Monday, 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 before using Winkeyer-USB some years ago.
Also using  a USB  sound-device is not without RFI consequences.
This  also could have blurred the weak JA signals last Saturday.
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The FLEX1500
I am using it for WSPR  again on 477 and 500kHz  3.5MHz   28MH.


 It is working fine again  over USB2 Lenovo W510.
No audio-streaming hicks noticed.
CPU % 5-18
I now have the latest version P-SDR 2.3.5
I did not check whether XVTR SPLIT bug is fixed. I did not see it in in the bug fix list. 

For  WSPR the Flex1500 is real nice  I can  select a separate RX  antenna  the K9AY if needed.


This Flex1500 was just spotted by big ears VK7DIK !
 2012-07-23 20:12  PA0O  3.594126  -25  0  JO33hg  5  VK7DIK  QE28sf  16731  84

Good, now I have the K3 free for other things.


One other thing I noticed.
The errors in the CAT  connection N1MM -K3    I had this again few times    Also when logging
JA0RUG at 50MHz ....I had to reset / restart N1MM  to be able to log again.  Of course this will happen preferably at such prime time moment.  Suddenly  call entry was whipped out and the frequency ruler displayed wild out of band showing red zone.
This problem seems to be related with Telnet.  When I closed the Telnet box in N1MM the connection was stable again.



1 comment:

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