How do u measure the load resistance of a antenna ?

[aj_silverthunder]

antenna

friends how do u measure the load resistance of a antenna
and which type of antenna has resistance of 75Ohms

 

[biff44]

Re: antenna

what type of electronic test gear do you have access to? What frequency is the antenna?

 

[aj_silverthunder]

antenna

100mhz

 

[aj_silverthunder]

antenna

a dipole antenna can offer 75ohm impedance

 

[aj_silverthunder]

guys please explain me how do u calculate the drain-source voltage of Jfet.

 

[aj_silverthunder]

what is the base emitter voltage of the first transistor in this schematic " https://sub.allaboutcircuits.com/images/quiz/01587x01.png "please explain in detail please ,thank u in advance.

 

[betwixt]

It is the same voltage as you get on any forward biased NPN transistor.

What has this got to do with antenna impedance?

Brian.

 

[snafflekid]

what is the base emitter voltage of the first transistor in this schematic " https://sub.allaboutcircuits.com/images/quiz/01587x01.png "please explain in detail please ,thank u in advance.

The 220k and 27k form a voltage divider. Since 9V is applied to the top, ~1V will appear on the base. 1V is more than enough to turn on the base of the transistor, so current will flow through the emitter and into the 1.5k. The base emitter voltage is going to be the ~1V minus the voltage on the 1.5k resistor. We know that it takes approximately 0.65V to turn on a npn. So we are left with 0.35V on the 1.5k. Thus about 233uA are flowing through the 1.5k resistor. This is a preliminary analysis and exact numbers require simulation.

 

[aj_silverthunder]

guys what is transition frequency.
for example i have 2N3019 transistor,its transition frequency is 100Mhz,can i use it to amplify RF signals below 100Mhz.please help me out.

 

[betwixt]

It's the frequency at which the gain falls to 1.

You normally work at frequencies well below transition frequency so it can be ignored in gain calculations. As you get close to it, the gain falls and normal 'DC' calculations become increasingly inaccurate.

As a rule of thumb, use an FT several times higher than the highest frequency you want to amplify.

Brian.

 

[aj_silverthunder]

so then if i need to amplify a RF signal of 100Mhz then can i use a transistors (transition frequency) of 175Mhz to 600Mhz.

Added after 51 minutes:

can u please tell me how do u calculate the Vcbo of this circuit.
as simulated,it shows voltage @ collector is 30V
and voltage at base is 2V
can u please tell me how can i know the Vcbo of the transistor.