[hpsdr] ALEX - Input protection

[k3bu at optonline.net]

> Would it be posable to design the ALEX so that at least one inductor is
> on the antenna side of any device that needs protection.  An inductor
> would filter out any fast raise time in the impulse and store it's
> energy
> which then can be dissipated more slowly.  In other words a low pass
> filter is already designed to shunt high frequency energy to ground



>>Might be a problem getting the right impedance versus current handling on
the low bands. It was not unknown for front end coils to blow in AR88`s and
HRO's due to static even with their battleship dimensions.
Shel CT1IZU
<<
 
Probably the best combination of protection for the front end is to use the RF choke across the antenna input to the RX with small light bulb as a fuse in series with antenna connector and input to the RX (choke). This will provide the DC path to ground for any static buildup from LW antennas and the fuse bulb will blow under excessive current from the "next door" antenna's RF or lightning discharge. 
This was used in vintage FT100 and other radios.

Personally, I prefer using monoband antennas with "bazooka" quarter wave coax baluns that serve as a balun, band filter and DC ground at the feedpoint, while giving broader bandwidth for the antenna tuning.

Yuri, K3BU.us
 
  
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.openhpsdr.org/pipermail/hpsdr-openhpsdr.org/attachments/20070808/69bb32d6/attachment-0004.htm>