Downloading the Marchwood Power Supply link has now been FIXED at the bottom of the page
My name is Dave and live in the Lake District, a little market town Cleator-Moor in west Cumbria, the little village I live in is Wath-Brow
The Homebrew rig covers 80, 20, 40, meters
100 watts output into Auto Atu. I built the Pic-A-Tune designed by G3XJP which was published in a series of articles in Radcom, it turned out to be quite a long winded project which took me 2 years to build but well worth while the effort.
The Digital display that you can see lit up is the G3XJP DDS absolutely brilliant, and that also was featured in Radcom as well which injects +7Dbm into the SBL1 mixer which is just right to turn the diodes fully on in the mixer. I have since built a HMode mixer using Baluns and they are very high performance mixer indeed.
The transceiver I built was from G4CLF’s circuit diagrams
And introduced many other circuits from other magazines to eventually end up with a full blown working transceiver, a labour of love I suppose but I still get a thrill every time I use it.
Below pictures Homebrew Pic-A-Tune designed by G3XJP. I used Mylar sheet for the capacitors which should handle a good 200 watts. I have no problems at up to 150 watts, no flash overs.
The aerial I now use is a Inverted V Doublet 180 foot long, a truly very low noise aerial having used it now for about 3 months, mainly on WSPR to prove its performance. For the past 10 years been using a Delta Loop 210 feet total of wire but the performance was not in the same league as my friends Doublet so decided to put the doublet up and on my website blog have added G3PKW Andy Choraffa a friend of mine for 40 years kept trying to persuade me into errecting one and the results are on this website for everyone to see, excellent performing aerial.
Over the last 45 years plus I have enjoyed making all of my station, the power supply that I use is the Practical Wireless Marchwood design and in actual fact built up 3 of them as they are so reliable 13.8 Volts @ 30 to 40 Amps depending upon the transformer. The Microhone is a cheap homemade electret type but found them to produce very good audio quality if engineered correctly. There is plenty of information out there on the Internet.
This Grid Dip Oscillator design I found on the Internet designed by Al Bloom N1AL. I decided to add it to this site to make it a little easier to find,, I built one up and it works very well indeed, it also dips as it should right down to zero without any hesitation. The only problem that I found was the voltage suggested in the article was 1.5Volts,, this just is not enough so I wrote an email to Al Bloom and he also said that other people had found the same as me,, it requires 3Volts,, 3 x 1.5Volt cells. Just click on the morden_gdo to view the Adobe PDF file and then save it to your computer to print out as required. If you click on the link below it explaines quite well what you can indeed do with the GDO.
73s G4RVH
I have just started working on the modern gdo, but when initially looking at the circuit, I was dubious about the low power supply of 3 volts used for the MPF102’s, as per the PDF printout. My suspicions were later confirmed during experimentation when it was found that the oscillator would not fire up at any voltage below 6 volts. I emailed N1AL last week but have not had a reply. From what I have seen on the web, I am not the only one who has had problems with this circuit. I was initially attracted to the design, because of it using a 2 connection coil with a BNC connector + a single gang variable capacitor. This circuit goes back a long time I know, but would very much like to know how you achieved the desired. results you mentioned on your page. You also mentioned about it requiring 3 volts but then you say 3×1.5v cells which is 4.5v.
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Yours sincerely + 73,
Colin Roper G4FPB
Hello Colin, nice to know that you have also built up a GDO, not a mistake on my part because I used use 3 x 1.5 volt cells, duracell and I have just taken the lid off mine to make sure for you as I had problems with 3 volts so with the 3 cell producing 4.5 volts and no further problems at all.
I have been testing out a WSPR-Lite transmitting Beacon putting out 200 milli-watts only and had it switched onto to my Delta Loop for 6 days now and worked 8,000 spots of which 103 of them reaching the States and Argentina 11,000 Km away but its directional because I fed it on the bottom leg, but I will write it all up on my blog for others to benefit from my findings as I have been at this Delta Loop business for 4 years now and done a lot of research on it.
Let me know how you get on. 73s Dave G4RVH
Hi Dave. Thanks for the quick response to my inquiry + the info about the battery voltage you used on the GDO. I will continue with the experiments. Very interesting about the delta loop and the excellent results you have been achieving, particularly with only 200mW.
Cheers + 73. Colin G4FPB.
Hi David, do you have any further info on using mylar sheet for you picatune build, was it used instead of tesco freezer bags and silicone grease?
73 Ian
Hello Ian, yes that is quite correct, I used mylar very thin sheet, I did try PTFE
but it gave me strange capacitance, but as soon as I used Mylar sheet everything
went according to plan. And yes it was to replace the freezer bags and silicone
grease, as I personally did not like the idea at all. Its quite a long winded
project. If you look up my call sign in QRZ.com there are more pictures there.
Its a big project so give yourself plenty of time, but it works very well indeed.
73s Dave
Hi Dave,
Thanks for reply.
I have got more or less as far as the capacitor stage but started not long after the project was first published..
Do you have a source for the sheets?
Thanks again.
73 Ian
Hi Ian,
http://www.ebay.co.uk/itm/MYLAR-STENCIL-Blank-Film-Sheets-FOOD-LASER-SAFE-A3-Various-quantities-125-micron-/251302939857?var=&hash=item3a82d28cd1:m:mJ7PaH4pni6HRMqMswaIN3w
That is a long time for a project. Above is a link for the Mylar Sheets
73s Dave
Hi Ian ,
I built a switch box to make the testing of the capacitors much easier to test so that you could switch the sections into play to make sure that you have the correct capacitance at the correct capacitor. 73s Dave