Thursday 26 November 2020

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

 Having got the hardware finished it was time to convince th 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  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

Sunday 22 November 2020

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!

Friday 20 November 2020

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.

Thursday 15 October 2020

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

Tuesday 22 September 2020

BATC 2020 50/70MHz Contest

beaming at G4CPE, Malvern hills on horizon

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!

Low Band 2020.gif

Thursday 17 September 2020

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

Monday 14 September 2020

My First 76GHz UK QSO

 Having assembled the transverter in a box as described here it was time to try it out. An opportunity was  found with the upcoming 24GHz to Light contest so an outing was made to visit Cleeve common. As the weather was going to be good it was decided to visit the trig point IO81XW90 with its good all around coverage.

qsos were easily had with GW3TKH/P amd GW4HQX/P when using the 12" Procomm dish

Sunday 13 September 2020

Housing the DB6NT 76GHz Transverter

Having also bought a DB6NT 76GHz transverter recently I decided it was time to be put in a box and join it's 47GHz cousin in the field.

It was found that the same size box as used to mount the 47GHz transverter would be suitable. However,  how to get RF signals in and out would be a challenge. After a long search a pair of 90 degree WR15 H plane bends were found on Ebay. They were similar but not identical in dimensions. These would allow the transverter to be mounted on the base of the box with the waveguide bends poking through holes in the sidewall.

The box was fitted with a an N type socket for the IF and a TNC socket for the 10MHz reference. A 3 pin XLR was used for the 12V power. A power LED,  lock LED and transmit LED were fitted

The local oscillator was mounted directly on the base of the box alongside the transvreter. As the 76GHz portion of the band used in the UK is 75976 MHz and the transverter has a 144MHz IF the local oscillator was programmed for 9479 MHz. Note that this is not an available standard frequency available in the MKU oscillator. I chose to reprogram the unit and replace the existing 9486 MHz 76 GHz LO with the 9479 MHz one.

The transverter has an RF output power Indication  which was connected up to my usual LM3914 and 10 LED bargraph indicator. Initially this was mounted inside the box on the local oscillator but it was found after its first outing to be more useful if visible from the outside ao a hole was filed and the unit mounted.

Wednesday 9 September 2020

Housing the DB6NT 47GHz Transverter

 Having bought a DB6NT 47GHz transverter last year I decided it was time to use it, especially as I had a pair of W1GHZ horns that would avoid the need for a T/R relay.

Finding a big enough waterproof box for the xverter module was an issue but one was eventually found that was a close fit. It mounted fine in the box but the SMA plugs on the ends made it too long. Using a dremmel some of the inside walls of the box  were removed and it just fitted, even if the SMA plugs could not be unscrewed in situ!

The transverter was mounted "labels down" on flat base of the box with holes made to line up with the TX and RX waveguide ports

The local oscillator was mounted directly on the base of the box alongside the transverter. As the 47GHz portion of the band used in the UK is 47088 MHz and the transverter has a 144MHz IF the local oscillator was programmed for 11736 MHz. which is one of the available pre-programmed frquencies

The box was fitted with a an N type socket for the IF and a TNC socket for the 10MHz reference. A 3 pin XLR was used for the 12V power. A power LED,  lock LED and transmit LED were fitted.

The transverter has an RF output power Indication  which was connected up to my usual LM3914 and 10 LED bargraph indicator. Initially this was mounted inside the box on the local oscillator but it was found after its first outing to be more useful if visible from the outside ao a hole was filed and the unit mounted

Thursday 13 August 2020

BATC 2020 146/437MHz Contest

 BATC announced a dual band 146/437 Dualband DATV contest on August 8/9 . Dorstone IO82LB was the obvious choice but due to other commitments only operation on Sunday 9th was possible. As G3UKV would be out portable on 5GHz FMTV equipment for that band was also taken

G8GKQ/P was easily worked on both 2m and 70cm IO81UC 118km. I could see his 5GHz FMTV signal but he could not copy my 8W signal.

My signals were successfully received by G3VKV (IO81XV) at 71km

M0YDH/P (IO82QL) was worked on both bands  along with G3UKV/P at the same site on 5GHz FMTV at 54km

G4CBW/P (IO93AD) was worked easily on 432MHz but it took 25 minutes to complete the QSO on 2m due to QSB at 141km

Finally my signals on both bands were received by G4NZV (IO82WA) at 63km. An interesting outing

The equipment on 144MHz was a Portsdown 2019+ 30W Mitsubishi brick to a 9 element portable tonna at 4m. On 437 MHz a Portsdown 2019 + Mitsubishi 7W brick + 400W LDMOS amp into a 21 element Tonna at 5m

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

Monday 15 June 2020

IARU TV Contest 2020

For this years IARU ATV contest I decided to get a bit more active than last years 2 QSOS and go portable at three locations :-


Left home at 0800 and drove the 84 miles from home to Walbury hill IO91GI (thanks to Noel for the opportunity to use the site while he went elsewhere) Having never been there before it was a bit tricky to find, but the photos from google maps Noel supplied helped. 

Having 7 TV bands plus 2m FM talkback setting up the equipment took a long time, At the start of the contest worked G8GKQ/P on all bands 432 to 24GHz at 54km.

Worked G8LES at 40km on 23 and 13cm and he received my signal on 9cm (he has no transmit on that band) 

Worked G8GTZ/P at 51km 432 to 24GHz except 13cm (equipment trouble his end).

Transmitted my signals successfully to G4LDR at 30km on 24GHz to 9cm during some huge rain storms which forced a couple of hasty retreats into the car. Could lock to his carrier on all bands but got no further than Carrier and FS lock.  Did have a two way on 13cm with him

Drove back home arriving at 2240


Left house at 0700. Arrived at cleeve common car park IO81XW at 0800 

As a new location the rules said I needed new contest numbers in the Portsdown 2020. No problem I thought, I have previously saved a suitable new set to USB drive. Imported them but subsequently not even the Portsdown touchscreen would respond. After much searching found ethernet cable and did a factory reset via SSH. Manually set all parameters. Lost 2 hours so no time for expedition to trig point for LOS 24GHz path.  Worked G8GTZ/P at walbury at 76km on 13cm to (surprisingly) 10GHz,   Just not enough signal for 24GHz.  Location getting overrun with visitors so left at 1200

Drove the 29 miles to Notgrove, IO91BV, a site that should have a good path to Walbury (and would not be crowded!!) 

The Membury TV mast can be seen through the gap

Decided to change the contests numbers manually and avoid risk. Worked Noel at 67km 23cm to 24GHz. Signals were not too loud on DATV but huge on 24GHZ NBFM.  

Worked G0MJW with big signals both ways on 70cm and 23cms. 

Saw signals from G4CPE on 70cm but couldn’t attract his attention with my 5W Tried getting signals on 70cm to G3VKV but path too blocked locally. Good signals on microwave bands from GB3ZME 3 and 5 GHz but too late to work the M0YDH/P in that area. Did hear the GB3LPC beacon on 3.4GHz narrowband for the first time.

Sunday 10 May 2020

GM3SEK Mains filter finally finished

Having heard about the GM3SEK mains filter at the RSGB Convention 2019 and seen the design on his  web site I had decided to build one. I gathered most of  the necessary parts after Christmas. The one missing item were cable ties with screw holes to hold the ferrites in place. I finally found some on ebay so set about assembling. I decided to fit a 16A chassis mount plug and socket on the box to make it more transportable, the mains input and the distribution panel output having connectors to allow easy disconnection

Sunday 19 April 2020

WKUSB-SMT lockup

I have used winkeyers for many years now, ever since building a serial version board to take on the 3B9C expedition without any trouble. While setting up a WKUSB-SMT at the MW2I station recently it refused to respond after a run on 20m. It appeared on the virtual com port but refused to respond to the wk3demo or wk3tools programs. I thought a reset was needed, but the manual was not very helpful as it suggested hitting the reset button when connected to the keyer, which I could not do. So I left the problem and substituted the spare winkeyer a  WKUSB-DIP which worked fine.

A few days later I found the document  on the winkey website which had a very interesting paragraph:-

There have been cases where a WKUSB‐SMT has entered a lock up state due to a nearby lightning strike, a high RFI field, or other very unusual situation. In most cases the WKUSB can be restored to normal operation by pressing and holding the red pushbutton for about six seconds until it responds with an R followed a few seconds later with an OE (dah‐dah‐dah‐dit).

This technique was tried and the WKUSB-SMT recovered. It did reset the EEPROM so all settings had to be re-entered, but the crisis was over!  Pity this information is not in the manual!

Saturday 15 February 2020

The Langstone Narrowband Transceiver with Pluto and RPI 4

At the RAL TV meeting last year G4EML demonstrated a narrowband transceiver ("Hayling") using a raspberry Pi 4 a 7" LCD screen USB soundcard and an Adalm Pluto. Talking to G8GTZ at the recent Didcot Rally I found that the code has been uploaded to github ("Langstone")so on my return from the rally I decided to try it out.

The first attempt at building the code resulted in a no frequency display on the screen. The log seemed to be objecting to my USB sound card, so I changed it for another one I had and I was getting  the frequency readout but no audio

I then noticed that the display seemed to think I was on transmit. I consulted with G4EML and found that there should have been a pullup resistor on the GPIO PTT input pin. With this modification the display indicated RX and i got receive audio and could hear signals

I took a listen to my transmit signal. The dots sounded fine but i discovered the centre button on a 3 button mouse was needed to send CW, which I didnt have. I got no audio on transmit until I discovered the USB sound card mic input needed a computer headset (electret) microphone rather than my (dynamic) heil headset 

To try it out on the air I hooked up a 3W 1296MHz module and had a nice 2 way qso with a local on the band

I mentioned my findings to G4EML who updated the code to have a key input and a PTT output to drive an amplifier. He also added band output pins to auto switch external amplifiers and preamplifiers

I was then interested  to see how the system would work as a microwave IF. I connected it the radio on 144MHz to my 5760 to 144MHz Transverter and could hear the GB3OHM beacon on 5760.9MHz on a horn antenna. I then realised the pluto works directly on 6cm so I connected it directly to the horn antenna and could hear nothing. I then used the KX3 and the transverter to calibrate the Pluto and found there was a 65kHz offset, on which frequency I could just detect GB3OHM. I dug out a DEMI ATF36077 preamp and put that infront of the Pluto and the beacon became quite readable

All that is needed now to make the rig suitable for portable operation is a panoramic display!

Wednesday 29 January 2020

CQ160 contest 2020

Having had so much fun in the ARRL 160 contest I returned do the CQ 160 in January from DEMI. To avoid the previous issues with connecting in Charlotte I flew on an American Airlines codeshare flight which was on a BA plane direct from Gatwick to Orlando, arriving early at 1430, Steve and Sandy met me at Orlando and after a fish supper we drove the 3 hours to Live Oak.

The rules for this contest are not quite the same as the classic CQWW rules. Multipliers are US states+VE provinces+countries. Although DX stations (and only DX stations)  send their zone, they dont add to the  multipliers!

The contest started at 1700 local on Friday under the call K0DI. Unfortunately the starting operator was stuck on a plane at the gate in Washington, so I was volunteered to start. Calling CQ for 10 minutes, nothing much happened, then the pileup started, which was a new "run" experience, which I continued for 2.5 hours before switching to mult duties retiring at 2300 I returned at 0600 and operated till the band closed at 0830 working some JA but no VK/ZL

Having not experienced the overnight shift I returned at 2300 to teamup with Steve. I ran , he searched. I ended up running for 8 hours. The band closed around 0800 sunday morning again . We resumed at 1600 that afternoon  after a visit to the club shack and surprisingly had 17 qsos in the last hour

For light entertainment on the monday after the contest we replaced the power supply in a quadra VL1000 amplifier which had been hit by lightening.