A fairly recent issue of QEX had a very nice design for a 1x8 switch. The key
features were a radial layout of the "8 side" connectors to maximize spacing
while minimizing length of runs, and the utilization of a pair of relays in
series to do the switching in order to maximize isolation. Definitely worth a
look.
Al
AB2ZY
________________________________________
From: Amps <amps-bounces@contesting.com> on behalf of Jim Garland
<4cx250b@miamioh.edu>
Sent: Friday, August 1, 2014 10:26 AM
To: amps@contesting.com
Subject: Re: [Amps] Circuit Board Question
I use 0.25 inch trace widths on 1 oz copper (tinned w/solder mask) on a
.063" PCB. Lenghs are under 1.5 inch, with PCB-mount power relays doing the
switching. Tested extensively at 2.5 KW from 1.8-30 MHz with no problems.
73,
Jim W8ZR
> -----Original Message-----
> From: Amps [mailto:amps-bounces@contesting.com] On Behalf Of
g8on@btinternet.com
> Sent: Friday, August 01, 2014 2:47 AM
> To: amps@contesting.com
> Subject: Re: [Amps] Circuit Board Question
>
> According to the ITT 'Reference data for radio engineers', 3 oz
(0.0042inches thick) copper
> will give you 3.5 skin depths at 1.8 MHz.
> At 30 MHz, one skin depth is 0.00048 inches.
>
> At DC and LF, a conductor width of 0.1 inch would give you a temperature
rise of 10C at
> 10 amps. (MIL-STD-275C)
>
> I would use about 0.2 inch spacing, but if the unit is where condensation
can be a problem,
> it would be worth using a coating of varnish.
>
> My switching unit uses a normal receiving type ceramic switch, about 1.25
inches across,
> with clips on both sides, driven by a Ledex. The traces are 50 ohm traces
on 1 oz copper
> (about 3/16 inches wide or so), none more than about 3 inches long. The
SWR is about 1.2
> at 30 MHz and it has been running quite happily since 1996 in an unheated
shed at the base
> of the tower. No varnish on the board, just a tin dip.
>
> 73
>
> Peter G3RZP
>
>
>
> ----Original message----
> From : maflukey@gmail.com
> Date : 01/08/14 - 07:19 (GMTDT)
> To : amps@contesting.com, towertalk@contesting.com
> Subject : [Amps] Circuit Board Question
>
> Could someone help me out with some advice.
>
>
>
> How much separation between circuit board traces in an antenna switch box
> would be recommended to reliably handle the voltage associated with legal
> limit at 2:1 SWR?
>
> Just tinned or conformal coating?
>
> How wide would you recommend the trace to handle the same signal using 3oz
> board stock - longest trace is about 2", most less than 1"?
>
>
>
> Thanks in advance
>
> Matt
>
> KM5VI
>
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