Add me to the list. ;) Heck, even if it were VHF-Hi we would have a shot temporarily. I just wish they would get rid of VHF with this -DT transition and only have UHF. Make it easy for the consumer!


Why not? They need to be slapped. Wait, I'll send Bush over, he will straighten them out. :rolleyes:

It is a different topic for a different thread, but for some reason the CRTC does not like subchannels. I think as long as it doesn't affect the -DT feed, then who cares.

Even a deepest fringe setup would not get a Barrie or London station in Buffalo on a normal, regular basis so this is all kind of moot.

Let's get back to Channel Master gear discussion. :)
Ya, to get CKVR from Barrie you would need to be pointed that way and have a good DXing night. With that said, if CKVR decides to boost out a lot of juice towards Toronto who knows. But it is still 2-3 years away until the deadline, unless of course the CRTC pushes the deadlines back (which I think they will).

My gut though is from Buffalo, CFPL may even be a better bet one day since they have a big area to cover as well.

And now back to the topic :)

I understand that, but reflector or not, it's the driven element that does the receiving, correct? If that is not 'cut' to the correct frequency, does it really matter how good the reflector is?


It receives as a unit other wise why bother putting a reflector on it to begin with. Any piece of metal near the antenna becomes part of the antenna weather it has a wire attached to it or not.

Do to the magic of harmonics; it kind of is cut to the right frequency.

Most antennas will resonate at a odd harmonic of their designed frequency and it just so happens that the 4228 and 4221 do just that.

The problem is that when an antenna operates on an odd harmonic the feed point impedance is much different than it is at its designed frequency. The mis-match causes some loss of net gain unless some sort of adjustments are made.

Both antennas (4228- 4221) with the right reflector have a raw gain near 7-9 dbi on VHF-HI but due to those nasty mis-matches the net gain will be much lower on some channels.

It's no mistake that TV and amateur radio bands are placed at the intervals that they are, that or someone was just darn lucky.

I think as long as it doesn't affect the -DT feed, then who cares.

That is the CRTC's only concern, however adding a subchannel with different content may need to be negociated as part of the license.

Could you gang a 4228 and a 4221? Curious as I have a spare 4221 laying around...

Stu

With identical antennas the effects of ganging are predictable to a great extent, but ganging 2 dissimilar antennas is never an easy or desirable thing. Your CM4228 is actually 2 ganged CM4221s.

Thought as much.

I am going to experiment with this today - ganging two 4221's and then combine that feed with a 4228.

I currently have a 4228 and 4221 combined very successfully. I have a spare 4221 hanging around and will gang it with the single 4221 pointing in the same direction.

So here is my only concern: The feed lines are currently exactly the same length from each antenna to the combiner, as is necessary. When I gang the 4221's must the length of the new ganging wires (the two wires in question will be prior to the 2 way ganging combiner) be factored in to the total length of the combining lines?

Or, does the point of origin of the ganged antennas begin at the ganging combiner, thus leaving the current exact length combined feed lines the same?

I am sure I could have found a less complicate way to ask this question....


Stu

I am going to experiment with this today - ganging two 4221's and then combine that feed with a 4228.

When combining two antennas pointed the same direction, you need want to make everything identical as possible so the signals add together in phase.

For two antennas pointed different directions, in theory it doesn't matter because you're using the two antennas to pick up different frequencies. However, in practice the "idle" antenna will still be picking up some signal, thus it's a good idea to still try to match feedline lengths to try to keep the two signals in phase.

For your situation, the cable from the 4228 to the combiner should be approximately the same length as total length of cable from the 4221 through the first combiner to the second combiner. (I'm assuming the combiner doesn't invert the signal.) Note: even at channel 68 one wavelength is almost 15" so you don't have to be hyper-accurate.

I gather from reading the posts here that the original CM 4228 (not made in China) is the best choice. Is it still available? If so, where could I get one?

I'm in South Surrey, at 126th Street and 19th Avenue. Off rabbit ears, I get variable reception on 2, 6, 8, 10, 12, 26 & 32, although only 6 & 8 are reliable. With a rooftop antenna I'm really hoping to improve the reception!

Any suggestions as to the choice of antenna would be appreciated.

the original CM 4228 (not made in China) is the best choice. Is it still available? If so, where could I get one?Yes, yes, do a search.
2150 doesn't always do so good up north, but this is what I came up with;
http://www.2150.com/broadcast/default.asp?latitude=49%2E060527&longitude=%2D122%2E816893&magnetic_north=17&range=100&sort=distance&show_expired=True&show_construction=True&show_analog=False&show_low_power=False&action=Show+Stations

Those locals being 20-27 miles out are no problem. If you want the next group 37 to 60 miles out, either the 4228 or the 91XG up as high as you can go.
The US stations are over 100 miles out. You are SOL with those. Have you tried looking at antennas from Wade?

tenstu; I wouldn't bother trying to 'gang' those antennas. If you want to use the other antenna, point it in the direction of some closer stations as a 2nd antenna to switch back and forth with instead of turning the main antenna.

Off rabbit ears, I get variable reception on 2, 6, 8, 10, 12, 26 & 32, although only 6 & 8 are reliable.

The CM-4228 is a UHF (ch. 14-69) antenna though it does a good job with VHF-HI (ch. 7-13). It won't work very well with VHF-LO (ch. 2-6).

For digital broadcasts, they are currently on UHF, and are re-mapped to the same channel number as their analog broadcasts.

Hi,

Do you know what's the difference between the CM4221 and CM4221A ?

I heard that there's a new CM4221 coming out soon, so i'm wondering if it's the A? (http://www.channelmasterintl.com/documentation/datasheets/Channel%20Master%20New%204200%20Series%20HDTV%20UHF%20Antenn as_200807.pdf)

dcmoore, check out this thread for a BC source of original CM4228s:

http://www.digitalhome.ca/forum/showthread.php?t=51079

dcmoore, you might want to check out stampeder's post #17 earlier in this thread. It quotes actual field testing of the CM4228 which showed 8-9 dBd of gain for CH7-13 and 2 dBd of gain for CH2-6. If you are able to receive channels 2-6 with rabbit ears, you will have little problem with the CM4228 since 2 dBd of gain is greater than that of rabbit ears. I am currently receiving channel 3 from 70 kms away with a CM4228 and high VHF from 110 kms. Prior to installing the CM4228, with rabbit ears, channel 3 came in quite snowy or not at all.

It quotes actual field testing of the CM4228 which showed 8-9 dBd of gain for CH7-13 and 2 dBd of gain for CH2-6.

Strange. HDTV Primer (http://www.hdtvprimer.com/ANTENNAS/comparing.html) shows a VHF-LO (Ch. 2-6) gain of less than -14 dBd (significantly below rabbit ears) for the CM4228.

http://www.hdtvprimer.com/ANTENNAS/GainVHFnetUHF.gif

I'd be willing to bet that neither the computer simulated gain or the post #17 field test gain numbers are truely correct.
The computer simulation doesn't take into account the end effects of the mounting point where the whiskers attach to the phase lines and touch the plastic mount or other real world factors like the length of the feed line.
End effects can skew the actual results by a fair margin although generally less on channels the antenna is not designed for.
The field test gain results shown in post #17 are way over even what perfect world computer models show and I have my doubts about those gain numbers, especially the VHF-lo gains. Too bad the link to the actual test results isn't working any more, it would be interesting to see how the tests were done.

I've been doing both computer simulation and semi controlled field testing on these style antennas and others (but not an actual 4228). All the real world factors like attaching baluns, amps, different feedline lengths, feed line type, splitters, and height above ground have an effect on wide band antenna performance. Mis-match (SWR) will vary wildly through out the range of the TV spectrum for a 4228 and the factors listed above can add or subtract from that.

I think that the 4228 falls some where near the computer simulated numbers except that the peaks and valleys will not be as extreme and may be skewed by a few channels one way or the other depending on the TV band.

With the link in Post #17 now broken I Googled Kerry Cozad and found some of his documents here:

https://secure.connect.pbs.org/conferences/technology/2005/Presentations/DTV.Receive.Antennas.ppt

http://www.dielectric.com/broadcast/pdf/Measured%20Performance%20Parameters%20for%20Receive%20Antenn as%20.pdf

Here is a link to the actual data in Excel.

http://hdtv.forsandiego.com/messages/4364/Kerry_Cozad_s_Antenna_Gain_Measurements-3502.xls

dcmoore we'll follow up on your requirements in the following thread covering Surrey BC:

http://www.digitalhome.ca/forum/showthread.php?t=36554

You'll find lots of great info in there. :) Also you can read up on the Zenith box in this thread:

http://www.digitalhome.ca/forum/showthread.php?t=42186

Thanks for the links to those pages and spreadsheets, it appears from reading the report that those gain figures are calculated gain figures and the article mentions computer modeling. The gain figures are very similar to the raw gain figures you would get if you computer modeled the 4228. In the computer models I've run for a 4228, raw gains are around 9dbi for vhf-hi and 15 dbi for UHF. The net gain after calculating mis-match loses is much less (as much as 8 db) for some channels on vhf-hi and 0-3 db less on uhf.