Thursday, 29 May 2014

144MHz PA details

I have just posted a PDF article on my web page (www.g4ddk.com) showing details of the 144MHz 8W PA that complements the Anglian 144MHz transverter.
More transverter kits should be available in June. I am waiting for delivery of more 116Mhz crystals.

Sam

Wednesday, 28 May 2014

Suffolk Show

I spent much of today at the Suffolk show on Trinity Park, Ipswich.
I was asked by Dave, G4HUP, if I was interested in joining the Leiston Amateur Radio Club in the BBC Radio Suffolk WW1 At Home corral to help run a Morse session for visiting children and their parents.
I was an honorary BBC Volunteer for the day!

I had the opportunity to check out the TV uplink van and ask questions about transmit powers (16W from a TWT capable of 400W output), which satellite they were using and something about the video coding in use. All very interesting.

Two Morse signalling stations were set up, a few metres apart, using just a pair of wires to connect them. The kids were invited to either send or receive short predetermined Morse messages (slogans) that were taken from WW1 posters.
There was a steady stream of participants from the time I arrived around 11am until we shut up for the night at 6pm.

I was surprised at the enthusiasm of some of the kids for the code. And some of the them were naturals when it came to sending. A short demonstration of timing used sending dashes and dots and they were almost timing-perfect.

During the day Dave was interviewed by a BBC Radio Suffolk presenter and Dave even persuaded him to have a go at sending code live on the radio. I bet that surprised a few listeners!
Dave also appeared briefingly on Look East TV this evening, supervising a few kids sending receiving code.

All together a very interesting day. And the rain held off all day. It sure didn't look like it was going to be dry first thing this morning.....

Sam


Wednesday, 14 May 2014

4m Es

Managed to work my first 4m ES this evening after my first tropo contact outside the UK this year.
EA7KB and EA7BPO were nice signals from IM76 square. I missed the ZB2, which would have been a new DXCC for me from this QTH although I worked ZB2BL on 4 back in the early 1980s from my QTH in Staffordshire. In fact Jimmy was my fourth QSO on the band. After that it was all downhill..........
All the effort to get the Nacton transverter and 150W PA back on line today ( and part of yesterday) were worthwhile.
Sam

Sunday, 11 May 2014

144MHz

With the success of the Angllian 144MHz transverter kit I have started to wonder if I should get back on 144MHz and try to work some DX?

One thing that was always missing from my earlier 2m systems was a low noise mast head preamplifier. Thinking about the amount of cable loss ahead of the indoor shack transceiver/transverter it is obvious that I need some low noise mast head gain to obtain adequate sensitivity.

One possibility is to cut out the RF stage and filters from a now-unused Nacton transverter PCB to give a  low noise matched, low noise, preamp with a well matched on-board 144MHz output band pass filter.

From independent tests on the Nacton transverter the SPF5043 low noise front end is capable of better than +3dBm IIP3 with adequate out of band signal suppression, gain of around 20dB and good stability. I would expect a noise figure below 0.8dB. That is more than adequate for 144Mhz terrestrial use even in this formal area.
Conveniently, the RF stage and filters can easily be cut out from the Nacton PCB.

O
I will report results ( if it works!).

Sam



Friday, 9 May 2014

Cable tests

Recently I was pleased to be given some N crimp connectors for my LMR400 cable. However, my every attempt to obtain a suitable crimping tool had met with a lack of success. I know they are advertised on EBay, but even this proved a non-starter. I have now found one at the right price through my Chinese connector supplier and the price is excellent. But it won't be here until next week at earliest.
Bernie, G4HJW, came to my rescue by loaning me his crimping tool.
I replaced one of the existing N connectors on a length of LMR400 I had removed from the mast duct last month. With the troublesome connectors replaced with what at first sight seem to be low cost N crimp connectors, my measurements of loss and return loss using my HP5753C network analyser are within a fraction of a dB of Time's figures for LMR400 at various frequencies between 50MHz and 2.4GHz. I feel more confident of putting that cable back into use now.

Sam


Friday, 2 May 2014

144MHz transverters

Several transverters have been built up using the new populated PCB. Performance has been confirmed, so we have confidence that the design does what it says on the 'tin'!
I will complete the documentation later today and it will be available on my web page g4ddk.com

The supply of boards will be limited for the next few weeks as we ramp up production and await more parts.  
Please be patient if you are waiting for an Anglian 144MHz transverter.

Sam