Date: Fri, 25 Oct 2019 11:29:18 -0700
From: "Richard (Rick) Karlquist" <richard@karlquist.com>
To: n2ic@arrl.net, "towertalk@contesting.com"
<towertalk@contesting.com>
Subject: Re: [TowerTalk] Remote switch
On 10/25/2019 9:26 AM, Steve London wrote:
> Thanks for the tips on measuring isolation, Wes.
>
> Measured a few switches I had laying around. Old B&W round switch. 70 dB
> @ 3.5 MHz, 60 db at 28 MHz. Not bad, considering. Array Solutions 2
> antenna Stackmatch. 45 dB @ 14 MHz. Hmmm.
>
> 73,
> Steve, N2IC
<The legacy switches like the B&W shorted the unused ports
<to ground as a "lightning protection" feature. There was
<some switch advertised as "Protax" that had this.
<I believe for a wafer switch like this, it basically costs nothing
<to do it. With relays, it does cost something.
<Rick N6RK
## IF the UN used ports are shorted, I would suspect the
isolation would be almost infinite.
## easy to achieve with a 2 wafer rotary switch ..... AND multiple
pole rotors on 2nd wafer.
Also easy to achieve with spdt relays..... or dpdt relays with contacts
in parallel.
## with relays, COM of each relay is bonded to its respective port.
relay 1...port 1. relay 2..port 2 etc. ALL NC CONTACTS ARE
GROUNDED TO CHASSIS.
ALL NO CONTACTS are bonded to the input main 1.5 kw / rx buss.
## all de-energized relays have their respective ports center conductors
chassis grounded.
## The above is for simple 1 in.... and XXX ports out. Thick, wide
copper strap used to form
the 50 ohm stripline spacing between the pair of stacked 1 inch wide
cu straps was, I think aprx .25 to
.30 inches. That setup is used on the AS 20 kw 1 in, XXX ports
out remote switch boxes. The < 5 kw
versions will use PCB for the stripline.
## SPDT ceramic vac relays can also be used.
## For 2 in XXX ports out, typ 3PDT relays used....with contacts in
series.
## For stuff like 6 in and 10 out switches, typ used for indoor HF
commercial applications,
a cross bar matrix is used, complete with 16 x EIA flange connectors.
Jim VE7RF
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|