Wednesday, 11 July 2018

Antenna rebuild finally started.

Now I have started the antenna rebuild now and it is going fairly well.
Measured all antennas and they are similar to each other and the cables seems ok too but they have been drying in the massive drought we have at the moment.
Had 7mm rain for the last 2.5 month and all grass is burned and the leafs are falling from the trees.


After testing the antennas I made a bent dipole to check how it behaves.
Did not find any 6mm copper tubing but 4.6mm so I built one with that and it worked quite well.
Made a 1/2 lambda impedance transformer and a 1/2 lambda feeding cable and tuned it to 432 MHz.














With the dipole at the same position as the old one it needed som fine tuning of bending angle but the end results was very good and the same as the old.















Resonance is close to exacltly as simulated and matching is very good.

















Earlier I removed the 6m mast and lowered it so I can reach the feeding of the 25 element yagis standing on the ground .
Think its a good idea when elaborating how the feeding shall be.





















Needed to rebuild the base mounting too as it was not fully stable.

Will continue the next few days cutting and tuning the elements for the vertical yagis and drill the booms as well.
The garage has been locked due to a broken exhaust manifold on the Buick so I have not been able to drill any booms but that is sorted now thanks to my helpfull neighbor. 

Wednesday, 6 June 2018

Antennas down

Today was the Swedish national day and off work so I spent it lowering and removing all antennas.
Started in the morning and 2 hours later all antennas was removed and stored away.


Antennas lowered














All antennas removed














Measured the present stacking distance and it seems like its slightly to large as I suspected and according to the simulation of the antenas earlier.
My plan is to stack them using 283 Ohms open wire lines constructed of 6 or 8mm aluminium tubing.
Have looked at Nando I1NDP's antenna feeding and will I like the concept and I did some simulations of my 8 antennas.

Feed simulation















This feeding will give 100 Ohms impedance in the center Point of the 8 antennas but I will use a impedance transformation balun to correct for that and it is present in the simulation as the 70,5 Ohms transmission line.
Simulation results are very good with good bandwidth.

Simulation result including 100 to 50 Ohms transformer













The transformer will be built using a 40mm square tubing with 2 mm wall thickness and a 12mm round tube inside and this will get very close to the needed 70,5 Ohms.

Balun simulation














Will start with cutting of the antenna element and drilling of the booms next week and change the stacking distance to fit the new dimension.
Will also measure all cables that was used as a few of them seems to had moisture inside the connectors and measure all antennas prior to the drilling to check the performance after the winter.


Thursday, 31 May 2018

Rainmaker evaluation.

Finally I got the opportunity to test the rainmaker antenna performance.
Last Sunday I was QRV during the ARI contest and listen a lot to evaluate the performance.
Started by measuring Sun and ground noice and it all corresponds well to the VK3UM calculations.
The 25 el has close to 2 dB more sun noice and the ground noice is very similar so the antennas are working as expected when evaluating noice.
Listen a lot on Bernd DL7APV as he was for a long time the only station Calling CQ.
The 8 stack RX at -1 to -2 dB consistent when using WSJT-X 1.8 and the single 25 el H pol he was -8 and the 14 el V pol was at -6 dB which is really good for a single antenna of that size.
Look below on the RX screen dump.
Worked a few stations with the 8 antennas and all europeans reported close to only Vert pol signals received which corresponds well to the signal I received my self.








These tests together with the short test I did before and the test John, ZS6JON did earlier convince me that the concept seems to work as expected and I will start to rebuild the 8 antennas I have.
Will remove the antennas soon and start drilling the booms and cutting all elements and prepare for the open wire feed for the 25 element antennas and I might also need do some adjustments of the stacking distances to fit the correct length of feed wires.

Will try to make some more updates from now on but up until now there has been no radio activity at all.


Tuesday, 10 April 2018

Spring is here.

Finally all snow is gone.
So now I will start the evaluation of the dual pol "rainmaker" again.
Will also perform some sun noice measurements on the present system as reference when I make the rebuild to open wire feed.
The Italab amp build progress is slow at the moment and non ham related work is needed att his time.
Need to prepare the summer car and also spend some time in the forest cutting down trees before the sap goes up too much.

Did not work the CR2 dxpedition.
Heard them fairly good and regulary but pol was not playing along so they never heard me.
Lets hope the Z66EME dxpedition will be easier to work.
Besides that I have not worked so much lately.
The activity is mostly at max dec and when any dxpedition is qrv.

Will try to update more regulary in the future but nothing has happen lately so no point in posting nothing.
Got a PCB for the ON4BCB DIY version of the OE5JFL controller from Ronny SM7FWZ and is sourcing Component to complete the build.
Use at the moment VK5DJ controller and its working well but want PWM for the motors and it is an option in the VK controller but it seems easier with the OE5 one with direct support for a H-bridge.
Furthermore it also have built in position data for more noice and quite sources.

Saturday, 24 March 2018

Spring is comming.

Finally we got some warmer weather and the snow is melting quite fast but still we have some 20 cm in the garden.
Have only made some work on the Italab amp but not so much actually.
Have spent a lot of time bead blasting the rims for the Buick and will powder coat them and mount new tires as well and will also do some work on the engine later.
I also need to start cutting down trees to use as firewood for the next winter and that is somewhat time consuming.

The only activity lately was the TD9CHR dxpedition who I worked and now awaits the CR2EME dxpedition which is about to start today or tomorrow.

Will continue with the amp and I am right now cad a PCB for the arduino nano with all external circuits to fit within a screened casing including decoupling caps and series inductors on all input and output connectors.
Will hopefully mill the board next week so I can test the controll circuits and see if it behaves as I want.

Sunday, 25 February 2018

Wintertime

We have now entered a real wintertime here.
Temperature is at highest -5 during the daytime and down to -10 during nighttime and more or less powder snow falling everyday.
In total we have more then 40cm of snow and even driving the snowmobile is difficult in some places.
Closer to the coast line they have had really much snow during the past few days and below is a picture when I went to work Monday morning.
Did meet one car and it was OK as long as you did not stop and just kept moving all the time but the guy I met did stop so he got stuck.
Road to work Monday morning. 













So all antenna work are closed down and last week I was hit by the annual flu so just some minor work has been done but nothing related to the EME station.
The antenna has at the moment not so much snow on it and matching is good and the snow falling now when its cold is very light and will blow away.
Looking forward to the Guatemala dxpedition next weekend and I exchanged the preamp last week as it was not the best and some of the lost RX performance is restored.

Was active during friday and saturday eavning but activity was not that high.
Dubus contest was running and a lot of CW activity and I hrd a lot but I am not really used to the RX of the Anan radio in CW.
Feels like I have difficulties adjusting for a good AGC behavior together with bandwith for weak CW RX so I need to use it more to find my settings.

The heat sink I have planned to use for the Italab 70cm amp is huge and I need to cut it in half.
I got two of them with the plan of use parallell FET amps for both HF and 2m.
Will cut it this week and build a casing for the whole amp.

Sunday, 4 February 2018

Snow Again.

Need to rename my dual pol test antenna to the snowmaker instead of rainmaker.
From Friday afternoon to Saturday eavning we got more then 30 cm of really sticky snow.
All antennas are cowered and even the 80m dipole was more or less laying on the gound as the end spring was pulled to maximum length du to the wieght of all snow stuck to the antenna element.
So no antenna test this weekend and it will be cold the remaining of the week so the snow will stay on so John, the WW will be in use the whole week.

Will keep myself occupied with indoor work for some time now but have plenty of unfinnished projects to start up again and I also have a Italab KW pallet on 70 cm I bought a few month ago that also needs to be put together.
Will use the PQL controller as base and also PQL low-pass filer and directional coupler but everything controlled by a ON7EQ controller and display unit.