November 1971 såg vi ett enormt gyllene UFO,klockan 20.04 till 20.13 Tidsmaskin uppenbarade sig vid Nötesundsbron,Vindön,Sundsandvik,Orust,Bohuslän,Sverige 440 meter i diameter,svävande tyst och blickstilla 50 meter ovanför havsytan toppen syntes ovanför Vindön som är 87 meter över havet.Farkosten for 20.13 blixtsnabbt österut,helt ljudlöst,5 till 6 ljusblixtar,sedan ett LASER rubinrött 200 meter stort virvlande gnistrande lysande moln....en mörkblå NATO stjärna långt bort ovanför Uddevalla,Bohuslän,Sverige. Det vart en Lördagskväll i November 1971 och UFOt hördes på Bert Kjelldahls Bilstereo,men inte i hoovrande,eller när den ljudlöst for iväg.
November 1971 såg vi ett enormt gyllene UFO,klockan 20.04 till 20.13 Tidsmaskin uppenbarade sig vid Nötesundsbron,Vindön,Sundsandvik,Orust,Bohuslän,Sverige 440 meter i diameter,svävande tyst och blickstilla 50 meter ovanför havsytan toppen syntes ovanför Vindön som är 87 meter över havet.Farkosten for 20.13 blixtsnabbt österut,helt ljudlöst,5 till 6 ljusblixtar,sedan ett LASER rubinrött 200 meter stort virvlande gnistrande lysande moln....en mörkblå NATO stjärna långt bort ovanför Uddevalla,Bohuslän,Sverige. Det vart en Lördagskväll i November 1971 och UFOt hördes på Bert Kjelldahls Bilstereo,men inte i hoovrande,eller när den ljudlöst for iväg.😮
I dont understand the need for such a high IF? At BC freqs, with a standard 455kc IF filter, images are easily 50dB down, and using a tuned RF stage, even more. The tracking issue is going to be very much worse, the Rf stages tune a ratio of 3:1, the Osc range is miniscule in comparison, making single knob tuning with reasonable tracking very unlikely. Stability in the VFO will also be an issue given the ripple in these cheap filters giving annoying phase distortion audio artifacts throughout the passband as the freq drifts... There too is the possibility of powerful signals in the 25 meter band mixing with your Osc, giving spurs in the AM band despite the balanced mixer, and front end filtering.. The mechanics of superhet AM radios is well developed over almost a century, they work well the way they are.. I am not seeing the logic in this.
One of the advantages of high IF frequencies is the opportunity to dispense with tuned RF stages and remove the tracking problem completely, you can implement a simple lowpass filter at a frequency just above the RF range you are covering and all imaging is filtered, probably 60dB or more.
As I understand it Charlie is using junk box parts. He simply wanted to use that gorgeous variable capacitor. I have the same 9Mhz crystal filter and I wanted to use this as a spring board to a general coverage receiver. It's all good fun.
Exactly. None of these videos are 'this is how you do it.' It's purely me just having fun using what I have at hand. Hopefully, it will encourage others to give homebrew a go.
My FTDX10 has an IF of 9MHz and works perfectly tuning to the AM broadcast band. The reason for the low IF in the early days is because it was much easier to create LC filters with the required bandwidth. The other reasons for not using a low IF have already been proven false. I'm sure this will work fine and I'm excited to follow along. Cheers, Ian
