CM-7777 / 7778: "New & Improved"? - Page 2 - AVS Forum
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post #31 of 99 Old 03-03-2012, 06:30 AM - Thread Starter
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Quote:
Originally Posted by tylerSC View Post

I have strong, full power local channels within 10 -20 miles, from Greenville/Spartanburg/Asheville ...

Does your high-gain, low-noise Ability HDTV preamp overload from your "strong, full power local channels"?

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Originally Posted by tylerSC View Post

For my other TV, I use an original 4228 into the UHF side of a 7778, and Radioshack rabbit ears into the VHF side for my nearby locals. ...

That's a simple & clever solution.

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Originally Posted by tylerSC View Post

Now if only I could get one of those antennas outside ...

What hinders you from moving an antenna outside? Have you considered all the various mounts: J-pole, chimney mount (easiest), rooftop tripod, gable mount, wall-mount, 2nd-story deck or balcony mount, telescoping mast against side of your house, tower, etc.

Have you seen this thread? Given the info found in it, you will likely see a significant reception improvement and may thus need a lower-gain preamp when you move your antenna outdoors.

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post #32 of 99 Old 03-04-2012, 03:01 AM
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I am not the primary homeowner and family members do not want to fight the HOA to place an "ugly antenna" on the roof. So I am stuck in the attic. And they are mostly satisfied with cable. But I prefer to watch Charlotte channels which are not carried on cable, so an antenna is necessary. The Ability preamp does not appear to overload, and the low noise figure apparently allows me to receive the low power translator signal for WSOC. But I would eventually like to try a Winegard 269 and see what happens.
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post #33 of 99 Old 03-04-2012, 11:03 AM - Thread Starter
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Understood. I've also resisted moving the antenna to the roof. It's illegal for a HOA to place restrictions on outdoor antennas.

That's a excellent report about your Ability preamp not overloading.

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post #34 of 99 Old 03-05-2012, 04:37 AM
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Yesterday I added a Holland splitter and connected the antenna to a second TV, and signal strengths improved on several channels. So, apparently there was some overload from my strong nearby signals that I was not aware of. The 2-way splitter has a one port power pass which I correctly connected to the original TV with the power supply, and the other port leads to the 2nd added TV. The preamp piece is directly connected to the antenna balun. This set up sends a powered signal to both TVs from one CM4248 UHF antenna, including a distant UHF translator, as well as 3 HiVHF channels 7, 9, and 13. Excellent results from the 4248 antenna, which unfortunately is no longer manufactured. I wish Winegard, Antennacraft, or Digitenna could produce a newer version of the Channel Master 4248 UHF diamond design.
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post #35 of 99 Old 03-05-2012, 07:02 AM - Thread Starter
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With your "strong, full power local channels within 10 -20 miles" and such a high-gain preamp, I'm not surprised about the overloading. Have you rescanned since adding the splitter to see if you pick up any additional channels?

Q: What's better suited to the current TV spectrum than a CM-4248 UHF?
A: The mclapp M4 or M8, which have been optimized for both - VHF-hi & the new UHF band - a Made in America single antenna solution for channels 7 to 51.

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post #36 of 99 Old 03-05-2012, 08:48 AM
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Well perhaps the size/shape/spacing of the diamond elements could be redesigned to be optimized for the new broadcast frequencies. And perhaps mclapp could design a new version of the 4248 as well. But I believe the diamond elements of the 4248 capture more signal than the X shaped elements of the 43XG/91XG, along with the extra large corner reflector.
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post #37 of 99 Old 03-05-2012, 09:08 AM - Thread Starter
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CM4248:
Per Ken Nist - http://www.hdtvprimer.com/ANTENNAS/cm4248.html
Quote:


It is a top performer above channel 55.

And UHF now ends at 51.

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post #38 of 99 Old 03-05-2012, 09:37 AM
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Well, I have tried the other antennas and have gotten best results with the 4248. But it is good that the mclapp versions have been designed for the new broadcast spectrum, and they appear to be quality modifications of the original Channel Master bow tie design. But enough talk of antennas and back to the 7777 topic. Has anyone tried the new version yet?
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post #39 of 99 Old 03-05-2012, 09:38 AM
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The modeled antenna is not the CM4248 tylerSC is referring to. This is what a lot of people mean when referring to the CM4248: http://atechfabrication.com/products...aster_4248.htm I use the ones with the diamond shaped directors and they do appear to be better than the 91XG.
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post #40 of 99 Old 03-05-2012, 09:43 AM
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Quote:
Originally Posted by tylerSC View Post

... But enough talk of antennas and back to the 7777 topic. Has anyone tried the new version yet?

I haven't. I just ordered a couple more of the original 7777s for future use.
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post #41 of 99 Old 03-05-2012, 10:08 AM
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Quote:
Originally Posted by arxaw View Post

I haven't. I just ordered a couple more of the original 7777s for future use.

I am preparing to do the same. From where did you order yours?
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post #42 of 99 Old 03-05-2012, 10:33 AM - Thread Starter
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Quote:
Originally Posted by ctdish View Post

The modeled antenna is not the CM4248 tylerSC is referring to. This is what a lot of people mean when referring to the CM4248: http://atechfabrication.com/products...aster_4248.htm I use the ones with the diamond shaped directors and they do appear to be better than the 91XG.
John

John,

Thanks for the link. I hadn't seen that model or web site before. Definitely, looks much better than the inexpensive "stuff" produced in China & marketed here under old trusted brand names.

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post #43 of 99 Old 03-05-2012, 10:45 AM - Thread Starter
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Quote:
Originally Posted by tylerSC View Post

Has anyone tried the new version yet?

We'll probably have to wait until the stock of the current 7777 is very low before we see reports of the new 7777. Especially since the new model has so much less to offer. There may instead be an increase in sales of W-G AP 2870 &/or 2880 when the current CM-7777 is no longer available.

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post #44 of 99 Old 03-05-2012, 02:47 PM
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The Winegard 2870 and 2880 appear promising, as well as the new dual input versions from Antennacraft.
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post #45 of 99 Old 03-05-2012, 04:06 PM
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Quote:
Originally Posted by tylerSC View Post

I am preparing to do the same. From where did you order yours?

http://www.warrenelectronics.com/antennas/7777.htm
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post #46 of 99 Old 03-05-2012, 05:41 PM - Thread Starter
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Quote:
Originally Posted by arxaw View Post

I just ordered a couple more of the original 7777s for future use.

Quote:
Originally Posted by tylerSC View Post

I am preparing to do the same.

Why are you all ordering extra 7777s?

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post #47 of 99 Old 03-05-2012, 05:54 PM
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Just ordered myself, it's the best preamp I've ever used and it's a shame they had to go and change it.
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post #48 of 99 Old 03-05-2012, 06:07 PM
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Why do you ask?
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post #49 of 99 Old 03-06-2012, 03:20 AM - Thread Starter
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I'm just curious. Most people only have one outdoor antenna system. From first hand experience, our previous Quantum 3 CM preamp was still going strong at 4 years of age when I upgraded it to a CM-7777.

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post #50 of 99 Old 03-06-2012, 06:03 AM
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I bought them to install for other people in the future. And I am keeping one as a spare. I live on a ridgetop and we get a lot of lightning!
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post #51 of 99 Old 03-06-2012, 06:18 AM - Thread Starter
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Yes, I've read forum reports that lightning is quite a problem for the ultra low-noise preamps.

Isn't the CM-7777 is supposed to be much better protected from lightning?

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post #52 of 99 Old 03-06-2012, 06:29 AM
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Nothing protects against a direct hit.
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post #53 of 99 Old 03-06-2012, 09:10 AM - Thread Starter
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Agreed. Have you ever had a preamp fail due to either a nearby or direct lightning strike?

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post #54 of 99 Old 03-06-2012, 09:31 AM
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Yes, but not mine personally. But I have had the power supply blown out by a nearby direct lightning hit within 50' of my tower. Amazingly, the preamp itself was unscathed. Lightning does weird stuff.
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post #55 of 99 Old 03-06-2012, 09:59 AM - Thread Starter
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Our CM-0747 PS is pluged into a Belkin surge supressor that's pluged into a GFI outlet. The 2-way splitter's ground connection is also connected to the main circuit breaker panel ground cable. We've had no problems with this set up for 4 years.

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post #56 of 99 Old 03-07-2012, 09:15 AM - Thread Starter
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arxaw,

You may not need a spare CM-7777:
Quote:
Originally Posted by Jase88 View Post

The CM7777 is a decent pre-amp. I feel it's too powerful: Mine feeds about 100' of RG6 into a 4-split, then throughout my home, and I still get some overload on one of my tuners.

Nonetheless the unit has provided several years of trouble-free service through lightning storms, heavy snow, rain, heat, etc.

I did find the f-connectors to be exceptionally delicate. You can't over-torque connectors onto the amp. And the screws that hold the amp to the inside of the weather enclosure corrode quickly.

Digital Home Link

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post #57 of 99 Old 03-07-2012, 11:50 AM
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If the CM-7777 is too powerful, then consider the CM-7778 instead.
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post #58 of 99 Old 03-07-2012, 12:32 PM
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Probably showing my amateurishness with this one, but...

Is the noise rating always of primary importance? Is it possible that the NEW 7777 may be better in some situations because of its higher gain, despite its much higher Noise rating?

I know my Signal-Power and Noise-Margins for each channel at my particular location from my TVFool plot, I can calculate my system losses from antenna to tuner, but how do I use all this to determine if it's pre-amp gain or pre-amp noise that will make or break my application?
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post #59 of 99 Old 03-07-2012, 01:25 PM - Thread Starter
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Welcome to the forum acstolinker

Q. Is the noise rating always of primary importance?
A. A lower noise rating allows you to receive weaker signals. You want your first stage of amplification to be as quiet as possible because all subsequent stages of amplification will in turn amplify the noise from the first stage.

Q. Is it possible that the NEW 7777 may be better in some situations because of its higher gain, despite its much higher Noise rating?
A. Higher gain is only helpful to a point. Beyond that, it significatly increases the odds of overloading your tuner. The higher the gain, the further you need to live from the transmitters and/or the more system loss (cable length & splits) you need to have. For example, the current 7777 is recommended if you live at least 20 miles from most of your transmitters. Thus, with both a higher noise level and a greater potential for overload, the new model is probably not going to be as helpful. Additionally, it only has one input and one amplifier. The current model has separate inputs and amplifiers for VHF & UHF. These facts may explain the number of views of this thread to date.

Q. I know my Signal-Power and Noise-Margins for each channel at my particular location from my TVFool plot, I can calculate my system losses from antenna to tuner, but how do I use all this to determine if it's pre-amp gain or pre-amp noise that will make or break my application?
A. See holl_ands web page: http://imageevent.com/holl_ands/files/ota He is very knowledgeable on this subject.

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post #60 of 99 Old 03-08-2012, 07:30 AM
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Thanks for the helpful reply, ota.dt.man...

As I live 24 to 59 miles from the 19 transmitters in my area, overload is not much of a concern for me, therefore, I have been striving for higher gain. Your answer to my first question helps me to conceptually understand the effects of the importance of the noise of the first stage of amplification. I can see how even a little noise increase early in the system becomes problematic by the time it reaches the tuner.

I did go to holl_ands web page and found lots of interesting info, however, most of it was admittedly beyond me (again showing my amateurness).

Is there a formula to simply add all the pluses, like antenna and pre-amp gain then subtract all the minuses, like coax and splitter losses, then figure in pre-amp and tuner noise margins to arrive at a signal threshold requirement? This way I could determine the effects of different pre-amps by re-working the formula for each of the different pre-amps (new and old 7777, et al).
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