Handheld GMRS/FRS radio antenna gain question
 

Hi everyone,

This sure seems like the group I've been looking for.

I've been researching GMRS/FRS handheld radios and have been a little
disappointed in the "bubble-pack" radios that are commonly available for
this radio band. The first thing I learned about was how ridiculous the
manufacturer's power ratings and claimed reception distances were. I've
decided to ignore the marketing & sales hype and just try to understand the
basic physics of radio.

The one thing I think I've learned is that three most important components
of a radio are the antenna, the antenna and the antenna. Most consumer
GMRS/FRS radios come with a three inch or less antenna but I've seen some
with a 1/4 wave antenna. My understanding is that FRS antennas can not
exceed the gain of a 1/2 wave dipole and they can not be interchangeable, so
you have to make the correct choice when you buy the radio. I have some
basic understanding of the general theory of antennas, and someone suggested
to me that a 1/4 wave antenna could suffer a 2dB signal loss compared to a
1/2 wave antenna. I'm interested in learning the additional dB loss in
going from a 1/4 wave to a 2-3" "bubble-pack" antenna.

I guess where I'm coming from is that I'm wondering if, all other things
being equal, can I realistically get equal or better reception with a pair
of 0.5 watt ERP radios with a 1/4 wave antenna versus a 1-2 watt ERP radio
with 2-3" antenna. The advantage of broadcasting with only 1/2 watt is very
desirable from a battery life point of view. I believe increasing the power
at the antenna from 1/2 watt to 1 watt or 2 watt gives me a 3 to 6 dB
increase in signal strength, respectively. If the 1/4 wave antenna on the
1/2 watt radio has a 3dB or better gain on both transmit & receive units,
due to better antenna design, I've achieved the same radio performance with
longer battery life, all other things being equal. I guess I'm asking if
there is any information that can help quantify the differences in the two
types of antenna design?

On Wed, 1 Jun 2005 22:49:33 -0400, "Warren" wrote:

The one thing I think I've learned is that three most important components
of a radio are the antenna, the antenna and the antenna.

Hi Warren,

I suspect that if you've been lurking here long enough that, yes, you
may come to that conclusion. Unfortunately, within the scope of
alternatives you have considered, what you write above is simply not
the answer. Yes, it is smacks of a time-honored aphorism drawn from
business or real-estate (not much difference in this new investment
bubble these days); but actually it is the old bottle and not the new
wine that rules in this regard.

In other words it IS and has always BEEN - location, location,
location.

I believe increasing the power
at the antenna from 1/2 watt to 1 watt or 2 watt gives me a 3 to 6 dB
increase in signal strength, respectively. If the 1/4 wave antenna on the
1/2 watt radio has a 3dB or better gain on both transmit & receive units,
due to better antenna design, I've achieved the same radio performance with
longer battery life, all other things being equal. I guess I'm asking if
there is any information that can help quantify the differences in the two
types of antenna design?

A perfectly reasonable question, but location will eclipse these
gains you've researched - many times over. Height is always king of
the mountain. The ability of one antenna to "see" another antenna
trumps all aces, even if both antennas are crummy beyond compare.

Height is also far easier to obtain than the constrained gain you
describe. Hike that antenna ten feet for 10dB gain, or try to limp
along with 3 to 6dB with a huge investment in someone's "state of the
art antenna design?" The numbers will forecast that easily.

How do you get this 10dB? Well, yes, that is more handwaving than
guarantee when nothing has been said of the terrain, or perhaps the
fact you live in the tallest apartment at the top of a hill. The same
spin of the wheel dominates the best antenna money can buy too.

A simple rule at these wavelengths and typical power levels: The
range of your antenna is measured in miles for the square root of
double the height in feet of your antenna. If you have a hand held
and you are standing outside (we will call that at 5 foot), then your
range is 3 miles to the radio horizon. If someone has a similar hand
held (at 5 feet) your combined range (grazing the horizon) is roughly
6 miles. If they are 10 miles away, guess what? Better antennas
might do the trick, but they are bucking the trend.

Now let's raise both those antennas, each to 16 feet (the peak of a
roof of a ranch style house). Your range is 11 miles.

This is simplistic in the extreme, but as a basis of comparison, all
antennas at this frequency share the same results of height advantage.

Now, is this a matter of gain or power? At these frequencies, not
really as long as they are "in the clear" (that is, free of nearby
obstructions and small mountains in that path). Ham radio
communication with handhelds to the Space Shuttle is not a fantasy,
and there we are talking about common antennas, and common powers, at
uncommon distances (a hundred miles or more). Such is the advantage
of that "in the clear" path.

Irrespective of your choice of antenna, the choice of path (if in fact
you have a choice) will dominate results.

73's
Richard Clark, KB7QHC

Thanks Richard,

I certainly can't disagree with your argument about location, but I was
really trying to ask if , in identical environments and all other radio
components being equal does a 1/4 wave antenna give a quantifiable signal
quality advantage over a 2-3 inch antenna. I take it your answer is no.


"Richard Clark" wrote in message
...
On Wed, 1 Jun 2005 22:49:33 -0400, "Warren" wrote:

The one thing I think I've learned is that three most important
components
of a radio are the antenna, the antenna and the antenna.

Hi Warren,

I suspect that if you've been lurking here long enough that, yes, you
may come to that conclusion. Unfortunately, within the scope of
alternatives you have considered, what you write above is simply not
the answer. Yes, it is smacks of a time-honored aphorism drawn from
business or real-estate (not much difference in this new investment
bubble these days); but actually it is the old bottle and not the new
wine that rules in this regard.

In other words it IS and has always BEEN - location, location,
location.

I believe increasing the power
at the antenna from 1/2 watt to 1 watt or 2 watt gives me a 3 to 6 dB
increase in signal strength, respectively. If the 1/4 wave antenna on
the
1/2 watt radio has a 3dB or better gain on both transmit & receive units,
due to better antenna design, I've achieved the same radio performance
with
longer battery life, all other things being equal. I guess I'm asking if
there is any information that can help quantify the differences in the
two
types of antenna design?

A perfectly reasonable question, but location will eclipse these
gains you've researched - many times over. Height is always king of
the mountain. The ability of one antenna to "see" another antenna
trumps all aces, even if both antennas are crummy beyond compare.

Height is also far easier to obtain than the constrained gain you
describe. Hike that antenna ten feet for 10dB gain, or try to limp
along with 3 to 6dB with a huge investment in someone's "state of the
art antenna design?" The numbers will forecast that easily.

How do you get this 10dB? Well, yes, that is more handwaving than
guarantee when nothing has been said of the terrain, or perhaps the
fact you live in the tallest apartment at the top of a hill. The same
spin of the wheel dominates the best antenna money can buy too.

A simple rule at these wavelengths and typical power levels: The
range of your antenna is measured in miles for the square root of
double the height in feet of your antenna. If you have a hand held
and you are standing outside (we will call that at 5 foot), then your
range is 3 miles to the radio horizon. If someone has a similar hand
held (at 5 feet) your combined range (grazing the horizon) is roughly
6 miles. If they are 10 miles away, guess what? Better antennas
might do the trick, but they are bucking the trend.

Now let's raise both those antennas, each to 16 feet (the peak of a
roof of a ranch style house). Your range is 11 miles.

This is simplistic in the extreme, but as a basis of comparison, all
antennas at this frequency share the same results of height advantage.

Now, is this a matter of gain or power? At these frequencies, not
really as long as they are "in the clear" (that is, free of nearby
obstructions and small mountains in that path). Ham radio
communication with handhelds to the Space Shuttle is not a fantasy,
and there we are talking about common antennas, and common powers, at
uncommon distances (a hundred miles or more). Such is the advantage
of that "in the clear" path.

Irrespective of your choice of antenna, the choice of path (if in fact
you have a choice) will dominate results.

73's
Richard Clark, KB7QHC