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 contact me!)  I now have the units in my M1DST 10MHz Thunderbolt monitoring project and in both my LPRO101 10MHz Rubidium sources. The project is written up at http://g4fre.com/10MHz_distribution.htm

5760MHz UK Microwave contest August 2017

Having previously finished encapsulating my 6cm amplifier, I was eager to try for some QSOs. The UK microwave groups 5/10GHz activity contest on July 27, G4DDK had given me a 5Ghz patch antenna which would be easier to use than my 0.6m dish. I ended up packing the 5760 EME transverter, the amplifier , and the KX3. As it was a 12V system everything could be run from the car battery

As the local site at the tump at IO82UA had a good takeoff to many directions North through southwest, it made an ideal starting point; if anything didnt work I would be close to home to get it fixed

The first attempt was with GW3TKH/p operating from the Blorenge IO81LS. Signals were easily exchanged, but holding the antenna in one hand, writing the log entries and tuning the rig was quite tiring!Signals were also exchanged with GW4HQX/p at the same location

.

The path SW to GW3TKH/P

 The next attempt was with M0HNA/p in IO91GI. He had linearity issues so no SSB, so we tried NBFM. No problems in exchanging signals, and the best DX at 94km. I next tried with G4ODA. Signals could be seen on spectran in both directions, but not loud enough for a QSO.

The Path  SE to M0HNA/p

I wanted to try with G3XDY and G4JNT, but both were too busy setting up skeds on ON4KST. Hanging around was not possible as I needed to move to the other side of the malverns to work G3ZME/p in IO82QL before the contest ended. I left the Tump and went searching for a suitable location. I found a couple of locations but it is amazing how big the field hedges are on the west of the Malverns which precluded their use. I ended up again going to Ankerdine Hill IO82TF, where despite pointing through dense foliage a qso with G3ZME/P was completed, again handholding the patch antenna.  By this time G4JNT was free, but the Malverns caused a major path obstruction.

A very interesting trip out and some interesting points learnt for future operations

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 Chinese supplier

I have raised a "not as described" case with ebay against the seller. He was forced to refund the cost of the module!

Moral: You get what you pay for!