下列两种情况表明交易活动的不寻常：1、交易量高于平常表明交易兴趣浓厚；2、交易量也可以低于平常水平，显示交易兴趣匮乏。这两种情况对于推测价格走势都很重要。
识别不同寻常的交易量
交易日志的读者或许会发现，我经常用到比尔麦克拉伦的方法来快速识别不寻常的交易量。
交易量图表上的两条水平线把交易量划分成了三类：
a.交易量突破上面的一条线：不同寻常的高交易量；
b.交易量位于两条线之间：寻常交易量（大部分的k线可以被忽略，但是要留意趋势的变化：维持一周或更长时间的交易量减少或增加。）
c.交易量位于下面一条线的下方：不寻常的低成交量（成交量枯竭）。
交易量横线的画法：
• 根据去年的交易量来设置这两条横线；
• 确保上面的一条线上方能显示出每季度的高交易量；
• 同样，下面的一条直线也要突出每个季度的低交易量；
• 过多的交易信号会削减这两条线的有效性，可以将上方的一条线设置为40或50。
如果我将上方的横线设置在1.5百万成交量，那么我将错失很多有用的交易信号。
注意：
• 偶尔的高成交量是某个大机构的交易引起的，该机构的购买决定或许是几周之前就已经被商讨，与图表上的高交易量没有必然联系。如果成交量达到日常均值的5~10倍，不论是否由某一机构引起，你都应该进场；
• 不要被圣诞节、复活节或者周末到来之前的低交易量所迷惑；
• 小心对待指数、股票等结算日引起的交易量升高。
交易信号
高价格和高交易量
在一个强劲的上升趋势中，高价格和大成交量通常或引起反转：在过度超买或超卖的情况下，市场专业人士会逆趋势交易。
上升趋势：上图中显示的是上升趋势的衰竭状态。价格长期呈现上升走势，并在[1]处快速上升。接下来的k线走出了长影线，交易量也随之升高，预示着获利退场。[6]处价格范围波动大，交易量进一步升高。[7]处是典型的衰竭缺口，日交易量也随着达到了1千万。接下来的4天股票价格几乎下降了40%。[12]处的小阳线和高交易量预示一轮反转，但是买方已近衰竭，上升幅度有限。接下来一轮下降趋势开始。
下降趋势：[1]处恐慌性的抛售表明价格被卖方控制。[2]处的成交量巨大表明买卖双方势均力敌，进而形成了支撑位。
窄幅震荡（买卖双方势均力敌）期间的交易量升高通常会使价格突破震荡区间并沿袭原来走势，常会伴随着长尾线的蜡烛图。
加德士澳大利亚石油股价在8.5~10区间震荡长达6个月，突破之前出现了两个典型的买入信号：[1]处在震荡区间的下方出现空头陷阱；[2]处阻力位的贝壳状回调，交易量也显著增加。
下面的等量成交图通过宽度展现交易量，开盘价、收盘价描述方法与蜡烛图类似。
[a]处在价格达到阻力位10.00出现一大波获利回吐，[c]处价格穿透支撑位，导致一轮抛售。[d]处狭窄的交易范围和高交易量提醒我们买方仍然强势，并全部吸收了之前获利回吐的卖单。[e]处交易量进一步扩大，但是主体部分狭窄，代表着一根十字星线。[f]处卖方压力减少，并在[g]处枯竭。说明新一轮的上涨即将到来。
交易量衰竭
上图股价的小幅扇贝形态回调是上升趋势中的牛市信号，或下降趋势中的熊市信号。它的价格波动范围小，交易量低，表明卖方（买方）压力减少。
趋势的迅速反转同样也是进场的信号，前提是该反转持续时间短并带有长长的尾线，或者是伴随着交易量的升高。
交易量迅速升高产生的缺口同样也是主要的交易信号。比如上图中[7]处的衰竭缺口和下面我们讲述的两个实例。
1. [1]处一个巨大的衰竭缺口伴随着高成交量说明买方放弃希望；
2. 接下来的一天，市场专业人士在意识到该股票的真正价值之后以低价买入股票；
3. 三个月后，价格再次走低并试探4.00的支撑位。在[3]处缺口伴随高交易量形成之前，价格实际上已经穿透了支撑位。牛市在价格于[3]处突破下降趋势线的时候显现出来。上述例子中，价格同样也跳过了支撑/阻力位，进一步加强此时的牛市信号；
4. [4]处小幅回调和低交易量表明下降趋势枯竭。
Volume Spikes and Dips
There are two times where daily volume will highlight unusual trading activity:
1. Volume may spike above the normal range, signaling unusual trading interest; and
2. Volume may also dip below the normal range, indicating a lack of trading interest.
Both of these signals are important and can forewarn of future price movement.
Identifying Unusual Volume
Readers of the Trading Diary will notice that I frequently use a method, learned from Bill McLaren, to quickly identify unusual volume.
Two horizontal lines are visually fitted over Volume, separating volume bars into three categories:
• above the top line = unusual activity
• between the lines = normal activity (daily bars can be largely ignored but one should still watch for trends: increasing or decreasing volume over a week or more)
• below the bottom line = unusually low activity (where volume has dried up)
Hints
• Fit the lines based on the last year's volume and extend them forward each week when you review the chart;
• Ensure that the top line will highlight at least one volume bar in each quarter;
• Likewise with the bottom line;
• Too many signals on the other hand will negate their usefulness - set an upper limit of 40 or 50.
I would have missed a number of decent signals, in April/May on the above chart, if I had raised the upper line to 1.5 million.
Cautions
• Occasionally volume spikes are the result of a single large institutional transaction. The actual deal may have been negotiated over several weeks and has little relevance to the course of sales on the day on which it is booked. If volume is 5 or 10 times the daily average, you need to establish whether it was caused by a single transaction.
• Be careful not to confuse low trading volume with the lull in activity generally experienced over Christmas, Easter and prior to most long weekends.
• Volume spikes on triple-witching days (especially on indexes and major stocks) should be treated with caution.
Trading Signals
Price and Volume Spike
In a strong established trend, large price and volume spikes often precede a major reversal: the security has either been substantially overbought or oversold and market professionals step in and buy/sell against the trend.
Up-Trend
The Charles Schwab chart (above) shows a classic blow-off pattern in an up-trend. The long-established trend started to accelerate at [1]. Day [2] displays a tall shadow and huge volume, signaling profit-taking. A wide-ranging day at [6] leaves a tall blue candle with even higher volume -- a typical blow-off signal. The gap on day [7] is another classic blow-off sign -- see exhaustion gaps. Daily volume now approaches a massive 10 million as the big money steps in, selling the stock down almost 40% over the next 4 days. A narrower blue candle and strong volume at [12] signal the start of a rally but buying demand has been absorbed and the rally fizzles out, commencing a primary down-trend.
Down-Trend
In a strong down-trend, a wide ranging day [1] accompanied by a volume spike signals the transfer of large amounts of stock from weak to strong hands, establishing a strong support level. Australian ear implant specialist Cochlear fell sharply in 2002 before forming a broad base in 2003 until a fall below the $30 support level eventually triggered panic selling (the "abandonment of all hope" mentioned by Charles Dow). The stock fell sharply on day [1] on huge volume. Compare the trading range to day [2] which showed even higher volume as large buyers, perceiving real value, started buying against the trend, establishing a strong support level at $20.
Trading Range
In a trading range, large volumes on a wide-ranging day will signal the likely direction of a breakout.
Compressed Spring
In a reaction during a trend, a volume spike combined with a narrow trading range often precedes a big move in the direction of the trend; committed opposition (to the reaction) having compressed the trading range.
A similar (though weaker) signal is offered by a volume spike accompanied by a candle with a long tail.
Caltex Australia consolidated in a band between 8.50 and 10.00 for about 6 months, following a strong up-trend, before exhibiting two classic buy signals:
• a bear trap [1] at the lower border of the consolidation; followed by
• a small scallop below resistance at [2].
What is remarkable is the volume on the scallop at [2]. The equivolume chart below depicts volume by the width of the bars (open and close are reflected in a similar manner to candlesticks).
Profit-taking is evident at [a] as price again approaches resistance at 10.00. Price penetrates resistance at [c], triggering committed selling. The narrow range and huge volume at [d] alert us to the presence of strong buying, absorbing all stock that profit-takers offer in the market. Day [e] is looser, with a wider range but narrow body resembling a doji candle, on even larger volume. Selling pressure abates somewhat at [f] before a complete dry-up of trading activity at [g] signals that sellers are exhausted and a rally is imminent.
Trading Dries Up
A shallow correction/reaction in the form of a scallop, such as the one on the above Caltex Australia chart, is a bullish sign in an up-trend (or bearish in a down-trend). The best signal that the primary trend movement is about to resume is a narrow ranging day on unusually low volume, indicating that selling (or buying) pressure has abated.
This page has two examples:
• at [g] in the Caltex equivolume chart above; and
• at [4] in the Brambles chart below.
Reactions
A sharper reaction against the trend can still offer good buy signals (or sell signals in a down-trend), provided that the reaction is of short duration and ends with a long tail or reversal signal accompanied by a volume spike.
Gaps
Gaps accompanied by a volume spike often provide major signals. Earlier we saw a prominent exhaustion gap [7] during a blow-off on the Charles Schwab chart. The Brambles chart below provides two excellent examples:
• an exhaustion gap during a cathartic sell-off at [1]; and
• a breakaway gap accompanied by another volume spike at [3].
1. The large downward exhaustion gap is accompanied by massive volume as sellers abandon hope.
2. By the next day market professionals, having spotted real value, are buying in the face of the down-trend, mopping up all available stock at keen prices.
3. Three months later price again tests $4.00 after drifting lower. The stock actually penetrates the support level before gapping upwards accompanied by a volume spike at [3]. Sometimes referred to as a hole-in-the-wall gap, a strong bull signal is made when price gaps to above a downward trendline. In the above case, price also gaps above the support/resistance, adding extra weight to the signal.
4. Volume and trading range dry up on a shallow retracement.
Breakouts
A volume spike immediately after a breakout signals a healthy trend. Absence of volume signals weakness.
本文翻译由兄弟财经提供
本文来源：http://www.incrediblecharts.com/technical/volume_spikes.php