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View Full Version : 200W Vastelec Transmitter reception problems



crperryjr
10-24-2008, 03:29 PM
Hey everyone,

I was wondering if anyone is having the same issues I am regarding the 200mW Vastelec FM transmitter.

First, it is working. Much better than my old Belkin Mod'd transmitter I used last year, but I'm trying to fine tune it to at least a semblance of commercial quality.

The transmitter assembly is set up in my workshop which is about 30 feet from the road where people will be watching my show. I have a DIPOLE antenna I made of the correct length (89.3 FM=1.597m) tucked up in the roof of the workshop that is made from some stiff wire (coat hangers) and connected to the transmitter via a shielded coax cable. (Center wire to upper 0.799m, Sheathing to bottom 0.799m of anntena.) The antenna and FM transmitter are about 10 feet apart on seperate floors of my workshop. The antenna is about 16 feet in the air at it's highest point. I have mod'd the FM transmitter to emit RDS and that is working great. The whole deal is powered from the 12v side of my computer's power supply.

My issue is, on a MONO type FM receiver, (like a portable radio with only the one speaker in it.) the sound quality is excellent, and I have no hums, pops, or anything. Very happy with it. But on a stereo radio, like in my car or truck, the bass is garbally, and it sounds as though the music is "overamp'd" for lack of a better word. There is also a slight power hum when no music is playing. I've tuned the RDS down, so I know there's no noise coming from there. (You can tell the difference when the RDS is cranked to high.)

I've tried to modify my radios in my vehicles to find the best sound, and it seems if I turn the bass all the way off, it sounds better. Not great, but better. And there is still that power hum when nothing is playing. And I really don't want to put a sign out on my lawn- "Tune to 89.3, and turn off the BASS and set to mono." :)

The music I'm using (lots of different styles and formats) sounds good on my computer speakers, and on the mono FM receivers, so I don't think it's the music, nor the volume output of my sound card to the transmitter. (I tried lowering and raising that as well. Volume changed, but no difference in quality.)

Any ideas on why such a difference between Mono and Stereo receivers?

Thanks much for your help!

ctmal
10-24-2008, 03:43 PM
By any chance do you have another computer that you could plug the sound into(or maybe an mp3 player to test)? I didn't have the same issue as you but when I first plugged mine into a soundblaster sound card the audio was terrible. I moved it to the generic onboard sound card and everything sounded great after that.

crperryjr
10-24-2008, 03:45 PM
I'll try that right now and let you know. Thanks for the quick reply!

Edit: I just tried it with my daughter's mp3 player, and it's even worse on the vehicle stereos. (But still just as good on the mono radios.) So I think we're on the right track. Something changed... Any other ideas?

phenagan
10-24-2008, 04:14 PM
Have you tried switching the balance between the speakers on the stereo receivers - i.e. listen to the right channel by itself and then the left? May be an issue on only one channel that is being neutralized by the mono receiver's combining the two sides.

phenagan
10-24-2008, 04:17 PM
PS - I assume you meant 200mW rather than 200W? If it's 200W, you're swamping your radios (not to mention very likely to have the Feds on your door!) ;)

rstehle
10-24-2008, 06:13 PM
You can try adding ferrite beads to the power and audio cables.

crperryjr
10-24-2008, 06:15 PM
You're absolutely correct. 200mW it is. I guess it shows that you can never proof-read a post enough. :) <Looks over shoulder for FCC.>

Well, the good news is, I found the problem, and solved it!

Phenegan, you got me on the right track, and I thank you. I've been chasing my tail for days on this one.

My sound card has a really wierd application that lets you set up virtual 5.1, and it was turned on. Once I turned that off, and changed some other settings, (Like set to "desktop speaker" instead of "surround sound", and no virtual concert hall effects) The sound is now crystal clear on the vehicle stereos. (Still a little high pitched whine. But I'm the only one in the family that seems to notice it.) I think that could be related to the flourescent lights in my workshop.

Thank you again for your help.

omzig
10-24-2008, 06:26 PM
(Still a little high pitched whine. But I'm the only one in the family that seems to notice it.) I think that could be related to the flourescent lights in my workshop.A definite possibility. I had the same problem and eventually determined that it was caused from two things. One was fluorescent lights and the other was a nearby desktop computer that didn't have its cover on. As soon as I put the cover back on the computer the noise went away.

XmasInGalt
10-24-2008, 06:27 PM
Did the hum go away also?