Re: Digest Number 1053
Dave Martindale <[email protected]> Mon, 20 Sep 2004 09:30:59 -0700
| Newsgroups | gmane.recreation.radio.hardware.icomr2 |
|---|---|
| Message-ID | <[email protected]> |
>Thanks for the reply, Dave. This is great info. Could you clarify what you mean by "If there's nothing but coax between the antenna and the scanner" You mean other devices? Splitters?
Splitters, amplifiers, filters, anything but coax, since these devices may
pass only a certain frequency range, or pass signal only in one direction,
or pass nothing at all unless supplied with power.
>Also, I wanted to ask one more question and that is: Can you also use the pre-wire house coax to bring in signal from a random or long wire copper antenna for sortwave?
>
>The ICr2 covers shortwave and I wonder if the signal could be brought up cleanly into the house that way.
You can try it, but it may attenuate the signal. The antennas normally used
for VHF and UHF are low-impedance designs with a feedpoint impedance
somewhere near the 75 ohms of the cable, so they will couple signal nicely
into the cable and the cable will carry the signal with relatively low loss.
But HF antennas are usually a "long wire" that's only a tiny fraction of a
wavelength, which provides a high-impedance signal. This won't couple into
a piece of coax very well, and the coax will act like a capacitor to ground
attached to one end of the antenna (unless you use an antenna tuner between
antenna and coax). If the coax length is short compared to the antenna
length, this may not matter much, but a long coax run is likely to be a
problem.
Dave
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