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[John W E]

Hi all,

Just a quick query.  Has anybody altered an aerial on their receiver to incorporate it into say, a deck guardrail fitting?  If the model is of sufficient length and the railings around the outside are the same length as the aerial on your receiver.   Has anybody every cut short the aerial wire off the receiver and soldered it to the deck railings, using the railings as the extra length on the aerial.   Obviously, the railings have to be of a metallic construction.  I wonder if this can be done?

 :) Aye
John E
BLUEBIRD

[gribeauval]

I do this with all my lifeboats but in my case I use the actual VHF aerials on the model as the vertical section not the handrails. I use a small 1mm plug and socket to allow the superstructures to be removed. 

Mike

[John W E]

Hi Mike, do you notice any effect on your transmitter's range? or...any side effects like jittery servos or anything?

aye
john e
bluebird

[Doc]

John,
Can it be done?  You bet!  Almost anything metalic above deck can be made into 'part' of the antenna.  Handrails, masts, scale antennas on those masts, and so on.  Antenna length isn't all that critical.  Shortening an antenna isn't exactly the 'best' thing to do, but lengthening them doesn't hurt.
Side effects.  Certainly possible, not really all that likely though.  If an antenna is shortened or 'lowered' the range will suffer to some extent (range testing!).  Getting the antenna higher will usually extent range to some extent.  Probably not much, but you won't know till you try it (talking feet, not hundreds of feet range).
Forgetting to connect the antenna to the extensions is the worst part of the whole thing.  Really cuts down on range! lol
 - 'Doc

[gribeauval]

Hi Mike, do you notice any effect on your transmitter's range? or...any side effects like jittery servos or anything?

aye
john e
bluebird

Not if the plug is tight in the socket and as Doc says range suffers if you forget to plug it in !!!!

[John W E]

  the reason I ask is that I have had a disastrous weekend with electronics

the Gremlins are in; I didnt fancy frying my RX by finding out that the aeriel wire needed to be a certain omage resistance  and me replacing it with just a deck rail which may not have the same electrical resistance as the aerial
aye (fingers crossed)
john e
bluebird

[BobF]

Hi BLUEBIRD, (why do I have to shout your name)?   

I have heard that with a horizontal receiver aerial, that it can lose reception, when pointing directly towards or away from the transmitter. Not tried it myself.
I have posted this before, but a lot of the one meter yacht sailor's, run the aerial inside the hull just under the deck.
Also quite a few suffer from reception problems! and there is no electric motor to cause problems either.

Bob

Oh, and I had yet another bad weekend for electronic speed controllers.
They keep burning out. This is the third one that has gone up in smoke whilst on stand by. No big amps nothing. Just grey smoke. At forty quid a time, it's not funny. As the instructions say that it had auto cut out for over load and motor dead short protection, and there are NO wiring faults it's a real puzzle. The only thing that was different was that I had just fitted an eight cell pack  to replace the seven cell used for the last run, but it's an up to twelve volt controller.
And strangely that was exactly the same set of circumstances as the last time, but with a different model.

[RickF]

John,

My electronics is not that clever, but I don't think current flows in an aerial, so the size should not make any difference from that point of view.

Aerials can be "tuned" to wavelength by making them multiples or factors of the wavelength (I think!), but this would only work for a true vertical or horizontal aerial and I guess would be superfluous with the ranges we are taking about. Given the usual advice when installing a radio - something along the lines of "arrange the aerial inside the boat" - I would think any increase rather than decrease of total aerial length will have little effect. I certainly intend to incorporate the brass tube mast on Torpedo Boat No 80.

Rick

[funtimefrankie]

I've two recs, both 40mhz FM, with different length aerials from new ???

[kendalboatsman]

Hi Frankie,

I soldered my receiver aerial to a screw tag which I screwed to the bottom of the mast on my 590s. I even sailed it on ullswater a couple of times with no noticeable range problems.

My R/C'd HMS Bluebell was on 40mhz futaba and I used sticky cable tie bases to position the receiver wire in a loop around the hull. Again no noticeable range problems. Biggest pool I sailed that on was "Keepers Pool" between Abergavenny and Pontypool. Hugh Bright (Think it was him!) did an article in Marine Modelling about receiver aerials and operating lengths. Will see if I have a copy of it.

Hope that helps

Clive

[Doc]

Antennas like other antennas that sort of look like they do.  Vertical antennas like vertical antennas, horizontal ones like horizontal ones.  The 'V's and 'H's are not incompatible, they just don't like each other as much as ones like themselves.  Pointing a vertical antenna at another antenna, of any kind, is sort of a 'no-no'.  Signal strength off the end of a vertical antenna is less than anywhere else around it.  Won't make a huge difference, but it will make some difference.
There is current flowing in an antenna!  But it's so small in a receiving antenna that it's very difficult to measure.  If you threw a very long wire over a tree during a thunder storm, don't hold the bare end of it and wait for a lightning flash.  Awww, go ahead!  Only a real idiot will do that more than three times.  :)  Sort of like touching your tongue to a 9 volt battery's terminals to see if it's charged, you know?  Don't try that with the 'mains' outlet!  (Or go ahead, but put me in your will??)
 - 'Doc

A general 'rule' for model antennas is 'the longer the better'... within reason.  It's better not to coil it up, and the higher you can get it the better.  After that, it's whatever you can get away with and not be too ugly.

[tonyH]

Can anyone advise what happens when the whole boat is made of metal.

Is the length of aerial inside the hull/superstructure redundant or can the aerial be attached to, say, the cabin roof to make up the full system?

Ain't life fun?


Tony H

[RickF]

Just my two-pennyworth, but would not an all-metal boat used as an aerial pick up an awful lot of interference from the rest of the electrical gubbins? Better to fit an insulated exterior aerial, I think. But, as Martin would say "What do I know?"

Rick

[Colin Bishop]

An all metal boat would be effectively earthed by the water so you are likely to have problems.

[Bryan Young]

yes. but I also stick a bit of wire into the funnel and connect it to a "chocolate block". Also connected to the "block" is a strip of 1/8" brass strip. this strip touches on a brass rod connected to the receiver. No more plugs and forgetfulness.
But just as oddly, most R/C sets are made for the aircraft fraternity..our signals bounce across water. Leading the aerial around the inside of the hull works well on Tynemouth lake....which is big enough for you to lose track (visually) of what the boat is doing. The closer to the water the better.    Bryan Young.

[Doc]

All metal boats.  If it'll work on the big metal boats, it'll work on the small ones too!  Metal 'shields' an antenna, so getting it out of the metal boat is good.  Having it down inside the metal hull would 'hide' it.  Except for the 2.4 Ghz systems this is really ridiculous but, there's something called a "slot" antenna, a 'slot' cut in metal that acts as the antenna.  Used on a lot of metal planes (the big ones), nothing sticking up to cut speed, sort of.  You could even fill that 'slot' with some kind of insulating material and paint over it (non-metalic paint, naturally).  Size really DOES make a difference with the 'slot' antenna so for bands other than 2.4 Ghz, forget it.  Neat idea though!

Antennas inside a boat (if the boat isn't metalic) do work.  There are some "but's" though, and they hold true for any antenna, any band.  Coiling a recieving antenna up doesn't really do any kind of good, it actually shortens range.  The tighter the coil the worse the reception.    You can shorten a transmitting antenna by coiling it up, but that's a 'horse of a different color', not the same for receiving antennas.  A very 'general' rule of thumb is that if the antenna wire parallels it's self closely, it's about like cutting that section of wire off.  That's not 100% correct, but sort of.  Naturally, keeping the receiving antenna away from anything else metalic or electrical is a good idea... not very practical, but good.
The quick'n'dirty way to do things is to try it and see.  There's not a lot you can do to hurt a receiver's antenna unless you let it touch 'electricity' (that make sense?).  Experimenting with different antenna positions doesn't hurt.  Range testing is a VERY good idea!
 - 'Doc

[BarryM]

Sorry to be dim but:-

If the handrail to which I am soldering the aerial is 600 mm long and my aerial connection is at mid-length, how much do I shorten the aerial wire by? 600mm or 300mm?

Thanks,

Barry M

[BobF]

Hi BarryM,
Don't shorten the wire.

This has been posted before, so just a quick up date. If the aerial is shortened Rx or Tx, it will reduce the reception range. Adding length to the receiver aerial, will not reduce range, but will almost certainly extend it.

Bob.

[dougal99]

Bob

That's news to me. Everything I've read to date (except your post) advises that the RX aerial should be kept to the length provided as the RX circuit will have been tuned to it. Thus when using mast etc as part of the aerial you should remove the corresponding length form the aerial wire.

Are you saying this is incorrect or that it won't make much difference?

Doug

[DickyD]

On my Robbe kit the instructions were very specific.
The antenna cable had to be soldered to one of the radio aerials which was 150mm long.
Robbes instructions were to cut off 150mm from the antenna cable prior to soldering.
This I did and the receiver picks up the signal at approx 200 yards no sweat, don't need that distance.

Richard

[tolnedra]

Richard, if you're anything like me, (advanced age!) you can't see what the boat is doing at 200 yards! At the moment I'm building a 40" tug (Tyne Models "Alfred") with the hope I may be able to see it bit further away, and which way it's facing!!!

Danny

[DickyD]

As I said Danny "don't need that distance." it disappears from view at about 100 yards and its 4 foot long, my camouflaged corvette even sooner.
I am now going to do PT15 and hope I'll be able to see the bow wave.
 
Richard 

[BobF]

Hi dougal99 and others,

This topic has been gone over many times before, I thought on Mayhem, but may be the old M.B. forum.

I'm sure Doc and others will come back with Tech Spec if required.
It has been stated (by experts) before about wave length of aerials etc. and I was trying to avoid going over it again.

I have for some years, attached the full length of receiver aerial to the base of my One Meter Yacht masts, which adds an extra length of approx 70 inches on a number one rig. The only result of doing this, was to add a great deal of range. I have never experienced the problems of signal loss, that a lot of the yachters that run aerials round the inside of the hull have. On the pond at Brid, that I know you have sailed on, I can sail the whole pond, with the transmitter aerial down, with no loss of signal.
(not something I do other than to check reception range, as this will almost certainly damage the output stage on the transmitter)

I have never had a receiver fail as a result of lengthening the receiver aerial. I have never actually had a receiver fail for any reason, unlike Electronic Speed Controllers, which I appear to be cursed with at the moment.

I am not an expert, and can only go by the suck it and see method. I have been in the hobby this time round for the last ten years, and any remarks I make, are usually based on actual sailing time and not theory.


Bob

PS dougal99 will you be at Skipsea this year? if so, see you there.

[Doc]

Adding to a receiving antenna isn't going to hurt anything.  If connecting to the handrails is an option, fine, do it.  If having too much antenna length inside the boat is a problem, and you've added to the thing by connecting to the handrails, shorten the antenna inside the boat by whatever the length of 'half' the handrail is.  Connecting the antenna to anything metalic means you've added some amount of length to the thing.  That can be good or bad just depending on what the metalic stuff is, how it's positioned and how you get along with gremlins.  If you want to try something different, try it.  The usual 'catch', give it a range test.  If it shortens range, do something else.  Antennas have little chance of harming a receiver as long as the applied signal isn't too strong.  That 'signal' might also be electricity of some form, battery, etc, which does stand a good chance of ruining things, so don't.  After that...?  Good question.  Try it and see.
 - 'Doc

(If you happen across some miraculous combination, don't tell anyone except me!  We'll make a fortune!)

[BarryM]

Thanks Doc - all I wanted was "half-length" or"full length" of handrail but the subject seems to raise mighty passions in the breasts (am I allowed to say that word on this forum?) of many. Is there any mileage in starting a 'My Aerial is bigger than your Aerial contest?   

Cheers

BarryM