On Sun, 02 May 2004 09:04:33 -0500, John Fields
wrote:

On Sun, 02 May 2004 14:09:44 +0100, Paul Burridge
wrote:

On Sat, 1 May 2004 15:30:18 -0400, "Ralph Mowery"
wrote:

The generators are more of a voltage source. They will deliver their rated
output when loaded to the proper impedance. Load it with 50 ohms and see if
it gives the rated output. If not try 70 ohms, or another value. One of
the reasons for using a 6 db pad is that it helps isolate the impedance of
the generator and receiver.

My main sig gen states "output EMF using 6dB pad" next to the socket.
WTF is a "6dB pad"?

---
A 6dB attenuator.

---
Also, less commonly, a device used to match the impedance of a
generator to the impedance of a transmission line or a load, or the
impedance of a transmission line to the impedance of a load.

The impedance of the generator, line, and/or load are assumed to be
purely resistive, and there is always loss associated with the
transformation. Devices which exhibit the least loss are called
"minimum loss pads", and

http://www.maxim-ic.com/appnotes.cfm/appnote_number/972

gives a good description of the process involved in designing one.

The reference given to Bruno Weinschel and the ITT handbook (as we
old-timers call it) is particularly good, and if you're interested in
RF (or just about anything else...) and you can buy a copy of it you
should.

BTW, since a pad is usually rated in terms of the power it's supposed
to lose between its input and its output, the reference to "output
EMF" on your generator may be what it supposed to be with a 3dB pad on
its output.

Easy way to find out would be to build a 3dB and a 6dB pad to find
out. For a 50 ohm tee pad, here are the resistor values you'll need
for -3dB:

0dBIN--[8.55]-+-[8.55]---3dBOUT
|
[141.93]
|
GND-----------+-----------GND


and for -6dB:

0dBIN--[16.61]-+-[16.61]---3dBOUT
|
[66.93]
|
GND------------+-----------GND

The input goes directly to your generator, (assuming its output
impedance is 50+j0 ohms) a 50 ohm resistor gets connected across the
output of the pad, and you'll measure the voltage across the 50 ohm
resistor.

Use non-inductive resistors (carbon comp if you can get them) and keep
the leads short. That is, ********KEEP THE LEADS SHORT*********.

--
John Fields

On Sun, 02 May 2004 11:35:08 -0500, John Fields wrote:

On Sun, 02 May 2004 09:04:33 -0500, John Fields
wrote:

snip John helping Paul with terminology

http://www.maxim-ic.com/appnotes.cfm/appnote_number/972

Once in a while, I can post a helpful link (I've got plenty of tech
info links, but most don't usually apply to the topic at hand
whatever that may be) , but some of you guys, like Spehro, You,
etc., ... it's like you can pull horshoe out of yer asses You
must do more digging than I do.

I got a kick out of this link because I have the opposite situation.
I don't need an MLP becuse I have an SLM tha *is* 75 ohfriggin'megas
and the link dealt with ... you know.

snip John still helping but going the extra furlong or so

Use non-inductive resistors (carbon comp if you can get them) and keep
the leads short. That is, ********KEEP THE LEADS SHORT*********.
^^^^^^^^^^
advice that should be unsnipped. Er, snip the leads, though.

--
Best Regards,
Mike

On Sun, 02 May 2004 11:35:08 -0500, John Fields wrote:

On Sun, 02 May 2004 09:04:33 -0500, John Fields
wrote:

snip John helping Paul with terminology

http://www.maxim-ic.com/appnotes.cfm/appnote_number/972

Once in a while, I can post a helpful link (I've got plenty of tech
info links, but most don't usually apply to the topic at hand
whatever that may be) , but some of you guys, like Spehro, You,
etc., ... it's like you can pull horshoe out of yer asses You
must do more digging than I do.

I got a kick out of this link because I have the opposite situation.
I don't need an MLP becuse I have an SLM tha *is* 75 ohfriggin'megas
and the link dealt with ... you know.

snip John still helping but going the extra furlong or so

Use non-inductive resistors (carbon comp if you can get them) and keep
the leads short. That is, ********KEEP THE LEADS SHORT*********.
^^^^^^^^^^
advice that should be unsnipped. Er, snip the leads, though.

--
Best Regards,
Mike

On Sun, 02 May 2004 09:04:33 -0500, John Fields
wrote:

On Sun, 02 May 2004 14:09:44 +0100, Paul Burridge
wrote:

On Sat, 1 May 2004 15:30:18 -0400, "Ralph Mowery"
wrote:

The generators are more of a voltage source. They will deliver their rated
output when loaded to the proper impedance. Load it with 50 ohms and see if
it gives the rated output. If not try 70 ohms, or another value. One of
the reasons for using a 6 db pad is that it helps isolate the impedance of
the generator and receiver.

My main sig gen states "output EMF using 6dB pad" next to the socket.
WTF is a "6dB pad"?

---
A 6dB attenuator.

---
Also, less commonly, a device used to match the impedance of a
generator to the impedance of a transmission line or a load, or the
impedance of a transmission line to the impedance of a load.

The impedance of the generator, line, and/or load are assumed to be
purely resistive, and there is always loss associated with the
transformation. Devices which exhibit the least loss are called
"minimum loss pads", and

http://www.maxim-ic.com/appnotes.cfm/appnote_number/972

gives a good description of the process involved in designing one.

The reference given to Bruno Weinschel and the ITT handbook (as we
old-timers call it) is particularly good, and if you're interested in
RF (or just about anything else...) and you can buy a copy of it you
should.

BTW, since a pad is usually rated in terms of the power it's supposed
to lose between its input and its output, the reference to "output
EMF" on your generator may be what it supposed to be with a 3dB pad on
its output.

Easy way to find out would be to build a 3dB and a 6dB pad to find
out. For a 50 ohm tee pad, here are the resistor values you'll need
for -3dB:

0dBIN--[8.55]-+-[8.55]---3dBOUT
|
[141.93]
|
GND-----------+-----------GND


and for -6dB:

0dBIN--[16.61]-+-[16.61]---3dBOUT
|
[66.93]
|
GND------------+-----------GND

The input goes directly to your generator, (assuming its output
impedance is 50+j0 ohms) a 50 ohm resistor gets connected across the
output of the pad, and you'll measure the voltage across the 50 ohm
resistor.

Use non-inductive resistors (carbon comp if you can get them) and keep
the leads short. That is, ********KEEP THE LEADS SHORT*********.

--
John Fields

My main sig gen states "output EMF using 6dB pad" next to the socket.
WTF is a "6dB pad"?
--

A pad is usually 3 resistors in a small container. They can be a T or a Pi
type. This is the way the resistors are configured in the pad. You may
also see them referred to as an attenuator. The number 6 db is how much the
pad reduces the signal in power. You can get them from about .5 db to 20
db. They have to be used for the impedance they are rated at. They are for
reducing the signal level and also to help isolate small differences in
impedance.
For the calibration to be accurate on your generator it sounds like the
scale is calibrated so you need the 6 db pad after it. A 5 db pad will
reduce the power by a factor of 4 or a voltage by a factor of 2.

"Ralph Mowery" wrote in message
...
My main sig gen states "output EMF using 6dB pad" next to the socket.
WTF is a "6dB pad"?
--

[...snip...]
For the calibration to be accurate on your generator it sounds like the
scale is calibrated so you need the 6 db pad after it. A 5 db pad will
reduce the power by a factor of 4 or a voltage by a factor of 2.

That last 5 should be a 6.

--
Steve N, K,9;d, c. i My email has no u's.

[...snip...]
For the calibration to be accurate on your generator it sounds like the
scale is calibrated so you need the 6 db pad after it. A 5 db pad will
reduce the power by a factor of 4 or a voltage by a factor of 2.

That last 5 should be a 6.

--
Steve N, K,9;d, c. i My email has no u's.

Thanks, I fat fingered that and hit the 5 instead of the 6.

[...snip...]
For the calibration to be accurate on your generator it sounds like the
scale is calibrated so you need the 6 db pad after it. A 5 db pad will
reduce the power by a factor of 4 or a voltage by a factor of 2.

That last 5 should be a 6.

--
Steve N, K,9;d, c. i My email has no u's.

Thanks, I fat fingered that and hit the 5 instead of the 6.

"Ralph Mowery" wrote in message
...
My main sig gen states "output EMF using 6dB pad" next to the socket.
WTF is a "6dB pad"?
--

[...snip...]
For the calibration to be accurate on your generator it sounds like the
scale is calibrated so you need the 6 db pad after it. A 5 db pad will
reduce the power by a factor of 4 or a voltage by a factor of 2.

That last 5 should be a 6.

--
Steve N, K,9;d, c. i My email has no u's.

On Sun, 02 May 2004 14:09:44 +0100, Paul Burridge
wrote:

On Sat, 1 May 2004 15:30:18 -0400, "Ralph Mowery"
wrote:

The generators are more of a voltage source. They will deliver their rated
output when loaded to the proper impedance. Load it with 50 ohms and see if
it gives the rated output. If not try 70 ohms, or another value. One of
the reasons for using a 6 db pad is that it helps isolate the impedance of
the generator and receiver.

My main sig gen states "output EMF using 6dB pad" next to the socket.
WTF is a "6dB pad"?

---
A 6dB attenuator.

--
John Fields