> 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@kingwoodcable.com>
> Sent: Wednesday, July 07, 2010 2:59 PM
> To: "Amp Reflector"<amps@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@contesting.com
>> http://lists.contesting.com/mailman/listinfo/amps
>>
>
> _______________________________________________
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>
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