[hpsdr] Pre-Distortion

[Helmut, DC6NY]

Ok Michael, you are welcome. Assume legal power level of 1.5 kW, which is
equal + 62 dBm. The typical clipping barrier of the ADC on our HPSDR boards
is -15dBm. That means the necessary isolation has to be at least the
difference of both levels, i.e. 77 dB.
As an ADC provides best resolution and SFDR when driven close to this
barrier, an adjustable attenuation in the feedback loop makes sense to get
close to this level.

73, Helmut, DC6NY 


-----Ursprüngliche Nachricht-----
Von: Owen, Michael [mailto:Michael.Owen at saabusa.com] 
Gesendet: Montag, 9. Dezember 2013 14:53
An: Helmut, DC6NY; 'William H. Fite'; n1jez at burlingtontelecom.net
Cc: hpsdr at lists.openhpsdr.org
Betreff: RE: [hpsdr] Pre-Distortion

Dear Helmut -

Could you please add a little explanation about (a) what isolation you are
referring to; and (b) why 77 dB?  I am still new to this concept.

73,
W9IP

-----Original Message-----
From: hpsdr-bounces at lists.openhpsdr.org
[mailto:hpsdr-bounces at lists.openhpsdr.org] On Behalf Of Helmut, DC6NY
Sent: Monday, December 09, 2013 8:24 AM
To: 'William H. Fite'; n1jez at burlingtontelecom.net
Cc: hpsdr at lists.openhpsdr.org
Subject: Re: [hpsdr] Pre-Distortion

***** High Performance Software Defined Radio Discussion List *****

Hi Bill,

be carefully with this device! 50 dB isolation is NOT enough. For legal
power amps we need at least 77 dB. Bird 4275 seems fine with rated
attenuation 35- 80 dB, depending how deep the coupling element is diving
toward the transmission line. But the device is not rated for frequencies
below 20 MHz.

73, Helmut, DC6NY

-----Ursprüngliche Nachricht-----
Von: hpsdr-bounces at lists.openhpsdr.org
[mailto:hpsdr-bounces at lists.openhpsdr.org] Im Auftrag von William H. Fite
Gesendet: Montag, 9. Dezember 2013 13:48
An: n1jez at burlingtontelecom.net
Cc: hpsdr at lists.openhpsdr.org
Betreff: Re: [hpsdr] Pre-Distortion

***** High Performance Software Defined Radio Discussion List *****



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