Jump to content
spagoziak

900 mhz Tx or Rx Problem... can't tell

Recommended Posts

Hey folks,

I've had a rangevideo receiver & transmitter (both no longer for sale on the site) for just about a year, and have used both some but always been very careful to keep them dry and protected from trouble.

Everything worked great yesterday....

But today when I turned it all on to show a friend, all I could get on my feed was garbage! Later at home with some poking around, it seems that something has happened to whatever thing handles the channel separation inside the RX. All RV units ship to work on channel 1 (910mhz), and that's what has worked over the last year.. except today, I could only get garbage on 1 and parts of a picture on channel 2 (980mhz).

If I use my patch antenna and keep the tx within 4 feet, I can get an ok picture, with some artifacts. The whip needs to be much closer. Compare this to a few days before, when I was out 2500 feet without issues...

Incidentally, the separators on that channel switch feel pretty weak, like the little cams that lock it into each position have given up a bit. Which is interesting because I've never really moved them more than twice, ever.

Here's video of some bad radio:

http://www.youtube.com/watch?v=lH8V4ZQoWtM

Here's what it looked like before this mess (for this, a direct cable connection is used):

http://www.youtube.com/watch?v=NSKkQmmS_zE

The $65 + shipping RV is asking for the only receiver they carry now is way out of my budget, unless I get rid of my plans for the tricopter, which would be quite unfortunate. :(

I'm pretty handy with a soldering iron... or if it's not fixable, can anyone suggest a new RX that works with my existing patch & 900mhz TX?

I should mention that I've tried powering the vRx with two separate 3S lipos (both full) and a 12v 500ma wall adaptor. The vTX rig has been powered through a 3S and an 800ma wall adaptor. Directly connecting the rig to the recorder reveals a perfect picture. I've tried a normal whip & a +3dbi on the vtx & receiver. Also a patch on the Rx. The videos are shot with my last known working configuration, a +3 on the vtx and the patch on the vrx. The units were are about 5 feet apart during the videos (uploading now).

Thanks folks,

spag

Share this post


Link to post
Share on other sites

Need a bit more information.

Which Tx model is it? It would be best to post a link to a catalog page that fully describes it.

What are you using for the Tx antenna? If you bought it then post a link. If you built it then post a photo and describe the construction details.

Lastly, do NOT use a common 12V wall adapter. I've lost count how many times I've helped someone solve a wireless video system problem that was caused by the poor regulation in those things. To ensure less frustration during your tests, charge your batteries and use them instead.

Share this post


Link to post
Share on other sites

Indeed, the wall regs are flaky at best. I only mentioned them to illustrate that I've tried multiple sources of power.

Rangevideo.com no longer hosts the page that describes the tx/rx I bought. The only model they have on their site is this one, which is not similar to what I'm using. However, DPCAV does carry what appears to be a model identical to what I'm using, shown here. This seems to be the best match to an equivalent transmitter.

For antennas, I always use the +8dbi patch antenna from Rangevideo on the receiver. The transmitter always uses the +3dbi dipole from same.

Share this post


Link to post
Share on other sites

I'm not sure which Tx / Rx you have, but if it is the same as the DPCAV TX9-500, and the Rx you have is exactly the same as the RX900-STD Rx, then I don't know of any bad habits on those products.

But be careful; a lot of this stuff looks identical but is not at all the same. BTW, if you have the 900MHz 200mW Tx that was sold by some FPV shops then that is a quirky unstable design. It can do odd things depending on the antenna that is used. For sure, if that is what you have then my best advise is to replace it with the 500mW model.

Share this post


Link to post
Share on other sites

I'm not sure which Tx / Rx you have, but if it is the same as the DPCAV TX9-500, and the Rx you have is exactly the same as the RX900-STD Rx, then I don't know of any bad habits on those products.

But be careful; a lot of this stuff looks identical but is not at all the same. BTW, if you have the 900MHz 200mW Tx that was sold by some FPV shops then that is a quirky unstable design. It can do odd things depending on the antenna that is used. For sure, if that is what you have then my best advise is to replace it with the 500mW model.

Mine is 500mw, so I'm safe there. I haven't heard of anything weird from either of these bits... the ones on RV were reviewed well. It's a shame their pages are off the site now so I can't refer to them. I've not heard back from any staff at RV either.

Share this post


Link to post
Share on other sites

FWIW, the symptom suggests a hardware issue, not a bad Tx/Rx adjustment. So don't start turning any pots or inductors or you will certainly Charlie Sheen your system.

Unfortunately, the problem could be the Tx, Rx, or something else. From my experience the usual FPV'er immediately blames the Tx as being the problem for such things. However, if the Tx is the same as the one sold at DPCAV then I can say from experience that it is rarely the source of problems (but of course it could be bad).

So start at ground zero; check and recheck everything, even the things you know it cannot be. This includes cables, connectors, battery voltages, and so on. If that gets you nowhere then maybe you can do a shout-out to fellow FPV'ers in your area and get together with their 900MHz system to isolate the problem.

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

×