Modern 2.4GHz Tx/Rx systems - couple questions

[Evil Jim]

Good day, all -

Given the paradigm shift in radio systems since the 80s, I have questions about certain aspects WRT installation.

First and foremost, what's the deal with the antenna(s)? I've seen all manner of placement within various machines...none, stubby, familiar (vaguely, but still shorter), doubles...and most of it is quite different from the old AM/FM days of, "Get as much wire outside the car as you can...and as high as possible!"

Does it matter at all? I can see where crawlers could probably care less (no meaningful rig/driver separation), while speed runners will want maximum range/signal, out on the tarmac and runways.

Second concern is keeping the Rx protected from water intrusion. I'm still getting used to seeing crawlers and bashers running through puddles and creeks, but it seems the Rx is rarely a listed waterproof component...unsurprisingly. For anything new, pretty much every kit/RTR comes with some sort of box, minus some race machines.

What about dropping a modern Rx into a gold tub, or similar...what would folks recommend? And as an added wrinkle to this, what if you've got a really small Rx form factor? I decided to go with a RadioLink RC8X and the lowest channel (4ch) option is a Mini-Z size, naked board style...and it's absolutely minuscule. I think the ESC/servo plugs will dwarf the poor thing...it's almost as much plugs, as it is anything else.

Which is great for fitting it into the buggy, but not so much for finding a decent box to put it in, in the car. Aside from all the boxes (all parts, really...always hated that part) being so ridiculously car-specific, not just in mounting, but overall shape/size, too.

At a minimum, I can pop the Rx into a balloon and zip-tie it to something.
But that's...pretty lame.

EJ

 

[Tex Koder]

Good day, all -

Given the paradigm shift in radio systems since the 80s, I have questions about certain aspects WRT installation.

First and foremost, what's the deal with the antenna(s)? I've seen all manner of placement within various machines...none, stubby, familiar (vaguely, but still shorter), doubles...and most of it is quite different from the old AM/FM days of, "Get as much wire outside the car as you can...and as high as possible!"

Does it matter at all? I can see where crawlers could probably care less (no meaningful rig/driver separation), while speed runners will want maximum range/signal, out on the tarmac and runways.

Second concern is keeping the Rx protected from water intrusion. I'm still getting used to seeing crawlers and bashers running through puddles and creeks, but it seems the Rx is rarely a listed waterproof component...unsurprisingly. For anything new, pretty much every kit/RTR comes with some sort of box, minus some race machines.

What about dropping a modern Rx into a gold tub, or similar...what would folks recommend? And as an added wrinkle to this, what if you've got a really small Rx form factor? I decided to go with a RadioLink RC8X and the lowest channel (4ch) option is a Mini-Z size, naked board style...and it's absolutely minuscule. I think the ESC/servo plugs will dwarf the poor thing...it's almost as much plugs, as it is anything else.

View attachment 305801

Which is great for fitting it into the buggy, but not so much for finding a decent box to put it in, in the car. Aside from all the boxes (all parts, really...always hated that part) being so ridiculously car-specific, not just in mounting, but overall shape/size, too.

At a minimum, I can pop the Rx into a balloon and zip-tie it to something.
But that's...pretty lame.

EJ

The tiny twig of wire that you see at the end of the antenna is Where the magic happens.. so do NOT cut, bend or cover that portion of the antenna and you should be good.
(The grey portion is actually a coaxial cable.)

 

[Diem Turner]

Good day, all -

Given the paradigm shift in radio systems since the 80s, I have questions about certain aspects WRT installation.

First and foremost, what's the deal with the antenna(s)? I've seen all manner of placement within various machines...none, stubby, familiar (vaguely, but still shorter), doubles...and most of it is quite different from the old AM/FM days of, "Get as much wire outside the car as you can...and as high as possible!"

Does it matter at all? I can see where crawlers could probably care less (no meaningful rig/driver separation), while speed runners will want maximum range/signal, out on the tarmac and runways.

Second concern is keeping the Rx protected from water intrusion. I'm still getting used to seeing crawlers and bashers running through puddles and creeks, but it seems the Rx is rarely a listed waterproof component...unsurprisingly. For anything new, pretty much every kit/RTR comes with some sort of box, minus some race machines.

What about dropping a modern Rx into a gold tub, or similar...what would folks recommend? And as an added wrinkle to this, what if you've got a really small Rx form factor? I decided to go with a RadioLink RC8X and the lowest channel (4ch) option is a Mini-Z size, naked board style...and it's absolutely minuscule. I think the ESC/servo plugs will dwarf the poor thing...it's almost as much plugs, as it is anything else.

View attachment 305801

Which is great for fitting it into the buggy, but not so much for finding a decent box to put it in, in the car. Aside from all the boxes (all parts, really...always hated that part) being so ridiculously car-specific, not just in mounting, but overall shape/size, too.

At a minimum, I can pop the Rx into a balloon and zip-tie it to something.
But that's...pretty lame.

EJ

Hey there, yes the length of the antenna does make a difference, although how much it matters will depend entirely on the use case. The receivers with little stubby or no visible external antenna, are generally designed for track useage where you're never very far away from the vehicle. It has the added benefit of the antenna being protected in case of (inevitable) crashes.

Long antennas that you run up and out of the body will provide more range (all other things being equal). Dual antenna (diversity), as far as I know, was originally used on aircraft receivers and this provides some added redundancy to aid in signal strength.

As for the water resistance, the receivers themselves are not water resistant in any way, shape or form. I think this is fairly obvious from the big gaping holes in the case where you insert the plugs to your ESC, servo, etc. The water proofing comes entirely from the electronics box you house it in. For maximum water proofing, the box should have a rubber gasket for the lid and any openings should have some form of seal (none wil seal perfectly, how well will depend on the design).

Hope this helps

 

[Evil Jim]

Tex -

I had noticed that the new antenna were coaxial cable, rather than simple wire.

If only the (I assume, unshielded) length at the end is needed to match the system wavelength, is it possible to trim the overall length?

That is, as long as one makes sure to expose the same distance of core conductor when finished, of course.

EJ

 

[Diem Turner]

Tex -

I had noticed that the new antenna were coaxial cable, rather than simple wire.

If only the (I assume, unshielded) length at the end is needed to match the system wavelength, is it possible to trim the overall length?

That is, as long as one makes sure to expose the same distance of core conductor when finished, of course.

EJ

Correct. I believe the exposed bit at the end is quarter wavelength if I'm not mistaken. There's some minor variation among the manufacturers from what I've noticed so, just to ensure optimum operation, measure the length of the exposed end of an original antenna and just match it.

 

[Senton_Prime]

Don't do that..

 

[Diem Turner]

Don't do that..

Why not? As long as you uncork the same length at the tip, the overall length of the antenna will make no difference.

 

[Evil Jim]

Don't do that..

Why not? As long as you uncork the same length at the tip, the overall length of the antenna will make no difference.

Agreed. From my (admittedly limited) RF knowledge...if the "exposed" portion is key, then maintaining that should be enough.
But, this is also all new to me...so, just looking to learn.

For Senton Prime, same question...I'd like to hear what you know.

EJ

 

[Dan B.]

Yeah, but just for reference, what length does the exposed tip need to be for 2.4 GHz? I can’t recall and I’m too lazy to search it right now. Please respond in mm’s, not in those stupid SAE fraction things….

 

[Senton_Prime]

Why not? As long as you uncork the same length at the tip, the overall length of the antenna will make no difference.

Oh, I didn't know!?

I actually know nothing of the subject really, just always heard not too.. something about being tuned or matched to a certain frequency of said wavelength.. i.e. shorter antennas/higher frequencies, longer antennas/lower frequencies!?

But really I know nothing on the matter so I'm just here to learn!!

 

[rotauq]

31.23mm

https://oscarliang.com/repair-2-4ghz-antenna-rx/

 

[Bustedaw11]

At a minimum, I can pop the Rx into a balloon and zip-tie it to something.
But that's...pretty lame.

EJ

Hey, thats how we all used to do it! A lot of vehicles (nitro I know for sure) came with them either already in a balloon or they came with one in the parts bag so you could do it...... it was like mod 1 for nitro crap back in the day

 

[nino]

I run naked receivers in my crawlers... You just have to waterproof the board itself (conformal coating, nail polish, various things-in-a-can for that). Bam, submersible!

I usually try to leave the antenna upright and sticking out an inch or two from the rest of the chassis. But usually it doesn't matter for reasonable distances, I've had them zip tied to chassis rails, bunched up in receiver boxes, etc.

For rx placement in a box on my fast stuff, I stopped gluing them in. Just stick em in there and screw it closed, done. There's always some extra wire in there to keep them from flopping around.

 

[Evil Jim]

Hey, thats how we all used to do it! A lot of vehicles (nitro I know for sure) came with them either already in a balloon or they came with one in the parts bag so you could do it...... it was like mod 1 for nitro crap back in the day

Oh, I know...I was there.

Spring? I'm not even a fall chicken...

EJ

 

[Evil Jim]

I run naked receivers in my crawlers... You just have to waterproof the board itself (conformal coating, nail polish, various things-in-a-can for that). Bam, submersible!

I usually try to leave the antenna upright and sticking out an inch or two from the rest of the chassis. But usually it doesn't matter for reasonable distances, I've had them zip tied to chassis rails, bunched up in receiver boxes, etc.

For rx placement in a box on my fast stuff, I stopped gluing them in. Just stick em in there and screw it closed, done. There's always some extra wire in there to keep them from flopping around.

I suppose I could remove the shrink it comes with, to get the whole thing coated. Or maybe dip it, as-is. I know what we use to do conformal coat at work...not easy/cheap to get 'hold of. Sounds like folks have generally found success with what's available to consumers on the street?

So...above the chassis, but not necessarily beyond the body? That's definitely what I've seen, especially in the Scale rigs. I know there's concern about appearance there, but I'm mostly thinking about crashes and rollovers. Killed quite a few masts that way, BitD. (poop, carried spares...)

Sounds like you're not using gyros on your fast stuff, nino.

 

[morrjr71]

I keep my 2.4ghz antennas totally inside the body, and, with a couple of exceptions, I don't use antenna tubes. For my Radiolink R7FG receiver with two antennas, I keep one outside the receiver and the other curled up inside the receiver box. For those with a single antenna, I leave about two to three inches outside the receiver box and stuff the remainder inside. I have not had range issues doing it this way.

I don't submerge my vehicles in water, so I don't worry about conformal coating the receiver circuit board. Many receivers marked "waterproof" already come with conformal coating. Those that say "splash proof" (i.e. Castle) tend to not have conformal coating, and rely on the receiver box to keep them running in wet conditions.

I use Gorilla clear double-sided tape to mount my receivers in the receiver boxes. The receivers come out cleanly with no residue on either the receiver or the box if they ever have to be removed.

 

[SrC]

Good day, all -

Given the paradigm shift in radio systems since the 80s, I have questions about certain aspects WRT installation.

First and foremost, what's the deal with the antenna(s)? I've seen all manner of placement within various machines...none, stubby, familiar (vaguely, but still shorter), doubles...and most of it is quite different from the old AM/FM days of, "Get as much wire outside the car as you can...and as high as possible!"

Does it matter at all? I can see where crawlers could probably care less (no meaningful rig/driver separation), while speed runners will want maximum range/signal, out on the tarmac and runways.

Second concern is keeping the Rx protected from water intrusion. I'm still getting used to seeing crawlers and bashers running through puddles and creeks, but it seems the Rx is rarely a listed waterproof component...unsurprisingly. For anything new, pretty much every kit/RTR comes with some sort of box, minus some race machines.

What about dropping a modern Rx into a gold tub, or similar...what would folks recommend? And as an added wrinkle to this, what if you've got a really small Rx form factor? I decided to go with a RadioLink RC8X and the lowest channel (4ch) option is a Mini-Z size, naked board style...and it's absolutely minuscule. I think the ESC/servo plugs will dwarf the poor thing...it's almost as much plugs, as it is anything else.

View attachment 305801

Which is great for fitting it into the buggy, but not so much for finding a decent box to put it in, in the car. Aside from all the boxes (all parts, really...always hated that part) being so ridiculously car-specific, not just in mounting, but overall shape/size, too.

At a minimum, I can pop the Rx into a balloon and zip-tie it to something.
But that's...pretty lame.

EJ

Yeah the Balloon Trick was actually a Real RC thing. And still a smart move actually. Done that many times before. Cutting much of the neck off to install the Rx. Wires exiting and use a zip ties to seal it off. Many of my Vintage Nitro rigs as well. Nitro fuel ruins electrics. That was way before Rx boxes were even a "Thing" in RC platforms.
Most Rx's actually claim to be water resistant these days. I don't trust that personally. Some Rx boxes are not even sealed well to begin with. Having fried several when wet before. I use Water proofing Silcone Conformal Coating, brushed onto on the RX PCB boards for all My Crawlers which do see streams, snow storms, water and all, even though it's in the Rx box. Many of the Rx's are Conformal Coated at the factory. Open you Rx's up to see how well they did it if at all. I just add a coat more 99% of the time. Many are not WP or coated , even though they say it thge Rx is water proof. Look closely at what you have there.
I don't run any of my $6s$ bashers in the wet anymore. Just all my Crawlers with Brushed Setups. Brushed motors are cheap, have great Linear Throttling for crawling and are immune to Water for the most part. BLX motors not so much at all. And cost too much to let them get wet and trashed.
Crawlers don't need long range at all. We drive them near and close slowly. I use Antenna'less Rx's with them. Simple.
I normally use Antenna'ed Rx's in all my other rigs. I keep the antennas stretched outside of the Rx box , not bunched up, coiled inside of it. Us ean antenna tube, If the Stocker one is too short Buy long ones form Dubro. ANd extend the antenna all the way. Best, Noo glitching this way, Max range will be achieved this way. WIth the modern 2.5 ghz antennas, The last 20mm or so of the antenna is the ACTUAL Antenn itself. Keep it high and pinted stright up. Id running a double antenna setup, ( Best for Speed Running) Angle the 2 antenna "Tips" 90 degrees from each other for this type of Diversity Antenna design. Best reception results this way.
My spin.
Good luck.

 

[Evil Jim]

I use Antenna'less Rx's with them. Simple. I normally use Antenna'ed Rx's in all my other rigs.

SrC, are you buying receivers this way...either with, or without antenna? I've not seen any from RL without antenna.

It doesn't seem like simply removing one could work...it would have to be designed as internal from the start.

EJ

 

[SrC]

^^^
Yeah, I never saw any for the RL's. Only Flysky has one (sucked) and Spektrum's "Sport" $Rx$ has also no antenna. Designed for short range Track use. The Early Tactic Radio Rx's also had no antennas. With the early release boxed OE SCX10.2's They even had very decent antenna range ironically for bashing. My First 6s OC Arrma had that. And Range was impressive for some odd reason. Just that overall, the Radio was garbage, slow frame rates, felt disconnected with the model, hard to bash.
But honestly you could just spool some of the antenna up inside very loosely coiled up, and just leave the last 20mm or so dangle outside thru the Rx box pointed Up. And won't be in the way... for Crawler type short range use only. Antennas are delicate where exposed, and need to be in the tube/protected however long it is. How I fly.