Now here's my question - will I notice the improvement
enough? I've had several OM's tell me that on SSB, CW
or HF I would but not on 2m/440 simplex and repeaters.

Well, a 6 dB boost would double your range, IF you aren't hitting the limits
imposed by your radio horizon. VHF and UHF don't "bend" much, so once you go
beyond your radio horizon, you're pretty much done, no matter how much
signal you had. It will improve your signal into repeaters, where you were
a little noisy before, you should be quiet. On simplex, you'll notice
better signal once you get far enough away that you used to be no longer
full quieting.

In an FM receiver, there is a signal limiter, that caps the signal level, so
if you were already "full quieting", then no amount of power increase would
result in a better signal. If you are far enough away that you're not full
quieting, then yes 6dB will be noticeable.


--
KC6ETE Dave's Engineering Page, www.dvanhorn.org
Microcontroller Consultant, specializing in Atmel AVR

Well, a 6 dB boost would double your range, IF you aren't
hitting the limits imposed by your radio horizon.
_____________

Clarification: the coverage AREA doubles for the above situation, but the
"range," or distance from the transmit antenna to a given field strength
value increases only by about 40%.

Here are the numbers, using the FCC's F50,50 curves for UHF NTSC TV
propagation.

50W ERP from 100 feet above average terrain:

60dBuV/m at 2.99 miles
Coverage area within the 60dBuV/m contour = 28 sq miles

200W ERP from 100 feet above average terrain (a 6dB ERP increase from the
above example):

66dBuV/m at 2.99 miles
60dBuV/m at 4.2 miles
Coverage area within the 60dBuV/m contour = 55.4 sq miles

The radio horizon for these examples is located about 14 miles from the
antenna site (at a 0.15 degree depression angle).

RF

Visit http://rfry.org for FM transmission system papers.

From: "Richard Fry"
Date: 11/9/04 6:29 AM Pacific Standard Time
Message-id:

Well, a 6 dB boost would double your range, IF you aren't
hitting the limits imposed by your radio horizon.
_____________

Clarification: the coverage AREA doubles for the above situation, but the
"range," or distance from the transmit antenna to a given field strength
value increases only by about 40%.

Here are the numbers, using the FCC's F50,50 curves for UHF NTSC TV
propagation.

50W ERP from 100 feet above average terrain:

60dBuV/m at 2.99 miles
Coverage area within the 60dBuV/m contour = 28 sq miles

200W ERP from 100 feet above average terrain (a 6dB ERP increase from the
above example):

66dBuV/m at 2.99 miles
60dBuV/m at 4.2 miles
Coverage area within the 60dBuV/m contour = 55.4 sq miles

The radio horizon for these examples is located about 14 miles from the
antenna site (at a 0.15 degree depression angle).

RF

Visit http://rfry.org for FM transmission system papers.

I stand by my statement, " 6dB doubles your range". Rather than going to an
obscure site and referencing something about some TV coverage - just run the
numbers. We are not talking about broadcast to consumer TV sets here. Anyone
who has done path analysis knows that 6dB doubles the range. Check into it -
you might learn. On second thought here is the equation -
Loss (dB) = 36.6 + 20 log F (MHz) + 20 log D (statue miles). And, again, as
first stated, " within the limits of the radio horizon". Off course, space
shuttle mobil and EME folks don't worry about the horizon.

KF6HHS
Retired, now life moves at my pace.
please note spam filter

"KF6HHS" wrote:
I stand by my statement, " 6dB doubles your range...
Anyone who has done path analysis knows that
6dB doubles the range. Check into it - you might learn.
_____________

I've checked, thanks.

The field strength values I posted are based on empirical data used by the
FCC to determine coverage range, and protection ratios for FM & TV broadcast
stations. The same physics applies to "hams" as to broadcasters.

The free-space path loss formula over a reflection-free path gives different
results. But, as the original post asks " Is it worth it? Will I notice?,"
the real-world values from the FCC curves will give more applicable answers.

Verify my numbers and conclusions for yourself at
http://www.fcc.gov/mb/audio/includes/curves.html .

You might learn g.

RF

KF6HHS wrote:
"I stand by my statement: 6 dB doubles your range."

The "Sommerfeld formula" is ancient and accepted. It says:
Ground-wave field strength = (A) Eo / d
Eo = field strength at the surface of the earth at a unit distance from
the transmitting antenna, neglecting earth`s losses
d = distance to the transmitting antenna
A = factor taking into account ground losses

If the earth is perfect, the above reduces to:
volts/meter = Eo / d
assuming the right scale factors.

At twice the distance, the field strength over flat earth is halved.

The resulting current is also halved. Thus, the power, their product, is
quartered. That`s a 6dB change from doubling the distance.

On the other hand, if you want to produce the same field strength at
twice the distance, you must use 4X the power by the Sommerfeld formula.

Best regards, Richard Harrison, KB5WZI

On Wed, 10 Nov 2004 20:50:31 -0600, (Richard
Harrison) wrote:

That`s a 6dB change from doubling the distance.

Hi Richard,

Unfortunately, from FCC field data for BOTH AM and FM curves over real
earth, they show anywhere from 6dB to 20dB+ depending on range from
the transmitter. In most respects departure has to do with earth
curvature and earth soil conditions. Even sea water paths do not
recover the greater than 6dB requirements.

73's
Richard Clark, KB7QHC

Richard Clark is correct. The FCC family of propagation curves shows
greater attenuation than results from signal spreading into an ever
enlarging volume. However, these curves also include an inverse distance
line which is the 6 dB per doubled distance line. Its drop, make that
decline, only derives from the growth in volume the fixed amount of
expanding signal fills as it propagates.

Best regards, Richard Harrison, KB5WZI

A long time ago, when there was not so much man-made noise, I found that in
the almost-flat-country at the extreme edges of coverage from a base station
to a mobile station, the rate of decrease was roughly one db per statute
mile. This was in the 160 MHz range.
The mobile is so far away from the base that the received signal is
"noisy." I am considering rural locations and a terrain without significant
hills.

On the average, +3db of power at the base provided another 3 miles of
(poor quality) coverage. More often than not, coverage was limited by the
transmitter power of the mobile and the noise level at the base!

The question asked can start to be answered when one knows the value
placed on increased coverage.

73 Mac N8TT
--
J. Mc Laughlin; Michigan U.S.A.
Home:

On Sat, 13 Nov 2004 12:35:32 -0500, "J. Mc Laughlin"
wrote:

A long time ago, when there was not so much man-made noise, I found that in
the almost-flat-country at the extreme edges of coverage from a base station
to a mobile station, the rate of decrease was roughly one db per statute
mile. This was in the 160 MHz range.
The mobile is so far away from the base that the received signal is
"noisy." I am considering rural locations and a terrain without significant
hills.

On the average, +3db of power at the base provided another 3 miles of
(poor quality) coverage. More often than not, coverage was limited by the
transmitter power of the mobile and the noise level at the base!

The question asked can start to be answered when one knows the value
placed on increased coverage.


I'll bet I can get good reliable converage to a 100 miles with a 5
watt HT and a rubber duck with todays receivers.
50 to 75 mile coverage to mobiles.

It's worked on 52 simplex every time I've tried it.
Fasten the belt clip to the strap above the arm rest with the rubber
duck sticking straight up into the big window, Hook a boom mike and
ear piece to the HT and put my ANR head set over it.
Call CQ and darn near get a pile up.

Ain't nothing like a good tall antenna.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com
73 Mac N8TT