Monday, May 25, 2015

Phase Locking the G8ACE MKII Ovened Oscillator

I decided I needed to build a new 1296MHz Transverter that would be a single unit and have enough output to drive my 350W amplifier. I had a spare G4DDK2004 Transverter module but this requires drive at 96MHz for the local Oscillator. I could have built another DFS96 but that would occupy a lot of real estate. Similarily an RDDS is too large.  In my parts collection I found some G8ACE mkII oscillators, in boxes with the PLL lock boards. One was already on 106.5MHz for my EME 10368/144 xverter so I could put another on 96MHz. I ordered a 96MHz crystal cut for 60C via G4HUP. Putting it in the unit and running the Calibration produced the following:-

The TP1 Volts was set to 6.0V for optimum performance

Thoughts then turned to the lock board. I had no idea which software the EPM3064-4 FPGA had, so I decided it was best to reload the chip.  Originally I had used a parallel port programmer running MAXIIplus+ software for programming the chip but I no longer had a parallel Port. Some time ago I bought a USBBlaster clone from China so this was found.  I downloaded and installed the QuartusII 13.0sp1 Programmer software from the Altera web site and attempted to load . Nothing useful happened. I discovered that unlike my PIC programmer the USBBlaster does not power the target, It has to have its own power. Once that was supplied the software told me it could see the correct chip and the ref_e1_64_4.pof file was succesfully loaded to the FPGA. 
After making the connections between the boards I connected a Voltmeter to the monitor point. After applying the 10MHz reference this Voltage slowly oscillated before finally settling down at a fixed Value with the Rubidium locked Frequency counter showing exactly 96MHz

Spurred on by this success I found I had a temperature calibrated 123.75MHz crystal in the third oscillator/lock board (for 24192/432MHz). I loaded the FPGA with mwref_ww2r_3064-4.pof , set conf=101 and it locked to 123.75MHz . All I need to do now is order a 123.25MHz crystal for 24048/144

Wednesday, May 13, 2015

432MHZ UKAC May 2015

Went on a nostalgia trip last night in my first ever attempt at a 432MHz UKAC. Arranged to use GW4NXO/P which I had not used for 30 years! The call raised a few eyebrows!

Used Elecraft K3+ DEMI Transverter + 100W solidstate amp. The USA MGF1302 EME MHP preamp was dusted off after it's success in winning the 432AFS contest.  A 21 ele Tonna was borrowed by G4BVY which came with a long length of feeder attached causing the MHP to be mounted at the base of the mast!

It was quite windy on the Blorenge but at least it did not rain. Conditions were good early in the event but tailed off towards the end. I was amazed at the number of stations worked in the Channel Islands.The Best DX was DG1KJG at 715km

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!

Thursday, April 30, 2015

1296MHz UKAC April 2015

Originally I had intended to do this contest from Wales. However having blown up the 60W amplifier and the transverter IF pin diodes again  (due to the minimum power of the K3 being 3W) early Tuesday morning I decided not to risk the trip which would involve getting the generator but rather try the equipment locally.
Having tried Ankerdine hill in the past and found it blocked to the North  it was time to try somewhere else. With Roger G4BVY we had previously found a tump in IO82UA which looked good on paper, time to take a look. My "small"  system would be used. This is a K3+ G4DDK2004 Xverter +G4DDK VLNA and Wimo 44 ele. It would also be fun to try assembling my 14' Portaple mast, which collapses to 3' and is an easy fit in the Honda Jazz for the 1st time. This would all work off 12V from the car  and give me 10W

23 stations were worked with a few stations in IO83/IO93 who I dont normally work from home and stations to my SouthEast (eg IOW) I never even hear from home. However there was a lack of stations to the east which I normally work from Home.

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.