antenna mystery

[IQ_imbalance]

Scratching my head over this. I have two antennas....a discone and a 800-900 MHz Yagi. Here's what they look like at the radio end of the feedline....

(discone on left, yagi on right)

The mystery is that i'm trying to monitor a 850Mhz system, so you'd think the yagi would be much better. Problem is the SDS200 is deaf to that system using the Yagi, but works OK with the discone!



(again, discone on left, yagi on right)

Can anyone tell me what the heck is going on???

 

[tvengr]

It appears you are getting more signal on the discone. I would suspect a problem with your yagi.

 

[ind224]

Is the yagi on a rotor or can you turn it? Can you confirm being able to null another system? Is it vertically oriented? I'm seeing 868.00 on the screen is that a control channel? Same coax and antenna height?

 

[IQ_imbalance]

i'm going to start checking the coax starting at the antennas. That might be the quickest way to figure out if it's an antenna or a coax problem.

 

[IQ_imbalance]

OK, the truth has been revealed. Don't ask me why, but the coax itself was showing that resonance at ~850 MHz; it was severed and the yagi wasn't even in the circuit! Sheesh. Lesson learned.