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eHam Forums / DXing / RE: Yemen Activation?
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on: May 09, 2012, 01:31:01 PM
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It wasn't too hard to hear/work them from here on 80, but I do have an active vertical array for RX. Should be easy for you east-coast guys however  Tor N4OGW/5 (Mississippi) |
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65
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eHam Forums / DXing / RE: Yemen Activation?
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on: May 02, 2012, 06:05:29 AM
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It's a shame but N6PSE says long path isn't possible. That's a major disappointment for many of us west of the Mississippi. My work schedule is really going to cut into devoting much time to this one, oh well. At least it's not an ATNO.
Take a look at their QTH using the Google satellite map on QRZ.com. They have their QTH set on the North coast of the island in Hadiboh. Many don't set their QTH precisely but I'll bet these guys did. If they are in Hadiboh they are at the base of a mountain which is centered near Eerk and Jo'oh. They have a clean shot to the West but that mountain completely shuts off the LP. 73, Chris/NU1O That is not the problem with LP on the low bands: 7O6T's sunset is 1439z. At that time, the sun has already risen even in W6. You need common darkness for SP or LP on the low bands. Tor N4OGW |
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66
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eHam Forums / DXing / RE: Yemen Activation?
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on: May 01, 2012, 01:29:52 PM
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Fortunately I don't have to worry about 20 as I have 7O1AA on SSB and 7O1YGF on CW, both on 20. I think for the mid to far west only three bands are a realistic possibility, 20, 17 and 15. I could hear them OK on 15 last night, but they were louder (S5) on 17. I did manage a 17m CW QSO @ 0158. Unless conditions improve dramatically 10 and 12 are likely out of the question, although he is barely detectable on 12 as I type this at 1600. The lower bands look like a bust, as the grey line just doesn't work out...one end or the other is always in full daylight. He was very weak on 30 last night, and that was on a 3 element yagi. It's a shame but N6PSE says long path isn't possible. That's a major disappointment for many of us west of the Mississippi. My work schedule is really going to cut into devoting much time to this one, oh well. At least it's not an ATNO.
Yes, their sunrise is 0201z, so you don't have any common darkness with them. But I think you are within 10 minutes, so 40 should be easy and maybe even 80. Here in MS I do have 1+ hours of common darkness. They had an excellent signal on 80 last night and were working quite a few north american stations. Tor N4OGW/5 |
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eHam Forums / DXing / RE: Anyone ever go from an A3S to a 204BA?
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on: May 01, 2012, 06:59:19 AM
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The Force-12 antenna is twice the price of the 204BA. I did look at their specs - and they are 10 pounds lighter, which is a very good thing.
However, I did just find a Wilson M520 - which is a 5 element 40' boom 20M monoband antenna for $150.00
I'm actually thinking of purchasing it, removing the first director and boom leading up to it - re-tuning it using the gamma match.
But I need to find an online manual - do I can see what its weight is and what the spacing is. Its a crazy idea - but the worst thing that could happen is that I end up with enough aluminum to build several antennas - hi hi.
OK- anything used is of course going to give you much more antenna for the $. Cutting down a bigger monobander is also easy. But you will certainly have to retune all the elements, don't expect to just retune the gamma match and get good performance. Tor N4OGW/5 |
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eHam Forums / DXing / RE: Anyone ever go from an A3S to a 204BA?
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on: April 30, 2012, 06:59:03 PM
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Any specific reason you want a 204BA? I think there are better choices in monobanders- the 204BA is quite heavy for its size.
I have a pair of Force 12 EF-420's up and have been very happy with them. The boom length is a little more (30'), but they are less weight and wind load than the 204BA.
Tor
N4OGW/5
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70
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eHam Forums / Antennas and Towers and more / RE: Radial wire type
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on: April 22, 2012, 06:45:24 AM
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Get solid rather than stranded if you have a choice. When you need to fix a radial connection later on, it is MUCH easier later on to clean corrosion off of solid copper rather than stranded. It's usually cheaper than stranded as well.
Tor
N4OGW
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71
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eHam Forums / Antennas and Towers and more / RE: What wire array has worked for you?
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on: April 19, 2012, 06:41:27 AM
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Before I put up towers at my qth I used a lot of wire antennas in trees (lots of 100 ft pines here). One of my favorites for 20 and up was a 2 element delta quad. These had a number of advantages, not all electrical: -good gain and pattern for a 2 element design -can be supported by only two ropes. This is a major one- I also had a 2 element 40m quad up that required 4 ropes in trees, it was a nightmare to put up and keep up -it was configured with the triangles pointing down, feed at bottom. I used three pieces of lightweight PVC for booms. This is a very strong mechanical arrangement, and resists being flipped over in a storm better than a wire yagi. For 20 and up the boom is less than 10 ft. Below 20 the whole thing gets too heavy for 2-rope support. -can be designed with 50 ohm feed, no matching needed. I would often feed them with ladder or open wire line, and transition to coax on the ground under the antenna (use multiple of 1/2-waves of ladder line). One thing I found about making parasitic wire arrays: to get them to work I had to tune the elements carefully. Tubing yagis are easy to build and come out nearly exactly where modeling software predicts. But with wire antennas, the precise length of an element is very hard to model. Small differences in wire size and how the insulators are attached are enough to throw off a parasitic design. See for example the very precise instructions for the spiderbeams. For the quads I made all elements exactly the same size and used an antenna analyzer to set the required resonant frequency from the model exactly. Then to get reflector elements I added a tuning stub. But if you can put up a tower, do it. Conventional yagis are much much much easier to build and maintain Tor N4OGW |
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73
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eHam Forums / Computers And Software / RE: Decoding multiple Morse code signals automatically on a noisy RF band
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on: April 17, 2012, 06:27:02 AM
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Thanks Tor
I looked SO2SDR briefly and will install it during the weekend.
I did not find code for " spectrumProcessor" part, is that in one of the included libraries?
73 Mauri
Yes, that is where all the peak detection is. It is all in spectrum.h and spectrum.cpp. Look in the function "detectPeaks". Sorry, the code could be a lot clearer and better documented  I do something like this: 1) for each spectrum from the FFT, do some smoothing (a running average in frequency). Also average several recent spectra together in time. 2) look for peaks in the averaged spectrum, computing the center frequency. Store this in a list, along with the number of times this frequency has been found. 3) once a peak has been detected several times with the same (within some delta_frequency) center frequency, count it as an active "signal". Otherwise remove peaks after a certain time interval has elapsed. Keep active signals in the list for somewhat longer. #3 is important for distinguishing peaks from noise- otherwise it is easy to find peaks in a noisy band. But a CW signal will have a frequency that is constant. Tor N4OGW |
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74
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eHam Forums / Computers And Software / RE: Decoding multiple Morse code signals automatically on a noisy RF band
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on: April 16, 2012, 06:28:54 AM
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I do wide-band peak detection in my contest logging program SO2SDR. It has a skimmer-like bandmap display which does signal detection but not decoding. It is open source and you are welcome to look at what I did: http://code.google.com/p/so2sdr/I am not particularly interested in adding CW decode to my program as I don't want to operate in assisted classes in contests. But even without that, you can do some neat tricks once you detect all CW signals (or carriers): for example, you can easily compute the "best" open frequency to call cq on Tor N4OGW |
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eHam Forums / Antennas and Towers and more / RE: Best ways to accurate measure phasing line lengths ( and affordable) are..?
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on: April 16, 2012, 06:15:44 AM
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Two comments: 1. The way you described (tee to 50 ohms and 1/4-wave of coax) will produce a low SWR when the far end of the 1/4-wave is SHORTED. Did you short the far end? If you left it open, you are getting a multiple of a 1/2-wave. How long (in feet) are your two pieces? 2. There is a lot of recent mis-information about this phasing method. The 71/84 degree lengths are not magic lengths that match any two verticals. Those two lengths assume the impedance of your verticals is about 36 ohms. If the impedance is different you need different phasing lengths and will need to calculate them. ON4UN goes through the math. Or see: http://www.eznec.com/Amateur/Articles/index.html "The Simplest Phased array..." I think W7EL has a simple program on his site that will do the calculations. Tor N4OGW |
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