Connecting two NAV/COM radios to a single KI-203 nav indicator

I've nearly completed rewiring an RV-8, but am left with one final problem. There are two KX-155 nav com radios, a KA-24 audio panel and a single KI-203 navigation indicator. There is a single VOR antenna in the port wing-tip. The NAV component has only ever been used for VOR in this aircraft and hence no glide-slope antenna. (I hasten to add this is not my aircraft!!). The single antenna output is duplexed to the two radios via a little duplex box.

I understand how to hook up the COM aspect of the radios via the audio panel. Also the what I presume is the audio component of the VOR signal from the radio to the audio panel. What I don't understand is how the navigation indicator receives feeds from two radios and hence inputs fromtwo antennae but knows which antenna signal and radio to utilise? IS this something that should be obvious? What am I missing?

Be really grateful for some help - I need to complete this job by next Friday......

Thanks

Chris

PS can someone please confirm that you can't use a VOR antenna for glide-slope, or that it at least would be very degraded?

A switch is needed

I don't think you are going to be able to do that without using a multiple pole relay switch. They make them but it is a complicated wiring job.

Vic

Actually this is quite easy.
For VOR/LOC, you need to switch 3 lines - Nav Composite (a single-core screened cable), ILS energise, and Nav switched power. The indicator ground is common so can go to a local chassis ground with the radios, and lighting is optional from the panel lighting bus, but not connected to the radios. A small 4-pole double-throw switch is all that's required.

Whilst you can derive glideslope from a Nav antenna using an appropriate coupler (Comant CI1125 will give 2 navs and 2 glideslopes from a single antenna) this isn't needed with the KI203 as if doesn't have a glideslope bar or flag. If you do want glideslope you'll need a KI204 indicator (and a version of the KX155 with integral glideslope receiver) and switch 4 additional lines, so a relay box is then needed.

Harry, Vic, thanks, that's really helpful. My mistake - KI-204; it definitely has a glide slope bar.
Since there was definitely no multi-pole switch or relays when I took it all apart, I think the assertion from the owner that both radios provided VOR to the indicator must be in error.

Chris

Technical note: Most antennas designed for one frequency also work well at the odd harmonics. The GS uses frequencies that are 3 times higher than the nav frequencies, so a localizer antenna also works well for GS.