47 & 76 GHz outing to Notgrove IO91BV

 Originally I had booked the afternoon of Friday 25th June off work to go and watch a worcester T20 cricket game, but my ticket was cancelled due to covid restrictions. The question was what to do with the spare time? The answer was to persuade Noel G8GTZ to go out portable so we could try the Notgrove to Combe Gibbet path on 47 / 76 GHz, something we didnt really have time to try in the IARU 2021 contest

Noel managed to receive my pictures on both 47 and 76 GHz but I could not receive his DATV signals in the reverse direction. We did however manage an SSB QSO on 47GHz over the 67km path

The path towards IO91GI from IO91BV

My 47GHz signal as received by Noel

My 76GHz signal as received by Noel

IARU TV CONTEST 2021

Originally I ws not going to bother with this years contest, but after Noel said he was going to Dunkerry beacon there was a chance to set a few distance records if I went to Cleeve common, so i decided to venture out. 9 bands were packed (23cm, 13cm, 9 cm, 6cm,3cm 24GHz, 47GHz and 76GHz  and 2m FM). This number of bands would be quite challenging for the Portsdown software as it only has four transverter bands!

To get the best parking spot for the Dunkerry beacon path I went to Cleeve common early. Perhaps a bit too early considering the 1300 start time, but I used the time to go on an 8 mile discovery walk around the common

Two way TV QSOs were had with Noel on 23cm, 13cm, 9 cm, 6cm, 3cm and 24GHz. I briefly detected his signal on 47GHz but the river mist I saw on the path meant no two way qso. The only other station I heard on 2m talkback was G8GKQ but he was busy so I went home. Noel journeyed back to IO91GI overnight

5GHz and 10GHz point at IO81FD

The 23cm setup

On sunday morning I went early to cleeve common to try the path to IO91GI. I went man portable to the trig point and worked Noel on 24GHz at 0700z) but there were no signals either way on 47 GHz. I then retreated back to the car park and worked Noel on  13cm, 9 cm, 6cm, 3cm, By this time Cleeve Common was getting busy so I left and went to IO91BV.

Man Portable Sunday morning (note the shadow length!)

While at Notgrove my 7" display packed up (but not it;s touch screen!). With considerable effort (and Noels patience) we did manage qsos on 23cm, 13cm, 9 cm, 6cm,3cm and 24GHz

I was going to a third location to try it out, but with the failed display I didnt bother and went home. 

So I ended up with 16 QSOS, all working the same callsign! Activity was lower this year and being so far west denied me working the stations i worked when operating from walbury last year.

Another 47 and 76GHz DATV Expedition to IO91GI

 Noel, G8GTZ had let me know that on June 3rd he was going portable on 47 and 76GHz to Combe Gibbet, to allow G1EHF to try out his 47GHz QRP system to work G4LDR/P and G8ACE/P (who I hadnt worked ) on narrowband so I decided to tag along

Two way qsos were had with G4LDR/P SSB (at Stockbridge IO91GC68, 26km) and G8ACE/P on both 47 and 76GHz. My signals on 47GHz were so loud with Neil that even a conductive plastic bag over my dish couldnt eliminate signals at his end! I used my Langstone as the IF, the spectrum view was very useful for finding signals. G1EHF had his first qso, all before lunch, so we retired to the pub for a drink

Noel and I decided to try 47GHz DATV, to convince him his system was working. Although I had brought the portsdown, i didnt think we would be doing any datv so I hadnt brought the USB lead for the minituner. Fortunately G1EHF had a spare which I could borrow. 

Noel went off to Stockbridge IO91 while I returned to Combe gibbet. The langstone spectrum view helped find Noels drifting signal and a two way qso was had 

Noels 76GHz signal over 26km

Noels signal on 47GHZ on DVB-T

SEC1223 Power Supply Repair

 While using my SEC1223 Power supply to resurrect my Drake TR7 PA It suddenly started producing less output and tripping Amplifier alarms. To check the PSU wasnt current limiting I swapped to mydel 30A PSU and it behaved normally. I then reverted back to the SEC1223 and again the amp misbehaved maxing out at 20W. I then noticed that at this power the amplifier volts display was down to 7.2V when the current was 7A. Obviously the SEC1223 was ill

Searching the internet it appeared the most common cause of demise was the output capacitors failing, so I took the cover off

Indeed two of the three output capacitors had black goop on the top and were bulging. The capacitors are 16mm diameter and 29mm tall. I searched for replacements at the usual suppliers but did not find anything. Then I did an ebay search and found identical capacitors Teapo 2200uF 25V at £4 for 10 units so I got them. When they arrived they did look the same so I started swapping them:-

1. Remove the Mains connector and wires

2. Remove the 4 screws under the chassis holding the fan in place

3. Remove the 2 black screws under the chassis holding the internal heat spreader in place. This saves risking damaging the 3 active devices taking them off the heatsink

4. Remove the 4 screws holding the PCB in place.

It was then possible to manouver the PCB to get under the old capacitors off the board. Two of them had put black goop on the PCB that was cleaned off, but all three were replaced

After reassembly the psu produced 13.8V and using the K3S producing 100w output, the PSU only showed a drop of 0.3V at 20A output. Repair finished  

I will be taking a look at my other two SEC1223 to see if they have capacitors about to fail

Locking the Adalm Pluto to an external reference (Part 3; Software challenges)

 Having got the hardware finished it was time to convince the Pluto that it had a 50MHz NOT 40 MHz reference. This was easier said than done! 

It took 6 hours of internet research and trials before a working solution was finally found at https://tbspace.de/plutosdrclockinput.html  AND which would survive a pluto power down. 

The final solution was to execute the following on the pluto. No idea why it works or what it does, but it solved my problem

fw_setenvadi_loadvals fdt addr fit_load_address } && fdt get value fdt_choosen

/ fit_config }/ fdt && fdt get addr fdtaddr / fdt_choosen } data && fdt addr

fdtaddr }; if test ! n ${ad936x_skip_ext_refclk}; then if test n ${ad936x_custom_refclk}; then

fdt set /clocks/clock@0 clock frequency ${ad936x_custom_refclk}; elif test n

${ad936x_ext_refclk}; then fdt set /clocks/clock@0 clock frequency ${ad936x_ext_refclk}; fi; fi; if

test n ${model}; then fdt set / model ${model}; fi; if test n ${ attr_name } && test n ${ attr_val };

then fdt set /amba/spi@e0006000/ad9361 phy@0 ${ attr_name } attr_val };

fw_setenvad936x_custom_refclk "<50000000>"

To check if the changes were successful, we can read the device-tree:

cat /proc/device-tree/clocks/clock@0/clock-frequency | xxd

the response was

# 00000000: 02FA F080 .}x@

02faf080 is 50000000 in hex, Success

Having got the Pluto to work with the external reference I spent some time adjusting levels. It was suggested  on the internet that the pluto needed 0 to 10dbm to achieve lock but I found it needed much less than that, it would lock down to -22dbm input. I adjusted the output attenuator in the DFS50 to produce -10dBm output on mine

Locking the Adalm Pluto to an external reference (Part 2)

 Having worked out how to inject the external reference the next question was what frequency to inject. Should I use 40MHz like the original?  Looking in my junk box I found a G4HUP DFC30 unit which takes a 10MHz reference and provides a 30MHz output. I tried retuning the output filter to 40MHz but the multiplier was very ineficent at times 4. So i tried retuning the output filter to 50MHz which worked fine. The reference was to be 50MHz

In my parts collection I found a 10MHz oscillator which could be used to drive the multiplier when no external reference was available. It also had a relay to switch between internal and external reference.

The 10MHz oscillator and DFS30 as deployed in the Langstone:-

That is the hardware done, next to get the 50MHz reference in the software!

Locking the Adalm Pluto to an external reference (Part 1)

 Having finished boxing up the Langstone Transceiver  which is based on an Adalm Pluto SDR, the next step was to improve frequency stability.

Some have tried changing the reference 40 MHz oscillator to a more stable device. The preferred device is very small and i can imagine the damage caused by taking out the old oscillator.

Others have tried feeding in an external 40MHz GPS locked signal. One discovery from here was that the existing oscillator has an enable/disable pin so it can be left in place when an external signal is injected. This is thr chosen route

Note that C123 and C124 form a potential divider to reduce the output level of the oscillator. However C124 is not fitted but it does provide solder pads to mount another 180pf 0603 capacitor (I am not brave enough to try an 0402 size!) through which to inject the external reference

This is how mine ended up:-

Note that the braid of the coax cable through which the reference is injected is soldered to the groundplane in two positions. This is to prevent the 0603 capacitor being ripped off the board if the cable moves.

47 and 76GHz DATV Expedition to IO91GI

Having previously proved out the 47 and 76GHz equipment on narrowband modes it was time to try them on DATV. Advance planning with G8GTZ and G4LDR came up with some paths to try in and around IO91GI on October 14 so an expedition was planned

I left Malvern at 0815 aiming for Combe Gibbet IO91GI25 to meet Noel. G4LDR was going to the Stockbridge site IO91GC68.  My journey took longer than expected due to road works and I arrived at 1030. 47 GHz narrowband signals were very loud on NBFM both ways and a two way DATV QSO was easily had. Moving to 76GHz. I eventually had a two way qso with Neil (after finding a field solution to the transverter sticking on transmit with no IF radio attached) and Noel received G4LDR/P but could not be received by Neil. As time was flying by and the road would have tractors on it at 1400 (the local land manager told us) we decided to go to the next site

Combe Gibbet 47 and 76 GHz

Combe Gibbet 76GHz 

G4LDR 47GHz received at Combe Gibbet

47 and 76GHz at Combe mast alongside G8GTZ 76GHz

G4LDR 76 GHz received at Combe Gibbet

Neil went to the Butser site IO90MX13 while we moved across the ridge to the Radio mast site IO91GI61. Narrowband signals were loud both ways on 47 GHz and a two way DATV qso was had thereby extending the UK 47 GHz DATV record to 51.8km.  76 GHz narrowband signals were good both ways on both mine and Noel's systems, but at this point the damp weather arrived, not good news for 76 GHz propagation. The optical path to G4LDR/P disappeared in the mist along with any hope of any DATV qsos.. It then started to rain so the attempt was abandoned at 1650. Due to rain and roadworks I got back to malvern at 1900.

G4LDR 47GHz received at the Combe Mast

BATC 2020 50/70MHz Contest

Having participated in the BATC 144/432 MHz contest (and won it) It was time to think of the upcoming 50/70 MHz contest. Originally slated  for September 19 and 20, after I pointed that the sunday clashed with the RSGB 70 MHz AFS contest it was changed by BATC to a saturday 1300 to 1900 contest. As the IO82lB site, used for the 144/432 contest has interference on 70MHz somewhere else was needed. The previously used IO82QL Titterstone clee site was chosen

The thought of putting up a 5 ele on  6m and a 5 ele on 4m was discounted  quickly. I remembered that back in 2014 I bought an Innovantennas  dualband 4 ele on 6m and 4 ele on 4m antenna so that was unpacked (for the 1st time) The assembly manual wasnt very helpful, but a few emails to Justin got the answers. The boom and 4m elements fitted in my car, but one end of the 6m elements had to removed so it would fit.

Arriving on the site around 1000 it was found to be very very windy. The HF dipoles of the IOTA contestants were blowing all over the place. The possibilty of not being able to put up the antennas (one for the 50/70MHz yagi one for the 144/432 talkback colinear) was considered. As a test the 4/6m antenna was assembled on the mast and eventually raised to the skies. The swr was 1.8:1 on 6m and 2:1 on 4m but this was not a day to adjust antennas. It ws decided another mast was too risky so 2m talkback ideas were abandoned!

Had a 2 way on 4m with G8GTZ (MER15) Tried on 6m, Noel copied my signal easily but due to loud interference coming from the radio station at the bottom of the band I struggled to receive him, but eventually I copied him at 66ks near the top of the band (for my only 2 way QSO). Worked G0MJW on 4m (MER6). Due to the fine work of Noel acting as a Zello to 2m transponder, hooked up with G8VPG and had a 2 way with him on 4m (MER 16) When he turned his beam on noel he was still MER8 with me! Tried 4m and 6m with M0DTS with no luck, but my 4m signal was detected!. Worked Arthur G4CPE (for the 1st time!) on 4m (MER peaked at 7.5) at 156km for my best DX. He could not copy my 6m, probably due to cross polarised antennas. Copied Noel at MER6 when he transmitted 4m at Arthur! Managed to get my 6m received by G0MJW in the final act of the day

On 4m used Portsdown 2019 +modified G4DDK nacton 437/71MHz transverter + MITSUBISHI brick (20W) +minituner. On 6m Portsdown 2019 +modified G4DDK nacton 437/51MHz transverter + 7w MITSUBISHI brick+LDMOS amp (150W; the bigger amp is locked down in wales)+ minituner

G8VPG/P 120km on 4m showing intended loc.

G4CPE 156km on 4m

G8GTZ/P 141km on 4m

G4MJW 127km on 4m


The results  were subsequently published and came as a bit of a surprise with a win and a trophy!

My first 47GHz UK QSO

Having put the 47GHz system in a box it was time to try it out. An opportunity arose with the upcoming 47/76GHz contest so a visit to Cleeve common IO81XW was organised

As GW3TKH was going portable on the Blorenge IO81LS I Initially set up on the west side of the summit. We first tried on 24 GHz and signals were huge both ways on NBFM with both GW3TKH/P and GW4HQX/P. Moving to 47GHz signals were equally loud on NBFM  both ways with GW3TKH/P but I had to resort to SSB to work the GW4HQX/P QRP

47 GHz transverter on top of 24GHz Transverter

47GHz takeoff towards The Blorenge

 As there were no others on 47GHz I packed away that band and went manportable on 24GHz from the trig point and worked another 5 stations including the best DX of G8GTZ/P at Walbury at 74km to achieve 3rd overall place