Question, where to connect preamp & loses at cable connector.

gary350

DTVUSA Member
#1
I bought a channel master 7777 preamp I hope it arrives by mail today. I bought a new 25 ft RG-6 cable too.

Questions is. Where should I put the preamp? I know there is some loss in the cable if I put the pre amp at the TV the signal will be weakest there and high frequencies looses are higher than low frequencys so if there isn't any signal or very low signal in the high frequency range there won't be anything to amplify. Will it be better to put the preamp closer to the antenna? I also plan to raise my antenna about 20 ft so I will either need another 25 ft cable or replace all the cable with a 50 ft cable. How much lose is at the connected where two 25 ft cables are connected together? I could use the preamp at the connecter between the two 25 ft cables.

Information on new RG6 coax cable box losts the lose per 100 feet of cable, 100 MHz = 2.1 dB, 200 MHz = 3.1 dB, 400 MHz = 4.4 dB, 700 MHz = 6.0 dB.

Channel freq. are 692, 608, 554, 518, 481, 197, 185 MHz.

My antenna is 2 channel master 4228s in parallel. After I raise the antenna I think I will only need 1 antenna.

I am in a neighborhood that does not allow antennas so my antennas are 6ft from the ground so they are not very noticable. I tried 1 antenna it only picks up a few channels but 2 antennas work much better. I tried the antennas in the attic they work better outside. Signal will be much better if the antenna is up high so I am planning to put it up 20 ft. My house is on a slight hill I am probably 10 to 15 ft above all the houses that block the antenna signal but there are trees. With the antenna up 20 ft I will be above the trees.
 
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SWHouston

Moderator
Staff member
#2
Combining Two Antennas with a Pre-Amp

Greetings Gary,

It's a pretty general rule, that Pre-Amps "push" better than they "pull".

That meaning you put it close to the Antennas, letting it get it's best signal, and sending that on down the line. The Power Inserter for the 7777 can be anywhere in that line, as long as it's not blocked by a Non-Passive Splitter.

And the two Coaxs leading down to the Amp, be the same length.

The fewer Linear Feet, and the fewer connections promote the best signal. So, any way you can eliminate such, the better. So yes, you can place the Inserter between the two 25' lengths, as long as it is INSIDE a protected area.

Now a couple of comments...
I'm sure you're aware that the 7777 is a very powerful Amp, and usually recommended for Transmitter/Antenna distances of 45 miles or more !

They are sometimes used when Cable Lengths approach or are greater than 100', though a Distribution Amp may be a better choice for that condition.

Given that there may be other Antennas other than the 4228 which are more capable of VHFhi, I'm wondering why you are using two of them. You do understand that the 7777 is a "split" Amp, having one input for VHF and another for UHF, with one single output.

Have a good Day ! :)
S.W.
 

Don_M

DTVUSA Member
#3
:welcome: , gary!

Yes, you want the pre-amplifier module on the mast, as close to the antenna as possible. The 7777's box should contain an instruction sheet, which will explain everything you need to know for a goof-free installation. In particular, please pay close attention to the switch settings. There are two: The first is for selecting a singe antenna versus combining separate VHF and UHF antennas; the second is for turning the built-in FM trap on or off.

Until the amp and instructions arrive, here's a basic wiring diagram that should help you envision the installation:



Splicing two cables together as you describe might make a difference with marginal signals in an un-amplified system, but your 7777 will take care of that little problem nicely. Use a bullet connector for the splice. Don't attempt to splice the cables by stripping insulation and twisting the bare wires together; doing this almost never works. If the splice ends up outdoors in the final installation, be sure to use a waterproof sealant to keep corrosion-causing rain and moisture out of it.
 
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SWHouston

Moderator
Staff member
#4
Gary,

I know I speak for all the regular Guys on the forum here, all of us want to try to help you do what YOU want. Helping someone fulfill a project/goal makes us all happy.

However, when the occasion arises where we think someone is going overboard on something, I think it's reasonable to advise someone of that.

That may be the case here.

Are you trying to build the highest gain system you can ?
Are you aware that may not provide you the best viewing experience ?
There's a limit as to how much signal your equipment/tuners can handle.

If you will, post a Chart for your location, and we'll look at it with you, ok !
If you don't know how to do that, just click on the link below my Signature.

Have a good Day ! :)
S.W.
 
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