Hello again Ian I've also tried a decoder with a 4 MHz crystal and it still heterodyned. Get a tunable decoder and your troubles will be solved.
What I found was if I turned up the TX CTCSS encode, the decoder activated and held up the receiver which held up the transmitter etc. We also had a ~ 1KHz whistle, probably the receive signals or TX were off frequency by that much. Peter VK2ZTV also has had the same problem with FM-828's Regards Don vk2zcz ----- Original Message ----- From: Ian Wells To: [email protected] Sent: Wednesday, March 03, 2010 3:12 PM Subject: Re: [Repeater-Builder] Adapting ctcss decoders to maxon pm150 From the manual it says it uses a 4 meg crystal Thank You ,Ian Wells Kerinvale Comaudio, 361 Camboon road, Biloela.4715 Ph 0749922449 Mb 0409159932 Hm 0749922574 Fx 0749922767 www.kerinvalecomaudio.com.au -------Original Message------- From: Don Crutcher Date: 3/03/2010 3:04:49 PM To: [email protected] Subject: Re: [Repeater-Builder] Adapting ctcss decoders to maxon pm150 Hello Ian IF your repeater is a UHF and the CTCSS decoder has a 5 MHz crystal oscillator, it will mix with the transmitter and give a signal at the receiver frequency 5 MHz lower (in Australia RX 433-435 TX 438-440 MHz) This a is a common occurrence with UHF Philips FM-828's. The fix is to use a tuneable CTCSS decoder and not use the one with a crystal oscillator in it. Been there and done that. Took years to find out why we had a whistle in the receiver (heterodyne). Regards Don vk2zcz ----- Original Message ----- From: Ian Wells To: [email protected] Sent: Wednesday, March 03, 2010 2:48 PM Subject: [Repeater-Builder] Adapting ctcss decoders to maxon pm150 Hi guys .I was looking at adapting a midian tds-1 to a maxon pm150 but we end up with feedback problems when used in repeater . Can anyone suggest ideas to give rf protection to the decoder chip .I came up with shielded cable between the board and the chip And to install the chip in a metal case on near the radio .or mounting it as close to the rf motherboard as possible but I don't think It will fit under the lid .The reason we would like to use the tds-1 is that the radio has to unmute before it decodes And I would like it to decode before the signal opens the mute .This improves the speed the repeater opening up On a valid signal . Thank You ,Ian Wells Kerinvale Comaudio, 361 Camboon road, Biloela.4715 Ph 0749922449 Mb 0409159932 Hm 0749922574 Fx 0749922767 www.kerinvalecomaudio.com.au
