Monday, 30 September 2013

And so to 70cm

With all the emphasis I have been putting on 4m recently I began to think that I ought to do something about the higher bands, especially with the IARU 432MHz and up contest this coming weekend. 432MHz is essential for this contest. I will probably also have 23cm available.

Late this afternoon I took down my 9 element 2m yagi and put my 21 element 70cm yagi back up in its place, at the very top of the mast.

It is many years since I had a masthead preamp on 70cm, so this was a definite requirement, especially with the long coax feed I now use.

Last week I discovered one of my 'reject' 23cm preamps. This one had failed to respond to my efforts to stabilise it. So I changed it to a VLNA70 and installed it in one of my interchangeable masthead preamp cases. I should add that having changed it to 70cm it was completely stable!!!! It was probably a faulty component that I had completely failed to find.

With the 21element Wimo on the mast I was delighted to hear and positively identify not only PI7CIS (JO22) but also HB9F (JN36) and F5ZHG (JO10)

At the moment I am unable to transmit, but I plan to implement the simple interface between my remote ( indoor shack) and main (outdoor shack) to enable PTT over the long control cable between the two. Maybe tomorrow.

73 de Sam

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I went to Newark on Friday.
A very enjoyable day out. I had volunteered to spend some of the day on the RSGB PSC stand although I was also able to spend a little time with Roger Banks on The DX Shop stand. There seemed to be a lot of interest in his new Gemini 4 70MHz PA and Roger was kept busy answering questions about the new 300W solid state power amplifier. Roger had a few of my built VLNA low noise preamps for sale on the stand, hence my interest.
Back on the PSC stand there was a steady flow of visitors. The PSC stand was in the block of stands allocated to the RSGB and was just across the way from the main RSGB stand. This obviously had its benefits as we were able to direct some of our visitors across to the main stand in order to re-new subscriptions, buy books or just meet members of the RSGB board.
Steve, G0KYA, is the Chairman of PSC. He had set up the PSC stand the previous day and it featured a number of photos, diagrams and a laptop running a slide show. Of particular interest was the plot of sun activity through this cycle. Steve didn't think we had reached the peak of this cycle just yet as the sun's magnetic field didn't seem to have flipped.
My only purchase of the day was a Cross Country Wireless SDR4+
This was purchased as a lowish cost way to produce a panoramic display on my TS2000. As the SDR4 frequency coverage has been increased to 4m it is now also capable of covering the first IF of the TS2000.
I struggled through Saturday to get it to work on my W7PRo desktop, but without success. I couldn't get the Si570 tuning to work.
On Sunday I tried again, but the installation was now onto my W7pro laptop. This time I was successful, but then I found the SDR-Radio software wouldn't apparently work at 70MHz!
I've put the SDR on one side for now and turned my attention back to preparations for the RSGB Convention in 12 days time.
I'm expecting a batch of PCBs this week. When I have these I will build one up to produce a 4m transverter to prove the PCB and to give me another version of the Nacton to photograph for the Convention!
73 de Sam
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Location:Falkenham Road,Kirton,United Kingdom

Thursday, 26 September 2013


Off to the Newark Hamfest tomorrow. I will be spending some time on the RSGB PSC stand as well as a bit of time on The DX Shop stand.

I will be looking for another SDR to use as a panadapter with my TS2000.
More on what I find, if anything, when I get back.

I hope to see many microwavers at the 12o'clock get together near The DX Shop stand.

Not looking forward to the early start tomorrow, though!

73 de Sam

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Sunday, 22 September 2013

4m again

I operated for an hour or so in the PW 4m contest this afternoon. I was rather surprised when several stations said 'thanks for the new multiplier!'
Was I the only JO02 station on 4m today? Apparently not. There was at least one more station on from somewhere north of me. I didn't hear them.

I used my original Nacton 4m transverter with the K3 and the external SSPA at about 100W output to my 5 element dual band 6/4m YU7EF yagi.
The only propagation I observed was tropo, so ranges weren't so great and there was lots of the usual slow QSB. My best DX was probably Tony, GW8ASD, who I usually work on the microwave bands and who is usually many dB stronger on 23cm than he was on 4m today,
As always, I found the waterfall and spectrum display on my P3 to be invaluable for spotting activity and knowing where to tune without the hassle of having to tune up and down the band.
73 de Sam
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Saturday, 21 September 2013

Web page update

This morning I updated my main web page to reflect some changes to the status of my preamp kits.

I took the opportunity to update the VLNA PDF to include some important changes to the VLNA70 as well as including the changes required to the VLNA23 to cover 1420MHz (VLNA21).
I have also ordered a small batch of PCBs for the new 'Nacton' 4m transverter. I will be talking about the Nacton at the forthcoming RSGB convention.
For anyone coming to the Newark Fleamarket next weekend, I will be on The DX Shop stand part of the time and the RSGB PSC stand part of the time. I'm not sure I'm going to get to look around the flea market!
I plan to have the early prototype of the Nacton with me at Newark. I may also have another prototype of the final PCB with me. If you want to ask me about the Nacton please do so.
73 de Sam
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Sunday, 15 September 2013

More 4m

DUBUS turned up two days ago. Interesting that it contains a nice 4m transverter design by DF4UE. What is surprising is how similar some of it is to my Nacton design. Maybe I shouldn't be surprised at the similarities. Anyone starting out to design a transverter today would probably choose to use modern MMICs for the RF stages. Indeed DF4UE has chosen to use the same MMIC for the RF stage. Even the mixer(s) are the same as used in the Nacton, although I use just one whilst Johann uses two.

I have added more interface switching options since the original design. When interfacing the original transverter module to the PA, external linear etc it became obvious that it needed a few more options. I'll talk about this at the Convention.

As I mentioned in my last blog I have spent a lot of time during the week drawing the schematic circuit diagram using my PCB CAD package and then modifying the PCB mask to correspond. Or maybe it was the schematic modified to agree with the PCB?........
Anyway, both are now ready to be used in my Convention talk next month.

I've etched another couple of PCBs, using the latest mask, drilled them and am now ready to assemble another transverter using some alternative and easier to obtain parts to those in the early transverters. In particular I have had to order a set of tuneable coils from Coilcraft. Coilcraft are usually happy to supply free samples as long as you are not too greedy. The chosen tuneable inductors are similar to the now-obsolete TOKO parts used in the original design. I am keen to check that these ones do fit the hole pattern in the PCB and have an adequate adjustment range to cover the required 4m frequency range. I've been informed that the samples have been dispatched and hopefully will arrive this week.
Dave, G4HUP, is currently stocking what appear to be suitable 42MHz third overtone crystals in HC49U package, so I will be obtaining one of those tomorrow in order to try it in the oscillator stage. The transverter has facilities for an external LO input where the requirement for greater stability warrants it.

If all goes well I plan on getting a small batch of PCBs made in the next few weeks.
I might have these back from production before my talk in mid October.

The other thing I have been doing is working out how to assemble my 3cm band EME RF feed unit. After weighing the successful 6cm EME unit I have found that the 3cm power amplifier, waveguide switch, and adapter weighs in some 1kg less, leaving just enough margin to add the mounting plate, transverter and feed without exceeding the target weight of 4kg I have arbitrarily set.
As my TVRO dish has a quadrapod feed support, meant to support a lightweight Chaparal horn and LNB, it has limited ability to support a heavy RF head. It will probably need further supports to prevent sag when the dish is elevated.
As we approach the autumn equinox the sun is getting lower in the sky so that sun noise testing time is reducing rapidly.
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Monday, 9 September 2013


I have been busy updating the documentation for my Nacton 4m transverter design, ready for my talk at the RSGB Convention, next month.
So far the design documentation has only existed as a series of notes in my shack notebook and in my head!
The need to ensure I have a comprehensive circuit schematic and PCB design ready for my talk means I have been having to critically examine all parts of the original and has already resulted in a number of small changes. Consequently I now need to produce another set of transverter hardware to check out these changes.
The good thing in doing this is that, because there is a good deal of commonality between the 70MHz Nacton and 144MHz Kirton transverters, I should be able to document the Kirton much more rapidly.......
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