Hi folks,
I have a Uniden BC125AT and a BC346XT. For an upcoming airshow I wanted to connect both scanners to a pair of noise cancelling headphones so that I could have the output from each scanner in a separate ear. I thought this would be easy (and cheap), requiring only a 'Y' cable splitter with two 3.5mm male mono inputs and a 3.5mm female stereo output.
Before buying the 'Y' splitter I thought I'd search in the RadioReference forums to see if other people had rigged up similar multi-scanner setups, and of course they had. This provided plenty of discussion and ideas to digest. I quickly realised that using a simple 'Y' splitter was probably not a good solution and at the very least I'd need an isolating transformer so I can connect both scanners to a common ground safely.
Whilst products such as the passive ART DTI seem perfect for this application at first glance, closer inspection reveals that most isolation transformers are for DJs and are designed to work with impedances of 600 ohms and upwards. This makes them unsuitable for use with low-impedance headphone sockets. This is the first problem.
The next problem is the outputs. For some reason Uniden use a stereo output on the BC346XT and a mono output on the BC125AT. This is presumably because the BC346XT can pick up stereo FM broadcasts. Properly converting a stereo feed to mono requires yet more dedicated electronics (and cost). Something like the Monacor SMC-1 seems to be the best solution as I've read that using a cheap stereo-mono adaptor can potentially result in high current draws under certain circumstances making them unsuitable for battery operated devices with low impedance outputs. Whilst you could just connect one channel (i.e. either just the 'L' or 'R' channel) to turn the output of the BC346XT into a mono source, I didn't want to live with one channel missing as I wanted to use the rig for listening to the airshow FM radio station.
As an aside, I didn't realise that the BC346XT has a stereo out until I started doing the research for this little project - I'd always assumed it was a mono plug. Up until now I've been using my BC346XT with a mono cable, so may have already damaged the unit by shorting one of the stereo channels.
This project was starting to look very complicated (and expensive) and I was just about to give up when I read somewhere that you don't generally need an isolating transformer if the impedance levels of the inputs are the same, which in my case they are (both 32 ohms). Potentially this means that I might be able to go down the 'Y' splitter route after all. So this brings me to my question. Firstly, am I right in thinking I can simply connect these together directly if they have a similar impedance? Secondly, has anyone got any thoughts on the stereo to mono problem? Any help or potential solutions would be greatly appreciated.
I have a Uniden BC125AT and a BC346XT. For an upcoming airshow I wanted to connect both scanners to a pair of noise cancelling headphones so that I could have the output from each scanner in a separate ear. I thought this would be easy (and cheap), requiring only a 'Y' cable splitter with two 3.5mm male mono inputs and a 3.5mm female stereo output.
Before buying the 'Y' splitter I thought I'd search in the RadioReference forums to see if other people had rigged up similar multi-scanner setups, and of course they had. This provided plenty of discussion and ideas to digest. I quickly realised that using a simple 'Y' splitter was probably not a good solution and at the very least I'd need an isolating transformer so I can connect both scanners to a common ground safely.
Whilst products such as the passive ART DTI seem perfect for this application at first glance, closer inspection reveals that most isolation transformers are for DJs and are designed to work with impedances of 600 ohms and upwards. This makes them unsuitable for use with low-impedance headphone sockets. This is the first problem.
The next problem is the outputs. For some reason Uniden use a stereo output on the BC346XT and a mono output on the BC125AT. This is presumably because the BC346XT can pick up stereo FM broadcasts. Properly converting a stereo feed to mono requires yet more dedicated electronics (and cost). Something like the Monacor SMC-1 seems to be the best solution as I've read that using a cheap stereo-mono adaptor can potentially result in high current draws under certain circumstances making them unsuitable for battery operated devices with low impedance outputs. Whilst you could just connect one channel (i.e. either just the 'L' or 'R' channel) to turn the output of the BC346XT into a mono source, I didn't want to live with one channel missing as I wanted to use the rig for listening to the airshow FM radio station.
As an aside, I didn't realise that the BC346XT has a stereo out until I started doing the research for this little project - I'd always assumed it was a mono plug. Up until now I've been using my BC346XT with a mono cable, so may have already damaged the unit by shorting one of the stereo channels.
This project was starting to look very complicated (and expensive) and I was just about to give up when I read somewhere that you don't generally need an isolating transformer if the impedance levels of the inputs are the same, which in my case they are (both 32 ohms). Potentially this means that I might be able to go down the 'Y' splitter route after all. So this brings me to my question. Firstly, am I right in thinking I can simply connect these together directly if they have a similar impedance? Secondly, has anyone got any thoughts on the stereo to mono problem? Any help or potential solutions would be greatly appreciated.
