Crystal radio question

[radio nut]

Hello, i built one of those cheap 80's crystal radio kits. It picks up my 2 local stations decently. I am only using 15 feet of wire. If i add more wire the volume goes down. Why is that? I thought the more antennae the better.

[old_tv_nut]

Don't know, maybe it's the stray capacitance of the wire?

How is the wire arranged physically?
Do you have a good ground for the set?

[radio nut]

The ant. wire just goes up and to the left around tools on the peg board and then down towards the floor. For a crystal set does it matter which way the diode points? The instructions aren't clear on that.

[radio nut]

Ground...gies to the breaker box...
Then that goes to ground.

[old_tv_nut]

Ground sounds OK.

Not sure what to suggest about the antenna except maybe running it as straight as possible without bending back. When I had a crystal set as a kid in Chicago I threw the antenna wire out the upstairs window and into a tree. It was mostly horizontal and maybe 20 feet long and got a few Chicago stations.

Diode direction should be immaterial, just changes the phase of the audio by 180 degrees.

[old_tv_nut]

Just had a thought - how long is the ground wire? Does the ground wire run in the opposite direction from the antenna or more or less the same direction?

[radio nut]

Ground wire 18 inches, and same direction as ant wire

[old_tv_nut]

I don't think one that short could be a problem - out of ideas for now.

[Dude111]

Hmm maybe adding longer antenna changes how it recieves??

Is the volume lowering OR is the station not being picked up as strong? (That would make voluime seem to go down also)

[old_tv_nut]

Originally Posted by Dude111

Hmm maybe adding longer antenna changes how it recieves??

Is the volume lowering OR is the station not being picked up as strong? (That would make voluime seem to go down also)

Did you read the first post? He said using a longer antenna changes reception.

In a crystal set, the volume is entirely dependent on the received signal strength. It's not either/or.

[old_tv_nut]

More questions:
When you lengthen the antenna, do you have to retune the station?
What is the tuning mechanism? Variable coil length or variable capacitor?
Can you post a schematic?

[radio nut]

If i lengthen the ant the volume gets weaker and does seem to move on the coil. This is tuned by changing coil length. Could a very cold environment affect the earphone? It is 20 here and this is in my garage.

[old_tv_nut]

Originally Posted by radio nut

If i lengthen the ant the volume gets weaker and does seem to move on the coil. This is tuned by changing coil length. Could a very cold environment affect the earphone? It is 20 here and this is in my garage.

Doubt the temp has much to do with the efficiency unless it affects the diode somehow? Even if it did, it would not account for the difference with antenna length.

You can email me the schematic and I'll post it.

wayne bretl "at" cox "dot" net (no space in name)

[radio nut]

I cant get the diagram pic to load correctly

[radio nut]

My camera's pictures are too big file size....wise to load here.