On 9/10/2012 5:35 AM, ULLS wrote:
Thanks for all your responses!

First off, I am attempting to auto switch/scan between two frequencies
on AM. I have FM and internet streams sorted. The tuner is a Cambridge
Audio hifi tuner with an RS232 interface for scanning. I don't recall
the exact model number. The tuner can't be relocated as the server is
controlling the frequency scan.

Obviously I didn't attach it to the FM coax input! I do have a small
amount of common sense.

The coax cable was already installed, I assume it's standard CT100
75Ohm.

the loop was just one of those cheap plastic things they bundle with
tuners.


somebody mentioned impedance matching, Thanks! I'm going to look into
this if I can't already find a ready made 50-75Ohm antenna.

somebody else mentioned overloading with an active antenna....this is
central London so there are all kinds of local AM stations....what kind
of damage can be done??

again thanks for your input, you have given me something to work with.





Without knowing what model you have, I looked at the AZAR 651 series.
http://www.cambridgeaudio.com/assets...-01English.pdf

All I see is 300 ohm connection for a loop AM antenna.
So, if you use an antenna on the roof, and 75 ohm coax coming down,
then a 75 to 300 ohm transformer into the receiver. I may even shorten
the leads on the 300 ohm side just to limit ingress.
Does the receiver make all the tones if you short the AM input with a
very short wire?
Mikek