Jump to content
Sign in to follow this  
ThomasScherrer

RSSI inside this RX unit ?

Recommended Posts

Hi I purchased the 2.4ghz 500mw tx/rx set,TD240500TXRX from blackwidow

anyone know if there is an RSSI signal available inside the box ?

I think it could be cool to purchase another similar unit,

and make a real fast video switch that always send out the strongest signals.

If I use the sync fail check mentioned on other pages, it will not be as perfect since errors needs to be seen before switching, so I prefer the RSSI methode.

on this page I have pictures of the inside of this RX box Im talking about.

http://www.webx.dk/rc/video-wireless/video.htm

anyone ?

Share this post


Link to post
Share on other sites

Thanks you are my hero !

Signal level out at pin 9 nice to have such a good data sheet avail.

what kind of good fast video switch would you recommend ?

I have seen 4066 used, but dont think they are good with color burst and hi resolution, not that fast ? also the internal resistance is a bit too hi.

what about this:

ADG712 CMOS Low Voltage 2.5 Ω Quad SPST Switch

Edited by ThomasScherrer

Share this post


Link to post
Share on other sites

MAX4311. Dont' forget you'll need to analyze sync too if you want the switching not to be noticeable.

Share this post


Link to post
Share on other sites

why wait for sync ?

if the other RSSI is stronger, I wanted to switch to that one right away.

if both video levels are at the exact same level,

it should be fine to switch 100 times pr line ?

you mean line sync ? not picture start sync ?

Share this post


Link to post
Share on other sites

It's true if your switch is fast enough it will be OK. But the transient might be seen if switching is done in the middle of a line. I'd do it in blanking periods.

As the RSSI method can mean many switches even if both video signals are perfect, it would be nasty to see some spikes here and there.

Share this post


Link to post
Share on other sites

I have to agree with this, if during a horizontal sweep the currently selected receiver drops out, I see no advantage in waiting for the next sync (H or V) to switch.

Of course, some hysteresis is required, and there is no point switching receivers when they both have a signal strong enough to produce a decent image.

There is one 'gotcha' in this. The switch is fairly transparent if it is extremely fast, and if both receivers have identical gains (and have similar frequency responses), but when they aren't, the switch can be quite visible.

Share this post


Link to post
Share on other sites
It's true if your switch is fast enough it will be OK. But the transient might be seen if switching is done in the middle of a line. I'd do it in blanking periods.

As the RSSI method can mean many switches even if both video signals are perfect, it would be nasty to see some spikes here and there.

Personally I haven't seen glitching when switching receivers, even mid-line.

To reduce switching when both signals are perfect, a simple threshold, above which you don't switch regardless of relative signal strength, resolves the problem.

Share this post


Link to post
Share on other sites

thanks for your inputs,

I dont see any difference in switching pixel to pixel,

compared to line to line, if the video signals have different levels

the same problems will happen.

ok the switch on/off delay is much more critical on the pixel switching,

but comparing to dropout problems :-)

it is only a matter of sw to change it later.

I want to use the same rx type on both inputs,

and have a trimmer on the DC level and gain so I can adjust them to be perfect both on black and white signals, I will also add a OSD chip, to indicate A or B antenna and RSSI levels, just made as small as possible.

Share this post


Link to post
Share on other sites

Hehe, thats the same receiver that is inside BWAVs diversity receiver and that same receiver can from comtech has been the industry standard 2.4ghz video receiver for at least the last 4 years.

Matt

Share this post


Link to post
Share on other sites

what is the uptimal antenna distance ? angle and types,

when used in diversity systems ?

I think something about halves wavelength distange,

both could be patches, but also whips one pointhing up the other to the side,

and not the same angle to plane, and not same height to ground, right ?

Share this post


Link to post
Share on other sites
what is the uptimal antenna distance ? angle and types,

when used in diversity systems ?

I think something about halves wavelength distange,

both could be patches, but also whips one pointhing up the other to the side,

and not the same angle to plane, and not same height to ground, right ?

I wouldn´t use a whips for a diversity receiver, a nice patch like GP Patch, or CP Patch and some other more directive for some long distance flights would be great.

By the way, last sunday I placed on my plane a 5dbi omni with sma conector and there is a significant improvement over the 3dbi omni in all the ways, even in turns. The only weakest point of it is when you flight over the receiver, then the 3 dbi is better.

Share this post


Link to post
Share on other sites
By the way, last sunday I placed on my plane a 5dbi omni with sma conector and there is a significant improvement over the 3dbi omni in all the ways, even in turns. The only weakest point of it is when you flight over the receiver, then the 3 dbi is better.

As you would expect, the only other down side would be if you are near buildings and then you may suffer worse multipath or local interference.

Terry

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
Sign in to follow this  

×