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Ideas for improving indoor FM reception?

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modrachlan

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#1
I am trying to improve stereo reception of a station about 30 miles away to the North/Northwest.The building I am in is about 20 vertical feet from the crest of a hill. I have access to interior spaces, but nothing outside. Sadly, I am on the ground floor of the building. There are two big north-facing windows, and I have a 300 ohm standard dipole tacked up right above one of them. I've tried to keep the lead as short as possible, though I did have to add about two feet of copper wire to the downleads to reach my FM tuner due to the room layout.

Observations:

(1) Dipole fed to 300 ohm input, both wires- 1 signal unit, high background noise in stereo
(2) Dipole fed to 300 ohm input, one wire (either one)- 1 1/2 signal units, slightly lower noise
(3) Same as 2, with a length of wire added to the second terminal, stretched across the bottom of the window pane- 2 1/2 units, noise level not bad, but not great. Getting there.

So, here is my question- can you think of anything I can do that would be better than this?

One thing I have considered, but not tried- building a 30" on a side loop from some coax and stretching that across the window.

Any thoughts?
 
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#2
Hard to say without seeing the location.

If said hill is between you and the station you want to listen to, then you are at a bit of a disadvantage.
The glass might be tinted, which often uses metalized film, which can effectively block radio signals.

Ideally, an exterior directional antenna would help, but that's not an option in your case.

Internet streaming comes to mind. If the radio station doesn't offer it, you could set up a receiver at your home (if you can receive the station there) and stream it to a computer at your work, if you have internet access at both locations.

Any antenna inside the building is going to be at a disadvantage. A loop antenna might improve things, might not. Really depends on a number of factors. High RF noise environment from electronics inside the building might be part of the issue.

Experimenting is key. It's difficult to know what's going to work since there are so many variables that would be specific to your own installation.

Look up "Yagi antenna" on line. Sometimes you can build a simple one out of wire. Maybe put it on a piece of cardboard, or suspend it from the ceiling. Yagi antennas are directional and will help performance a bit.

I suspect your #3 above is that you've created a counterpoise that is helping with reception. One thing you could try is to ground that lead carefully to a water pipe, electrical conduit, etc.
 

modrachlan

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#3
Interesting theory about the counterpoise. securing it to a ground is easy to confirm, so I'll try that next.

Also good to know about the windows- they are indeed tinted. Maybe by hook or by crook, I could get a wire out the window. Maybe 8 feet?

I will check yagi designs out. Maybe I can tack something to the ceiling.

Thanks.
 
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#5
Also good to know about the windows- they are indeed tinted.
This is a H-U-G-E issue on the public safety and cellular side. "Low-E" glass, as they call it, and high energy efficiency building practices are creating buildings that are becoming impervious to RF. Fire Code is starting to require bi-directional amplifier systems in new buildings to address public safety radio coverage. Cellular carries are having to do the same thing.

I have a building at work that is 75 yards from and outdoor cellular distributed antenna system site. You can stand in the building looking through the window at the cell antennas and a cell phone will show "no service".
But hey, the building won awards for energy efficiency!
 
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#7
I assume you have been using the arial that often are included when you buy a HiFi stereo with a FM receiver? It is a 300 ohm ladder line with a 300 ohm antenna. The ladder line and antenna are extreamly sensitive to any metal objects that are too close to it. The lenght of the lead are not an issue as it doesn't matter with ladder line and these frequencies. If you extend it you have to use the same ladder line, not any copper wire you can find.

Most windows have a metal frame around it in the wall and putting an antenna behind it or very close to it are not adviced.

Some FM broadcast stations use horisontal polarisation and some use vertical. If you have your antenna the wrong way it will reduce the signal a lot. I suggest you attach the antenna to a wooden broom handle or similar and try to find a place in the room and at different angles of the antenna where you get the best reception. I tacked my antenna to the ceiling at the best angle to receive some stations noise free but later had it hanging vertically on a wooden wall to receive other stations.

If you have trouble keeping the ladder line off from interfering metal objects you should switch to RG6 coax and use the 75 ohm antenna input. As antenna you connect a wire to the inner lead and another equal lenght to the coax braid so that the lenght tip to tip is 5 feet. Try that both vertical and horisontal and also angles between and at positions that you could have it permanently mounted.

Building that FM loop seems like unneccesary work in your situation.

/Ubbe
 

modrachlan

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#8
I assume you have been using the arial that often are included when you buy a HiFi stereo with a FM receiver?
Yep, that's me.

If you extend it you have to use the same ladder line, not any copper wire you can find.
VERY good to know. Thank you. I spent yesterday just trying to work out a combination of 300 ohm dipole and some spare copper wire.

Most windows have a metal frame around it in the wall and putting an antenna behind it or very close to it are not adviced.
We just got new windows two weeks ago. All metal framed. Darn it.

If you have trouble keeping the ladder line off from interfering metal objects you should switch to RG6 coax and use the 75 ohm antenna input. As antenna you connect a wire to the inner lead and another equal lenght to the coax braid so that the lenght tip to tip is 5 feet. Try that both vertical and horisontal and also angles between and at positions that you could have it permanently mounted.
I wonder if if would eliminate the problem entirely by just make one out of coax, like this one. https://www.youtube.com/watch?v=KjTshXYsRss

Building that FM loop seems like unneccesary work in your situation.

/Ubbe
Thanks for all the useful information!
 
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