Nov 11, 2009

Upgrade current VHF station

Planned changes

There's a few reasons why I'm planning some upgrades on my current VHF station. First there's the annual wear and tear; the 17el 6.67m 144MHz Tonna yagi has a bended boom, due to a storm last spring. The coax is some 5 years old and has a few connectors too many along the path. I want to raise that antenna to the max level officially allowed, which will involve another 1mtr above street level. There's an older 4el vertical yagi for long distance 145 FM repeaters for which I have a replacement 5 el version ready. The 70cm vertical omni and yagi combo is still awaiting going into service. And them some more minor things.
Then there's plenty of equipment in the shack which needs to be sorted out, optimised for performance and operation.

Check current beacons
Just for fun let's check two popular beacons.
Now this surely is very subjective since there are so many criteria involved which change from day to day. The weather today is cold, cloudy and moist. The FM repeater at 100km distance is a few dB down and shows some more noise on its signal than what is normal.
Waiting for the right up-swing in the very slow fading (several minutes to be exactly) I copy:

DB0FAI (A1A) on 144.490 from JN58IC
This German beacon uses a 16 el yagi mounted to a cows barn and puts out 100W pointed into my direction. Distance is 545km.
You can find more info on

The displayed frequency shows the 28MHz IF ouput of the transverter plus its LO offset.
The beacon is at times pretty loud; some 34dB above the average noise level.

HB9HB (F1A) on 144.448 from JN37QF
This Swiss beacon puts out 10W into a 2el yagi also into my direction. Distance is 507km.
The location is on a mountain at 1395m ASL.
Details can be found at:
The F1A transmission effectively shows 2 signals after detection in CW mode with a 1 KHz difference. The signal on 448 sounds inverted, the one on 449 is normal. This makes finding HB9HB, which is always very weak at my place, both challenging and a good performance test for the receiving equipment.

Used equipment:

- Bended 17 el Tonna Yagi @ 12m ASL
- 25m Ecoflex 15 + 9m Ecoflex 10 coaxial cables
- Elecraft XV144 transverter (28Mhz output)
- home made 3dB splitter
- Modified Elecraft K2, optimised for 28Mhz
- Perseus SDR receiver

I'm using both the Perseus SDR as well as the Elecraft K2 for listening. The Perseus offers valuable virtual data, the K2 is the slightly better receiver. The 3dB splitter has no negative effect as there is plenty of signal from the transverter output.

Nov 1, 2009

The MPV project II

The MPV rises to 16mtrs !

I have found a top section of an old 12m spiderpole. This came from a damaged Heavy Duty version and has served as an 160m vertical during a HB0 dx-pedition. However, despite wall thickness up to 2mm it didn't last long in high winds.

The 12m fibreglass pole can be spotted on top of a 20m alum mast which serves domestic logistics.

I allocated the top sections in the back of my shed and found them in good shape. A total length of 6.40m is available and it fits tight on the top section (22mm dia/2.5mm wall) of the earlier installed 10m DJ6NI mast. For the experiment I added a couple of hundred windings using 0.85mm lacquered copper clad steel wire from

Nice job done, but a quick check with my antenna analyser using some ground radials and a 3m ground rod, shows resonance at 1570KHz. And I haven't even hoisted up the bottom 10m sections. A few too many windings I say!
With the 40cm overlap and true snug fit the Most Pitiful Vertical is now at 16m.

I run upstairs in order to make a nice 'total view picture' from the 1st floor.
Looking outside I quickly recognize the downside of this kind of structures; wind.
Even the slightest afternoon breeze bends it like this:

Another guying point at the 10m point, just below the black top section, is not feasible. My guying locations are way too close and there's no room for attachment points farther away. Let alone the risk of tangled up guying wire during the daily job of sliding the whole structure in and out. BUMMER.

OK, where are we now?
  • This current 16m version is not an option.
  • Guess that a max of 12m vertical is possible, provided I use a thin wall fishing pole and no extra windings on the top section to minimize the load.
  • Explore option of a T-version, where the top-hat functions as guying. Max 12-14m height?
  • Better install an electrical 30m Bigh Bertha, which needs no guying and is 3m high (and the same amount buried in the ground with several tons of concrete, right?).
What went well?
  • Back yard has been cleaned up
  • Found that chicken mesh-wire functioning as ground screen is a realistic option

Only few weeks till CQ-WW CW