How is tx & rx antenna VSWR effected by the antennas being inside a metal shed or aircraft hangar?

Thread Starter

genekuli

Joined Oct 21, 2018
103
transmitting inside a common metal garden shed or aircraft hangar, how does that affects the antenna matching VSWR of the Tx and Rx antennas?
it is not for transmitting out of the shed.
it is for tx and Rx inside the shed.
and does the wavelength relative to the size of the shed matter?
 
Last edited:

Delta prime

Joined Nov 15, 2019
841
Please you should know better place it inside a metal box of course you've heard about Fairday cages correct
Paraphrasing Wikipedia
Faraday cage or Faraday shield is an enclosure used to block electromagnetic fields.A Faraday shield may be formed by a continuous covering of conductive material, or in the case of a Faraday cage, by a mesh of such materials.Faraday cages are named after scientist Michael Faraday, who invented them in 1836.
 

Thread Starter

genekuli

Joined Oct 21, 2018
103
Please you should know better place it inside a metal box of course you've heard about Fairday cages correct
Paraphrasing Wikipedia
Faraday cage or Faraday shield is an enclosure used to block electromagnetic fields.A Faraday shield may be formed by a continuous covering of conductive material, or in the case of a Faraday cage, by a mesh of such materials.Faraday cages are named after scientist Michael Faraday, who invented them in 1836.
it is not for transmitting to out of the chamber.
it is for tx inside the chamber
 

Thread Starter

genekuli

Joined Oct 21, 2018
103
for example tx antenna transmitting inside a common metal garden shed, how that effects the antenna matching.
 

Yaakov

Joined Jan 27, 2019
2,902
transmitting inside a common metal garden shed or aircraft hangar, how does that affects the antenna matching VSWR of the Tx and Rx antennas?
it is not for transmitting out of the shed.
it is for tx and Rx inside the shed.
and does the wavelength relative to the size of the shed matter?
I don’t know about other folks but veiled questions are, to me, an insulting way of trying to get information. If you can’t describe, in some detail, your actual problem and allow those who would try to help you decide if the information they provide is actually an answer to the hidden question, you are wasting their time—hence the ”insulting” part.
 

Thread Starter

genekuli

Joined Oct 21, 2018
103
I don’t know about other folks but veiled questions are, to me, an insulting way of trying to get information. If you can’t describe, in some detail, your actual problem and allow those who would try to help you decide if the information they provide is actually an answer to the hidden question, you are wasting their time—hence the ”insulting” part.
sorry, but my "actual" question as you put it is way too long and complex to ask here so i am just asking only the parts that i absolutely can not discover my self. i know this may appear disjointed and lack context
 

Yaakov

Joined Jan 27, 2019
2,902
sorry, but my "actual" question as you put it is way too long and complex to ask here so i am just asking only the parts that i absolutely can not discover my self. i know this may appear disjointed and lack context
The problem is, if you can't answer the real question you have no idea if the answer to your obfuscated one will be pertinent to it. You have attempted to partially solve something you don't understand by providing a hypothetical you imagine is a model of that thing.

Problems like this are not reducible in the way you are hoping.

I'm done with this thread and anything related to it.
 

SamR

Joined Mar 19, 2019
3,244
Being inside a metal enclosure has no effect on matching transmitter frequency to antenna wavelength so the SWR is not changed.
 

PadMasterson

Joined Jan 19, 2021
26
You should also remember that if you are transmitting on frequencies in the Aircraft band, you best be sure they are very low power or you could have the FAA and FCC at your door in very short order. Interfering with ATC frequencies is a federal crime and issue and they don't like people messing with critical frequencies like that. Just saying...
 

DC_Kid

Joined Feb 25, 2008
806
Do an ez experiment. Get a cheap CB radio band vswr meter box, a CB radio (handheld is ok), and a CB antenna (stick) that you can cut down to tune. Try for a 1:1. Do this outside with a decent ground plane.

Take that exact setup into your metal box, what does the vswr meter show you now?
Do the same thing in the box but connect your ground plane to the metal box, what does vswr show you?

Interesting? Boring? You tell us.

caveat: you may need adapter to cable CB to meter, and antenna to meter.
 

Janis59

Joined Aug 21, 2017
1,330
RE: Delta. Faraday cage principle means that ANY SIGNAL FROM INSIDE IS INSTANTLY PROVIDED TOWARD OUTSIDE. So, none signal froom outside may not come inside. But all signals from inside are self-forwarded to outside. Just one example. The small monitoring data solutions consultant firm where sometimes I am invited to solve the painful bottlenecks, undersigned a deal with large diesel driven electrostations exploiting (best Latvian Beer producer) factory needs to make a radiolink for monitoring the alternator temperature, humidity, voltage, FC etc etc parameters in www to the main contor in neighborous village. When arrived there and mounted the sensors, was clarified that generators work in the hermetic 2 mm zinced steel earthened container where if drill any tiniest hole in the wall or ceiling then warranty on generators are sure lost. So, its forbidden to drill an antenna or any other cable through wall, but internet stays 1 km afar. So, I said, okay guys, at least we can today assess do the sensors are being read. Yes, they was, and through the opened door the signal strength was about 60% instead of normal 99%. So, not believing on such blind hen luck I said, probably let close the door and we shall have at least 1% strength to use a surplus retranslator somewhere near the door gap? We closed the door and signal strength was 25% (the housing is earthened by two well digg zinc rods in 6 meters deep). So, my Eureka was, ah, the earthening have large inductance some 6 meters multiplied to 10 nH for each cm. Actually, when good weather that 25% of Lora(tm)=868 MHz coming out of the closed earthened Faraday cage was enough to cach an internet without of retranslator, but we installed retranslator few meter afar at pine-tree up so now is the third year this system works well. Only many month later I found the intriguing reason, tah Faraday cage is working unidirectionally.
 

Thread Starter

genekuli

Joined Oct 21, 2018
103
Being inside a metal enclosure has no effect on matching transmitter frequency to antenna wavelength so the SWR is not changed.
thank you, but what if it is one wavelength distant of the Tx frequency or within one wavelength distant of the Tx frequency ?
 

andrewmm

Joined Feb 25, 2011
1,235
thank you, but what if it is one wavelength distant of the Tx frequency or within one wavelength distant of the Tx frequency ?
then depending upon the earthing, you could end up with a standing wave.
which if I remember the antenna could worse case then appear as a short or open circuit .
 

Thread Starter

genekuli

Joined Oct 21, 2018
103
then depending upon the earthing, you could end up with a standing wave.
which if I remember the antenna could worse case then appear as a short or open circuit .
you mentioned a standing wave within the metal chamber in the scenario, how could this be deliberately set up? what is needed to be satisfied to create this? would the antennas have to be half wavelength from walls of metal chamber, that is, centred? or is it just the size of the chamber that matters?
 
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