Transmitter power questions.....

[Bill Glaze]

I have no idea why they want those items listed; probably they wanted 
additional info that the writer was able to supply.  I would be more 
interested in the frequencies and harmonic suppression than the listed 
questions.  But I answered what the writer wanted to know.  Bill Glaze

Bob Richards wrote:

>I'll echo most of what you say, Bill.
>
>I've seem to remember that the power was limited to 1
>watt into the final output stage. Actual power
>delivered to the antenna will be less than 750mW.
>
>I have also heard that someone once measured the
>output power of their transmitter by connecting a
>regular power sensor in place of the antenna, and they
>measured 200 or 250 mW, but I don't think that is the
>proper way to measure it. A standard power sensor
>usually has a 50 ohm impedance, which may not be
>anything close to the actual impedance of a whip
>antenna, so they won't be measuring the actual power
>from the output stage.
>
>Gain? I have no clue. Gain is relative to an isotropic
>radiator (radiates equally in all directions) which is
>theoretical based on the power delivered to the
>antenna. The only way an antenna can have gain is if
>it radiates more in one (or more) directions more than
>in others. Think of an isotropic radiator as a light
>bulb, and an antenna with gain as a light bulb placed
>in a reflector. The more focused the beam, the higher
>the gain, but less light will be radiated outside the
>beam (lobe). For our purposes, we don't want a high
>gain antenna, since we could end up with a null signal
>in some directions.
>
>The best way to figure the gain (if any) of our
>systems would be to make EIRP or EDRP measurements
>(Effective Isotropic or Dipole Radiated Power) with a
>field measurement system, correlated to a calibrated
>antenna. I've done this for cell phones and wireless
>devices, but never one of our transmitters. (Never had
>the time). IMHO, it might not be a very repeatable or
>meaningful test since, in normal use, we will be
>holding the radio at ??? angle to the ground. Who
>wants to stand still on a turntable holding a
>transmitter for the time it would take to make the
>measurements at all different angles? :-) You could
>place the radio on a table, but that would not be real
>world.
>
>Polarization? Depends some on the angle the antenna is
>held, though I suspect it might be mostly vertical.
>
>I'm curious why they want all of this information? I
>would think they would only need to know the
>frequency, bandwidth, and radiated power.
>
>Bob R.
>
>
>
>--- Bill Glaze <billglaze at triad.rr.com> wrote:
>  
>
>>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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