[TenTec] When did Ten-tec switch to Schottky diode ring mixers?

[Kevin Purcell]

Excellent. Thanks Steve for that data point. And Don, NN8B, who  
replied too. Both have the Corsair 2.

So they had switched by 1986.

Anyone with an original Corsair (Corsair 1, so to speak)? I think  
that might be the rig they made the switch to schottky diodes.

It would just take a second to check the schematic in the manual on  
the RF Mixer board :-)

They won't be MPN-3404 PIN diodes (which appear in fours in the  
Corsair too) but something else.

I'm sorry I didn't mention the quad option too (so people go hunting  
for 4 diodes) as it is similar to the digital Argosy RX mixer.

> TT will use either four discrete diodes (probably switching diodes  
> if they were still using them but they may be discrete schottky  
> didoes) or, more likley, a single quad schottky package, as they do  
> in the 525D Argosy digital which is an ND487CI.
>
> Does the RF mixer board have a ND487CI on it?
>
> Or a similar 4 legged package between a pair of transformers and  
> taking signal from the LO via a driver?

On May 20, 2007, at 9:15 AM, Steve Hunt wrote:

> Kevin,
>
> I have a Corsair II purchased new from the UK distributor on 3rd  
> October 1986. The serial number is 580 - 01861
>
> The schematic shows a single component, D13, for the mixer diode  
> quad; its part number is given as 87C2 K38
>
> Hope this helps.
>
> Steve G3TXQ
>   ----- Original Message -----
>   From: Kevin Purcell
>   To: Discussion of Ten-Tec Equipment
>   Cc: Kevin Purcell
>   Sent: Saturday, May 19, 2007 7:01 PM
>   Subject: [TenTec] When did Ten-tec switch to Schottky diode ring  
> mixers?
>
>
>   When did Ten-tec switch to Schottky diode ring mixers?
>
>   If you have a Corsair or Corsair II you can help by looking at the
>   schematic in the manual for the RX mixer in your TT rig. Let me know
>   the diode type.
>
>   Why ... I've been trying to interpret some performance numbers from
>   Sherwood and trying to find comparable measurements for 1n4148 and
>   Schottky diode ring mixers to answer the question "how much worse is
>   a PN diode mixer?".
>
>   <http://www.sherweng.com/table.html>
>
>   Looking at the data I have it seems to be sometime in the first half
>   1980s
>
>   The TT 546 Omni C from 1981 has four 1n4148 in the primary RX mixer
>   (1981).
>
>   The second version (after serial 822?) of the TT 525 Argosy
>   (analogue) has four 1n4148 in the primary RX mixer (early 1980s).
>
>   The TT 525D Argosy (digital) had a Schottky diode ring mixer
>   (1982-1986?)
>
>    From W8KC's lineage
>   <http://mywebpages.comcast.net/w8kc/lineage.htm>
>   Omni C -- 1981
>
>   Corsair -- 1983
>
>   Corsair II -- 1987? (8/87) (production 1987 to 1990)
>
>   Paragon I 585 -- 1988? (5/88)
>   Omni V -- 1990?  (11/90)
>
>   So I think one can be pretty sure that the Paragon and the Omni V
>   have Schottky diode ring mixers so that leaves the Corsair's as the
>   point of the design change. But if I'm wrong let me know.
>
>   Thanks.
>   --
>   Kevin Purcell
>   kevinpurcell at pobox.com
>
>
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--
Kevin Purcell
kevinpurcell at pobox.com