Geoff's Challenge 2007

For 2007 Geoff came up with another truly excellent challenge, to build something to use in the field that would indicate using LEDs.  Geoff did not specify what was to be measured.  We were treated to 5 very different projects, all of which would be really useful in the field.  Judging took place at our May 2007 meeting, with the winner decided by popular voting. 

SWR Measuring Device

Alan G8FWF submitted an SWR Measuring Device (Picture on left).

 

This indicated forward and reflected power on two big red LEDs.

 

With a well matched antenna, then the forward power LED will be brightly lit, whilst the reflected power LED will be dimly lit or not even lit at all.

 

 

 

 

 

Cairo Test Box

Andrew 2E0XAM showed a Cairo Test Box (Picture of right). 

 

Cairo is the standard connection used by Raynet so that any microphone can be connected to any transceiver etc. 

 

The bright white LEDS indicate the presence of 12Volts on one pin, 8 Volts on the Microphone PTT line, and the state of the squelch on receive.

 

By using bright white LEDs, Andrew explained that it could also serve as a torch!

 

Sensitive Field Strength Indicator

Phil G3XBZ had built a sensitive field strength meter (Picture on left). 

 

Phil explained that it would work up to about 30MHz, limited only by the main transistor.

 

 

 

 

 

 

 

 

 

 

 

SWR and Power Indicator

Alan G4UWS found a design for a SWR and Power Indicator circuit from RadCom (Picture on Right). 

 

This was by far the most complex circuit of the evening.  Alan had gone to a lot of trouble to finish the project off, to make it look really good.

 

 

Battery Voltage Indicator

Dave G3ZPR brought along a number of batteries at various stages of discharge to demonstrate his battery condition indicator from a Gorge Dobbs design in Practical Wireless (Picture on Left).

 

The switch on the side enables selection of either a single LED illuminated, or a bar of LED’s to be displayed.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Judging

Each entry was briefly described by the builder.  Members then voted awarding each entry up to 10 points.

Results

The winner was the Power / SWR meter submitted by Alan Walkers G4UWS with 80 points. 

 

Alan G8FWF’s small SWR indicator was a close second with 76 points.  

 

Dave G3ZPR’s battery condition indicator was third with 65 points.  

 

The sensitive field strength meter submitted by Phil G3XBZ was forth with 61 points.

 

Andrew 2E0XAM’s excellent Cairo test box got 51 points.

 

Everyone agreed that each of the designs was really in the spirit of the challenge that Geoff had set us, and that they could all find a practical application in the field.  Without doubt it was a particularly difficult challenge to judge.

 

 

 

 

 

 

 

 

 

 

 

Don’t forget Geoff’s Challenge for 2008.