Test Equipment Anonymous (TEA) group therapy thread

[BU508A]

This is my very crude attempt of designing a TEA logo after fighting with Inkscape for 2 hours.      

[McBryce]

This is my very crude attempt of designing a TEA logo after fighting with Inkscape for 2 hours.      

Is that triangular wave deliberately all over the place?

McBryce.

[Robert763]

Well those are not real LM741s. The 741 has a gain bandwidth of about 1.5MHz. Amplitude is also limited by the slew rate of 0.5V/us.
No way are you getting a gain of 1 out of a 741 at 10MHz.
Also have you loaded the output? should really be able to drive 50R. A old composite video amplifier works well especially if you put a ethernet isolating transfoumer / balun on the outputs. The Extro ones ae very nice. A VGA one with BNCs will also work.

LM7171 has 200Mhz unity-gain bandwidth. In simulation I was able to get 150Mhz easy.

For the transfo I think I saw in the spec something like 2db attenuation. I need to check back.

 
I read 741, not 7171 some kind of mental abberation or confirmation bias   
The 7171 is good for this.

[Kosmic]

Well those are not real LM741s. The 741 has a gain bandwidth of about 1.5MHz. Amplitude is also limited by the slew rate of 0.5V/us.
No way are you getting a gain of 1 out of a 741 at 10MHz.
Also have you loaded the output? should really be able to drive 50R. A old composite video amplifier works well especially if you put a ethernet isolating transfoumer / balun on the outputs. The Extro ones ae very nice. A VGA one with BNCs will also work.

LM7171 has 200Mhz unity-gain bandwidth. In simulation I was able to get 150Mhz easy.

For the transfo I think I saw in the spec something like 2db attenuation. I need to check back.

 
I read 741, not 7171 some kind of mental abberation or confirmation bias   
The 7171 is good for this.

Yes working fine and can be found cheaply.

[med6753]

Well those are not real LM741s. The 741 has a gain bandwidth of about 1.5MHz. Amplitude is also limited by the slew rate of 0.5V/us.
No way are you getting a gain of 1 out of a 741 at 10MHz.
Also have you loaded the output? should really be able to drive 50R. A old composite video amplifier works well especially if you put a ethernet isolating transfoumer / balun on the outputs. The Extro ones ae very nice. A VGA one with BNCs will also work.

LM7171 has 200Mhz unity-gain bandwidth. In simulation I was able to get 150Mhz easy.

For the transfo I think I saw in the spec something like 2db attenuation. I need to check back.

 
I read 741, not 7171 some kind of mental abberation or confirmation bias   
The 7171 is good for this.

Yes working fine and can be found cheaply.

Looks damn good.  Why would you care about that slight amount of attenuation as long as the output (including harmonics) is clean and accurate?

[Kosmic]

Well those are not real LM741s. The 741 has a gain bandwidth of about 1.5MHz. Amplitude is also limited by the slew rate of 0.5V/us.
No way are you getting a gain of 1 out of a 741 at 10MHz.
Also have you loaded the output? should really be able to drive 50R. A old composite video amplifier works well especially if you put a ethernet isolating transfoumer / balun on the outputs. The Extro ones ae very nice. A VGA one with BNCs will also work.

LM7171 has 200Mhz unity-gain bandwidth. In simulation I was able to get 150Mhz easy.

For the transfo I think I saw in the spec something like 2db attenuation. I need to check back.

 
I read 741, not 7171 some kind of mental abberation or confirmation bias   
The 7171 is good for this.

Yes working fine and can be found cheaply.

Looks damn good.  Why would you care about that slight amount of attenuation as long as the output (including harmonics) is clean and accurate?

just my OCD side. It's not really important. But I can fix it by adding 2 resistors and 1 cap

[BU508A]

This is my very crude attempt of designing a TEA logo after fighting with Inkscape for 2 hours.      

Is that triangular wave deliberately all over the place?

McBryce.

Yes, sort of.
The idea was to show a screen of a scope and the text "TEA" and "EEVBlog" should follow the shape of the circle on the outside.
I've read a lot of how-to's in the web but that damn text refused to follow the shape of the circle. I guess, I have to read
a bit more and play around with Inkscape. Twenty years back I used Corel Draw a lot for this kind of stuff. The UI was
easy and intuitive, but with this Inkscape thingie I have the feeling to fight with Eagle for vector graphics. *brrrrrr*

[Wolfgang]

... any point doing this ? Does this have better close to carrier PN than the BG7TBL stuff ? Or is it just fun ?

[PA0PBZ]

The idea was to show a screen of a scope and the text "TEA" and "EEVBlog" should follow the shape of the circle on the outside.

If you have Microsoft Word it's a 10 seconds job with WordArt

[BU508A]

The idea was to show a screen of a scope and the text "TEA" and "EEVBlog" should follow the shape of the circle on the outside.

If you have Microsoft Word it's a 10 seconds job with WordArt

Linux here. No MS Office stuff.

[bd139]

quick TEA logo attempt (blatant plagiarism involved of course  )

[0culus]

quick TEA logo attempt (blatant plagiarism involved of course  )

TEAtronix

[bd139]

Just bought another British made item: Racal 9916 520MHz counter. This one has a working OCXO that the seller has checked against his GPSDO apparently.



Aaaand I'm done shopping for a while now  . That was actually my entire shopping list nailed.

[Robert763]

So This £5.99 ebay purchase arrived today

Putting it with this

(Ebay for £15 including a good CCD video camera, lens currently £845 from Edmund  )
Allows me to do some macro /micro photography with th Canon M100.


Those were handheld with normal indoor lighting.

[Kosmic]

... any point doing this ? Does this have better close to carrier PN than the BG7TBL stuff ? Or is it just fun ?

I don't know, I think the BG7TBL is outputting squarewave no ? I wanted 8 outputs all sinewave. And yes it's mostly for fun. If I move it to a PCB it's also to educate myself and learn a little.

[factory]

Just bought another British made item: Racal 9916 520MHz counter. This one has a working OCXO that the seller has checked against his GPSDO apparently.



Aaaand I'm done shopping for a while now  . That was actually my entire shopping list nailed.

I must be unlucky with Racal stuff, I've got three different Racal counters here, none of which are working properly.
The first I got was a ex mil 936, I did get this going by replacing two shorted tants (going to the probe power socket), but went to use it last year and found it refusing to count.
The next was an older SA520, the less said about this one the better.
Recently bought a 1GHz 9025, guess the problem with this one, again no count, but works fine when an external 1MHz reference is fed into the back and for good measure someone has blown the 10Hz to 150MHz input.


David

[bd139]

Yeah typical British engineering. I had one with a duff OCXO ages ago and had to replace it

[McBryce]

The idea was to show a screen of a scope and the text "TEA" and "EEVBlog" should follow the shape of the circle on the outside.

If you have Microsoft Word it's a 10 seconds job with WordArt

Linux here. No MS Office stuff.

Libre Office can do that too.

McBryce.

[mnementh]

Izzat holesaw-pad construction I see...? How much PITA in real use?

mnem
*pats belly* Sooooo much pizza... *Grooooooannnnnnnnnn*

Yes my first tentative. Got the bits from china a while ago.      In term of usage, it's pretty easy if you have a drill press. A lot simpler than cutting pad with the nibbler and then gluing.

Awresome! I suspected that would be the case; I hoped it would prove out. Seems to me that having the pad on the same plane as the ground fill should really inhibit stray capacitance.

mnem
 

[med6753]

quick TEA logo attempt (blatant plagiarism involved of course  )

TEAtronix

I wonder why I like that so much? 

[factory]

Yeah typical British engineering. I had one with a duff OCXO ages ago and had to replace it

No prizes for guessing it was the OCXO and as usual it's the only part I can't find any service info for, I used the manual for the similar but lower frequency 9024 as I couldn't find a Racal 9025 one.


Here is what I tested the counter with, a HP 3311A for the external 1MHz frequency reference input and the HP 8620C/86222B on the other end of the really long BNC lead, with GR 874 attenuator before counter input.




David

P.S. that nice 60's HP 101A 1MC oscillator needs repairing too.

[bd139]

I think most of their counters double the OCXO up from 5MHz to 10MHz. I managed to frig one here to take a 10MHz Bliley OCXO off aliexpress by bypassing the doubler:

https://www.eevblog.com/forum/testgear/repairing-off-frequency-racal-9442-ocxo/

BTW rather love the overkill oscillators   

[VK5RC]

Best way to fix an oscillator - make a high gain amp - it will be an oscillator - well that is what happens for me! (and vice versa)!

[Neomys Sapiens]

Well those are not real LM741s. The 741 has a gain bandwidth of about 1.5MHz. Amplitude is also limited by the slew rate of 0.5V/us.
No way are you getting a gain of 1 out of a 741 at 10MHz.
Also have you loaded the output? should really be able to drive 50R. A old composite video amplifier works well especially if you put a ethernet isolating transfoumer / balun on the outputs. The Extro ones ae very nice. A VGA one with BNCs will also work.

LM7171 has 200Mhz unity-gain bandwidth. In simulation I was able to get 150Mhz easy.

For the transfo I think I saw in the spec something like 2db attenuation. I need to check back.

 
I read 741, not 7171 some kind of mental abberation or confirmation bias   
The 7171 is good for this.

That sort of mis-cognition results from having too many people around of which you know with a high degree of certainty that upon hearing OPA they will by default propose their blasted 741/324/2904 abominations like none other, and far nicer ones existed.
IMO they should be relegated to the same category like coal mine ponies, flintlocks, slate tablets....

[Cerebus]

Best way to fix an oscillator - make a high gain amp - it will be an oscillator - well that is what happens for me! (and vice versa)!

Who needs high gain - my last "successful" oscillator creation was supposed to be a unity gain 'diamond transistor' output stage!