power antenna length

[rmmchl]

most of hirschman and other brands of antennas extend too long and do not look well on our cars. Mine is on the left rear. I want a mast no longer than about 20 to 24 inches. Does anyone have any ideas.

[hauser]

The original anennas were long.

[66andBlue]

The optimal length of a car antenna depends on the station frequency that you want to receive because for best reception the antenna should match the wavelength of the transmitter either exactly (1 to 1) or at 1/2, 1/4, 1/8  wavelength
The FM band goes from a frequency  ~88 MHz or when expressed as wavelength = 341 cm = 134 inch
to a frequency of 108 MHz = 278 cm = 109 inch.
Thus if your favorite station is located at 88 MHz then the antenna must be pulled out to a length of 33.5" (1/4 wavelength) but only 27" at the other end of the scale.  Automatic antennas tuned to the middle of the FM band (98 MHz) should be about 29 inch or 72 cm long.

But if you are tuned in mostly to the firebrands on AM talk radio then a shorter antenna is OK. AM band spans from 560KHz to 1.6 MHz thus the middle of about 1 MHz = in wavelength 28532 cm  = 11232 inch. That means to match that length the antenna should be either  1/264 wavelengths = 44 inch or 1/512 wavelengths = 21 inch long.
Most automatic antennas just pull out to the full length but some have an additional stop switch and can be adjusted to at almost any length.

[114015]

Alfred is absolutely correct here.

Furthermore,
the oldest period Hirschmann (power) antennas had aerials of about 1.5 meter = 150 cm = 59.1 inches. These were designated for short wave and AM radio reception only.

There is one factory leaflet showing a 1963 230 SL with this antenna, pictured in the first 230 SL sales brochure. It is the "Moderne Zeiten" picture with a silver 230 SL with hardtop, without beauty rings, non-perfect fitting engine hood, a beautiful lady at the ivory steering wheel and the car in front of an (ugly German) tower building.

Later cars had a 1.2 meter telescope = 47.24 inches long (all info from Rainer Königs, www.koenigs-klassik.de, our German "Ed Ebel" in this area).
Even more later cars (280ies and such) had even shorter aerials, 1 meter or so.
But definitely 72 cm areals (= 28 inches) is too short.
Maybe "beautiful ore correct" to your eyes but not period-correct for our cars.

Just my 2 cents
Achim
(with 1.2 meter aerial)