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Topband: Virtually All Modern Ham Gear is Un-shielded!

To: topband@contesting.com
Subject: Topband: Virtually All Modern Ham Gear is Un-shielded!
From: Jim Brown <jim@audiosystemsgroup.com>
Reply-to: jim@audiosystemsgroup.com
Date: Sun, 11 Oct 2015 13:44:56 -0700
List-post: <topband@contesting.com">mailto:topband@contesting.com>
On Sun,10/11/2015 6:09 AM, JC wrote:
Another issue with DDC radios available nowadays is the lack of shield, they 
looks like a computer board and that's it, performs like a computer board. No 
good RF practice to protect the noise floor or common mode noise. Really not 
ready for field use.

ALL modern ham gear is either unshielded or poorly shielded. Anyone who thinks ham gear is shielded either hasn't looked at I/O wiring or doesn't understand the fundamentals of shielding!

In all the gear I looked at in Dayton last year, only the RF output coax connector is screwed down to the chassis. Virtually all other cable shields go THROUGH the chassis to a circuit board, as do all other signal and control cables. They are not even bypassed to a chassis. When a cable goes THROUGH the chassis without making contact, it CONDUCTS RF into the box, so what's inside the box is not shielded. This is in addition to "the Pin One Problem," recognized by an RF guy working in pro audio in 1994.

MANY pieces of ham gear have metal enclosures that fail to make contact at junctions between parts of the enclosure, usually because they are insulated by paint. Such an enclosure FAILS as a shield. One of my Astron power supplies has this problem, and EVERY Astron I've opened fails to connect the power line green wire to the chassis, as required by virtually all Electrical Codes. Again, the problem is paint between the log where the green wire is soldered and the chassis. Not only that, but even worse, Astron bonds V- to that same lug! Talk about a recipe for RFI!

73, Jim K9YC
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