In this example we'll use the main Knoxville, TN Post Office as our center point. Our post office is located at:
1237 E Weisgarber Rd, Knoxville TN
So, go to http://geocoder.us and type in the address you want to be the center point (typically your home address).
The format you will use in TweetDeck is
Distance can be expressed in Miles (mi) or Kilometers (km)
Now in TweetDeck, add a new search column and use the examples below:
To find all Tweets with a 5 Mile Radius:
To find all Tweets in a 10 Mile radius that contain the word "fun":
You could also do similar searches from the Twitter.com search website http://search.twitter.com.
There you can define searches that contains a "Place" such as Knoxville, Atlanta, Boston, etc. You can also use a Zip Code.
Find all Tweets within 5 Miles of the 37909 zip code:
In Twitter's search box you enter: near:37909 within:5mi
Find all tweets within 15 Miles of Knoxville that contain the words "Krispy Kreme":
In Twitter's general search you enter: "Krispy Kreme" near:Knoxville within:15mi