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Terrible range on Gremlin with dipole antenna

#1
After a fair amount of frustration with the build, I just finished building a Gremlin, which came with a FX805 camera and VTX combo with a dipole antenna. I also bought the FXT Viper goggles. Everything works, except that my video range is terrible. I thought maybe this was a result of the dipole antenna on the VTX, but there are numerous videos on the internet where people are flying the same quad with a dipole antenna and getting MUCH better range than I'm getting.

I'm trying to figure out what the problem is. Should I replace the antenna on the VTX with a circular polarized one? That seems to be possible. Should I upgrade the antennas on the goggles? I'm currently using just the stock dipoles, but I'm not sure what I'd upgrade to.

Any suggestions would be appreciated.

Thanks.
 

cranialrectosis

Well-Known Member
Mentor
#2
Antennas come as SMA and RP-SMA connection types.

The difference being how the little stinger in the center seats in the female connector. It is possible to connect two females if you mix the two.

The result being VERY short range.

Are you mixing SMA and RP-SMA gear?
 

cranialrectosis

Well-Known Member
Mentor
#4
Are you using the antennas that came with the goggles on your VTX?

If so, look HARD at the connection or post a well lit photo here were we can see the connectors.
 
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PsyBorg

Wake up! Time to fly!
#5
Those combos are garbage. They are a freakin nightmare.

Get rid of it and go with eachine atx03 and a run cam micro.

Look in my Gremlin thread if you wanna see the video night mares them combos are. There is also videos of each evolution til I settled on the atx03 / runcam set up.

Running the gremlin on 50 or 100mw with beautiful camera settings makes all the difference in the world and has been hassle free since tge switch.
 
#8
Does your VTX get HOT?
It gets warm, but not so hot as to be untouchable or anything.

Look in my Gremlin thread if you wanna see the video night mares them combos are. There is also videos of each evolution til I settled on the atx03 / runcam set up.
Will do. Thanks so much for the input. I ended up ordering a combo camera VTX with switchable power up to 200mw from Amazon for $15. We'll see if that improves anything. Maybe I'll end up exactly where you are, but $15 seemed like it was worth it to see if I can keep from adding too much weight.

Are you using the antennas that came with the goggles on your VTX?
I'm using the antennas that came with the goggles on the goggles. As you point out later, the antenna on the VTX is soldered on.
 

cranialrectosis

Well-Known Member
Mentor
#9
I think what is happening is you are running a right hand polarized antenna off the VTX and an un-polarized receiver antenna off your goggles.

Polarization is used to help isolate the signal and I suspect your receiving antenna is not able to receive the full right hand polarized signal from your VTX antenna.

This is speculation on my part as I have never tried this and RF isn't my bailiwick.

I would try a right hand polarized SMA antenna on the goggles and see if that doesn't help.
 
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ElectriSean

Eternal Student
Mentor
#10
I think what is happening is you are running a right hand polarized antenna off the VTX and an un-polarized receiver antenna off your goggles.

Polarization is used to help isolate the signal and I suspect your receiving antenna is not able to receive the right hand polarized signal from your VTX antenna.

This is speculation on my part as I have never tried this and RF isn't my bailiwick.

I would try a right hand polarized SMA antenna on the goggles and see if that doesn't help.
He's using a linear (dipole) on his goggles as well as on the VTx, which is optimal as long as they are both either vertical or horizontal. Obviously a quad is banking and pitching, so rarely perfect, but should be usable. To make this setup optimal the 2 antennas on the goggles should be at 90 degrees to each other to minimize cross polarization. Circular polarization just aids in removing multipathing, which is where reflected signals arrive at a different time than the original and cause interference. Having a CP on one end and a linear on the other will cost about 3dB, which isn't a huge deal but will make this bad situation even worse :)

I second Bills suggestion of an ATX03 and Runcam micro - I run this combo on my 2" Eclair and it is amazing even at 25mW. Both my micro quads run dipoles mainly for weight saving and durability. Any of the light CP antennas are very fragile and if soldered to the VTx risk damaging the board in a crash.
 

PsyBorg

Wake up! Time to fly!
#12
The combos are garbage. Some have better electronic components then others but the All have one fatal flaw.

That little stub of pcb that sticks up above the camera where the antenna is soldered. That tab breaks if you look at it cross eyed.

After all I went thru with the gremlin and breaking cp antennas on gates I went to dipole on the quads and what ever miss matched antennas happen to be in the bag when I grab my goggles.

Back yard flying 50 mw on tbe gremlin is plenty. 200 mw on everything else and I have not had a problem since the switch.

I run one stock dipole and an aomway cp most times. I have been running a patch instead last few weeks as all my cp'sare now 3 leaf not four. Zero issues no mstter what direction the quad faces.

Granted I dont go super far. But I only fly as far as my body is willing to walk to get the quad if it crashes that day. Pretty much a couple of foioball fields is plenty of room for me to fly.