[Amps] QSK-1500 chip

[Jeff Blaine AC0C]

Joe,

Thanks for the comment.

Tough for me to imagine because the device's switching speed is going to be 
the low tens of nS range - and the rest of the "ham stuff" with respect to 
switching is going to be in mS increments.  I can't quite follow the 
conclusion that the circuit would necessarily need to be modified as a 
result of the part differences.  If I were looking at a nearly $250 
investment required just to get two of these obsolete parts, I sure would 
want to give it a try.  But that's me.

In looking at the data sheet the thing I noticed was a lot of hype on the 
Mot sheet about additional diode clamps.  I can believe that the circuit may 
not ensure that part is properly bypassed and the designer relied on the 
input clamps to keep things from getting the gate oxide blasted.

Good luck to Lon in his adventure!

73/jeff/ac0c
www.ac0c.com


--------------------------------------------------
From: "Joe Subich, W4TV" <lists at subich.com>
Sent: Wednesday, July 07, 2010 7:17 PM
To: <amps at contesting.com>; <k5jv at kingwoodcable.com>; 
<keepwalking188 at yahoo.com>
Subject: Re: [Amps] QSK-1500 chip

>
> > Would a CD4011B instead?
>
> Probably not.  The QSK-1500 functioned only because of the specific
> properties of the MC14011BCP when used at U3B and C.
>
> It has been nearly 30 years now and I can't remember if the specific
> requirement was because of the output properties of U3C or the input
> properties of U3B but those two gates plus D1, R4 and C4 are a crude
> pulse stretching circuit with a very fast attack time (allowing the
> PIN diodes to switch before the transceiver can generate RF) and
> holding the diodes in the transmit state just long enough after the
> key was released for the transceiver to stop producing RF but still
> releasing quickly enough so as not to overly delay the overall return
> to receive.
>
> If one needs to replace U3 and can not find an MC14011BCP, the circuit
> between pins 8/9 and pin 4 will need to be replaced by one that takes
> a logic high (+12) when the key is closed and produces a logic high
> (+12V) output that remains high for about 10 - 15 ms after the key
> is opened.  Using another "4011" type of quad NAND will most certainly
> require a significant amount of cut and try to find new values for D1,
> R4 and C4 to achieve the proper timing characteristics.
>
> 73,
>
>    ... Joe, W4TV
>
> On 7/7/2010 7:31 PM, Jeff Blaine AC0C wrote:
>> Would a CD4011B instead?  I know the TI chip is still available and has
>> diode clamped inputs.   $0.40 at Mouser.
>>
>> 73/jeff/ac0c
>> www.ac0c.com
>>
>>
>> --------------------------------------------------
>> From: "kingwood"<k5jv at kingwoodcable.com>
>> Sent: Wednesday, July 07, 2010 2:59 PM
>> To: "Amp Reflector"<amps at contesting.com>
>> Subject: [Amps] QSK-1500 chip
>>
>>> Greetings to all,
>>>
>>>         I have located a source for the, hard to find, Motorola 
>>> MC14011BCP
>>> chips.  The only problem is that I must order 25 of them to get the 
>>> price
>>> anywhere with reason.
>>>
>>>         Does anyone have an interest in these chips?  There are two of 
>>> them
>>> in the QSK-1500.  The manufacturer marked on of the a absolutely 
>>> critical
>>> for proper QSK timing.   If I get enough interest, I will order them and
>>> will sell 20 of them for $10, each, including shipping to the original 
>>> 48.
>>> First come, first served.
>>>
>>> 73 de Lon, K5JV
>>>
>>> Lon W. Cottingham
>>>
>>> 1110 Golden Bear Ln.
>>> Kingwood, TX 77339
>>>
>>> 281-358-4207
>>> 281-795-1335 Cell
>>>
>>> _______________________________________________
>>> Amps mailing list
>>> Amps at contesting.com
>>> http://lists.contesting.com/mailman/listinfo/amps
>>>
>>
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>