Im a bit of a newby at RC but whilst in industry i came across a flux for joining copper to ally through a tinned joint stand corrected if wrong (it has been known)!

Thanks Doug i was previously under the impression longer did not matter.Excellent info👍

hi there Colin,

just to put another spanner in the works - when I built an MTB, I made a Carley raft and in the interior of the floating chambers I wound a coil of aerial wire for the receiver - this sits on the deck. I know it goes against all rules for radio control - but - this model has a pretty good range - The length of the lake - how long the lake is I cant remember. However I know anything now more than 100 yards away it goes to a blurr. The other model is HMS Ajax and what I did there I measured the length of the aerial - cut it so that from the receiver to the deck was about 3 inches. The rest of the aerial is made up of brass railing around the side of the boat to the equivalent length of the original aerial.

This again works well so my theory is, if its worth anything, we are not flying aeroplanes where they are hundreds of yards away - the majority of the time, we sail models pretty close to ourselves.

John

Thanks for all your help shipmates, now got my head around the problem.
Cheers Colin.

Hi, my experience is that assuming you wish to keep your model boat in visual sight then the aerial length is not critical.

Make sure there is some of the wire going along the length of the boat and that here is at least 6 inches of vertical aerial. I often have a fixed vertical scale aerial with a trailing wire and socket and plug the end of the aerial into it.

This means I can remove the superstructure and just unplug the aerial.

Sorry this is not a technical answer but I have a background of electronics and up to 200 or 300 feet range it is not a problem.

I have seen many model boats where the aerial has never been undone from new, they seem to work!

Let us not find extra things to worry about! We have enough on our collective plates already!

Best regards

Roy

Talking of 2.Ghz If I really let my Laser dip with the wind I lose control momentarily but regain control within seconds

Hello.i have found that.
The rule is 40mhz is 40 inches long.
The rule is 27mhz is 27 inches long

Hi Doug
Thanks for your superior knowledge.👍👍

"That's why I still have and maintain my old Graupner MC-10 40Meg set for my subs.
Never seen a 75Meg set, they ain't allowed over here.
Thought they were for hairyplanes with you guys?
Maybe they changed the frequency allocations when 2.4 Gigs came in."
Nope, 75 has always been a surface or sub surface as the case may be, freq over here. 72 is aircraft only. I love my Robbe F-14 just for that reason. We may be cousins, but we are definitely different, in case no one has noticed yet.....😁

"the wire length is 61.0 cm. From the case."
Sounds good to me Colin 👍
Same as my little Nano RX.
Should work a treat, does for me in my U25.
My eyes fail before the control does 🤓
Look forward to your Sea trial report Admiral.
FLEET// 😎😁

"Does the length take into account any directional changes in its routing to the outside of the model."
No Colin, what matters is the total physical length of the antenna to ensure optimum matching to the RX input circuitry, and hence max signal transfer from the antenna to the RX.
If this matching is 'off' part of the signal is reflected back to the antenna and lost 😭
That's why you often see in the RX instructions a warning not to alter the length of the antenna wire!!
Keep as much of the antenna as possible vertical 👍 Not terribly critical though for our purposes. See also my previous comments re vertical and horizontal signals!
Cheers, Doug 😎

Thank you for your responses guys. Doug the wire length is 61.0 cm. From the case. Thanks I will check it out on Saturday.
Cheers Colin.

"As a rule though, the lower the frequency, the better the radio signal is able to penetrate hard objects. Hence, 27mhz, 40mhz and even 75mhz work well for submarines because of the signal's ability to get thru the water. 2.4ghz and higher hate solid objects. "
Agreed TD 👍
That's why I still have and maintain my old Graupner MC-10 40Meg set for my subs.
Never seen a 75Meg set, they ain't allowed over here.
Thought they were for hairyplanes with you guys?
Maybe they changed the frequency allocations when 2.4 Gigs came in.
Cheers, Doug 😎

Hi Colin,
Do not route your antenna wire inside a metal tube mast!
The metal tube will block or reduce the signal reaching your wire antenna.
On my destroyer I have a brass tube mast so I included it as part of the antenna by soldering the RX antenna wire (suitably shortened) to the base of the mast.
Works fine over several hundred metres, until I can't what the ship is up to anyway 🤓
If you include any metal structure, mast etc, in your antenna then shorten the antenna wire by the length of the structure. Total antenna length as described below.

Soldering to ally is a no go 🤔 So either use a brass mast as I did or string the RX antenna wire from a stub mast (jack staff) on the bow or stern up to the mast head.
I did something similar on my Type 1A U Boat; from bow to conning tower and down to the stern. Works a treat, all well insulated from the wet stuff of course 😁
BTW Colin; if your RX antenna is mounted vertically on such a mast make sure you also hold the TX so that the antenna is vertical. Do not point the antenna at the boat.
Why? The RF signals are sent and received by waves propagating at right angles to the TX antenna. Virtually nothing comes out of the end of the antenna.
Similarly, if you run your RX antenna horizontally around the boat then also hold your TX such that the antenna is horizontal for best reception and range.
Why?
There is a factor of 10 (20dB) difference between horizontal and vertical polarised RF waves!
So if you get it wrong (mismatch) the signal voltage received at the boat (and range) can be reduced by a factor or 10 or so.
Cheers, Doug 😎

"I was hoping to route inside the mast, and will the aluminum mast reduce reception.
Or would it be better to have a separate fixed antenna to attach the aerial wire to and do I need to alter the wire length."
Again, good question Colin. You are barking up a tree that I am not too familiar with. That said, I have routed my antenna up a mast by attaching it to the outside of a mast and suffered not ill effects. It is easier to access as well, in case I need to change the receiver, as when I sink the boat.......😋
As a rule though, the lower the frequency, the better the radio signal is able to penetrate hard objects. Hence, 27mhz, 40mhz and even 75mhz work well for submarines because of the signal's ability to get thru the water. 2.4ghz and higher hate solid objects.

Good question Colin!
Depends to a certain extent on the internals of the RX.
40.675 MHz corresponds to a wavelength of 737 cm (24.181feet) 😮
Which would be the resonant length of a single element monopole antenna, or single wire antenna like ours in RC.
Obviously a bit impractical, unless you have a helium filled airship to hold your antenna aloft 😁 (Side note: I have a small airship but no helium 😭)
Soooo!
To keep things practical we work with sub-harmonics of the frequency.
1/2 wave, 1/4 wave, 1/8 wave etc.
At 1/8 wave we get down to a more practical length of 92.125 cm for your frequency.
I just checked two of my 40Meg band RXs, measuring from where the antenna wire exits the case:-
1. Graupner C17 FM40S, Standard size in typical 90s plastic box.
Antenna length 98cm. The extra length, beyond the 92cm for your frequency, ensures that it can also cover the lower frequencies of the 40 Meg band.
2. Conrad Digital 4 Nano RX.
Antenna length 61cm.
Thereby we come to the relevance of the RX internals to account for the difference!
Usually the antenna (what you see outside the 'box') has been artificially 'shortened' by adding the 'missing' length in the form of a closely wound coil of fine wire inside the RX case. A so called matching or loading coil which together with the external wire gives the total Effective Antenna Length. Thus the first sentence of my answer! 😉
The Conrad RX appears to have an internal coil of longer effective length, i.e. more wire!

Therefore I suggest that you start with a wire length of 92cm.
Measured from where the wire is soldered into the RX board.
If that's not practical measure from where the wire exits the case. Close enough😉
Do a range check and note the max reliable operating range.
Replace the antenna wire with one of 60cm and repeat the range check.
Compare results and use the best of the two lengths.

Otherwise we're gonna have to open your RX and see what sort of matching coil it has!
BTW: AM or FM makes no difference to the antenna.
That is only a description of how your control pulses are impressed on the 40Meg carrier wave at the TX, so called modulation. By twiddling the Amplitude or the Frequency. FM is better by the way, like in the old car radios; reception always better on FM 😊
This is detected and decoded, demodulation, after the RF carrier antenna and amplifier stages.
All clear? I know, clear as mud 😁
To cut a long story 'sidevays' start with 92cm and see what happens.
Bon chance mon ami 🤞
Cheers, Doug 😎

Does the length take into account any directional changes in its routing to the outside of the model.
I was hoping to route inside the mast, and will the aluminium mast reduce reception.
Or would it be better to have a separate fixed antenna to attach the aerial wire to and do I need to alter the wire length.
Cheers Colin.

Colin,
While I do not know the length specification, I can say that it is measured from the receiver, not the height above the model.