Neat way of reducing RFI

[Cathal O'Donghaile]

Good afternoon everyone

I thought I would share a simple and neat way of reducing RFI on the SDR end of things. Previously I posted put everything inside a static bag, but I've tried out something simpler and it works: Put your SDR inside the bag it came in and use a short USB extension cable to plug it into your data collector:

Just punch a hole on the input end to connect the cable.

Cathal

[Andrew Thornett]

That's clever - use the electrostatic protection bag it came in

Sent from Outlook for Android

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From: sara...@googlegroups.com <sara...@googlegroups.com> on behalf of Cathal O'Donghaile <cathalod...@gmail.com>
Sent: Thursday, June 4, 2026 1:09:00 PM
To: Society of Amateur Radio Astronomers <sara...@googlegroups.com>
Subject: [SARA] Neat way of reducing RFI

 

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[Sweet Thing]

A better solution.  The bandpass H line LNA has plenty of gain.  So run reasonably good coax (not RG-58) from the LNA on the antenna shack, back from the antenna to the operating room inside. Then connect the RTL-SDR receiver and of course the computer.  This gets the RFI source away from the antenna.

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[Sweet Thing]

 

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[Don Latham]

elegant.

 

------------
Don Latham
PO Box 404,
Frenchtown, MT, 59846
406-626-4304

 

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From: 'Andrew <sara...@googlegroups.com>
To: sara-list <sara...@googlegroups.com>
Date: Thursday, 4 June 2026 7:11 AM MDT
Subject: Re: [SARA] Neat way of reducing RFI

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[Conrad Cardano]

Hi

I have my sdr connected to my LNA.  

Is that a bad idea?

Conrad

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[Don Latham]

Not at all. but watch two things; power and sdr gain.

 

------------
Don Latham
PO Box 404,
Frenchtown, MT, 59846
406-626-4304

 

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From: Conrad <cardan...@gmail.com>
To: sara-list <sara...@googlegroups.com>
Date: Thursday, 4 June 2026 2:47 PM MDT
Subject: Re: [SARA] Neat way of reducing RFI

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[Stephen Arbogast]

As   Don Latham said   be  careful  of  power  and sdr  gain....  the   RTL-SDR   V3  looks  like this...  

rtl-sdr schematic  or block  diagram

I no longer  use  the RTLSDR  V3.  prefer   the  AirSpy .....  

About   ESD  bags..........    they  are constructed in three  layers   and are only a  partial  solution..   See...  https://www.google.com/search?q=esd+bags+as+faraday+cages&client=ubuntu-sn&hs=O6N&sca_esv=88a6b616b8dc7187&channel=fs&sxsrf=ANbL-n4uHjXE5GAZKwqasfFKEfulN5m61Q%3A1780621741776&udm=50&fbs=ADc_l-aN0CWEZBOHjofHoaMMDiKp9lEhFAN_4ain3HSNQWw-mMGVXS0bCMe2eDZOQ2MOTwmdSduEdP1lcK-3UDyorIbYkF4w9ksckliRqNmnEiwdZq9hi6Uf0JMwEobPco1ddsraLMoix6VFcBVLI33WJ4qzChHA80y2JbwB7Ntoj9wD-E0QQ0ZdtEYmEVOXRtobBmtczcO1eywFdgs0HIQoWFlRkLvAJg&aep=1&ntc=1&sa=X&ved=2ahUKEwi7lpfz9O6UAxWGATQIHf8nNtYQ2J8OegQIEBAD&biw=1156&bih=627&dpr=1.09&mstk=AUtExfBynak4Wc3uMDdUdu3luw5vKgFuhgxnaOV2GSiyqxGMK2qh8NsyB8aDh7PQAiQsKHJrPL6gxcFYUBvOerqJlBCeWQXkM_5kb7dSkRaZbo1oN0MM6cS1xP2iEneaaT22VYWBBcRPY_krSJCAQLF8dA6chOPTskgi1oCCb3oKjF1OVNT4sWcVzBqYSsUDOzdsAzTNE21iGAFfpWZQX4A097ShxJFeMatHHF_d-pZJqaflzMKCk64XyijZDjYucgR80la_lNonwpF3O3imByy4HP_vO0DjL7bMCNQUPKH6VukNdJ_z2CW_E-ocCvFzFdHHRRVg9Hrjq1O1pg&csuir=1&zx=1780621819966&mtid=-iEiaoyOApmH0PEP562emAo

[Stephen Arbogast]

RTL-SDR V3  looks like  this...    very  easy to  over drive the  input.. 

[Scott Elliott]

The pink anti-static bags are just that.  They only have enough conductivity to dissipate static, not kill a rf signal.  You may be seeing more capacitance off the plastic (i've used the 1/2 thick packing version to "tune" a biquad antenna a few MHz by placing it between the active element and reflector)??  Pink esd bags do not have low enough conductivity to do much/any good shielding.   Rigid Cross-linked Polyethylene (Closed-Cell)  like lead insertion black ESF foam Chip Quik ESD-FOAM-BLACK-36X24X0.25 is high carbon and has a conductivity of  Surface Resistance: 10^3 to 10^5 ohms/square https://www.chipquik.com/store/product_info.php?products_id=497012.  It costs about US$10 per square foot on Amazon.  This black esd foam is a poor ham's way to dampen multipath off of, say, a lamp post or other small nearby shiny surface.  This type of foam is a reasonable cheap absorber (for the price, proper emi foam costs a lot more), but not a shield.   This foam must be kept dry.   A proper enclosure has a tight fitting lid that makes intimate electrical contact all the way around.  It is best to pass the signal through bulk head connectors.  All metal paint cans are a cheap option.

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[Cathal O'Donghaile]

Thanks, Scott. I'm going to give that a try. While the static bag is a good RFI reducer, some RFI still remains.