[Icom] How to protect Rx Ant input?

[Larry Benko]

Effi,

I stand corrected.  A couple of other folks pointed out that I 
probably didn't appreciate HOW BIG the signal would be at the 
RX antenna input.  I made my comment in regards to the impression that
the RX antenna input was not protected when in fact it is protected.
It just is not protected well enough especially for high power.  The
diodes DS101 and DS102 clamp the voltage to 1.4V which means that the
lamp sees all the voltage.  The varistor R112 probably does not help 
as I believe that it clamps in the 50V range.  An external relay driven
from the send line or the send jack to the amplifier would have 9 to
10 msec. to operate before the RF starts.  There are several small
telecom type relays that operate in the 2 to 3 msec. range and have
DPDT contacts rated at 2 amps.  Aromat (NAIS) type DS2 are common
examples.

73,
Larry, W0QE



Ekki Plicht wrote:
> 
> Am Montag, 3. Juni 2002 03:02 schrieb Larry Benko:
> > Gee, looking at the schematic shows a Varistor(R112), a lamp (DS111),
> > and back to back diodes to ground (DS101, DS102).  This certainly
> > seems like protection of the RX Antenna port.
> [...]
> > What component(s) gave up when you had your problem before?
> 
> The lamp DS111.
> Sure, this is a nice protection of the more expensive components, but it is
> somewhat awkward to tell your qso partner that after each transmission you
> have to stop and repair the Rx input.
> Especially in a contest this is not exactly helpful for high qso rates.
> 
> 73,
> Ekki, DF4OR
> 
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