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Abdul Ahad

Jan 1, 1970
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Hi,
Can someone please tell me which component to adjust/change to
increase the range of my 40 MHz transmitter for my remote control car?
I want to know which BIT inside the transmitter to tamper with...
(Don't tell me to use a signal booster or better antenna at the
receiving end, I don't want to do this - I want to boost the
transmitter.)

Thanks
AA
http://uk.geocities.com/aa_spaceagent/
 
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Dr. Anton Squeegee

Jan 1, 1970
0
Abdul Ahad said:
Hi,
Can someone please tell me which component to adjust/change to
increase the range of my 40 MHz transmitter for my remote control car?
I want to know which BIT inside the transmitter to tamper with...
(Don't tell me to use a signal booster or better antenna at the
receiving end, I don't want to do this - I want to boost the
transmitter.)

Before you consider doing this, you should do some research.
Specifically, you need to check with whichever agency in the UK performs
the same function as the FCC. Specifically, check what the power limits
are for RC stuff. You could easily end up in deep kimchee if you exceed
that limit and you get caught.
 
Before you consider doing this, you should do some research.
Specifically, you need to check with whichever agency in the UK performs
the same function as the FCC. Specifically, check what the power limits
are for RC stuff. You could easily end up in deep kimchee if you exceed
that limit and you get caught.

According to the Radiocommunications Agency,
http://www.radio.gov.uk/topics/spectrum-strat/uk-fat/annex-b2002.doc

The limit is 100mW (ERP), which is probably what you're outputting.
Plus the primary user of the frequency is the Ministry of Defence.

Simon
 
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Abdul Ahad

Jan 1, 1970
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According to the Radiocommunications Agency,
http://www.radio.gov.uk/topics/spectrum-strat/uk-fat/annex-b2002.doc

The limit is 100mW (ERP), which is probably what you're outputting.
Plus the primary user of the frequency is the Ministry of Defence.

Simon


O.K. I appreciate the legalities and restrictions on transmitter power
imposed by government thanks for your information. But I am a "space"
man with many un-Earthly applications in mind! What if... you were
stranded on the Moon or on a space station hundreds of miles out in
space and your life depended on boosting the transmission power of
your "local" radio - designed for communications only with your
immediate space/moon based colleagues - so that you could send a
message to ground control on Earth for a rescue mission? In that
situation, I doubt if anyone would give a toss about the FCC or other
bodies!?

I just want to know: do you adjust the CRYSTAL, do you change the
FERRITE ROD or COIL or do you change another component that dictates
the output power and the ultimate range of the transmitted signal?

RSVP - I'm stranded on the lunar surface...!
AA
http://uk.geocities.com/aa_spaceagent/
 
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Andrew Howard

Jan 1, 1970
0
Sometimes on transmitters, there are resistors which connect to the the
antenna to cut down the signal, maybe changing those might do something. (I
have no idea)
Just don't blame me if something goes bad... :)

Andrew Howard
 
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Fred Abse

Jan 1, 1970
0
the amount it receives is probably reduced in accordance with the square
of the distance.

The _power density_ (watts per square meter) decreases as the square of
the distance, but the _field strength_ (volts per meter) decreases as the
first power of the distance.

It's volts per meter at the receiving antenna that matters.
 
T

Terry

Jan 1, 1970
0
Fred said:
The _power density_ (watts per square meter) decreases as the square of
the distance, but the _field strength_ (volts per meter) decreases as the
first power of the distance.

It's volts per meter at the receiving antenna that matters.

Thanks Fred. I had some dimly half remembered formula that it had
something to do with the square of the distance; many things it
seems have to do with the square or sq. root of things! Also I
was too lazy to even remember where to look it up!
What I was trying to help Abdul with was the idea that even IF he
was able to successfully double the output power of his RCC
transmitter it would probably have little effect! If his plane or
model, whatever, went a few yards further away the signal would
be just as weak as before the power increase. etc.
Also; in these suspicious times it might be wise, especially if
one is not an 'electronically skilled person' to NOT tamper with
something that may have regulatory authority (FCC in the US)
approval? Terry.
 
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Abdul Ahad

Jan 1, 1970
0
Terry said:
Abdul had written about increasing the power output of a Radio
Control transmitter;



Abdul this group seems to agree; there is no one component that
can be pointed to to increase the output power. A complete
redesign of your units circuit would have to be looked at.

Even though under conditions in previous wars some incredibly
ingenious electronic things were done they were usually by people
who had extensive knowledge and/or experience. Just for one
example; there was the term 'Fox hole radio', which was basically
a simple detector that without batteries could receive very
strong broadcasts. Servicemen and prisoners of war used things
such as the impurity in a piece of coal and the point from a
broken razor blade to make what was then called a 'crystal
detector'. Not the same thing at all as the crystals used in a
transmitter.

It might be possible, and quite likely illegal (although the US
FCC or any other nations regulatory agency, including the United
Nations, probably don't have any jurisdiction on the moon!), to
feed the output of your radio control transmitter into a 'booster
amplifier'. Such a booster might be powered by 12 volts; so you
could use a car battery or several lantern batteries to power it.
These would be heavy and bulky.

In a unit such as yours the crystal determines the
frequency/wavelength of the transmission; don't mess with it. It
does not directly affect the amount of power output. To obtain
the the power output that your unit is designed for, the basic
frequency inside is probably 'amplified' (are you familiar with
that term?) by transistors. Those transistors require battery
power. If your unit is limited to 100 milliwatts as suggested as
typical and legal in many countries for RCC (Radio Control) and
you WERE able to increase the output power those batteries would
have to supply a lot more power. I would suggest to you that that
to achieve any significant increase in performance you would have
to at least quadruple (times 4) the output power. Even then as
the distance to the model plane, or whatever increases, the
amount it receives is probably reduced in accordance with the
square of the distance. In other words twice the distance would
require at least four times the signal. Four times the distance
would require sixteen times the power etc. Could you install a
more sensitive receiver in the model/plane? Use a better antenna
on either the model or the transmitter?

Finally I would observe that there are good safety reasons for
the power to be limited for RCC. A similar example might be that
one does not use cell phones, also of low power, in certain areas
such as hospitals to avoid interference with medical equipment.
Another example is that one is advised to turn off all radio
transmissions when entering an area where a construction company
is blasting/using dynamite etc. or where explosives are.

Under the present concerns about 'Security' in many countries due
to terrorism etc. it might NOT be a good thing to go messing
around with a RCC unit since in the wrong context it might be
misconstrued as an attempt control something more dangerous than
a model plane or even to use the model itself to cause damage?
Just a suggestion anyway.

By the way I don't think planes, model or otherwise, can fly on
the moon? Wrong kind of atmosphere! Hope you get home safely.

Terry.



Yes, I think I understand the technical intricacies involved here...
but just one more question: If the radio signals from my 40 MHz model
transmitter are expected to stay weak no matter how much the power
amplification, then how do we expect the alien recepients (if any) of
the 1974 Arecibo Radio Telescope message to respond back???

For those of us not familiar with this, an interstellar radio message
was sent to Messier 13, a globular star cluster in the constellation
of Hercules, on November 16, 1974, from the Arecibo Radio Observatory
in Puerto Rico. As M13 is 24,000 light years from Earth, and radio
signals travel at the speed of light, it will take 24,000 years for
the message to reach the star cluster.

Abdul Ahad
http://uk.geocities.com/aa_spaceagent/
 
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