How important is the placement of a high gain antenna for a USAT card reader?

[Apple Leisure]

I've had some trouble with the signal of this snack machine lately; the soda right next to it works fine.  So I bought a high gain antenna and mounted it outside and on top of the machine.  It's about half-way back, on the right side.  Last I left it it still wasn't receiving, I had given it about an hour.  Should I move the antenna, or is it likely something else?  It's a G8 or G9 reader I think, about 3 years old if that makes a difference.  Tech support was trying to help but scratching their head last time I was there.  Also, I bought two antennas and tried them both.

 

TIA

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[AZVendor]

That location is fine.  You just don't want to leave it inside the cabinet as that defeats the purpose of the high gain antenna.  It sounds like a bad card reader.

[Southeast Treats]

You didn't indicate what your signal strength reading was before and after, but in my experience the high gain antenna solves any signal problem that can be solved.  If it's still not working I would agree with AZ that the problem is elsewhere; you may need to change the telemeter...

[Corvus Corax]

Replace the Eport 5volt power supply. They become intermittent and shut down the display which powers the reader. 

[Snickers]

I have had some G9 telemeters fail here lately. Is there anything to do with them other than trash/recycle?