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: Repeater-Builder@yahoogroups.com
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
