KD9SV / OK1RR
KD9SV Front End Saver
With OK1RR recommended 12V
My diode-based RF Limiter / Receiver Front End Protector was good, but under
certain conditions, simply wasn't cutting it. My TX and RX
antennas are just too close to each other --
on some bands my K3 would "click" from excessive RF getting to
the receive antenna port.
I decided to build an active device,
using the KD9SV Front-End Saver as
revised by OK1RR, which would ground the RX antenna whenever the TX
I found an old, small
5-Port Ethernet Switch which had a nice metal chassis...just about the
right size. I cut 3 rectangles of copper clad board and scribed
lines with a hobby knife to create 8 properly spaced solder
"islands". Glued them to main board. First, a
Add in the (2) 2N222A transistors
and 4.7 K resistors Manhattan Style
Make a backplane, solder it to the
main board, add the connectors and other wiring.
Create labels in Word, print on
plain paper, add masking tape to back and clear tape to front.
Glue in place. My hands...not very steady with the scissors.
The Front End Saver is
a money saver too. Compared to prices for the
commercial unit, this homebrew version
cost me 3 X $1.45 for the relays (Mouser
8L01-12-001) and not much more for the connectors (very
cheap from overseas vendors on eBay).
You can get 3 lbs of all
double-sided copper clad laminate
(for me a life-time supply) for something like $8 from
this eBay seller.
Bill Patton, WY3AWest Chester, PA