Tuesday, 9 January 2018

Preamp and relay failures.

The weather since last update has been either rain or cold so no further antenna work has been done.
Tried to work some after new year but the preamp blowing and relay blowing is a constant issue.
Exchanged the preamp as said in last post but blew it after some 10 CQ´s again and built a new relay box containing a Russian REW14 relay as main relay and a Siverslabs as RX isolation and termination relay but blew that setup too including the preamp after some 10 CQ´s or so.
Have not yet removed it form the mast as the temperature has been to low but will do so as soon as it rises again.
So I am not 100% sure the relay broke but the VSWR is like 7 and no preamp.

The REW14 relay should withstand the power without any problem at all and my first thought was that the amp is oscillating or something strange as it does happen in the middle of a TX sequence and not while switching.
Tobbe SM7EOI had an idea that maybe the power inside the PA is causing the switch that controls the RX/TX relay and preamp to switch on occasionally due to high RF levels while transmitting and this could for sure explain the preamp and relay failures.
The switch is a P channel FET switch that is located within the PA enclosure so I will try to design a circuit that triggers on the control signal and transmit to see what is happening.
Or I will design a new system for controlling and switching completely.

Another thing I discovered was that when I blew the last relay the PA indicated high VSWR but did not shut it off.
It still continued to TX and I had to stop with the JT software.
This should not happen but still it did so I need to check that in the PQL controller circuit.
Believe I have experienced something similar on the 2m PA as well so maybe there is something needed to be reworked.

Besides from that we have had our share of the flue and now the work has started again.
Will try to find an isolated 30-40mm bar or tube so I can mount the dual pol yagi on an az/el rotor before the next high declination time which is in 2 weeks so I can monitor the difference in signals from the moon with dual pol.
I think I have a boom to make a second of these antennas but don´t think I will find the time to make that.
Could be interesting to see but I have some other things to attend to first.

Have had a discussion with John ZS6JON and he is planning to build a similar setups both for himself and a Ham colleague.
As the weather is like it is here in the winter time, my plan is to do the conversion of all my 8 antennas with vertical parts when the weather gets warmer and when I have planned to also lower the mast and change to open wire feeds.
So most likely he will bet me and manage this before as his weather is more favorable at the moment.
Looking forward to his work and information and will support them as much as I can.

Saturday, 30 December 2017

25el Hor + 14el Vert GTV trial antenna

Now is the Christmas celebration done and I found some time to complete the trial antenna of a 25 el. horisontal GTV and a 14 el vertical antenna on the same boom.
Assembled the 25el first and put my adjustable dipole on it and as is it showed a good match as the last time the adjustable dipole was used was when tuning the 4 25 el yagis I built this summer.

Matching of 25 el H yagi

Assembled the 14 el vertical parts and measured the horizontal antenna again and it showed absolutely no difference at all.

Moved the adjustable dipole to the vertical antenna and the results was very close to the horizontal antenna without any tuning at all.

Matching of 14 el V yagi

Complete evaluation antenna

Manufactured dipoles for the two parts and measurements did not change anything at all so I am convinced they will work as expected.
Will try polarisation performance after the new year on tropo and over the moon to verify.
Will add a piece of coaxial cable with loss making up the difference in gain between the two parts before a relay and preamp to evaluate it easier.

Did work some of the moon the last few days and the propagation has been vary shifting.
From time to time very good signals and good own echoes and other times very poor.
To Asia the propagation has been very poor for my only horizontal antennas.
Worked Rob PD7RKZ that uses 8 times 11el GTV antennas and only 25W quite easilly which is for sure the lowest power station I ever worked and he worked smaller stations then me which is really amasing.
Tried to work Hartmut DG7YBN too but we hrd eachother at different times and never at the same time so no complete QSO yet.
Tried to work some tonight but it was raining some sticky frozen rain which caused some SWR and caused the preamp to break down so Went QRT.
Removed the preamp and the relay and the relay was OK but the preamp was confirmed broken.
Will exchange it tomorrow when the rain has stopped and in daylight.

Has not had the time to more in detail evaluate the SAV541+ preamp boards so I will continue with my YU1AW ATF ones for now.

Saturday, 23 December 2017

Merry christmas

Christmas time is here and it starts with a big storm.
Very high winds at the moment and we have had a power failure for an hour or so allready and it will build until midnight and them according to the prediction decline rapidly tomorrow morning.
Added some extra supprt to the antenna system to avoid it all to move to much in the wind and it seems to withstand the gusts quite well.

Will have few days off and will evaluate my future designchange by adding vertical antennas in front of the antenna supports.
Simulated and decided to us a 15 el based on Hartmut DG7YBN's 14 el GTV antenna.
Will also make the 2m setup and connect the transverter with the amplifier and the HF rig.
Like to make it work with both the tentec orion and any of the Anan SDR rigs.
Have a set of SM5BSZ WSE boxes for 2m that I will use for EME on 2m but that setup will have to wait as I have no antennas for 2m EME at the  moment.

But now will I spend the whole Christmas with the family and I wish you all a merry Christmas and a really happy new year.

Tuesday, 12 December 2017

Snow and ice.

Tried to work the V31eme dxpedition the past weekend but the polarization was not at all favorable.
Listen for approximately 9 hours and did not get one single decode.
At one point I saw a weak trace but it disappeared again.
Others reported the same and the ones that could work Uwe most of them had the possibility to RX vertically.
The polarization seem to be better when Uwe had the moon highest on the sky but that was some 1 hour after my moon set.
But that's life and a big congratulation to them who managed to work them.

The Gemenides MS shower is starting to get some good reflections and I worked UA3WM with huge reflections. One was 12.5 seconds and really strong.
Tried to work last night but had massive VSWR as the antenna was completely covered with snow and ice.
Lets hope it will melt away until tonight and tomorrow but I do not think so as the temperature will stay on or below zero for the whole time.

Got my PCB's for the preamp evaluation and just tested them quickly and got some results but had some problems with instability and the Nf was in the order of 0.6 so further work and tuning is needed.

Saturday, 2 December 2017

Good signals on the moon

Yesteray eavning the propagation was really good with very good reflections.
Noted my own echoes at -3.5 dB and HB9Q was constantly -1.

Worked 3 new stations and my first SSB QSO with Karl DF3RU who was 54 and solid copy all the time.
Did ocationally hear my own SSB echoes too.
Also worked OK2AQ who has a single yagi and 250W with good signals.

Today I have so far worked 3 new stations including BV3CE whom I tried to work yesterday without success.
Waiting for the V31 dxpedition that now stated will be QRV next weekend 8 - 10 December.

Have not got the PCB´s for the SAV541 preamp evaluation yet so no work there but the hardware clocks have arrived for the VK5DJ controller so that I will finalize this week.

Friday, 24 November 2017

Short update

Nothing exciting happens at the moment.
Working with preamp designs and is waiting for one batch of PCB's from the Chinese vendor but it will most likely take another week to arrive.
Tried to match the YU1AW design better but failed and is rethinking the design a bit.
Already working on a second design with two transistors in series to achieve more gain and to reduce the number of preamps to only one.
That is not completed yet and I wait until the first set of boards arrive so I can debug the first stage and optimize input circuit before ordering the second version.

Got the 4*40 displays I ordered for the VK5DJ controller and they worked very well but I missed the part in his design that he stopped including the SW clock module so I needed to order a HW clock module to finalize it and it has not arrived yet.

Besides from that I wait for the dec of the moon to increase and the V31 expedition to start.
Helping my sister renovating her new house as well so I am keeping myself occupied.

Saturday, 11 November 2017

Vertical polarisation

Tried to work the DX7EME expedition in the beginning of the week but did not receive anything at all. Not even the slightest trace of them.
They TX circular polarisation but later discovered an error on one dipole which led to some sort of linear pol and the few stations receiving them that could alter their polarisation saw that they where stronger on vert pol.
So how to add vertical polarisations on the setup I have.
Try to rotate the entire stack is not doable and to setup an entire new vertical seems to much work.
The two possible sollutions I see is to add an array of vertical antennas on the booms I have today but in front of the vertical antenna mounting tubes or go large dish.
I did some calculations and a YBN 14 element yagi would fit in the front part of the present antennas.
The stacking distance will be larger the optimum creating sideloobes stronger but in my mind the easiest solution to the problem.
Would not interfere with the horisontal array even when I change to open wire feed as the stacking cables would be coaxial for the vertical array and "hidden" on the mechanical structure of the antennas.
I have allready decided I will rework the setup next summer with lowering the mast and adding open wire feeds instead of the present coaxial and I will also remake the plate where the triangular horisontal boom is assembled on as it seems as the weakest part at high winds.
This will require the array to be taken apart anywhay so why not in the process drill for vertical element too.

I was intended to try to optimize the amplifier tuning but did not find the time to do it this week but hopefully will find the time next week.
Had a nice chat with Toshi, JE2UFF the other day on the HB9Q chat and found and started reading his blog and they are designing a kW amplifier that looks really interresting.

Have had a problem with the preamp not starting when switching to RX and investigated that and it turned out that the Relcom RX / TX relay up in the array was occationally not making proper contact.
So I removed it and pulled it apart to clean it but discovered that the TX part was quite severely burned and RX part oxidated.
Bought this relay and the other I burned completely just before the 1st part of ARRL contest in october used from a ham in Sweden and starting to suspect that they was more or less burned allready when I got them.
Have never exceeeded the max power rating and the have seen very moderate use here so most likely something has happned in their past life.
Cleaned it up and it works ok at the moment but need to change before it brakes completely.
Have some Russian REW-14 that will handle the power but then I need to add an isolating relay for the preamp as they have less isolation then the Relcom I use now.
Have a box of old Sievers Labs relays too which are similar as the Relcom and has some 80dB of isolation on 432 MHz that could be used but I have no information of power handling capbillity so It could be a gamble to try.