Maybe Mori can get you an old Telefunken from DE next time he's there
Radio theory
- Thread starter JHZR2
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Bringing back memories of my electronics training in the air force. Schmitt triggers, pulse theory, magnetrons, bi-stable multivibrator, power factor, impedance etc. 38 years since I studied all that, seems like another life
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You guys are way out of my league ..but don't you get 4 frequencies out of the "beater box"? The sum and the difference and the two fundamentals??
Originally Posted By: sprintman
Bringing back memories of my electronics training in the air force. Schmitt triggers, pulse theory, magnetrons, bi-stable multivibrator, power factor, impedance etc. 38 years since I studied all that, seems like another life
Same here studying for the FCC 1st Class license with Radar Endorsement that I passed almost 30 years ago. Vacuum tubes such as pentodes, triodes, etc. I've forgotten all the theory behind it now.
Bringing back memories of my electronics training in the air force. Schmitt triggers, pulse theory, magnetrons, bi-stable multivibrator, power factor, impedance etc. 38 years since I studied all that, seems like another life
Same here studying for the FCC 1st Class license with Radar Endorsement that I passed almost 30 years ago. Vacuum tubes such as pentodes, triodes, etc. I've forgotten all the theory behind it now.
Originally Posted By: JHZR2
Im using a Sony ICF-SW7600GR, generally considered an excellent radio for its reception, from what Ive seen. Do you mean that this radio isnt all that good?
No, you just wanted an explanation for the spurious reception you are experiencing. Poor front end selectivity at longwave is pretty typical from my experience, even in very high priced receivers, and your image issue is probably just as much an artifact of your location as it is your receiver.
The receivers I have that can tune longwave are a Drake R-7A, a Drake SW-8 portable, a Collins 51S-1, and a Zenith Royal 1000 Trans Oceanic portable. Out of this bunch, the only one that has a real front end for longwave is the TO. I doubt the Drakes have any front end filtering below 500 khz, and the Collins probably only has one tuned circuit, if that. I have some transceivers that probably tune below 500 Khz, but I doubt they have any filtering below 500 khz, either. Here in the middle of the country, there is nothing to hear on longwave except aircraft NDB's, so I never tune around there.
Whether the Sony is a good receiver or not depends on what you want to do with it. For casual broadcast band and shortwave broadcast listening, it is probably very good.
Would I use it to chase CW DX on the low end of 20 or 40 meters where I need to pick one weak station out from underneath a sea of stronger stations on almost the exact same frequency? Probably not, it's just not made for that type of reception, and would not be a good receiver in that application.
Im using a Sony ICF-SW7600GR, generally considered an excellent radio for its reception, from what Ive seen. Do you mean that this radio isnt all that good?
No, you just wanted an explanation for the spurious reception you are experiencing. Poor front end selectivity at longwave is pretty typical from my experience, even in very high priced receivers, and your image issue is probably just as much an artifact of your location as it is your receiver.
The receivers I have that can tune longwave are a Drake R-7A, a Drake SW-8 portable, a Collins 51S-1, and a Zenith Royal 1000 Trans Oceanic portable. Out of this bunch, the only one that has a real front end for longwave is the TO. I doubt the Drakes have any front end filtering below 500 khz, and the Collins probably only has one tuned circuit, if that. I have some transceivers that probably tune below 500 Khz, but I doubt they have any filtering below 500 khz, either. Here in the middle of the country, there is nothing to hear on longwave except aircraft NDB's, so I never tune around there.
Whether the Sony is a good receiver or not depends on what you want to do with it. For casual broadcast band and shortwave broadcast listening, it is probably very good.
Would I use it to chase CW DX on the low end of 20 or 40 meters where I need to pick one weak station out from underneath a sea of stronger stations on almost the exact same frequency? Probably not, it's just not made for that type of reception, and would not be a good receiver in that application.
Originally Posted By: Gary Allan
You guys are way out of my league ..but don't you get 4 frequencies out of the "beater box"? The sum and the difference and the two fundamentals??
Depends on the mixer. In an unbalanced mixer, yes. Singly balanced mixers cancel one fundamental input from reaching the mixer output, and doubly balanced mixers will cancel both the LO input and signal input from reaching the output of the mixer.
Unfortunately, in any of these, it's never just the sum and difference that appear at the mixer output. What you actually get are the sum and difference of all the possible combinations of the sum and difference and all the possible combinations of those sums and differences, ad infinitun, plus all of their harmonics ..... There's an equation to calculate this, but I don't recall it off the top of my head. How the mixer(s) and its termination handles this plethora of mixer products has a profound effect on the overall quality of the receiver.
I like building receivers.
You guys are way out of my league ..but don't you get 4 frequencies out of the "beater box"? The sum and the difference and the two fundamentals??
Depends on the mixer. In an unbalanced mixer, yes. Singly balanced mixers cancel one fundamental input from reaching the mixer output, and doubly balanced mixers will cancel both the LO input and signal input from reaching the output of the mixer.
Unfortunately, in any of these, it's never just the sum and difference that appear at the mixer output. What you actually get are the sum and difference of all the possible combinations of the sum and difference and all the possible combinations of those sums and differences, ad infinitun, plus all of their harmonics ..... There's an equation to calculate this, but I don't recall it off the top of my head. How the mixer(s) and its termination handles this plethora of mixer products has a profound effect on the overall quality of the receiver.
I like building receivers.
I can't remember my father building a receiver but he did build all his transmitters. All tube-type.
I googled VE3TM (his old call-letters) and found a cool historical recount of the original Michigan net in the 20's and 30's,,, included VE3TM in Leamington.
I googled VE3TM (his old call-letters) and found a cool historical recount of the original Michigan net in the 20's and 30's,,, included VE3TM in Leamington.
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