Mode Zero

Hello guys ,you’ve seen this project before and I’m wanting to close it off as being finished . However I have a gremlin !
I have made a neat job of the installation of the Digispark and also a JR 35meg RF board.

All works but not perfectly. Upon coupling the antenna (screwing it on) it stops working. It seems like the RF is swamping everything and possibly the Digispark too.

Without the antenna it works , with it doesn’t and I get spurious twitching of the servos and my eyebrows!

I have moved the Digispark outboard in the last photo and still the problem persists. I wonder if I put ferrite rings on the Digispark leads if that would fix it ?

Now this is of course a metal cased transmitter and the RF board is from a plastic cased JR max TX. Should I be grounding the case to -VE ?

I have made a stiff metal linkage between the aerial connector bracket on the RF board and the Aerial base.

The aerial connection has been tested for continuity and does not short to the casing

Bit sunk at mo I’d like to go this project finished as lots more in the wings.

Thank you in advance guys

Jonathan

Outboard Digispark

Without seeing what that metal bracket leading from the rf out comprises it's a bit difficult to say but seems to short everything out.

It the big bracket from RF-out to the antenna base is just a connection I would replace it with a shielded wire and try again.

Frank

Hello Frank - yes that’s a good suggestion might give that a go

It is in fact a direct replacement for the aerial itself when the RF board was in the donor plastic cased TX

Bluejets
The rigid connection does not short to the case or touch anything.

It’s a good connection and provides rigid support for the RF board at the same time.

Further experiment revealed that the swamping of the Digispark does appear to be the problem as moving it away from the aerial link appears to improve the situation

Jonathan

In your original post you asked if the case should be connected to -ve. Yes, this is definitely a good idea! Just make sure there is nothing else connecting the case to any other part of the circuitry first! (+ve?) A simple continuity check between case and + and - leads should suffice.

RF pick up in encoders can be a real pain! The popular 5044 encoder i/c was particularly prone, and on 459MHz, I had to resort to a double sided board, with a continuous ground plane on the top, to cure it!

You might end up having to put the encoder inside a tin box enclosure if all else fails. The other alternative might be the Arduino encoder, which may be less susceptible.

Best of luck!

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Pete

Pete! Thank you very much for your suggestions - I will try everything to sort it.
It’s a nice transmitter and I want to go flying with it as soon as we are allowed .

I have some ferrite rings somewhere I might try those too