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





Wednesday, 12 March 2014

Just a test

I thought I had lost my Blogpress access. I guess not!

Saturday, 8 March 2014

4m PA module






This is the first 4m PA module for the Nacton, built on the new PCB.
The photo shows the PA on a temporary heat spreader plate. It is difficult to photograph the PA once it is mounted inside the Hammond housing.

The documentation for the PA is nearly complete.

Sam




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Thursday, 6 March 2014

On closer inspection the gnawed cable probably happened a while ago and I missed it as it was right on the opening of the duct. The exposed copper inner has already started to go green, indicating it happened a while ago.

I've pulled that cable and cut out the gnawed section. It is surprisingly free of signs of water ingress more than a few cm either side of the damage.

I have decided to re-terminate a shorter section of this Ecoflex 10 cable and connect it to the spare FSJ4-50 still in the duct. The rodents seem less interested in that type of cable!

Tomorrow I hope to finish this last stage of the cable rationalisation and become QRV on 23cm again. I've also decided to use the 23cm coaxes for 13cm saw well. More in this in another blog.

The Anglian transverter PCBs have arrived, as have the PCBs for the small Mitsubishi modules for 4m and 2m. I now need to complete the documentation for these boards before making them available.

Sam



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Location:Cable problems

Wednesday, 5 March 2014

Rodents!

Since last night, when I unwrapped the cables where they emerge from the duct, a rodent has already gnawed it's way into one of my coax cables! More protection is obviously required. Is it the early spring bringing hungry rodents out in search of food?
Sam



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Less cables

The final tally is 6 cables pulled out of the duct. That is a lot less weight hanging on the mast!

Sam



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Tuesday, 4 March 2014

Cables

Whilst waiting for the transverter PCBs to arrive I thought I would have a break from building stuff and do some maintenance on my mast and cables.
I am trying to rationalise the antennas on my mast so that I have just the 6/4m dual band yagi, 2m/70cm dual band vertical, 23cm yagi, 13cm yagi and 3cm band dish.
Other bands can be added as and when required.
I initially counted 13 individual cables ( coax and wire) dangling from the mast. Once I started to untangle the cables from each other, cut tapes etc I found there were actually 16 cables in the bundle! This is a large and heavy weight to be suspended from a small Versatower mast.
So began the journey...........
Several cables have not been used for sometime and were pulled from the under-lawn duct to make way for some other cables. Others were far too long ( and hence lossy), so they were shortened.
I had thought that the pair of LMR400 cables intended to be used on 13cm, as previously, were likely to be in excellent condition. Not so. One was acceptable, the loss being within a dB or so of the expected value. The second one was very lossy for reasons that are not yet obvious. I have pulled this cable out and I am now going to replace it with a length of lower loss LMR600. This will be the 13cm transmit cable. The lossy cable certainly explains the lack of contacts on that band for some time!
The Ecoflex10 23cm receive coax also turned out to have a slightly higher loss than expected, but now I know that I can probably allow for that by increasing the gain of the masthead preamp.
I had been using a length of FSJ4/50 joined to an equal length of Ecoflx 15 as the old 9cm transmit feeder. As this measured spot on for loss, and I'm not using 9cm at present, this coax has been allocated to 23cm transmit.
Similarly, the RG213 coax connected to the 6/4m yagi was showing signs of aging with longitudinal cracks beginning to appear in the jacket. This feeder has also been pulled out and a length of Ecoflex 10, that was spare, turned over to use on this yagi.
Interestingly I discovered an unscreened Multicore cable that was not being used for anything, but which was coiled up in the masthead power feed and control box. Again this was pulled out. The screened 4 wire will provide all the control circuits I am likely to need for now.

I am beginning to think that the problem of increased loss with the EF10 and LMR400 is due to the duct being extremely wet this winter and these cables have suffered water damage by osmosis. I am going to have to rethink how I get my cables across from the outdoor shack to the mast. Maybe an open trench with removable cover might be a better solution.

I have at least one more day's work to do to reinstall all the cables and connect everything back up. Once that is done I should be back on 23 and 13cm with a better signal and able to hear signals again!

Sam




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