Artisan Radio, at least for the moment, is located in a concrete highrise. Lots of windows, but they are surrounded by aluminum framing. Of course, there's rebar embedded in the concrete.
The FM transmitter/antenna is located beside a window to the balcony, which has an overhang made of the same concrete.
I was testing a potential AM antenna - basically, a wire running up a bamboo stake, and I was astonished at some of the results.
With that stake outside on the balcony, just beside the window, the AM signal was hugely attenuated inside the apartment. Moving the stake inside beside the same window, a distance of under a foot, hugely increased the signal strength inside. Crazy.
FM is not affected, and the height of the antenna, in fact, increases the range well beyond what might normally be expected with BETS-1.
It really shows the effect of concrete/rebar/metal on AM. I also think that the windows are coated with some sort of reflective coating material, which is affecting the AM signal as well.
I doubt that the window is anything but normal glass. Must be other things at play. Reflections whatever. The window may be double paned with space inbetween for insulation but other than that nothing.
Was the AM signal better outside with the antenna out on the balcony? Does it get out to the ground?
I actually can't hear it outside on the ground when the antenna is inside.
I haven't tested it yet when the antenna is outside. That's the next step. I'm hoping. I can live without hearing it inside, run a private stream or something for inside the apartment.
Understand that this is a difference of inches, the only thing changing was the glass in between. And I guess moving the antenna a bit more inside the concrete Faraday Cage.
I'm also going to try different parts of the balcony (it's fairly large).
I recall in a Talking House manual it saying something about it not doing good with glass and stucco and it being best to install in the garage.
I was surprised that it indicated that a window can attune the signal - it said to keep the transmitter away from them
Carl's "wintenna" however seems to disprove that.
@richpowers Glass by itself is transparent to RF. Including AM frequencies. Usually in a building to get AM reception you go to a window. So what comes in should go out. I wonder what could be in the makeup of the window?
@artisan If you put the antenna out on the balcony the strong signal from the Talking Sign can't be received inside?
Remember the story about the person that had a Talking House in an apartment building and the signal got into the wiring and the whole building was radiating and carried quite a ways?
And it was with the power supply it came with, with the 3rd grounded plug like the ones that we...artisan and I have. Those grounded power supplies are not to be found now anywhere and I called Globe Tek Electronics, gave them the model number and they said non existent now. I have to see if Gerry has any more of those. It grounds an AM transmitter through the house or building ground.
If the antenna is on the balcony (outside), in front of a window, the signal is very weak inside. If I move the antenna inside, in front of the same window (but on the other side), the signal is strong throughout the apartment.
That's why I was wondering if maybe there is some sort of metallic reflective coating on the windows. A few more tests and I'll have a lot more information.
Up to this point, I've only been using the Talking Sign to generate an AM signal for the SDR, and I didn't care about outside reception (in fact, the antenna wire was just draped over something inside), not even vertical. I was still pegging the tuning meter on the transmitter, so the built-in tuner was able to match it (it's pretty versatile, as it's manual, not like the Talking House which can churn forever if it doesn't find a match).
I've always had issues with amateur radio antennas on the lower frequencies in concrete buildings. The only band I've ever gotten to work half decently on HF is 10 meters (28 Mhz). I remember I had a Chameleon brand auto matching antenna on a balcony that I could only ever get to receive the very strongest signals on any frequency from 14 Mhz and lower. On a car in the open the signals (on the same bands) just came pouring in. Up until then, I was beginning to think that the problem was in the radio itself, but no. The same radio with the same antenna had no issues in the car with the aforementioned scenario.
That's why I was wondering if maybe there is some sort of metallic reflective coating on the windows. A few more tests and I'll have a lot more information.
Evidently there is some energy efficient glass called Low-E that as a side effect is known to block radio, and there are also special "RF Blocking Films" applied to windows.. kind of interesting, there's even window curtains made specifically to block rf.
I know that new transparent solar panel glass is set to, or maybe already has been installed in new buildings.
@richpowers How about someone that wants to listen to radio? Talk about interfering with ones right to listen to radio in their own home. Good to know. If I ever went into a building I will take a radio to check this.
But it affects AM and not FM?
@mark I only know what google said when I asked "Can windows block radio waves"
https://www.google.com/search?q=can+windows+block+radio+waves
Also some glass has lead in it..
@richpowers If it's old glass on a house prior to, what, 1978 in the USA, it could have Pb in it. And lead in the paint, and so forth.
@centinel Yep, there's not much in our society that doesn't interfere with radio waves.