[INRAD] Switching diodes in roofing filter for the IC-775DSP

[Thomas]

William,

You have a valid point and I did make a mistake regarding the MPN3404 
recombination time. I have the HP spec sheet for the 5082-3081 and it is 
indeed 2.5us. However, my Motorola MPN3404 data sheet does not list the 
recombination time and I made the incorrect assumption that it was 
microseconds - which on second thought can't be correct. The data sheet 
says that it is intended for VHF switching applications which implies 
that its recombination time must be much less than a microsecond.

My lame excuse for the error is I was being hurried to head out the door 
while I was typing my response to Charlie's email. You know when the XYL 
is saying let's go... it is time to go!

'73, Thomas - AC7A


William E. Sabin wrote:

> The MPN3404 has a recombination time of  "a Few Microseconds" and the 
> HP5082-3081 has "2500ns = 2.5 microsec".  These two types appear to be 
> almost identical in that respect.
>
> Bill W0IYH
>
> ----- Original Message ----- From: "Thomas" <ac7a at cox.net>
> To: "Charlie Mazoch Jr." <w5vin at earthlink.net>
> Cc: <list at inrad.net>
> Sent: Friday, November 25, 2005 10:50 AM
> Subject: Re: [INRAD] Switching diodes in roofing filter for the IC-775DSP
>
>
>>
>> The mistake that many hams make is assuming that any PIN diode will work
>> in most any application. The MPN3404 is rated for VHF switching
>> applications, because its recombination time is short; a few
>> microseconds. Yet, I often see the MPN 3404 used in HF RF and IF
>> applicaitions. Not to say that it won't act as an RF switch, but it will
>> not provide the isolation or low distortion of a more suitable HF PIN
>> device. By a more suitable HF PIN device, I suggest a device like the
>> HP5082-3081, with its 2500nS recombination time (1 tau).
>>
>>
>
>
>