[Premium-Rx] Harris RF-590 bandpass filter and noise blanker

[John Reed]

  ----- Original Message ----- 
  From: Jim Sorenson 
  To: premium-rx at ml.skirrow.org 
  Sent: Monday, April 19, 2004 3:58 PM
  Subject: [Premium-Rx] Harris RF-590 bandpass filter and noise blanker

  The specs on the built in preselector for the 590A (RF-596A-02/RF-1317A) read as follows:

  Bandpass filter (2-29.99 MHz) 20 dB attenuation +/- 10% from tuned frequency
  Lowpass filter (1-1.999 MHz) provides HF attenuation when receiver is tuned below 2 MHz.

  I think the lowpass filter should read 1 KHz to 1.999 MHz.  It won't do anything for broadcast interference.  I would get a good high pass filter with a cutoff at 1.6 to 1.8 MHz.  There are some available.

  On the noise blanker, I asked Harris about this accessory once and got sticker shock.  As I remember the price was around $2000.  They must have thought I worked for Uncle Sam.  I built my own.

  John Reed


  Gentlemen:

  I wonder if anyone out there knows anything about the tunable bandpass filter (10073-6550) that comes as an option on the RF-590? Before I run it through a series of non-destructive tests (I hope), it would be nice to have some specifications on it. 

  The manual only says "Provides over 20 dB of selectivity at +/- 10% of tuned frequency. Reduces interference from close transmitters".  This leaves me with a number of questions, particularly since the RF-551A preselectors that were part of the Harris package (embassy in this case) cut off at 2.0 mHz and have no apparent effect at 1.80. I've got it out at the moment, so putting it back in may improve sensitivity over top band range by overcoming desensitization due to front end overload/blocking (numerous broadcast antennas overlook me from the Mohattam Hills which are less than a mile away) traded off against any inherent insertion loss involved  It was never checked out below 3.5 mHz before I pulled it out. It's likely that this bandpass filter also cuts in around 2.0 and nicely attenuates signals below 2.0 mHz as designed. At least it's presumebly tunable by the layman.

  I've also tried to tweak the 551 down those 20 kcs. with mixed results. I need the schematic for the 551 as well. If I just worked for Harris.

  Also, does anyone know anything about the noise blanker option (1073-6800)? It did not come installed on this receiver and I'm curious if it might well be the magic bullet I seek to vanquish the army of florescent lights that surround me. It's set up so the green light goes on when you push the button, but still no blanker.....

  Many thanks for your help and suggestions from out there....

  Jim
  SU9AM/W3BH










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