On Sep 27, 2010, at 9:10 PM, "Jim Thomson" <jim.thom@telus.net> wrote:
> Date: Mon, 27 Sep 2010 20:50:48 -0700
> From: Jim Lux <jimlux@earthlink.net>
> Subject: Re: [TowerTalk] X99KP 12VDC RELAY FOR AMERITRON REMOTE
> ANTENNA SWITCHES
>
>
> And just how do you think they do a "double make" contact? :)
>
> Bridge the two armature contacts on a dpdt or dpst relay and you get a double
> make spdt or spst.
>
> ## whoa. P+B makes SPST-DM relays. They are configured just like any
> contactor. It's 2
> sets of contacts IN SERIES. The COM [ moveable part] is shaped like a 'T'...
> and comes crashing
> down on the TWO 'throws. One throw is the input, the 2nd throw is the
> output. Contactor's
> are built the same way, except times two or three. The concept is when
> shutting off stuff like
> motor's, etc, the back emf is split into TWO gaps, = zero arcing.
>
> ## IF you take a DPDT or DPST relay, and parallel all the contacts, you
> just get a
> higher current rated SPDT or SPDT. I dunno if you would call it DM.
Not exactly. In the bridge the armature scheme, the contacts are in series,
just like the pb relays you describe. Granted the usual t shaped armature
thing as contractor isn't really rf suitable, at least at 30MHz
> I would call it
> redundant contacts. It's an excelllent config, when using mech realys for
> remote switch's.
> If you double the current rating, you quadruple the power rating. The way the
> poer can go open is
> if both contacts go open.
>
> ## The only other config that is reliable is vac relays.
>
> Jim VE7RF
>
>
>
>
> On Sep 27, 2010, at 8:39 PM, "Ron W8RJL" <youngron@verizon.net> wrote:
>
>> For anyone who might be confused by the armature and parasitic verbage here
>> is what Allan Bradley has to say about Form X relays:
>>
>>
>> A Form X contact arrangement is one which has single-pole, single-throw,
>> normally open double-make contacts. The function of this arrangement is to
>> close a circuit when actuated.
>>
>> Forget about parasitics and armatures. It is just a contact configuration.
>>
>> 73,
>> Ron W8RJL
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