Wednesday, 30 September 2015

23cm EME revisited

After the best part of three years QRT on 23cm EME I thought that with the dish relocated to a more favourable position in the garden and yet another dead wych elm tree removed ( Ivy is still a good 'noise generator!)fom the garden boundary, i would have a listen during the September 2015 ARRL all mode EME contest.
In total, over the two days and also Monday evening, I decoded or heard ( on CW or SSB) more than 20 different stations, with the best being JA6AHB. Signal levels ranged from -5dBJT down to around -22dBJT.
I looked carefully for VK5FA who was running just 40W but even though I knew he was there when working other Europeans,  I could not get a JT65C decode from him. Maybe next time. Andy is located in Adelaide and as I am going there next month I thought it might be nice to work him or at least give him a signal report.
Today I started to terminate my 14m length of LDF5-50 transmit cable. The cable runs from the shack to the dish so that the amplifier can stay in the warm, dry, shack, as previously. Although the cable loss should be 0.8dB at 23cm, the measured loss on my network analyser stubbornly refused to go below 1.3dB. I suspect the extra loss is from the old connectors I am using. With 200W in the shack this means I will just about achieve 100W at the feedpoint wih the additional loss of the short patch lead around the rotator. That is a smaller transmit signal than I used to achieve with the dish closer to the shack using around 8m of 5-50.
If I am going to take this seriously I will have to think about moving the amplifier closer to the dish. Maybe even run 300W in the old Storno case as I had previously planned to do.
The VLNA preamp performance is quite adequate and gives a sun to cold sky ratio closer to what I would expect than I saw previously.

Sunday, 20 September 2015

Crawley Microwave Round Table

I went to the Crawley MRT today. I had missed the last few years because of other commitments.
It was a good as ever. Although one of the smaller events in the UK amateur calendar, it is both very friendly ( as I used to say in my RadCom column) and an opportunity to see some of the other microwave enthusiasts I don't see for months on end.

I especially enjoyed Roger, G8CUB's talk on 24GHz as I had just managed to relieve Simon, G3LQR, of his portable 24GHz transverter. This hadn't been used for many years and was just what I wanted to allow me to align the portable dishes for the higher bands. My own efforts at a portable 24GHz transverter, using Thales and Elcom modules had proved less than ideal and had been cannibalised for parts for my new 24GHz masthead home station transverter. 

I'll have more to say about 24GHz home station operation in a later blog.

In the meantime the portable system will be used with one of several dishes for path alignment when setting up higher bands.

Simon also kindly allowed me to talk away his old 47GHz transverter. This needs a bit of work to make it more user friendly, but it will prove to be the basis of a very effective portable 47GHz system. It is many years since I held the 48GHz UK distance record in conjunction with G4KNZ ( 39.8km!). My old NEC-based transverter is no more........

The longer term plan is to make a 134GHz transverter. I have a suitable Elcom synthesiser and Roger, G8CUB, is reprogramming it for me to produce the two (switchable) 11GHz LO drive frequencies required. I have a (suitable?) 34GHz tripler and the DB6NT 140GHz PCB. Roger has ageed to bond/solder the diode onto the board for me.
With 24GHz and 47GHz portable to help align dishes, the 134GHz may allow me to make my first steps onto this primary amateur band.

Sam


Thursday, 17 September 2015

Anglian transverters

I have started to take delivery of another batch of assembled Anglian 144MHz transverter boards. The first of these have already been dispatched to their new owners. I have a number ready to go out and another panel or two arriving later this week. Details on www.g4ddk.com

New deliveries of component reels have been arriving steadily for the last few weeks. I'm now looking forward to getting back to doing some actual radio operating!
Sam