KD9SV / OK1RR
Front-End Saver

KD9SV Front End Saver
With OK1RR recommended 12V
PRMA Relays

 WY3A Homebrew Project
KD9SV Front End Saver

Manhattan Style

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 went "key-down". 

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 little planning. 

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.

IT WORKS

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, WY3A
West Chester, PA