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Author Topic: Pre amplifier problems  (Read 7794 times)

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Bethsalem

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Pre amplifier problems
« on: July 21, 2009, 04:37:00 PM »
Due to the nature of the building I live in it would be very difficult to set up an external antenna.

So in order to improve the sensitivity of the supplied indoor antenna I bought a Moonraker MRP-2000 Mk2 and connected it to the RadarBox via a sma to bnc adaptor to the pre-amp, and then a bnc to sma adaptor from the pre-amp into the RadarBox.  Instead of seeing an increase in flights I'm seeing a big decrease (from 25 to 3!).  Any suggestions as to what I'm getting completely wrong?

Fenris

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Re: Pre amplifier problems
« Reply #1 on: July 21, 2009, 05:27:31 PM »
A wideband preamp could be saturating on a local signal within its frequency range, this reduces the gain on all frequencies and could lead to the symptoms you see.

A properly designed pre-amp for 1090MHz would have filtering to remove signals at significant offsets and be able to cope with strong signals close to the frequency of operation.

Not familiar with the MRP-2000, but I'd guess it is a wideband amplifier from the model number.

malc41

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Re: Pre amplifier problems
« Reply #2 on: July 21, 2009, 07:40:41 PM »
Fenris your suggestion was right the Moonraker MRP-2000 Mk2 is a wideband preamp from 25 to 2000Mhz.

I think you hit the nail right on the head.
15 Miles East of EGNJ

Bethsalem

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Re: Pre amplifier problems
« Reply #3 on: July 21, 2009, 09:14:00 PM »
So basically a wideband pre-amp is fairly useless in conjunction with the RadarBox, but a 1090Mhz model would increase sensitivity and be worth getting hold of?  I've had a look on the internet and can't find any specific models - any suggestions?  Thanks.

GlynH

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Re: Pre amplifier problems
« Reply #4 on: July 21, 2009, 10:20:40 PM »
Try looking at the Elad and the Kuhne.

But don't think a preamp is the solution to all your problems.

Of much more importance is your location, antenna type & mounting, coaxial cable and proper plugs - for example the Westflex 103 plugs are £6 each.

I have had a situation where my 'naked' antenna with 7m Westflex 103 pulls in 500 aircraft in MyFlights and with the Rolls Royce of preamps attached at its proper position at the masthead causes it to drop to 150 aircraft.

Maybe a case of overloading the RadarBox as the preamp states 30dB gain - not sure what the RB would make of an already good signal being boosted by 30dB?

There was another thread here that might help;

http://www.airnavsystems.com/forum/index.php?topic=2640.0

Regards,
-=Glyn=-

CoastGuardJon

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  • Mullion Cove, Kernow --- sw Cornwall UK.
Re: Pre amplifier problems
« Reply #5 on: July 21, 2009, 10:27:50 PM »
Hi Bethsalem, Kuhne 1090 amp, and the Elad 1090 are the best options, both require a Bias-T to send the 12V DC power supply up the co-ax to power the amp..        Neither is a cheap option however.     The Kuhne is regarded as the RR of amps., both need to be as close to the antenna as possible.

http://www.kuhne-electronic.de/en/shop/143_Vorverstaerker/article:342_KU_LNA_1090_A_TM

http://www.hamradio.co.uk/acatalog/Accs_Pre-amps.html

The JIM M-75 is sold under of guises (badge engineering as it used to be known!) but is a broad band amp., and can always be used for scanner if no good on RB/SBS.


Cross posted with Glyn, sorry my typing is so slow!!!!!
ANRB :  AOR AR8000 : Icom R-7000 : Icom IC-R9000 : JRC NRD-545 : OptoElectronics Digital Scout and OptoLinx Interface; Realistic Pro-2005 : UBC 800XLT - listed in alphabetical order, not cost, preference, performance or entertainment value!

Bethsalem

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Re: Pre amplifier problems
« Reply #6 on: July 22, 2009, 09:11:02 PM »
Thanks guys for the advice.  I bought the pre-amp cheap :) and it does improve my airband scanner reception noticeably when I'm out and about using just a "rubber duck" antenna, so no harm done.  As I can't really change the position of my indoor antenna, or get an outdoor one, I'll try to improve sensitivity by changing the coaxial cable and the connector plugs.

t1mb0

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Re: Pre amplifier problems
« Reply #7 on: July 22, 2009, 09:48:53 PM »
homemade antenna with the ELAD is what I have, gives ample 200+ mile range, very happy.
12m SE of EGHI