Jump to content
Hogster

Using the correct capacitor value?

Recommended Posts

The absolute minimum for good sync fidelity is a high quality 330uF. If you have some average-bear 220uF electrolytics, then put two in parallel.

The values can be higher than 470uF (1000uF is commonly sold). Plus, the working voltage can be as low as 6V.

Share this post


Link to post
Share on other sites

I've got (what seems) a high quality 470µF 50V cap and 35v cap but as they're quite sizey I was wondering if I could get away with something smaller ... evidently not. :)

What's this bypass capacitor for anyway, do you know?

Thanks very much :)

David

Share this post


Link to post
Share on other sites
What's this bypass capacitor for anyway, do you know?

Technically speaking, it's not a "bypass" cap application. Instead, it removes the DC bias to/from the video source (A/C coupling).

Some board cameras have this cap (or a tricky electronic equiv) already added to their video output signal. So sometimes you can cheat and not use one on the Airwave Tx module. And on the flip side, some video monitors have it on their Vid-Input, so you sometimes can leave it off the Airwave Rx. But overall, it is a krap shoot, so it is generally safest to assume the worse and install the cap per the Airwave data sheets.

FWIW, in the video industry their are some inconsistencies with use of AC coupled video. Some products don't play nice with it and instead need DC coupling (no cap on the video signal). This can really screws things up with users that have a mix of video devices to plug in. However, in the case of the Airwave module (and nearly ALL other video devices), A/C coupled video is expected and offers the most compatibility.

Share this post


Link to post
Share on other sites

I think we might not be talking about the same cap here ... I'm referring to the 470µF 16V cap shown at the top right of the schematic diagram on the 3rd page of that PDF - capacitor 'C3'. I've already got the correct capacitor for the video output, C6 (470µF 10V - only had one of them though!).

Or is this 'bypass' capacitor something to do with the video output?

Many thanks,

David

Edited by Hogster

Share this post


Link to post
Share on other sites

Sorry, I didn't realize you meant C3. You are correct, it is the bypass cap for the RF amp. I've always used the recommended value. So, I have no idea what problems you will run into if you cheat it. These sort of things usually end up as a YMMV thing when you detour from the recommendations.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×