Help in identifying the schematic symbol

[whompah]

http://electronics-diy.com/tx200.php

Hello there, this circuit seems interesting and I wanted to simulate and construct it, but the problem is I do not know what do the 3 symbols in the circuit represent (1 in audio input, 1 in the middle, and 1 at the antenna). I have never come across with these symbols before.

Can someone lend a little help here ? appreciate that

 

[CocaCola]

The symbol on the input and output is a coaxial connector... Not sure why they have one in the middle, unless there is a secondary tap for some reason...

 

[whompah]

Yes, in the middle part, the wire shouldn't be connecting to the ground. Middle part confuses me a lot

 

[CocaCola]

Yes, in the middle part, the wire shouldn't be connecting to the ground. Middle part confuses me a lot

It's not, IMO it's showing that another 'connector' or take off could be installed at that point for some reason... If you do not require that take off, just consider it a non-connection like this...

 

[whompah]

I see. THANK YOU VERY MUCH !!!
I will try to simulate that now.

 

[KrisBlueNZ]

The one in the middle might indicate a feedthrough through a metal shield wall between the two parts of the circuit.

 

[davenn]

The one in the middle might indicate a feedthrough through a metal shield wall between the two parts of the circuit.

My thoughts exactly, Kris

very common in RF circuits to stop feedback. They have just represented it poorely

Dave

 

[whompah]

But in simulation, can I represent it this way ?

And also, in constructing the circuit physically, 1st stage (modulator) and 2nd stage (amplifier) should be seperated from each other by a metal plate right, but physically connected by a wire without using co-axial cable as shown in the figure above ?

 

[KrisBlueNZ]

The circuit is probably meant to be constructed in a metal (steel) box or rectangular tube. The metal is the circuit ground. You place a steel sheet with a hole in it between the two sections of the circuit, and solder it to the metal on three sides (the fourth side is formed by the clip-on steel cover), and feed the signal through the hole, using insulation, or a ceramic tube, to insulate the wire so it can't make contact with the plate.

You can also get complete feedthrough components that you solder to the hole, which have a connection on each side. Open up a TV tuner or modulator; you may see something similar.

I haven't ever seen coax cable used for the feedthrough.

 

[davenn]

The circuit is probably meant to be constructed in a metal (steel) box or rectangular tube. The metal is the circuit ground. You place a steel sheet with a hole in it between the two sections of the circuit, and solder it to the metal on three sides (the fourth side is formed by the clip-on steel cover), and feed the signal through the hole, using insulation, or a ceramic tube, to insulate the wire so it can't make contact with the plate.

......................

I haven't ever seen coax cable used for the feedthrough.

yeah, .... more commonly its just a semicircular notch cut out of the metal shiels so that the PCB track passes though

Dave

 

[davenn]

But in simulation, can I represent it this way ?

And also, in constructing the circuit physically, 1st stage (modulator) and 2nd stage (amplifier) should be seperated from each other by a metal plate right, but physically connected by a wire without using co-axial cable as shown in the figure above ?

yes simulate it that way as shown with no connections at those points

as i said in my previous post, its normally just a PCB track passing through a notch cut out of the metal shield

will see if I can find an example pic for you

Dave

 

[davenn]

OK in this pic from my collection of RF gear, there are 2 places in the metal wall where the RF paths move from section to section....
one on the bottom right and one on the left wall

now just remember and for clarification....
You CANNOT use feedthrough capacitors to pass RF. The whole idea of feedthrough caps is to stop the passage of RF
In the image above there is a feedthrough cap on the right hand side metal wall bringing DC into that section. The feedthroough cap stops RF leaveing via the DC feedline


cheers
Dave

 

[CocaCola]

A poor way to represent that on a schematic, although to be fair if it was for a repair manual or service manual representing the connection that way would have been obvious to the person upon first glance of the physical circuit, so in that case representation isn't all important...

 

[davenn]

a metal screen is normally indicated by using a dashed line eg....

Dave

 

[CDRIVE]

OK in this pic from my collection of RF gear, cheers
Dave

Now that's an RF enclosure! Very mil spec-esc.

Chris