[TowerTalk] Relay Specs - Coax switch

[Jim Lux]

Tom has raised a number of important issues for relay selection ....

I collected all the relay posts from a few years at
http://home.earthlink.net/~w6rmk/relay.htm

There's also the relays used inside things such as the various antenna
tuners. There's a somewhat different requirement set than an antenna
switch... to a certain extent such things as isolation and parasitic C and L
aren't as important because you'll be tuning them out by adjusting the
overall C and L.  You'd have to watch out for parasitic resonances (somehow,
I don't think any of the designers of these things actually looked for that,
though.. they probably just got lucky, or it's unlikely in the first place),
and losses could really bite you.

In an antenna switch, though, you need nice flat response and good
isolation, as well as reasonably low loss.


Anybody want to comment on the relays in the QST article?


----- Original Message -----
From: "Jim Lux" <jimlux at earthlink.net>
To: <keith at dutson.net>; "Towertalk" <towertalk at contesting.com>
Sent: Thursday, March 31, 2005 6:50 PM
Subject: Re: [TowerTalk] Relay Specs - Coax switch


> What impedance is your system?
>
> 2000Wrms (just to give a bit of margin) into 50 ohms is about 316Vrms,
call
> it 450V peak.
> 2:1 voltage margin is typical as a design requirement.
>
>
>
> However, if you, for instance, happened to have a quarter wavelength of
coax
> from amp to switch, and left it open at the switch end, the voltage could
be
> just a bit higher(!)  (although, the amp will be looking into a short, so
it
> probably won't develop full output power, either)
>
> ----- Original Message -----
> From: "Keith Dutson" <kjdutson at earthlink.net>
> To: <TowerTalk at contesting.com>
> Sent: Thursday, March 31, 2005 1:19 PM
> Subject: [TowerTalk] Relay Specs - Coax switch
>
>
> > I am home brewing a coax switch for the shack.  I want it to handle 1500
> > watts of power, but not to "hot" switch.  I am looking at PCB relays and
> > found many that handle 10 amps, but only a few that specify a high
> > dielectric voltage.  What kind of voltage should be expected out of a
> > legal-limit amplifier such as an Alpha or Ameritron?  TIA
> >
> > Keith NM5G
> >
> > _______________________________________________
> >
> > See: http://www.mscomputer.com  for "Self Supporting Towers", "Wireless
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any
> questions and ask for Sherman, W2FLA.
> >
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> _______________________________________________
>
> See: http://www.mscomputer.com  for "Self Supporting Towers", "Wireless
Weather Stations", and lot's more.  Call Toll Free, 1-800-333-9041 with any
questions and ask for Sherman, W2FLA.
>
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