Wednesday, 9 April 2014

2.3GHz

As a result of the future of 2.3 and 3.4GHz OFCOM document that appeared yesterday I thought it might be useful to see whether I needed to be concerned about interference levels to the MOD equipment at Boscombe Down. The other MOD sites are significantly further away from this QTH as not to be a problem at almost any time.
I have been running the numbers for potential interference levels at Boscombe Down on 2.3GHz  from this location. Using the G0MJW software and the simplified path model ( no terrain data) it would appear that my 100W at the feed point and 20dBi antenna ( possibly 22dBi) gives around 6dB margin over what would be required. These numbers are for a 10% exceed.
The overall loss is 205dB, dominated by tropo scatter with diffraction and refraction both being significantly higher.
The G3YGF plots in Vol 1 of the RSGB Microwave Handbook confirm these losses.
It looks like I can operate without being too concerned that I am causing interference to the MOD down in BD!

Sam

Tuesday, 8 April 2014

Anglian results

I have completed my initial testing of the new Anglian 144MHz transverter. 
I only found one minor error on the PCB, and that is easily remedied.
The receive converter performed better than I expected, probably as a result of it being housed in a screened tin plate box. Later this week the first (#1) unit will go off for independent testing. At the same time the boards are being readied for production. With luck and a following wind, the first transverter kits will be ready for sale at Martlesham, although quantities may be limited at this stage.
For sure, the new Anglian transverter will be worth waiting for !

Sam


Sunday, 6 April 2014

Back on 4m

I found a little time today to reconnect the 4m system. I was too late for this morning's 4m contest and anyway, Sunday mornings are not normally good for me as I have chores to do, like the Sunday morning shop run and usually a coffee with a couple of the local radio amateurs. All very pleasant and far better than just talking to them on the radio!
With the 4m transverter connected to the K3 and over the long coax to the outside shack to pick up the Larcan power amp and heavily filtered preamp ( necessary due to the long coax run) I was able to hear the RAL beacon but not the Tring beacon. The YU7EF dual band antenna seems to have survived the winter.
Sam


Tuesday, 1 April 2014

Dispensing solder paste

At long last I got round to firing up the air(brush) compressor and paste controller in order to use the controlled cartridge solder paste dispenser. Once I'd set everything up I was able to manually dispense spots of solder paste onto the victim PCB. Much easier on the thumb than using a manual syringe.
The components were then manually placed onto the paste spots and after checking everything was in the right place, the PCB was placed in the toaster oven and 'solder' pressed on the reflow soldering controller. 12minutes later and the board was perfectly soldered.
It doesn't make sense to reflow solder simple little boards unless there are lots of them or they use some awkward part like a QFN or DFN package.
The intention is that I will make VLNA and transverter boards available, ready assembled.

Dave, G4HUP, will be demonstrating reflow soldering at the up-coming Martlesham Microwave Round Table (MMRT) www.microwavers.org and follow the events link. 
There may even be a chance to have a go at reflow soldering for yourself!

Sam




Friday, 28 March 2014

An early look at the Anglian

Sneak preview before I show it at the monthly Codger's meeting tomorrow!

I have just completed assembling the first Anglian 144MHz transverter. The Anglian is a direct development of the Nacton transverter, but features a significantly better performance. A 70MHz version will also be available, replacing the Nacton transverter. And for those who prefer a 'real' 6m band radio instead of an HF rig with a 6m section bolted on, the Anglian could be what you are looking for!













Monday, 24 March 2014

Nacton PA

I have published the 7W 4m band PA paper to go with the Nacton 4m transverter on my web page. Www.g4ddk.com 
PCBs are now available from me together with suitable wire for the LPF and the various passive components. I don't sell the PA modules. These are available from GH Engineering in the UK

Sam


Monday, 17 March 2014

That duct again!



For the last few days my remote rotator control has been playing up. The symptoms were that the pot in the G1000DXC has failed. I thought this unlikely as the rotator is a only a few years old. Resistance tests with a multimeter were inconclusive. 
Having thought about the problem overnight I became more convinced than ever that the rotator. cable was faulty. 
This morning I pulled the cable from the duct and there, a metre or so into the duct, the cable was showing clear rodent damage......


Once the cable dried out and the wires were separated, I tested the rotator and all worked as it should.
The problem was what to do. I could have bought a replacement cable from W&S for a little over £50, but the chances are that the cable would probably be of the same 'delicious' grey PVC that the rodents like. Clearly after four such attacks something more drastic was required. The answer was to splice in a new long centre section where the cable goes through the duct. I already had a length of black 6 wire recovered from the previous G400 rotator system. That cable had been in the duct for at least 8 years with no damage or apparent attacks from rodents.
With the rotator cable reinstalled everything seems to work well and if I decide to abandon the remote rotator controlit will be say to tap into the rotator downlead and parallel off a cable to the house. The rotator control box can then be moved between the indoor shack and the outdoor shack as required!





Now that the antennas can be pointed where they are wanted it was time to sort out why I couldn't get any output power reading on the remote Bird 43.
I eventually found the problem. More in another blog.

Sam