My Fm Transmitter Query - diyAudio
Go Back   Home > Forums > General Interest > Everything Else

Everything Else Anything related to audio / video / electronics etc) BUT remember- we have many new forums where your thread may now fit! .... Parts, Equipment & Tools, Construction Tips, Software Tools......

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 4th September 2005, 06:02 AM   #1
diyAudio Member
 
Join Date: May 2005
Location: Mumbai
Default My Fm Transmitter Query

Hello friends.

i have a 1WATT FM Transmitter schematic, to which i design a PCB using Express PCB soft..

at the test, transmission clairity is very good but only for an OVER THE AIR distance of 50-55 mtrs max.. surely much less than my expectation of around 500-600 mtrs atleast...

i used a dipole antenna for transmission with a decent RG8 cable. And the class C amplfier 2N3866 doesnt disspiate significant amount of heat. using a scope i observe no amplification of the osc. freq. arcoss its o/p.. can anyone suggest some modifications to be to the design..

i have posted the blurred schematic of my Tx.. I feel the need for greater inductance across Class C biasing.. and removing Trimmer 2; the one just before the Tx o/p..

Please advice..


________________
Prasanna.

Expectation leads to disappointment...
More expectations lead to more disapoinments.
Attached Images
File Type: jpg xmitter.jpg (67.6 KB, 140 views)
  Reply With Quote
Old 4th September 2005, 07:42 AM   #2
diyAudio Member
 
Join Date: Mar 2003
Location: Willmar, Minnesota
What are the element lengths of your dipole antenna? Is the antenna near anything which might detune it? Are you sure your output impedance matches the antenna's input impedance?


-=Randy
  Reply With Quote
Old 4th September 2005, 08:03 AM   #3
diyAudio Member
 
Join Date: May 2005
Location: Mumbai
Sir,

The total dipole length is around 2 meters (1 + 1 mtr). Impedance of the cable is 75 Ohms, as rated with the o/p impd. of the transmitter.. The tx. is tuned to freq. of 102.3 MHz.

And if i use a simple 100cm aerial, then too the range is around 15-20 meters.. not much diff. as compared to the dipole range..

________________
  Reply With Quote
Old 6th September 2005, 08:12 AM   #4
diyAudio Member
 
Join Date: May 2002
Location: Switzerland
Some thoughts: Wavelength at 100 MHz is 3 meters approx so a half-wavelength dipole is 1.5 meters and a quarter-wavelength aerial is around 75 cm.

When using the dipole then use is vertically, since your receiver's antenna is most probably also vertically polarised.

Have you ever checked the output power of your TX into a resistive load ?

Regards

Charles
  Reply With Quote
Old 6th September 2005, 08:49 AM   #5
diyAudio Member
 
TwoSpoons's Avatar
 
Join Date: Oct 2004
Get yourself a VSWR meter so you can tune your antenna properly.
  Reply With Quote
Old 9th September 2005, 12:13 PM   #6
diyAudio Member
 
Join Date: May 2005
Location: Mumbai
Quote:
Originally posted by TwoSpoons
Get yourself a VSWR meter so you can tune your antenna properly.

Could you elaborate more on that pls..
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

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
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
PC interferes with FM transmitter Vermonter Everything Else 17 19th February 2009 12:53 PM
FM transmitter / PA Studio1 Tubes / Valves 4 17th July 2008 01:25 PM
My sub is a radio transmitter. mashaffer Subwoofers 6 7th April 2006 07:08 AM
FM transmitter kamathajit2002 Digital Source 2 3rd January 2006 06:01 PM


New To Site? Need Help?

All times are GMT. The time now is 03:13 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2