I'm thinking of getting the following to scan & record wireless mikes at weddings

:: Uniden Australia :: (http://www.uniden.com.au/AUSTRALIA/p_ubcd396xt_index.asp)

I have constant problems getting access to the receivers/ PA's that are used and I want better sound than an ambient mike.

My hope is that I can use this unit to scan & find the frequency on the mike that the celebrant or venue has and record that.

any experts out there that can confirm my theory (desperate hope)

Radio mic frequencies now fall into the 590-694 Mhz band approx and that is a frequency band that receiver doesn't scan on.....
Scanners will often not work with radio mics as most brands have a unique coded squelch to make them work. ie; sennheiser TX wont work with a sony RX.
Radio mic TX - RX need to be in matched sets..........

Good thought but 99.9% chance it WON'T work for you.....

I thought in Aust it was between 520 - 820.

most venues have systems that are god knows how old and every one is different (and the staff have now idea how to use them).

there must be something that can scan all frequencies

Australian users of wireless microphones need to be aware of this stuff:

Wireless microphones | ACMA (http://www.acma.gov.au/theACMA/Newsroom/Newsroom/Media-releases/wireless-microphones-2)

More information is available in links within this page above.

I would think it unlikely that you would even have a good chance at FINDING wireless mics, much less actually RECEIVING them with enough quality for video production. I would NOT consider this even a long-shot possibility.

The coverage of the scanner is full of holes because it is optimized for "land-mobile" (commercial/government 2-way radio) bands. That does not bode well for reasonable expectation of finding various wireless mics.

Even if the scanner DID cover the frequency of the wireless transmitter, chances are that the scanner is optimized for narrow-band FM which is not compatible with most wireless mics which are wide-band, (at least compared to typical land-mobile equipment).

It is not reasonable to expect that ANY receiver can properly operate with a wireless transmitter except for the model(s) designed by the manufacturer. There are a variety of subtle and significant differences between wireless mic systems. It would be unusual to find wireless mic transmitters and wireless mic receivers from different manufacturers or even different models of the SAME manufacturer that work properly together.

Its easy enough to find the frequency, I use one of these RF scanners to set up radio mic systems.. But they ONLY give a visual display.
RF Explorer : Seeed Studio Bazaar, Boost ideas, extend the reach (http://www.seeedstudio.com/depot/rf-explorer-m-22.html?ref=side)

The coded squelch for different types of systems will be the problem for a reciever.....

For example I can run a Sony radio mic AND a Sennheiser Radio mic on exactly the same frequency at the same location at the same time but as each have a different code there is NO intermodulation... Not ideal I know but I have done it.

In Australia the 694-820MHz band will no longer be used for radio mics, this frequency band is going to be used for 'mobile devices' such as mobile phones and tablet pc's in 2015
Those old systems in churches etc will need to be replaced to the new allocated frequency space.