Ten Minute Transmitter On The Air with a Homebrew Antenna Switch

Why I need This

My Ten Minute Transmitter is just that--a transmitter. It is not a receiver. To get on the air, I have to:

• Connect to a suitable antenna
• Listen to any reply using a receiver or transceiver

Since I have few choices of antennas, my transmitter will need to share the same antenna as my receiver. (In this case, my receiver is a KX3). And to use the same antenna, I need a switch that opens the connection to my 40M antenna when I'm transmitting, then close the connection to the transmitter and open the connection between the 40M antenna and my receiver. 

Resources

An antenna switch doesn't sound that complicated. I wondered if I'd need to connect all the negative/shielding together. I used the following resources:

• https://swling.com/blog/tag/homebrew-antenna-switch/
• https://dailyantenna.blogspot.com/2019/02/building-manual-hf-antenna-switches.html
• https://pa0fri.home.xs4all.nl/Ant/ANTswitch/antswitcheng.htm
• https://www.g4ifb.com/html/homebrew.html#ManualAntennaSwitch

Information about capacitive voltage dividers are here https://www.basictables.com/electronics/capacitor/capacitive-voltage-divider In essence, I don't require a voltage divider since I'm not attempting to take readings through a scope.

The Build

I basically drilled holes on three sides of an Altoids tin for four very old BNC adapters that I scrounged from the garbage about 10 years ago. A SPST switch completed the fourth side. I used a short length of RG-8x coax to tie the hot terminals together. here's a picture:

The Result

The switch worked quite nicely after I remembered to use it! I called CQ several times. While nobody returned my call, I was spotted by Bob Delinger (KD7YZ) on the Reverse Beacon Network. (Bob is in Greenup County, Kentucky (Grid EM88ll) which is about 305mi distant. I registered a 5dB signal--not too bad since I'm putting out only about 360 mW).