Friday, March 22, 2019

Low Band DX - 2 - Vertical to Inverted L

Last weekend I decided to upgrade the vertical to an inverted L, specifically a 1/4 wave on 80m.

Measuring the 43 ft vertical purchased from ZeroFive, it has 14 x 32" sections and the base section is 36" for a total of 484" or 40.3 ft - where is the other 3 feet? No idea! Running some rough calculations I added a 22 ft horizontal wire to the top, and after a fight with the maple tree snagging the wire a few times I got it up.

I was a little surprised at the changes, SWR:
  • 80m, 3.5 MHz is near 1:1 and rises towards the top end of the band.
  • 60m, SWR high, remote ATU fails to find a match.
  • 40m through 10m SWR high, remote ATU matches it in no problem.
Since I have no real idea as to what load the antenna is presenting to the ATU, its hard to know much more, to solve that I have a RigExpert AA-55 antenna analyzer ordered.

With that, I decided to bang my head on antenna modeling to help get a better understanding on what to expect from this inverted L I have created. Being brand new to modeling software, I found 4NEC2 "too hard". I took at a look at MMANA-GAL, which includes an inverted L file. After a quick edit of the geometry to match what I have, the results were interesting. Granted I might have missed an important detail with this, it could easily be totally wrong.

Starting with 80m and working our way up, blue is horizontal, red is vertical polarization:

80m, what I expected, the small horizontal component is from the horizontal wire at the top. An anecdotal observation is the small horizontal component has made receiving local signals via NVIS stronger.

40m, calculating the length on 40 turns out to be a 3/8 wave, so that works.

For reference, here is the contents of the MMANA-GAL file:

Inverted L: v40 ft + h22 ft
0.0, 0.0, 0.0, 0.0, 0.0, 12.28, 0.015, -1
0.0, 0.0, 12.28, 6.7, 0.0, 12.28, 0.001, -1
1, 0
w1b, 0.0, 1.0
2, 0
w1b, 0, 0.0, 400.0, 0.0
w1b, 1, 10.0, 0.0
400, 40, 2.0, 2
2, 0.0, 4, 50.0, 120, 60, 0.0
Feeding direct coax 50 Ohm.
Bandwidth (SWR<2) 210 kHz.
Load 2 ia a ground loss.

Tuesday, March 19, 2019

WSPR - 40m, 1 Watt, 16441 km

Distance wise, this is the 2nd best spot I've reported yet at 16441 km / 10216 mi, from ZS1LCD in Cape Town South Africa who was running 1 watt on 40m [7MHz]. ZS1OA remains king at 16511 km / 10259 mi on 30m [10MHz], and ZS3D is a regular in 3rd place at 16233 km / 10087 mi on 40m.

After running WSPR for about three months, I took a break from it about a week ago having built up a good feel for what I can expect with the current antenna configuration. Last night I had it running again after adding a 20 ft horizontal wire to the top of the 43 ft vertical turning it into a 1/4 wave inverted L on 80m.

With the exception of 60m, Remote ATU has no problem finding 1:1 match 80 thru 10m, 40m was the surprise since the antenna is close to a 1/2 wave. Hard to know with out an antenna analyzer to see what is really going on. I'll soon have a better idea, ordered a RigExpert AA-55 analyzer, and another 40 x 32 ft radials for the vertical / inverted L to bring the total to 60.

Monday, March 18, 2019

Extra Class

This past Saturday I made the trip to Renton where the Mike and Key club run VE testing sessions.

It took about 4 months of study and the practice exams on QRZ to reach an average score of 80%. To pass you need a score of 74%, out of 50 questions you can get 13 wrong.

The good news is I passed!

I think the incentive based system here is a good way to manage access to HF bands, in addition to creating an incentive to further your skill and knowledge, regardless of how "irrelevant" some think the subject matter and questions are.