Thursday, September 1, 2016

FAKE AD4351 in AD4351 Signal Generator?

Having got the signal generator from ebay seller ayanhu81 running it was time to measure Phase noise. I decided to start at the low frequency end, so 42MHz was chosen. The controller was set to this frequency and the lock light came on. However, looking on the spectrum analyser no signal was found. Winding out the span a signal was found at 2668MHz (42x64), very strange! Next 116MHz was tried. The controller was set to 116MHz and the lock light came on.  No signal was found at 116MHz but a signal was found at 3712MHz (116X32). I next tried 144,432, 1296 and 2320MHz and the output was produced on the expected frequency. Checking further the IC only worked correctly above 137MHz

As a check I used the AD435x software tool to tell me what the register values should be for 42 and 116MHz and modified the arduino software to load the hex values directly, but still got 2668 and 372MHz. Its not the code, its a problem with the chip

Looking ath the Analog Devices datasheet for the AD4351 it has a divide by 64 and divide by 32 circuit in the chip, which my IC apparently didnt have. I checked the markings on the chip and it said AD4351. I did notice from it's datasheet that the AD4350 does not have these dividers, behaving exactly as my AD4351 was doing currently. Obviously my board had an out of specification AD4351 or a mislabelled AD4350

At this point G4JNT made a post on the UK microwave reflector that he was experiencing exactly the same issue with exactly the same module from the same UK supplier

I have raised a "not as described" case with ebay against the seller. We will see what happens!

Moral: You get what you pay for!

Saturday, August 13, 2016

KR600RC Maintenance

A few weeks ago I uncovered the Rotator and the control box for my KR600RC Rotator. Connecting it together and powering it up resulted in a lot of whirring from the rotator and only clockwise movement. Removing the cover the reason for the whirring was obvious; the drive band had perished.  I searched the web for the a replacement there was no obvious source. However there was a hint from the VKL reflector that the rubber nitrile band was a #29. Web Research showed that in the UK this is called a BS029, which were available on EBAY costing  £5 for 10, so 10 were ordered

The reason for no counter clockwise was also investigated. The reason was because the NC contact on the clockwise switch, through which the counterclockwise switch gets its power, was open circuit. Note that the 2 switches are different; the clockwise is DPDT (6 pins) , the anticlockwise is DPST (4 pins). Researching a replacement switch, I found someone was selling refurbished ones in Australia, so it must be possible to take them apart!

The replacement bands arrived last week so it was time to start repairs. First the rubber feet were taken off. The cover was then removed and the front panel detached. The gear train then had to be dismantled, by removing the calibrated bezel screws to get to the screws holding the metal cover holding the gears in place!) to get the band in place. Note that the rubber band goes round 3 axles to maintain tension

Powering up the indicator then worked properly. The broken switch was then taken apart by releasing the 4 lugs. I noticed that the 2 contacts had slightly different profiles. The non contacting contact was then removed and bent into a shape matching the working contact. The switch was then reassembled and was now found to be performing properly. Job done!

My only concern is how robust the controller is for mountaintop operation; I can see building an all digital controller with LCD display coming up!

Saturday, August 6, 2016

ADF4351 signal generator

Although I have a portable signal generator using the SI570 that can get to 200MHz I needed something that goes a bit higher. Looking on ebay I found some modules that cover 35 MHz to 4400MHz using the ADF4531 for 20GBP so I ordered one (auction 172152204149 by ayanhu81)

It took 4 weeks to arrive. The next question was how to control the module. An internet search revealed a design by F1CJN here  using an Arduino UNO and LCD shield with buttons from, which I did not have. However I remembered in my collection I already had a similar LCD/Switch unit from adafruit This would need some code modification, time to remember how arduino's worked. It was not too hard as Adafruit provide the libraries and examples for this unit on their web site. The biggest issue was as my switch reading used SPI not the A/D converter of the original design it was much faster resulting in much keybouncing.  Some strategically placed delays stopped that issue.

I now have it working. Listening to the signal on 144MHz and 432MHz it sounds OK, if a little off frequency due to the cheap on board reference (6kHz low at 432.2MHz) but as the board has an external reference input that is not an issue. Next to take a look at the output spectrum, which is reputed not to be too good at lower frequency, then to put it in a box.


Monday, July 25, 2016

70MHz Trophy

Enthused about 4m from previous outings we decided to visit British (IO81KR) again. We were late starting by 30 minutes by eating cake and coffee before departing to the site!. There was mist/rain/drizzle for the whole contest. Again we used the K3S and the Anglian transverter to drive the I0JXX dualband amplifier. The antenna was the 5 ele Powabeam at 6m,

The only equipment issue was computer related. The K3S just has one USB connection to the computer (no audio leads). For the first 30 minutes on every speech peak the virtual serial port and the K3S soundcards would be removed from the computer and reappear on receive. After a while there was a warning that the device was disabled as it was unstable. Not having had this issue on previous 4m events I took a look at the USB lead. I had taken the first one from the bag; a thin black lead. Looking further I found a thicker lead with clear cover that showed a decent braid. Changing to that cable, the issue went away!
In a change to  normal, there were numerous stations QRV up north, in IO84 and 94. This activity allowed us to confirm that the site is good to the North, we dont normally work much up there as there is no activity! The loudest signal was from GM4ZUK/P in IO86. Although two stations were worked in GU, there was not even a hint of a GJ station or GD. Being called by GI4OPH in the last hour was a welcome surprise/ 98 QSOs were had with the best DX being PA4VHF in JO32 at 640km

Saturday, June 4, 2016

June 70MHz UKAC

After the success during the previous Sunday's 4m contest, thoughts turned to the 4m UKAC the following Tuesday evening. Blorenge is much more hospitable at this time of week and it was much easier to get to directly after work than British Mountain

This time we used Rogers Van to support the 5 ele Powabeam at 20' Again the K3S drove the Anglian transverter then the I0JXX amplifier module, all operated from the Honda Jazz.

There was some DX heard while setting up from EA and IC8, but it disappeared as the contest started. Conditions on tropo were poor, but we ploughed on, listening around between qsos. We found EA6SX who we worked at 1442km as the best DX. After this excitement the search for multipliers continued. No continental DX was worked. Northern English squares were well represented but despite calling a lot that way, there were no sign of GM stations. 109 QSOS were made in total

Nice Sunset

The results have been published very speedily... within 12 hours of the entry deadline, AND the writeup contained more details than "the next contest is on xx/xx/2016! Looks like only our station worked the Sporadic-E





Friday, June 3, 2016

70MHz Cumulative Contest

Having finally  finished integrating my I0JXX dual band 50/70MHz amplifier it needed trying out. The contest calendar showed a 2 hour 4m (2nd cumulative) contest so we decided to give it a try. Blorenge is no place to be on a Bank holiday Sunday so an alternative was needed. Roger suggested British Mountain which was a bit more remote. I had never been there so I went there via his house, so i could follow him. The route was challenging for both vehicles. As we neared the destination we noted a vertical antenna and a tent, which caused concern, Dropping by and introducing ourselves we found they were CBers so we should have no trouble to us on 70MHz. We moved 100m along the road and setup the station. The 5 element Powabeam was put on 25' of pole with guys. The rest of the station was the K3S (on its first outing) and my G4DDK Anglian Transverter. We also got to try the audio boxes I had made which allows the operator and logger to choose any combination of main and sub RX audio

When the antenna was connected the band was full of wideband signals. Sporadic-E was in progress, the band was occupied by FM broadcast stations from Eastern Europe. SQ8EP was worked before the contest, but during the contest, despite the broadcast SP-E signals there was no SP-E dx available, the best dx was PF7M. The Northern English squares were well represented but despite calling a lot that way there were no sign of GM stations. 71 QSOS were made in total.


A friend of a friend stumbled across a youtube video from visitors to the CB station wondering what was going on at the white van up the road from the cb station! The video is here   The marauding sheep timestamp the recording time

Saturday, April 2, 2016

The K3S must be working alright on 475kHz!

Having done the K3S upgrades for 475kHz see here it was time for DX.  I was duly rewarded with my First transatlantic WSPR decodes of the year using the K3S and the PA0RDT whip in the loft:-

Timestamp           Call MHz         SNR Drift Grid          Pwr  km
2016-04-01 23:52 G3XIZ     0.475785 -24 -1 IO92ub 0.5  137
2016-04-02 03:56 DK7FC     0.475682 -26 0 JN49ik 1  827
2016-04-02 04:42 WG2XJM  0.475761 -28 0 EN91wr 5  5732
2016-04-02 05:10 WG2XJM  0.475761 -29 0 EN91wr 5  5732

Not band with the takeoff in that direction!

Worcestershire Beacon