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How Do I Measure Distance For DX Reception Purposes?

M

Matt Cvetic

Hi, everybody!

I've been lurking around here for some time, now, and finally decided to register so I could ask a few questions and chime in on things once in a while.

I have a DXing question I thought you guys could answer for me.

Here it is: When I am trying to calculate from how great a distance I've received a particular station, do I base it on how far it is from where I'm at to the station "as the crow flies", or do I use how far away I am in terms of "land distance"?

This afternoon, for instance, I was checking to see what I could catch on 550 AM.
At first, I picked up a very weak signal from WDUN in Gainesville, GA.
That's only about 183 miles from me "as the crow flies", but approximately 210 miles away "by land transport". (I live in East Tennessee, about 45 miles or so from the Tri-Cities. I was using my trusty Sangean PR-D5, by the way).

In any event, I've caught WDUN a few times before and was not particularly excited by that. It suddenly got much more interesting, however!
Just 3 or 4 minutes later, I began getting a relatively good signal from WGR-Buffalo, NY! (Even "as the crow flies", that's a good 511 miles away, and almost 650 miles distant "over land").
That's the first time I've gotten WGR during daylight hours and I was very excited about that catch!

A good 7 or 8 minutes later, it faded out and I was able to hear a weak signal from WKRC in Cincinnati for a brief time (yeah...I wonder if those call letters being SO CLOSE to WKRP is just a 'coincidence', too!).
It's a 5,000 watt station and I don't recall ever having gotten it before, either.
From less than 300 miles away, though, I didn't consider that nearly as great a 'feat' as picking up WGR!

In any event....how do I measure my DXing distance?
As "the crow flies"? By "land distance"? Or, do you split the two?
Do AM signals usually travel "as the crow flies" or follow the "lay of the land" or does it depend on the antenna array and so on?

Thanks so much for your help!
I really enjoy these forums A LOT!
 
Radio - with some really weird exceptions - EME on amateur radio comes to mind - is always 'as the crow flies'. Shortest straight line distance. But it is via the 'great circle' route. Meaning you can't necessarily just lay a ruler on a map for long distances. There are computer programs for computing the distance but I don't have the name of one off the top of my head.
 
Matt Cvetic said:
Hi, everybody!

I've been lurking around here for some time, now, and finally decided to register so I could ask a few questions and chime in on things once in a while.

I have a DXing question I thought you guys could answer for me.

Here it is: When I am trying to calculate from how great a distance I've received a particular station, do I base it on how far it is from where I'm at to the station "as the crow flies", or do I use how far away I am in terms of "land distance"?

This afternoon, for instance, I was checking to see what I could catch on 550 AM.
At first, I picked up a very weak signal from WDUN in Gainesville, GA.
That's only about 183 miles from me "as the crow flies", but approximately 210 miles away "by land transport". (I live in East Tennessee, about 45 miles or so from the Tri-Cities. I was using my trusty Sangean PR-D5, by the way).

In any event, I've caught WDUN a few times before and was not particularly excited by that. It suddenly got much more interesting, however!
Just 3 or 4 minutes later, I began getting a relatively good signal from WGR-Buffalo, NY! (Even "as the crow flies", that's a good 511 miles away, and almost 650 miles distant "over land").
Click to expand...
For shorter distances (200 miles or less); you can put in zip code (or GPS coordinates) at the www.radio-locator web site to get the distances for AM, FM or both; of course, using your zip code the distance (as the crow flies) could be off by 3 or 4 miles, but it will be a close approximation.

For example from Johnson City, TN it shows the WDUN 550 antenna to be 159.6 miles away.

http://radio-locator.com/cgi-bin/lo...&format=&dx=3&radius=250&freq=&sort=freq&sid=

The Sangean PR-D5 is an outstanding radio. (I think GarFla was telling everyone about what a great radio it is.........so I want to Thank GarFla for suggesting it), between that and a Grundig Satellite 750 I have awesome dx opportunities.

drt,
st. petersburg,fl
 
The Sangean PR-D5 is an outstanding radio. (I think GarFla was telling everyone about what a great radio it is.........so I want to Thank GarFla for suggesting it), between that and a Grundig Satellite 750 I have awesome dx opportunities.
Click to expand...

Been thinking about getting the '750' sometime reasonably soon (later this year, anyway).
It's been around a while, though, hasn't it?
Anybody know if a replacement and 'upgrade' for it will be coming anytime soon?
 
Google Earth has a line measure feature built in, and on regular Google Maps, if you click on the "Maps Labs" link at the lower left-hand corner of the page, one of the features you can enable is a distance measurement tool, saving you a trip to a separate website. It has all sorts of options for units, like cubits, light-years, and smoots. Using Google Earth is helpful because if you download this handy filter from FCCInfo (http://fccinfo.com/fccinfo_google_earth.php) you can easily locate exactly where a station's transmitter is and measure from there to wherever you're listening from.
 
You should measure it from your antenna to the transmitter site. If the distance is large enough it's a good estimate to measure from your town to the city of license. Do not measure based on driving distance because radio waves don't take the highway.
 
This may have been mentioned elsewhere, but Google Maps now has a beta version of a distance measurement tool.

In the directions pane on the left of the map, click Map Labs just above the Google Maps copyright info, and a window will pop up. Click "enable" Map Measurement Tool, and then click "Save Changes" in the bottom left corner.

The tool (small yardstick icon) will show just below the mile/kilometer bar on bottom left of map.

Works great.
 
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