**** GAIN **** 
How Does DB Gain effect your ability to Receive/Communicate ? 
What's more important, Antenna GAIN or Antenna PATTERN ? 
What's a DB ?? THREE DB is equivalent to DOUBLING your 
POWER (when your talking about GAIN), but is also equivalent 
to CUTTING your POWER IN HALF (when your talking about 
LOSS). If you double your power, do you double your distance ?
The Answer is NO. Only SOME of the hiss noise will be reduced 
on weaker signals. Most human beings cannot detect any differ- 
ence in how a signal sounds with a 1 DB change. How can an 
Antenna have GAIN ?? If a antenna has 3 DB gain, it doubled 
your power, right ? WRONG ! It gets this gain (only in certain 
directions) by taking away its ability to receive (or transmit) in 
other directions. That could be good (if you didn't want to receive/ 
transmit in that other direction) or it could be bad (if it caused you 
to lose the performance you wanted in that particular direction). 
The Antenna Pattern tries to illustrate what you may experience 
when using a particular antenna for a particular application. 
*** H.A.A.T. *** - Height Above Average Terrain.
Your Elevation Above Sea Level should be compared to the 
Elevations Above Sea Level in a 360 degree circle around your 
location. Take a measurement at every 1 or 2 mile point 
extending out 10 to 20 miles from your location at every 22.5 
or 45 degree direction. Add to your Elevation Above Sea Level, 
the Height above ground your antenna is. If you compare that 
total (Your E.A.S.L. + Antenna Height) to the E.A.S.L. 's in 
each direction, as soon as the directional E.A.S.L. equals your 
Antenna E.A.S.L., your reception in that direction will start 
being Shadowed by that ground. The higher the directional 
E.A.S.L. is above your antenna E.A.S.L., the greater the shadow 
effect will be in causing attenuation of VHFUHF radio signals. 
For Good VHF/UHF results in a desired direction, your antenna 
should be located (following Common Sense Safety Guidelines) 
as high as possible above the E.A.S.L. in that desired direction 
with the proper amount of Gain, and, more importantly, the 
right Antenna Pattern (see GAIN above). 
*** COAX *** - Types to Use, Losses. 
The LONGER your Coaxial Cable length is from the Antenna to 
your Radio, the more attention you must give to the type of Coax 
your using. You could be losing most of the signal before it even 
gets to your Receiver !! RG-58 and RG-59 Coax Cable is the 
worst ones to use, yet most Scanner and Television Antenna 
installations use those types of cables most often. Any installation
exceeding 50 feet of coax cable can often improve their overall 
performance by simply upgrading the type of coax being used. 
For installations that are 100 feet and more, the improved 
performance may be quite surprising. Losses in Coaxial cable 
equally affect the receiving and transmitting performance. For 
more information on commonly used Coax Cables, 
Coaxial Cable Feed-Line Losses for common cables 
db Loss per 100/ft of Coax shown at: 
10, 50, 150, 500 and 1000 MHZ
Figures Shown could vary as much as 5 or 10 percent dependent on manufacturer. 
TYPE	IMP	VF	10	50	150	500	1000	
RG-6	75	75%	.70	1.85	3.00	5.00	7.00	
RG-8-X	52	75%	.90	2.60	4.60	8.50	13.50	
RG-8	52	66%	.68	1.75	2.70	4.75	6.50	
RG-11	75	66%	.68	1.75	2.70	4.75	6.50	
RG-58	53.5	66%	1.50	3.30	5.60	10.50	17.00	
RG-59	73	66%	.93	2.70	4.70	8.50	13.00	
RG-62	93	86%	.93	2.00	3.60	6.20	8.70	
RG-213	50	66%	.68	1.75	2.70	4.75	6.50	
RG-214	50	66%	.68	1.75	2.70	4.75	6.50	
9913	50	84%	.44	.97	1.75	3.20	4.50	
1/2" Hardline	50	81%	.22	.55	1.00	2.00	3.00	
3/4" Hardline	50	81%	.17	.44	.83	1.70	2.50	
7/8" Hardline	50	81%	.13	.36	.70	1.50	2.30	
1/2" Hardline	75	81%	.24	.64	1.20	2.40	3.60	
3/4" Hardline	75	81%	.18	.46	.87	1.80	2.70	
7/8" Hardline	75	81%	.13	.40	.75	1.60	2.35	
db relating to change in % of Power ( approximate Loss): 
1db/20% 2db/36% 3db/50% 4db/60% 5db/68% 6db/75% 
7db/80% 8db/84% 9db/87% 10db/90% (losses/performance) 
Basic Electronic Formulas Used in Radio 
Ohm's Law: Current (Amps) = Voltage divided by Resistance (Ohm's) 
Ohm's Law: Resistance (Ohm's) = Voltage divided by Current (Amps)
 Ohm's Law: Voltage (Volts) = Current (Amps) times Resistance (Ohm's) Power (Watts) = Current (Amps) times EMF (Volts) 
Half-Wave Dipole in Feet (in Air) = 492 divided by Frequency (MHZ) 
Half-Wave Dipole in Ft. (end supported) = 468 divided by Freq (MHZ) 
Meters = 300 divided by the frequency (MHZ)

*** USE OF PRE-AMPLIFIERS *** 
Do They Help You, OR, Do They Make It Worse? If you live in 
a Metropolitan Area, you will generally find that when you put a 
pre-amp on your Television or Scanner antenna, your reception 
will actually get worse! This is caused by nearby transmitters 
which, even though they are on different frequencies than what 
you are trying to get, will over-load the pre-amp and/or the front- 
end of your receiver, and, will cause much more mixing of the 
stronger signals (pager transmitters are a good example), which 
will cause those signals to appear on many other frequencies you 
are trying to receive on. You are better off using a better antenna 
and coax for your installation. If you live more than 5 to 10 miles 
from any strong Radio/FM/Television/Pager/Land-Mobile 
communications transmitter, then the possibility of a pre-amp 
could help your reception performance. There are some 
manufacturers of Filters (or Traps) that are designed to reduce 
FM Broadcast or Pager Interference that could be inserted in your 
coax, but for best results, those filters should be on the antenna 
side of your pre-amp. The mixing of strong signals in your Receiver 
is called INTERMOD and is very annoying. 
*** WEATHER PROOFING *** 
How to Keep It Working like it was when it was new. 
Radio Frequency (RF) Signals/Power, and WATER, DO NOT MIX ! 
*** SAFETY *** 
Power Lines, Wind and Lightning. 
No Antenna should be installed in a location, whereas, if it fell down it
could come into contact with any electrical power lines. Any Antenna
Installation IS ONLY AS STRONG AS ITS WEAKEST POINT !