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Archive for August, 2008

Grid Dip Oscillator

Modern_gdo

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 use is a Delta Loop with about 210 feet of total wire length and its fed on the bottom leg slightly to one side, a truly very low noise aerial having used it now for about 5 years.

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

What-you-can-do-with-a-dip-meter

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