Damn great thing arrived this afternoon by courier.  Clark SCAM 12m in decent condition but no legs or other accessories.  Plan is to mount it on a trailer or on the back of the campervan.  Fabrication time….

IMG_0459a IMG_0460a IMG_0461a IMG_0462s IMG_0463a

13cm receiver improvements

Completed DDK VLNA tuned up and on test.  Seems to have given me 2-3dB better S/N on the beacons. Should be even better when it is installed on top of the mast.


Using the VLNA, I was monitoring GB3BSS but it wasn’t on its usual 2320.923925 MHz, it was sliding LF at an accelerating rate.  It then picked itself back up and started moving back to the nominal freqency, where is has been for 30 minutes or more.  Very solid tropo signal from the beacon at 240km over a very obstructed path



The path to GB3BSS with earth curvature.  It says troposcatter loss is 208dB.


GB3BSS runs 40 watts EIRP, so +46dBm eirp,  My antenna has 16.5dB gain, I have 2.4dB feeder loss and maybe about 0.3dB in the relays and internal coax at the moment.  That means I would expect to see 46+16.5-2.4-0.3-208 or around -148dBm.  Sensitivity of this end is at least 15dB better than that, but I have some local clutter problems which explains why I’m only seeing about +8dB above noise on average.  I think the preamp is working!

13cm PA progress

Drilled and tapped the ally spreader plate and fixed the 13cm Spectrian PA to the spreader, the bolted it to the DB6NT watercooling plate.  Next job is to fix the power leads, input and output connectors and control connections.  Circulator needs plumbing in, then just pop the amp in between the transverter output and the antenna relay.


Completed PA assembly ready to solder the SMA sockets. This is a first fix, not slathered it in Arctic White thermal compound yet…


Initially I’ll use total loss cooling with a bag of water draining through the plate into a bucket.  Once all is well, I’ll plumb this in to the main fluid cooling system.

Building a G4DDK VLNA for 13cm

Nice little project this evening, 2.3GHz VLNA kit from Sam G4DDK. Comes as a board, tin box and bagged and colour-coded SMDs.  I hand-soldered all the SMDs with the help of my shiny new binocular microscope, needle-pointed thermostatic soldering iron and some 0.3mm solder. Finished thing is pretty small, 36 x 73mm



Close-up with my iPad, too much faff to get the SLR and macro lens out.


Next step is to fit the input matching coils, then the power lead and the RF-absorbent sorbothane  to keep the thing tame. Watch this space…

GB3BSS and GB3ZME are usually about 2dB over noise on 13cm tropo, with some peaks to +10dB from aircraft scatter.  I’m hoping the VLNA will pull that up by a few dB once I get the input matching right

The Shack – Ham Radio 2016 style

Another G4DDK VLNA on the workbench.  13cm this time…..


Remember the “Shambolic Shack” feature of the 1980s? Is this just a slightly higher-technology version?  This is the Engineering side of the G4DBN radio room, the operating position is to the left.  Repaired Kuhne 13cm transverter and Anglian 144MHz transverter on the operating table in front of the testgear rack


DB6NT MKU 23 G4 13cm transverter

Another new toy arrived today, the latest 13cm multi-segment transverter from DB6NT

Feels very solid and precise, reassuringly heavy

onnected to the DDK Anglian transverter

IMG_0426Output spectrum, 20dB attenuation external to the 8562A, so 27.17dBm output on 2320.200MHz.  Close-in noise about 80dB down at 5kHz.  The HP436A shows about 27.8dBm.  Second and higher harmonics are below the noise floor of the analyser.

2320 spectrum MKU 23 G4This is the SDR waterfall with a -156dBm carrier in to the 2320MHz RX input from the E4421B via a Narda 18GHz 20dB pad.


Binocular Microscope

I finally cracked and decided my eyeballs were not up to SMD work, and holding a magnifying glass was just too clumsy, so yet another bit of kit has appeared.  7x to 45x binocular microscope from AmScope. Very nice working distance and excellent clarity, at full zoom an 0805 resistor looks like a house-brick.  FOV at 45x is about 4mm. At 7x zoom, full frame is about 25mm diameter, with 100mm working distance.


13cm Spectrian amplifier

I bought an eBay Spectrian 75W amplifier for 13cm to go with the Kuhne transverter.  Spec says 26V at 16A, so the efficiency is extremely low, but it was cheap.  7 amps or so standing current. Thinking of watercooling it.  It has a thin copper heat spreader bonded to the underside of the PCB, so maybe OK just mounting it on an aluminium cooling plate, but I have a bit of copper bar that I can solder the water pipe to directly, so might go for that instead.  Transverter has not arrived yet, so having to test it with a CW signal from my Agilent E4421B