Home |
Search |
Today's Posts |
|
#1
|
|||
|
|||
I got a good answer in mail:
"J" == Jerry writes: 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.? J It isn't the size but the voltage rating that matters. The point of the J capacitor is to protect the RF stage of your radio from the ringer signal of J the phone, which will be anywhere from 40 to 70 volts. Considering that J your radio may be sensitive to signals in the microvolt range, it isn't J surprising that 70 volts could be a radio killer. I'd use a cap of 200 volt J or more rating. There are a lot of different kinds of caps. A ceramic disk J would be appropriate and dirt cheap. Sure wish there would be that warning on that regular posting to rec.radio.info . Yes I emailed McFadden. Is .01uF critical or is there actually a range that is acceptable? J The point is to have it big enough to pass all the RF signals your J interested in, but not signals lower in frequency than you want. 0.01uf is J a standard value, but double or half that would be OK. Also the "RF connector" isn't clear. What are examples of this "radio frequency connector"? Perhaps just coax to alligator clip? J Just connect one end of the capacitor to the phone line and the other to J your radio. If your radio has a telescoping antenna, just clip it to that. 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? J You're making this too complicated. Just connect the capacitor to the J antenna. Any wire will do. Considering that the phone wire may be miles J long, whether or not you extend the telescoping antenna is probably J irrelevant. 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? J HF signals are rarely perfectly clear, no matter what the antenna. You J ought to hear more than you do with the telescoping antenna alone. 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? J If you have 4-wire phone, one of them will be ground, and that one certainly J will NOT work. The others are probably equal as antennas. Just try them J all. 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. J Probably means 50 volts. Not enough. The first time the phone rings will J damange this capacitor. A 1000-volt 0.01uF cap is only a quarter or so a J Radio Shack. Far from stores, I wonder if the necessary high voltage capacitor could be found in my pile of broken radios. I suppose I would look for meaty cylindrical types rather than pill shaped types. OK, will look. |
#2
|
|||
|
|||
Years ago before they started burying all the phone drops and cabling the
overhead wires, I connected my BC-348 to the phone withe a 0.005-uF disc ceramic capacitor. It gave me a VERY long wire, probabaly miles of long wire. Worked quite well. I haven't tried it since. 73 de Jack, K9CUN |
Reply |
Thread Tools | Search this Thread |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Forum | |||
Inverted ground plane antenna: compared with normal GP and low dipole. | Antenna | |||
Mobile Ant L match ? | Antenna | |||
EH Antenna Revisited | Antenna | |||
Poor quality low + High TV channels? How much dB in Preamp? | Antenna | |||
50 Ohms "Real Resistive" impedance a Misnomer? | Antenna |