[Premium-Rx] Mini-circuit amps

[Chuck Hutton]

Hi Jim:

 

 

The loss is not 3 dB per port, but rather log(# of ports).

 

For example:

 

# of ports           loss (dB)

 

2                                             3

3                                             4.7

4                                             6

8                                             9

And ..

12                       10.8

 

 

There's a nice table of insertion loss versus # of ports in a MiniCircuits
app note at http://www.minicircuits.com/appnote/an10006.pdf .

 

 

Chuck

 

 

  _____  

From: premium-rx-bounces at ml.skirrow.org
[mailto:premium-rx-bounces at ml.skirrow.org] On Behalf Of James C. Garland
Sent: Saturday, November 12, 2005 7:19 PM
To: premium-rx at ml.skirrow.org
Subject: Re: [Premium-Rx] Mini-circuit amps

 

Scott,
I'm not sure your multicoupler-on-the-cheap will yield very good
performance, but I'd recommend attenuating the input, rather than the
output. You'll have a wider dynamic range on the amplifier by attenuating
the input signal, which is probably more important than preserving the noise
figure. Actually, with a 12 way splitter, you'll probably need all 20 db
gain and then some. I'd guess you'll lose about 3dB for each port on the
splitter.  

You can't adjust the gain by fiddling with the voltage for the m onolithic
minicircuit amps (I'm not sure whether yours is that type, however.)  In all
the ones I've seen, the power supply voltage is in series with an external
resistor that sets the bias current for the amplifier. The amplifier
performance deteriorates rapidly if you move away from the optimal bias
point.

Regards,

Jim

At 09:42 PM 11/12/2005, you wrote:



I'm getting ready to fiddle with a MIni-Circuits ZFL-500LN amp ahead of a 12
way splitter to use as a poor man's multicoupler.  Because it was all cheap
:)

The amp has nominally 20 - 25 db gain or so, which I'd like to reduce to
make the system a unity gain set up.  Can anyone hazard a guess what the
best approach to doing this might be?  I've considered an attenuator on the
output of the amp, but was also curious whether the gain might be usefully
varied by reducing the supply voltage, and what effect that might have on
noise figure (which is OK at less than 3db) or 3rd order IMD (which ain't
very good already at about +14 db).

Thanks for any ideas.

Scott 
_______________________________________________

Premium-Rx Mailing List
To Post: premium-rx at ml.skirrow.org
For Info: http://ml.islandnet.com/mailman/listinfo/premium-rx
Visit the Website: http://kahuna.sdsu.edu/~mechtron/PremRxPage/

-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mailman.qth.net/pipermail/premium-rx/attachments/20051112/d15f4e4e/attachment.htm