Should a uhf rx be on the wing- or just the antenna?

[Billy_boy_2010]

hi guys

I have always placed my uhf rx on the end of a wing and have never had any signal issues.....

However- for my next wing I would quite like to have the rx in the main bay- and just route the rx's antenna out on the wing.

So- my question is-does UHF interference enter the rx only through the antenna, of through the actual rx module as well?

if it's the latter I will mount the whole thing on the wing as usual.

[mutley2]

I try to placed the RX in the fuz and keep the antenna close, coax is less than 400mm long, that said the antenna's are tuned on a VNA for my system. The Z3/Talon/Drak are all like this and will 20km+ without a problem.

[SnoozeDoggyDog]

hi guys

I have always placed my uhf rx on the end of a wing and have never had any signal issues.....

However- for my next wing I would quite like to have the rx in the main bay- and just route the rx's antenna out on the wing.

So- my question is-does UHF interference enter the rx only through the antenna, of through the actual rx module as well?

if it's the latter I will mount the whole thing on the wing as usual.

Hi Billy. I'm just building mine now with ezuhf 8ch lite. I'm putting the RX and antenna on the wing. I've ordered a Dipole for it from BN with a coax as short as possible. I can't offer RFI advice sorry. But my concern is the long ppm cable from the RX to the vector which will also run close to the wing servo cable.

P

[BlueFlyer]

I would always say it's better to run a PPM cable from a RX on the wing, compared to running a coax pigtail down the wing.

However, unless you're trying to break distance records then either way will be fine.

For years I've put the RX on the wing with a direct attach dipole on it, great results, never a glitch or failsafe and I've been around 5km with that.

On my most recent build however, I had my 4ch lite rx on top of the fuse of my mini talon, right in between the tail fins with the ESC just centimetres away on the side of the fuse (just under the right tail fin) and the motor a few inches to the rear. It only had a self built sander style monopole on it and I flew it to 8.3km yesterday... again, no problems at all I had full control the whole time.

On the transmitter side I was using a bignose13 JR Module dipole.

[Billy_boy_2010]

I try to placed the RX in the fuz and keep the antenna close, coax is less than 400mm long, that said the antenna's are tuned on a VNA for my system. The Z3/Talon/Drak are all like this and will 20km+ without a problem.

I'm confused- are you saying that provided the coax is less than 40cm long you have had no issues? I know you will lose some gain with a coax- but I don't think it's a huge amount?

But my concern is the long ppm cable from the RX to the vector which will also run close to the wing servo cable.

P

You can shield the PPM cable if you wish but this is really being fussy IMO. the servo won't be giving out much noise.

I would always say it's better to run a PPM cable from a RX on the wing, compared to running a coax pigtail down the wing.

However, unless you're trying to break distance records then either way will be fine.

For years I've put the RX on the wing with a direct attach dipole on it, great results, never a glitch or failsafe and I've been around 5km with that.

On my most recent build however, I had my 4ch lite rx on top of the fuse of my mini talon, right in between the tail fins with the ESC just centimetres away on the side of the fuse (just under the right tail fin) and the motor a few inches to the rear. It only had a self built sander style monopole on it and I flew it to 8.3km yesterday... again, no problems at all I had full control the whole time.

On the transmitter side I was using a bignose13 JR Module dipole.

I have always done this too- but wondering if I can get away with just routing the antenna this time. Having said that- you lose some gain with a cable vs none with a ppm servo lead. Plus the weight of the coax will probably outweigh the weight of the ezuhf rx on the wing tip.....

I would be really interested to see a list in order of what factors reduce interference the most

position of rx from noise
position of rx antenna from noise
ferrite ring on ppm cable
capacitor on ppm cable
shielding of ppm cable
grounding of ppm cable shield
esc noise
servo noise
board cam noise
hd cam noise

phew. The hassle and time it takes to control for all the above just isn't worth it.  But what offers the most effort vs reward would be interesting.

[BlueFlyer]

I use twisted servo wire for the PPM signal wire, it acts like a bit of shielding with the GND wire twisting around the other wires. Honestly a long PPM cable will give you no issues.

[Billy_boy_2010]

I use twisted servo wire for the PPM signal wire, it acts like a bit of shielding with the GND wire twisting around the other wires. Honestly a long PPM cable will give you no issues.

That's what I do too. And I twist servo wires.

[Coyote]

RX near the antenna is always best for maximising range. Although on 433 losses down good quality cables are minimum.

[SnoozeDoggyDog]

If the RX goes on the wing do you put weight on the opposite wing to equal things up (if not putting a vtx on the opposite) or do you just use extra trim?

Thanks
P

[BlueFlyer]

Definitely weight to balance.

[Billy_boy_2010]

RX near the antenna is always best for maximising range. Although on 433 losses down good quality cables are minimum.

Interesting- what about standard ebay cable?!

[Coyote]

There is no standard cable.  If it's RG316 then it's ok for Uhf

[FPVSteve]

Yea definitely a counterweight otherwise the trim will affect the plane at different speeds

[SnoozeDoggyDog]

Thx Steve.

[mutley2]

I'm confused- are you saying that provided the coax is less than 40cm long you have had no issues? I know you will lose some gain with a coax- but I don't think it's a huge amount?

Nope, what I was saying (not very well) is the Vtype and coax I use are all ex high GHz test leads made into an antenna, these have issues at much higher frequencies 30-40-50Ghz and cannot be used but are all good for what I use them for. These are no longer than 400mm, so my antenna's are never any longer than that.
Could I and would I use longer coax, yes I would but there is really no need, I don't use ebay RG316 and I don't use 90deg SMA connectors because I wont get the desired antenna "I" want, but they are still very serviceable for FPV.
As far as placing the antenna as far away from electronic FPV equipment goes like out on the wing, well that's down to your equipment and the noise levels at 433MHz. I like to house the RX inside the fuz and don't have an issues with the Talon out to 24Km+ (all over farm land away from towns etc). This is my Talon and it's placement of the antenna, RX, ESC and motor. All these components are with-in a 230mm length, no problems, no need to run ubber cables/antenna's out on a wing for me.
The black upright plastic tube is the 433MHz antenna, tis not right or wrong but just how I build, others build in a different way and are successful as well.  :thumbsup: