Wednesday, February 7, 2018

432MHz AFS 2018

The final leg of the RSGB as usual is held in February starting at 0900, meaning waking up at 0500! This would be the first opportunity to try the newly built G4DDK Iceni 432MHz Transverter, along with the K3S, solidstate amplifier, HA8ET masthead Preamp and a 20 element yagi at 20'

As the first 2 hours overlapped a French Cumulative contest there was some interesting DX to be worked, which made up for the lack of ANY DL/ON/PA stations! There were a few snow flakes before and after the contest but during the contest freezing feet were the main hazard

The only equipment issue was the audio from the K3S. At times there would be buzz on the monitor audio on transmit. The monitor was set at level 2 and the buzz was equally as loud Eventually it was correlated with the fans running on the K3S.  The fan was running more often than previously as the Iceni was placed on top of the K3S, as shown above.

Searching the Elecraft website after the contest revealed there was a mod for this issue, although they were slightly confused as to whether the hum was on transmit or receive. The fix was a 470uF capacitor mounted on the KPAIO3. The modification was done and the issue resolved

The equipment seemed to have done the trick, again we won the open section:

Resulting in a winners certificate and , in conjunction with other Bristol contest group operators won the G0ODQ Trophy. Perhaps it was worth getting up at such an unearthly hour!

Thursday, February 1, 2018

10MHz Distribution Amplifier

I have had a need for a distribution amplifier for a while now. Searching around I found the design by G4JNT in Radcom, which filled my needs. I redrew the circuit for 4 outputs and had PCBs made. (if you want one conteact me!)  I now have the units in my M1DST 10MHz Thunderbolt monitoring project and in my LPRO101 10MHz Rubidium source. The project is written up at

Tuesday, January 30, 2018

BARTG 2018 RTTY Sprint

This is a fun contest. It starts and finishes at a reasonable hour (noon) and as a sprint only serial numbers are exchanged; no reports. The hardest part was that neither the confirmed dates, rules or the experts list were available on the BARTG web site or any hint where they were located before the contest

Radio conditions were poor. 15m only opened for 30 minutes on Sunday morning. 20m didnt have the usual quantity of far eastern DX. 40m was subdued. 80m was good overnight into the USA, the only failure was AD5XD in Texas, despite many attempts. The highlight was being called by YC4BGN on 40m Saturday night giving me the 6th continental multiplier (OC).

The dual vfo FSK configuration using a pair of TinyFSK worked very well using the method by K0SM , Although N1MM v1.0.7013 was supposed to support TinyFSK natively, when tried it showed highly corrupted text in the transmit window meaning it could not be used effectively to see what was being sent! Hence I resorted to the K0SM setup configuration

There were no equipment issues. I used my newly made accesory cable to replace the elecraft made one that caused trouble the previous weekend on the RSGB Data AFS which worked fine switching the KAT500

        Band     QSOs     Pts  DXC  Are  Con  
         3.5      90      90    4    0    0   
           7     224     224    9    0    1   
          14     256     256   39   19    5   
          21       7       7    0    0    0   
       Total     577     577   52   19    6   

  SOAB100W section Score : 245,802

Tuesday, January 23, 2018

RSGB Data AFS 2018

The original plan was to operate with G4BVY from GW0FRE. However he was detained elsewhere so I would have to do it single operator, I decided to use MW2I

As it is a dual band (80/40m) dual mode contest (RTTY/PSK63) I could not just use MMTTY. At his talk on data modes at the Malvern club G4BVY suggested using MMVARI, which I hade never used before. Using it on AFSK you could have one window for RTTY QSOs and one for PSK31 QSOs. With Rogers remote guidance (including a Skype call 10 minutes before the contest!) I managed to get it going

Originally I had intended to use the KPA500/KAT500 at 400/100W output. However during pre-contest testing there were many issues with the switching. Most often with the correct antenna and band selected on recieve, when i went to transmit the amp would change band (sometimes with "Invald" on the KPA500 display) the atu would switch antenna and try to tune it and the KPA500 would fault out.  With time running out a decision had to be made, so i used the K3s barefoot at 100w with its internal ATU and the 2 antenna ports switching between bands

Conditions were poor on 40m, just 6 RTTY (no PSK) qsos into central europe. 80m had a reasonable rate
              PSK        RTTY      Total
80m       52           90           142
40m       0             6              6

Grand Total 148 QSOs

After the contest I investigated the issue further. It was narrowed down to the 15pin to 15pin aux cables supplied by elecraft with the KAT500 and KPA500. One worked fine but the other appeared to have an intermittent short between the band1 pin and the ptt (hence why it changed band when going to transmit).  During the following week I cut apart the molding on the faulty cable and saw how unreliably it was assembled. Although their was a clamp that held the screen, which was doing a reasonable job on the screen, it did absolutely nothing to stop the cables in the bundle moving and rotating. This had happened and the band data lead was wandering around the plug, touching the PTT pin.

I looked at the cost of a replacement cable, but at nearly 50 pounds and the photos not assuring me the cable grip method was any better I decided to make my own

A search of the Farnell website revealed a 15 pin HD metal shroud that had a selection of cable clamps that would grip any cable firmly. They were not cheap (6.52) but I needed reliability.

As the Elecraft aux cable used only 10 cores I found some 10 core+screen cable and made a pair of 1 metre long 15 pin male to female cables; enough for the KAT500 and KPA500. I also made a shorter cable that could be used to connect the KAT500 to the KPA500 when the ATU is sitting on top of the PA,

 I also found my 3 metre 15pin to 15pin all pins connected cable (with moulded plugs), As it had 2 female connectors, i chopped it in half and with two of my newly purchased connectors made a pair of 1.5m male to female leads. These cables are useful when connecting to my K3 switching box which has a possible need for all pins

Monday, December 11, 2017

Making the K3 internal Transverter more External Transverter proof

Having suffered with the K144XV internal transverter's lack of useful output adjustment range, I finally decided to do something about it. The issue is that with the power control fully clockwise the 144 MHz output power is 9W. With the power control fully anticlockwise the output is 1W. This is the only band you cannot turn the output down to 0W!.  If you set the the IF level to -10dbm, fully anticlockwise is still 1W, as is every other setting of the knob.

The issue was raised with Elecraft over 3 years ago, but they said there was no software solution. They did point out that there is a drive pot in the module that could be adjusted to make the maximum level suit my transverter. After blowing up the pin diodes in my DB6NT transverters on more than one occasion, it was time to investigate.

Reference to the circuit of the K144XV revealed the pot was labelled R87

After removing the K3 top cover and the Transverter top cover, R87 was physically located between L3 and L4. It is shown in the following picture:-

Next a small hole was drilled to allow a trimming tool to adjust VR4 with the lid still on the transverter, as shown below:-

I set VR4 to give 1.2W with the drive level set in the menus to 0dBm. The adjustment range is similar, but now there is no risk of overdriving and destroying the transverter.

Another advantage of the new configuration is that the positive  voltage on transmit present on the XV connector centre pin is retained for transverter switching. Previously with an external attenuator the DC component was dissipated and an external Bias-T was needed to switch the Transverter.

Wednesday, October 11, 2017

1296MHz Trophy 2017

Having been to Dorstone two weeks previously for the UKAC with poor results to the North, I wondered whether it was conditions or if there was not just enough time to set up skeds on ON4KST. to work them.  Six hours of operation in the 1296MHz should provide an answer, especially as for the first time i could use the SCC M2I.

As there are no power classes in this contest the full 350W from the 4 x MRF286 amplifier could be deployed (as opposed to the 2 x mrf9060 in the UKAC) to the 44 ele Wimo. 48QSOS were made  with the best DX being DK2MN at 684km Some other noteable dx was PI4GN, PA0S, OT5A/P GD8EXI, GU6EFB and GI6ATZ. The only failure was with G4ALY who by the time i found him on CW my keying paddle springs had fallen apart. The only escapee on ON4KST was G8PNN, who admitted at the RSGB convention had been replying to M21 not M2I 

The conclusion of the operation was that with the extra time some of the weaker northern stations were workable, the site was alright

Things got so quiet towards the end i spent the last hour trying to receive the GB3ZZ DATV repeater. The 46km proved not possible (and having plotted the path on my return home I can see why!)

I also took along the 13cm system with the KX3 which although it could receive beacons produced no power, which turned out to be the KX3 not being able to produce sufficient voltage (~3.5V) on the antenna connector to switch the transverter to transmit.

Saturday, September 30, 2017

RSGB National Hamfest 2017

This years visit was made on Friday as usual. There was heavy rain as the outside area opened, so much so that the inside hall was opened early. A used Tonna 50MHz five element  yagi for £20 was purchased from the flea market with the intent of converting it to a lightweight 4m Yagi. Indoors a four section 20' swaged mast was finally bought (I thought about getting one last year!) from Moonraker

The usual big traders were in attendance, although some on a smaller scale than last year, for example Waters and Stanton. It was impossible to get near the QRPLABS stand as G0UPL had to queue of people placing orders. I have still to finally meet him after having previously had many transactions with him from Texas

The highlight of the trip was non transactional! A few months ago I assembled the BATC minituone receiver, but it failed to receive the DATV signal generated by the RPI, even though it passed self test so I put it aside. The BATC would be at Newark and I guessed would have real DATV signals, so I took the receiver along. Noel G8GTZ was only too pleased to try it out and it passed testing with flying colours. Now I can move onto assembling my Portsdown Transmitter modules