[GreenKeys] Might be a bad weekend...

[Ron Ott]

Ooops, I meant you can make filters for 425 and 850Hz shifts with toroids and tubes.

Ron

----- Original Message ----
From: Ron Ott <ronott at sbcglobal.net>
To: jhhaynes at earthlink.net; Bob Camp <ham at cq.nu>
Cc: greenkeys at mailman.qth.net
Sent: Saturday, December 1, 2007 12:03:58 PM
Subject: Re: [GreenKeys] Might be a bad weekend...

I believe that 170Hz shift became practical with the advent of op amp filters. On the other hand, you can make adequate filters and discriminators with toroids and tubes.

Ron, W6XY


----- Original Message ---- 
From: "jhhaynes at earthlink.net" <jhhaynes at earthlink.net> 
To: Bob Camp <ham at cq.nu> 
Cc: greenkeys at mailman.qth.net 
Sent: Saturday, December 1, 2007 11:52:05 AM 
Subject: Re: [GreenKeys] Might be a bad weekend... 



On Sat, 1 Dec 2007, Bob Camp wrote: 

> With 425 shift you get away from the problem. You can also tolerate more 
> drift on the link. My guess is that drift / frequency tolerance is the bigger 
> issue for the military. 
> 
I think you're right, and that also explains why everybody used 850 Hz 
shift in the early days. When you try to copy RTTY on a pre-WWII 
Super Pro receiver (or even on a SP-600) you understand the problem. 

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