Best low EMF shortwave radio for a beginner?

[vk6zgo]

I am anything but a troll, Electrical hypersensitivity is real, EMF stands for Electrical magnetic fields, and...thanks to some replies given, I will take the advice and go old school for a manual receiver with a turning knob. Arrivaderci

IF it interests some, here is ONE of many credible sites on the topic. It is a growing phenomenon.

https://pubmed.ncbi.nlm.nih.gov/32289567/

Almost any radio receiver manufactured in the last 80 years will have at least one internal oscillator.

Before that, there were Tuned Radio Frequency (TRF) radios which did not, but they were superseded by Superheterodynes, which were much easier to align accurately & having better selectivity, to use in the real world.

Googling will find so-called "TRF" radios based upon a single chip, which unfortunately, have many of the disadvantages of classic TRFs, but few of the advantages.

Prior to that, & for simple designs for many years later, there were Regenerative Receivers, which used positive feedback to cancel circuit losses.
They could also be operated in Oscillating mode, which made it easier to receive Morse & SSB signals, so such a radio would also be a "no-no".

Then there are "crystal" sets which don't use any active devices.
They are not very sensitive however, & work best when you are relatively close to the transmitting station.
In that case, any RF energy from your receiver is the least of your problems.

In any case, the device you are using to post on this forum has oscillators in both the unit itself & the switch mode power supply, either internal, or part of its charger.

There are also natural sources of Electromagnetic fields----a relatively close (several km away) lightning strike generates a much higher field strength than anything in your home.

[ArdWar]

Can anyone ELI12 me how this hypersensitivity supposed to works?

I can (maybe) understand if it's about working in intense field like radio transmitter, RADAR, MRI, etc. or even microwaves and inductive stoves.

But spurious emission from a ham radio in (I assume) receive only? Surely a well engineered one only emit in less than milliwatt range? Your PC probably emit more than that. Mobile phone would be even worse since they need to transmit to work.

[radiolistener]

But spurious emission from a ham radio in (I assume) receive only? Surely a well engineered one only emit in less than milliwatt range? Your PC probably emit more than that. Mobile phone would be even worse since they need to transmit to work.

yes, in some cases PC can produce more strong parasitic emission than digital receiver, but even small amount of noise may interfere with reception of very weak stations.

A detector receiver (LC + simple envelope detector) doesn't have emission, but on the other hand it has very bad sensitivity and selectivity

Receivers with active circuit always have some emission. Analog one has LO and BFO leakage. Digital one has wideband digital noise and a lot of parasitic carriers. But a good shielding and using RF chokes allows to minimize effect of such emissions.

[TimFox]

Repeating a link from my earlier post, here is an example of how to shield an analog superheterodyne receiver to minimize LO leakage:
https://frank.pocnet.net/instruments/EHScott/RCH/Scott_RCH_manual.pdf

[BrokenYugo]

Can anyone ELI12 me how this hypersensitivity supposed to works?

I can (maybe) understand if it's about working in intense field like radio transmitter, RADAR, MRI, etc. or even microwaves and inductive stoves.

But spurious emission from a ham radio in (I assume) receive only? Surely a well engineered one only emit in less than milliwatt range? Your PC probably emit more than that. Mobile phone would be even worse since they need to transmit to work.

You're looking at this from the wrong angle. There is nothing technical to understand about what is, per any science I've seen, irrational delusional behavior. These people aren't reacting to RF, they're reacting to their own personal idea of RF and what is and is not harmful, which conveniently ignores things like the sun, the transmitter in the phone, etc.

https://en.m.wikipedia.org/wiki/Electromagnetic_hypersensitivity

[coppercone2]

well regardless I don't think you should be shoving technology to people that don't want it, once in a while they are right. there is better agendas to have that are infinitely more useful and less difficult to achieve

i can see RF free zones being more common in the not so near future when the sensors and stuff get good enough to let people see through walls with it though. that will be easy to prove and very unnerving due to privacy. so the low emissions technology is not a bad one to explore. like when there are cheapie rydberg systems and cheap micro cryocoolers and stuff like that

[Infraviolet]

"Almost any radio receiver manufactured in the last 80 years will have at least one internal oscillator."
Worth noting though that this local oscillator will typically be stronger and more prone to causing local radio emissions in older devices (particularly the old superheterodyne types), that is how the Gestapo and the KGB used to track down people LISTENING* to foreign radio broadcasts in the territories they oppressed. Modern receivers have a much weaker local oscillator, so we'd all be able to safely recieve radio broadcasts from abroad in any future tyranny, if there was some free contry left where they were being transmitted from with enough power to overcoming jamming. The OP is either suffering psychosomatic issues (nothing to be ashamed of) or has a problem with the barely perceptible noise of some switching supplies, but if he/she really were sensitive to electromagnetic radio frequency radition then older receivers would likely be a worse option than newer ones.
*albeit at relatively close ranges

[TimFox]

The BBC used the same procedure to locate un-licensed television receivers in the UK.
Apparently, they weren't of much use.
https://en.wikipedia.org/wiki/TV_detector_van#Detection_techniques

[SpecialK]

I am anything but a troll, Electrical hypersensitivity is real, EMF stands for Electrical magnetic fields, and...thanks to some replies given, I will take the advice and go old school for a manual receiver with a turning knob. Arrivaderci

IF it interests some, here is ONE of many credible sites on the topic. It is a growing phenomenon.

https://pubmed.ncbi.nlm.nih.gov/32289567/

So I read your pubmed link.  Authors "Yael Stein" "Iris G Udasin".  Googled such.  Seem to float the idea of "Electromagnetic hypersensitivity". 


From Wikipedia:

Electromagnetic hypersensitivity (EHS) is a claimed sensitivity to electromagnetic fields, to which negative symptoms are attributed. EHS has no scientific basis and is not a recognised medical diagnosis. Claims are characterized by a "variety of non-specific symptoms, which afflicted individuals attribute to exposure to electromagnetic fields".[1]

[Simon]

well regardless I don't think you should be shoving technology to people that don't want it, once in a while they are right. there is better agendas to have that are infinitely more useful and less difficult to achieve

i can see RF free zones being more common in the not so near future when the sensors and stuff get good enough to let people see through walls with it though. that will be easy to prove and very unnerving due to privacy. so the low emissions technology is not a bad one to explore. like when there are cheapie rydberg systems and cheap micro cryocoolers and stuff like that

Oh dear, another nutter.

[Simon]

I am anything but a troll, Electrical hypersensitivity is real, EMF stands for Electrical magnetic fields, and...thanks to some replies given, I will take the advice and go old school for a manual receiver with a turning knob. Arrivaderci

IF it interests some, here is ONE of many credible sites on the topic. It is a growing phenomenon.

https://pubmed.ncbi.nlm.nih.gov/32289567/

So I read your pubmed link.  Authors "Yael Stein" "Iris G Udasin".  Googled such.  Seem to float the idea of "Electromagnetic hypersensitivity". 


From Wikipedia:

Electromagnetic hypersensitivity (EHS) is a claimed sensitivity to electromagnetic fields, to which negative symptoms are attributed. EHS has no scientific basis and is not a recognised medical diagnosis. Claims are characterized by a "variety of non-specific symptoms, which afflicted individuals attribute to exposure to electromagnetic fields".[1]

There is it's companion one of which I don't know the name but something to do with "chemicals" they hang the post on the line for days before opening it.
Due to the way society is these days instead of telling them to stop being silly we let them carry on and "respect" their non existent rational point of view. It's all 'bout feelings, "you know, man?"

[CaptDon]

I worked for 13 years in Commercial Radio Broadcasting. We, as the engineering team fielded some really idiotic calls from people effected by our transmitters and radio broadcasts. Claiming to hear the voices of dead relatives on their radio (why did they call us?) or not being able to sleep because of our 'radio waves' (They were 20 miles from the A.M. tower field and much closer to other stations). One said when she listens to 'our' station it causes the electric bill to be higher??? Crazies!!! Then we have some local crazies who park up on the bluff overlooking Lake Erie with their high beams on watching the sunset over the lake. I asked one of them why.....So the sun doesn't run out of energy!!!! I have gotten that reply more than once!!! Oh, and the years that I had an 18AVQ mulltiband antenna ground mounted and only used to receive SWL before I got my novice license and soon every neighbor was blaming me for interfering with their t.v. reception!!!

[radiolistener]

Oh, and the years that I had an 18AVQ mulltiband antenna ground mounted and only used to receive SWL before I got my novice license and soon every neighbor was blaming me for interfering with their t.v. reception!!!

Many peoples just don't know that electromagnetic field strength is much more safe for health with a large antenna than with a very small one...

They just thinking that since their mobile phone has a very small and hidden antenna it produce much smaller field strength than a very large antenna. This is their mistake due to a lack of knowledge... The mobile phone produces extreme high RF field strength which exceeds safety limits, while a large shortwave antenna doesn't exceed safety limit even if it pushing 2000 W power into air... 

This is something like compare safety of a large 2 kW spotlight with a tiny 2 W laser. Yes, 2 kW spotlight produce a lot of light, but its safe to see on it from some distance. But if you try see directly a 2 W laser from the same distance, it will lead to eye damage and blindness... Despite the fact that it's very tiny and has just 2 W power.

This is because laser has very high power flux density, so it give very high concentration of energy within a limited space volume. The same happens with a very small antenna, it has very high concentration of energy within a limited space volume around antenna... But the problem here is that people don't see these fields, so they don't realize that a large antenna is much more safe than a tiny one...

[wizard69]

I am anything but a troll, Electrical hypersensitivity is real, EMF stands for Electrical magnetic fields, and...thanks to some replies given, I will take the advice and go old school for a manual receiver with a turning knob. Arrivaderci

IF it interests some, here is ONE of many credible sites on the topic. It is a growing phenomenon.

https://pubmed.ncbi.nlm.nih.gov/32289567/

I don't by it that it is real.   However I'm opened minded enough to ask for credible evidence from sound scientific testing.    I doubt you can find such though.   Besides that Electrical magnetic fields will come from any device, microprocessor or not.   You can't have the magnetic without the electric.   Any magnetic fields generated by a microprocessor would be so minute compared to the rest of the hardware to be impossible to notice.