[Boatanchors] Cathode Keying Question

[Ian Wilson]

I have had trouble with reed relays trying to break that much current.
I have one
that welded its contacts closed under these conditions.

Have had no problems with MOSFETs as long as you pick one with high enough
breakdown voltage. I also have the Harbor Press Keyall waiting to be
built. Seems
like a great solution, and it's a "why didn't I think of doing it that
way" type of
circuit.

73, ian K3IMW

On Mon, Nov 16, 2009 at 6:52 AM, Ed - K9EW <k9ew57 at gmail.com> wrote:
> Hi Lee,
>
> Yes, you're absolutely right.  You need to key 120Vdc at 110mA.  A
> reed relay would do it, but why not go 20th century, and use a MOSFET.
>  Before you turn away, let me tell you that I've been keying my
> boatanchors (both cathode-keying and grid-block keying) with the same
> MOSFET circuit for several years now, and it's great.  You can buy a
> little kit from Jackson Harbor Press (
> http://home.att.net/~jacksonharbor/keyall.htm ) for $14.  There was
> also an article in a recent (well, maybe in the past year) QST for a
> similar circuit.
>
> I invite you visit my website ( www.k9ew.us ) where I have information
> on a BoatAnchor QSK project I put together.  You may get some ideas
> from that.
>
> 73, and have fun with your project.
> ed - k9ew
> www.k9ew.us
>
> On Mon, Nov 16, 2009 at 8:35 AM, Lee Buller <k0wa at swbell.net> wrote:
>>
>> I have a Knight T-50 and the VFO to go with it.  I am looking at making a TR switch that runs the VFO all the time while I key the T-50.
>>
>> I am a little flummoxed (confused) as to what the current and voltage is going through the cathode key of the T-50.  Unkeyed - the manual says 120 volts.  Keyed - the manual says zero volts.  Of course the the current keyed would be around 110 ma.  So, what I am working with here is 120 V and 110 ma at the key handle.
>>
>> Is my thinking right or am I off here?  Could a simple reed relay could handle these parameters?  The last time I did this was in 1965...and I used big old clunky relays.
>>
>> Lee Buller - K0WA
>>
>>
>>
>>
>> In our day and age it seems that Common Sense is in short supply.  If you don't have any Common Sense - get some Common Sense and use it.  If you can't find any Common Sense, ask for help from somebody who has some Common Sense.  Is Common Sense divine?
>>
>> Common Sense is the image of the Creator expressing revealed truth in my mind. -  J. Wolf
>>
>> ______________________________________________________________
>> Boatanchors mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/boatanchors
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:Boatanchors at mailman.qth.net
>>
>> List Administrator: Duane Fischer, W8DBF
>> ** For Assistance: dfischer at usol.com **
>>
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>>
> ______________________________________________________________
> Boatanchors mailing list
> Home: http://mailman.qth.net/mailman/listinfo/boatanchors
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Boatanchors at mailman.qth.net
>
> List Administrator: Duane Fischer, W8DBF
> ** For Assistance: dfischer at usol.com **
>
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html