View Full Version : FM100B Noise?
10-21-2002, 09:29 PM
Hi. A few days ago, I got done building the FM100B tx. I'm pretty satisfied with it, but without modulating any audio, or low audio levels, I hear some pretty noticeable hiss, louder than my FM25A tx. This is not just through one rx, but through any rx from a portable radio to a car radio. Is this normal, or could there be a problem somewhere? It's ok if it's normal, but if it isn't, then I would like to find some may to "improve" it.
How high do you have the power set. If the power is real low, the receiver might not be getting enough signal for a full quieting stereo carrier.
10-21-2002, 10:54 PM
The power output is set to full power assuming about 25mw. I did slightly turn down the power to see if the receivers were overloaded, wasn't that. I switched to an external antenna on the roof (with the FMLP1 filter inline) a little better, but still has the slight hiss.
10-22-2002, 05:43 PM
do you turn your receiver volume all the way up?
I have 2 FM100B, I can hear a little bit hiss when I turn my walkman volume all the way up
since FM100B employs fully-regulated power supply, the hum/static is almost inaudible
if you hear a lot of hiss, even under normal volume, it's time to check your grounding, and try different receiver to find out (walkman is the best bet)
10-22-2002, 06:20 PM
Yes, with any receiver (big home stereo system or car, to a walkman) with the volume all the way up, some hiss is present.
10-22-2002, 07:56 PM
because mine is
since the SN is around 40dB, a little bit hiss is heard when you turn your receiver volume all the way up
That would have been my next question, regarding the volume. I think Matt's answer is on target
vBulletin® v3.8.5, Copyright ©2000-2013, Jelsoft Enterprises Ltd.