?
Solved

circuit schematics - FM Transmitter and reciever

Posted on 2005-04-06
14
Medium Priority
?
3,693 Views
Last Modified: 2008-01-09

Hello all,
        I have a need for a FM transmitter and reciever. I play paintball alot and have decided it would be beneficial for a small walkie talkie type system. i do not want to purchase a pre-made system however, i want to build them myself.
size and weight is everything in this.

i need good instructions for someone who has not designed schematics or have any background in FM modulation, i do however have a good understanding of electronics and have built my own devices before from well drawn schematics and sources.

i would like to use a small power source such as a VERY common watch battery or laser pointer batteries. a small microphone that is preferrably water resistant. and will also need to have a reciever. the entire system will be attached to the bottom of my mask (the need for lightweight cant be stressed enough).

thx in advance


0
Comment
Question by:ViRoy
  • 4
  • 3
  • 3
  • +2
12 Comments
 
LVL 12

Expert Comment

by:GinEric
ID: 13718358
I used to have these around.  The core component is a Voltage Controlled Osciallator [VCO].

Trying to get it into something with a watch battery is really something else; you're talking about real "spyware," which costs, in a shop, in the $300.00 and upwards category.

Because you're talking about microelectronics, I doubt you can build this yourself, at least not without an extremely good laboratory, like M.I.T.'s, one with the ability to generate substrates and such.

That's because of the "watch battery" and the first problem you'll have is distance.

I've designed, diagrammed, and built this stuff, but it requires probably more than you have at hand.  You might be able to scalp two FM transceivers from a walkie-talkie, but size, again, is a problem, along with emitted power, etc..

The band frequency that real spyware uses is in the military range and above.  Stuff that's not easy to come by.  That's because of the nanowatts power.

Maybe you should first start with a simple FM transmitter and/or receiver first, to see what all the problems will be.  For that, you pretty much need only the VCO as the basic component, available from catalogues and maybe Radio Shack.

Look for an FM kit online.

Are you playing pinball underwater?

:)
0
 
LVL 5

Expert Comment

by:J-A-L
ID: 13718836
or maybe consider mounting a slightly larger fm receiver/transmitter on your back with a sufficient battery
and bring up to your helmet some how.  Since you can't play paintball without a helmet.  Doing anything miniature you're looking at using surface mount technology.  If you want to have someone do circuit boards for you though, I recommend pcbexpress.com... they also have free software to lay out your circuit paths and stuff.

Lots of chip manufacturers are also moving away from dips and providing more stuff surface mount these days... bad news for the hobbiests.

Jeff
at yourtechonline.com
0
 
LVL 16

Expert Comment

by:dhsindy Sparrow
ID: 13718871
This is a pretty cool transmitter (AM and FM at the same time):

http://www.electronics-lab.com/projects/rf/028/
0
[Video] Create a Disruption-Free Workspace

Open offices have their challenges. And Sometimes, it's even hard to work at work. It's time to reclaim your office and create a disruption-free workspace. With the MB 660, you can:

-Increase Concentration
-Improve well-being
-Boost Productivity

 
LVL 8

Author Comment

by:ViRoy
ID: 13721687


J-A-L: you kinda missed the whole idea of making my own :) those are all pre manufactured and the last one you listed from ebay is nothing more than a ear peice... has nothing to do with transmitters at all.

Dhsindy: thats a pretty interesting little device! dunno why youd want both FM and AM transmitting at the same time, but it sparked a thought as to wether AM or FM is the best way to go. i know FM is clearer quality, but im using mono voice over maybe 300ft. maybe AM would be better?

in the mean-time ive been searching and found something that is exactly what im looking for.
http://www.talkingelectronics.com/FreeProjects/FM-Bugs/Voyager/VoyagerP1.html
2400ft 9v transmitter, tiny for the power!

http://www.talkingelectronics.com/FreeProjects/FM-Bugs/MicroBug/MicroBug-P1.html
Microbug! soooo tiny, all SMD ... learn to solder SMD first

they would both need a few small modifications to suit my needs, but luckily for me they already covered those topics in the tutorial! :D
i still wonder if AM would be a better choice, i know nothing about AM vs. FM transmitters.


0
 
LVL 8

Author Comment

by:ViRoy
ID: 13721694

eric: paintball, not pinball lol :)
0
 
LVL 12

Expert Comment

by:GinEric
ID: 13721791
For tactical stuff [in and out of water :)  ] you might be able to get it all in a helmet.  The mil does.  The batteries are built into the helmet, special purpose, and there's even a "recharge" plug on the helmut.  You'd need a relatively new helmut.

J-A-L I used to use a place out of Virginia for printed circuits, they provided a program call PCDATAK, but I still wound up drawing it by hand, photocopying for the etch, and shrink down.

Since most examples don't really tell you what you need to know, there's only books for the schematics and theory.

Paintball with stainless steel pinballs could be interesting, eh?

:)
0
 
LVL 5

Expert Comment

by:J-A-L
ID: 13721883
all this will have to fit in your helmet of course...
Frozen paintballs hurt enough by the way without making them metal... and the ebay thingie...yeah, that does require the transmitter/receiver the guy sells as well.  So, if you really really wanna make your own.

The pcbexpress gives you easy to use software... plus their software automatically sends your drawing and gives you a live estimate on the cost depending on # iof boards you want, etc.  FM would be more clear and take less power most likely. You'll still need an antenna for best gain... FM has the smallest antenna you need to power.

Jeff
0
 
LVL 8

Author Comment

by:ViRoy
ID: 13729224

umm no, im not gonna go through all that... idea is to keep minimum cost with good reliability.
i got a feeling i will be making many of these... many people will not dare change any of their equipment such as buying new mask (i use a special lightweight anti fog mask $90)
thats why it has to be real lightweight and versatile

that link above is exactly the size and weight im loking for... now i need to deal with making a reciever.
0
 
LVL 12

Expert Comment

by:GinEric
ID: 13729265
AM runs "along the ground" which must be considered.  FM is free radiated waves, not requiring land.  Television was the first to use AM and FM together; AM for picture with FM embedded for the sound.

AM will "break up" whereas FM is more reliable.  AM is affected by small weather phenomena, FM generally isn't.

Voyager and Microbug are the same circuit, if you look at them, a transmitter.  You need a transceiver, that is, a transmitter/receiver for what you want to do.

One transceiver:

http://www.iitk.ac.in/robotics/Socrob2000/onboard.html

The chip:

http://www.micrel.com/

If you think about it, cell phone pretty much does exactly that and more.  This whole technology has to be down to about one chip for cell phones to work.   The only thing extra a cell phone does is to relay it via towers for wider range.

http://www.pmc-sierra.com/wireless/

While it may be a little harder to find a chip to do what you want, any cordless phone does it.

You have to be creative and search through catalogues, even order some, GTE, National Semiconductor, RCA, others.

First find out who makes the cordless stuff, and what's inside.  Usually around 800MHz, then go from there.  Each the phone and the base have to have transceivers.  Any two phones on the same frequency will be heard together [which is how scanners pick them up anyway].

The pickup can be replaced with any cheap computer headset with mic; you may also find some wireless headsets that will do the complete job.  Lots of people already use these, concerts, sports events, military, etc..  And every pilot uses one.

Eat the bun, and start thinking.
0
 

Accepted Solution

by:
modulo earned 0 total points
ID: 14395321
PAQed with no points refunded (of 250)

modulo
Community Support Moderator
0
 
LVL 8

Author Comment

by:ViRoy
ID: 14405193
DOH!, man u guys shoulda given me a lil more time, i know it was a few months ago and i know it eats up those precious few kb in the db.... but i woulda atleast awarded the points away rather than wasting them and everyones effort. are you guys competing for cleaning up?
0

Featured Post

Get your Conversational Ransomware Defense e‑book

This e-book gives you an insight into the ransomware threat and reviews the fundamentals of top-notch ransomware preparedness and recovery. To help you protect yourself and your organization. The initial infection may be inevitable, so the best protection is to be fully prepared.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Arrow Electronics was searching for a KVM  (Keyboard/Video/Mouse) switch that could display on one single monitor the current status of all units being tested on the rack.
Backups and Disaster RecoveryIn this post, we’ll look at strategies for backups and disaster recovery.
Please read the paragraph below before following the instructions in the video — there are important caveats in the paragraph that I did not mention in the video. If your PaperPort 12 or PaperPort 14 is failing to start, or crashing, or hanging, …
Loops Section Overview
Suggested Courses

840 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question