47 and 76 GHz man portable on the Malverns

 

As G8GTZ and G8GKQ were going to the Midlamds Convention at Eaton Manor, it seemed the ideal opportunity to try to extend the 76 GHz record distance record. They would go to Titterstone Clee amd i would go man portable on the Malvern Hills. The hereford beacon would be ideal, but it has steps to the top, not ideal for towing a fishing trolley. Eventually a location on Black hill was found which was just an uphill slope approach from the North Hill car park

Having done my stint on the 160m ARRL contest from Florida i set out at 1200. The weather was ok and the RH was only 61%. However when i got to British camp it was very windy (gusting 35mph!) and was very cold. I set off up the path. Very shortly afterwards the bottom of the plastic container fell out and one battery landed on the floor. I proceeded with just one battery. Going to the summit of pinnacle hill was impossible due to the wind so i found a lower location IO82TB96 which still had LOS to Titterstone Clee IO82QJ85. 

First we tried 47GHz and i received the loudest narrowband signals from Noel I had ever received from any loaction. A 47GHz DATV qso was easily had. We tried 76GHz but due to the wind it was impossible to keey the dish pointing corrrectly so the attempt was abandoned

Talkback was an issue. My ic706 was too heavy and my only ht did 2/4m, previously we had used 70cm. We tried to use the phone., I had coverage but Noel had flakey coverage which made coordinating an issue system. Time to look for a new HT for these occasions

Obtaining Accurate frequency spots from the RSP1a and skimmer server

 As my Anan-10 is often used as an HF multiband panadaptor (to see which bands are open) rather than a skimmer I needed to deploy another SDR as a cw skimmer. I had a spare RSP1a so decided to try that, even though it is in a plastic box!

Firstly the sdruno and api were installed from here, which made sure the rsp1a drivers were installed. Next the skimmer server was installed from here along with the needed SDRPLAYintf files to allow skimmer server to speak to RSP1a. The aggregator software was also installed from here to allow spots to be uploaded to the reverse beacon network.

The cw segment on 40m (outside contests) is narrow so only a 96kHz bandwidth (as is done on the anan-10) was chosen in the skimmer server settings and the system left running overnight

The following morning I examined the spots but found they had a random frequency error compared to other stations spotting the same station (eg ka9zap was -11.6 kHz, k3wjv was +2.1khz, k4ees was -0.3khz)

I wondered if the issue was band sensitive, so the following evening i skimmed 80m. The errors were similarily random.

I did a web search to see if anyone else had suffered the same issue, but found nothing. However I did find a page in Spanish by EA2NN showing he had succesfully used skimmer server with an RSP1a. I did however notice that he had set the skimmer server bandwidth to 192kHz so i thought it was worth a try.

After making this change all spots were within 100Hz of everyone elses spots on 160, 80 and 40m. The problem had been solved!

Note that in the skimmer server ini file you can define the frequency range that cw signals can be decoded (less than 192kHz!)

I also discovered that if you have the skimmer looking at 3 bands (the maximum it would appear from an RSP1a)  the default is that it skims 2 minutes on the 1st band then 2 minutes on the 2nd band then 2 minutes on the 3rd band before going back to band 1, so if you generate a local test signal locally it may take 6 minutes before it finds it!

Now to put the rsp1a in a metal box. I may even add an RF relay to the box so the input can be terminated on transmit!

47 GHz and 76 GHz DATV outing

 

Having failed to work 76km on 76GHz from the Blorenge G8GTZ and I decided to try some shorter paths

The first one was from Hackpen hill IO91CL to IO91GI Combe Gibet. I had never been to Hackpen, but I had previously worked it on 47 and 76GHz narrowband from Cleeve Common so I went there. When I arrived there was mist on the horizon towards Combe, but it slowly cleared and QSOs were had on DATV on both bands over the 26km path

I then travelled to Combe masts IO91GI61 and met with Noel and I worked G1EHF/P using fleapower on 47GHz. . With sunset being around 1615, and wanting to try another path of 35.6 km we forsook a pub lunch and had a sandwich before Noel went off to Cheesefoot IO91JB. I returned to the Combe masts. To save time we started on 76 GHz and a 250ks qso was had, even though there was a lot of mist on the path.

47and 76 GHz from Blorenge after the CQWW RTTY contest

 As I was off work for the week after the CQWW RTTY contest and was passing the Blorenge on the way back I wanted to try some more 47/76GHz TV. Noel G8GTZ was persuaded to come west to be the target

Arriving at the Blorenge at 1100 in high winds and rain squalls, we first tried the path to Birdlip, IO81WU at 67km  Two way qsos were had on 47GHz NB easily. I received Noels DATV signals easily but Noel was having trouble receiving me. After a lot of unsuccessful experiments, in desperation I reprogrammed the Lime to normal software and changed the Portsdown  setting from "Line DVB" to "Lime Mini" it all worked fine again. Two way 125ks DATV qsos were then successful. We then started on 76GHz but as s storm cloud had just come through and sat on the path no signals were received by Noel through the rain 

By the time Noel got to IO81XW81 the rain had cleared. Two way 47 GHz QSOs were had on DATV at 125kS at 74km  76GHz was a bit more cooperative with a two way NB qso but not good enough for Noel to receive my high power DATV 

CQWW RTTY 2021

 

For a change this year Roger and I decided to try the MS section from MW2I. Having read the rules that MS doesnt really mean MS we set up the second K3S as the mult station. It didnt go quite to plan as the K3 went into "Hi sig" error mode and that was the end of that idea This is exacty the same issue as I had previously as recorded in my blog  where Q8 and Q9 had blown

So we ended up doing Multi op single radio 2 computers!

80m  dipole
40m rotary dipole
20/15/10 A3SDX 

The anan-10 rtty skimmer had a wellbrook loop for LF and a 12AVQ for the higher bands and proved its usefulness (it didnt capture G8S though)

Conditions were good. More  JA worked on 40m than we knew existed, along with KL7 for a new DXCC. 80m was very good into W sunday night and after many years of trying a new DXCC ....GJ!. Only gotaway was PZ5RA on 10m during the brief opening Sunday afternoon

 Band     QSOs     Pts  ZN   Cty  SP   Pt/Q

   3.5     333     700   11   52   14   2.1

     7     725    1697   23   75   40   2.3

    14     705    1713   25   70   50   2.4

    21     358     937   27   58   42   2.6

    28       5      11    4    4    1   2.2

 Total    2126    5058   90  259  147   2.4

Score: 2,508,768

As Roger said afterwards, "It is a long time since we did all 48 hours of a 48 hour contest" . Luckily I am on vacation this week so I can recover

After returning from the contest I replaced Q8 and Q9 in the K3S. I also changed the three resistors to the values Elecraft finally settled on see https://g4fre.blogspot.com/2018/08/k3s-hi-sig-warning.html.

Plisch 432MHz amplifier module

 When I visited Frederichshavn in 2018 I purchased some small Plisch dual BLF861 device 28V 432 MHz amplifier modules  which had been used in TV trasnsmitters. I also got a larger two stage module with a single device driving  the same dual BLF861 devices.

When I returned I tried using the dual stage device but it saturated at 100W, even after doing the published modifications to the output stages at http://pa0ehg.com/70cmpa.htm and help from G4ERO. So the project was put to one side

I recently rediscoverd the modules and decided to try again, firstly with the dual device modules., With the same modifications I again got 100W output with 4W of drive. with each dual device set to 1A standing current.  I then reread the modifications and realised a PAIR of 5.6pf ATC capacitors were added across output capacitor, not a single one like I had been doing. Adding the capacitors and retweaking the input variable capacitor resulted in 190W output with 5W of drive, which is generally considered to be normal

A summary of my mods :-

Remove C62 and C63 (3pf)

Remove C7 and C27 (5.1pf)

Add TWO 5.6pf ATC capacitors across C9 AND C29

Add 22pf trimmer across C2 and C22

Add a 2N7000 FET at to turn the bias OFF on receive by earthing C19 V7 base junction (needs 5V on gate on receive)

The module after modification

Next task was to put it in a box. I did find the chassis from the defunct 6m 300W amp with coax relays and PIC controller so decided to repurpose it. 

The completed amplifier (with lid off module)

PortsLang 4 Hardware Updates

 Having used the PortsLang 4 for a while I decided it needed 3 main improvements:-

1. The mouse for tuning works ok but is a bit clumsy and occasionally misses pulses

Fitting am Arduino Pro micro board emulating a USB mouse s described  at   https://wiki.microwavers.org.uk/Langstone_Project  with an Optically coupled encoder fixed this issue in my Langstone so the technique would be used again, There is not enough room for a turning knob on the Front panel. An external solution would have to be used.. The mouse simulator was built with 3 switches an an optical encoder in a small diecast box, allowing it to be plugged into the back panel of the PortsLang

2. The Adalm Pluto Oscillator drifts and has a frequency offset

This is not an issue in my Langstone as it has enough room to put a good oscillator and multiplier in the box.  There isnt enough room in the PortsLang to do that. Measuring the output frequency of the PortsLang showed the oscillator settled down 33kHz high at 437 MHz which was unacceptable. I had previously bought a couple of  the recommended replacement 40 MHz oscillators from Mouser, so decided to swap it out. The existing oscillator was carefully removed from the PCB with two soldering irons and the new oscillator soldered in place . Unfortunately when removing the original oscillator solder flicked onto the oscillator output capacitor and whilst removing this solder the capacitor vanished. A new 18pF 0402 capacitor , While I had the board out I also added the PTT output relay described at https://wiki.batc.org.uk/Custom_DATV_Firmware_for_the_Pluto#PTT_output

Measurements now showed the oscillator was now within 200 Hz at 437MHz without tweaking the Pluto calibration.

3. It has no speaker so a headset HAS to be used to listen

I had built a speaker into my Langstone so I could hear the signals when peaking a dish without tripping up on the headset lead. There was not enough room for a speaker in the PortsLang so an external box  was needed. Looking in my Junkbox I found a 12V 18W audio amp module, volume control,  a 2" speaker and a suitable plastic box, I built the amplified speaker with a DC connector to allow it to be powered from a 12V output from the PortsLang 

Upgrading my Portsdown 4 to become a PortsLang 4

Inspired by a post by G8GKQ about new features available in the latest Portdown software release I decided it was time to upgrade my Portsdown 4 to enable it to be used as a Langstone on Narrowband modes, saving an extra box when man portable. The main change is the SDR is changed from the LimeSDR to an Adalm Pluto SDR. Looking at the benefits of the change revealed the only feature I would lose would be the Lime spectrum view which is not available on the pluto

I did have a spare Adalm Pluto obtained secondhand from HRD. but it was still in its plastic case. First task was to house it in a metal box which was much easier the second time around. Fitting it inside the Portsdown necessitated moving the antennuator board 1cm towards the front panel, which took much longer. 

The Langstone mode requires a "USB mouse" tuning knob and a USB sound card which would require additional USB ports (the RPI4 only has 4). I dug out the old USB3 powered hub and refitted it. I also found a dual port USB extension cable that allowed two of the ports on the hub to be accessed on the Portsdown rear panel.

The USB soundcard required fitting two 3.5mm stereo sockets for mic and phones to the rear panel to allow external access for a boom headset/microphone. A phono soocket was also added for a footswitch input to put the Langstone on transmit. The audio connector for the RPI audio output was kept.  All these additions made the portsdown rear panel crowded!

One great feature is that the band data pins on the RPI GPIO can be accessed from both the Portsdown and Langstone software so the band decoder can drive the 8 port RF switch and external transverter interface from both

Internal View

Rear panel is now very crowded

The powered USB and the Langstone USB soundcard

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