Monday, October 2, 2017

Kit: TinySWR - a truly small SWR indicator

Designed by a group of German hams (DF3OS, DJ6TE, DL9SCO and DK3IT), the TinySWR measures 0.6 X 0.8 inches square and was made to be installed inside of rigs like the KD1JV Sprints (in Altoids tins) and other super small QRP rigs.

The circuit board is available from OSH Park, a "community circuit board manufacturer". Barry N1EU has put together a list of the required parts, available here as an easy to order form from Mouser.

I no longer have my AT Sprint or MTR transceivers but this little circuit would easily fit into either of them and would provide the ability to trim or otherwise tune the antenna. Even with the popular PAR end-fed antennas that don't require a tuner, I never liked operating blindly, trusting that the SWR in a particular installation of the antenna was matched.

Confirmation of low SWR is always nice to have and the TinySWR would provide that.


Cloud Runner said...

I recently built one inside my MTR3 radio. It works PERFECTLY. I can easily and accurately see and tune my antennas while on SOTA outings. Thank you for making this informatiom readily available. - Fred KT5X (aka WS0TA) 500+ SOTA peak activations

John AE5X said...

Thanks for the info, Fred. Looking forward to working you again soon. 73 - John AE5X

Goathiker said...

Yes what Fred said ...TinySWR works great. Now installing in both MTR3/5s! Like an oil gauge in a car it's reassuring to know your engine is well lubed or not in danger of over heating! Likewise it's good to know your radio's PA is not about to go up in smoke because of high SWR!

Anonymous said...

Great project! I suggest that when you order boards and parts to get enough to build up 6 or more since you'll want to install them in all your tiny rigs.

JT aa1of said...

Did you evert try the solderpaste with hot air? Those embossing stick/guns are not that expensive.

Unknown said...

The easy order form list three different sets of three red LEDs
Would one set of 3 be best?

Cloud Runner said...

my experience has been they all work the same. get just one set of any of them. I use green for the first two, then a yellow, then a red. The green illuminates around 1.2:1, the yellow around 1.5:1, the red around 2.5:1. - Fred KT5X/WS0TA