Q: What values should I include for external losses, such as body absorption, building losses, etc.?
A: The following table provides some general guidelines for loss values introduced in various circumstances. These values can be used when determining the amount of signal available at a receiver's input terminals for a given field strength. For example, a hand-held receiver in the 150-170 MHz band worn on the hip will experience approximately 17 dB of loss (due primarily to the body proximity), according to the table below. Therefore, if the computed field strength for a given location is 40 dBu, the actual field strength available to the antenna of the hip mounted receiver may be as low as 23 dBu (43 - 17).
These values can also be used to determine the amount of field strength needed for operation of specific receiver hardware using the equations in the "Field Intensity Units" FAQ article, or using the TAP "Compute Required Field" program in the Utilities menu. The loss values shown below can be used along with the manufacturer's specification for required receiver input (voltage or power) to determine the field strength (in dBu) necessary to produce that voltage or power at the receiver input terminals in the presence of losses due to body or vehicle proximity, etc.
Measured losses inside building:
| Floor | VHF | UHF |
| Basement | -34 dB | -27 dB |
| 1st | -29.5 | -23.5 |
| 3rd | -26 | -20 |
| 5th | -23 | -15 |
| 10th | -12 | -3.5 |
| 14th | -7.8 | +2.0 dB |
Additional measured losses by General Electric:
150-170 MHz Hand Held, vertical -6 dB
- Hand Held, angled -10 dB
- Hip mount -17 dB
450-470 MHz Hand Held, vertical -17 dB
- Hand Held, angled -18 dB
- Hip mount -17 dB
Measurements inside vehicle by General Electric
150-174 MHz
- Radio on driver's left hip, antenna clear -25 dB
- Radio laying on seat speaker up with
- antenna toward front -36 dB
- Radio connected to vehicular charger and
- unity gain antenna on rooftop -2 dB
450-470 MHz
- Radio on driver's' left hip, antenna clear -24 dB
- Radio hand held, vertical -16 dB
- Radio connected to vehicular charger and
- unity gain antenna on rooftop -4 dB (15' RG-58/U coax)
Losses due to presence of emergency light bar on roof, antenna mounted center of roof: -2 to -7 dB at 840 MHz.
(Additional loss values were measured at the
4th Annual TAP Engineering Seminar.) Copyright 1999 by SoftWright LLC
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