Jump to content
Electronics-Lab.com Community

fm transmitter scematic required


Recommended Posts

happy new year  guys!
please help me.
i want to build a fm transmitter for radio transmission in my college campus and got so many schematics.but i m confused regarding their ranges.actually i need a stereo fm transmitter having a range of minimum 1 km (with in surrounding buildings ).frequency stability is also matters much.please send  me a fine tested circuit .

Link to comment
Share on other sites


  • 3 weeks later...

yeah but I was thinking that because the 1W amp needed 100mW to drive 1W out that with the 10mW or so that the micromitter has (without the attenuator) that I might be able to drive 100-200mW. Anyway i decided to return the micromitter kit and bought the EDM kit the is switchable between 10mW and 100mW which should be more than enough for what I need. From what I've read the signal quality is pretty decent.

Link to comment
Share on other sites

ok you are probably right , I was only going by what I read on the diy site.  They said it would put out 20mW but I read somewhere else someone posted that there must have been a typo and at most it would be 10mW.    In any case I think I will be happy with the EDM-TX-110EP I ordered Have you heard of it?

Link to comment
Share on other sites

I stumbled onto the EDM page while looking for info on the BH chips. I never bought one as I made my own circuit with a BH1417. I looked at their mod meter at one stage and was thinking of getting one but found a surplus meter on ebay. I have seen a lot of post on the EDM transmitter on various boards. Looks like a good tranmitter. You may want to read the reviews on part15us. This is a site dedicated to low power transmitters AM& FM http://www.part15.us/node/691 There is something on the EDM as well

Link to comment
Share on other sites

  • 2 weeks later...

yeah but I was thinking that because the 1W amp needed 100mW to drive 1W out that with the 10mW or so that the micromitter has (without the attenuator) that I might be able to drive 100-200mW. Anyway i decided to return the micromitter kit and bought the EDM kit the is switchable between 10mW and 100mW which should be more than enough for what I need. From what I've read the signal quality is pretty decent.


Was wondering if you could give us a report when you receive this transmitter?
Link to comment
Share on other sites


Was wondering if you could give us a report when you receive this transmitter?


I recieved my EDM transmitter last Wednesday.  It is an awesome little unit. I am so impressed with the sound quality. It really sounds awesome especially when I connect my cd player to it. Sirius Sat Radio sounds alot better too. Seems to have a really great pre-emphasis stage in the input. The treble sounds better and the base sounds better too. What I like the most is it's separate L-R input level POTs so you can fine tune your inputs for better stereo balance and you can adjust MPX value manually so you are capable of using all the the 75Khz deviation band of the FM signal. Anyone who gets this Tx will not be disappointed. The workmanship is excellent and support so far has been really good. fast email responses. You can purchase them through paypal. Once you purchase a unit from EDM they give you access to a private yahoo group which has lots of great info on such as homemade attenuators, antennas etc...

Anyone who wants more info , dont hesistate to contact me.
Link to comment
Share on other sites

using the stock whip antenna I did some preliminary range tests. The Tx was installed in the cab of my truck with the antenna running up and down the mirror which isn't the best placement for it but nevertheless I was very happy with the range I received.  using a fairly good quality FM headset I walked down the road and the sound was crystal clear up to about 300 feet after that I started getting some static and the occasional blank spots. On high setting I got crystal clear sound up to 500-600 and after that a bit of static and the occasional blank spot. Keep in mind that the Tx was in the cab of my truck with alot of metal around it.  I have made a custom 50Ohm coax and made a 1/4wave ground plane antenna and I expect the range to be better when I mount this antenna outside the cab of my truck.  I've read that on high setting I can get about 1/8mile.

Link to comment
Share on other sites

I researched the Ramsey model but they are about $60 more for a kit and about $100+ assembled. Second is the fact that EDM is also microprocessor controlled and has digital LED readout. If I can quote from their site

This is the only Compact, Multi-Channel, Digital-Display, Fully-Synthesized, Microprocessor-Controlled, Stereo FM Transmitter kit that we know of for under $100 (including S/H)!!


I found all the feedback I read on all the independant website was all positive. I was hard pressed to find anything negative about them. I also liked that EDM posted alot of their graphs and tests online. As a customer I felt re-assured that they were very open and honest by posting their specs online. This tell me that they have nothing to hide and not afraid to post their results publically.

Full Band operation: (87.7 - 107.9MHz) in 0.2MHz increments, on LED display
Frequency Stability: < 0.0005% of set frequency
Frequency Accuracy: < 0.001% error from set frequency
10mW (+10dBm) into a 50 Ohm load
100mW (+20dBm) unit also available
RF output is reduced 20dB while tuning with PLL un-locked
VSWR: Withstand 20:1 without damage (both models)
Low phase-noise
-90dBc/Hz @ 10kHz
-94dBc/Hz @ 20kHz
-104dBc/Hz @ 100kHz
Low spurious output: < - 50dBc
Low Residual FM: < 25Hz rms (Measured in a 300-3kHz Bandwidth)
Incidental AM: < 0.2%
Frequency Response: 20Hz - 15kHz
Level: Line level input via RCA type sockets (level adjustment on module)
Max Audio I/P sensitivity: < 100mVp-p (integrated limiter)
Distortion (THD): 0.2% with 1kHz tone at 75kHz deviation level (mainly 2nd, 4th)
Signal to Noise Ratio (SNR): > 60dB
Stereo Separation: Typical about 40dB
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
×
  • Create New...