FM, no static at all (calling all radio nuts, Buzby)

[Rizla]

I've got my nice old tuner set up today, and for an aerial I'm as usual using some speaker wire in a dipole set-up, 75cm per pole, hanging vertically. The reception's grand across pretty much all frequencies in mono, but stereo gets enough background hiss to make Radio 3 organ recitals a less than stellar listening experience. I'm wondering if I need something like this. Or am I just not finding the sweet spot with the ghetto ribbon set up I'm using? Is it indeed possible to get a crystal-clear stereo reception across all the UK FM frequencies?

[buzby]

I've got my nice old tuner set up today, and for an aerial I'm as usual using some speaker wire in a dipole set-up, 75cm per pole, hanging vertically. The reception's grand across pretty much all frequencies in mono, but stereo gets enough background hiss to make Radio 3 organ recitals a less than stellar listening experience. I'm wondering if I need something like this. Or am I just not finding the sweet spot with the ghetto ribbon set up I'm using? Is it indeed possible to get a crystal-clear stereo reception across all the UK FM frequencies?

Have you connected the ends together at the ends of the arms? A traditional 300ohm twinlead FM folded dipole effectively forms a loop between the two terminals:

I use a standard twinlead-type antenna on my 70s Quad FM tuner (hidden behind a picture frame on the living room wall) and have no problems, but I'm in a city with decent signal strength.

Hiss in stereo but not in mono is a symptom of a weak signal. The FM mono signal is a 'summed' L+R signal. The stereo 'difference' L-R that is used to extract the 2 channels from the L+R signal is transmitted in AM on a subcarrier of the FM signal (this allows for compatibility with mono-only tuners, which will cut off the AM subcarrier signal). Having to receive the AM subcarrier means that in stereo mode the tuner has to receive a wider bandwidth signal, which will pull in more noise as a result (and the AM subcarrier is more susceptible to noise than the FM signal too) - a rough guide is that you receive 20dB more noise in stereo mode, so you need 10 times more signal voltage to defeat that noise floor compared to mono only. 

Those circular folded dipoles aren't rated very highly by the radio buffs - if you are going for a 'hard' external or loft aerial, you would be better with a proper dipole. If you are in a weak signal area may need a directional multi-element yagi-type beam antenna pointed towards the transmitter you want to receive the best signal from,

[Sebastian Cobb]

Back when I was a teenager I used to get the pirates in brum with one of those twinleads tie-wrapped to a bamboo cane, wire out the window and the cane pushed up and trapped between the guttering and the house. Worked much better than the 'halo' bent di-pole my dad had on the roof, but I think it was a case of that being horizontally polarised and most pirates using vertical di-poles.

I also got my hand on a technics tuner from one of their semi-separate midi systems that could step by .025 mhz, which came in handy when try to tune in to drifty vfo's.

[Head Gardener]

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