[Premium-Rx] Attenuator Pads

[Ahmet Gundes]

Hello,

Attenuator Pads are very useful in many applications
One main use is for signal absorption and another
for "buffer" and isolation between stages.  When signal
travels from stage to stage, there are reflections. These
reflections cause undesirable distortion in active devices
such as transistors. Therefore Pads help absorb reflections
and isolate / buffer between stages.  A well matched transistor
amplifier also has better distortion specs partly  due to
much less returned signals causing distortion.

Another method of reflected signal absorption is to dump it
into a resistive load. The way of doing this is to use 
a Diplexer Filter which has two filters, one terminated by a
Resistor to absorb unwanted freq range and the other to pass the
range desired.  Many Mixer stages use this method.

Some amplifier designs do not use Resistive elements or Pads 
as this tends to increase the NF slightly.

Have a Great Weekend all.

Ahmet Gundes


> I found a series 6 dB pad helps when you are using an antenna tuner. I just
> tune for maximum noise or signal and the tuner ends up being close to 50
> ohms matched.
> I have been able to transmit (on the Ham Bands) using this method of tuning.
> I found receiver input impedance is not usually exactly 50 ohms. fc
> 
> -----Original Message-----
> From: W.J. Ubbels [mailto:W.J.Ubbels at student.tudelft.nl]
> Sent: Friday, January 30, 2004 3:58 PM
> To: 'Richard Reich '; 'W.J.Ubbels at student.tudelft.nl '; 'ahmet-m at usa.com
> '; 'premium-rx at ml.skirrow.org '
> Subject: RE: RE: [Premium-Rx] General Coverage Antennas for HF
> 
> 
> Yes, that would be a good option. The antenna delivers more than enough RF,
> so a 6dB pad won't hurt.
> 
> Wouter
> PE4WJ 
> 
> 
> Thank you for that information - just what I was looking for.
> 
> I guess for it to work correctly into any receiver, the amp must see a  constant
 impedance of 50R - so  would fit a pad (of around 5-6dB or so) between the amp  and receiver?

-- 
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