I downloaded the manual on the CAT-200 and looked....
The CAT-200B has the ability to do de-emphasis, but, it's not as simple
as flipping a dip switch; you must install a capacitor for adding
de-emphasis per port.
C10 is for RX#1 and C11 is for RX#2. These parts are listed as
"optional" on the schematic, and like many things from CAT, they don't
tell you the damn value...
I also looked at the audio chain... I see they have taken my advice
for the output coupling capacitor value, but the input cap is too
small. It's a .1, and it feeds a 10K pot, and the wiper feeds a 10K
input resistor. Depending on the setting of the input control, this
could result in a .1 feeding 5K shunt resistance. Doing the math, this
equates to a low end roll that could be as high as 318 Hz. In my
opinion, a .1 uF cap is TOO SMALL. I'd change it to a .47 uF bringing
the corner to 67 Hz.
My recommendations:
Change C8 and C9 to something larger than .1uF I recommend nothing
smaller than a .47 uF _Non-Polarized_ capacitor.
Install C10 or C11 with (depending on which port of the controller you
are using and what audio is being delivered) whatever CAT tells you to
install for de-emphasis. I recommend a .05 uF which puts the
de-emphasis corner at 96 Hz.
7 years ago many folks complained about the terrible audio on CAT's
high-end controller, the CAT-1000. Jim Hartzell, Jay Farmer and I did
some research and created the following article:
http://www.repeater-builder.com/cat-auto/cat-1000-audio.html
The result was CAT changed the values of the capacitors in their
production to values that are similar to those suggested in the article.
So, now we find out you only get the /good audio chain/ *if* you buy the
more expensive controller. What a crock....
Let us know how you make out, Jim...
Kevin Custer
Jim Brown wrote:
This may be out in left field, but I have built several repeaters
using the CAT300 controller (not the CAT200) and the 300 had no way to
de-emphasize the discriminator audio. I have used an external series
15 K and shunt .22 cap to supply the discriminator audio to the CAT300
and it sounds great.
Maybe one of your repeaters does not have the de-emphasis circuit
installed, or if it is available on the CAT200, maybe it is not set in
the right mode.
73 - Jim W5ZIT
*/Eric Lemmon <[EMAIL PROTECTED]>/* wrote:
Subject: [Repeater-Builder] Micor Audio on VERY WEAK SIGNALS
Hi Guys,
A question for the MICOR fans that may have experienced a similar
dilemma I am having with one of our three Micor Repeaters. All three
are Micor VHF Bases, converted to repeater duty using the information
I obtained from this group. All three have Cat 200 Controllers and
unless I have missed something all are wired the same.
When a weak signal, like from a portable radio or a station far away
comes in I have quite a bit of background (white noise). I have
noticed that if I listen to the audio from the Micor Speaker, it
appears to me that much of the white noise is gone and the signal is
much more understandable. Now this audio test is being performed with
the TX on, so I have determined that there is no noticeable desense.
The first thing I did was check the input audio into the Cat200 and
make sure the voltages were set to the book, which they were. I have
also taken into consideration that the Micor Speaker may reproduce the
audio better than the HT or Mobile, but there is still enough
difference that I wish the repeater audio, on weak signals only,
sounded as good as the Micor RX direct to the speaker. I am using
Discriminator Audio on all the repeaters and have the controller set
properly for that. The only way to explain a weak signal is the
background seems to be pumped up. Any ideas I will look into on my
next trip to Pa.
73 Jim KA2AJH Wellsville, NY
