Component symbols and others
 

Hyas peeps. While in my quest to build my Tri band VHF Transceiver .. having trouble with the FM detector / IF stage.. I decided to look up SINAD measuring instruments and see if it could help.
I found a wonderful You tube piece that explained the SINADDER 3 and its uses, and.. the schematic. It looked quite a simple thing...I knocked up a pcb for the AGC amp and 1 Khz filter and Active rectifier. STUPIDLY.. I didnt do a bench "knock up" prior...as it was a commercial item
The first version didnt work as I had substituted the Quad opamp LM348 with the LM324 as I had them in stock.... they are both Single rail devices..so I thought a simple substitution was ok.
Second version. I substituted the Quad opamp with the dual LM358.... and knocked up the Active filter and rectifier. Both worked fine... so I made another pcb.... including the AGC amp.
Again.. failure.
So what was wrong ?? I was obviously missing something.
As this was an american circuit.. originally posted by Motorola.. I scrutinised the schematic again....
If you see the schematic added...The AC Gound and DC neg use different Ground / Earth symbols...... Stupidly.., when I had redrawn the schematic I used the same symbol for both......
Not blaming anyone but myself.... the americans.. use the symbol shown for a NEG connection, whereas I always used a -V symbol for opamp connections.
Hopefully this is a "heads up" to anyone else building OPamp based projects.. ::wall::wall::):)

Re: Component symbols and others
 

:thumbsup:

Re: Component symbols and others
 

Don't know if you have it, but the manual is here

http://repeater-builder.com/test-equ...sinadder-3.pdf

Re: Component symbols and others
 

Bloomin heck.. that was quick.. I just posted :D Thanks Terry.. I just had the schematic. I have substituted the split rail PSU for a DC/DC converter...Then a common ground is ok if I connect external items with a different ground.
I guess you either have one or use one... I was able to get a nice picture of the meter scale which I can use.... no point in re inventing the wheel.
73's

Re: Component symbols and others
 

By pure chance, I was reading something the other day and it was mentioned, so I looked it up and found the manual :)

Re: Component symbols and others
 

That is a very unconventional way of using earth symbols, even for an American diagram. I would expect a 'V-' or '-12V' or similar symbol.

I use 3 different earth symbols on diagrams that I draw :

The 'downwards italic E' for 0V, common rail, logic ground, etc. May be connected to mains earth, may not. I put a letter alongside it where appropriate (e.g. an 'A' for analogue ground, a 'P' for power driver ground, etc. Normally all those are electrically connected, possibly at a 'star point' in the PSU)

The 'triangle of shortening horizontal lines' is for mains/chassis metalwork earth where is is distinct from the first ground.

The 'triangle' (the common American ground symbol) I use for a common rail that is most certainly NOT mains earth. For example the -ve side of the mains smoothing capacitor in an SMPSU.

Re: Component symbols and others
 

Glad its not just me then :D Motorola used those symbols on their instrument as well so I assume SINADDER just copied it.. although the circuits do differ. Sinadder pared it down a bit... especially on the AGC circuit.