I am using a CAT 200B controller on a 222 mhz repeater made from a Micor mobile that I converted to 222 mhz and a UHF GE Delta-s for a remote base radio. I am using discriminator audio from both radios with the 0047uf C10 and C11 installed, everyone says that the repeater audio is excellent. ----- Original Message ----- From: Bob M.<mailto:[EMAIL PROTECTED]> To: [email protected]<mailto:[email protected]> Sent: Sunday, November 04, 2007 9:14 AM Subject: Re: [Repeater-Builder] Micor Audio on VERY WEAK SIGNALS
On the CAT200B manual I have, page 6-2 tells all about adding C10 and/or C11, and the value they supply is 0.0047uF. Don't chastise them so hastily. Engage eyes before shifting fingers! They probably designed the audio stage to reject sub-audible tones. The audio response is perfectly adequate when driven from a de-emphasized audio source and feeding a transmitter that will follow it with pre-emphasis. In my case, using MaxTracs, I just use the constant amplitude Headset Audio available on the front panel RJ45 MIC jack, and feed audio into the MIC input on the same jack. As both of these already have sub-audible audio filtered out, the controller has no problem with the audio. Using a 0.05uF cap for de-emphasis will likely make it take effect way too early, considering everything else in the system. As was mentioned earlier, if the Micor circuitry provides flat audio in and out, it is up to the person doing the controller integration to add the appropriate pre- and de-emphasis. Bob M. ====== --- Kevin Custer <[EMAIL PROTECTED]<mailto:[EMAIL PROTECTED]>> wrote: > 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<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]<mailto:[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 __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com<http://mail.yahoo.com/>
