Joel,
I saw the comments on the schematic. Interesting. PINs are quiet and fast
but wow, easy to fry if you were to inadvertently to behave badly. :)
Relays on the QT here for me.
The good news is that On seems to still be making those so the guy will be
in luck.
73/jeff/ac0c
www.ac0c.com
--------------------------------------------------
From: "Joe Subich, W4TV" <lists@subich.com>
Sent: Wednesday, July 07, 2010 9:15 PM
To: "Jeff Blaine AC0C" <keepwalking188@yahoo.com>
Cc: <amps@contesting.com>; <k5jv@kingwoodcable.com>
Subject: Re: [Amps] QSK-1500 chip
>
> Jeff,
>
> > 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.
>
> I worked with John "Doc" Sheller (now K8RR) on the QSK-1500 some
> 30 years ago. I distinctly remember that the MC14011BCP requirement
> was added to the "service and technical manual" after the units
> were shipped due to the timing problems discovered when other
> manufacturers' devices were used at U3.
>
> John designed the circuit on a breadboard and just happened to have
> Motorola parts when he did it. The values of R4/C4 were selected to
> work with the TS-930 (or TS-940) that he owned at the time. It was
> only after the unit was in "production" (all the boards were stuffed
> and soldered by hand) that the critical nature of U3 came to light.
> While I have not studied the differences between the Motorola and
> other designs, I would suspect the input clamping in the Motorola
> design effected the charging rate of C4.
>
> 73,
>
> ... Joe, W4TV
>
>
> On 7/7/2010 8:31 PM, Jeff Blaine AC0C wrote:
>> 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@subich.com>
>> Sent: Wednesday, July 07, 2010 7:17 PM
>> To: <amps@contesting.com>; <k5jv@kingwoodcable.com>;
>> <keepwalking188@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@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
>>>>>
>>>>
>>>> _______________________________________________
>>>> Amps mailing list
>>>> Amps@contesting.com
>>>> http://lists.contesting.com/mailman/listinfo/amps
>>>>
>>>
>>
>>
>
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