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| Radio Direction Finding |
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| PA3BNX:
Hello Every Body, I did some sketch for a Super Simple Sound Doppler with negative voltage for the diodes if you use ordinairy 1n4148 diodes as Pin Switches. I am trying to build en draw a new PCB in DipTrace to right now. I did some changes in the outputcircuit to try to softswitch it. So take a look and give comments. |
| PA3BNX:
Hello Every Body, Yesterday I did a radio Veron club demonstration with the Doppler's. Today I did rebuild the 4 x 1/2 wave Doppler antenna at home and it didn't work okay anymore. It took me quite some time to find out what was wrong. But the RVS BNC Chassis had no good contact for RF to the aluminium. But still the DC contact was good enough to measure voltage drop over the 1n4148 diodes. It was strange what happend. I did wire the mass to the solder lug so the RF contact is again okay. It has to do with corrosion or bad contact from RVS to aluminum. Further I did reduce the 4x 100nF C's at the lowpass at the 4001 NOR outputs to 1nF on the SuperSimpleSoundDoppler circuit. The not connected output looks much better on the scoop hi... The bare 4001 nor outputs are not very happy with just 470 ohm and 100nF as load only. The Doppler works equally good. |
| steve_w:
keep up the good work, I read your posts with interest. regards SW |
| PA3BNX:
Hello Every Body, Today I did work on my 4 magnetic feet for the car with 1/4 wave monopoles for 2 metres. They have about 8 cm diameter feet with rubber beneath them. About 100pf capacity between earth and coax mass. So I decided to put aluminium foil underneath them and wrap that with a tire wrap around the base clamp. No or less wrinkles and now I have more then 700pf So that's a lot better for mobile using. So try that to if you want to use 4 monopoles on the car. Remember that good mass or RF earth is needed for good bearings with a Doppler. |
| PA3BNX:
Hello Everybody, Today I did draw a even more simple SuperSimpleSoundDoppler circuit with a 4017 I have not build it yet but I think it can run as well... It would be easy to make a 3 4 5 or even 8 antenna SuperSimpleSoundCard design now. Just put the reset line further away and add some more antenna's hi.. Don't forget to change the oscillator frequency accordingly. I did put to diodes to have a symmetrical block wave to the lowpass filter for the reference signal with the 4 antenna circuit. I added a resistor from base to mass at the referency frequency circuit of 100k Today 6-6-2012 I changed the buffer reference transistor to a collector tapped one so the output is constant if I Remove or Connect the antenna switcher unit control cable I got it all working on matrix PCB now. Time to draw a new PCB layer for boards hi. |
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