K7C已在归途上----学习一下 [复制链接]

以下内容是k7c网站上，10月1号的公告，中间有不少技术知识，不妨细细品味一下。

http://www.cordell.org/htdocs/kure/kure_pages/kure_news.html

k7c bulletin - oct 1st

this is a short information bulletin to our dxer friends around the world. we want you to know that we have heard your concerns regarding qsos with dxers in europe and other places on the other side of the polar path. we've all been in your situation, so we have empathy for you.

let's start with a technical consideration of which you should be aware. as you already know, we are using vertically-polarized antennas very, very close to salt water and with large radial fields. this makes our signal launch angle very, very low - quite a bit lower than most horizontally-polarized antennas on dry land. as a result, the k7c signal has been reported to be very loud on the receiving end. this doesn't mean, however, that you are just as loud here. all it takes is a couple of extra "hops" from a higher launch angle and your signal will change from an easy-to-work s5 to being undetectable. the k7c team has observed a number of occasions when it is obvious that you can hear k7c easily, but on our end the pileup is only an unworkable s-1 grumble. this is most pronounced at the beginning and end of an opening so you may be hearing us long before or after we can hear you. marginal openings on the paths to europe, the middle east and northern africa may be entirely "one-way" - incredibly frustrating for you to have k7c be as clear as bell, but not hearing the most important dxer of all - you.

while we can't change propagation and certainly don't want to raise our signal take-off angles, we can and will make sure that dxers far away from kure know that we are making every reasonable effort to work them. to that end, we will be "listening for eu only" whenever an opening - even a low-probability, marginal one - is a possibility. we want to be clear - we have not discounted eu openings before now. everyone on the k7c team has considered eu to be the top priority since the onset of operations last week. but we just haven't been hearing workable signals from eu except during the prime openings. nevertheless, it is important that the dx community has confidence that we are making every effort to make eu qsos. in order to spend more time focusing on eu, we will have to ask our us and ja friends to stand-by and grit their teeth during some periods when it would be easy to work k7c. we hope they'll understand that the special extra effort for the difficult paths is the same as made by expeditions to d6, ft5x, and 3b9 in the past.

how can the dxer that needs a qso with kure help themselves to make the contact without rushing to spend the college fund on an amplifier? fortunately, the steps are easy to take...

1) listen. one well-timed, well-placed call is better than an hour of random calling. if you are transmitting, you are not finding out where or when we are listening. resist the urge to press the mike switch or send your call - listen for the right frequency at the right time, instead.

2) follow the golden rule. in a very weak pileup, bad pileup manners can close down an opening just as easily as low solar flux. it takes very little rude behavior to drop the qso rate from more than one per minute to nothing. take a deep breath and resist the urge to call over someone else.

3) follow instructions. if the k7c op says 200 to 205, you probably won't get in the log at 207 or 198. call only when called or when the requested call is very close to yours. if the k7c op says, "radio charlie", then n0ax should be quiet. when we are working "sa and oc only", then na should go get a drink, visit the head, or kick the dog.

4) spread out according to the instructions. if k7c says "up 2" and everybody is exactly 2.00000 khz up, it makes pulling out calls a very tough job. use timing to set your signal apart from others. send your full call and use standard phonetics every single time.

5) if you have a choice, use your lowest angle antenna, not necessarily the one with the highest gain. the key is the launch or take-off angle of your signal.

finally, please have patience and a little empathy for the team. a dxpedition to a remote location like kure is hard, uncomfortable work although the rewards of making dxers happy is ample compensation. we're out here for you, even though sweat is puddling in our chairs or we are running low on sleep or maybe we were busy fulfilling our time commitments to the island administrator - part of the price of admission to kure. these are not excuses, just the reality of dxpeditioning that we all accepted when we signed up. imagine though, having a ghost crab nibbling on your toes just as you're trying to pull out that 50-watt-and-attic-dipole signal! it's not like home.

keep the faith, brothers and sisters. we're pulling for you just as hard as we can - don't give up!

ward silver nøax, for k7c kure island dxpedition team

k7c这次使用的是垂直天线，最近几次大型的dx远征，都使用了较多的垂直天线，尤其以垂直的dp天线为多，一来可以减轻装备的负担，方便快速设立电台，垂直dp的增益相对垂直天线也高一些，另外，垂直极化的天线在靠海平面的高度使用，效果不亚与定向天线。

由上面所说的天线和地理位置原因，垂直天线的发射仰角非常低，它所发出的信号无须经过太多的跳跃，就可到达接收方，所以，大多数人听k7c觉得信号都不错。但是，这并不异味k7c听别人的信号也很好，因为，很多在内陆的电台、海拔高、或者使用其他发射仰角相对高一些的天线，这样，他们的信号需要多在地球和电离层之间多跳跃几次，才能到达k7c那里，信号就变得缩减得更厉害了。

其实这样情况，大多数使用垂直天线的朋友可能有体会，往往在qso的时候，别人给你一个s5以上的信号报告，但你听别人，只有s1、s2的样子。尤其是在一堆pile-up中，听这些微小的信号，增加了难度。

'

其实这样情况，大多数使用垂直天线的朋友可能有体会，往往在qso的时候，别人给你一个s5以上的信号报告，但你听别人，只有s1、s2的样子。尤其是在一堆pile-up中，听这些微小的信号，增加了难度。

'

确实是这样的，我一直用的是1/2gp，国外电台给我信号都是58、59，可是我听他们只有52、53，很难超收，不过这次叫k7c却是一次就叫通了！

就是就是就是哦
倒v，进行国内通联是很好的天线，一个跳跃就基本是国内范围，用来做dx不是不可以，但是相对垂直天线更困难一些。而垂直天线一个跳跃经常是出国的范围，国内有些地方往往是跃距。各有千秋了。
上次hq比赛那次，好不容易做的各段倒v，结果还不如我的车载天线好用，而且是差距很大哦。

很多美东的电台在跟我聊天的时候都抱怨说，k7c高波段的信号（17m and above）简直太差了，他们对低仰角的说法不屑一顾。
他们开玩笑说，k7c肯定是把天线架设在了靠近ja一边的海滩上:)

http://www.k2kw.com/verticals/whyvert.html

why vertical antennas?

the selection of using vertical antennas was not a natural choice. the "conventional wisdom" for contest-expeditions and dxpeditions was to use yagi antennas when ever possible, regardless of the height. "conventional wisdom" would tell you that a 3 ele yagi at 25' to 30' high on 10m, 15m, or 20m would be the correct (if not only) choice.

when first researching our antenna selection, most of the major contesters in the usa said that the caribbean stations always came in at a high angle. again, more "conventional wisdom" indicating that a low yagi would be the best choice from jamaica.

when we were running our propagation programs, the team noticed that the take off angle to the usa was actually a 1-hop low angle. not the high angle that most people indicated. which was right: conventional wisdom or the computer models?

in our first trip to jamaica during the arrl dx cw contest, the group used a blend of antennas:

verticals for 40m-160m
both a horizontal yagi and vertical array for 20m
yagis for 10m and 15m.
the use of yagis on the high bands seemed appropriate, as we would elevate them between 0.5 and 1.0 wavelength high. the computer models indicated that the yagi should perform ok.

while in jamaica before the contest, the team ran extensive tests with the 20m 2 ele yagi (45' high) and the 2 ele parasitic vertical array. the results were astonishing: of the hundreds of tests, there were only a handful of times the horizontal yagi was better than the vertical array (and only by a small margin).

most of the time the vertical array was 2 s-units stronger than the horizontal yagi! in fact, there were many occasions when a signal was an honest s-9 on the verticals (on the ft1000-mp) and s-0 and almost unreadable on the horizontal yagi. this extreme difference can only be attributed to a signal arriving at a very low angle, where the yagi had little gain.

these results, amidst many additional months of research, convinced the team that verticals by the ocean were the only logical choice for competitive contest-expeditions.

the following graphs were created by n6bv of the arrl:

the first chart (below) shows an analysis of the take off angles from 6y2a to japan on 80m compared to various antenna choices.

first, let's look at the vertical bars (light blue). this is a statistical grouping of all take off angles between 6y2a and japan over all times of the sunspot cycle, over all months of the year, and over all conditions. the data is displayed in the percentage of times a signal will arrive at a given angle: right x-axis is the % of time, and the y-axis is the take off angle.

thus by looking at the first bar on the left, we can see that on average, signals will be arriving at 1 degree take off angle nearly 17% of the time. in fact, you can see that all signals will arrive at or below 13 degrees on all occasions. those are very low angles!!

overlaid on the take off angles are the elevation-plane analysis of standard 80m antennas. lets look at the 80m dipole at 100' (pink with inverted triangles). by most standards, this is a very good antenna. but you can clearly see there is little gain at the low angles.

next, look at the 1x2 verticals over good soil (2 ele parasitic vertical array). this antenna provides you with a large improvement over the dipole.

now lets jump to the "ultimate" 80m antenna: a 3 element full size yagi at 200'!! there aren't many of those around, and who ever uses them will rule the band! (based on conventional wisdom). the 3 ele yagi really does a great job over most arriving signals.

but let's finally look at the 1x2 verticals over salt water (orange with circles). we can see that the verticals have a large advantage over the 80m yagi at the very low angles. in this example, the verticals have a 16 db improvement (3 s-units!) advantage over the yagi. on the higher angles, the vertical still performs well. overall, we believe the 2 ele vertical array over salt water is a better all around antenna than a full size 3 ele 80m yagi at 200'!







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the next graph examines the take off angles on 10m to europe. the reference antenna is a 4 element yagi at 60', an excellent contesting antenna. you can see that the 10m horizontal yagi still does not cover the very low angles, and there is a null where there are still many signals arriving.

the comparison array is the 2x2 vertical array. the 2x2 verticals match the peak gain of the yagi, but also offer excellent coverage over all arriving angles. did we say that verticals by the beach rule!?









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the team has done extensive modeling to all areas of the world on all bands, the results are typical of the examples above: vertical arrays over salt water are very competitive antennas.



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ba4rf de bd2qa 昨天晚上1824听见你，我的天线有问题驻波太大回答不了，你的信号到沈阳599很好。

'

很多美东的电台在跟我聊天的时候都抱怨说，k7c高波段的信号（17m and above）简直太差了，他们对低仰角的说法不屑一顾。
他们开玩笑说，k7c肯定是把天线架设在了靠近ja一边的海滩上:)

'

k7c使用垂直，别人听他好，他听别人不好，这是最郁闷的事情。

首先要自己听得好，至于别人听自己如何，那是他自己的事情，自己想办法吧。

'

ba4rf de bd2qa 昨天晚上1824听见你，我的天线有问题驻波太大回答不了，你的信号到沈阳599很好。

'
roger,昨天我在测试一个天调，也没有指望被谁听到，嘿嘿.

'

就是就是就是哦
倒v，进行国内通联是很好的天线，一个跳跃就基本是国内范围，用来做dx不是不可以，但是相对垂直天线更困难一些。而垂直天线一个跳跃经常是出国的范围，国内有些地方往往是跃距。各有千秋了。
上次hq比赛那次，好不容易做的各段倒v，结果还不如我的车载天线好用，而且是差距很大哦。

'
倒v？

'

很多美东的电台在跟我聊天的时候都抱怨说，k7c高波段的信号（17m and above）简直太差了，他们对低仰角的说法不屑一顾。
他们开玩笑说，k7c肯定是把天线架设在了靠近ja一边的海滩上:)

'

现在一些美国爱好者对这种垂直dp到了一种迷信的程度,夸大了它的效果.

这种垂直dp的发射效率<垂直地网天线，我的感觉，不知道对不对，但是发射角度稍微低一些。

垂直dp的效率应该高于一般的gp,除非gp的有理想地平面。

'

现在一些美国爱好者对这种垂直dp到了一种迷信的程度,夸大了它的效果.

'
我看了看他们的照片，发现他们似乎把steppir的两单元天线垂直架设，当作垂直dp的阵列来用。
其实，我个人的感觉，他们分析的是有些道理，但是他们在分析中没有提到垂直天线的噪音问题－－也许在海岛上没有什么工业的噪音。 但是不是还是会像我们平时使用垂直天线与水平天线对比那样，发现垂直天线的噪音比水平的大。
这个问题最好要问问当年参加bs7h的国内火腿－－ba1ham,ba7jg你们在这里吗？

'

垂直dp的效率应该高于一般的gp,除非gp的有理想地平面。

'
我认为天线发射电磁波是天线两极对空气的充放电过程，垂直dp是2个阵子，下面的一个从另一方面看是否能当成地网的一种？垂直地网天线-gp相面的地网肯定要多过1个，所以我认为垂直dp效率低过垂直地网天线。
真的不知道我的理解是否正确，还望指正

'

我看了看他们的照片，发现他们似乎把steppir的两单元天线垂直架设，当作垂直dp的阵列来用。
其实，我个人的感觉，他们分析的是有些道理，但是他们在分析中没有提到垂直天线的噪音问题－－也许在海岛上没有什么工业的噪音。 但是不是还是会像我们平时使用垂直天线与水平天线对比那样，发现垂直天线的噪音比水平的大。
这个问题最好要问问当年参加bs7h的国内火腿－－ba1ham,ba7jg你们在这里吗？

'
我感觉不想听到的信号都算是噪音，不单单工业噪音，包括pilup时，只要听到一个人的信号就好了。
我也有感觉他们象是做了相控阵列，曾经听过他们信号半天的时间，有时候短时间信号强度变化比较大的还是。

一个波长就是正弦波的360度，dp也就是半波长天线，每边振子负责90度，但发射仰角受架设高度影响；gp的垂直部分负责半波中的90度，另外的90度由地网系统负责，这就需要良好的地网系统才能把提高效率，但gp拥有低发射仰角的优势；在这种情况下就发展出垂直dp，垂直dp本身已经完全负责了180度，无需再为良好的地网系统伤脑筋，但却拥有gp的低发射仰角优点，同时也承继了gp高噪音的缺点。

同意vr2kw的，gp的地网只最终目的还是为了产生天线主体的镜像，也就是垂直dp的下半部分。这就要求地网很好才能达到垂直dp的效果。

多谢了！学习了:)
以后就放心使用垂直dp了

其实只要把水平dp架设相当的高度，同样也可以有很低的发射仰角，或者同时还可以拥有适合中距离通讯的副波瓣，而且噪音相对比gp低。
垂直dp可能是最简单高效的天线，但我个人比较喜欢loop，loop比dp噪音更低，而且有接近3db的增益，受架设高度的影响较少，但最大的缺点是体积比较庞大。