Dennis Frie

- a couple of projects and pictures


(2011) Scherrer UHF supply measurements

I have been flying FPV with 35 mhz RC-link for quite a while, but finally decided to buy an UHF system for RC-link. Mainly to have a more safe RC-link and be sure not to loose signal if another turned on his 35 mhz remote-control at the same channel.

Unfortunatly I had a few problems with the supply-voltage being pretty unstable compared to my old Corona receiver.

This is my old Corona (RP6D1) receiver with 2 servos moving and no ekstra capacitor:

Can not show picture

- and this was the result I was getting using Scherrer NR recevier.

Can not show picture

My old Corona worked without extra caps - but to be sure the ripple wouldn't cause problems I have been using a small standard 1000 uF capacitor. Just to be sure. The Scherrer NR receiver went into fail-safe for a couple of seconds, 1 second with a few servo clicks and fail-safe again. Adding the 1000 uF capacitor used on the Corona resulted in this:

Can not show picture

The result was a lot better, but unfortunatly I still experienced a few fail-safes and the movement wasn't very smooth.

Assing another 1500 uF cap gave this result:

Can not show picture

This solved the "fail-safe" issue, but I still experienced a little delay and not perfectly smooth servo-movement.

Instead I tried to use a little 330 uF low ESR capacitor, with this result:

Can not show picture

Even though this cap is only 1/3 the value of the 1000 uF capacitor, and the fact that it looked a bit worse on the scope, it actually removed all fail-safes etc. alone. Not perfect and smooth movements, but it did work.
Last test was with the low ESR cap and a big normal 1500 uF cap.

Can not show picture

I have later used 2 x 1500 uF low noise ESR capacitors and haven't had any problems :)