First steps with 10 GHz from the new QTH

With the winter finally loosing its grip and spring upon us I managed to get some concrete in the ground for the tower base and get  the base post down for the Radio Structures 18m HD tower which has been sitting in its crate at Roger ZL3RC’s while we bought some land and got our new house built.

The tower is a replacement for one I lost in a North West storm at my old QTH in West Melton a few years ago. The new tower is a properly constructed lattice tower on a heavy duty baHD Towerse plate, which will be large enough to carry my EME arrays. For now though I have been concentrating on building the shack and sorting out what cabling I need in place, no mean feat for a brand new house!

The base is pretty hefty, and is a solid, reinforced block, about 1.7M x 1.7M x 1.6M – a lot of concrete! Properly overkill but to be honest I’d prefer to sleep better knowing its well weighted, even though the tower won’t be up in any storms (I hope!) The base plate weighs probably around 600 Kg – put it like this we needed a HIAB on a truck to lift it on the bolts! The tower is a 3 section heavy duty model that will take anything I care to try and load it with!

We dug the hole with a small digger, at least my friend did who can really dig a square hole, minimising the amount of concrete needed in the hole! Roger and I built a reinforcing cage from surplus material left over from the house build (clever me for stopping them throwing it in the skip!). I got some hold down bolts made locally and got them plated to minimise rusting.

With a truck load of concrete down the hole (30 MPA) I left the base for a few weeks before we got the truck back and HIAB’d the base on – with a bit of fine tuning from Mark, my welder chap, we then bolted the base down and HIAB’d the mast on and pinned it. I have to say using the HIAB was awesome and effortless, good as I would have been on my own trying to do that, an impossible task.

With the tower on I luffed the tower up and then left it a few more weeks before I was tempted to start thinking about warheads!

The tower will be destined for EME on 144/432 but I quickly realised my small SPID RAS AZ/EL rotator wasn’t going to be cut out for this job, so I wired up the Big RAS/HR SPID I have spare that was on my 3.7M dish (now I’ll be using the 5.2M dish so that needs a bigger tracking system so this is spare) – Problem…. wiring this up revealed a really noisy AZ motor and after talking with RFHamDesign they decided to send me a new motor – but thats at least 10 days + delay for me. OK so in the meantime I wanted to do a check on 10 GHz for the new ZL2VHX beacon at Mount Climie, about 375 Km north of me.

I haZL2VHX 3cm Beacon ve a 10 GHz transverter I brought with me from Europe but I hadn’t got round to running this so digging that out I ran some checks and it looked good. I mounted up the smaller RAS SPID and ran some wires out and set up the system on the weekend. Sunday afternoon I was ready to test.

Initial views showed no beacon. Hmm. I was pretty convinced I should hear it. It runs 8W to a 16 slot WG omni and has a clear view south at its home 870M ASL on Mount Climie. So I dropped the mast again and took the transverter into the shack.

Doing some further tests I realised the IF gain was low and using the small internal pot I added some gain. I also changed a cable I suspected was causing me issues, as putting my hand over the feed I could not see any change in noise, a sure sign of poor sensitivity.   With the IF gain upped and cable changed I could then see a change in signal with my hand over the feed. I buttoned up the transverter and rehomed the transverter on the mast and wound the tower back up (I’m getting some good arm exercise!).

I had previously sort of found my AZ off the sun and found a weak peak on EL and set that to the correct angles, so I parked the dish on what I thought was the right heading. Nothing.

Hmm OK, my transverter was running unlocked for this so opening the panadapter out I saw a strong birdy about 10 KHz higher than the beacon frequency, my heart missed a beat, was that ZL2VHX? Quick swing of the dish, it disappeared! Ahhh this looked promising. Slowly peaking the signal back on the dish, the signal suddenly started sending JT4G tones! Bingo!

I spent a while just tweaking the dish and getting a feel with azimuth settings to ensure I was on target. I tweaked the elevation and minimised ground noise while peaking the signal. OK, time for a celebratory coffee!  Now, time to break out WSJT-X.   Many modern beacons have adopted JT4 as part of their beacon routines. ZL2VHX at least spends a lot of time on carrier which is helpful when peaking the dish or tweaking transverters.

The Flex 6500 has a great system called Digital Audio Exchange or DAX for short. This virtual audio cabling means I can route audio from the Flex 6500 on the other side of the room to a remoted PC running SmartSDR and DAX and feed this into WSJT-X without a physical cable in sight.

Setting WSJT-X up and making sure I was aligned with the 4 tones, I let WSJT-X run till the next JT4G period. The four tones of JT4G have been designed to handle the wide frequency spreading that is found on the microwave bands (more on this later) – Zl2VHX kicked into JT4G and I could see 4 clear tones – wait till the end of the period and …. yes! There it was!

Awesome! Not bad for a 370 Km path under flat bands. Great – another celebratory coffee!

The decode shows a signal around -17 dB in a 2.7 KHz bandwidth – thats about +10 dB in CW bandwidths – quite acceptable!

0734 -17 1.0 981 ZL2VHX RE78NU

So now I spent some hours tweaking and playing with gain settings and display settings in SmartSDR until I was happy that I was seeing the best I could. And that’s when mother nature decided to throw me a bone!

I noticed that spreading was getting wider on the signals as time was progressing, did we have some rain on the path?   A quick check on the NZ Metservice website showed a very active front coming in from the NW. Yup this could be fun!   You can see the rain in this image from the Metservice radar.

The red line is my path up the coast to ZL2VHX. The large active area of rain to the NW of the beacon was allowing me to see rainscatter while 15 deg off axis. Peaking back on the beacon spreading was getting worse with smearing of the tones between 50-100 Hz. As this was happening signals were getting louder with a peak as the rain band moved into the direct path. Smearing reached over 100 Hz at the peak. As the rain moved steadily eastward signals dropped off and the smearing reduced. Show’s over for tonight but a great first showing from the new QTH and I am very pleased!

Here’s an audio clip from the proceedings.


So what’s next?

Well I will continue to tweak 3cms and wire up transmit now to the transverter and set some tx gain settings. My AZ motor might arrive in the next week and then I can get the EME array up and I have ordered a 1M dish to sit inside the main array so I can continue on the 3cms adventures. 10 GHz is a great band and a lot of fun, I have missed it 🙂

More soon as I continue to develop the station.

73 Simon ZL4PLM


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