Xastir and local shape files

Derek, KV4SH and myself were discussing shape files and other things that are useful for mapping with Xastir, the Linux based APRS program. To increase the level of visibility you can download additional files from the USGS and the Census Department, but it is a bit of tricky process, so here are some tips.

When you click on the link, you will get the web interface to select the features you wish to use. For example Choose 2018, Roads, Choose “Virginia” under All Roads, Choose “Prince William” and the download points at tl_2018_51153.zip. For convenience I have downloaded a number of these files and put them on the PWCARES site, but the most current ones are always the best. See the Web Links at the bottom of this article.

In the zip files, the .shp files are useful for Xastir, so for example, if you unzip tl_2018_51153.zip you will see something like:

[kg4giy@Jura Downloads]$ cd tl_2018_51153_roads
[kg4giy@Jura tl_2018_51153_roads]$ ls -la
total 12440
drwx------@   9 kg4giy  staff      288 Jan 30  2019 .
drwx------+ 138 kg4giy  staff     4416 Aug  9 09:34 ..
-rwxrwxr-x@   1 kg4giy  staff        5 Sep  5  2018 tl_2018_51153_roads.cpg
-rwxrwxr-x@   1 kg4giy  staff  1933227 Sep  5  2018 tl_2018_51153_roads.dbf
-rwxrwxr-x@   1 kg4giy  staff      165 Sep  5  2018 tl_2018_51153_roads.prj
-rwxrwxr-x@   1 kg4giy  staff  4186140 Sep  5  2018 tl_2018_51153_roads.shp
-rwxrwx---@   1 kg4giy  staff    20411 Sep  5  2018 tl_2018_51153_roads.shp.ea.iso.xml
-rwxrwx---@   1 kg4giy  staff    92672 Sep  5  2018 tl_2018_51153_roads.shp.iso.xml
-rwxrwxr-x@   1 kg4giy  staff   119980 Sep  5  2018 tl_2018_51153_roads.shx

You will then need to move the .shp file to /usr/share/xastir/maps/ for Xastir to be able to find them. Specifically:

  • tl_2018_51153_roads.zip into /usr/share/xastir/maps/TIGER/2018/AllRoads/
  • tl_2018_51_cousub.zip into /usr/share/xastir/maps/TIGER/2018/CouSub/
  • tl_2018_51_prisecroads.zip into /usr/share/xastir/maps/TIGER/2018/PriSecRoads/

How to control display for zoom

In Map Chooser, select the parent directory, then click Properties

Hit the Select All button, then type (e.g.) 128 to the Max Zoom box, and click the button “Max Zoom->”. Now, the roads do not clutter when at 30k feet.

End Fed Wire Antennas

Over in the PWCARES Slack channel, Brian, WC4J and Dan, WA4GSD have been having a spirited discussion about end-fed half wave and other sorts of wire antennas.

It was suggested (hey, even I don’t need to be clubbed up side the head) that some of this discussion should be memorialized (since none of us have taken our ginkgo this morning) for future reference.

First up then, this handy dandy PDF of wire lengths.

Then there are a couple of YouTube videos:

And finally this little bit of information:

EFHW have better efficiency, lower SWR and is more forgiving on bands covered. EFLW tunes most bands but is 15% less efficient. You can look up more at this link on random wire.

Where might you use this? Why, in the field, like Brian did at National Night Out this week.