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Discussion Starter · #1 ·
Hi,


I'm new to this. I've placed three orders trying to obtain a Channel Master 7777 as suggested by several posters, but all have been out of stock. The last email I received stated:


"There is a shortage directly from channel master on these items. Unfortunately we are also out of stock on this item. I am not aware of any distributor that currently does have stock. Channel Master has recently been aquired by the Andrew corporation and we are hoping that production resumes on the popular amplifier soon, but currently are not aware of when additional stock will become availible."


What would be a good alternative to the Channel Master 7777? I'm about 50 miles from the HDTV source. Any help/advice is appreciated. Thanks.
 

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Discussion Starter · #3 ·
Thanks for the reply ThumperBoy,


I think I need both VHF and UHF. The 7775 is UHF only isn't it? Would the WINEGARD ChromStar Series Pre-Amplifier, AP-8283 be a good substitute? Here's some of the specs:


Average Gain:

VHF - 29 dB

UHF - 28 dB

Average Noise:

VHF - 2.9 dB

UHF - 2.8 dB



Single 300 ohm UHF/VHF Input

Output: 75 ohm


Thanks again.
 

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You can try the Channel Master 7778. There is stock on that - The UHF is 23 versew 26 DB and the VHF is 16 DB.


The Winegard is good!


We will have stock on the 7775 and 7777 in 2 weeks - it is worth the wait.


P.S. The sale of Channel Master had nothing to do with production. It was known that there would be a shortage in the 4th quarter due to production issues.
 

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Interesting, so that explains what the problem is! I too have an order involving a 7777 and it was delayed because of it being out of stock.


I figured it was worth the wait.
 

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I should be picking up a Winegard AP-8700 today. It has similar specs to the Channel Master 7778 I was looking at before (and the 7777 you speak of except less amplification). I should be able to report some firsthand results tomorrow.


Is it better for the pre-amp to have a 300ohm input rather than a 75ohm input? With the 300ohm input I can ditch the external balun which I am thinking might lead to a lower overall NF. But I see the Winegard preamp with a 75ohm input has a NF of 2.8 dB while the same model with a 300ohm inputs has a NF of 3.9dB -- so maybe it's a wash? If someone knows the answer please let me know.
 

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Quote:
Originally posted by STL
Is it better for the pre-amp to have a 300ohm input rather than a 75ohm input? With the 300ohm input I can ditch the external balun which I am thinking might lead to a lower overall NF. But I see the Winegard preamp with a 75ohm input has a NF of 2.8 dB while the same model with a 300ohm inputs has a NF of 3.9dB -- so maybe it's a wash? If someone knows the answer please let me know.
What a great question! Typically, a balun will have an insertion loss of about 1.5 dB at mid-band UHF. You can subtract that from your antenna's gain or add it to your preamp's NF, the result is the same. A NF of 2.8 dB plus a loss of 1.5 dB nets 4.3 dB. The preamp with the 300 ohm input is nominally 0.4 dB better. Note that the quality of baluns vary all over the place and the potential loss could be much higher.
 

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Thanks for the info Old Fogey! I have another question: does it matter where the power injector (for the pre-amp) is located? Is it better to locate it closer to the TV/STB or does its location really not matter at all?
 

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Quote:
Originally posted by STL
Thanks for the info Old Fogey! I have another question: does it matter where the power injector (for the pre-amp) is located? Is it better to locate it closer to the TV/STB or does its location really not matter at all?
It's usually most convenient to locate the power injector at the TV/STB location because that's usually where the AC outlets are and, of course, you can get to it. If you use a surge protector/powerstrip it can be handy to have everything plugged into the strip so that you can remove all power with a single switch. From a signal perspective, it can be located anywhere in the coax run after the preamp.
 

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Thanks again Old Fogey. I have yet another question for you: if I modulate my satellite output on an unused UHF channel (meaning I have no corresponding OTA channel) can I combine that output with my OTA feed with a simple combiner? Here is the modulator I am looking at:
http://www.a1components.com/stores/i...site&item=4448

Here is the combiner I am speaking of using:
http://www.partsexpress.com/pe/pshow...number=180-714


FYI, the Winegard seems to have really done the trick for me. Read more details in this thread:
http://www.avsforum.com/avs-vb/showt...0&pagenumber=4
 

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Warren Electronics sold me a Winegard AP-4800 instead of the OOS CM7775. I was told that CM was not going to ship 7775 or 7777 until mid February. I installed the Winegard today, with a CM4248, and I'm able to pull in every LA DT station that is broadcasting, over 80 miles away.
 
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