Using Pre-Amp With Multicoupler

[kvg911]

Hello,

I have a strideberg 4 port multicoupler with power source attached to it. I have one of the pre amps from scanner master and noticed it dosent make much of a difference and actually seems to hurt the signal strength.

Even when I put it directly on a scanner it dosent seem to do much except hurt me.

WRP-1300 Pre-Amplifier for Wideband Scanners
WRP-2500 Pre-Amplifier for Wideband Scanners

http://www.scannermaster.com/Pre_Amplifiers_s/45.htm

Those are the amps I was using.

Any input?

 

[prcguy]

If you tell your doctor it hurts he will usually tell you to stop doing it.
Most people in an urban environment will experience what you describe because there are enough local high power pagers, cell phone towers, FM broadcast towers, etc to overload a pre amp and cause Intermod. The problem is worsened when that feeds another amp in the multicoupler. You can sometimes alleviate some of the problem by filtering out FM broadcast and paging before the pre amp but this turns into an expensive science experiment unless you have the equipment to measure all the offending signals to determine what to filter out.
Tell us more about your setup like what kind of antenna, what kind of feedline and how much, distance to nearby towers and what bands you listen to.
In the end a pre amp and filtering is best placed at the antenna to set the system noise figure and to make up for feedline loss. Placing it right at your scanner will raise the signal levels and the pre amp probably has a better noise figure than the scanner but it will not improve the signal to noise ratio enough in most cases to to make it worth while unless you have a very old tube type receiver with a numb front end.
If you can successfully use a pre amp without causing problems you would usually use a passive splitter to feed several receivers because the pre amp will generally have more than enough gain to make up for feedline and splitter loss.
prcguy

Hello,

I have a strideberg 4 port multicoupler with power source attached to it. I have one of the pre amps from scanner master and noticed it dosent make much of a difference and actually seems to hurt the signal strength.

Even when I put it directly on a scanner it dosent seem to do much except hurt me.

WRP-1300 Pre-Amplifier for Wideband Scanners
WRP-2500 Pre-Amplifier for Wideband Scanners

http://www.scannermaster.com/Pre_Amplifiers_s/45.htm

Those are the amps I was using.

Any input?

 

[pappy1]

If you tell your doctor it hurts he will usually tell you to stop doing it.
Most people in an urban environment will experience what you describe because there are enough local high power pagers, cell phone towers, FM broadcast towers, etc to overload a pre amp and cause Intermod. The problem is worsened when that feeds another amp in the multicoupler. You can sometimes alleviate some of the problem by filtering out FM broadcast and paging before the pre amp but this turns into an expensive science experiment unless you have the equipment to measure all the offending signals to determine what to filter out.
Tell us more about your setup like what kind of antenna, what kind of feedline and how much, distance to nearby towers and what bands you listen to.
In the end a pre amp and filtering is best placed at the antenna to set the system noise figure and to make up for feedline loss. Placing it right at your scanner will raise the signal levels and the pre amp probably has a better noise figure than the scanner but it will not improve the signal to noise ratio enough in most cases to to make it worth while unless you have a very old tube type receiver with a numb front end.
If you can successfully use a pre amp without causing problems you would usually use a passive splitter to feed several receivers because the pre amp will generally have more than enough gain to make up for feedline and splitter loss.
prcguy

Ok, that explains it for city folks. Now explain it for county folks.

I live in a hay field somewhere near plum and nearly ( plum out of the City and nearly out of the County) and the nearest tower of any kind is approximately 21 miles as the crow flies, the nearest neighbor almost 1/4 mile. I have the same problem with the GRE pre-amp and useing a 4 port amplified cuppler. The cuppler has no amplification other than to have 0 loss at each port. Now the good part: I hooked up the preamp with a wall wart for power and I have no difference in signal what so ever. There is no RF anywhere around me other than what I create myself.

My question is: Why am I haveing the same problem out here as I would in the City?

 

[N_Jay]

Ok, that explains it for city folks. Now explain it for county folks.

. . . . The cuppler has no amplification other than to have 0 loss at each port. . . .

BECAUSE the Coupler has an AMPLIFIER in it. The fact that the gain of that AMPLIFIER is set to offset the loss of the coupler does not make the AMPLIFIER go away. It still have the same overload potential of any other AMPLIFIER.

Cascading amplifiers is a tricky matter.

 

[zz0468]

Ok, that explains it for city folks. Now explain it for county folks.

I live in a hay field somewhere near plum and nearly ( plum out of the City and nearly out of the County) and the nearest tower of any kind is approximately 21 miles as the crow flies, the nearest neighbor almost 1/4 mile. I have the same problem with the GRE pre-amp and useing a 4 port amplified cuppler. The cuppler has no amplification other than to have 0 loss at each port. Now the good part: I hooked up the preamp with a wall wart for power and I have no difference in signal what so ever. There is no RF anywhere around me other than what I create myself.

My question is: Why am I haveing the same problem out here as I would in the City?

In order to see any improvement, the noise figure of the preamp-multicoupler combination HAS to be lower than the noise figure of the receiver itself. If it's a low quality preamp with a high noise figure, that alone could kill any improvement. The next thing to watch out for is too much gain from the preamp overdriving the amplified multicoupler.

Preamps can be a bit tricky to actually get improvement, and just tying off the shelf stuff together like that is a safe bet that it's actually hurting, not helping, weak signal reception. I'm not the least bit surprised it's not helping you.

And pushing all that hot air aside, you may well have a bad preamp, if it's not doing a thing.

 

[pappy1]

In order to see any improvement, the noise figure of the preamp-multicoupler combination HAS to be lower than the noise figure of the receiver itself. If it's a low quality preamp with a high noise figure, that alone could kill any improvement. The next thing to watch out for is too much gain from the preamp overdriving the amplified multicoupler.

Preamps can be a bit tricky to actually get improvement, and just tying off the shelf stuff together like that is a safe bet that it's actually hurting, not helping, weak signal reception. I'm not the least bit surprised it's not helping you.

And pushing all that hot air aside, you may well have a bad preamp, if it's not doing a thing.

Well the pre amp may be bad as it will not do anything hooked to a hand held with stock duckie. Thanks for the reply as it gives me a starting place.