John Curl's Blowtorch preamplifier part III

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#585
DF96 said:
We have infra-red detectors in our skin, so it is not beyond the bounds of possibility that in some individuals these could detect ionising radiation too. However, I suspect that if it is enough to detect this way then it is enough to do harm. It is a long way from this to detecting underground water, which as far as I know does not emit significant amounts of any radiation.
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Whenever I have to use the "hotspot" feature on my cellphone, I get the hibby-jibbies touching it. I'm not sure whether it's cause I know that I quadrupled (or more) the radiation, or because it literally feels hotter to me.
 
#586
It is a real effect.
Historically, the effect of ionizing as well as non ionizing radiation on living tissue was accessed by measuring the temperature increase of the target mass when radiation intensity was increasing by a certain amount.
Target mass was made by a special gel formulation modelling some properties of real tissue.

George
 
#587
gpapag said:
It is a real effect.
Historically, the effect of ionizing as well as non ionizing radiation on living tissue was accessed by measuring the temperature increase of the target mass when radiation intensity was increasing by a certain amount.
Target mass was made by a special gel formulation modelling some properties of real tissue.

George
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Ohh yes the effect is real. I remember from my airforce air defense radar times, body tissue definitely can be heated by prolonged exposure to microwave radiation. And don't forget the kitchen microwave!

Jan
 
#590
Destroyer OS said:
Whenever I have to use the "hotspot" feature on my cellphone, I get the hibby-jibbies touching it. I'm not sure whether it's cause I know that I quadrupled (or more) the radiation, or because it literally feels hotter to me.
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The latter - the GPS core in your phone is power hungry ( I used to design them and they are getting better)

Radiation harm is, as mentioned before, determined by its thermal effect on tissue. On that basis modern cellphones/WiFi/BT devices are harmless but there is debate that cellular effects unrelated to tissue heating may cause harm. But it is hard to find control subjects anymore and the ethics of a DB clinical trial are dubious.
 
#592
VivaVee said:
The latter - the GPS core in your phone is power hungry ( I used to design them and they are getting better)

Radiation harm is, as mentioned before, determined by its thermal effect on tissue. On that basis modern cellphones/WiFi/BT devices are harmless but there is debate that cellular effects unrelated to tissue heating may cause harm. But it is hard to find control subjects anymore and the ethics of a DB clinical trial are dubious.
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All the late (epidemiological) research I've seen has made this an open and closed issue, the only controversy is in the court of public opinion and the unfortunately ubiquitous cranks. There's no dose effect.

Edit, except of course their powers of distraction.
 
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#593
DPH said:
All the late (epidemiological) research I've seen has made this an open and closed issue, the only controversy is in the court of public opinion and the unfortunately ubiquitous cranks. There's no dose effect.

Edit, except of course their powers of distraction.
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I have not looked at recent studies but how do you find control groups that are not exposed to EM radiation? It is so damned ubiquitous.
 
#594
VivaVee--when I get back on my work network where I have access to journals, I'll have a look. IIRC, recent studies try to look at dose-response effects. E.g. "do very frequent phone users show something significantly different to infrequent users?"

But I'm not seeing much in the way of abstracts when searching Google Scholar for "Cell phone dose-response". The most damning is that adolescents who use a phone a lot don't sleep. (Shocking!)
 
#595
I do hope people realize that the term 'hot spot' for access to internet is just a marketing term for a location where you can log on to the network, and it's not really a hot spot by any means. Right?
I mean come on. The WiFi at your home is a hot spot if there ever was one!

Just like we do not think that the hot and cold output wires of our amp are different in temperature. At least I hope we don't.

Jan
 
#597
jan.didden said:
I do hope people realize that the term 'hot spot' for access to internet is just a marketing term for a location where you can log on to the network, and it's not really a hot spot by any means. Right?
I mean come on. The WiFi at your home is a hot spot if there ever was one!

Just like we do not think that the hot and cold output wires of our amp are different in temperature. At least I hope we don't.

Jan
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It's the name on my phone for it, why would I call it something else? 🙄
 
#599
If one wants to use jfets in preamps or I/V converters it means for sure that is going to be expensive exoteric equipment. Unobtainable complementary jfets and need for meticulous matching it's main obstacle to get cheap (moneywise) equipment.
Why not to use bjts only and the matching problem solve by using low noise matched quads as THAT340 .
Here is one example of the current to voltage converter suitable for a DAC outputs. It’s non balanced configuration but easily upgraded to balanced one.
The main source of noise are those current to voltage resistors, in this case R19 and R1. Lower the resistor value les nose, but increase in distortion.
And yes, this is non GNFB circuit.
Damir
 

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