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 Indoor FM reception
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 Return to top of page · Post #: 1 · Written at 3:03:28 PM on 2 May 2020.
Gandhn's Gravatar
 Location: Cameron Park, NSW
 Member since 5 November 2010
 Member #: 770
 Postcount: 385

Our house has foil backed insulation in the walls, a Colourbond roof and bronze mesh fly screens on the windows, making a very effective Faraday cage. I have a couple of FM radios with a simple rod antenna and their reception is terrible.

I am looking for suggestions on how to get a decent FM signal inside the house, other than mounting an outside antenna and cabling, as none of the radios have an antenna input, only the telescopic rod.

Any and all ideas are welcome.

Harold


 
 Return to top of page · Post #: 2 · Written at 3:19:19 PM on 2 May 2020.
Vintage Pete's avatar
 Location: Albury, NSW
 Member since 1 May 2016
 Member #: 1919
 Postcount: 2048

Hello Harold , Unfortunately, I don't have any foil between the bricks and the wall, Which makes it extremely hot in the summer, But my FM Reception is shocking here at Albury, Mostly I listen to AM,,, I now use a Blue tooth Module and I listen to any station I want on my 50s and 60s Radiograms. , It cost me 30 bucks for Jay Car ... But you may just be looking for running a wire etc which I can't help you with, I just wanted to say how I got around the problem ,I'm very happy with the sound , It's clear as a bell on my Radiograms,
All the best Pete


 
 Return to top of page · Post #: 3 · Written at 4:02:17 PM on 2 May 2020.
GTC's avatar
 GTC
 Location: Sydney, NSW
 Member since 28 January 2011
 Member #: 823
 Postcount: 6678

That's tough one Harold. Effective Faraday cage indeed. Places like harbour tunnels use rebroadcast systems. I'd be inclined to pipe the audio into rooms from a central receiver which would require a good outdoor antenna. If you only listen to one or two FM stations you wouldn't need remote control.

An alternative is live streaming from the internet.


 
 Return to top of page · Post #: 4 · Written at 4:15:41 PM on 2 May 2020.
Ian Robertson's Gravatar
 Location: Belrose, NSW
 Member since 31 December 2015
 Member #: 1844
 Postcount: 2363

You could make your own passive rebroadcast system.

Do you still have your Newcastle TV antenna? Re-purpose that. Connect it to a 2nd antenna inside the house. Just a dipole tuned to Band 2.

If the Faraday cage is really effective you could add some gain using an old booster amp that works on Band 2.


 
 Return to top of page · Post #: 5 · Written at 4:26:20 PM on 2 May 2020.
Vintage Pete's avatar
 Location: Albury, NSW
 Member since 1 May 2016
 Member #: 1919
 Postcount: 2048

Curious about this Topic of Reception and the only way I'm going too know more is if I ask, So Would a free Standing Loop Antenna placed behind the Radio you wish to use work? Or no good for FM ? I imagine the foil would still block the signal? Before I Bought my Module I was toying with the Idea of building one , But my aim was AM


 
 Return to top of page · Post #: 6 · Written at 4:57:56 PM on 2 May 2020.
Gandhn's Gravatar
 Location: Cameron Park, NSW
 Member since 5 November 2010
 Member #: 770
 Postcount: 385

Do you still have your Newcastle TV antenna?

Yes, that is still in use with VHF and UHF dipoles, however it has a booster amplifier which only passes the current digital frequencies. The idea of a passive rebroadcast is what I had in mind, just how to do it?

Harold


 
 Return to top of page · Post #: 7 · Written at 5:31:12 PM on 2 May 2020.
GTC's avatar
 GTC
 Location: Sydney, NSW
 Member since 28 January 2011
 Member #: 823
 Postcount: 6678

There's also this approach but, again, a good main antenna is required: https://www.ebay.com.au/itm/133382701180


 
 Return to top of page · Post #: 8 · Written at 6:11:42 PM on 2 May 2020.
Ian Robertson's Gravatar
 Location: Belrose, NSW
 Member since 31 December 2015
 Member #: 1844
 Postcount: 2363

Harold, what frequencies is digital TV using where you are? Only Band 3 in Sydney now.

You can get a Band 2 extractor and install it ahead of the TV feed.


 
 Return to top of page · Post #: 9 · Written at 6:14:44 PM on 2 May 2020.
Brad's avatar
 Administrator
 Location: Naremburn, NSW
 Member since 15 November 2005
 Member #: 1
 Postcount: 7290

G'day Harold,

Before I read Ian's comment I was thinking along the same lines as he did but using an FM transmitter kit to rebroadcast with. The stumbling block here is that if you want to change stations, it would have to be done on the receiver feeding the retransmitter rather than the receiver you are listening to.

Ian's idea makes sense, though you'd probably have to have line of sight to the indoor dipole.


‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾
A valve a day keeps the transistor away...

 
 Return to top of page · Post #: 10 · Written at 6:41:20 PM on 2 May 2020.
Ian Robertson's Gravatar
 Location: Belrose, NSW
 Member since 31 December 2015
 Member #: 1844
 Postcount: 2363

There used to be a TV rebroadcast "passive" repeater for Thredbo Village. The TV signals were picked up by antennas on one side of the top of the mountain and cabled to the old metal roofed chairlift nacelle - the open end faced the village. Inside the nacelle were 3 yagis pointing to the village, rebroadcasting the amplified antenna signals on the same frequencies.

You may have enough shielding in your house to do something similar, just use 10 or 12 dB gain on Band 2. Too much gain and you'll get feedback, obviously.


 
 Return to top of page · Post #: 11 · Written at 8:19:28 PM on 2 May 2020.
Gandhn's Gravatar
 Location: Cameron Park, NSW
 Member since 5 November 2010
 Member #: 770
 Postcount: 385

Thanks everyone, for your inputs. Climbing on the roof to fiddle with the TV antenna is now beyond me, but installing a FM band only antenna on the gutter would be a much simpler operation. If it could feed a wide band amplifier, (88 to 108 MHz) and drive an antenna in the house, I could be in business. It means that the radios are usable on all frequencies in the band.

Does this sound like a mini version of the Thredbo system that Ian referred to? Is such an amplifier available, other than for (expensive) commercial use?

Harold


 
 Return to top of page · Post #: 12 · Written at 8:41:25 PM on 2 May 2020.
Ian Robertson's Gravatar
 Location: Belrose, NSW
 Member since 31 December 2015
 Member #: 1844
 Postcount: 2363

The trick is to get the outside receiving antenna as far away from the indoor one as practical.

As a proof of concept, try doing a "broomstick". Place the antenna outside (e.g. on a broom handle) as high and in the clear as you can and run the coax inside. Connect the coax to an indoor TV antenna if you have one. See if that helps.


 
 Return to top of page · Post #: 13 · Written at 4:32:04 AM on 8 May 2020.
Wa2ise's avatar
 Location: Oradell, US
 Member since 2 April 2010
 Member #: 643
 Postcount: 830

If you can get at the foil, maybe you can create a slot antenna.

in the foil. The length of the slot would be a half of a wavelength, for the FM broadcast band 100MHz this half wavelength is 1.5 meters long. The width of the slot I think is about a cm or so (seems not critical). The feedpoint you connect twinlead to is at the middle of the slot. A vertical slot acts like a horizontal dipole antenna (while the slot is omnidirectional at the horizon, hard to do with regular dipole antennas and be horizontally polarized). And a horizontal slot will act like a vertical dipole antenna.


 
 Return to top of page · Post #: 14 · Written at 8:58:28 AM on 8 May 2020.
Ian Robertson's Gravatar
 Location: Belrose, NSW
 Member since 31 December 2015
 Member #: 1844
 Postcount: 2363

VERY good idea!


 
 Return to top of page · Post #: 15 · Written at 10:04:20 AM on 8 May 2020.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 5239

Owing to this being an issue especially in this shed, and to an extent in the house. The two principle radio's and the mobile phone take antennas & one also has a long wire attached to it.

The TV FM antennas of the house are on the Barge board (nearest neighbour 1/2 mile) Shed 11/2" pipe, longwire abt. 50m on poles. A slot cut in a metal plate can make a resonator.

A smart modem instead of a dumb provider would solve some phone issues.

Marc


 
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