If you want to know real testing data for the range of the car alarm you want to buy, and have by now learned that you cannot trust the manufacturers claims then you should check out this site:

https://gullfoss2.fcc.gov/prod/oet/cf/eas/r...nericSearch.cfm

This site will give you the RF emmisions characteristics of basically any product which is sold in the US.

When a company releases a product they must send it in to the FCC to be tested to make sure it doesnt exceed limits in power and spectral range of output.

It does require a bit of hunting though, because you need the fcc id's of the products or other info , so that you can search.

Here is some useful info to get you started.
compustar-- applicant name ="Firstech"
scytek(galaxy,astra,asianwolf)- grantee code = "OAR" aplicant name="Precision Engineering"
lynx/airwolf-- grantee code="'QQH" and frequency= 447.475
DEI-- applicant name="Directed Electronics " grantee codes="EZS"&"CZ5"&"I5M"


And for all the hardcore junkies, you can lookup the schematics for most of the products, in most cases the complete schematics are given, what is usually missing is the contents of the main logic chip but that is fairly easy to figure out. Also if you want to make the transmitters yourself your gonna in some cases have to come up with your own modulation/demod technique.

Also make a note of the type of modulation used by the systems. Spread Spectrum is best, then comes FM which is better than FSK and then then finally ASK and then pure AM (im like 80 percent sure of the order of the last few).

 

Excellent post!.. this should be in the important topics...

 

Actually, you can get all of this info directly from the FCCs website... the ID number shouldn't be hard to find as FCC rules state that the ID should be printed right on the transmitter (usually a sticker on the back). If it's not there, it will also be in the manual.

 

right, i thought that was the fcc's site ,but also that would mean you need to have the item in hand, i was suggesting that people could use it as pre purchase research.


anyways, interesting thing i noticed was that most of the better two way systems that are out there ,are fairly close in terms of output but the ones that use spread spectrum dont even come close to the limits, the limit is 1watt where as they only use like single digit milliwatts like all the other non SS systems. (i might be wrong about numbers but the order of magnitude is about right)

This might mean you can legally "seriously " extend the range of the ss systems.

on a side note you got a PM MacGyver