"ellisc" wrote in message
m...
I have an 80s model delco am/fm radio. I'd like to attach an external
long wire AM antenna, an external FM antenna, and rig something up so
I can listen to it with headphones at bedside.

Questions:


Depending on the frondend design... Early AM car radios included the
antenna feedline capacitance as part of the tuned circuit; and included
a trimmer to fine tune the radio tracking to match the antenna. The
antenna was connected to a very high impedance point of the RF
stage tank.

Later designs used aperiodic frontends, and were less critical. You
might loss ground using a long antenna on the set, depending on its
vintage.

pete

On 6 Feb 2004 10:25:58 -0800, (ellisc) wrote:

I have an 80s model delco am/fm radio. I'd like to attach an external
long wire AM antenna, an external FM antenna, and rig something up so
I can listen to it with headphones at bedside.

Questions:

1. What do I need to do/build the headphone connection? Can I put
something together using the car radio speaker wires?

Get a 1/8" stereo jack from RS or wherever. Use a 100 ohm resistor
between left and right speaker outputs and the jack. Too loud? Try a
higher value. Not loud enough? Try a lower value. Resistors are
cheap.

2. Is it possible to hook up the long wire antenna without getting too
complicated? Can I use the antenna plug on the radio in some way, or
will I have to get inside the box? I don't know a lot about
electronics. I have a soldering iron and have fixed the occasional
loose wire on things around the house, but not much more than that.

For normal use just put a 5 foot length of wire on it. That should
work for FM, too. It's not much different than what was on the car.

If you want to listen to distant stations a different antenna is
needed for AM and FM. I used a tuned loop antenna with a shielded
pickup loop on a mid-80's Dodge radio and it worked great. It was
selective enough to bring in stations adjacent to a nearby 50,000 watt
clear channel station (WHAM 1180, Rochester, NY).

Anyway, try it out. It will cost a buck or two and you will learn
something in the process.

Good luck,
Jim

CDE,

ANTENNA:
You could try building a 'Low Noise' AM Antenna that can
start at near ground level and going up to as far as you
can get it and then out as far as your can make it.
NOTE: This is usually called an Inverted "L" Antenna.
* First install a Ground Rod and a short Heavy Ground
Wire at the Base / Starting Point of the Antenna.
* The Antenna Element was 100 Feet of Landscape Lighting
Cable (Heavy Duty Outdoors Zip Cord).
* Affixed the Two Wires of the Near-Feed-End of the
Antenna Element across a TV 300 Ohm Matching Transformer
and connected them one-to-one.
* Secure the The Near-Feed-End of the Antenna Element and
Matching Transformer using insulators to the Ground Rod.
* Stripped and Twisted Together the Wires of the Far-End
of the Antenna Element and covered them with electrical tape.
* Ran/Routed the Antenna Element from the Ground level
up to the Top of the First / Near Antenna Support.
* Ran/Routed the Antenna Element from the Top of the First /
Near Antenna Support to the Top of the Far Antenna Support.
* Attach 50Ft to 100Ft of 75 Ohm Coax Cable to the other
end of the Mounting Transformer.
* Attached a short Heavy Ground Wire to the 75 Ohm Side
of the Mounting Transformer.
* Ran/routed the Coax Cable from the the Antenna Element
to the your Car Radio's location.
* Terminate the 75 Ohm Coax Cable with an Motorola Connector.
* Plug the Motorola Connector into the Car Radio.
TBL: The Antenna Element is a "Flat-Thin-Loop" that is
Physically 100 Ft Long and Electrically 200 Ft Out-and-Back.

ALTERNATE: To the Random Wire Antenna is to use a CB 104"
Stainless Steel Whip Antenna mounted on a piece of 21Ft Top Rail.
* A proper Antenna Insulated "Mount" is required to be used
between the Whip and the Top Rail.
* Use a 75 Ohm Coax Cable from the the Antenna to the Radio.
* Connect the Center Wire of the Coax Cable to the Whip
Antenna Element and the Outer Shield to the Top Rail.
* Terminated the Coax Cable with a Motorola Plug.
* The Base (Butt-End)) of this piece of Top Rail should be
3Ft-5Ft in the Ground and allow the Top Rail to be Free Standing.
NOTE: The Top Rail is your Antenna and Car Radio Ground.


STEREO HEADPHONES:
NOTE: Since your did not ask about Hooking-Up a Pair of
Stereo Speakers. I assume you know how.

The simplest method of making the connection between the
Car Radio's audio power amplifier Stereo Output and your
Stereo Headphones is using a pair of Dropping Resisitors
with a 1/8" or 1/4" Stereo Jack to match-up with your
Headphones and Two Dropping Resisitors.
THE HOOK-UP: The Barrel of the Stereo Jack is Ground;
Center-Section is the Left-Side Stereo Sound; and the
Tip is Right-Side Stereo Sound. For the Center-Section
and the Tip use an Equal Value Dropping Resistor.
Here is a suggested 'value' of Dropping Resistors for
different basic Headphone Impedances:
* 4 Ohms Headphones = One 43 Ohm One Watt Resistor per Side.
* 8 Ohms Headphones = One 82 Ohm One Watt Resistor per Side.
* 16 Ohms Headphones = One 160 Ohm One Watt Resistor per Side.
* 32 Ohms Headphones = One 330 Ohm One Watt Resistor per Side.


iane ~ RHF
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= = = (ellisc)
= = = wrote in message om...

I have an 80s model delco am/fm radio.
I'd like to attach an external long wire AM antenna,
an external FM antenna, and rig something up so I can
listen to it with headphones at bedside.

Questions:

1. What do I need to do/build the headphone connection?
Can I put something together using the car radio speaker wires?

2. Is it possible to hook up the long wire antenna without
getting too complicated?
Can I use the antenna plug on the radio in some way, or
will I have to get inside the box?
I don't know a lot about electronics. I have a soldering
iron and have fixed the occasional loose wire on things
around the house, but not much more than that.

Or should I just forget it and buy a portable receiver?
I mainly want to listen to AM talk at night and a
particular FM college station in the next town.
I read on several posts about using a car radio because
of the AM reception.

I've also thought about buying a used Grundig receiver,
in particular the S350. I think having the option of
listening to shortwave might be fun. Does this thing
put out good audio via headphones?

Thanks.

..