Radio reception on bike

E Willson said:

To most serious cyclists this may seem like blasphemy but I would like
to listen to a radio on my daily trip. I have tried several portable
radios, but none can keep a constant volume as the bike changes
direction. It seems that the antennas are very directional, so that when
the bike changes direction the signal strength changes drastically. This
is true on either AM or FM. Any info on how to setup a radio so that the
signal strength is adequate and uniform would be appreciated.

Thanks,
EJ in NJ

Hi again EJ (in NJ)!

I work in a power station which is very noisy(electrically speaking). I
came up with a design where a long length of wire (the antenna) is
connected to the inner core of coaxial cable which is fed down through
the roof to the radio on my work bench. The coax isn't connected
directly to the radio but to a loop about 150mm in diameter (6 inches to
you guys). The other end of the loop is connected to the outer braid of
the coax. The loop is about 8 turns of wire.
The coax braiding at the antenna end is left unconnected.

What the loop does is it re-radiates the radio signal to the ferrite rod
inside your AM radio. It has to be up against the side of the radio,
you'll have to experiment a bit to find the best spot. (If you look
inside an AM radio you'll see a dark rod about 3 inches long with a fine
coil around it, that's the part that actually picks up the radio waves.)

In your case you may not be able to run a long enough wire as the
antenna, and it would have to be vertical to be omni-directional (works
in all directions), however I think it's a good design to start your
experiments with.

My boss heard about my antenna design and rang me up and got me to
install one to his office so he could listen to the fottball and
cricket. He was very pleased.

I have an amatuer radio license.

Marty
VK6ABC

It's not just the antenna's fault. Signals in a city propagate like
light in a maze. They are impeded by buildings, but at some
frequencies refract around buildings. Since many signals bounce off
of buildings and other structures, they occasionally interfere causing
"null spots" or "fast fades". There is also ground-effect attenuation
(ground interference from ground reflections) which can severely
reduce a signal.

Your best bet is probably to find a channel at the lowest frequency
possible, like AM 580 because lower frequencies can go around corners
more easily.

Mount the antenna as high as you can (e.g. consider buying headphones
with a built-in AM radio.) Most low-cost antennas are polarized
dipoles which means they favor signals coming from the horizon, and
are much less sensitive to signals from space or from the ground.
This means that once you have pointed the antenna STRAIGHT UP, you
should try to avoid tilting your head because this will cause an
immediate loss in signal strength. Alternately, you might get an
antenna that is less polarized but I don't know where you could find
such an antenna and you would need a better receiver.

Finally, make sure to find a radio with ALC, or automatic level
control. circuitry tries to keep the volume at the same level on a
constant basis. This might be helpful for pure attenuation fades, but
would not be useful for nulls or shadowing fades.

- Don Gillies
San Diego, CA

front end of the

E Willson said:

To most serious cyclists this may seem like blasphemy but I would like
to listen to a radio on my daily trip. I have tried several portable
radios, but none can keep a constant volume as the bike changes
direction. It seems that the antennas are very directional, so that when
the bike changes direction the signal strength changes drastically. This
is true on either AM or FM. Any info on how to setup a radio so that the
signal strength is adequate and uniform would be appreciated.

Quoted message said:

Thanks,
EJ in NJ

On Wed, 19 Oct 2005 16:21:30 -0400, E Willson <[email hidden]>

Quoted message said:

direction. It seems that the antennas are very directional, so that when
the bike changes direction the signal strength changes drastically. This

I use a pocket radio, with headphones, at a sound level that naturally
still allows me to hear the road noises around me.

My point is, the headphones cord work as an antenna - longer that an
outer antenna of the kind of radio you seem to be using, and bouncing
around to all directions :-)

Of course, some radios are better than others ;-) If you use a digital
type one, ounce you lose a frequency, you can either chose another
memorized station, or have the radio scan the nearest receiveable
frequency.

Good luck,
JBR

BigBen said:

On Wed, 19 Oct 2005 16:21:30 -0400, E Willson <[email hidden]>

Quoted message said:

direction. It seems that the antennas are very directional, so that when
the bike changes direction the signal strength changes drastically. This

I use a pocket radio, with headphones, at a sound level that naturally
still allows me to hear the road noises around me.

My point is, the headphones cord work as an antenna - longer that an
outer antenna of the kind of radio you seem to be using, and bouncing
around to all directions :-)

Of course, some radios are better than others ;-) If you use a digital
type one, ounce you lose a frequency, you can either chose another
memorized station, or have the radio scan the nearest receiveable
frequency.

Good luck,
JBR

On FM radio the headphone wires are sometimes used as an antenna but for
AM a ferrite rod is used. Correct antenna length is related to the radio
wave length. For FM radio the wavelength is a few metres, for AM radio
it is one or two hundred metres. AM radios rarely, if ever, use the
headphones as part of the antenna. The ferrite rod has special magnetic
properties that focus the radio waves, a bit like a lens concentrating
light onto a single point. I sympathies with you, my favorite station is
also AM.

Marty

the $20 Sony headset at walmort is excellent in swfl but swfl's fm
spectrum is not jammed and the land is flat with "urban areas" over the
horizon from each other. wear a headband over the loops.

Marty,

I have some coax from my TV installation, and my CB days. I think I
understand the arrangement. I'll try it.

Thanks,
EJ in NJ

Marty said:

E Willson said:

To most serious cyclists this may seem like blasphemy but I would like
to listen to a radio on my daily trip. I have tried several portable
radios, but none can keep a constant volume as the bike changes
direction. It seems that the antennas are very directional, so that
when the bike changes direction the signal strength changes
drastically. This is true on either AM or FM. Any info on how to setup
a radio so that the signal strength is adequate and uniform would be
appreciated.

Thanks,
EJ in NJ

Hi again EJ (in NJ)!

I work in a power station which is very noisy(electrically speaking). I
came up with a design where a long length of wire (the antenna) is
connected to the inner core of coaxial cable which is fed down through
the roof to the radio on my work bench. The coax isn't connected
directly to the radio but to a loop about 150mm in diameter (6 inches to
you guys). The other end of the loop is connected to the outer braid of
the coax. The loop is about 8 turns of wire.
The coax braiding at the antenna end is left unconnected.

What the loop does is it re-radiates the radio signal to the ferrite rod
inside your AM radio. It has to be up against the side of the radio,
you'll have to experiment a bit to find the best spot. (If you look
inside an AM radio you'll see a dark rod about 3 inches long with a fine
coil around it, that's the part that actually picks up the radio waves.)

In your case you may not be able to run a long enough wire as the
antenna, and it would have to be vertical to be omni-directional (works
in all directions), however I think it's a good design to start your
experiments with.

My boss heard about my antenna design and rang me up and got me to
install one to his office so he could listen to the fottball and
cricket. He was very pleased.

I have an amatuer radio license.

Marty
VK6ABC