Pencils aren't lead anymore, they are graphite.

Okay, I read this whole thread but the numbers just phase through me, I am still only in Algebra 2 and math isn't one of my strong subjects...

Now here's the deal, can someone tell me/post pictures on how to make an antenna that works better than the stock, or haven't we figured this out yet?

If so please make it plain as day, IE: (Give exact length of wire to use from the mounting post on the rear deck)
I understand the straw part and how vertical is better than coil, but sort of confused on the mini z... Having more material that can recieve in the car itself increases range? Or should I just worry about the material that sticks out from the body.

Also I am guessing that you DO NOT want to mess with the antenna on the controller, the only way you can incease range is through the car itself.

but here is the jist of my question

I have 26.995 MHz crystal. I have CAT5 cable. Can someone tell me how much length I need and how to mount it to the rear deck?

Sorry to anyone if I sound like a complete idiot or if I missed a major concept somewhere along the line.

No problem at all. I just read the whole thread and wanted to try to help out a bit. Hope it is/was some help to someone, somewhere. That's one reason I posted the link to the antenna calculator. I figured it might help if my calculations had something other than a printed formula behind them. I will admit, though, that I had to not only grab my dusty old FCC license manual (yes, it was VERY dusty, since I've been licensed for over 20 years, and hadn't opened that particular book since my first test) to refresh my memory of the formula for a vertical antenna. I remembered the formula for a 1/2 wave vertical, but not a full-wave, which is what you were closest to, and that's what I had to look up, and that's where I started. The rest was all stuff I remembered from when I took my first test and each subsequent upgrade.

I was just hoping not to upset/aggravate anyone with my first post, so that's why the disclaimer. It appears as though I may have achieved my goal of being more informative than argumentative, which is what I was striving for, and that's a good thing. :D

Again, good luck to all, hope I was of some help...let me know if I can be of any assistance...I can't guarantee anything, but I'll sure try.

--Mike

Thanks for your input. My experience with antennas is limited, thanks for the clarification on some issues. :)

OK. After reading all of the replies, I can't help but stick in my $0.02 worth on this one. The correct formula for a full-wave vertical antenna is

Length in ft = 936/freq (in Mhz)

So, given that, for an 1/8 wave vertical antenna on 27.095 Mhz, which is the shortest that an online calculator that I located (use this address if you're curious: http://www.csgnetwork.com/antennaevcalc.html) will give me, the length of the antenna would be 4 ft, 3-27/32 in long. Now, you can divide that in halves as needed, but try to keep that in even multiples in order to keep the antenna tuned to the frequency you need. If you stray from your halves, you'll throw the tuning off unnecessarily and will cause the range to drop. Mongo's correct, of course, this shouldn't cause any damage, but your range will drop drastically, and you'll wonder what happened to your car as you struggle to gain control and get more and more frustrated trying to make it work.

More antenna theory for you: Turning the antenna wire around a form, such as a pencil, will create a loading coil, thus shortening the antenna length, it's true. BUT, be sure to remove the pencil, or use a non-conductive form, such as a plastic pen-housing or something similar in order to prevent interactions from the carbon-based substances in the lead of the pencil. The lead in the pencil will cause the tuning of the antenna to be off if you leave the pencil in the coil to help it retain it's shape. A pen housing is a better coil form. You should still have some vertical portion of the antenna after the coil, though, in order to maintain adequate reception and retain as much range as possible. I've considered building a folded dipole type of antenna for my XMod, but just haven't gotten around to it as of yet....it's on the list, believe me. It's much more complicated than what's being discussed here, but I'll post a tut if I get it to work well enough that others will want to duplicate it.

And yes, in calculating the antenna length, you need to take into consideration the length of the wire from the receiver board to the point where the connection is made from the wire to the antenna itself.

I wasn't intending to cause any issues or rain on anyone's parade, but I wanted to help anyone that was having any issues, and I've been working with radio for an awfully long time, now, so figured I could help out a bit...and have also been away from RS for almost half of that time.

Good luck to all!

i say as seen in another tut put a cap btw antenna wire and antenna to increase range instead of a straw which just looks tacky

peace 8)

With those antennas I was getting about 20 feet or so before it sputtered. I put the stock antenna back on and I'm back to about 50-60 feet with some sputtering towards the outter range.

Before I put the V2 and FatBoy motor in I had very decent range with the stock antenna. I've read that higher end motors cause more "noise" and therefore interfere with your range. I was hoping that using your method to create a better antenna would cancel this out.

Any suggestions?

How much range do you have with these antennas? If its only around 5 feet, you may have blown the reciever inductors. In that case, a 1:1 wave antenna will not help you.

If the inductors are good, you should get the same, or better range than the stock antenna.

I hope you took the batteries out of the car when you were working on the antenna. :oops:

Has anyone had luck using this method with Cat5 cable? I tried today to make two antennas using the shortest and next to shortest calculations.

Using a #6 crystal my calculations were as follows

984/27.255 = 36.103467

36.103467/16 = 2.2564667' or 27.0776"
36.103467/32 = 1.1282333' or 13.5388"

I measured that the wire from the reciever board to the antenna post is 4.5"

Using this I made a Cat-5 antenna of length 22.5 inches and one of length 9 inches.

For both I used an antenna straw from a hobby shop to keep it as vertical as possible (the longer one hung out of the top a bit). In both cases the range was worse than with the stock antenna if anything. Am I doing something wrong? Should I not subtract the 4.5" for the wire from the reciever board to the antenna post?

Any help would be appreciated.

Both are the same. Mongo's is simply condensed into one step, so use his it's shorter :lol: .

I'm wondering which method is more effective all around...

Correct

Ok, so if I read all that tech info correctly, you can create an antenna are a fraction of the total length of the optimal 36.44 but will lessen the range. But you could also coil the wire (which isn't as effective). So would it be more effective to use a wire 36.44 in length coiled, or a length at a specific fraction of the size? (as one can't go around with such a huge antenna by itself)

Oops :oops: sorry mongo, that was why it was different I was using the 27.095 mhz on my mustang and thats why it was off.

Wavelength (ft) = (984) / Freq in Megahertz

is the correct forumula. If you want to be exact, you can use the exact frequency that is stamped on each band, but the length would change by that much. My first post was just an example using straight 27mHz.

Be lieve me when I say this I just took a course in physical science, not saying you had it all the way wrong mongo, about the halvings and all you were right, but the formula is wrong. to tune your custom antenna you take the frequency of the chip that your xmod is using (find the numbers on the controller and multiply by a billion) in hertz and divide by the velocity of the wave, in the case of radio waves this is the speed of light, or 299800000 m/s. This gives you the wavelength in meters. You then multiply by one hundred then divide by 2.54 to get the wavelength in inches. Divide this answer down to what you think is a reasonable length (I divided by five and then by two a couple of timee). Sorry for the long post, just thought you needed to know :wink: .

No, if you coil it, range is reduced, but not like what you describe above. You still have 1ft 9 in. Just coiled.

The best antenna is verticle and straight. Coiling it will reduce some range. Coiling is good for extra long antennas that would be too big straight.

after some math i came out with 1 ft 9 in. if thats correct... :? so what happens if i coil it? it turns out to be a little bit over an inch so will i get an inch worth of range?

ah, I see. The manager at RS gave me a free antenna so I guess I won't have to worry about cutting wire the correct length.

No, there are set length, longer does not mean better if it is not matched to the frequency.

Look at the first post of this thread.

Those are the match lengths for the XMOD frequency.

I would include the wire that runs from the board to the antenna mount for total length. A stock car with stock antenna should be around 1.13 feet. (I really should measure that sometime :) )

So take a wire and make it the same length as a stock antenna. You will have an antenna as good as the stock one.

The next longest matched antenna would be 2.27 feet.

adding a few inches will make your range worse becuase then the antenna would not be matched to the frequency it is trying to recieve.

As far as wrapping wire is concerned, I have taken 6 feet of telephone wire (a single strand from the kind with four wires in it) and made a coil by wrapping it around a pencil. Using just this as an internal antenna, I got the same range as a regular antenna. I did not get to test it beyond across a room before I sold the car.

so all I need is like a 10in long piece of cat5 wire and attach it to the stock antenna post where my lost one wnet and I'm all good? If the original was 7in, then mine would be slightly better?

Use a non-cuductive post to wrap the wire around if you are worried about this. If the wraped wire allows current to go thru to what it is wraped around, you lose the legth because it is shorted to the shorter antenna.

In other word, you would defeat the length in the wrap because the current has a shorter path to take, straight down the straight wire.

i'm pretty sure that by doing the wrapping you'll have created two antennas that will fight each other for the signal.

I heard that to increase yout antenna's range you could do a copper wrap. You have to buy a roll of copper wire or use some from an existing wire. Then you just wrap the copper wire around the antenna in very small wraps. If you do the wraps small and tight enough, the copper wire would stay in place but you also have to tie the copper wire at the top of the anttenna. It increase my range alot. I already have a 14" antenna compared to the stock 7" antenna and wraped in copper. My car goes alot more farther than usual.

_________________

GTR
Li-ion pro kit
TOPCAD Turbo
R100 180 motor
cxp strut bar
AWD
Locked rear and front Diffs
custom 14" antenna
Carbon Fiber driveshaft
18 guage wire
6 wheels upgrade

did anyone find out if you can use a wire from inside a phone cord for this mod???????????

Thank you Mongo. I'd like to move it to the tut section for you since it has some valuable information in it, but as I have no mod powers in the announcement thread I cannot.

Hopefully someone can convince Kai that I am reliable enough to actually have the mod powers that everyone else here has. I am not pointing names but certain people went from member, to mod of the entire forums overnight, and Im still stuck with half powers. . .

sorry to get off topic, had to say it though.

Mongo could you please IM me on AIM, "DieCastoms" I had you on my list but dont know for some reason.

Thanks again.
DC

#1. diameter has no effect, only length.

#2. Have nottaken a close look. I would include all wire when considering length. So the wire that goes from the mount to the board should be included as part of the antenna.

#3. Should work, but not as well as one that was verticle. Maybe try the next length up if you can get it to fit.

Sorry for resurecting a dead thread but:

I am working on making some internal antenna for my car. I read this thread completely and do understand your length formula.

My questions are:

1. Does the diameter of the wire affect the length at all considering that a larger dia. would present more surface area?
2. In the picture that MNM posted, those are the metal plates used in Mini-Z antennas.. How is the formula applied to their size?
3. If I use a Cat5E cable, stripped of it's insulation, in 1/32 wavelength (1.13ft) and wind it around a flat piece of tine 1 inch wide (that would be about 7 times around) how well do you think that would work?

Im working on designing a custom internal antenna that actually screws in instead of these little coils of wire that get trashed if someone sneezes in Iraq . . .

Any info would be appreciated!
Thanks,
DC

Yes, that could work. Question is would a shorter verticle antenna work better than a longer horizontal antenna. Seems to be working with the miniz's. I plan on playing with antennas and testing different ones one of these days. On my list of projects.

same concept as it is for mini z'z with there internal anntenas!
those 2 green plates, have the same conecpt has you deiscribled!

oh, how bout this idea...

take two or three plastic plates, align them vertically under the body, and drill holes through the top and bottom:

______________________
o o o o o o o o o o o o o o

o o o o o o o o o o o o o o
______________________

you get the point; anyhow, if you threaded the antenna wire, cat5 wire, etc. through those holes

________
o o o o o
| /| etc.
|/ |/
o o o o o

the majority of the antenna wire would remain vertial, although not straight anymore... however, with this method you could probably fit 4.55 feet of wire under the xmod body, depending how many plastic plates you use... mongo, is this a viable way to do it?