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-   -   Looking for guidance around preamps (http://forum.tvfool.com/showthread.php?t=16509)

BrooklinOTA 26-Sep-2018 3:12 PM

Looking for guidance around preamps
 
Hi Everyone,

I want to thank everyone for the amazing help I've received so far. Because of this forum, I'm getting some great college football, NFL and sports playoffs all for a bit of work and very little cash.

I have been puzzling over the situation with preamps for some time and I was hoping that someone could help me get some clarity. I understand that a preamp only helps with loss through the cable run and does nothing to benefit reception. Also, I have been discouraged from using a preamp because of the added noise that will be added.

All of that said, it appears to me that my system would benefit from the use of a preamp and here are my details:

Tv Fool report: http://www.tvfool.com/?option=com_wr...9038aaf236a07a

I have a run of 75 feet of RG6 coming from a DB8e going to a Channel Master distribution amp.

Now, when I look at calculations of loss over 75 feet of RG6 and then consider some of the channels I get that can be variable with reception, it seems the preamp would work.

Take NBC, real channel 33 for example. Channel 33 is broadcast at 587 MHZ and over a 75 foot run of RG6 I should be losing around 3.65 db.

So if that is the case, would it not make sense to introduce something like a TVPRAMP1R, that brings 2.6 db of loss into the system? Wouldn't I achieve one extra db of gain and it would help the channel be more stable when the signal is borderline in and out?

Thanks for the help!

jrgagne99 26-Sep-2018 5:47 PM

Quote:

Originally Posted by BrooklinOTA (Post 60326)
...would it not make sense to introduce something like a TVPRAMP1R, that brings 2.6 db of loss into the system? Wouldn't I achieve one extra db of gain and it would help the channel be more stable when the signal is borderline in and out?...

Yeah, you have the general idea. I don't think any of the green stations in your report are strong enough to cause overload. Especially since you are not pointing right at 247 (right?). So I think a moderate-gain pre-amp is worth certainly worth trying.

BTW, you should probably keep this discussion all in the same thread, it makes easier if everything is in one place. :)

BrooklinOTA 26-Sep-2018 6:37 PM

Quote:

Originally Posted by jrgagne99 (Post 60327)
Yeah, you have the general idea. I don't think any of the green stations in your report are strong enough to cause overload. Especially since you are not pointing right at 247 (right?). So I think a moderate-gain pre-amp is worth certainly worth trying.

BTW, you should probably keep this discussion all in the same thread, it makes easier if everything is in one place. :)

Correct, I'm pointing at around 195.

Agreed, this probably should have been tagged onto my other post.

ADTech 26-Sep-2018 9:40 PM

Quote:

I understand that a preamp only helps with loss through the cable run and does nothing to benefit reception.
Actually, that's a mis-statement of how it works, it's pretty much an over-simplification.

A low-noise pre-amp's input noise figure would substitute for the combined insertion loss of the downlead and of the tuner (plus any other losses). Adding one, where appropriate, can extend the noise floor limit by a few dB, perhaps even as much as 6-10 dB for a typical tuner and preamplifier with 75' of RG6. IOW, very weak signals that would get lost in the cabling and tuner's input would have sufficient power to be above the tuner's noise floor and then may possibly be received (there are other factors..).

To do the actual calculations, you'd have to use what's usually called a "Cascaded Noise Figure" calculator or the equivalent to find the "System Noise Figure" when using (or not) a preamplifier.

BrooklinOTA 27-Sep-2018 12:16 AM

Quote:

Originally Posted by ADTech (Post 60334)
Actually, that's a mis-statement of how it works, it's pretty much an over-simplification.

A low-noise pre-amp's input noise figure would substitute for the combined insertion loss of the downlead and of the tuner (plus any other losses). Adding one, where appropriate, can extend the noise floor limit by a few dB, perhaps even as much as 6-10 dB for a typical tuner and preamplifier with 75' of RG6. IOW, very weak signals that would get lost in the cabling and tuner's input would have sufficient power to be above the tuner's noise floor and then may possibly be received (there are other factors..).

To do the actual calculations, you'd have to use what's usually called a "Cascaded Noise Figure" calculator or the equivalent to find the "System Noise Figure" when using (or not) a preamplifier.

Thank you, this helps to make more sense of it. In your opinion do you think it is worth me trying a preamp like the RCA model?

BrooklinOTA 16-Oct-2018 3:24 AM

Just an update. I installed the TVPRAMP1R this weekend and it makes a significant difference. There were no dropouts on NBC (my hardest to reach American station) and the Canadian channels in the null zone are much more stable!

Thanks for the help everyone!


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