XK X250 FPV Camera Antenna Repair

[kagaos]

Hi Guys!

I'm new here, but I stumbled upon this site while trying to search for answers to my FPV system problem.
I'm a newbie at electronics and circuits so I have no idea what I'm doing (I can solder is about it). Hopefully you guys can help out a dummy like me!

So here's the situation:

I have an XK X250 quadcopter with the stock FPV system and camera. It just so happens I had a nasty crash and somehow the antenna from the camera got ripped off. It is a 5.8g fpv system and that's about all I know haha

So I've attached some pictures as to what I'm working with. The second picture shows where, I believe, the antenna was attached. There are 3 points. I assume one is + one - and one N? I'm just curious how to fix this. I've read that there are certain types/lengths/shapes of wire that varies with each application...and I have no idea where to start.

As of now, the FPV gets a range of about 25' before cutting out.

Thanks in advance!

 

[73's de Edd]

Sir kagaos . . . . . . .

Soooooo . . .it looks like the right top black "stub" antenna is what your missing and looked like.

Probably only available from the factory.

Looks like the two end board solder connections are symmetrical ( interchangeable) and the center is being being a common ground for its wire in..



73's de Edd

 

[KJ6EAD]

Looks like the two end board solder connections are symmetrical ( interchangeable) and the center is being being a common ground for its wire in.

It's also possible that it uses an amplified antenna where the connections would be power, ground/shield and signal.

 

[73's de Edd]

Sir kagaos. . . . . . .

In further exploring . . . .

If it is using an amplified antenna . . .then they would want full Vcc power to it.
Look at the very bottom of the board with its white micro Sipex connector and to its right is the main Vcc electrolytic filter capacitor . . .with its + terminal being designated on the PCB.
Take an ohmmeter . . . low scale . . . .and in a no power connected condition, see if that caps + lead connects to any of the three "vacant wire" solder lands in the antenna wiring connect area..

Next . . . . . at the right top corner of the PCB, all of that edge real estate is being a foil ground plane.
Either pierce thru the green resist to make connection with one probe or use the top terminal of that corners brown monolithic ceramic block capacitor for your ground connection and check to see which of the three "vacant wire" solder lands might be grounded.


73's de Edd

 

[kagaos]

.


Sir kagaos . . . . . . .

Soooooo . . .it looks like the right top black "stub" antenna is what your missing and looked like.

Probably only available from the factory.

Looks like the two end board solder connections are symmetrical ( interchangeable) and the center is being being a common ground for its wire in..



73's de Edd



.

Thanks for the reply!

It sounds like you're saying it's a part that I would have to buy directly from the manufacturer. Is that correct?
Otherwise, do you think it is possible to re-make this antenna? Also, perhaps I wasn't clear, I do not have the original antenna that fell off the camera. I lost it when it crashed. So I was hoping to "home-make" one.

If I can home-make one, what's your guess as to how is it wired? (again, I know very little about this, I apologize)
Do I simply solder a wire on each of the 3 contact points and if so, what do I do with the other ends of the wires I attached?

 

[kagaos]

Sir kagaos. . . . . . .

In further exploring . . . .

If it is using an amplified antenna . . .then they would want full Vcc power to it.
Look at the very bottom of the board with its white micro Sipex connector and to its right is the main Vcc electrolytic filter capacitor . . .with its + terminal being designated on the PCB.
Take an ohmmeter . . . low scale . . . .and in a no power connected condition, see if that caps + lead connects to any of the three "vacant wire" solder lands in the antenna wiring connect area..

Next . . . . . at the right top corner of the PCB, all of that edge real estate is being a foil ground plane.
Either pierce thru the green resist to make connection with one probe or use the top terminal of that corners brown monolithic ceramic block capacitor for your ground connection and check to see which of the three "vacant wire" solder lands might be grounded.


73's de Edd

OK I will look into that after I get back home today. You can bet I'll have a ton of dumb questions haha

Thanks!

 

[73's de Edd]

.

Oh tayyy !

Pull out ye olde tyme ohmmeter and find out about those 3 solder connections that I asked about.
I am really expecting a ground to the left connection, a center RF connection and then another ground connection to the right.
And yes . . . . I can fill you in on a "custom hand engineered " three dollah and 'lebenteen cents parts cost replacement.

 

[kagaos]

Haha Edd, you're a funny bean!

OK. As far as I can tell, there is some connection between the right lead and the + for that capacitor. I am really not sure what I am doing (especially with multi-meter) or if I'm doing it anywhere near correctly. But I put the multi-meter on the setting in the attached picture and when I tested between the +lead on the PCB and the right-most lead the meter read 2.95. I am not sure what that means, but the other 2 leads did not result in a reading from the meter.

I attached pictures of what I was doing. Please let me know if I am testing the wrong leads or if I am just plain ol' am not understanding haha.

Next . . . . . at the right top corner of the PCB, all of that edge real estate is being a foil ground plane.
Either pierce thru the green resist to make connection with one probe or use the top terminal of that corners brown monolithic ceramic block capacitor for your ground connection and check to see which of the three "vacant wire" solder lands might be grounded.

I'll be honest here and say I'm not sure exactly what you're asking me to do. Perhaps you could use my image to point out where I need to probe? I understand we want to find out which land is grounded but I can't say I understand the procedure to do so.

Thanks for your help, time, patience, and understanding!

 

[kagaos]

Any updates?

 

[kagaos]

Anyone?

 

[73's de Edd]

.


Sir kagaos . . . . . . .

Ahhhhhhhh Sooooooo . . . . .Most honnable apologies . . . .I be velly velly bizzy lately.

Saw your third from last post and see that the ohmmeter testing would have had two errors.
The BLACK probe lead needs to be moved from the 10 AMPS input jack over to the extreme right to the COM input.
Then the functionii selectamus knobbae needs to be dropped down two clicks to the 200 ohms range.
Open probes should give a reading similar to what is now shown.
Short the probes together and note the change in the reading in trying to display a very low ohms reading.
BUT . . . .this is of no consequence now, after I went back and got your post 1 photo and magged it up.

Using my photo referencing, you can compare what you had left clinging to your PCB end, as compared to what it would have been initially.

Since I am blind-deaf-dumb-senile at this end, how about there being any possible communication between this cameras transmitted signal and your control unit display .
Specifically, is there any any chance that the receiver display gives you received signal strength ?
Or do you just have to experience video drop out ?
If not, lets just play it this way:
Take well tinned soldering iron in hand and clean the coax remnant wire strands from A B C and then solder a rigid length of hook up wire to B.
Clip the extended wire length down to that 13 mm wavelength.
Either fire up both units and either walk off with the control unit to see what range is attained before video drop out or do a test flight in a safe area.
I would expect about 1000 ft range with that temporary test antenna stub.

If all is well, then get a piece of RG316 coax and initially work on the PCB end where you take a sewing needle and unbraid the shield.
Then divide the straightened wire strands into right and left portions and twist and form them into the shown
" quasi Trident" for making the 3 connections.
On the radiating end of the antenna , ever so slightly use a single edge razor blade to cut a ring around the clear plastic insulation covering , but not damaging the shield.
Then the same earlier procedure for unbraiding the coax from its end, up to that circle. A pair of fingernail clippers will do one fine job in evenly trimming that wire around the circle.
When all is in order, trim that stub to 13 mm.
I leave the ~3/8 inch dia plastic "bullet" up to your ingenuity in fabricating. . . .be it multi layering buildup or formed and then cut into halves to re-bond together or a 2 part epoxy putty to mold into shape..

If you are not in the "bidness" you can get RG-316 micro coax from:

All of e-bays listing . . . . . .with long delivery waits if using OVERSEAS HK or China suppliers

http://www.ebay.com/sch/i.html?_from=R40&_trksid=p2050601.m570.l1313.TR0.TRC0.H0.XRG-316+coaxial+cable.TRS0&_nkw=RG-316+coaxial+cable&_sacat=0

Or get a new surplus cable and cut off a connector to make one antenna PLUS 13 additional ones. This comes from a STATESIDE suppler . . . . . . . or check for others pricing.

http://www.ebay.com/itm/NEW-RG316-RF-FLEXIBLE-COAXIAL-CABLE-TNC-MALE-TO-SMA-MALE-4-FT-FREE-SHIP-/330305698907?hash=item4ce7c0fc5b:g:s1cAAOSwo0JWIB7G



NOWHOWTODOITTOIT:

( Clickee-clickee . . . it makee biggie- biggie )

CLARIFICATION. . . . ( "bare" meaning the insulated center wires UN-shielded length )

Thassssit . . . . .


73's de Edd


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