The Southgate Amateur Radio Club - the amateur radio site for all radio hams  
www.southgatearc.org

 

 


The Amateur Radio Forum is the place to swop circuit designs and tips or to get help on a project

Switch-out SWR Bridge


For QRP work, a resistive (lossy -6dB) type that you switch out of circuit after use is the best. However I don't think these are made commercially! You sometimes see this simple circuit with QRP rigs and I suggest you get a local to build it, possibly a novice!

The circuit uses a double pole changeover switch (Measure or Operate), a SWR C/O switch Forward & Reverse, three 50 ohm resistors rated at 1/4 RF power, one RF diode (OA81), two 1nF capacitors, a series meter calibration variable resistor (10K) and a meter (100uA).

It is best to make it from an old CB meter as you get the Box, Meter SWR scale, sockets and switches. Sensitivity is down to about 0.2V of RF at the detector which is about 0.8mW. Depending on the layout and components used, the meter could be accurate to VHF.

circuit for swr bridge

 

73 De John, G8MNY @ GB7CIP


| Home | For Sale & Wanted | Tell a friend | Guestbook | Cast Your Vote | Newsboard | Amateur Radio Forum | Links | Diary Dates |
| Games | SWLs | 'How To' Guides | Humour |
Data Comms | Lottery | Amateur TV | Contests | Can You Help? | Contact Us | 10 Metres |
| Clubs Worldwide | Subscribe to our Newsletter |