[INRAD] PIN DIODES

[dj]

Perhaps this will help:

http://members.aol.com/cdrentea2/Improving-Receiver.pdf

If I'm not mistaken, Cornell wrote the original article using PIN  
diodes for switching bandpass filters in receiver front ends.  This  
was published in the Fall 1991 issue of Communications Quarterly.   
It's good reading in any event.

Dale, K9VUJ



On 30, Nov 2005, at 18:20, Charlie Mazoch Jr. wrote:

> Hi Tom:
>   This PIN diode fad started out in the days when Hewlett Packard was
> making their series of PIN diodes. There were a lot of them installed
> into the FT-1000 Yaesu series. I installed a set into an Icom 735 and
> saw zero improvement.  I'm in full agreement with your remark about
> comments listed on W8JI's and the Sherwood sites. My beliefs  
> concerning
> PIN switches in low signal receive path switching  is that as
> semiconductor barrier voltages increase so does electronic or resistor
> noise. The advantages of the PIN is that it acts as a variable  
> resistor
> at RF and a 50 ma. forward bias may switch 1 ampere of RF  whereas in
> the PN junction diode this forward bias must be greater than the
> switching current. When one introduces electronic noise into a  
> receivers
> front end by using inexpensive or sloppy design and then amplifies it
> 100 + Dbm it's annoying in the least. I believe that as the Hf noise
> floor rises because of man made interference the equipment  
> manufacturers
> don't put as much emphasis into low noise receiver design. I say this
> because if one looks at specifications of VHF and UHF equipment the  
> MDS
> and noise figures seem better. I personally use Schottky diodes as low
> level signal path switches. Their barrier voltage is lower, 0.37  
> versus
> 0.68 volts for hot carrier diodes. The GaAs devices offer much lower
> noise figure and their barrier voltage is less than silicon devices.
> This also leads to higher Ft's. I'm not an RF engineer but  
> modification
> of my personal equipment has led to less electronic noise. This is by
> measuring MDS and noise versus signal. As stated in your e-mail relay
> switching is quieter than solid state if one utilizes quality  
> devices. I
> believe W8JI's comment was that a 1N4148 PN junction diode was  
> adequate
> for low level signal path switching. and a PIN diode offered no  
> visible
> improvement on his measuring equipment. In fact he dares someone to
> prove him wrong. Not by ear but through testing with good  
> equipment. His
> comments on linear amplifier tune up and VHF parasitic suppression  
> in HF
> amplifiers are also worth reading.  Charlie  W5VIN
>
> _______________________________________________
> INRAD mailing list provided as a service by International Radio
> INRAD Web Site: http://www.qth.com/inrad
>
> To Submit Message to the List: list at inrad.net
> List Help:
> http://mail.inrad.net/mailman/listinfo/list_inrad.net