On Fri, 7 Sep 2012 13:58:38 +0000, ULLS
wrote:

I am trying to receive an am signal well below ground level in a metal
server room, there is a coax feed up to the roof which I used and
attached the standard wire loop that was supplied with the tuner,

Numbers please...
What make and model tuner?
What loop antenna?
What type of coax cable?
How many feet of coax?

The loop antenna that comes with most home hi-fi receivers is resonant
in the BCB (broadcast band). If you add coax cable or twinlead to the
loop, it becomes detuned and starts looking more like a short circuit.
The barrier strip BCB connections on the back of the hi-fi are
intended for a "long wire" antenna, and a decent ground connection.
The required BCB antenna impedance is probably much higher than your
coax cable, which means you'll need to build a matching network if you
plan to use coax cable to the roof. You might do better with just the
longest wire you can find that makes it up to the roof and beyond, if
it doesn't pickup RFI/EMI from the servers.

If you're plugged into the "F" connector found on the back of some
hi-fi's, that's for FM band reception, not BCB.

however when I attempted to tune into some stations I could only pick up
a couple of local stations and wasn't able to receive the ones I was
hoping for.

That's because the loop antenna is acting more like a short than an
antenna.

when I dialed in the desired frequencies,

Why would you want to hear BCB AM radio inside a server room?

all I was
receiving was a tone, the tone changed in frequency/pitch depending on
the tuners frequency.

If it's anything like the server farms that I occasionally visit, the
RFI/EMI from the high power switchers, servers, and thousands of clock
oscillators is sufficiently high that I couldn't even get a pair of
cheap FRS/GMRS radios to communicate across the building. I suggest
you consider streaming audio as a better alternative.

To check that I could receive the stations I took
the tuner to the roof and attached the antenna directly and sure enough
I could pick up the desired stations.

Yep. You probably connected the loop directly to the unspecified
model radio. Try it again with an approximate length of unspecified
coax cable and it should fail similarly to your indoor test. Also
note that you're now outside what I suspect is a shielded room, which
should improve reception. For entertainment value, try making a cell
phone call from insider the server room.

My thoughts are that the coax is
affecting the signal in some way, perhaps picking up electrical noise?

Yes to both questions.

any advise would be appreciated.

Long wire antenna or switch to streaming audio.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558