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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