Tuesday, 31 July 2018

HP ESP120 Power supply

I have 2 HP ESP120 Power supplys and one of them I use on my 2m amplifier in the upstairs schack.
This only because I do not have 3 phase outlet in that schack for a Delta SM70-45 power supply which I use for the 70cm EME amplifier.
Have made some study of how others are enabling the ESP120 and I am a bit pussled how they do.
The most used way seems to be published by N4GA where he advice to short out 3 pins without any desciption of their functionallity.
I read the only datasheet I could find on a similar power supply that looked like a drop in replacement for the HP supply.
This shows that when connecting these three pins together you short out Power good output, PSKILL and the present pins.

PWOK is the power good signal and is an TTL output pin indicating if everything is OK.
PSKILL is a emergency kill pin that switch the PS off if it looses connection to the 5V rtn.
Present pin is an indicator for the system to show that a PS is inserted in that slot.

Connecting these pins do not seems correct and I am actually surprised it works but it does.
In my mind I would connect the PSKILL to the 5V rtn constantly and switch the PSON to 5V rtn to enabel the PS output and I tested to do so and it worked perfectly.

The reason for all this was that I wanted to remotely control the PS from the amplifier and when connecting the Power on switch of the amplifier between the PSON to 5V rtn it works great.

I have occationally seen some noice from the PS on 2m. but I placed capacitors on the output connections to PS outer cover and also placed a copper braid screen around the two 10 mm Square cables to the amplifier and grounded that in the outer housing as well.
This seems to fix the worst noice but its important to ensure the cables are routed in a specific way to totally get rid of any noice.
This is most likely caused by the fact the 2m antenna is placed only 4 meters above the schack where the PS is located.

Got a half promise that a freind with an excavator will come this or next week to fill the whole for the concrete base and to dig down the anchor points for a 22m mast I have laying to use for tropo and a HF beam.

Friday, 27 July 2018

Slow progress

Have cut and trimmed all elements and drilled the booms and everything is prepared for mounting but the weather is just to hot at the moment.
The temperature is above 30 in the shade every day and outdoor work not possible at the moment.
Have done some other work like rebuilding the kitchen and spending time relaxing with the family.
Did some cleaning and maintenance of the machines in the workshop as well.
Bought 6mm dipole holder but have designed my own ones and will print a few to evaluate RF performance of the PLA material.

When drilling the booms I discovered that on 2 of the antennas the 2nd director was slightly shifted to one side so I need to go through all antennas to ensure they are assembled correctly.
Don't think it happend over time and It's a error from my side when assembing the antennas last year.

I also awaits the support wires I ordered earlier to try out how the support structure will end up like.
Assume it will be ok using one support wire going from the front of the boom to the back and have a turnbuckle in the back to allow adjusting tension.
The feedstructure will hopefully be enaugh support between the antennas in the back and if needed I will order some fiberglass support for the front but I want to assemble it all together first to evaluate.

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.