New CHEAP LNA

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GaryG
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Joined: Wed Jan 30, 2013 1:26 am

Re: New CHEAP LNA

Post by GaryG » Tue Sep 16, 2014 10:02 pm

Hello Jon,

Which side of the LNA? I found I had to put the LNA on the antenna side of the filter; if I put the LNA between the filter and the receiver (SBS-3) my range actually dropped quite a bit.

My feeling is that there might be a lot of lower frequency 'noise' being output by the LNA that saturates the front end of the receiver. The filter gets rid of that noise as well as boosting the 1090 signals.

GaryG

jonfear
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Location: Wick St Lawrence
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Re: New CHEAP LNA

Post by jonfear » Tue Sep 16, 2014 10:14 pm

Hi Gary

The filter is fitted antenna side. I got an appreciable increase in messages and range. Clearly the amplifier is wide bandwidth and is amplifying everything it sees. By limiting the bandwidth to c. 1090Mhz definitely helps.

There are small filters on ebay http://www.ebay.co.uk/itm/B1602-SAW-fil ... 19c16842ba.

I will get one and try to put it inline BEFORE the amplifier. The insertion loss will be more than covered by the gain...

Jon
http://www.360radar.co.uk, the new name for MLAT Radar in the UK and Western Europe.

Former PP feeder Bm. No longer feeding. I do not have time to sort out imaginary problems with NTP
when it has been working fine for 2+ Years.

Extranet
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Joined: Tue Jul 01, 2014 5:45 pm
Location: Germany
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Re: New CHEAP LNA

Post by Extranet » Thu Sep 18, 2014 11:12 am

jonfear wrote:Just bought one of these:

http://www.minicircuits.com/MCLStore/Mo ... 7714151058

I too have been having trouble with the RPi seeing the signal though the LNA and decent antenna. Works fine with the GSM antenna which is badly out of band so I suspect far too much gain swamping the front end...I will let everyone know.

Jon
Hi Jon,

When I click your link I get a message from the minicircuits website telling me "Please enter model number or your input is too long.." , can you tell me the model number :)

Thanks

Nigel
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jonfear
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Location: Wick St Lawrence
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Re: New CHEAP LNA

Post by jonfear » Thu Sep 18, 2014 11:36 am

Hi Nigel

Search for VBFZ-1065+ on the mini-circuits website. This is the unit I purchased. I am going to fit it to one of the bigger antenna's tonight!

Jon
http://www.360radar.co.uk, the new name for MLAT Radar in the UK and Western Europe.

Former PP feeder Bm. No longer feeding. I do not have time to sort out imaginary problems with NTP
when it has been working fine for 2+ Years.

jonfear
Posts: 365
Joined: Sat Feb 09, 2013 12:15 pm
Location: Wick St Lawrence
Contact:

Re: New CHEAP LNA

Post by jonfear » Thu Sep 18, 2014 1:22 pm

All

I have a sample of the Gollege 1090MHz SAW filter being sent to me. I will get this fitted to my LNA on the Antenna side and see what difference it makes...

Jon
http://www.360radar.co.uk, the new name for MLAT Radar in the UK and Western Europe.

Former PP feeder Bm. No longer feeding. I do not have time to sort out imaginary problems with NTP
when it has been working fine for 2+ Years.

T-EGJA1
Posts: 107
Joined: Sun Sep 08, 2013 12:11 am
Location: Mid-Devon, UK

Re: New CHEAP LNA

Post by T-EGJA1 » Thu Sep 18, 2014 1:41 pm

That VBFZ-1065+ is a very neat looking filter, however at around £32, it's a little more than I'm prepared to spend for experimenting/testing ....... hence I'm planning to build a filter using the circuit and calculator on this site: http://www.raltron.com/cust/tools/band_pass_filters.asp

I'm currently using a 1/2 wave dipole (nominal impedance 73 ) and 75 ohm feeder; so I entered 75 for RL, 1090 for Frequency and 50 for Loaded Q, which (I think) should give a bandwidth of around 20 Mhz
The calculator then suggests 2x capacitors of 97.3 pF (near enough 100 pF) and one inductor of 1.1 µH (nearest available is 1µH) ... add a piece of Vero board, a small project box and a couple of Type-F chassis connectors and the whole thing should cost less than a fiver ..... whether it'll work or not is another matter ....... I'll let you know in due course
Terry

milairuk
Posts: 34
Joined: Wed Apr 09, 2014 8:12 pm
Location: Chelmsford, Essex

Re: New CHEAP LNA

Post by milairuk » Tue Sep 23, 2014 1:03 pm

jonfear wrote:Ok John

That got my attention! Please tell us more, parts list etc? Looks like double sided FR4 sub-strait. I do love to fiddle with this like this...

Jon
Hi Jon,

Sorry for the delay, been away on holiday, it's the Mini Circuits CBP-1090C+, specifically designed for 1090 Mhz. I just made the PCB from an old piece of single sided FR4 I had kicking around, just cut the input/output tracks with a stanley knife and just soldered all other pads to the copper laminate. It's only got the input and output pads, all others are earthed anyway. I tried to get some PCB's made in HK with their Gerber files, but everyone I tried said they were missing a drill file and a .gko (block diagram) Mini Circuits replied that they didn't use specialised PCB software so I gave up and resorted to the mark 1 Stanly blade !!

John

watsonm
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Joined: Sun Jun 29, 2014 12:19 pm

Re: New CHEAP LNA

Post by watsonm » Wed Oct 22, 2014 9:05 am

Coming late to the party.

Apologies if you folk have already found this out but the dump1090 setting for auto-gain was found to be a misprint in the help according to the software developer.

I have recently set it to the "corrected" value with good results on my installation

Suggest you try --gain -10

Obviously "Your mileage may vary" .... :-)

Mike

watsonm
Posts: 26
Joined: Sun Jun 29, 2014 12:19 pm

Re: New CHEAP LNA

Post by watsonm » Sun Nov 23, 2014 7:54 pm

After some further experiments and the purchase of the Cosy Cave LNA I had the same issue as Jon. Had to wind down the gain otherwise
I started swamping the signal. Also had chance to work out what my PPM needed to be so for now my parameters to Dump109 are :

--gain 37 --mlat --quiet --net --enable-agc --ppm 50 --modeac

I am in a small vilage in the country so do wonder whether a 1090 filter would be of benefit. I have a relay Television mast about half
a kilometre away, but other than that nothing that I aware of....

Mike

bfsapuk
Posts: 2
Joined: Sun Apr 19, 2015 10:26 pm

Re: New CHEAP LNA

Post by bfsapuk » Sun Apr 19, 2015 10:28 pm

jonfear wrote:
The LNA certainly has lots of gain, rather too much in fact. I have had to wind the gain on my RTL dongle back to approximately 40dB otherwise the front end overloads, even with an out of band antenna.
How do you know when you're suffering from overload?

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