7
votes
Accepted
Are amateur radio operators more likely to get cancer from exposure to RF?
FCC's page on this at https://www.fcc.gov/general/fcc-policy-human-exposure which links to several other documents including FCC OET Bulletin 56, "Questions and Answers about
Biological Effects ...
- 4,203
6
votes
Can the tip of an antenna burn insulation/drywall?
The peak voltage at the tip of the antenna is a function of the input power and the field impedance at that tip. The impedance varies based on the geometry of the antenna, but for a typical mag-mount ...
- 49.8k
6
votes
Accepted
Does amateur radio induce a health risk?
Sure, there are plenty. Unfortunately, they all seem to be selling something.
The scientific consensus is quite clear: no known risk, beyond the obvious risk of being cooked which MPE limits are set ...
- 49.8k
6
votes
How far from a cable entry point can the lighting suppressor be installed
The picture you have drawn suggests a lightning suppressor installed in this way will do little to nothing to protect your station.
The suppressor does only one thing: it limits the maximum voltage ...
- 49.8k
5
votes
Accepted
How safe is 100 watts on 2-40 meters?
The FCC has published a bulletin OET 65B that has a table showing for VHF you don't need to evaluate the RF hazard if your effective power is 50 watts or below. For 70 cm UHF the limit is 70 watts. ...
- 1,208
5
votes
How to safely listen to my transmitted signal with a second receiver
If the receiver is close to the transmitter, and you are transmitting with more than a few milliwatts, just fire up the receiver with no antenna attached. Not having an antenna makes the receiver far ...
- 49.8k
5
votes
Can I have the Hytera PD785G turned on in the charger?
Never owned a similar device, but judging from the product pictures:
Indeed, the charging logic for the battery is not inside the handset, but the charging cradle, and hence, that would quite likely ...
- 13.3k
5
votes
Accepted
What safety procedures should be followed when developing and testing a high power amp?
Get yourself a dummy load.
If your gut is telling you your doing something stupid you're doing something stupid.
Keep the power supply switch near by.
Always assume it's live.
If you have doubts about ...
5
votes
Accepted
Transmission power of Apple Wi-Fi antennas (EMF and health)
Maximum permissible power output for Part 15 operation is 1W; Apple devices are known to use up to that limit.
e.g. https://fccid.io/BCGA2589/Test-Report/WLAN-OFDMA-Test-Report-1-5691887.pdf
The above ...
- 176
4
votes
Accepted
Is it safe to live close to cellular antenna?
Cellular networks are heavily regulated all over the world. Part of these regulations is that there's no amount of power radiated in any inhabitable direction that would pose a risk to the health of ...
- 13.3k
4
votes
why do some radios have two fuses in the power leads
According to Alan K0BG's page about wiring, the negative lead is fused because of the possibility of a faulty ground elsewhere in the vehicle, which could cause excessive current to flow in the ...
- 8,922
4
votes
How to safely listen to my transmitted signal with a second receiver
Also, there's a lot of attenuators out there. Just do the math: If your transmitter is capable of thransmitting let's say 20 dBm, and your receiver has a sensitivity of -90 dBm and a max input of 10 ...
- 13.3k
4
votes
Antenna installation for a base station
Regarding the overlap of the mast to the antenna, there should be about 1 foot of overlap as shown in this picture:
The top of the pipe must stay below the decoupling radials in order for the antenna ...
- 18.1k
4
votes
Do lightning rods attract or do they help prevent lightning?
These ideas have been around for centuries as lightning dissipation theory and lightning diversion theory.
Notably, Benjamin Franklin was an early proponent of lightning dissipation theory. He noticed ...
- 49.8k
4
votes
Will my neighbor's amateur RF antennas effect my own utilities?
The frequencies your neighbor would be transmitting are different than the ones your own communications would use. They should not interfere with your utilities.
Occasionally, funny things like old ...
- 5,995
4
votes
distance between shack and antenna
Various organizations have issued guidelines on maximum permissible exposure. Below a certain power, the station can be assumed harmless. Above that power, some more careful design is prudent. Your ...
- 49.8k
4
votes
What safety procedures should be followed when developing and testing a high power amp?
If you do have to stick a scope probe or adjustment tool into it, take off all your rings, watches, bracelets, necklaces, etc., before reaching into anything (or around any uncovered circuitry) that ...
- 12.4k
3
votes
Accepted
Does copper wire get sold as flat straps to reduce inductance?
You can buy copper strap at Georgia Copper. There are other sources, such as DX Engineering's Georgia Copper page.
For RF, it is better to use this copper sheet metal strap wherever possible. The ...
- 7,495
3
votes
How is working on DC high voltages as in a tube radio different from 120VAC?
800 volts is far more likely to burn you. Just doubling the voltage from 120 to 240 will quadruple the power heating your flesh.
This is just basic Ohm's Law: [P=E*I]
DC is one nasty customer:
It ...
- 7,495
3
votes
How can I protect equipment against a lightning strike?
What you need to do is follow the requirements of the National Electrical Code (assuming USA).
This article covers it well.
(ps. Failure to comply with NEC 810 is the #1 reason ham radio operators in ...
- 131
3
votes
Accepted
How much EMF does a typical scanner put out?
What I would like to know is; how much EMF/RF does an average scanner emit?
No more than your TV, electric lights, or phone charger. In fact, quite possibly less. Certainly far less than your cell ...
- 49.8k
3
votes
Estimating near-field electric field strength at LF (137 kHz)
Estimating the near field is best done with modeling software or empirical measurement. The details of the antenna construction and environment (the ground and any nearby conductive objects in ...
- 49.8k
3
votes
Accepted
Estimating near-field electric field strength at LF (137 kHz)
Below is a rough estimate of the near fields calculated by NEC4.2 for an elevation of 3 meters above level Earth from a transmit antenna and system as generally described in the OP, and the followup ...
- 2,872
3
votes
Accepted
Do modern radios and power supplies require grounding for safety?
The OP states clearly that the only interest is safety. That is how I answer the question.
In most countries there is a category of equipment that is double insulated. If your radio is connected to a ...
- 46
2
votes
Does amateur radio induce a health risk?
There are some indications that RF has ill effects on humans, at least in certain configurations or environments. Here are a few references taken from the top search results from Google Scholar. It ...
- 561
2
votes
DIY lightning arrestor - gap size?
Get a two terminal GDT and call it a day, use very short low inductance leads to attach it between the center conductor and earth ground. GDT (Gas Discharge Tube), Bourns make them, Digikey or Mouser ...
- 21
2
votes
Is it safe to live close to cellular antenna?
I think the biggest risk you would take by renting such an appartment is terrible cellular reception. If your provider is one of the providers using the antenna on top of your building, that would ...
2
votes
Is it safe to live close to cellular antenna?
The FCC has a bulletin on this. It says (page 21):
Measurement data obtained from various sources
have consistently indicated that "worst-case" ground-level power densities near typical cellular
...
- 49.8k
2
votes
Antenna installation for a base station
I would say the mast must extend only high enough to provide appropriate mechanical support. Glenn W9IQ provides a great illustration.
Having the mast extend above the antenna might provide some ...
- 49.8k
2
votes
overhead power-line safety
Just make sure that supports are fully anchored and supported other than that check with local codes to make sure that wires that you are putting up are away a certain amount.
If you are in a major ...
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