I found this advertisement, which is interesting.  Who knew?

Their might be an EMI filter that can go on top of an HT.  i think that's a 
lot of tork on a connector, but maybe they are small, since they would be 
working at high frequencies.

EMI Filter Supplier Distributor
EMI ( Electromagnetic Interference ) Filters
, also known as RFI (Radio Frequency Interference) Filters, basically are 
passive
electronic devices that are used to suppress conducted interference that is 
found
on a signal or power line. Electromagnetic Interference (EMI) is 
unacceptable electromagnetic
emissions, natural or man-made, which result in the degradation or 
malfunction of
electronic or electrical equipment. Radio Frequency Interference (RFI) is 
detrimental
electrical energy in the frequency range, which is for the specific 
transmitted radio
frequency. Major sources of EMI and RFI include microprocessors, switching 
power
supplies, AC motors, and electrical power cords (which basically act as an 
antenna).
As mentioned previously, an EMI Filter is a passive electronic device 
(comprised
of multiple components) for suppressing conducted interference found on any 
signal
or power line. An EMI Filter will suppress the interference created by other 
equipment
and the interference of the module or system itself, with the desired result 
being
improvement to the immunity from EMI signals in the surrounding setting. EMI 
Filters
can be found both in plastic as well as metal housings, in stand-alone, 
desktop or
module configurations.
An EMI Filter works by presenting a significantly higher resistance to 
higher frequency
content. In other words, the low pass design of the EMI Filter (the 
combination of
shunting capacitors and series inductors) results in the 
restriction/impeding of
the flow of high frequency signals, effectively shorting it to ground. The 
final
result of the EMI Filter is that it reduces and attenuates the unwanted 
signal strength,
thereby having a minimal effect on other components or devices. EMI Filters 
are gauged
by specifications including insertion loss, voltage rating, and current 
rating. In
addition, there are numerous approval authorities and specifications, 
including UL,
CSA, VDE and military specification.
There are a wide variety of EMI/RFI Filter applications, including (but not 
limited
to):
Energy Management Systems
Computers
Automatic Lighting
AM Radio Equipment
Factory Automation Equipment
Implantable Medical Devices (Cochlear Implants, Cardiac Pacemakers, etc.)
Military/Space Electronic Modules
Radio Controls
Telecommunications
Televisions and Monitors
Laboratory Equipment