6m Trophy 15/16-June-2019

1906156m

This went better than last year with stronger Sporadic E openings. I managed 15 countries including Pantelleria which was a new one on 6m for me. This was my first contest with the 6m beam back up on the pole after re-roofing.

 

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26-May-2019 UK Microwave Group 3cm contest

There had been some rain about, so I was hoping for some decent conditions. I was disappointed. Unusually, GB3FNY was only 10dB above noise, so I suspected a receive problem. Neil G4DBN said he heard FNY well down too and reckoned it was microwave- absorbing rain/drizzle.

I gave a few points away to just five stations: Neil G4DBN, Denis G3UVR, David G4RQI, Nick G4KUX and G3ZME/P. The latter station was over to the SE from here, so difficult over the ridge & through the trees.

I heard no-one to the SE.

1905263c

18-May-2019 “2m May” contest

I entered this using the K3 driving an old Microwave Modules linear amp giving me about 20W to the 9el yagi. There seemed to be reasonable UK activity and I heard a few continentals. It was lovely to work Mark EI3KD again. He was strong on CW. I don’t seem to work may stations in Eire these days. Seven Scottish stations was a surprising haul. I did two 2 hour periods on the Saturday and the same again on the Sunday.

North-South seemed easier than East-West. I got 75 contacts in total. I can’t remember the last time I worked IO97 square. It is mostly sea! I failed to work JO02 and JO03. It was hard to hear anyone on the continent. In spite of this, my best DX was Helmut DL6YBF who was surprisingly strong in the conditions.

1905182m

Es’Hail-2 Dual Band feed with patch tuning screws

I’ve made an attempt at building a dual-band feed for a dish (instructions & examples on this link). I had some thin copper sheet available. I just hand cut the sheet with metal shears. I used my step drill bit to drill the holes in the centres of the plates. I pushed the cleaned base plate and patch onto the piece of 22mm copper pipe and added a bit of liquid flux at the joins & some solder. I fitted an SMA socket, held in place by brass screws, tapped into the base plate and sawn short so that the ends of the screws were flush. Then I baked the whole thing on an electric hot plate & dabbed in a bit more solder. I let it all cool down.

The first attempt resonated around 2475 MHz (with a second resonance about 50MHz up on that), so somewhat high.

In an attempt to bring the resonances down to the Es’Hail-2 uplink band, I laid a couple of little fragments of copper to a couple of corners on the patch. This seemed to work, judging from my VNA. I soldered them on with the aid of a blowtorch. This gave the patch antenna a proper “bodged” look, unlike the pretty pictures of professional-looking antennas I have seen. Of course, one fragment floated & moved slightly out of position and then refused to budge under the blowtorch, so the result was still a bit high in frequency. With a bit more blow-torching, I further added a bit of brass (from a connector block), to hold an adjustment screw.

 

The solder blob on the right edge of the patch in the left-hand picture is the feed point from the USB socket.

The upper resonance seemed about right, but the lower one was still a bit high at about 2405 MHz. Feeding the signal generator into the patch, I set up the SG-Labs yagi a short distance away as a receiver & fed this into the spectrum analyser. Rotating the patch showed that the difference between the maximum and the minimum signal was about 5dB. So the polarisation seemed to be somewhat elliptical.

With some more blow-torching I added a second screw block and adjustment screw. That gave me some adjustment of each resonance.

With screw-twiddling I found I could get a good return loss or good polarisation, but not both, so I opted for a compromise. The elliptical distortion came down to about 2dB; RL (return loss) about -15dB, or better, across the satellite bands. Gluing on the red lens from a Rocket LNB for 3cm improved the return loss a little further. I don’t know why!

Whether the patch’s polarisation is right-handed or left-handed, I have no idea. Today, Barry G8AGN helped me by trying it out on his 1.1m dish, feeding it from an SG-Labs transverter. We could see a carrier coming back on the Goonhilly SDR about 10dB over the noise. I hope that means the polarisation is the right way round.

Update 4-April-2019: here is the patch with both adjustment screws. I have also bent back the ground plane plate in order to fit it in a nice box I bought from Toolstation. The box has no metal parts & it passed the microwave oven test, so I am optimistic the box is transparent to microwaves. The patch looks even more bodged now, but this is hidden in the plastic box.

patch+2_screws+bent_edges

The lid clamps down nicely with integral plastic screws. I used a step drill bit to make the hole in the lid for the red lens and in the base for a tight fit for the copper pipe waveguide. I added an N-type socket with an SMA tail attached to the 13cm antenna.

patch_in_its_box_with_N-type_socket

I sawed off the horn from the Octagon LNB. This left a short stub of waveguide. I filed the diecast case of the LNB, so the stub stood as proud as possible. I cut a short ring of 22mm pipe to act as a spacer in the 22mm compression coupler. I found the coupler clamped on to the LNB’s waveguide OK.

Another, smaller, Toolstation box gave protection to the Octagon LNB.

As a result of the edge bends on the ground plane plate and encasing the patch antenna in a plastic box, the operating frequency has dropped. There is now a very good match (RL < -25dB) for the whole of the 13cm band, 2300 MHz to 2400 MHz, rising to -15dB at 2408 MHz. I have not yet re-checked polarisation. So maybe I could have skipped adding the the corner fragments and adjustment screws & just bent the ground plane edges and put it in the box?

I’ve put some bleed-holes in the boxes so that any condensation can escape. I shall apply some sealant in order to keep the rain out.

Es’Hale uplink experiments

I had recently taken down my 40 element Wimo yagi aerial, so I put this back up on the horizontal T on the dish pole, so that its elevation would tilt with the dish. I left it horizontally polarised & gave it an azimuth off-set with the intention of it paralleling the beam from the off-set dish; I just guessed this visually.

g3yjr_dish+13cm_yagi

I have added a sub-band switch to the SG-Labs transverter so that it imitates the jumper settings J1 and J2 from the four positions of the 2-pole switch. So now I can switch from 2,300 MHz to 2,320 MHz to 2,400 MHz (plus one other sub-band setting).

I’m guessing about 1W reaches the yagi.

This gave me a carrier 4-5dB over the transponder noise, so good enough for CW/morse code. Feeding into to 80cm off-set dish that I use for the downlink would be better, but I don’t have a way of doing this at the moment.

I tried re-aligning the yagi, but I did not see a significant difference, so perhaps my original visual guess was OK?

This morning I worked Severin DL9SW using morse code/CW. He was solid copy and a few dB over noise. This was my first ever satellite contact!

Update: I’m also experimenting with an Andrew linear amplifier. The SG-Labs transverter doesn’t like the match into this, but it is doing something as I get a lift of 10dB or so visible on the downlink. I’ve had a few contacts on SSB with this including Vera in Essen, who is the only woman I’ve heard on the satellite so far.

Es’Hail satellite downlink experiments

I have been experimenting with an Octagon LNB (Low Noise Block) which I’d obtained from the late John Roberts G8FDJ. Originally it had two outputs. John had modified this according to Bernie G4HJW’s guidance and had removed one output to allow room for an external reference oscillator input of 27 MHz. I used John’s TCXO (Temperature-Compensated Crystal OScillator) incorporating a 3MHz crystal and a 27 MHz harmonic filter. I hadn’t spotted the MIMIC buffer/booster amplifier.

I found a length of satellite coax with an F-connector on it & sealed this onto the LNB with self-amalgamating tape. I used a separate “Wi-fi” thin coax lead with SMA connectors and sealed this on the other LNB socket for the external reference input. I made a little clamp from some toilet seat bits and a bit of sailing rope and clamped the LNB close to the existing horn on the off-set dish arm. It is an 80cm diameter dish. I slanted the LNB, hoping to receive horizontal or vertical polarisation. I fed the satellite coax from John’s bias tee. The LNB output fed an RTL dongle (I’d given up with the FCD) and the data fed into GQRX running on Ubuntu Linux 18.04.

At first, I failed to get any sensible output from the LNB; I just got noise.  The LNB did not resolve anything; certainly not the GB3FNY beacon, which is very strong here. The LNB output noise lifted when I added the reference oscillator input via 40dB of attenuation. This seemed a lot of attenuation. The LNB didn’t seem to work on it’s internal crystal alone.

Barry G8AGN brought round a neat Arduino-controlled marker that he had made. I got no reading off this either. Barry did a neat job of replacing the LNB’s reference feed-in capacitor with a 1nF chip capacitor and did a general clean-up of the LNB’s board & case. We tried again. Still nothing from his marker. I took out 10dB of attenuation. A signal! It turned out that John had included a MIMIC in the reference oscillator box. Also the PLL seems quite fussy about the level of 27 MHz reference input.

Back in my lab/shack I sealed the die-cast case using outdoor Bostik sealant and put the LNB back on the dish arm. I tried 27 MHz from my signal generator. The LNB produced noise with above -40dBm input up the coax. With the reference input a bit stronger I finally found the Finningley beacon appearing about 60 kHz higher than where I was expecting it.

I adjusted GQRX to compensate for the dongle frequency error. The RTL dongle was remarkably stable. Overall the whole receiving assembly seemed as stable as my DB6NT-K3 receiver with GPSDO reference, so this looked very promising.

So I found raised noise from the LNB does not necessarily indicate PLL locking. I need a lock indicator! I settled on 26 dB attenuation in the 27MHz feed. (assuming 4dBm from the OXCO+MIMIC, this gives -22dBm into the coax feeding the LNB’s local oscillator).

Peaking the dish on GB3FNY, I found I needed to dip the dish about 5 deg. to for maximum LNB signal. Azimuth, (on my sloppy rotator) seemed about the same.

190215_3cm_horn+LNB

Saturday 16-Feb-2019 I aimed the dish at Az 154 deg., El 24 deg. Nothing. I took the power off the LNB and put it back on: signals! The PLL must have locked. Fortunately, there were signals on the narrow band; the band edge beacons were switched off.

I compared the Goonhilly SDR with my LNB/GQRX output:

190217_GQRX_v_Goonhill_SDR_comparison

The top window is GQRX with a waterfall falling down. The lower window is the Goonhilly WebSDR with a waterfall falling up. The left-most trace is the lower beacon. The right-most trace is the upper beacon.

Update: I had failed to get my FUNcube dongle working with GQRX, so I bought an R820T dongle from cosycave.co.uk priced £13. This stabalises after some minutes & the frequency accuracy is much better than the dongle I have been using. Barry G8AGN showed me how to drop out the coax socket that it comes with (using my hot-air gun) and I soldered in an SMA socket and it all worked fine. A couple of days later, its little blue LED stopped working, but I can live without the LED.

R820T_dongle