent to Channel Master support:

Greetings,

I'm a contributor on dtvusaforum.com and have recommended your 4221HD antenna many times. I notice there is an apparent change in the specifications of that popular antenna, but I've seen no notice from Channel Master to that effect. Your recent ads reflect the new model, while many documents on your site still reflect the old. Here is the new data:
&#8226; Antenna Size: 4 x 20 x 36 in
&#8226; Designed for UHF/VHF reception from 470 to 700 MHz
&#8226; UHF reception range: 65 miles
&#8226; Average gain (dB): 3.5/10.2 VHF/UHF
&#8226; Turning Radius: 10&#8221;

And here is the old data from your own 4220 series PDF manual online:
- Reception Range, Channels 14 thru 69, Up to 45 miles
- Antenna Size (L x W x H) 5.5 x 24.5 x 33 in.
- Turning Radius 12.25 in.
- No gain was ever listed for VHF

As you can see, these specs are quite different. Also, Amazon has the 4221HD listed as "discontinued by the manufacturer"! Any news you care to share? Is this a new model??

Thanks in advance,
Rick XXXXXX
Here is Channel Master's response and my follow up:

----------------------------
Hi Rick,

Thank you for the email. We still produce the 4221HD antenna.

Please refer to the ChannelMasterStore.com website specs they are most current.

I will make sure the PDF manual gets updated.

Thank you again,

Isaac XXXXXXXX
Product Marketing Director
Channel Master

----------------------------
Hi Isaac,

Thank you for confirming there's a new model of the 4221HD antenna that's taller and thinner than the one I bought a couple years ago.

From the new gain figures it appears these changes have increased high VHF reception for the 4221HD while marginally decreasing gain in the UHF band. Can you confirm either one of those conclusions?

Everyone at dtvusaforum.com is excited about the new model and anxious to learn whatever we can.

Best,
Rick

----------------------------

I concluded there must be a new model, since my 4221HD is not 36 inches tall and is more than 20 inches wide. I measured again to be quadruple sure.

So we'll see if I can squeeze some more data out of the marketing department.

R.
 
#14
Then tried a non-amplified (Antennas Direct) Clear Stream 4. With that, most of the stations that show a NM above 10dB are quite stable. This phase began 3 weeks ago, and re-confirmed the common sense theory that antenna gain is better than amplification.
It's not that antenna gain is better than amplification gain, it's that amplification gain literally doesn't count when you do a signal to noise calculation -- and that's the only calculation that normally affects reception, since the first thing the signal hits in your TV is an amplifier/attenuator. All signals are at the same level by the time they reach the demodulator. Noise is the only thing that matters at that juncture.

So you can add antenna gain to noise margin, but you should not add amplifier gain to noise margin. Of course, every antenna manufacturer, without exception, adds antenna gain and amplifier gain to get completely meaningless "total gain" figures on their indoor antennas. Only thing an amplifier can do is amplify the signal when it is the cleanest -- just as it comes out of the antenna -- so the noise from a long cable run or any splitting LOOKS smaller to the TV amp. But an amplifier also adds its own noise, so very often an amplifier does more harm than good.

Our top expert here on antennas has a policy of never recommending amps for indoor antennas, and I agree with him.

I have solid reception on channel 13 now, but lost channel 7 (no surprise here, since the CS-4 is "UHF only").
Makes sense.

There are trees, and I am about to find out what impact they have, as soon as leaves come out and it rains .
Unless you have a small forest, it'll probably be fine.

My next step would be to find an antenna that has 6 to 8 dBd gain for VHF, and UHF gain at least as good as the Clear Stream 4. From that perspective, the Stellar Labs 30-2440 looks pretty good "on paper". If that fails, I would consider separate antennas for UHF and VHF, connected via a combiner.
My concern is the Yagis (triple booms included) are very directional. The C4 has three nice lobes off the back, and my impression (please correct me if I'm wrong) is you're getting almost everything from the north-east, even though it's pointed south-west. Those stations might :bolt: with a Yagi

The CS-4 is up there, doing a pretty good job, pointed at 243deg-M. It also "happens to have" (read: "I scrubbed many radiation patterns to find this one"), a notch at 24deg-M, to lower the level of channel 49. (The idea is to reduce the gap between the strongest and the weakest channel, so that I can add a pre-amp or a distribution amp, if needed.)
I wouldn't even think about adding a pre-amp unless you have more than 75 feet of coax or you're splitting to three or more receivers. Even then, I'd try to go amp-less.

Since most of the channels of interest, in both bands, are in the same direction, I think having a single antenna would make sense and is worth trying (as long as the UHF side of that antenna is at least as good as the CS-4). Should that fail, I can keep the CS-4 and combine it with a VHF only antenna. :)
Well, YOU are the ultimate expert on your channels of interest, so I support whatever decision you make. I'd like you to try the tri-boom, just because I'm curious about that antenna, so I'd hit you up for all kinds of data and review. But I have to admit, if you hadn't brought it up I'd be thinking along the lines of adding a VHF dipole to your C4 (somebody said the one you can get for the C2 also works for the C4). That would be the cheaper way to go, and I like those odds better.

Rick
 

DW-77

DTVUSA Member
#16
Thank you Rick.

You are absolutely correct about antenna gain vs amplification; the way I worded it before was just "trying to make a long story short". :)

Yes, I am receiving several channels from the back of the antenna (they make it through the reflector due to their high level). Besides those, with 1 or 2 exceptions, I am also getting all the channels that TVFool shows with a NM higher than 12, at 243 degrees. I am primarily using the F/B separation of the antenna to resolve the 31&33 co-channels conflicts coming from 42&44 degrees; there is some "collateral damage" (that lines up pretty well with my expectations based on "the numbers").

You are also right that the cheapest solution would be to add a dipole to the CS-4. Antenna Direct offered to sell me one, along with a UHF/VHF combiner. The issue I may face with that is that channel 11 and 13 might require more VHF gain than that provided by a simple dipole. (I am getting ch.13 "as a bonus from the CS-4" now, but would be losing it as soon as I pass that signal through a VHF/UHF combiner).

About the triple boom Yagi, I am as curious as you are (if not more). Most "standard" Yagi radiation patterns I have seen have small lobes in the back as well, but I am not sure how that plays out for a triple boom. I like to verify things on paper before engaging other resources and climbing the roof (or the attic), but without any relevant data form the manufacturer / re-seller, it is like shooting in the dark. If I decide to the 30-2440, I will let you know and share what I learned.
 
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#17
(somebody said the one you can get for the C2 also works for the C4).
Second thought, I think that poster was joking. I'd go for a Y5-7-13, if the 5 feet will fit in your attic. You would need a UVSJ combiner and a 300-75 Ohm balun for that, so total comes to about $45. There should 0.5 dB max loss from the combiner.

Or else try the tri-boom. :cheers:
 
#18
While you're at it, read this thread: http://www.dtvusaforum.com/dtv-hdtv...nna-solution-me-antennaweb-info-included.html

Similar situation to yours, if you care about the north-east stations. (The one station at 11 degrees is so strong, it'll blast through whichever way you're pointed.) 4221HD without the reflector would be a logical way to start, but you'd probably wind up still needing the Y5-7-13.

But I believe enough in black magic that I hesitate to mess with that miraculous C4.

Or try the tri-boom. :evil:
 

DW-77

DTVUSA Member
#19
Oh, BY THE WAY! I found a spec sheet for the C4 antenna, even though there's no link to it on Antennas Direct site. Just in case you don't have it, here's a link: http://www.antennasdirect.com/cmss_files/attachmentlibrary/AD_SpecSheet_C4.pdf

R.
I did not have that datasheet, thank you for sharing it. And here is a bonus I can add: when I called Antennas Direct about the CS-4, the support rep did not seem to know about this file, but was kind enough to obtain and email me the radiation patterns at 3 different frequencies (as 3 separate B/W JPG files). I combined them into 1 image, and sent the result back to Antennas Direct. You can have it, too:
ClearStream4_Horiz_Plane_Pat.jpg
I am sure Antennas Direct won't mind, since there isn't any "secret sauce" here; if anything, it should help more people decide to buy this antenna, which I found excellent. Realizing I have praised Antennas Direct more than once in this thread, I must mention that I have no "vested interest" in this manufacturer. I am just very pleasantly impressed with their product documentation and customer support. If more manufacturers followed similar standards in these two aspects, we would be living in a better world.
 
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#20
I combined them into 1 image, and sent the result back to Antennas Direct. You can have it, too:
Muchas gracias. I've added it to my antenna library. Here's a page from tvprimer: ClearStream4 from AntennasDirect.com

I just wish there was any clue what the peak dBi number is. People get so hypnotized by graphs, they leave out the most obvious, most crucial data. Apparently gain is raw gain, since writer speaks of a drop off below channel 12, but it doesn't show up on the graph. But the comments are good, I thought.

I am sure Antennas Direct won't mind, since there isn't any "secret sauce" here; if anything, it should help more people decide to buy this antenna, which I found excellent. Realizing I have praised Antennas Direct more than once in this thread, I must mention that I have no "vested interest" in this manufacturer. I am just very pleasantly impressed with their product documentation and customer support. If more manufacturers followed similar standards in these two aspects, we would be living in a better world.
Unless they're trying to sell you something, in which case they'll make up whatever answer you want to hear! AD went waaaaay over the top in their DB4e roll out. JMHO.

Rick
 

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