spindrift

Being the newbie that I am - I have a question re antenna placement. Any help or suggestions would be appreciated.

During multiple web searches I have seen:
Antenna tubes run along the inside of the hull - just under the deck.
Antennas routed up through the deck and up the backstay.

I have a hitec ranger AM 2 stick surface radio. The receiver antenna is only 21" long - so it wont reach the stern from the SCU board (boat is 5' long).

I think I have two options:
Running a tube forward or aft from the RX, under the deck along the port rail. With a little breeze it worries me that the rail will be under water or close to it - will this block or disturb the signal.
I could run it through the deck and up a shroud or the mast.

Any suggestions on which one is best or are there better ideas.
Do people use antenna whips for RC boats?

Anyone ever mount the RX under the deck, upside down with velcro tape? Would that get it further away from any water that might intrude - or will the water run along the underside of the deck and get it more wet? I dont expect water but - an ounce of prevention.....pound of cure.....

Thanks in advance for your help,
spin

LtDoc

Spin,
Mounting the RX is up to you, positioning isn't critical at all. As long as everything will reach it (servo, battery lines, etc.), it'll work just fine. Keeping it dry is good, no matter how you do it (within reason!).
Running the antenna so that it ~may~ be under water at some point isn't the 'best' thing you can do. Won't harm the receiver but may cause loss of signals from being under water. Using a 'whip' like the car guys do shouldn't cause any electrical problems, don't know about mechanical problems with sail movements though. Running the antenna wire up the mast (non-metalic masts) works. Metal mast or stays can ~be~ the antenna, or support the antenna is they aren't metal.
- 'Doc

spindrift

LtDoc,
Thanks for the help. The tube idea (EC12 site) looked clean and uncluttered but being that low to the water sounds like it may not be the best.
Ill take a look at how it will route if I go up through the deck and up the side of the mast (solid wood). That way the deck penetration is near center where there will be less water as compared to the shroud chainplates.

If I remember correctly antennas are designed for an specific length (my TX antenna is about 24" and my RX antenna is about 22" ). What would happen if I make the RX antenna longer ?

Sorry for the newbie questions,
Thanks for all the help,
spin

LtDoc

Spin,
Some antennas are frequency dependant for length. But those used on most R/C radio systems are more dependant on 'practicality' rather than frequency and length. The length supplied with most receivers is because thats the length the manufacturor figures will yield a strong enough signal at the ranges it's normally used. [The same does NOT apply to transmitting antennas! Don't mess with the transmitter's antenna, it's a particular length for a very good reason.]
Shortening a recieving antenna usually means a shorter usable range. Lengthening it usually means a slightly longer range (but not a lot). Shortening or lengthening a receiver's antenna doesn't do anything 'bad' to the receiver it's self. Going from a 2 foot antenna length to a 4 foot antenna length will not double the range, but it also won't shorten it, and it won't harm the receiver.
- 'Doc

PS - For those who have a background in radio electronics, you know that all of the above isn't exactly 'pure truth'. But when you boil it all down, it's close enough so that it just isn't gonna matter. Besides, who wants to try explaining reactance/impedance/resonance in 5 words or less?

spindrift

LtDoc,
great info - thanks. I might just solder on an extension and route the antenna under the deck through a tube aft and then up the backstay a bit. That should get it a bit longer and a bit higher off the water and shouldnt look to bad.
Really appreciate the help -
spin

pompebled

Hi Spindrift,

I have the antenna connected to my backstay (which is ss), effectively making it over one meter above the waterline, it gives me reception beyond practical use (a very tiny white triangle in the distance...)

I'll post a pic when I get home.

The blue lead has a 2mm goldplated connector, the counterpart is soldered onto the receiver end.
On deck the blue wire is soldered to the brass sleeve, that tightens the loop of the backstay.
The backstay itself is mounted with a clip onto two loops of Deneema as insulation.
I made the top loop adjustable with a slider, but that's beside the point.

Let me know if you need more pics.

Regards, Jan.

spindrift

Jan,
Thanks - I look forward to the photo. I hope I dont ever have to try the tiny white triangle test......
If it is connected to the backstay (soldered?) then do you have some sort of connector/disconnect fitting that allows you to disconnect the antenna and remove the RX from inside the boat?
Thanks,
spin

pompebled

Seeing my picture, I realize I really must clean my boat more often, as a whole it looks rather tidy, but the water obviously makes it dirty, detail photo's show that, yuk!

Regards, Jan.

spindrift

Jan,
It all makes good sense and thanks for the pic. I like the idea of the gold connector at the RX. Then you can remove the RX from the boat and leave the rest of the blue antenna wire in place.
Once again thanks a bunch for the help.
spin

tsparks

Hey Spin,
Just putting my vote in for internal antenna. I tried it both ways on my Atlantis, internal and external, and honestly, can't say I noticed any difference in the performance. If you look closely in the bottom right side, the green wire is the aerial taped to a piece of scrape wood. Now with it internal, it's just one less thing to deal with when taking the masts down for transport.
Taylor

spindrift

Taylor,
Thanks for the pics and suggestion. Id agree that its definately much cleaner looking. My current plan is to install the antenna at normal length in a tube holder that will have a velcro support block allowing it and the RX (also on velcro) to be easily removed from the boat. Ill do some distance testing of the system with that setup and possibly some preliminary sailing. Then I can make changes to the SCU / winch / battery / RX installation prior to drilling another hole in the deck.

If range testing suggests a change is required - Ill add a connector at the RX, double the antenna length, go above deck, supported by the rig. Then the section of antenna can be permanently mounted in the hull, sealed at the deck penetration and the RX can be removed by disconnecting it from the antenna.

Thanks,
spin

spindrift

Just wanted to thank everyone for their help and give you all an update..
I ran a range test with the stock antenna and RX resting on the deck (horizontal antenna). The boat was inside my garage. Walked away and did the verizon test ("can you hear me now" )... I was approximately 200 ft away when it started to lose solid signal.

This was definately not a clear line of site test - boat in garage, fence, houses, trees, cars inbetween the RX and TX. I had flourescent lights on in the garage (I have heard that they adversely effect RC).

2nd test - Extended the antenna wire by soldering on additional length (added approx 2X original). Ran the wire from the RX which was velcro'd under the deck, out through the hatch and up the mast (mast is wood). Ran the same test. I quit testing before I lost solid signal - I figured that I was well outside the range that I would ever want to sail it. If I were to estimate the distance I was from the boat I would have to say that I was almost 3X further than the first test.

Conclusion - the stock antenna mounted in a tube under the deck would probably work fine in open water. However, Im going with the longer wire since it allows me to reach the mast and get some vertical orientation to the antenna (from where I located the RX the stock wire was too short to reach the mast or backstay).

Oh - if anyone is curious my radio gear is Hitec 2 channel AM Ranger IIN.

Once again I appreciate everyones help. Maybe some of this can help others new to RC sailing.

Happy Sailing,
Spin

LtDoc

Spin,
Thanks for the 'up-date'! Now, if you really wanna make it more better, swap to a directional antenna on your transmitter! At 27 Mhz that's sort of big, but who cares, right? Also need a very strong back, or a rotor to turn the thing. Modify the transmitter's output power (hey, the CB'ers do it!), few thousand watts ought'a work just fine. Oh, don't use mylar sails! Just like in a microwave, they sort of disapear in a puff of smoke with all that directed power (ever put a 'Pop-Tart' in a microwave without removing the foil??).
- 'Doc

spindrift

Doc,
Thats great - I dont know much about antennas (or electronics) but your comments brought back memories from years ago while sailing on merchant ships. I used to hang out in the radio shack with the radio op during off hours. He was into ham and we would make ham ship to shore calls and talk to different people all over the world. Apparently many ham operators would keep track of the different countries they connected with. If I remember correctly one of the coolest things the radio op would do was rotate the antenna so that it directed the signal the long way around the globe and sometimes we would get better reception.

Now those guys are into their electronics - sometimes he would disassemble the radio and reassemble it because he was bored... Not me - I know just enough to be dangerous with a meter and soldering iron... Im just glad I can get assistance from generous people on sites like this. Maybe someday I can return the favors..
Spin