[Premium-Rx] WJ-8711A Additions and Digital Noise Issues

[Steve Pappin]

Subject: WJ-8711A digital noise radiating from the tuning encoder shaft 
above 15 MHz.

I just uploaded an article pertaining to the WJ-8711A and radiated tuning 
encoder shaft noise. Noise may become an issue when antennas are located 
near the radio. The article is on the PCS FTP site. This article also 
applies to the HF-1000A. As far as I can tell this issue is officially 
undocumented. It is one of the reasons why the WJ-8711A in native form does 
not meet MIL-STD-461. A number of significant changes are required to stop 
the front panel from radiating.

Best Regards,
Steve


----- Original Message ----- 
From: "Steve Pappin" <pappy92651 at yahoo.com>
To: <premium-rx at mailman.qth.net>
Sent: Thursday, July 19, 2012 11:40 AM
Subject: [Premium-Rx] WJ-8711A Additions


> One of our list members donated new WJ-8711A files to the FTP site. The
> manual and appendices should now be 100% complete.
>
> History: I started working on these radios 10 years ago. At the time I did
> not have the sophisticated equipment that I have now. I am starting to
> service them again and I have a few new observations.
>
> Notes:
>
> 1) The front end of the 8711A, especially with the pre-amplifier on is
> extremely sensitive, -137 dBm.
> 2) Connections inside this radio are touchy, AMP IDC and compression
> connectors
> 3) The front panel is a noise source and does not meet MIL-STD-461 
> (radiated
> & conducted emissions to EN55022, Class B)
> 4) The radio is actually a repackaged 8712 with a front panel interface
> 5) The later firmware versions make the radio much easier to use and 
> control
> 6) WJ-RCS or other software make the radio much easier to use but add
> computer noise
> 7) A well grounded steel or aluminum enclosure are necessary to control
> front panel, computer, and internal noise
> 8) All cables running to the 8711A should be as short as possible and well
> shielded
> 9) A centralized earth ground is essential to making this receiver perform
> properly
>
> Summary: This radio is actually a micro-controller mated to RF and analog
> sections with a front panel interface. The switching power supply is well
> shielded. The front panel is not well shielded. The tuning encoder shaft 
> is
> a major source of radiated noise. Careful attention to proper grounding 
> and
> cabling are required to fully utilize the capabilities of this radio.
>
> Best Regards,
> Steve
>
> ______________________________________________________________
> Premium-Rx mailing list
> Home: http://mailman.qth.net/mailman/listinfo/premium-rx
> Help Page: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Premium-Rx at mailman.qth.net
> Help Contact eMail:  paul at 8zo.com
> Home Page:  http://www.premium-rx.org/