Model Boat Mayhem
Technical, Techniques, Hints, and Tips => Radio Equipment => Topic started by: ronnie42 on March 17, 2022, 11:49:42 am
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Had an issue yesterday, radio starts telling me that connection to RX is lost/on at about 100m out . Think that i need to reposition the RX and support the aerial leads. Its a Radiomaster 16s and a Flysky RX.(https://i.imgur.com/HSyUr73.jpg) Must be interference from the electrics, as the aerial leads are hanging down, at shorter distances have no problems.
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As a simple check try rotating the aerial on the transmitter vertically upwards or downwards. The signal from the transmitter is basically polarised with in this case a horizontal polarisation. The receiver aerials are vertical so are not receiving the full strength of the signal. With these twin aerials it is best to have one vertical and one horizontal or both at 45 degrees with 90 degrees between them. this way at least one will in a better position relative to the transmitter. Also try and have the receiver aerials pointing upwards out of the hull.The actual receiver position should be OK, 2.4GHz sets are much less liable to being affected by other electronics than the older VHF sets.
Jim
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Remember its the tips of the aerials which are important. Get those above the water line and positioned as Jimg says. In your photo they are well below the water line.
Barrie
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Hi Ronnie42,Some guidance for you ...... it is clear from the photo that your antennas are very poorly positioned. As has been pointed out, it is only the the last circa 35mm that is the actual antennas, most of the length is a screened cable. Reposition the receiver so that one antenna is vertical and the other either horizontal or at 45 degrees. The way you have the antennas positioned currently they are close to being below the waterline. This is why it works when close to the TX but fails at a distance. Also locate the receiver away from other electronics (i.e. motor, ESC, etc) and clear of other wiring.Hope this helpsSteve Dean.
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Drilled a couple of holes in the superstructure to pass the aerials through , they are above the waterline and further away from the ESCs thanks again.
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I have seen operators all the way
from 27Mhz to 2.4Gigs pointing
the end of the antenna at the model
being controlled. The main signal is
from the sides of the antenna. The
end is basically a null point.
Antennae at right angles are great for
aircraft operating in 3D,not so much
for waterborne models.
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I've got a control line boat.... knit one, purl one, knit one, purl one.....! {-)
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I have a fishing rod and spinner that works, better than a rescue tug😎
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I hate to say but as you keep saying it's a wet boat there shouldn't be a need to put another 2 holes to the outside. Radio waves should go through plastic and wood just fine.
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It’s an OSV , people have had issues with the work deck , the superstructure is not a problem🤓
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AHTS maybe even.
I'd I were you I'd not be putting any unnecessary holes in anything but what do I know.
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Have the aerial leads been extended? If so why?
Regards Ian.
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Have the aerial leads been extended? If so why?
Regards Ian.
These are the standard length for FrSky receivers. Most 2.4GHz receivers have the actual aerial section at the end of a length of coax cable to allow for better positioning and reception. (The actual aerial at the end is just the exposed inner of the coax.) These radio sets are not generally designed for us model boaters but for use in aircraft where it is important to get the aerial ends away from any dense objects which may reduce signal strength. Some designs even use extra satellite receivers which can be mounted at a distance from the main one. Its generally only when you get to pistol grip type transmitters as used in card and RTR boats that the sets are specially designed.
Jim
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Constant learning curve O0 things obviously changed as early 2.4 gigglies receivers seemed to have only the grey lengths of wire shown as standard.
Regards Ian.
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Constant learning curve O0 things obviously changed as early 2.4 gigglies receivers seemed to have only the grey lengths of wire shown as standard.
Regards Ian.
The original Spectrum 2.4 GHz receivers just had a short length for the aerial and many of their receivers still do (some of the newer ones have no external aerial probably using a track on the circuit board.) Many of these rely on a separate satelite receiver mounted at a distance to give good reception. Most other manufacturers have gone to extending the aerial with coax to get it further away from the receiver and clear of any masses that would absorb the signal. Of course even with transmitters the stub aerial on most 2.4 sets is purely for show, the actual aerial is just a short length at the end of a length of coax cable. Many sets now just have the Tx aerial internal, often inside a carrying handle. Good transmitters now have two or more aerials internally to give a less directional spread of signals. (I have a Jeti transmitter with two 2.4GHz transmitting modules with 2 aerials each plus a 900MHz transmitter with 2 aerials, all fitted inside the case around the screen at the top. Obviously intended for the more expensive aircraft where the radio link is very important and would be a vast overkill for boats.)
Jim
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I have seen operators all the way
from 27Mhz to 2.4Gigs pointing
the end of the antenna at the model
being controlled. The main signal is
from the sides of the antenna. The
end is basically a null point.
Antennae at right angles are great for
aircraft operating in 3D,not so much
for waterborne models.
Agreed. I'm a mostly digital engineer but with decades exposure to rf designs. A dipole (straight) up antenna does indeed have a null at the tip - the radiation pattern is typically more 'doughnut', or like earths magnetic field
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As a simple check try rotating the aerial on the transmitter vertically upwards or downwards. The signal from the transmitter is basically polarised with in this case a horizontal polarisation. The receiver aerials are vertical so are not receiving the full strength of the signal. With these twin aerials it is best to have one vertical and one horizontal or both at 45 degrees with 90 degrees between them. this way at least one will in a better position relative to the transmitter. Also try and have the receiver aerials pointing upwards out of the hull.The actual receiver position should be OK, 2.4GHz sets are much less liable to being affected by other electronics than the older VHF sets.
Jim
I like the 45 degree idea.... gives me food for thought.
The thing about antennae is that longer isnt simply better - they have to be tuned to fraction/multiple of the wavelength (iirc a half-wave 2.4GhHz dipole is 12.7cm). I have a Spektrum receiver with a short stub and a longer but with summat active halfway down.
'Diversity' is also good, it's why wifi routers do/did have two antennae spaced suitably - if one is in the trough of the rf wave then the other is in the peak. As has been said - 90degree opposition is good for aircraft, but maybe less relevant to boats/cars
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Ah...... knew I had a photo somewhere.
My first 2.4 GHz RC outfit's instruction book went to great pains in describing how to install the receivers two aerials in model aircraft for best reception. Basically have them positioned at 90 degrees to each other.
As I like to be able install and remove RC gear quickly and easily in my models, a simple method was devised. Just taping the ends of the aerials to a triangular piece of cards would achieve this. The aerial card being placed above the waterline inside the wooden or plastic hulls that I use. I'll tempt fate and say that this method has never failed me.....
Glynn Guest
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Ah...... knew I had a photo somewhere.
My first 2.4 GHz RC outfit's instruction book went to great pains in describing how to install the receivers two aerials in model aircraft for best reception. Basically have them positioned at 90 degrees to each other.
As I like to be able install and remove RC gear quickly and easily in my models, a simple method was devised. Just taping the ends of the aerials to a triangular piece of cards would achieve this. The aerial card being placed above the waterline inside the wooden or plastic hulls that I use. I'll tempt fate and say that this method has never failed me.....
Glynn Guest
Nice (clean and simple) solution!! :-))
But I'd suggest the aspect of 'in model aircraft' - 3D.... For sure important when the receiver is at varying altitudes and horizontal orientations (banking etc). I'd contend though that a boat/car is not going through such aspect changes. If you're stood on the bank with upright Tx antenna, then the craft is always going to be best off also having upright antennae.
Maybe boats never get far enough away from us for this minutiae to matter :)
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Ah...... knew I had a photo somewhere.
My first 2.4 GHz RC outfit's instruction book went to great pains in describing how to install the receivers two aerials in model aircraft for best reception. Basically have them positioned at 90 degrees to each other.
As I like to be able install and remove RC gear quickly and easily in my models, a simple method was devised. Just taping the ends of the aerials to a triangular piece of cards would achieve this. The aerial card being placed above the waterline inside the wooden or plastic hulls that I use. I'll tempt fate and say that this method has never failed me.....
Glynn Guest
I get the vertical/horizontal orientation of the 2 antenna lead ends - surley it makes more sense to place them as far apart as possible.
If for some reason there is an obstruction/null area to the received signal rather than both antennas sitting side by side and both being in that null area you stand a chance of receiving a signal (regardless of polarisation) on the other remotely spaced antenna which may not be affected by the null area...
Agree that this is unlikely to be mission critical on a slow boat chugging around the boating lake - but I add the comment for completeness....
Regards
C-3PO _._
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Hummm... bit of confusion here methinks....
If you think about it the 90 degree orientation of the two receiver aerials in a model aircraft is not to have one vertical and the other horizontal. This situation would be hard to maintain for any length of time, especially the way I fly my model aircraft!!! It's more to do with if one aerial is orientated such that it receives a weak signal, then the other aerial has a better chance of detecting a stronger signal.
As my models are not built of radio absorbing or reflecting materials, it seems perfectly OK not to have them widely separated inside the hull . I do however keep them away from batteries, current carrying wires and such like. This would be hard to do in a model submarine but then 2.4 GHz is not usually commended for them.
Glynn Guest
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It is always good practice to separate the clean and dirty wiring in your boat. Power wires (dirty) should be separated from (clean) signal cables such as servo leads. Antennas should be considered ultra clean and kept well away from everything else. The antenna wires should be run vertically in a straight line. If they bend back on themselves, the induced currents will cancel reducing range. Also make sure that the Tx antenna is also kept vertically polarised. Noise is less of a problem with 2.4GHz systems than with the old 27 and 40MHz gear but good build practices should still be observed.
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and if more than one antenna connected to the same receiver kept a wavelength apart (approx 12.5cm @ 2.5Ghz) - assuming coax cable length allows.....
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Thinking about Aerials and their length I’ve come across this advert and bought one for my new Futaba 4PM Combo set, not that I’ll use it but more from curiosity:
https://www.ebay.co.uk/itm/361600376127?hash=item54310fdd3f:g:0vcAAOSwClNeioed (https://www.ebay.co.uk/itm/361600376127?hash=item54310fdd3f:g:0vcAAOSwClNeioed)
The set arrived today so I spent a few hrs reading through it - nowhere is mentioned extended aerials although these are claimed to be suitable for Futaba amongst others. So who uses such things and what claims are made?
Jim
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Hi Jim,
I think you know this - to clarify the Aerial length is not being extended (the actual part that receives the radio signal).
The cable exiting the RX case often consists of two parts:
1. A coaxial cable allowing the received signal to travel back to the receiver (the thicker part of the cable)
2. The end part - the "active" receiving element(s) of the aerial more often than not cut to a specific resonant wave length
The extension cable kit comes with a longer coaxial cable part allowing the receiver case to be mounted futher away from the active receiving element(s) of the aerial system.
Some receivers will have the coaxial cable soldered directly to the receiver board - some will use some sort of sma connector (see pic) - either way you have to open the receiver case to swap aerials.
Hope that helps
Regards
C-3PO
(https://modelboatmayhemimages.co.uk/images/2023/04/14/111.jpg)
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Thanks C-3PO, You’ve answered my thoughts exactly, I had thought the RX might have had a plug but seeing that the (sealed) case has to be opened I won’t bother because I see no direct advantage - EXCEPT for keeping its aerial vertical and above water.
Jim
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Yep, absolutely. Extended physically for mounting, not range.
Looks like still a standard "half-wave dipole" - the core of the coax protruding ~6cm out of the braiding. There is often nothing more to it than that!
If your tx has the 5" stubby type of plastic antenna - that's all that's inside the plastic.
Do be careful unclipping those little uFl connectors - you need to pop it off vertically upwards. Avoid any levering action, else you could rip the socket off the circuit board....
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Interestingly most of my parts have just arrived including the Gas Valve from Regner, also arrived is my RX aerials - 15 Cm long with 35mm tails, ….. erm! What to do with them about 20! ? They have solder terminals at lower ends but would they give more benefit than the original aerial?
Jim
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35mm sounds quite long? Can you post a pic?
As C-3PO says, what alternative you can easily use depends on how your current aerial is attached on the receiver. A uFl connector is ok to swap, but if you've currently got a soldered one then I would probably advise "don't mess with it" unless you really think you need to. Perhaps just change the whole receiver?! I you have to solder it, and you accidentally short out the two parts of the aerial then you'll have a range of maybe about a foot.....
A dipole aerial out of coax doesn't have to be the ~6cm - it does need to be a multiple/fraction of 2.4GHz wavelength (12.5cm) though. The radio waves 'travel up and down' at a particular frequency and have to be able to bounce back down the wire and not crash into the next wave. ("Resonance")
Quite complex in detail and I'm not a real RF expert, but just think about it in terms of waves bouncing off a sea wall - sometimes the peaks and troughs meet at the same point and cancel each other out. Roughly the same principle with radio - if they collide and cancel each other out then the signal is going to be weak. Best for radio is that the peaks meet in sync, then the signal is stronger.
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FWIW, one of my RC yachts (abs hull) uses a Spektrum AR410. No aerial wire, its built into the receiver circuit board. I've had no range problems at up to around 250 or more metres. I have positioned it to not be too close to the servos and battery as much as I can , no interfering 'lumps of stuff' too close, but it seems to work just fine.
Radio stuff is a black art..... ! :)
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I've just checked some of the receivers I have from 4 different manufacturers. None of them have same length of exposed part of the aerial. 2 of them Hitec and Flysky have an added section before the exposed section, this is supposed to improve the signal strength to the receiver. Futaba just has a plain end while some of my FrSky receivers have a length of PC board as the aerial, this has the tracks folded to give the equivalent of 4 times the normal length. I don't think that the actual length is that critical with our modern radios as the electronics can compensate and in boats the actual range is much more than you will ever need. I can remember way back to the old RCME 27MHz FM kits where one of the selling points was that the receiver length could be altered as it was no longer part of a tuned circuit, this being done by the electronics.
Jim
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Colth107, JimG,
With my previous boats used at the Norwich Model Yacht club I never had any trouble using 2.4 or the previous 35mhz systems but my book on Radio Control in Boats says that steam and Radio are not the best mix…which kind of puts one ‘on guard’ so to speak.
Jim
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When I used-to build model aircraft mainly using Futaba sets I always separated the rx aerials to 90 deg using chopped off cotton bud tubes secured to the acft frame, and mostly ditto with my boats, in my latest Windermere launch I’m placing said COTTON BUD TUBE vertically in Rx so as to (hopefully) assure signal receipt simply because I don’t want to risk damage to the craft that could be caused through a lost signal.
Jim
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Colth107, JimG,
With my previous boats used at the Norwich Model Yacht club I never had any trouble using 2.4 or the previous 35mhz systems but my book on Radio Control in Boats says that steam and Radio are not the best mix…which kind of puts one ‘on guard’ so to speak.
Jim
I think the main problem with steam and radio is the damp atmosphere and heat involved with steam engines. Keeping the receiver separated in its own compartment should cure this. The main importance with 2.4 GHz equipment is to keep the aerials clear of the boiler and engine as they will block the signal, less of a problem though as the transmitter aerial is above the boat at the ranges we sail at. Many years ago I ran a steam tug on 27 MHz with no problems with the receiver and servos in a closed compartment in the stern with the longer aerial kepr out of the engine room.
Jim