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ON TOPIC ! A quick brain teaser.

E

Eeyore

Jan 1, 1970
0
The strain gauge thread reminded me of a product with an 'issue' I was once
asked to take a look at.

It was the receiver section of a marine radar.

The detector was followed by several variable gain stages. These were wideband
IC amplifiers made by Ferranti ( now Zetex ) with a control current / voltage
that varied each IC's gain over about something like a 12-15dB range. The
control ports were driven in parallel so that gain was swept equally between all
the devices.

They were at least 6 of these cascaded to provide the necessary gain before the
signal went off for further processing.

After the pulse was transmitted ( and the receiver input clamped ) the gain was
ramped up with a triangle waveform to provide the necessary low gain for near
targets and higher gain for distant targets.

I took one look at the schematic, grinned and said I could fix it.

What problems ( not less than 2 of them ) were they encountering ?

Graham
 
F

Frank Bemelman

Jan 1, 1970
0
Eeyore said:
The strain gauge thread reminded me of a product with an 'issue' I was
once
asked to take a look at.

It was the receiver section of a marine radar.

The detector was followed by several variable gain stages. These were
wideband
IC amplifiers made by Ferranti ( now Zetex ) with a control current /
voltage
that varied each IC's gain over about something like a 12-15dB range. The
control ports were driven in parallel so that gain was swept equally
between all
the devices.

They were at least 6 of these cascaded to provide the necessary gain
before the
signal went off for further processing.

After the pulse was transmitted ( and the receiver input clamped ) the
gain was
ramped up with a triangle waveform to provide the necessary low gain for
near
targets and higher gain for distant targets.

I took one look at the schematic, grinned and said I could fix it.

What problems ( not less than 2 of them ) were they encountering ?

Let me guess, made in the U.S.A. ?
 
A

Andrew Holme

Jan 1, 1970
0
Eeyore said:
The strain gauge thread reminded me of a product with an 'issue' I was
once
asked to take a look at.

It was the receiver section of a marine radar.

The detector was followed by several variable gain stages. These were
wideband
IC amplifiers made by Ferranti ( now Zetex ) with a control current /
voltage
that varied each IC's gain over about something like a 12-15dB range. The
control ports were driven in parallel so that gain was swept equally
between all
the devices.

They were at least 6 of these cascaded to provide the necessary gain
before the
signal went off for further processing.

After the pulse was transmitted ( and the receiver input clamped ) the
gain was
ramped up with a triangle waveform to provide the necessary low gain for
near
targets and higher gain for distant targets.

I took one look at the schematic, grinned and said I could fix it.

What problems ( not less than 2 of them ) were they encountering ?

Graham

Was gain increasing as the 6th power of time? Could you improve the noise
figure by running the first stage(s) at higher gain?
 
J

J.A. Legris

Jan 1, 1970
0
Eeyore said:
The strain gauge thread reminded me of a product with an 'issue' I was once
asked to take a look at.

It was the receiver section of a marine radar.

The detector was followed by several variable gain stages. These were wideband
IC amplifiers made by Ferranti ( now Zetex ) with a control current / voltage
that varied each IC's gain over about something like a 12-15dB range. The
control ports were driven in parallel so that gain was swept equally between all
the devices.

They were at least 6 of these cascaded to provide the necessary gain before the
signal went off for further processing.

After the pulse was transmitted ( and the receiver input clamped ) the gain was
ramped up with a triangle waveform to provide the necessary low gain for near
targets and higher gain for distant targets.

I took one look at the schematic, grinned and said I could fix it.

What problems ( not less than 2 of them ) were they encountering ?

Graham

You've neglected to provide a vital piece of information (not counting
the schematic) that you had that we do not: what was the complaint?
 
P

Phil Allison

Jan 1, 1970
0
"J.A. Legris"
You've neglected to provide a vital piece of information (not counting
the schematic) that you had that we do not: what was the complaint?



** Don't get sucked in.

This is the silliest troll from the depressive bear in years.





........ Phil
 
T

Tim Wescott

Jan 1, 1970
0
Eeyore said:
The strain gauge thread reminded me of a product with an 'issue' I was once
asked to take a look at.

It was the receiver section of a marine radar.

The detector was followed by several variable gain stages. These were wideband
IC amplifiers made by Ferranti ( now Zetex ) with a control current / voltage
that varied each IC's gain over about something like a 12-15dB range. The
control ports were driven in parallel so that gain was swept equally between all
the devices.

They were at least 6 of these cascaded to provide the necessary gain before the
signal went off for further processing.

After the pulse was transmitted ( and the receiver input clamped ) the gain was
ramped up with a triangle waveform to provide the necessary low gain for near
targets and higher gain for distant targets.

I took one look at the schematic, grinned and said I could fix it.

What problems ( not less than 2 of them ) were they encountering ?

Graham
1: Targets in the near range were coming through with a signal strength
much less than expected (because the first amplifier(s) was saturating).

2: I dunno, but I assume you'll illuminate us soon enough.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Posting from Google? See http://cfaj.freeshell.org/google/

"Applied Control Theory for Embedded Systems" came out in April.
See details at http://www.wescottdesign.com/actfes/actfes.html
 
R

Rich Grise

Jan 1, 1970
0
The strain gauge thread reminded me of a product with an 'issue' I was once
asked to take a look at.

It was the receiver section of a marine radar.

The detector was followed by several variable gain stages. These were wideband
IC amplifiers made by Ferranti ( now Zetex ) with a control current / voltage
that varied each IC's gain over about something like a 12-15dB range. The
control ports were driven in parallel so that gain was swept equally between all
the devices.

They were at least 6 of these cascaded to provide the necessary gain before the
signal went off for further processing.

After the pulse was transmitted ( and the receiver input clamped ) the gain was
ramped up with a triangle waveform to provide the necessary low gain for near
targets and higher gain for distant targets.

I took one look at the schematic, grinned and said I could fix it.

What problems ( not less than 2 of them ) were they encountering ?

No way to tell - what was it not doing that it was supposed to be doing,
and/or what was it doing that it wasn't supposed to do?

Thanks,
Rich
 
E

Eeyore

Jan 1, 1970
0
Frank said:
Let me guess, made in the U.S.A. ?

UK actually. Essex in fact.

I also diagnosed the problem with the display for the same system after being
woken up by the phone call.

They didn't believe I could do it over the phone. That was a nice contract.

Graham
 
E

Eeyore

Jan 1, 1970
0
Andrew said:
Was gain increasing as the 6th power of time? Could you improve the noise
figure by running the first stage(s) at higher gain?

Keep going. You're not quite there.

Ideally, estimate the effect on the display.

If you separate out all the effects there were 4 distinct ( inter-related )
issues.

Graahm
 
E

Eeyore

Jan 1, 1970
0
J.A. Legris said:
You've neglected to provide a vital piece of information (not counting
the schematic) that you had that we do not: what was the complaint?

That's what I'm asking you to 'guess'. All the necessary info is there.

Graham
 
E

Eeyore

Jan 1, 1970
0
Phil said:
"J.A. Legris"


** Don't get sucked in.

This is the silliest troll from the depressive bear in years.

LOL !

It's a cute one.

It took me only minutes to see the issues ( and the solution ) but I did have a
display to view too.

Graham
 
E

Eeyore

Jan 1, 1970
0
Tim said:
1: Targets in the near range were coming through with a signal strength
much less than expected (because the first amplifier(s) was saturating).

2: I dunno, but I assume you'll illuminate us soon enough.

Keep going.

A couple of you are on the right tracks but haven't yet got there.

Graham
 
E

Eeyore

Jan 1, 1970
0
Rich said:
No way to tell -

But there is. From first principles.

what was it not doing that it was supposed to be doing,

It wasn't doing it as well as it should have.

and/or what was it doing that it wasn't supposed to do?

Imagine a classic radar display and how it's supposed to work.

Graham
 
D

DaveM

Jan 1, 1970
0
Eeyore said:
That's what I'm asking you to 'guess'. All the necessary info is there.

Graham


I'll bet that the gain ramp should have been a log ramp instead of a linear
triangle.

--
Dave M
MasonDG44 at comcast dot net (Just substitute the appropriate characters in the
address)

Some days you're the dog, some days the hydrant.
 
P

Phil Allison

Jan 1, 1970
0
"Eeyore"
LOL !

It's a cute one.


** It a FUCKING ASININE TROLL !!!


- you ASD fucked pile of pommy shit .






........ Phil
 
J

john jardine

Jan 1, 1970
0
Eeyore said:
But there is. From first principles.



It wasn't doing it as well as it should have.



Imagine a classic radar display and how it's supposed to work.

Graham
Owz abouts, there's a forth power in the radar range equation. Yet the swept
gain goes up as the 6th power. Distant objects look huge. ?

Anyways, I changed to IDnet a month ago and if I can be arsed in
persisting, it's now taking about 2 hours to connect. Did you have any
problems?.
john
 
E

Eeyore

Jan 1, 1970
0
john said:
Owz abouts, there's a forth power in the radar range equation. Yet the swept
gain goes up as the 6th power. Distant objects look huge. ?

If only it was that simple. You're on the right track of course but there's
more.

Anyways, I changed to IDnet a month ago and if I can be arsed in
persisting, it's now taking about 2 hours to connect.

To 'connect' ???? What do you mean ?

Did you have any problems?.

None at all. It was blisteringly fast at least initially. It may have slowed
down a bit since. I'm synching at 8128/448 and it doesn't get any faster than
that with BT's gear.

http://www.adslguide.org.uk/tools/speedtest.asp
Gives me 5464/378 kbps currentyl

What are you coneecting with ? Details and stuff, router stats etc.....

Graham
 
R

Richard Henry

Jan 1, 1970
0
Eeyore said:
But there is. From first principles.



It wasn't doing it as well as it should have.



Imagine a classic radar display and how it's supposed to work.

Classic? A-scan, B-scan, or PPI?
 
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