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long antenna

Started by RichD November 17, 2015
During my workout yesterday, I attached a 3 meter 
extension to the earphone cord of my radio, as I 
wanted to place it at a distance.
The cord is the antenna.

I was indoors, where the reception is usually crummy.  
I figured the longer line should improve performance, 
right?  No!  The reception was barely decipherable.

Can anyone explain the physics here?

--
Rich

On Tuesday, November 17, 2015 at 1:39:04 PM UTC-5, RichD wrote:
> During my workout yesterday, I attached a 3 meter > extension to the earphone cord of my radio, as I > wanted to place it at a distance. > The cord is the antenna. > > I was indoors, where the reception is usually crummy. > I figured the longer line should improve performance, > right? No! The reception was barely decipherable. > > Can anyone explain the physics here? > > -- > Rich
What frequency? Calculate the wavelength. George H.
On Tue, 17 Nov 2015, RichD wrote:

> During my workout yesterday, I attached a 3 meter > extension to the earphone cord of my radio, as I > wanted to place it at a distance. > The cord is the antenna. > > I was indoors, where the reception is usually crummy. > I figured the longer line should improve performance, > right? No! The reception was barely decipherable. > > Can anyone explain the physics here? >
Was this AM or FM? On AM (but the headphone cord isn't likely used for the antenna there), there is so much electronic noise in the average house now that making the antenna longer may just increase that noise. Getting the antenna near a window will bring in more signal and less of the noise. But it's like for the FM broadcast band. There may be issues with multipath distortion, rearranging the headphone wire may help. I once found a nice compact stereo system, but the "local" NPR station (which isn't local) was noisy. I figured a better antenna, but that didn't fix it. I removed the whip, and reception improved. So in that case, the radio was being overloaded by local stations, which got in the way of the weaker non-local station. But taking out the antenna meant a reduction in the strength of the local signals, while the non-local was still strong enough to come in, but no overloading from local signals. Michael
RichD wrote:
> > > During my workout yesterday, I attached a 3 meter=20 > extension to the earphone cord of my radio, as I=20 > wanted to place it at a distance. > The cord is the antenna. >=20 > I was indoors, where the reception is usually crummy. =20 > I figured the longer line should improve performance,=20 > right? No! The reception was barely decipherable. >=20 > Can anyone explain the physics here? >=20
** I assume you are trying to listen to local FM stations - right ?=20 The original earphone cord was matched to the radio's tuned circuits so tha= t the combination resonates at or near the middle of the FM band at about 1= 00MHz when used in the usual way. Adding extra extra length detuned that re= sonance to a lower frequency, outside the FM band.=20 In good signal conditions, this would hardly be noticed but in weak, indoor= conditions it was enough to put the resulting signal below the threshold o= f reception. IME radio signals behave as expected in outer space, with some predictabili= ty in free air and a line of sight but with no predictability indoors.=20 ... Phil=20
On Tue, 17 Nov 2015 10:38:58 -0800 (PST), RichD
<r_delaney2001@yahoo.com> wrote:

>During my workout yesterday, I attached a 3 meter >extension to the earphone cord of my radio, as I >wanted to place it at a distance. >The cord is the antenna. > >I was indoors, where the reception is usually crummy. >I figured the longer line should improve performance, >right? No! The reception was barely decipherable. > >Can anyone explain the physics here?
can explain but not here. has to do with reflections and standing waves. w.