How to reduce two-way radio's power output?
 

Nowadays two-way radios are getting more and more powerful, coverage
up to 8, 10 12 or more miles. Ironically, it is even harder to buy one
with only 2-mile distance.

I want to use a two radio just for short distance, for example, only
within 1000 feet. How to modify the circuit (generally speaking) so I
can extend the radio's powerful consumption? As I do not need it to
communicate for longer distance, I want it to reduce power output, so
I can use it for longer time. I know it is difficult to illustrate
without a schematics, but just in general terms, what kind of options
or in what areas can I do the modification?

One of my applications is to use 2-way radio as baby monitor for
longer distance than normal baby monitor does.

How to reduce two-way radio's power output?
 

On May 12, 2:11?pm, wrote:
Nowadays two-way radios are getting more and more powerful, coverage
up to 8, 10 12 or more miles. Ironically, it is even harder to buy one
with only 2-mile distance.

I want to use a two radio just for short distance, for example, only
within 1000 feet. How to modify the circuit (generally speaking) so I
can extend the radio's powerful consumption? As I do not need it to
communicate for longer distance, I want it to reduce power output, so
I can use it for longer time. I know it is difficult to illustrate
without a schematics, but just in general terms, what kind of options
or in what areas can I do the modification?

One of my applications is to use 2-way radio as baby monitor for
longer distance than normal baby monitor does.

The simplest modification is an attenuator pad between In/Out
and the antenna. If you have a "one-piece" FRS HT such as
the little Motorola my wife and I use at home, it is difficult to
wedge one in there. An alternative in that case is to use a
piece of conducting foam (typically for storage of CMOS digital
devices) to sit over the antenna stub. One has to experiment
with the size of the block of plastic foam.

A drawback to using an HT is the power drain on the internal
battery and forcing the PTT button into transmit all the time.
That will eat up battery charges and an external power source
would be needed. However, always on transmit can cause
interference to other users on that FRS channel and is a legal
no-no. It would be better to just get an old 49 MHz baby
monitor and use that directly.

73, Len AF6AY

How to reduce two-way radio's power output?
 

On Sat, 12 May 2007 15:24:24 -0700, AF6AY wrote:
On May 12, 2:11?pm, wrote:
Nowadays two-way radios are getting more and more powerful, coverage
up to 8, 10 12 or more miles. Ironically, it is even harder to buy one
with only 2-mile distance.

I want to use a two radio just for short distance, for example, only
within 1000 feet. How to modify the circuit (generally speaking) so I
can extend the radio's powerful consumption? As I do not need it to
communicate for longer distance, I want it to reduce power output, so
I can use it for longer time. I know it is difficult to illustrate
without a schematics, but just in general terms, what kind of options
or in what areas can I do the modification?
...
The simplest modification is an attenuator pad between In/Out
and the antenna. If you have a "one-piece" FRS HT such as
the little Motorola my wife and I use at home, it is difficult to
wedge one in there. An alternative in that case is to use a
piece of conducting foam (typically for storage of CMOS digital
devices) to sit over the antenna stub. One has to experiment
with the size of the block of plastic foam.

I think his point is that he's trying to reduce transmitter output power
to conserve battery life - of course, an attenuator pad isn't going to
accomplish that.

Probably the "easiest" way to accomplish this would be to bypass the final
amplifier stage, passing its drive signal directly to the final filter,
and from there to the antenna. I would suggest this would be nearly
impossible to accomplish without a schematic - and not particularly easy
even with it.

I wonder if the best route would be to use a regular baby monitor
transmitter - but use a better receiver and/or receiving antenna? Like a
decent scanner, possibly with an attic antenna. This method is easy to
accomplish even for someone without electronics experience, and
unquestionably legal, unlike many other alternatives.

How to reduce two-way radio's power output?
 

Locate the trace that feeds switched battery voltage to the final
transmitting stage. Cut this trace somewhere between the transmit switching
circuit and the final amp stage. Insert a few rectifier-type diodes (1N400x)
in series across the cut point. Each diode in series will lower the voltage
to the final amp stage about .7V or so. For each halving of voltage to the
final stage, the output power (and consequently the power load on the
battery) will drop by 4:1. All of this assumes that the final amplifier is
well-behaved under reduced voltage conditions, which should be true but is
not guaranteed.

Joe
W3JDR

wrote in message
ups.com...
Nowadays two-way radios are getting more and more powerful, coverage
up to 8, 10 12 or more miles. Ironically, it is even harder to buy one
with only 2-mile distance.

I want to use a two radio just for short distance, for example, only
within 1000 feet. How to modify the circuit (generally speaking) so I
can extend the radio's powerful consumption? As I do not need it to
communicate for longer distance, I want it to reduce power output, so
I can use it for longer time. I know it is difficult to illustrate
without a schematics, but just in general terms, what kind of options
or in what areas can I do the modification?

One of my applications is to use 2-way radio as baby monitor for
longer distance than normal baby monitor does.

How to reduce two-way radio's power output?
 

How to reduce two-way radio's power output?
 

"W3JDR" wrote in message
news:hgD1i.6186$1X1.1174@trndny02...
Locate the trace that feeds switched battery voltage to the final
transmitting stage. Cut this trace somewhere between the transmit
switching circuit and the final amp stage. Insert a few rectifier-type
diodes (1N400x) in series across the cut point. Each diode in series will
lower the voltage to the final amp stage about .7V or so. For each halving
of voltage to the final stage, the output power (and consequently the
power load on the battery) will drop by 4:1. All of this assumes that the
final amplifier is well-behaved under reduced voltage conditions, which
should be true but is not guaranteed.

Joe
W3JDR

wrote in message
ups.com...
Nowadays two-way radios are getting more and more powerful, coverage
up to 8, 10 12 or more miles. Ironically, it is even harder to buy one
with only 2-mile distance.

I want to use a two radio just for short distance, for example, only
within 1000 feet. How to modify the circuit (generally speaking) so I
can extend the radio's powerful consumption? As I do not need it to
communicate for longer distance, I want it to reduce power output, so
I can use it for longer time. I know it is difficult to illustrate
without a schematics, but just in general terms, what kind of options
or in what areas can I do the modification?

One of my applications is to use 2-way radio as baby monitor for
longer distance than normal baby monitor does.




A lot of the time both the final and the driver are fed from the same source
so just one diode may have a considerable effect.

Jimmie

How to reduce two-way radio's power output?
 

"Doug Smith W9WI" wrote in message
.. .

I wonder if the best route would be to use a regular baby monitor
transmitter - but use a better receiver and/or receiving antenna? Like a
decent scanner, possibly with an attic antenna. This method is easy to
accomplish even for someone without electronics experience, and
unquestionably legal, unlike many other alternatives.

Unless the OP intends to use it for covert evesdropping, hence the plan to
make the battery last longer. 1000 feet is a long way for a baby monitor to
be needed that would be on the next block in most cities.

Asking in an amatuer radio newsgroup (where the goal is often increasing the
range not decreasing it) might not be the best source of info.
thanks, John.
KC5DWD