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#21
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MII - Thank You Very Much for this Link / URL ~ RHF
.. .. WHAT -?- "RF BALUNs" - by Harry Lythall [SM0VPO] .. BALUN = http://web.telia.com/~u85920178/antennas/balun0.htm .. WHY -?- Should "I" Read this WebPage / Check-Out this Link URL ? .. READ = http://web.telia.com/~u85920178/antennas/balun0.htm .. Elemination of Radiation from the Feeder Cable .. Makes the Antenna Radiation Pattern Predictable. .. Dramatically Reduces QRM, TVI to neighbours. .. Helps to Keep RF Out of the Shack. .. CHECK-OUT = http://web.telia.com/~u85920178/antennas/balun0.htm .. .. |
#22
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Mark Zenier wrote:
Somebody posted the schematic here in the newsgroup a few months back. Interestingly simple set. It's got a tuned dual FET cascode RF amplifier. So a preselector or pre-amp won't benefit it too much. Why do you think the first RF circuit in the DX-160 precludes using a passive preselector? |
#23
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In article , starman wrote:
Mark Zenier wrote: Somebody posted the schematic here in the newsgroup a few months back. Interestingly simple set. It's got a tuned dual FET cascode RF amplifier. So a preselector or pre-amp won't benefit it too much. Why do you think the first RF circuit in the DX-160 precludes using a passive preselector? Because there are two tuned circuits, each using a segment of the main capacitor gang, (the input transformer, and the output of the amplifier). Both are feeding the gates of FET amplifiers, so are (or have the possiblity of being) high impedance and therefore high Q. The fact that there's an "antenna trim" control, (which really usually compensates for mistracking of the two tuned circuits) indicates that they're pretty sharp, at least for an LC tuned circuit. Likewise, the bandspread capacitor is two sections, one in parallel with the main oscillator tuning, the other in parallel with the RF amp output tuning cap. So the Q must make the bandwidth narrower than the 1/2 MHz or so that, (as I remember), the bandspread covers. Mark Zenier Washington State resident |
#24
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RHF wrote:
MII - Thank You Very Much for this Link .....blush... mike |
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