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Old May 14th 04, 12:54 AM
Dan Jacobson
 
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Default Phone line as SW antenna

McFadden responds! Hope he can integrate some of this into that
periodic posting.

To: Dan Jacobson
From: Bill McFadden

http://www.rdrop.com/users/billmc/phone_antenna is built around
a ".01uF capacitor", but what kind? Are big .01uF capacitors better
than small ones etc.?


It doesn't matter much, but a ceramic capacitor is probably going to be the
best (and cheapest). A voltage rating 250V or higher would be good since
the ringing voltage on a phone line is around 90 V RMS.

Is .01uF critical or is there actually a range that is acceptable?


The value isn't critical. Anything within a factor of 3 (.0033uf to .033
uF) should be okay.

Also the "RF connector" isn't clear. What are examples of this "radio
frequency connector"?


The RF connector is whatever kind of plug fits the antenna input on your
receiver.

Perhaps just coax to alligator clip?


That's how I made the first one. It was one clip lead from the phone line
to the capacitor, and another clip lead from the capacitor to the whip
antenna. Worked okay.

Is the 50 ohm coax critical? How about a plain wire from the capacitor
to the radio's telescoping antenna? Should the telescoping antenna
still be extended, or retracted?


You only need coax if you're feeding the coax antenna input on the
receiver. You can use the whip antenna, which doesn't matter whether it's
up or down. If you get a lot of interference from nearby broadcast
stations, you'll need to use coax and one of the filters in the article.
50 ohm coax isn't critical. 75 ohm coax (TV coax) is often cheaper and
better shielded.

How do we know if our phone line antenna is working properly? Should
time signals on 5000, 10000 khz etc. jump out in perfect clarity?


You should get stronger signals than you would with the whip antenna alone.
If the signal level drops when you disconnect it, then it's working.

Certainly there must be a slight advantage between one of red and
green vs. the other... or might we not even bother comparing, as they
are certain to be the same?


I didn't notice any difference, but it was easy to try both.

By the way, I found a .01uF capacitor that the capacitor numbers web pages
don't seem to decode: 103K PE50. I can't figure out what the PE50 or
PE5Q means.


50 is probably the voltage rating (50V). PE may refer to the dielectric
material, but I don't recognize it.

Lastly, the article has some spelling mistakes, e.g., lightening arrestors.


Fixed.
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