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 Post subject: Inline Pre Amplifier
PostPosted: Mon Aug 24, 2015 9:32 am 
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Joined: Tue Oct 26, 2004 11:40 am
Posts: 581
Location: Snohomish County, WA
Been researching wideband pre-amplifiers hoping to improve reception of the SERS system.

For example:
http://www.scannermaster.com/WRP_1300_Pre_Amplifier_for_Wideband_Scanners_p/28-531167.htm
and
http://www.universal-radio.com/catalog/preamps/2422.html

However, both of these seem to be discontinued and not for sale by the normal radio geek stores or eBay auctions.
Anyone have have suggestions of equivalent product that can be purchased for <100 bucks?
Or willing to loan me one to test out just to see if it actually makes an improvement on my end? If I knew that it made a big improvement I would probably be willing to spend a little more $$.

Thanks

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 Post subject: Re: Inline Pre Amplifier
PostPosted: Mon Aug 24, 2015 9:56 am 
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Joined: Tue Jul 03, 2007 8:11 pm
Posts: 2151
Location: Puget Sound
Im trying to remember the model I have in my lowband repeater and once I fire up my laptop Ill be able to get the link. If I remember right they made everything up to 900 and were fairly inexpensive. But they were band limited compared to your links.

Preamps are (hopefully) linear devices and will amplify everything in their designed bandpass meaning the whole noise floor will raise in that particular band, right? If you are using less than half inch from your receive antenna to your receiver you might look into improving that for the 800 stuff. Or possibly try 75 ohm RG6 cable if you have any lying around.

Preamps will only amplify what makes it to them in the first place.

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 Post subject: Re: Inline Pre Amplifier
PostPosted: Mon Aug 24, 2015 10:16 am 
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Joined: Tue Jul 03, 2007 8:11 pm
Posts: 2151
Location: Puget Sound
Just found this-

http://www.amazon.com/Ramsey-Broadband- ... B0002NRKMG

This is what is in my lowband and I have one for UHF in the shop.

http://www.advancedreceiver.com/

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 Post subject: Re: Inline Pre Amplifier
PostPosted: Mon Aug 24, 2015 10:56 am 
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Joined: Tue Oct 26, 2004 11:40 am
Posts: 581
Location: Snohomish County, WA
chpalmer wrote:
Just found this-

http://www.amazon.com/Ramsey-Broadband- ... B0002NRKMG

This is what is in my lowband and I have one for UHF in the shop.

http://www.advancedreceiver.com/


Thanks for the links.
The Amazon one is temping. Very easy for me to return it if it did not do the trick.

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 Post subject: Re: Inline Pre Amplifier
PostPosted: Mon Aug 24, 2015 6:48 pm 
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Angus Cheeseburger
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Joined: Thu Feb 19, 2004 5:09 pm
Posts: 4759
Location: CN88st
It would be a good idea to get something with an adjustable gain pot. I have had problems with inline amps from the antenna causing overloading the front end of the scanner which will cause noise and desense of the scanner. I have that little GRE amp and it works pretty well on a portable with a rubber duck antenna for it's input. I also have an old Grove Power Amp II that works well with a small antenna. The ability to adjust the gain really helps to get it to do the job properly.

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Last edited by Jim on Mon Aug 24, 2015 6:55 pm, edited 1 time in total.

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 Post subject: Re: Inline Pre Amplifier
PostPosted: Mon Aug 24, 2015 6:52 pm 
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Joined: Tue Oct 26, 2004 11:40 am
Posts: 581
Location: Snohomish County, WA
Jim wrote:
It would be a good idea to get something with an adjustable gain pot. I have had problems with inline amps from the antenna causing overloading the front end of the scanner which will cause noise and desense of the scanner.


Ya I thought about that too. The problem is, as I mentioned, I can't find anything available to buy.

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 Post subject: Re: Inline Pre Amplifier
PostPosted: Tue Aug 25, 2015 8:13 pm 
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Joined: Mon Jan 03, 2005 1:17 am
Posts: 2643
Location: Lost on 405
So what radio are you looking to add this for? Portable, Desktop/Mobile or RTL SDR? If it's for a base station then do you already have an outdoor antenna?

A suggestion: you might consider buying both a high and low pass filters and form a trunking band-pass filter.

Example: This one would attenuate signals up to 740mhz: http://www.minicircuits.com/pdfs/VHF-740+.pdf

This would allow signals up to 950mhz and block everything above: http://www.minicircuits.com/pdfs/VLFX-780.pdf

Since these are SMA connectors, the good news is this will work readily on a portable scanner (at least the Uniden scanners.)

Mini-circuits also has amplifiers if you're so inclined. They're much higher quality and have excellent resale value.

An example broadband amp: http://www.minicircuits.com/pdfs/ZFL-1000LN+.pdf

Here's an 800 Mhz version: http://www.minicircuits.com/pdfs/ZX60-0916LN+.pdf


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