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Showing posts from July 23, 2012

Keeping the noise floor clean. WSPR with the FLEX1500

USB -serial converters   can rise the local noise level  by 3- 6dB. General eliminating digital originated noise is  much more important then using a low noise pre-amp of course. A low noise pre-amp is made useless by this noise.  If the USB-serial is just plugged in without any RFI protection it can spoil the noise floor on higher bands like 50MHz  and others ( i did not test yet 70) But I noticed  a serious  noise increase when starting the logger program. Also a intermittent noise burst effect 1/ second can be noticed. This noise burst runs synchronised with the data string over the serial port.   When starting N1MM CAT communication over the USB-serial the base noise clearly came up 3-6dB   Then  using the big toroid and a better shielded USB cable it was better. It is tricky this USB-serial chip noise because it will not stop immediate after closing the CAT communication. It will hang in  some 5-10 seconds before the USB device steps to lower activity. I noticed this


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