RC Radios, Transmitters, Receivers, Servos, gyros Discussion all about rc radios, transmitters, receivers, servos, etc.

AM vs FM

Reply

Old 01-09-2005, 02:19 AM
  #1  
HVAC25000
Junior Member
Thread Starter
 
Join Date: Sep 2004
Location: Pine Valley, CA
Posts: 19
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default AM vs FM

Besides about 40 dollars, could someone explain to me the difference between AM and FM?

Thanks
HVAC25000 is offline  
Reply With Quote
Old 01-09-2005, 10:24 AM
  #2  
tc3mafia
Member
 
tc3mafia's Avatar
 
Join Date: Jan 2005
Location: south, FL
Posts: 55
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: AM vs FM

can someone also explain the difference between a 27 mhz and 75 mhz? does it allow you to control the car from a farther distance?
tc3mafia is offline  
Reply With Quote
Old 01-09-2005, 10:42 AM
  #3  
Rodney
Senior Member
 
Join Date: Dec 2001
Location: FL
Posts: 7,769
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: AM vs FM

AM and FM are just describing the type of modulation the RF is encoded with. AM is amplitude modulation where the instantaneous strength or magnitude of the signal is modulated or varied from zero to maximum for that transmitter. FM puts out a constant strength or magnitude signal and the encoding is done by varying the frequency a small amount about the center frequency. Either type works well for the way RCers use them and each has some advantages over the other. For our puposes, FM usually provides more resistance to minor interferance. As to tc3mafias question, frequency has very little to do with range over the span you are asking about. Receiver sensitivity (usually stated in DB/Meter) is the prime factor for range, the smaller number is better. This is assuming the power output of the transmitter is the same for all the frequencies. Also selectivity is important but that is a number most manufactures don't publish and some of the less expensive units suffer in both respects.
Rodney is offline  
Reply With Quote
Old 01-09-2005, 02:41 PM
  #4  
HVAC25000
Junior Member
Thread Starter
 
Join Date: Sep 2004
Location: Pine Valley, CA
Posts: 19
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: AM vs FM

Thanks for the info Rodney. I suppose I'll go with FM (I've had 27 AM in the vehicle in question for the past 4 years, and on 4 seperate occasions, I have lost total control at full throttle...).
HVAC25000 is offline  
Reply With Quote
Old 01-09-2005, 03:56 PM
  #5  
MO_Radio_Tech
Senior Member
 
Join Date: Jun 2002
Location: MO
Posts: 337
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: AM vs FM

The advantage that 75 mHz has over 27 is that the 27 mHz band is noisy. 27 tends to have more interference problems and less range as a result.

A big source of trouble is the CB'ers at 26 mHz. Some truckers illegally modify and crank up their radios, splattering 27 mHz.

I used to be one of those loud CB'ers.
MO_Radio_Tech is offline  
Reply With Quote
Old 01-10-2005, 10:25 AM
  #6  
mrbigg
My Feedback: (21)
 
mrbigg's Avatar
 
Join Date: Oct 2004
Location: Streator, IL
Posts: 4,780
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: AM vs FM

you also have all the cheapo walmart toy rc vehicles on 27 too.
mrbigg is offline  
Reply With Quote
Old 01-11-2005, 01:29 AM
  #7  
MO_Radio_Tech
Senior Member
 
Join Date: Jun 2002
Location: MO
Posts: 337
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: AM vs FM

yes you do
MO_Radio_Tech is offline  
Reply With Quote
Old 01-11-2005, 02:00 AM
  #8  
HVAC25000
Junior Member
Thread Starter
 
Join Date: Sep 2004
Location: Pine Valley, CA
Posts: 19
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: AM vs FM

Well I'm taking a trip to my LHS tomorrow to pick up a new FM radio system.

Thanks for the help, everyone!
HVAC25000 is offline  
Reply With Quote
Old 01-11-2005, 10:35 AM
  #9  
laryboy
My Feedback: (2)
 
Join Date: Jul 2003
Location: wilmington, MA
Posts: 825
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: AM vs FM

rodney.......i am sure you know that receiver sensitivity is measured in dBm...decibels below 1 milliwatt.
laryboy is offline  
Reply With Quote
Old 01-11-2005, 04:10 PM
  #10  
Rodney
Senior Member
 
Join Date: Dec 2001
Location: FL
Posts: 7,769
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: AM vs FM

Lazyboy, thanks for the correction. You are correct.
Rodney is offline  
Reply With Quote
Old 01-11-2005, 04:38 PM
  #11  
laryboy
My Feedback: (2)
 
Join Date: Jul 2003
Location: wilmington, MA
Posts: 825
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: AM vs FM

lazyboy ? LOL
laryboy is offline  
Reply With Quote

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Thread Tools
Search this Thread

Contact Us Archive Advertising Cookie Policy Privacy Statement Terms of Service