EMRFD Message Archive 11609

Message Date From Subject
11609 2015-09-09 22:29:44 ve6jf Looking for a datasheet..

I'm trying to build an attenuator with some recently acquired Motorola RF hybrid stripline attenuator chips. Ive scoured the interwebs and not been able to find a datasheet on this part and wondering if anyone may have one in an old databook or in their archives somewhere. It's this one: http://www.ebay.com/itm/RF-HYBRID-STRIPLINE-RF-ATTENUATOR-MOTOROLA-10W-10DB-50R-MAR110-/191450345675

 Thanks - Jim VE6JF

11610 2015-09-10 02:24:48 kerrypwr Re: Looking for a datasheet..
I think that the word "hybrid" confuses matters; I think that it is simply a good-quality 10dB attenuator, useable up to several GHz in a well-designed microstrip/stripline layout.

It will require heatsinking to achieve its power rating; not a great deal is required for 10 watts.

A nice component; use it!

Kerry VK2TIL.
11611 2015-09-10 07:14:21 Gene W5DOR Re: Looking for a datasheet..

Go to  my web at www.w5dor.com and over on the right is a table of contents.  The first thing is Motorola data books.  Maybe you can find it in an old MOtorola RF data book.

 

Gene, W5DOR

gene@w5dor.com

www.w5dor.com

 

 

11612 2015-09-10 07:18:35 Gene W5DOR Re: Looking for a datasheet..

.  .  .and,  BTW,  it's a LARGE file so it will take a while to download.  My internet runs at 60Mbs and it still takes a while to download it.

 

Gene, W5DOR

gene@w5dor.com

www.w5dor.com

 

 

11613 2015-09-10 10:14:15 Jim Leslie Re: Looking for a datasheet..
Thanks Gene; I downloaded & went through everything that looked promising and still came up empty. I'm usually very good at
finding information (thanks to Google!) and it's hard to throw in the towel, but I am almost at that point! I've spent lots of time looking.

I think this part will make a great power attenuator if I could only figure it out. Not sure if it needs external termination resistors for example.
If anyone has any ideas on how to discover the way it works, it would be greatly appreciated.
73 Jim VE6JF

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11614 2015-09-10 11:05:22 Andy Re: Looking for a datasheet..
Jim wrote:

Go to  my web at www.w5dor.com and over on the right is a table of contents.  The first thing is Motorola data books.  Maybe you can find it in an old MOtorola RF data book.


I'd suggest making some corrections to your website.  (Note the extra space character or %20 on the end of the link above ... remove that if you were reading this and can't get there by clicking on it.)

Change "Motarola" to "Motorola".

Change "Motoraola" to "Motorola".

Change "MIT" to "MTT".

There is probably more.

You might want to run your webpages by someone else who nose bettir how two spel.

Still -- nice collection of appnotes!

Andy


11615 2015-09-10 11:48:26 n2msqrp Re: Looking for a datasheet..
JIm,

Let's assume it is a TEE or PI attenuator.

Calculate the values for the resistors using the following program:

<http://www.everythingrf.com/rf-calculators/attenuator-calculator>

If it is a TEE it will have the following ideal values:

---25.97------25.97---
11616 2015-09-10 12:00:56 n2msqrp Re: Looking for a datasheet..
I noticed the diagram spacing is missing on my posting.

The TEE 35.14 series resistor is connected at the junction of the two 25.97 shunt resistors.

The PI 90.25 shunt resistors are on each side of the 71.15 series resistor.

Mike N2MS
----- Original Message -----
11617 2015-09-10 13:04:28 Hector Pascal Re: Looking for a datasheet..
Kerry,. VK2TIL, is correct.

It is designed to be inserted in a break in a 50 ohm microstrip transmission line.
A cut-out in the microstrip line and the board must be made, so that the attenuator can be solidly bolted to a heat sink using thermal paste. Then the leads are simply soldered to the line.

No other resistors are needed.   When the output of the line is terminated with 50 ohms, the input will be 50 ohms too.

Two important points remain:

You need to establish whether this type of attenuator has a designated input and output lead - those made using hybrid technology are often not internally symmetrical, so that only one end can take the full power.  Getting this wrong in construction, or even reversing the attenuator when actually using it, will destroy it!

You also need to establish the amount of physical heatsink required to keep the device temperature at the recommended level.

So you still need a data sheet, unless someone else can answer these 2 points,

David
VK6JT

11618 2015-09-10 14:24:55 John Marshall Re: Looking for a datasheet..
Mike,

From the picture on the ebay ad it appears the part has only 3 connection terminals, presumably In, Out, and common, with both shunt elements connected to common. So when measuring in to out with an ohmmeter, the series combination of two 90.25 ohm resistors will be in parallel with the 71.15 ohm resistor, giving 51.03 ohms. Input or Output to ground would measure 57.88 ohms.

What we can't guess (and a datasheet should tell us) is whether the attenuator is bilateral in terms of power handling. That seems likely but it would be possible that one shunt resistor has a higher power rating than the other.

John, KU4AF


11619 2015-09-10 14:49:31 Jim Leslie Re: Looking for a datasheet..
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11620 2015-09-10 14:57:15 Jim Leslie Re: Looking for a datasheet..
John,
That was my concern as well; is it bilateral? The tabs for in/out are placed in such a way that it could be keyed
as to which is the input side.
It is likely but I'd rather not toast in testing it if I can avoid it.
So hard to believe in all my net searches I can't find any datasheet on it. There must be one out there somewhere. :)
73
Jim
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11621 2015-09-10 15:09:18 Dennis Czelusniak Re: Looking for a datasheet..
I suggest asking the vendor for the data sheet. How did they arrive by thier description if not by the data sheet. Lucky guess?

Dennis




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11622 2015-09-10 15:29:07 kerrypwr Re: Looking for a datasheet..
It's quite common for this kind of attenuator to be "offset"; this Florida RF device, the first that I picked at random from the catalogue, is considerably so;

[url=http://postimage.org/][img]http://s29.postimg.org/jspb0nycn/att.gif[/img][/url]

These are bilateral; I have seen a few of these devices and they have always been bilateral.

Mount your attenuator on a heatsink and test it; a variable DC supply would do.

Just apply known voltages & currents, starting small, and see what heating takes place.

Symmetry can be checked by reversing the connections.

It is not necessarily 50 ohms Z.  To check this, terminate one end in 50 ohms; you should measure 50 ohms DC resistance at the other end.  It may not be exactly 50 ohms; I think that allowance is made for resistance change with temperature in these devices

Kerry VK2TIL.
11623 2015-09-10 15:31:34 kerrypwr Re: Looking for a datasheet..
I inserted the wrong link to the picture; try this;

http://s29.postimg.org/jspb0nycn/att.gif

Kerry VK2TIL.

 

11626 2015-09-10 21:34:01 dualraoul Re: Looking for a datasheet..
Have you tried Sphere Research? They list the attenuator and may have a data sheet.
 Used/New RF and Microwave Electronic Test Equipment and Parts
Bottom of the page and only $3.20 each.

Ron K0IDT

 

11630 2015-09-11 09:32:31 n2msqrp Re: Looking for a datasheet..
Duh! Thanks for correcting my calculation.

Mike N2MS

From the picture on the ebay ad it appears the part has only 3 connection terminals, presumably In, Out, and common, with both shunt elements connected to common. So when measuring in to out with an ohmmeter, the series combination of two 90.25 ohm resistors will be in parallel with the 71.15 ohm resistor, giving 51.03 ohms. Input or Output to ground would measure 57.88 ohms.

What we can't guess (and a datasheet should tell us) is whether the attenuator is bilateral in terms of power handling. That seems likely but it would be possible that one shunt resistor has a higher power rating than the other.

John, KU4AF