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HF/MW/LW General Discussion General discussion on monitoring the HF (High Frequency), MW (Medium Wave), and LW (Long Wave) spectrum (0.5 - 30 MHz)

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Old 01-12-2006, 10:44 PM
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Default Longwire Antenna

I just set up a longwire antenna, and so far it's working great. I was just wondering, should the wire be horizontal from point to point, or can it slope? which way works best?
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Old 01-13-2006, 12:03 AM
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Sloping should not be a problem, even bending around a curve like an L is ok if you don't have room for a continuous straight run.
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Old 01-13-2006, 12:05 AM
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It won't make any noticable difference. I have an antenna wire that goes up through my kitchen cabinet to the ceiling and around the room to a window, and I never had any problems with it...
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Old 01-13-2006, 12:54 PM
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The slope will not be a big deal, and as noted above you can make a "L" if needed to give you more length.

Jay
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Old 01-15-2006, 1:05 PM
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Default 2 Longwire Antennas?

I'll just ask this question in the same post since it's related to longwires. My radio has a external antenna port on the side, if I had two longwires for two different bands, could i splice the wires and tie them both into the external antenna port of my radio? would that work? or would it just create more interference? thanks again in advance guys!
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Old 01-15-2006, 9:38 PM
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That depends on the reciever(s) you are using.
Some portables, and even some desktop high end receivers can be overloaded with intermod and phantom sigs
I have 2 IC-R75's an IC-71A as well as a JRC-NRD 525.
I have a 70' sloper random wire fed with a 9:1 transformer.
The other one is a 250' Random wire fed with the same type transformer ( balun, Unin , whatever )
With out impediance matchers ( such as the MFJ- 959C) and a a pair of preselectors , I can knock out the intermod and hets right down to 70khz. ( of course the external DSP filters help )
I have found that using the best 50-75 OHM coax running to the shack works best.
Then there's the RF ground and Lightning, ( static bleed off units ) inline also.
Alot to consider if you really want to get serious about LW-HF, and the full spectrum of radio.
This does'nt include the VHF/UHF antenna configs I have up now.
Pick the best receivers, do the research on the best antenna setup suitable for your QTH, and start thinking of a plan ( after you research all you can ) on lightning protection, etc. If you're are really serious about the best installation you can get at your location, the time and research will pay off in the end.

Hope this helps..........
Regards,
K.R.
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Old 01-16-2006, 3:32 PM
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Hi guys,

To put it simply, a longwire is just that, a long wire. Usually it's a random length as long as practical and it doesn't matter how you arrange it as long as most of it is as high as practical. It requires no lead-in, it in itself is connected to the receiver which must be grounded as it works against ground as a countrpoise.

There's an awful lot to be said about antennas so please don't confuse the poor guy with an overabundance of details that have little to nothing to do with listening to the shortwave bands.

CSL, just to nip this in the bud there is no such thing as a long wire for a specific band. It receives all MW and SW bands equally well, it's not tuned in any way. Take one down and find something else to do with the wire like adding to the one you don't take down if you don't think it's long enough already, but usually 100' or so is enough.

Now if you lay out a half mile or more in one direction you'll have a Beverage antenna but that's a horse of a different color altogether and my horns are showing. (;->)
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Old 01-16-2006, 3:42 PM
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I played with longwires for awhile and I found my best friend to be an antenna tuner. I got a MFJ antenna tuner at a local ham fest for 60 bucks and using the chart in the manual, tuned it to the coresponding bands. Worked much better than the longwire alone because you can tune the wire to resonance and capture more of the signal.

You can find them cheap on EBAy too.
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Old 01-16-2006, 4:11 PM
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Hey guys,
It seems that Warren and I will continue to disagree about the "lead in " theory.
Jason, the antenna tuner you use does not make a random wire antenna " resonate" on any frequency.
It only helps to lower ( or match ) the input impediance of your receiver. ( would you agree, Warren? )
Regards,
K.R.
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Old 01-19-2006, 10:42 PM
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Hi Ringkirk and ring readers,

Yup, an "antenna tuner" doesn't tune anything, rather it fools a solid state transmitter into thinking it's looking into a 50 ohm load for which it's designed resulting in maximum power transfer. The old "boat anchor" tube type transmitters employed a tunable pi network output circuit which would load anything from about 25 to 600 ohms. In any case a tuner does nothing for a receiver besides introduce signal loss and may severely attenuate signals outside it's range eg. the Amateur bands.

Now if you want to tune in shortwave more effectively you may use a preselector. These babies have tunable amplifiers (some with variable gain) that "pre select" a somewhat narrow range of frequencies and amplify them a bit while tuning out everything else. I don't need to go into more detail, you can see the obvious advantages.

K.R., early radio antennas, most notably those for crystal sets used "lead in" wires which were simply insulated wires that connected the bare antenna wire to the antenna input terminal of the radio. As you can see it's simply a radio term, later twinlead was commonly referred to as TV lead in wire because it leads in the signal. When you work behind the counter you have to tactfully talk down to non technical people in such a way that they understand and don't think you're calling them idiots. At Rat Shack the situation is often reversed or equally idiotic and comically chaotic.

Historical note;
In the early days of Amateur wireless nothing was known about SWR and antennas were random length wires for the most part so the tuning unit was simply adjusted for maximum antenna current. Often a light bulb was used during initial adjustments and when it reached maximum brightness it was shunted out of circuit. Coax? Never heard of the stuff, transmission line was paralell open wire strung up the wall and across the ceiling much like the knob and tube electrical wiring of the day. Ladder line? Well, sort of but not quite, check out some really old houses, Edison's labs or pay attention to wires on ceramic insulators leading to surface mounted light switches in old WW2 movies. That's how they wired castles along the Rhine, you can't wire inside stone walls. (;->)

Hysterical note;
What is "impediance"? (;->)
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