Super-heterodyne receiver basics and some shortfalls of older radios

[@rrangana11]

I am aware of these effects but this is the first time I am experiencing all of it in one place. Good demo and explanations. Thanks a lot.

[@W1VLF]

Thank you for watching appreciate the comment! W1VLF

[@juliocesarpereira4325]

It was very instructive. I'll repeat your experience with my radios too. One of them happens to be a Sony ICF-2010 too. I like your videos because they address theory and practice. Thanks.

[@W1VLF]

Hello Julio.. I tried with my 2010 and it looks like there is no a lot of signal radiating from it... I will try it again W1VLF

[@razielpavon80]

as an anecdote, that LO leak, together with my RTL-SDR helped me to repair a very peculiar fault in my old RadioShack DX390 radio, in MW it worked very well but in SW it stopped tuning, the display showed everything correct even, but there was no tune; With the help of the SDR and the service diagram indicated that the 1st LO was around 54MHz, (it is a double conversion radio), so with the help of the SDR I was able to detect how the LO moved in MW, but in SW it stopped moving, finally the fault was in a DC-DC boost converter stage, which generates the tuning voltage of the VCO, (15vdc), I corrected the fault and my old radio came back to life hehe

[@W1VLF]

Raziel.. That is a great story. Troubleshooting one radio with another radio! The new helping the old!!! Thanks for posting that!!!! W1VLF

[@FireandFrostHVAC]

Excellent video, thank you!

[@W1VLF]

Thank you ! Appreciate your comment W1VLF

[@KevinMauldin-c1r]

I've actually used the local oscillator leakage from one shortwave radio on another to tune ssb signals to listen to amatuer radio on receivers that did not otherwise support ssb. You just have to make sure the 2 radios are far enough apart that the lo "carrier" does not overpower and wash out the ssb signal that you are wanting hear.

[@W1VLF]

Kevin!! That is a great story!! Thanks for sharing that.. Experimentation at its best W1VLF

[@kensejkora4424]

Hello again, Paul. Just another thought after watching this video a second time. Although there is nothing 'wrong' with any of the concepts you presented, you missed the opportunity to describe how the radio "extracts" the AUDIO frequencies between zero and ~6 kHz from the mixer stage. Essentially, that is what the IF filter does, in that it "strips away" the 455 kHz difference from the mixed local oscillator signal to yield the demodulated audio frequency that the detector circuit "sees" and then we can "hear". Speaking of detectors, you might want to throw in a discussion of the very simplistic direct-conversion circuit used in the old "crystal radios" that pre-dated our youth. Those very simple 4-component radios used a tank circuit comprised of a capacitor and inductor, one or both of which was variable to "tune" resonance at a desired frequency, followed by an AM detector, usually a gremanium diode, but in the earliest days a piece of galena (lead sulfide) crystal, and a set of high-impedance headphones. Although I preferred the venerable 1N34 germainium diode, I fondly remember many an evening "tickling" the surface of a galena crystal with a "cat whisker" made of phosphor bronze wire to try to find the "sweet spot" where the interface between the phosphor-bronze wire and lead sulfide galena crystal formed a crude, but effective diode to serve as a detector. Now I'm the one really showing my age! In many ways, what goes around comes around... the earliest 4-component crystal raidos used a direct-conversion approach, and now many of the modern SDR radios employ essentially the same direct-conversion approach, albeit with a lot more options for bandwidth adjustment and demodulators compared to the barn-door wide bandwidth and simple AM detector/demodulator of the old crystal radios. 73 -- Ken WBØOCV

[@cthoadmin7458]

Early example of a covert channel. Russian embassies during the cold war, monitored radio transmissions in their host countries. Host countries wanted to know, which frequencies were they monitoring. Sensitive receivers placed near embassies capable of picking up the oscillator emissions from russian receivers would allow them to find out. Might be an interesting experiment, a 455 KHz tuned loop, and a sensitive receiver like the SDRPlay, how far do the signals generated within a receiver travel?

[@W1VLF]

Hi Thanks for that story.. I think the problem now adays would be that all the noise from switching power supplies on 455 KHZ. But you are correct.. A loop tuned to 455 KHZ would drastically crease the distance. W1VLF

[@franzliszt3195]

I finnaly understand supre het.

[@W1VLF]

Thank you Franz I appreciate the comment. Glad it helped W1VLF

[@cthoadmin7458]

... for the real tin foil hat experience you could even try to wrap a receiver with an external antenna, in tin foil or copper tape to see how well it suppresses radiated rf...