Friday, May 1, 2015

Martlesham Round Table 2015

The end of April is now the annual time for the Martlesham Round Table (rather than the previous November. I drove the 200 miles on Saturday morning and arrived just at the start time. I attended the DF9IC talk on 1296MHz Amps which was very interesting. I eventually found the relocated test equipment area and had my G4DDK 23cm, 13cm and 9cm preamps measured along with a 525MHz Coaxial LPF which does a wonderful job of removing the 3rd harmonic of the 500W 70cm amplifier. There was the usual dinner on the Saturday evening which was a very sociable affair. On the Sunday there were more talks during which time I did my presentation on "Remote control radio systems for free" available as a .pdf here. As usual there were some interesting items for sale from the traders. I got a length of LDF2 with connectors, FSJ4, 3 large Heatsinks, SMA adaptors and a bundle of IEC mains leads with UK plugs (to replace the ones with USA plugs I left in the USA).

Shawn the sheep, The Tea cosy a regular attendee at the meeting was not present on the Saturday but he was persuaded to visit on Sunday. He now has clones in New Jersey and Texas!


Wednesday, April 8, 2015

RSGB Propagation forecast alerts me to DX.

Tuesday night was the 2m UKAC contest and as the clocks had changed, (enabling setup in Daylight), it was time to go portable from Blorenge, IO81LS again. As the RSGB prop forecast said conditions should be good  to the east I also took along a small 24G system to see what beacons I could hear before starting setting up the 2m gear.  I took my normal 24048/432MHz transverter (retuned from 24192MHz it used in the USA) with an FT817 as the IF and a 20dB reference horn. Sure enough upon arrival there was a big Inversion layer visible to the east.   GB3CAM at 210km was quickly found and was a good decode. GB3ZME was also a reasonable signal at 105km LOS , but not on the direct heading of 020 degrees but on 070 degrees! No other beacons were heard (GB3SCK and GB3AMU were considered possibilities)

The 24048/432MHz Transverter


The UKAC on 2m sounded like an HF contest on 20m. 144QSOS in 27 locators with the best DX being DJ2TX in JO33 at 731km. Used 300W (due to the auxiliary equipment more power tripped the 1000W generator) to a 9 ele at 15' from Elecraft K3 with solidstate amplifier and HA8ET preamp for the first 2 hours Then there was a generator incident so a KX3 running 2W from its internal batteries (I hadnt seen the need for the KX3 DC power lead!) was used for the remainder of the contest but 10 stations out to 350km were still worked!








Thursday, April 2, 2015

Restoring my old FT726R

When we moved to the USA in the early 90's Roger GW5NF got the FT726R that was my primary VHF rig. It did make a trip to Gibraltar on the 1984 ZB2IQ expedition. Roger subsequently  used it with G4VXE off a car battery for Backpackers contests but had recently retired to the shack floor due to some issues. I decided it was time to rejuvenate it

First issue was that it did not work off the internal mains supply. Looking at the shorting plug on the back panel that had been used to supply 12V from the portable battery the link had not been removed, allowing 12V to be fed into the output of the internal PSU. Luckily Yaesu had foreseen this issue and fitted a fuse which had duly blown. The fuse  was replaced and the 12v wire removed from the plug and the radio lit up off its internal supply

50MHz and 432MHz receiver and transmitters worked fine but 144MHz was quiet on receive (no sign of GB3VHF) and only produced 3W on transmit. Occasionally blipping the ptt would increase the receive noise and the beacon would appear. An internet search revealed the radio is known for having a sticking relay in the 2m module which some had cured by burnishing the contacts whereas some had needed to replace the relay. Time to examine the module

Sure enough, in the quiet receive state no 9V was being supplied to the receiver chain by the relay. The relay, FBR221D012M  is no longer available  (note the available FBR221AD012M is very different). It was suggested that the contacts needed burnishing so the cover was taken off and the contacts burnished and adjusted. . This seemed to fix the problem for the time being. The transmit chain was also aligned as per the manual; a load of flux was found all over TC01 which was removed and adjusting TC01 and TC02 increased  the power to 18W which was reduced,  as per instructions to 10W maximum. The receiver was already tuned and could not be improved.  It was noted that the front end mod using a BF981 and the IF gain increase mod had previously been done, making it state of the art at the time

While the covers were off the 50MHz module was aligned. It had been noted as having a marked peak of 18W at 52.0MHz and 8W at 50.2MHz. Also the power control had limited range. 190degree setting was 0W 200degree was 4W and 210 degrees was 7W. The module was then aligned as per the manual the power output was now flat at 10W 50 to 52.5MHz but the power control was still compressed the best achievable was 190degree setting was 0W, 280degree was 5W and 10 degrees was 10W . 

The radio has been successfully restored and has now been re-integrated into Rogers shack to compliment his TS2000. It easily drives the 2m and 6m amps to full output.

Tuesday, March 31, 2015

Feature upgrades for the 432MHz Solidstate Amplifier

Having upgraded the 2m solidstate amplifier I decided I should do the same upgrade to the 432MHz Amplifier.  The original writeup is here The Two same features were needed:-

1. There is no bypass position, so one cannot test the antenna SWR before letting the amplifier use it. This cost of the lack of this feature was learnt the hard way on my 70MHz amplifier
2. Currently the Elecraft K3 keys the DEMI transverter which keys the amplifier which sequences the antenna relays and preamplifier. There is no output for the Amplifier to properly sequence the DEMI Transverter along with the antenna relays and preamplifier, this needs to be added.

A bypass switch was added to the front panel along with a bypass LED. A phono socket was added to the back panel for the Transverter output. An hour was spent adjusting the PIC code and all feature additions were accommodated.




Monday, March 30, 2015

Feature upgrades for the 144MHz Solidstate Amplifier

Having got the 2m Anglian up and running it was time to  interface it to the 400W solidstate Amplifier.  Two features were needed:-

1. There is no bypass position, so one cannot test the antenna SWR before letting the amplifier use it. This cost of the lack of this feature was learnt the hard way on my 70MHz amplifier
2. Currently the Elecraft K3 keys the amplifier which sequences the antenna relays and preamplifier. There is no output to properly sequence the Anglian Transverter along with the antenna relays and preamplifier.

A bypass switch was added to the front panel along with a bypass LED. A phono socket was added to the back panel for the Transverter output. An hour was spent adjusting the PIC code and all feature additions were accommodated. Also incorporated was the LCD showing the alarm trigger levels at amplifier startup


Thursday, March 19, 2015

Locking the 2m Anglian Transverter to an external reference

G4DDK had mentioned it was possible to Injection lock the 116MHz oscialltor of the Anglian Transverter by Injecting 116MHz into the LO port of the Transverter module. In my parts collection I found an early 116MHz DFS module, similar to the design used on 96MHz described at  at http://g4fre.com/dfs9096.pdf  except it used (10MHz * 11)+(3 * (10MHz/5)) and three 116MHz crystals. The output level was ideal at +3dBm While monitoring GB3VHF it was found to put the transverter onto the correct frequency as opposed to the free running frequency.

Having proved it worked, I then mounted the DFS116 inside the box. A slider switch (less likely to get damaged portable) was used to remove the 13V from the DFS when there is no external 10MHz applied. The output from the DFS did not need disconnecting from the transverter LO input when powered off.

Sunday, March 15, 2015

Using the Anglian 4m Transverter with ANAN-10 and N1MM logger+

This morning I decided using the K3 with the new Anglian 4m xverter for the 70MHz contest would be too easy, so I decided to try hooking it up to the ANAN-10 and trying to use it with the N1MM Logger+ software.

Its easier to use the TX port output with a 20db attenuator than the xverter port output. If you do use the XVERTER output, the TX port has to be terminated, as it still produces 0.5W output and Powersdr will complain of SWR alarms. As previously determined, a 30MHz LPF is always needed on the output.  I used the EOT output pin 25 of J16 to key the transverter. The Mic input had previously been wired for the KX3 PTT microphone

Powersdr makes the ANAN-10 look like a TS2000 to the N1MM software so N1MM could track the frequency through a com0com virtual serial connector.  I used a COM4<>COM5 pair.

Tuning Powersdr through the beacons was a challenge, so, having remembered I had a Griffin powermate USB knob I Installed that on the windows 7 64 bit machine (the driver/software on the griffin site for Vista worked fine). I configured it to tune the rig up and down. This worked fine BUT ONLY if Powersdr had focus. When N1MM had focus the tuning knob did very strange things to the frequency.  This was overcome by deleting the default setting entries in the Griffin setup software. I then discovered (after reading the N1MM documentation) it was possible to tune the radio (only in run mode) from the keyboard. This scheme worked well.

The transverter produced 7W into my loop antenna in the loft. A few QSOS were made on SSB with locals then my thoughts turned to CW. Initially I used the Powersdr CW keying facility as I failed setting up the N1MM keyer to send cw through the CAT connection. Unfortunately the paddle connections were swapped over so G4BRK got to suffer my cw with the paddle operated upside down ( you can swap the paddles over in Powersdr I later found out, but its in the <DSP><CW> tab!) I then worked G4BWP (my best dx) then G4RFR on CW.

After the contest I went back to looking at the N1MM keying. I discovered, (also in the <DSP><CW> tab) that, whilst leaving the primary cw connection as "radio", (ie its key jack) a secondary connection may be set as a com port (COM6 in my case) and the RTS and DTR set to convey the cw and PTT signals from N1MM. Another com0com virtual port pair was set up (COM6<>COM7). In N1MM in the <configurer><hardware> Tab,  COM6 was set up as a "CW/other" connection with RTS and DTR appropriately assigned. This then worked fine