According to prevalent definition of Kahal Yoga in Vedic astrology; if in a horoscope, the lord of 3rd house and lord of 10th house are in Kendra from each other and the lord of ascendant is strong, Kahal Yoga is formed in the horoscope. Kahal Yoga can bless the native with good results related to profession, finances, wealth, reputation, fame and many other things. Kendra houses are 1st, 4th, 7th and 10th.
In real practice, Kahal Yoga is not seen producing such results when only the aforementioned conditions are met. Hence some other condition should be met in order for this yoga to be formed effectively in a horoscope. Looking at this condition, the lords of the third and tenth house should be benefic in such horoscope. Looking at exceptions; this yoga may not be formed in horoscopes with Leo and Aquarius ascendants. Venus rules the third and tenth house in the first case and Mars rules these houses in the second case. Since one planet rules both these houses; this yoga may not be formed in these cases.
Taking an example, suppose Mars is placed in the first house of a horoscope in Aries, a combination of Mercury and Saturn is placed in the ninth house in Sagittarius. Mercury rules the third house and it is malefic whereas Saturn rules the tenth house. They are both placed in Kendra (1st house) from each other. However, Kahal Yoga may not be formed since malefic Mercury may afflict Saturn. Hence the native may not benefit from this combination and he may instead face problems.
Taking another example, suppose exalted Mercury is placed in the fourth house of a horoscope in Virgo, Sun is placed in the third house in Leo and Jupiter is placed in the ninth house in Aquarius. Gemini rises in the ascendant, Sun rules the third house; Jupiter rules the tenth house and both these planets are benefic in the horoscope. They are placed in Kendra (7th house) from each other. Hence Kahal Yoga may be formed in the horoscope.
Once the formation of Kahal Yoga is confirmed in a horoscope, the next factor to check is its strength. The strength of this yoga is calculated through the placements of planets involved in its formation in various signs, nakshatras and navamshas; as well as through the influences of other benefic and malefic planets on them. The overall theme of horoscope and running times (Mahadashas) also affect the strength of this Yoga.
Taking an example, suppose exalted Mercury is placed in the fourth house of a horoscope in Virgo and a combination of Sun and Jupiter is placed in the third house in Leo. Within Leo; Sun is placed in Aries navamsha of Magha nakshatra whereas Jupiter is placed in Cancer navamsha of Magha nakshatra. Both Sun and Jupiter are strong in Leo and they are exalted in their respective navamshas. Hence strong Kahal Yoga may be formed.
Let’s look at influences of malefic planets on this yoga. Suppose in the same horoscope; malefic Saturn and Ketu are also placed in the third house in Leo. Saturn and Ketu may afflict Sun and Jupiter. As a result, Kahal Yoga may witness significant reduction in strength. Hence the native may not benefit a lot from this Yoga.
Looking at the running times; when Mahadashas (planetary periods) of malefic planets are in effect; benefic effects of Kahal Yoga may reduce. When Mahadashas of benefic planets other than the ones involved in the formation of this yoga are in effect; benefic effects of this yoga may increase. When Mahadashas of the planets involved in the formation of Kahal Yoga are in effect; the native may witness maximum benefits through this yoga. For instance; in the recent example, the native may benefit the most during Sun Mahadasha, Mercury Mahadasha and Jupiter Mahadasha.