28-December-2020 SHF UKAC

This was my first UKAC this year. The Microwave Modules 70cm transverter wasn’t working on PTT for some reason and was defaulting to RF Sense, so I struggled a bit on 13cm. It is nice to have 13cm going again. I need to improve the Noise Factor of the pre-amp in the box on the pole, but that will have to wait until the weather calms down.

It was all pretty local stuff on 13cm:

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It was even more local on 3cm:

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26-Nov-2019 SHF UKAC using 13cm and 3cm bands

I hopped about between both bands. On 13cm it was was nice to work Pete G4CLA again. Keith G4ODA was my best DX (longest distance) at 117 km. So my contacts were all pretty local really. I used 25W into the coax to the antenna box, so the Andew amplifier was under-driven.

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On 3cm, my initial contact was with Peter G3PHO. Our usual reflection point worked well to get round the hills. Keith G4ODA was my best DX (longest distance) on this band.

The rain was in the wrong places for rain scatter.

Denis G3UVR was much easier to hear on 3cm than on 13cm, and the dish is mounted a bit lower down than the 13cm yagi.

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26-November-2019 – my first contact on the 2.30 GHz NoV band

With the SG-Labs 13cm transverter in a box indoors, I can use a sub-band switch on the front panel of the box to switch between 2.30, 2.32 and 2.4 GHz. At 1870 MHz, the LO (Local Oscillator) frequency is rather low for the Microwaves Modules 70cm transverter (1870+430=2300 MHz) as I have not reprogrammed the SG-Labs transverter, so I thought the configuration might not work on the 2.300 to 2.302 GHz NoV band. I had configured the K3 with a 2300 band setting to generate the correct frequency on 10m band Intermediate Frequency (IF) feed to the 70cm transverter.

Using my Tiny VNA as a signal source, I found I could receive in the 2.30 GHz band.

I tried a contact on transmit with Keith G4ODA. It worked easily! Keith’s signal was very strong. I was using the Andrew linear amplifier producing about 50W, feeding the 40 el Wimo yagi through some metres of Ultraflex-10.

Really the SG-Labs transverter needs re-programming to give a more appropriate LO frequency, but it is nice that something works on the NoV band for the time being.

UK radio amateurs can apply for an NoV here for the 2.300-2.302 GHz band.

22-Oct-2019 SHF UKAC 3cm and 13cm

I worked a few locals on 3cm, collecting my partner from the station in between. I could just hear David G4ASR in the noise, but not strong enough to work. I had tilted up the dish a tad in order to clear the ridge of trees. Anything south is a problem. I failed with John G4ZTR. Kjeld OZ1FF didn’t respond to my meeps on ON4KST KST chat. So about 400 points on that band maybe.

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I had taken the relay box down from the pole the previous day for 13cm. That Tue eve I finally found the fault. I had added an LED to show when the relay was on transmit. This drew just enough current to have the side effect of latching the relay to receive (energised), so no RF out on transmit! I disconnected the LED & the relay worked. So I just lashed it up on the bench. I worked Denis on about 1W at the antenna. Then I cabled in the linear with some attenuation to get 20-25W for a couple more. I tried John G3XDY near the end of the contest and logged what I heard. Then I timed out.

Denis G3UVR was easier to hear on 3cm.

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I’ll try a low-current LED. If I get a good spell of wx, I’ll put the box back on the mast & get the pre-amp nearer the antenna. I haven’t tried the relay or pre-amp before. The Narda relay is nice & chunky, but its markings suggest it is only rated up to 1 GHz.  I may have made the Noise Factor worse on receive, but I have some more dB on transmit. I’ve included a Band-Pass Filter in the box, so that worsens the NF a little more.

At least all the control circuitry seems to be working: sequencing, 12V to the pre-amp, 24V to the antenna relay etc. The 40el Wimo yagi is back up on its jockey pole so I can do terrestrial 13cm again. It has been nearly a year since I started upgrading 13cm with a pre-amp and linear.

The SG-Labs transverter is now in a box in the shack, with reverse-polarity protection, sub-band switch: 2.3 Ghz, 2.32 GHz and 2.4 GHz, power switch, ref. osc. input switch, indicator LEDs power switch and a nice Anderson power plug. I want to add drive power switching and a monitor meter.

 

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.

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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.

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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’Hail 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.

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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.