In these last days I focused my free time to meteors radar by French GRAVES VHF Radar transmitter. The new page is here: Meteors Radar.
On this page you can find a 3 minutes auto-refresh picture almost real time. Just under a statistics image of received meteors signals.
At the moment the system is composed by a desktop PC with a simple RTL-USB SDR receiver and a LPDA V-UHF antenna.
I hope to better optimize the quality of my receptions to get best reports.
What the page shows?
I must for first thanks mister Simon Dawes that shared the original Conditional Action for SpectrumLab that I modified for my purposes.
At the top of the page we can see the 3 minutes real time grabber image. The center of the image is at about 143.050 MHz: the GRAVES transmitter frequency.
For any positive sample you can read some data just after the meteor echoes:
Date&Time, Signal strength, Noise, Frequency, Time Length, S/N ratio.
Just under there is an image of RMOB Lab (Radio Meteor Observatory’s On Line) where my system sends data for colorgramme compilation.
At the bottom a 6 hours plot shows a pair of parameters analized in the time domain: the Signal Strength of the echoes and the Time Length of the same echoes. It’s so possible to see at a glance not only the quantity of events but also the strength of them.
Strength is in dB (absolute and not relative to noise floor), Time is a number derived from Conditional Action cycles, so 25 is about 6 seconds. Only longer events than 6 seconds are saved into the images gallery.
Just now my U3S transmitter is blocked in TX condition as is possible to see in the next picture:
The continuous line over 475.740 is my signal more than one hour long. The problem is that it was an unmanned operation and I’m not at home now. Strange is that the U3S doesn’t seems to have a whatchdog for a hard reset of the system in these cases.
It’s probably caused by high antenna SWR because of windy night.
In the next days I will build a web remote control at least to remote reset the TX and eventually turn off the amplifier.
As Rick IW4DXW said to me: “A good test for your amplifier, HI”
Here follows a PDF doc where is possible to see all my unique stations transmission report on WSPR MF band, they are in descending order of distance. I still didn’t compiled a ranking by country but it’s easy to see how many DL and G are in the log.
Senza nome 1
Finally my signal came out from continental Europe reaching Iceland.
44 stations copied my signal and 3 times TF3HZ received my weak signal:
| 2016-09-19 22:16
| 2016-09-19 22:08
| 2016-09-19 22:00
The distance of 3355 Km is a new record for my 100W transmitter and the “clotheshorse” antenna in MF. For sure conditions were very good and no strong thunderstorms over the Europe last nigth as two nights before.
This good outcome is probably due to antenna improvement, last year was very difficul for me to reach England and impossible be heard from Norway, now it seems to be a daily practice.
Last night was my second “serious” TX test on 136 kHz, transmitted Opera32 mode after an upgrade to the matcher.
To tune the antenna on 136 kHz I’ve build a couple of inductors over two hand cleaner soap bins. The first one was wound with enameled copper wire of about 1 mm diameter, the second with PVC copper wire of 1.5 mm diameter.
The first has an inductance of 2.2 mH while the second is around 400 uH.
Inserting one bin into the other I’ve reached the needed inductance to work with my antenna on 2200 meters.
Moving up and down the two bins I’ve reached a coarse value just to use my variometer for tuning. The maximum value that I can reach is about 4 mH.
In the next photo the final layout of entire matching system for 630 and 136 kHz.
From left: remote controlled variometer (for fine tuning), matcher, 136 kHz tunable coil. The next step will be to remote switch the two bands from my radio room.
Due the lack of public MF grabbers on the net, last night I’ve tried to receive my signal in qrss10 with remote WebSDR system. I alternated the two transmission mode so to have an idea about where my signals were received.
With great surprise receiving myself on Twente WebSDR my signal was audible and even a bit stronger than IQ2MI signal (used always to compare mine). The audio record follows:
My signal is on higher frequency because WebSDR software uses reverse CW.
For the expected solar storm of last 3rd August, I’ve planned a continuous 72 hours transmission of my MF station as QRSS10 beacon since 1st of August afternoon.
I’ve monitored my signal on the MF grabber of Stefan DL7FC, comparing it with IQ2MI signal, downloading for the 72 hours a picture any 10 minutes.
Nothing strange appeared over the pictures, signal was about the same for all days like before.
Only to note that IQ2MI signal appear over the grabbers at about 1800 UTC (sun set at my QTH) while mine about 40 minutes later. The same in the morning, my signal disappear 40 minutes before IQ2MI signal.
Here another picture with IK1HGI signal, too:
Even though I’m 500 Km farther from Stefan my signal seems quite solid.
This is my umpteenth upgrade to the TX antenna to try to get better general performance and get the possibility to work on 136 kHz without tons of electrical wires outside the terrace.
The new layout is drawn in the next basic picture:
I’ve passed from 4 top wire and a single vertical tube to 6 wires as in the picture. The hat is always 13 meters long (I don’t want to go over the neighbour roof) but now also six wires come down to about 10 meters to the variometer.
The capacitance was raised from 235 pF to 310, not bad. The only doubt is about the vertical side that is not exactly vertical and it shows an angle of about 75/80° to the ground.
The telescopic pole by now is not more a radiating part of the antenna, this simplified my life because I don’t need to insulate the base of the pole for high voltages.
This is the usual photo of the whole antenna with an Unidentified Flying Object up on the left:
Now the target is to tune the antenna for the 136 kHz that should it be possible with a 4.4 mH coil.
Since my antenna was born as monoband for 630 meters, until today I’ve used an autotransformer built around the variometer.
In these days I’ve tried to tune the antenna on 136 kHz, beginning to put some mH over mH to reach my goal. Arrived to 136 kHz I’ve sadly found that the autotrafo was inadequate to reach the correct impedance. So I tought to build a toroid coupler as seen on the web. A short look inside my “oblivion boxes” just to find a big blue toroid, this is a N30 material, usually used for interferences from several-KW triphase motor inverters.
It has a quite hi initial permeability and the work frequency is exactly for our game, from 10 Khz to about 400 Khz. Somebody could turn up one’s nose but since turns on toroid are only ten or so and mine is not a KW station I’ve decided to try to build my new matching unit.
For first I’ve winded 10 turns for primary and then 14 for secondary, here is what I’ve gotten:
I’ve soldered 10 wires for as many as different impedence taps and painted the welds with insulating paint.
The next step was to put the “spider” inside a box to be protected from rain and dust (and cats…).
The matching unit under the front cover
Every screw is provided of an OR rubber.The wingnut give me the possibility to fast retune the antenna The first test on 136 kHz was an immediate success, SWR was 1.14 at first “wingnut touch”! The same coming back to 474! WOW!
It was time to give POWER!!
Just started the trasmission on 136 I’ve seen power going down “rhythmically”: there was something was arching! Testing on 630 the music was about the same. A brief look on my external ammeter was clarifier. My old autotrasformer was not insulated from coaxial cable, common mode current probably was running over the braid. This new solution now shows me a 3 times bigger current on ammeter. The voltage is of course also higher and the antenna wall insulators cannot resist to this new hi voltage.
So at the moment antenna is perfectly tuned but I can use only about few Watts.
Next step is to increase the insulation to use more than few Watts.
Stay toroidal tuned!