[Premium-Rx] Radios and High RF powers

[Larry Gadallah]

Hello all:

I've heard of schemes to deal with this that use some sort of conductive
conduit that is heavily bonded to earth and carries the coax into the
building. The idea is that the conduit forms a waveguide and the
transients travelling down the shield of the coax can't pass through it
based on the physical geometry of the conduit and the coax. The term I've
seen used is "waveguide beyond cutoff", which I think refers to the fact
that below (or above) a certain frequency (again, based on the geometry),
a waveguide will not propagate signals. This serves to attenuate or
eliminate the high-frequency transients travelling along the coax. Here's
a cheesy ASCII drawing of what it looks like:


             \_______ conduit __________/
---------------------------------------------------------
coax cable
---------------------------------------------------------
             /--+---- conduit -------+--\
                |                    |
                |                    |
               ground               ground


> George,
> My point was the center tap of the transformer is at ground so the whole
> antenna is at DC ground but the rise time
> is fast enough to generate a voltage greater than 10 KV across the
> network. I do have gas tubes at the RX. My best protection is to
> disconnect the antenna while not in use.
> My LPDA is also at DC ground but you still can generate high voltage
> across the coax.
>                                fc

-- 
Larry Gadallah             larry AT gadallah DOT com
Sammamish, WA         http://www.gadallah.com/~larry
0x7F5B 56F0 5F6A BDEC EEC6  C121 775D 0914 602E C49D