Help with pre-amps

Hey all, anyone familiar with any scanner pre-amps? Can you use a cable TV signal booster on a scanner? I know it's 75 ohms, but for receiving only, it should not make any difference. Looking for some info and recommendations. Thanks all

You can use Catv preamps with a scanner, but note that some preamps are noisy, and not good qualty. Better to upgrade to a better antenna system before considering a preamp, Unless you live outside of the city or in the country and away from other towers or transmitters. :wink: 73, n9zas

I've got a decent antenna. I use a diamond 2 meter 440 ham antenna up about 20 feet. Can't get it any higher due to landlord. Plus i live in a valley.

As long as you don't intend to transmit thru the preamp you should be fine than. Also Fyi, amplified Hdtv antennas sometime work well with scanners too, as long as you're out of the city. 73, n9zas

Yes I'm not in the city. Need something to boost VHF/UHF and 800 mhz

jeffm77 said:

Yes I'm not in the city. Need something to boost VHF/UHF and 800 mhz

Click to expand...

Your situation may be different, but I found years ago that a pre-amp overloaded my scanner to the point that it created de-sense, and reception was worse than if there was no antenna connected. But I live in a large city. Things may be different if you're out on the country. Just make sure you can return the pre-amp if it doesn't work out.

The city of Pittsburgh is about 14 miles away from me and the city UHF stuff comes in very weak, however I usually do not listen to them. I am mainly concerned with VHF/UHF and 800 MHZ. Like I said, I have a Diamond dualband ham antenna that I use for ham use and switch over to my base ham radio when I want to get on the air. So, I have an antenna switch I can put in-line with the pre-amp to by pass it during transmitting. I use LMR 400 coax, about a 60 foot run to the antenna. Just VHF, UHF and 800 MHZ reception sucks down in the valley.

TV Preamps often work great, but as said above, watch for overload. Don't worry about the 5075 ohm situation, it makes little difference with a scanner.

I have used better quality TV preamps and splitters, such as Wingard and Electroline with great results. Stay away from cheap junk though.

Rich, can you give me a specific model # to look for or do you have a link? I want to get something good. Thanks.

After much research I purchased an Electroline EDA-2400 distribution amp that works great. Mine is 1 in, 4 out but they make one that is 1 to 1 that would work great at the antenna. Keep in mind preamps are only made to overcome the signal lost in your coax run or spiltter.

Assuming you choose to use a LNA or a Low Noise Amplifier with a very lose noise factor, then you can use a Pre-Amp to pull weak signals out of the noise.

Something like the first amplifier is what I run on a scanner with an inside telescoping antenna. Granted the specs may be for higher frequencies, it works well in the 800 MHz band.

I have a variable power supply and run about 10 Volts or what gives the best quieting.

Mini Circuits ZQL 1900LNW 1850 to 1920 MHz 50 Ohm 37 DBM Low Noise Amplifier | eBay

New Mini Circuits 15542 ZQL 1900MLN LNA 50

Or this - ZX60-33LN-S+

Here is a listing of Mini Circuits LNA's that you can choose from. The lower the Noise Figure the better, but higher 3rd order intercept (IP3) is also good.

If you search around on ebay, you can likely find some used lower cost LNA's. Just be careful about the required Voltage an DO NOT power the amp up without a load or having it connect to the radio. Often powering up higher power LNA without a load on the output can cause the amplifier to fail.

JamesO said:

Assuming you choose to use a LNA or a Low Noise Amplifier with a very lose noise factor, then you can use a Pre-Amp to pull weak signals out of the noise.

Something like the first amplifier is what I run on a scanner with an inside telescoping antenna. Granted the specs may be for higher frequencies, it works well in the 800 MHz band.

I have a variable power supply and run about 10 Volts or what gives the best quieting.

Mini Circuits ZQL 1900LNW 1850 to 1920 MHz 50 Ohm 37 DBM Low Noise Amplifier | eBay

New Mini Circuits 15542 ZQL 1900MLN LNA 50

Click to expand...

I've used 'good' pre-amps for a very long time.

I have a lot of antennas and every single one of them has a pre-amp mounted right at the base of the antenna.
EXCEPT for one antenna. That's my 'reference antenna'.

I also use a lot of the Mini-Circuits ZQL-1900MLN with great success on the higher frequencies only. (above 450 MHz or so..... you can see the gain and NF response below)



For general use, I prefer the LNA-1000 from RF Bay, Inc. and for SatCom and frequencies below 600 MHz the LNA-580 from RF Bay. They're great amps, but pricey.

Several things to keep in mind about using a pre-amp.
More gain is not always a good thing.
Personally, I prefer around 10-15 dbm of gain (at the radio) and a high IP3.

With a higher gain amplifier, you can feed more scanners or reduce the gain using splitters.

'Ball park' losses for splitters:

A 2-way splitter has around 4 dB loss
A 3-way splitter has around 7-8 dB loss
A 4-way splitter has around 9-11 dB loss
An 8-way splitter has around 13.5 dB loss

Those numbers vary widely depending on manufacturer so you have to check the specs.

Some of the cheaper TV type pre-amps can cause headaches. But, they are cheaper so it doesn't cost a lot to try one.

Rich

A few of my spare pre-amps:




Edit:

Here's a sample of one of my distribution setups.
I use two of these boards (less the pre-amp shown) with an LNA-1000 pre-amp mounted at the base of the antenna to feed 32 scanners from one antenna.
It works very well, and it's very clean.

My Broadcastify feed is on a similar setup.



Edit again:
And for a little teaser.........
Here's some SatCom activity received on a Scantenna ST2 and an LNA-1000 pre-amp. (E4000 USB dongle and SDRSharp)

https://www.youtube.com/watch?v=2p5IURvNhP0

.

jeffm77 said:

Hey all, anyone familiar with any scanner pre-amps? Can you use a cable TV signal booster on a scanner? I know it's 75 ohms, but for receiving only, it should not make any difference. Looking for some info and recommendations. Thanks all

Click to expand...

http://preview.tinyurl.com/jaj8rkc

I have had the four outlet model for about four years now. One in the car, one near the captain's chair, and one bedside. Gives about 40% gain in signal "strength" as measured by the HP-1 (E)'s analysis features. Wouldn't leave home without it, lol.

Two of the amps listed here are for the cell phone input bands of 1850-1920Mhz and not intended for use outside that range. Believe me, if they met any useful specs over a wider range then MiniCircuits would advertise that.

Also, lowering the supply voltage to these types of amps lowers the IP1 and IP3 numbers, making them overload sooner, not a good idea.
prcguy

JamesO said:

Assuming you choose to use a LNA or a Low Noise Amplifier with a very lose noise factor, then you can use a Pre-Amp to pull weak signals out of the noise.

Something like the first amplifier is what I run on a scanner with an inside telescoping antenna. Granted the specs may be for higher frequencies, it works well in the 800 MHz band.

I have a variable power supply and run about 10 Volts or what gives the best quieting.

Mini Circuits ZQL 1900LNW 1850 to 1920 MHz 50 Ohm 37 DBM Low Noise Amplifier | eBay

New Mini Circuits 15542 ZQL 1900MLN LNA 50

Or this - ZX60-33LN-S+

Here is a listing of Mini Circuits LNA's that you can choose from. The lower the Noise Figure the better, but higher 3rd order intercept (IP3) is also good.

If you search around on ebay, you can likely find some used lower cost LNA's. Just be careful about the required Voltage an DO NOT power the amp up without a load or having it connect to the radio. Often powering up higher power LNA without a load on the output can cause the amplifier to fail.

Click to expand...

You can buy F anttenuators on line, 2.5 DB, 5 DB, 10db they are cheap. Yes you can stack them. The cable companies use them to turn down a hot signal. They are 12 vdc too.

I use CATV amps in my setup. They definitely can help pull in weak signals. One I use is a 1-in/4-out amp that distributes amplified signals to 3 scanners. It has the advantage of having a gain adjustment in the event I needed to reduce the amplification.

prcguy said:

Two of the amps listed here are for the cell phone input bands of 1850-1920Mhz and not intended for use outside that range. Believe me, if they met any useful specs over a wider range then MiniCircuits would advertise that.

Also, lowering the supply voltage to these types of amps lowers the IP1 and IP3 numbers, making them overload sooner, not a good idea.
prcguy

Click to expand...

You are correct about the frequency band of the amplifiers, but they can and often are used outside of the frequency range. What you need to understand is some products are designed for specific markets/purposes and they can hold tighter specs and flatter gain curves for the intended purpose.

I have been using a number of these amplifiers along with other members here for some period of time without an negative side effects. I have no problem with overload or compression in my environment and just happened to be playing with the amp on a variable power supply with very good results. Many of these amps have the IP1 value only drop by 1-1.5 dB and the IP3 value drop by 2-2.5 dB at reduced Voltages. Given the high values that many of these amps start with the degraded specs for hobby use are still probably way better than the scanner front end.

Until you try something, suggest you stay open minded about it. Just because you think it will not work, does not mean it will not work.

Suggest you look at rbm's comments and plots below of the amplifiers performance outside of the "specs"!

Mini-Circuits Ultra Low Noise Amplifier

New product from Mini-Circuits for under $100.

0.34 dB noise figure in the 800 MHz band!

http://www.minicircuits.com/npa/ZX60-P33ULN+_NPA.pdf

50 MHz - 3 GHz wideband LNA spec sheet.

www.minicircuits.com/pdfs/ZX60-33LN+.pdf

I was able to recently snag a used one of these for $40.

Rather than an amp which will also increase noise, have you considered a beam antenna pointed towards your intended target?