Oct 26, 2008

SteppIR @ PI4TUE - Part III

The final day of this project.
Me and my XYL went to her family
during the whole weekend, so again I was not able to join in. I had a great time in former Y22-country; enjoyed the superb hospitality, played with the kids of her sister etc.... Life is good, even without antennas.

Preparation for the last steps
More helpfull hands, safety tools, helmets, first-aid kit, everything to make this day a succes.
Again, you absolutely need perfect weather to work on a building roof at 220ft level. This turned out to be a beautifull day.

- Steef/PA0IB, Rens/PA3FGA, Aurelio/PC5A (wrapped in climbing gear)
- Assembling the prepared boom parts

- Tram trolley and protection against the existing guying wires by covering them with lengths of used plastic hoses.
- Steef/PA0IB assembling the control wires

- 6mtr add-on optional element
- Truss wire, not a luxury at such a height.

- 'Partly beam' just hoisted up in the air
- First-aid chick on standby
- Mind you; this is a small platform he is sitting on

- Lunchtime in the living room/kitchen/ contest sleeping room of the club station ESRAC at the 13th floor of the Technical University of Eindhoven
- L to R: Rens, Aurelio, Claudia, Steef

- adding elements
- "Look ma, no hands"

And then there's Murphy
OK, so what's different in the above second picture ?
The ground crew noticed a loose screw on the boom clamp of one of the reflector 'EHM' units. These had been loosened before to install the boom truss wire. Holy crap...!
So the whole ^%@## yagi had to be lowered again....
It is at this point that physical stress turned into overload as happened to Aurelio; suddenly his forearm muscles simply blocked and next his fingers were cramped-locked together. He got down and Rens took over.

- Switch of tower-operator
- Steef finalizing the control cable on the new Emotator FX1200 rotor

- On the left: HF-2V 40/80m vertical (not visual)
- SteppIR 3 el Yagi
- VHF antenna mast, including full size 40 and 80mtr dipoles
- Crossing the street-light; 160mtr sloper wire, barely visual

This final job lasted the whole day. Totally exhausted they left the premises at 18:00
During the week the antenna tested successfully ! This new antenna will certainly bring some new momentum in the coming contests.
In the meantime I have seen the antenna from ground level, it looks intimidating.

Again a job done very well guys !

Oct 5, 2008

SteppIR @ PI4TUE - Part II

Last weekend the 'next step'was taken in this project:

Remove the old antenna's from the mast on the roof
The picture below shows the roof of the building at the Technical University of Eindhoven. Not all antenna's belong to the contest station PI4TUE. There's plenty of antennas for FM repeater and packet and other digi-stuff as well.

Safety first ! Especially at a total height of more than 70mtrs above ground level (230ft). We have had to cancel several saturday options because of fierce weather (wind).
The top antenna is, sorry used to be a 5 element yagi for 50Mhz. The front boom part +director was already dissappeared; it simply must have snapped off at one point. The wind forces can be huge at this height.
The antenna below is a classic old Fritzel FB33 tribander + extra WARC dipole (12-17-30mtr).

This is Aurelio, PC5A, being happy as the weather is such nice for a change :)
Blueman +white helmet is Rens, PA3FGA.
The tribander came down easy, well too easily for one end-part of a director as it came lose and just dropped down. Nothing was hurt or damaged though. Upon close inspection several bad or loose mechanical/electrical joints were noticed. Now maybe this explaines the sometimes erratic SWR behavior we have experienced ?

See how the boom has bended over the years?

Time for a well deserved pause and some coffee.
The room is situated on the top floor and adjacent to the shack of PI4TUE. It has facilitations for making thee/coffee, has a fridge and besides the 'diner-table' lots of room to relax on one of the old couches.
From left to right: Aurelio, Claudia and Rens.
I'm pretty d*** sure the beer is a "leftover" from some other group !!

Next the Emotator rotor was removed. Its internal slip-coupling is totally worn out. A previous custom modification lasted for another year or so, and now it is in-operatable again. This one simply has served its time. Pity that the custom mounting plate for the mast was corroded and stuck. This will be a job for others now. So the new rotor will have to wait. Too bad, now the project is on halt again. Oh well, it will be quickly dark and cold soon after such a day of hard work.

This is how much space the new SteppIR will take up. The try-out of the assembly was done to prepare us for the future final installation. It is convenient working with these"pro's" who make optimal use of their time available at that day.
Why I am not in any picture?
I was doing shopping with my YL in Amsterdam.

Job well done, much appreciated guys :))

Upgrade vertical polarized yagi for FM repeater reception

Previously I have mentioned that I do like DX'ing on FM repeaters on 145MHz .
Not only both my transceivers have been specially upgraded for this (customized 455Khz filtering), but there is a dedicated vertical yagi antenna for this too. It is fixed at about QTF 160 in which I can constantly work PI3ZLB near the Belgium/German border on 145.725. During ducting propagation I can work, or at least hear other repeaters on that same frequency from Belgium, Germany and Luxembourg:

Repeater Near city Locator QTF QRB
PI3ZLB Geleen JO20WX 153 78km
ON0NR Namur JO20KJ 195 139km
LX0HI Bourscheid JN39AV 166 196km
DB0ZK Koblenz JO30SH 133 209km

The above vertical yagi antenna has been in use for more than 5 years now at different locations. It is a 4el '50 Ohm' direct feed version. The boom has been extended as the tower had a strong negative influence on the SWR. After the extension it worked much better.
Since I am planning an overhaul on my whole antenna system, this one needs some attention too. And while we're there, let's take it to the 'next level' right?

Old Flexa yagi's
At my old QTH I had a stack 2x 9el Flexa yagis's installed on my roof :

These were used for comparison to a single yagi having double boom length at the same height, mounted on a second mast. Total stacking gain was similar to the single long boom yagi, but the performance was slightly less. The wider horizontal angle(better for contesting though) showed more background noise.
My current location does not allow for a second tower/mast unfortunately :(
So both 9el Flexa yagi's have been lying around doing nothing ever since, actually rotting in the rain:

For those of you who wonder if these Flexa yagi's elements ( 2mm steel whip elements on extreme lightweight alumn) corrode on the element to boom contact, see below:

After 8 years of use this looks pretty corroded to me.

Rebuild to 5 el. FM vertical yagi
I decided to cannibalize one of them and rework it into a 5 element vertical yagi with offset mounting.
Time to do some serious cleaining & polishing :).
I just cut the boom and mounted the first 5 elements of this 9el design only. SWR measurements showed right what was expected.
Next, the boom required an extension for both the offset mounting bracket and the required extra distance from the tower.
I planned to insert a piece of the right alumn tube for the connection between the two boom pieces. The first few cm's go easy, but after that it's a tough job. The alumn insertion tube quickly grinds to a final stop. For durability I was planning to mount a parallel piece of boom anyhow, so after a sunday's afternoons job we get the following result:

Flexa yagi's have received a lot of critical remarks in the past about the (too) thin 2mm dia precious steel elements. I don't care about the 0.5dB discussions, all I see is its current merits:
  • Extreme light weight
  • Visual unobtrusive
  • Low wind load
  • Thick, high impedance dipole + balun
Can't wait to get this one it up in the air :)