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  • 1 Post By Bama29
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Pre-Amp recommendations

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Old 04-04-2019, 09:02 AM   #1  
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Default Pre-Amp recommendations

My 12 year old Channel Master pre-amp finally kicked the bucket. It has been so stable over the years I have not kept up with current equipment. Is the Channel Master CM-7777 still considered the best choice for UHF and High VHF for fringe reception with a fairly long run? Are there better choices?
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Old 04-04-2019, 05:09 PM   #2  
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The current 7777 is nothing like the old one. There are multiple variations of it and you now actually need to know what you're doing before picking whatever version you end up with.

If you post your TVFool plot, identify your antenna(s), and describe your cable runs, we can better point you in the right direction.
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Old 04-10-2019, 05:42 AM   #3  
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Default What about the Televes pre amp?

I meant to search this before on this forum but I don't recall seeing much about this Televes amp. It's a European company who sells pretty much everything through solid signal although I have found this particular amp on Amazon for about $20 cheaper :

https://www.solidsignal.com/pview.asp?p=536040

They also have a version that allows you to put the three inputs in, two UHF and one VHF. The gain is supposed to be variable as it is supposed to internally regulate amplification based on the signal strength. I can neither confirm or deny these claims. Does anybody have experience with these?

Here's the 2 input version; 3 input similar:



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File Type: jpg Televes preamp.jpg (144.7 KB, 47 views)

Last edited by Chiwaukee OTA; 04-10-2019 at 08:44 AM..
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Old 04-10-2019, 08:53 AM   #4  
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I wonder how they magically solve the phase cancellation problems with combining two UHF antennas pointing in different directions???
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Old 04-10-2019, 10:08 AM   #5  
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Default Televes 3 input mast amp.

Quote:
Originally Posted by Terryl3 View Post
I wonder how they magically solve the phase cancellation problems with combining two UHF antennas pointing in different directions???
Yes, I was wondering that myself . Also, I posted a question on Solid Signal's Tech page. Do you still have their own forum , I wonder what happened? Now , It's actually a Facebook page.

Basically I was asking them if they amplify the signal before they combine it or do they combine it and then amplify it? I had to ask a question a couple different ways and it finally got this answer.
Let me quote:

"sorry for the delay in answering. It auto gain controls the two sources and then combines and then amplifies."

It's also supposed to be a somewhat noisy amp from their own YouTube video.


Last edited by Chiwaukee OTA; 04-10-2019 at 12:38 PM..
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Old 04-10-2019, 03:18 PM   #6  
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Auto Gain??? Thats a variable amplifier, then amp it again after combining??? Someone needs to back to engineering school...RF 101.....I would hate to see the output on a spectrum analyzer.
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Old 04-11-2019, 07:02 AM   #7  
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Quote:
Originally Posted by Terryl3 View Post
Auto Gain??? Thats a variable amplifier, then amp it again after combining??? Someone needs to back to engineering school...RF 101.....I would hate to see the output on a spectrum analyzer.
I Hope someone here can explain the concept of auto-gain. A lot of claims about this preamp.

For some reason, I can see the image I put on the earlier post on my Android phone but no on my Windows PC. Hmmm....

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Old 04-11-2019, 07:38 AM   #8  
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Quote:
Originally Posted by Chiwaukee OTA View Post
Yes, I was wondering that myself . Also, I posted a question on Solid Signal's Tech page. Do you still have their own forum , I wonder what happened? Now , It's actually a Facebook page.

Basically I was asking them if they amplify the signal before they combine it or do they combine it and then amplify it? I had to ask a question a couple different ways and it finally got this answer.
Let me quote:

"sorry for the delay in answering. It auto gain controls the two sources and then combines and then amplifies."

It's also supposed to be a somewhat noisy amp from their own blvideo.

An auto gain circuit is an amp with a variable attenuator. That would make the noise figure worse. The specs say the NF is 10 dB; waaaay too high.

I'm concerned about the combiner. I don't understand how it can be any better than a splitter in reverse used as a combiner. The reviews on Amazon don't impress me.





Source:
https://www.televes.com/us/536040-lo...amplifier.html
click on Documentation > Data Sheet
Attached Images
File Type: jpg Televes Amp Specs_1.jpg (69.9 KB, 19 views)
File Type: jpg Televes Amp Specs_2.JPG (157.8 KB, 20 views)

Last edited by rabbit73; 04-11-2019 at 08:44 AM..
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Old 04-11-2019, 08:11 AM   #9  
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Quote:
Originally Posted by Bama29 View Post
My 12 year old Channel Master pre-amp finally kicked the bucket. It has been so stable over the years I have not kept up with current equipment. Is the Channel Master CM-7777 still considered the best choice for UHF and High VHF for fringe reception with a fairly long run? Are there better choices?
Bama29 never did post his TVFool report, so we can't give him specific advice about a good preamp for him.
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Last Activity: 04-04-2019 03:06 PM
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Old 04-11-2019, 08:26 AM   #10  
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Quote:
Originally Posted by rabbit73 View Post
An auto gain circuit is an amp with a variable attenuator. That would make the noise figure worse. The specs say the NF is 10 dB; way to high.

I'm concerned about the combiner. I don't understand how it can be any better than a splitter in reverse used as a combiner. The reviews on Amazon don't impress me.

Wow, I saw that 10 DB noise figure! While everybody in the amp business is trying to get noise under 1 to 2 DB they're in the stratosphere with noise!

Yes, some of the reviews were pretty bad. Things like putting a defective return back in the box and reselling it! Also the instructions seem to be an issue and then the attachment of the cable with no connectors just clamping the cables. That would make me nervous also.

A lot of people though seem to be happy with it. Either they were doing something wrong before with their other amps and antennas or this thing does help some folks.

I don't think I would buy it because that 10 DB noise figure is horrible! And even though they're saying it's Auto gain, some are saying they still had to adjust it??? I would think if it was idle game they wouldn't have to adjust it.

One reviewer was pissed he put the Televes pre-amp all the way up and had to take his mast back down because it didn't work. Yikes!!

Last edited by Chiwaukee OTA; 04-11-2019 at 08:30 AM..
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