Monday, 25 September 2017

Finally up :)

Today I managed to lift up everything in the top of the mast.

It Went fairly smooth and I managed it allmost by my self.
The wife helped me controlling the winch the last part when everything was going over the edge at the top.
Was a bit tricky to fit the 4 u bolts as the tube was just a bit tight but it went ok after some fiddeling.
Will continue tomorrow with putting up the support wire for the cables and mount the elevation linear actuator.
The matching was a bit high in frequency and have no clue why as all individual antennas was tuned to resonance at approximately 432.200 MHz.
It will have no or very little effect of the performance as the matching on .200 is good enaugh but it's still irritating.

Sunday, 24 September 2017

Antennas tuned.

Finally a day without rain so I managed to get all antennas tuned and stacking cables mounted.
It took some time and some problems on the way.
One dipole feeding cable broke so I needed to make a new one.
The same with one of the stacking cables which showed some strange behavior.
When a 50 Ohms load in the end it measured 1.3 VSWR but all other cables was ok.
Did not investigate it in details I just made a new cable instead and everything was OK.
When all feeding cables and dividers was mounted the array shifted ballance slightly so its now somewhat back heavy so I need to add some weight to the front
Mounted the rotor and the azimut tube which was the heaviest task of the day.
It's a Stainless steel tube 60 mm outside diameter and 5 mm thick and 2.5 meters long and really heavy.
Should have mounted the rotor and tube before the mast was put up as it must have been much easier.
Lesson learned to the next time.
Will try to lift up everything this week and I will add pictures later as it got to dark before I was done.
The plan is to fasten the wire pulley at the top of the azimut tube and winch it up and place it some 10 cm above the top bearing. Will secure it along the way with a secondary wire if something brakes.

Saturday, 23 September 2017

Rain, rain and rain again

No the antennas are done with all support structures and everything is alligned and awaiting the dipoles and final tuning.
But its raining again :(
Last week we got 54 mm of rain and this week so far 23 and more or less rain everyday in the afternoon when I have time to do any outdoor work.

But some indoor work has been done with for example all stacking cables is done and within 3 degrees of phase difference for all 8 and the two 1/2" Cables differs 0.6 degrees.
The dipoles are finnished and awaiting the rain to stop and hopefully it will be a nice day tomorrow.
Starting to regret I made the mast the full 6 meter instead of 4 meter which is a more convinient height and is really enaugh for this antenna.
Let's see what happends in the future but I will not shorten it now, maybe next summer.

Sunday, 17 September 2017

Almost done

This past Saturday was almost rain free the whole day so I was able to finish all the support structures for the antenna and feeding.
Missed out on some screws and washers that I need to purchase this week.
Did the rework of the old dipoles and assembled the dipoles for the new antennas and they only need to be mounted on the antennas and tuned.
Everything takes so much more time then planned so at the moment I am a bit behind schedule because I wanted to have the antennas up to the Italian contest this weekend but its not.
This week I will first complete the assembly of the antennas and ensure no loose screws anywhere and lift it up a few meters to mount and tune the antennas.
I also need to make all feeding cables and mount the azimuth rotator and test before everything goes up.

Monday, 11 September 2017

8 antennas alligned

This afternoon I got the time to mount and roughly allign the remaining 2 antennas Before the rain started again.

Checked the material for the supports and will use 16mm round tubes in the front and 20mm Square in the back.
Found some angle pieces that will be used as mounting bracket for the supports.

The rain did not stop so I went inside and continued with the transverter instead.
Did a fix for the rx side tuning and the results is 1 dB NF and 26dB gain.

Configured the sequencer and TX scheme inside the transverter as well but I will use 24V at RX to the mastmounted relay and the preamp so I need to mount a 12 to 24V boost converter inside the transverter.
I switch the preamp and relay at the same time at RX so if anything fails the relay go into TX.
Did so in the past and never blown a preamp so I am confident it will work.

Sunday, 10 September 2017

Aligning antennas

Finally a day without rain pouring down the whole day so I started mounting and aligning the antennas today.
Finnished 6 of them and will continue tomorrow with placing the remaining 2 and adding support structures both front and back.
Maybe there is no need in the back but it will act as support for the feeding Cables too.

Discovered a few what I think is weak spots in the antenna mountings that I will correct this week too.
So hopefully I will be able to lift it higher this weekend and make the final tuning of all antennas before raising it all the way up.
Need to rework the feeding of the antenna built last year first as I did not have any stainless steel locking washers back then so they are slightly rusty which needs to be fixed.

70cm EME RX

Every sunday at 10 AM we are a group of Swedish VHF operators going on 80 for a small ring QSO and update ourself on different projects and discuss all sort of related issues.
This morning I discovered that the moon was on the way down so I started MAP65 and hooked up the 70cm antenna as I saw some activity on livecq.

The below screendump from Map 65 shows some good propagation.
Antenna used is a 19el DG7YBN without elevation, 12m RFC400 cable, preamp in shack  and a FCD+ receiver.

NC1I at -13 dB was suprising  and K5QE easily detected but do not know what rig he is using.

Friday, 8 September 2017

Power dividers.

My plan was to use 4 to 1 1/2 lambda power dividers that was 5 times 1/4 lambda on each side.
But for some reason this seems difficult.
Built my two dividers and they both behaves with less matching performance than on the 1/4 lambda resonance and 3 !/4 and even 7 1/4 lamba is good but not 5.
Measured other dividers of the same kind I built before and they more or less behaves in the same way.
So I decided to change to 3 1/4 lambda on each side instead and then it worked as expected.
Anyone seen this phenomena before?

Picture above shows measurements of the 3 1/4 lambda divider which is the same as a two meter divider.
The left resonance is for 432 MHz which here is the 2 nd resonance but the 144 MHz cant bee seen here as the mini VNA with extender cant work below 200 MHz.
So all is ok on 432 at the marker but look at the third resonace at approximately 700 MHz what a poor matching.
This is the 5 1/4 lambda frequency for that divider and close to 1GHz is the 7 1/4 lambda frequency which again is ok.
Its not a big concern but it will require some longer feedeing cables from the antennas to the divider but I am a bit puzzled and irritated about the thing.

Wednesday, 6 September 2017


Just a small update on the progress.

Last weekend was spent with my family and birthday celebrations so no work with this project at all.
The time schedule is somewhat delayed due to some problems on the way.
Finalized the rotor setup last week but had some problem with the HH-12 in the bottom of the Big RAK rotator.
Some friction caused a 0.2-0.5 degree hysteresis going from one direction to the other.
Seems difficult to sort out so I will have to live with it for now.
When going in one direction its rock solid and end up at the exact correct position all the times so the absolute encoding is correct it is just when alter direction the indication occasionally drags.
The problem was different depending on where in the turn the rotor was and I elaborated a lot with the coupling between the encoder and rotator.
The magnetic clutch is totally slip free and solid so no problem there but it seems difficult to make a coupling between the clutch and the HH-12 in a way where there is no friction or flex.

My version of the K3NG rotor controller.

Will elaborate with including PWM control of both rotators so I can use slow start and stop so the movement will not be so dramatic when tracking.

Got the transverter kit last week to and the customs did their job and an invoice was a part of the delivery.
Was quite simple to finalize but had some issue with the original oscillator but its on burn in now to see if that will affect the performance before I start to modify it.
I will use a separate reference locked oscillator anyway so its not a major issue but as it should work with the original one, I will make it operate as intended.
Measured Nf on the input chain and got approximately 1dB but that with the adjustable capacitors at their end positions.
Have not yet investigated if it was at min or max but will do so later in order to optimize it.
It will have little effect of the total system performance of the RX chain but if there is something that can be improved why not do it.

When assembling the 1.75m. vertical antenna bars for the antenna mounts on the 6m. horizontal boon I discovered that the boom was not fully in line resulting in the 4 vertical bars did not aligned.
It was twisted like a cork screw so I need to correct that this week.
The weather forecast for the week and weekend does not comply with outdoor work so I have to spend the time working indoors.
Fortunately I have a lot of space in the barn so I can work with up to 14 meters long mechanical structures inside if necessary.
Although the barn is large the roof is in sheet metal so no antenna tuning can be done there.