Thanks for the research Kevin. This Cat 200 is a good one to start with. I did not do the original install, so I will check the values. Mr. Lightning as not been good to this site, so this is the 3rd repeater the controller has been on. The other two were Micor Mobiles. Hope to get the associated link up before winter and I will make these modifications and post the results.
73 JIM KA2AJH _____ From: [email protected] [mailto:[EMAIL PROTECTED] On Behalf Of Kevin Custer Sent: Sunday, November 04, 2007 8:45 AM To: [email protected] Subject: Re: [Repeater-Builder] Micor Audio on VERY WEAK SIGNALS 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 <http://www.repeater-builder.com/cat-auto/cat-1000-audio.html> -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 <mailto:[EMAIL PROTECTED]> <[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
