Transmission1

Can a condenser microphone system that requires 48V phantom power be used with a Yaesu FT-450D?

Sure, but you have to use phantom box or any other 48V source.

I was not certain that the 48V from the phantom box does not put any voltage into the radio via the leads and just powers the microphone or have any issues with the 5V that the radio mic socket puts out.

Nah, it have separation capacitors.
Chris

If the radio has 5V superimposed on the audio line for unbalanced condensers, there is an additional concern. Phantom powering needs balanced audio as in most professional condensers. How will you convert the balanced audio to unbalanced. If you short pins 1 and 3, or 1 and 2, this can upset many phantom power units with XLR in and out. Most have blocking capacitors, but not by any mean all. Dragging one of the two hot lines down to deck to unbalance the system to work in a comms context might cause some problems - not nasty ones usually, just poor or no proper output from the mic, which gets one of it's balanced lines shorted. Worth testing and if it works, fine - but don't be surprised if it doesn't. Ideally, a transformer to unbalance the audio would be the best bet, then the phantom power unit, then the mic.

http://www.nu9n.com/transceiver_connections.html
and http://www.nu9n.com/tx.html#Audio_Cables

Not safe for work has blocked those links - what are they? The reason reported is
Juniper Networks Firewall has blocked the URL: 192.168.1.42(51056)->72.29.72.224(80) www.nu9n.com/transceiver_connections.html CATEGORY: Enhanced_News_and_Media REASON: BY_SITE_REPUTATION

Hang on - fiddled it with the phone. However, while the content is useful - it doesn't address the problem of phantom power.
Plenty of balanced to unbalanced ideas with and without transformers, but getting rid of +5V powering and adapting to 48V phantom is much trickier - well, capacitors to block critically, but still a transformer is the sensible method to provide isolation - which might also help reduce RF issues down the cable.

I have abandoned this idea as it will not work so this kit will be moved on, I am sticking with the Heil GM4. Thanks to all.

PS. I never click on or open links posted up unless there is an accompanying explanation as to what that link leads to or opens up.

No idea why it is blocked
NU9N site is best one with great info about ssb audio.
You can use some web proxy if ur too afraid to open it xD
Chris

p.s. GM4 sound like little girl speaking to tin can. Terrible audio, but it is HEIL.