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@@ -75,6 +75,7 @@ By running auto_rx continuously, not just at known radiosonde launch times, you
   * A receiver with a TCXO is *mandatory*, and you must make sure the PPM offset value is set correctly ([see here](https://github.com/projecthorus/radiosonde_auto_rx/wiki/Configuration-Settings#important-settings)). The demodulators are quite sensitive to frequency offsets, and the warm-up drift of the non-TCXO RTLSDRs is enough to throw it off. I've had great success with the [RTL-SDR.com 'v3' dongles](https://www.rtl-sdr.com/buy-rtl-sdr-dvb-t-dongles/). The [NooElec SMArt](https://www.nooelec.com/store/sdr/sdr-receivers/nesdr/nesdr-smartee-sdr.html) dongles (with the TCXO option) are also good.
 * An antenna suitable for receiving on 400-406 MHz (a basic [1/4 wave monopole](https://m0ukd.com/calculators/quarter-wave-ground-plane-antenna-calculator/) is usually good enough). If you have an 70cm amateur-band antenna, that will probably work fine too.
 * For optimal receive performance, a preamplifier and a band-pass filter, like [this one](https://store.uputronics.com/index.php?route=product/product&path=59&product_id=54). You can still achieve pretty good results without one.
+* For those in the US trying to receive 1680 MHz LMS6 sondes, a higher gain antenna (short helical) and a [preamp](https://www.nooelec.com/store/sawbird-plus-goes.html) is required.
 
 ## 3. Setup & Configuration - Docker
 Probably the easiest way to get auto_rx going is using Docker - A guide on setting up using Docker is available here: https://github.com/projecthorus/radiosonde_auto_rx/wiki/Docker