The ANT751 and ANT751R are the same.
Read my post about the HBU11.
And the link for chimney antenna mounts.
Here are some places to buy antennas and etc. .
www.solidsignal.com
www.amazon.com
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Top Rail , fence pipe , is long , and works good to get antenna up high.
The Big box stores such as Home Depot and Lowes and etc. have Top Rail fence pipe.