Hello Part 15 Community,
I have recently installed a rangemaster on the roof of
my college. I was having serious problems before but
now I believe we are only having one serious problem.
Hello Part 15 Community,
I have recently installed a rangemaster on the roof of
my college. I was having serious problems before but
now I believe we are only having one serious problem.
We are able to get a clean RF signal but the audio is very
faint. You need to turn the recieving radio up to nearly
full volume to be able to hear it. I have tried both sides
of the adaptor with several different audio sources, the
output from the mixing board, a headphone output from
a mini-amp/mixer and the output from my iPod.
It is always too quiet, we have to crank the volume up
very loud on the mixing board to be able to hear it at all,
and the iPod's audio isn't audible at all.
I just read about a new 600 ohm balanced audio adaptor
that is powered with a gain control from Hamilton, I wonder
if this will work? Does anyone have any thoughts/comments?
Thank You
M.D.
Did you adjust the volume control inside the transmitter? I had the volume control set at 12:00, then I fine tuned the audio by adjusting the output of the limiter.
Frank
www.easthillradio.com
I am nearly 100% certain that the volume dial in the
transmitter is turned all the way up. I have tried it
at maximum both ways (counter clockwise and clockwise).
The reason I am not 100% certain is because it is a tedious
process to get onto the roof of the building and I have
to borrow a ladder from maintence, so I can't just hop
up and down.
I am almost certain the volume is turned up all the way
inside the transmitter.
Any other ideas?
What sort of cable are you using to get the signal out to the transmitter, and are you sure it's in good shape?
Daniel
The cable we are useing to get the audio to the transmitter
is 4 wire shilded cable. There are 4 wires inside but we
are only using two. Its not the type that Keith gave us because
the 100ft. we bought with the transmitter wasn't long enough.
This cable has been supplied by maintence (of the college)
and looks basicly ok.
I can go up to the transmitter tomorrow and try to get the
audio running through a new, short cable run and will use
my ipod as the audio source to eliminate the pretty long
cable run the audio has to go through now.
The audio cable is lying on top of a dryer vent for a while as it travels toward the station, then it goes down through the 4th floor and
then goes along the hallway atop the drop ceiling, around
some flourcent light fixtures and data cables, but this only
for a short while.
Do you lose audio volume as the wire goes along?
Also, can you use the volt-ohm meter to see if your audio
signal is strong at the end of the cable run?
Thanks
md
"Do you lose audio volume as the wire goes along? "
Yes, it's called attenuation. I might or might not be a factor for your application. Read more here:
www.epanorama.net/documents/audio/audiocable_length.html
and ridiculous amounts of wire knowledge here:
www.epanorama.net/links/wire_av.html
"Also, can you use the volt-ohm meter to see if your audio
signal is strong at the end of the cable run?"
Yes, if your meter can measure low voltage, low current AC, which is what your audio signal looks like to a meter.
Experimental broadcasting for a better tomorrow!
scwis,
what is a "normal" amount of audio voltage that
should be showing up at the end of the cable run?
Also, do you think if I were to put the test leads for
the the volt-ohm meter at the two parts of bare audio
wire where the adaptor attatches to the cable that runs
to the transmitter and then again at the end that it would
give me an idea of the % of power lost during the cable run?
finally, is there anything to prevent this attenuation or
to lessen it?
Thanks
md
Or you running those two wires as a "balanced low Z" audio line? Or one carries audio and the other carries the voltage from the power supply for the transmitter?
Balanced line is 2 wires carrying the audio inside a shield. Unbalanced is one line carrying the audio inside a shield.
If only one of the wires is carrying signal inside the shield, then losses over 100 ft can be considerable.
Secondly, is it at all possible that water could have gotten into the audio connection or cable at the outdoor end? That can really sap your signal with either balanced or unbalanced line.
Daniel
Great suggestion. Test the level at the output of your audio device (disconnect the long wire run from the audio source first, as that will affect the level), then test the level again at the end of the wire run. You'll have a better idea of what's happening.
Prevention? Well, it's physics, so you can't prevent physics but you can work around the problem. Either use a balanced line as Rattan describes above or use brute force with an additional amplifier to push the audio harder. Even with an amp, I imagine attenuation will roll off the higher freqencies so, you'll probably want to tweak your equalizer to compensate for that. A balanced line would be better, I think.
Experimental broadcasting for a better tomorrow!
Rangemaster transmitters have a 600 ohm balanced audio input. If you drive the transmitter with a 10K ohm audio output, the source will be loaded down very much like a direct short. Impedance matching would be imperative at this point; accomplished with an impedance transforming amplifier or a 10K to 600 ohm transformer. Low impedance to high impedance: good. High impedance to low impedance: Bad.
Marshall Johnson, Sr.
Senior Pastor, President
Rhema Christian Fellowship, Inc.
Rhema Radio - The Word In Worship
AM 1660 - FM 93.5
http://www.rhemaradio.org
I used a direct box between my limiter and the Rangemaster. My limiter used consumer level inputs and outputs and I needed to provide balanced audio to the Rangemaster. It worked great.
I'm in the process of rebuilding the studio and all my equipement will have 600 ohm balanced outputs so I can feed the Rangemaster directly without a direct box.
Frank
www.easthillradio.com
Hi Frank, Could you clarify?
WDCX AM1610 Part 15
John
Owner-Operator-Chief Engineer-Program Manager
It's more properly called a match box or an interface amplifier. Unbalanced in at -10 db, balanced out at +4 db. Here's one at BSW: http://www.bswusa.com/proditem.asp?item=MB15.
Frank
www.easthillradio.com