Transmitter power questions.....

RC Steve Sterling rcsteve at tcrcm.org
Tue Apr 12 21:24:16 AKDT 2005 

I sure was yelling though!! Its interesting how I could control it when I
got it back closer  to my flight line. The plane didn't start reacting until
I was in the turn-around maneuver closest to the other flight line. As long
as I could get it somewhat closer to me than the other flightline, I could
get pretty good control.

It goes to show that in a two transmitter situation, you only need a
slightly stronger signal. With the modern receivers, they lock onto
strongest signal pretty well. In the old AM days, a very weak 2nd
transmitter would still create enough beat frequency interference to screw
things up. FM (or PCM which is still a frequency shift modulation)is much
more tolerant, thankfully.


-----Original Message-----
From: discussion-request at nsrca.org
[mailto:discussion-request at nsrca.org]On Behalf Of Michael Lance
Sent: Tuesday, April 12, 2005 8:14 PM
To: discussion at nsrca.org
Subject: RE: Transmitter power questions.....


I remember that "situation", Steve.  All of us witnesses were amazed
that you realized the issue, didn't over control and got your bird back
close enough to yourself to overcome the interference.  The whole
sequence of events must have lasted close to a minute.

Amazing recognition of the problem and cool response; not sure how you
managed it.

MIke

-----Original Message-----
From: discussion-request at nsrca.org [mailto:discussion-request at nsrca.org]
On Behalf Of RC Steve Sterling
Sent: Tuesday, April 12, 2005 4:05 PM
To: discussion at nsrca.org
Subject: RE: Transmitter power questions.....

bare light bulb is pretty close analogy.  Point source radiating in a
sphere
is the real definition.

A dipole actually has flux lobes and concentrates the radiated power
perpendicular (sorta) to the antenna, with nulls off the ends. Thus
dipoles
have that 2.1 db gain (theorically) over an isotropic source, because
they
concentrate more of the power broadside to the antenna. Although the
antennas on our transmitters are probably closer to being 1/4 wave whips
(still sorta a dipole), they don't have much energy coming off the
pointy
end. Still plenty to fly with in the normal situation. But if you ever
get
in a a weak signal or interference situation, holding the antenna
broadside
to airplane should raise the signal by several db. Helped me once in a
two
transmitters on situation.

-----Original Message-----
From: discussion-request at nsrca.org
[mailto:discussion-request at nsrca.org]On Behalf Of John Ferrell
Sent: Tuesday, April 12, 2005 11:39 AM
To: discussion at nsrca.org
Subject: Re: Transmitter power questions.....


That sounds familiar.
I have always thought of isotropic being like a bare light bulb
radiating
energy.

BTW, Bill & I defied fate again yesterday and flew all afternoon under
the
dreaded towers at CCRC....

John Ferrell
http://DixieNC.US

----- Original Message -----
From: "Bob Richards" <bob at toprudder.com>
To: <discussion at nsrca.org>
Sent: Tuesday, April 12, 2005 11:40 AM
Subject: Re: Transmitter power questions.....


> John,
>
> IIRC, the relationship between dipole and isotropic is
> about 2.1 dB.
>
> Now that you mention it, they probably run site
> surveys to check for unauthorized transmissions and
> that is why they want to know as much information
> about the expected transmissions from on-base.
>
> Bob R.
>
> --- John Ferrell <johnferrell at earthlink.net> wrote:
>> The antenna gain is less than 1 dbd. The last "d"
>> means as compared to a reference dipole. If needed,
>> I will review an antenna book for the relationship
>> to a "dbi" which is isotropic.
>>
>> The polarization is not consistent since a hand held
>> whip antenna less than a quarter wave is being used.
>>
>> The ground to air range is so low that the systems
>> can operate two miles apart without interfering with
>> each other. Since all of the equipment is handheld
>> and battery powered, no one is especially interested
>> in using the maximum legal power level.
>>
>> BTW, IMHO, their vigilance in the matter of nearby
>> radio transmissions is commendable in these
>> unsettled time.
>>
>> John Ferrell
>> http://DixieNC.US
>>
>>   ----- Original Message -----
>>   From: Bill Glaze
>>   To: discussion at nsrca.org
>>   Sent: Monday, April 11, 2005 8:35 PM
>>   Subject: Re: Transmitter power questions.....
>>
>>
>>   I can answer a few:
>>   Transmitter power:  1 watt maximum.  Actual,
>> really about 200 milliwatts
>>   Transmitter radius is difficult, because you need
>> to have an effective Field Strength Meter, but I
>> have successfully operated an airplane's controls at
>> 1.1 miles, (line of sight) but I didn't intend to
>> fly; I couldn't even have seen the airplane.
>>   Antenna used: Vertical Whip (Normally; that's
>> what's supplied)
>>   Antenna gain; I don't really know the answer to
>> that one.
>>   Polarization:  Vertical  (which is normal form a
>> whip antenna.)
>>
>>   bravo52 wrote:
>>
>>     Hey Guys,
>>       I am working on a project to get RC on my Air
>> Force Base and they have a few questions........
>> Can anybody answer these questions for me given a
>> standard Futaba or JR radio?
>>
>>     1. What is the transmitter power?
>>     2. What is the radius the transmitter will
>> operate effectively? Consider miles not
>> Line-of-sight. (I guess that depends on #1)
>>     3.  What type of transmit antenna will be used,
>> e.g., parabolic, whip, telescoping single pole, ect?
>>     4.  What is the transmitter antenna gain?
>>     5.  How is the transmit antenna polarized, e.g.,
>> horizontal, vertical, etc.?
>>
>>     TAI
>>     v/r
>>     Jerry L.
>>
>>     P.S. I tried to call Tony at RS but he left
>> early...............hmmm.......was he at the field????
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