Longwave and longer antennas

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Alain

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Hello All!

It would interest me no end if everyone who is receiving longwave to kindly post just what type of antennas you are using! I'd assume that some are using a beverage of some sort?

Even if you do not listen to longwave, post what type of antenna and feedline you use please, and any other particulars you'd care to share...

I have the Willco board installed in my ICOM R 71-A and my frequency display tunes down to 0.008.5khz. I have a 75' copper wire "loop" that I have hung in the rafters of the garage. I have a 10' stretch of Belden #8267, RG 213/U that ties from the antenna into the 71-A.

I usually hear some buzzing and clicking sounds but I am never sure as to just what I am listening to. Am I just hearing QRM/N? What should I be listening for?

Is there a good website or a book that I could purchase to learn more about the "history and the mystery" of this often neglected area of the radio spectrum?

Alain...WPE2OLR Newark [New Jersey] Radio Club, circa 1962
 

ka3jjz

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Alain, far and away the best place for LW information is the well known Longwave Club of America. They have a nice website, which I see has been just updated, here...

http://www.lwca.org/

73s Mike
 

k9rzz

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The BEST antenna I've ever used from home on longwave was the "EWE" antenna. A Google search will give more information than I could type here ... they are relatively small and work GREAT. That's the only antenna I've ever heard any of the longwave broadcasters on (Iceland, Germany, and Algeria). Mine was 15 ft high by 75 feet long (that's just where it fit easiest, not any magic number). If you have the room, try a "BOG" (beverage on ground), 300 ft or longer. Many people have had good luck with small loops + pre-amp because you can null local noise.

That R71a of yours is an excellent radio for longwave, that's what I primarily use as well.

The secret to longwave listening is finding the antenna that gives you the lowest noise, then the band comes alive with aeronautical non-directional beacons (NDB's), DGPS stations (give GPS receivers more accuracy), international broadcasters (easier if you live on one of the coasts, tuff here in the midwest), and some of the time stations WAY low in frequency (WWVH is easy).

Right now with my Palstar R30 and 100 ft longwire at 5pm I can hear the closest DGPS station on 297khz S9+ (about 8 miles away at the Milwaukee Coast Guard station) (HEY! There's a new one on there on 303khz S9+ ... never heard THAT one before!) and about a dozen airport NDB's from local airports within 100 miles or so.

More questions? Bring 'em on, I love listening to longwave.

John K9RZZ
Milwaukee
 

prcguy

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Unless you have a lot of land in the country, I think this active whip will give you the best bang for the buck. The folks that designed it were trying for transatlantic VLF contacts and this was about the best thing they could come up with. It will give you excellent performance on VLF through 30MHz and is extremely overload proof. The $500+ Dressler’s don’t even come close and you can assemble one for around $75 or less if you have some of the common parts. I built one and am thrilled with it. See http://www.arrl.org/tis/info/pdf/0109031.pdf and
http://www.amrad.org/projects/lf/actant/
prcguy
 

ReceiverBeaver

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I'm with LarrySC,

A big loop, a very common size and shape being a square one for 80 meters (about 75 feet per side) is also an all-in-one HF receiving antenna even down to LF freqs. Ridiculously easy design and construction. They tend to be very quiet as they're current-point type antennas and because of their loop-around configuration,...hence their name, they also tend to be omnidirectional whereas a longwire will directional off the end. I pity the fool who doesn't use a big horizontal loop. :)
 

k9rzz

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I've heard rave reviews about the horizontal loop, but if it's close to the ground then it's a cloud burner ... most sensitive to high angle sigs, or close in stations (if that's your gig). I had a 40 meter loop mounted vertically and fed on one of the sides. That was a great DX antenna because of the low angle of radiation (and reception).

Small loops may work well, but you need a hot pre-amp behind them.

It all depends upon what you're trying to hear. Of course, you can never have too many antennas, build one of each and switch back and forth!


John K9RZZ
 

kb2vxa

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Hi Alain and all,

I see that some of these guys are a bit confused as to which portion of the spectrum they're listening to. There are many long wave clubs and web sites around the world, you'll get the best info from the highly experienced and more technically oriented.

I see you're confused, shift the decimal and you'll see your display reading out 8.5Hz which is about as close to DC as you can get. Guaranteed your receiver isn't actually receiving, you simply unlocked the PLL circuit and it's way up the dial somewhere else.

Unless you're using one monster of a tuning capacitor your loop is resonating WAY too high, it lacks the inductance to tune down that low. I have used small untuned loops for MW and they work, the signals aren't as strong but it saves the trouble of fiddling with large, multi gang variable capacitors. I just might suggest you run a wire a couple of feet above ground around the property line and if need be you can go around several times if you live on a postage stamp lot. That low it shouldn't pick up much static, hams often use smaller versions or long wires close to the ground for receiving the lower frequency HF bands for that reason. Never mind the NVIS or "cloud burner", you're not transmitting and the lower signal level is preferable to tons of static, the signal to noise ratio is far more important. Then too you're not listening to HF, LF is all ground wave so that point is rather moot.

Then too you could always put up a 200' tall base loaded umbrella antenna but your neighbors would kill you for covering the whole block like a copper spider gone mad. (;->)
 
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prcguy

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I still say an active E-field antenna like the AMRAD kit is probably the best VLF/HF (especially VLF) antenna anyone will own unless you have lots of wire and an RF quiet space to put it. You can place the small active antenna away from noise sources, which is not always possible with long lengths of wire. Bringing wire antennas to the receiver is also a challenge with avoiding noise generating consumer electronics and computers along the way. Use coax to bring wire antennas inside and you create another problem with matching. The AMRAD design matches to coax and is shielded all the way to the radio. This antenna is not to be confused with active units from Sony, McKay Dymek, Dressler, etc, it’s in a completely different league.
prcguy
 

gcgrotz

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If I remember my propagation stuff correctly, freqs in the LF band are mostly ground wave and there would be no "NVIS effect" from ionospheric propagation. This is why a wire stretched out on a beach works so well, and large LF loops are ground mounted. I hear the flag and pennant type antennas work very well too.

pcrguy: I have wondered about that active whip from QST you referred to. I've been curious about that type antenna in general. You know a typical AM car radio is exactly that - a very short high impedance whip coupled to the RX with a low gain transistor stage that mostly isolates the antenna from the RX front end and provides an impedance transformation. If you have any more thoughts on that active whip I'd love to hear them.
 

prcguy

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gcgrots,
Your description is exactly right, it’s a short whip that uses a whopper of a FET to match the very high impedance short whip at VLF (2 meg ohm at 10KHz). The QST article mentions an important fact that all LF antenna experimenters should consider. The example of a 1M long whip used at 10KHz directly into 50ohm coax would result in an immediate 114dB loss of signal due to the extreme mismatch. Even longer wires or whips at higher frequencies that are still extremely short in wavelengths can experience very high losses when fed with 50 ohm coax due to these mismatches. That’s why AM car antennas use that bizarre high impedance coax with a hair sized center conductor. The designers of the AMRAD antenna also went to great lengths to find a power transformer that sufficiently isolates the line from the secondary to keep line induced noise out of the receive system. I originally made one of these antennas for my Harris RF-590A and it was a fantastic combination. I did find cheaper receivers like a Yaesu VR-5000 will lay over and die from BCB overload when fed by the AMRAD antenna.
prcguy
gcgrotz said:
If I remember my propagation stuff correctly, freqs in the LF band are mostly ground wave and there would be no "NVIS effect" from ionospheric propagation. This is why a wire stretched out on a beach works so well, and large LF loops are ground mounted. I hear the flag and pennant type antennas work very well too.

pcrguy: I have wondered about that active whip from QST you referred to. I've been curious about that type antenna in general. You know a typical AM car radio is exactly that - a very short high impedance whip coupled to the RX with a low gain transistor stage that mostly isolates the antenna from the RX front end and provides an impedance transformation. If you have any more thoughts on that active whip I'd love to hear them.
 
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