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A caphat on a mobile antenna is used to decrease the inductance needed to match the antennas feed point that is inherent using a shortened antenna.

The inductor is the loading coil and when using a shorter non 1/4 wave antenna for any given frequency, the more coil turns needed for a match. However, the more turns on a coil, the more loss there is. So this is the trade off for running a shortened antenna.

For us running mobile 100 watt Ham rigs, the losses are significant to where we are in single digit wattage ERP to milliwatts on lower bands like 80 and 160 meters. This is because a lot of coils is needed to match a very low impedance feedpoint. A caphat on these bands can be an improvement.

A 102 whip has no loading coil but the antenna feedpoint isn't 50 ohms so there is a bit of current loss. A properly designed shunt coil would fix that but it isn't likely to make a difference in performance but it'll satisfy perfectionist.

A cap hat would be useless on a 102 whip.

Here's my HF screwdriver antenna with a cap hat. Look how much coil can be extended! The cap hat let's it use half the coil on some bands compared to without it.

[ATTACH=full]48565[/ATTACH]

<blockquote data-quote="fourstringburn" data-source="post: 777519" data-attributes="member: 2920">A caphat on a mobile antenna is used to decrease the inductance needed to match the antennas feed point that is inherent using a shortened antenna.&nbsp;The inductor is the loading coil and when using a shorter non 1/4 wave antenna for any given frequency, the more coil turns needed for a match. However, the more turns on a coil, the more loss there is. So this is the trade off for running a shortened antenna.&nbsp;For us running mobile 100 watt Ham rigs, the losses are significant to where we are in single digit wattage ERP to milliwatts on lower bands like 80 and 160 meters. This is because a lot of coils is needed to match a very low impedance feedpoint. A caphat on these bands can be an improvement. A 102 whip has no loading coil but the antenna feedpoint isn&#039;t 50 ohms so there is a bit of current loss. A properly designed shunt coil would fix that but it isn&#039;t likely to make a difference in performance but it&#039;ll satisfy perfectionist. A cap hat would be useless on a 102 whip. Here&#039;s my HF screwdriver antenna with a cap hat. Look how much coil can be extended! The cap hat let&#039;s it use half the coil on some bands compared to without it. [ATTACH=full]48565[/ATTACH]</blockquote>

[QUOTE="fourstringburn, post: 777519, member: 2920"] A caphat on a mobile antenna is used to decrease the inductance needed to match the antennas feed point that is inherent using a shortened antenna. The inductor is the loading coil and when using a shorter non 1/4 wave antenna for any given frequency, the more coil turns needed for a match. However, the more turns on a coil, the more loss there is. So this is the trade off for running a shortened antenna. For us running mobile 100 watt Ham rigs, the losses are significant to where we are in single digit wattage ERP to milliwatts on lower bands like 80 and 160 meters. This is because a lot of coils is needed to match a very low impedance feedpoint. A caphat on these bands can be an improvement. A 102 whip has no loading coil but the antenna feedpoint isn't 50 ohms so there is a bit of current loss. A properly designed shunt coil would fix that but it isn't likely to make a difference in performance but it'll satisfy perfectionist. A cap hat would be useless on a 102 whip. Here's my HF screwdriver antenna with a cap hat. Look how much coil can be extended! The cap hat let's it use half the coil on some bands compared to without it. [ATTACH=full]48565[/ATTACH] [/QUOTE]

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