On 7/13/2012 1:45 AM, K8RI wrote:
> A small change inside a relay (that used to work) may drop the
> isolation to unacceptable levels and actually cause damage to one or
> more rigs.
Not if the overall switch is designed properly. If the switch is based
on two relays per antenna and unused antennas "float" relay capacitance
will cause coupling problems. However, if the switch uses three relays
per antenna with unused feedlines shorted (or terminated), a ground and
*two* open contacts between the antenna used by one transmitter and the
other transceiver as well as proper circuit board design, minor changes
in relay construction (or substituting similar relays from other
manufacturers will not significantly impact isolation.
73,
... Joe, W4TV
On 7/13/2012 1:45 AM, K8RI wrote:
> On 7/12/2012 11:43 PM, Jim Lux wrote:
>> On 7/12/12 10:54 AM, Larry Loen wrote:
>>> It appears this work has been done and maybe done to death.
>>>
>>> But for those of us who (like me) are new, can you expand a little,
>>> and, particularly, give a couple of links? What I see below is
>>> someone who knows the answer, but is speaking to others that know the
>>> answer, not to someone just getting started in this.
>>>
>>> I'm eventually going to want to make my station work remotely, so I'll
>>> be interested in high quality, high power coax switches that work well
>>> through at least HF and sometimes 6 meters. I had a handful of really
>>> good switches on a 1K amp I ran a while back, but those came from a
>>> trusted friend and I don't live in that state now anyway; sold the amp
>>> long ago.
>>>
>>
>>
>> The challenge is that relays that worked 15 years ago may not be
>> available today, or even if available, work today.
>
> These relays have to tolerate RF at the power and frequency run through
> them. They also have to provide isolation at that power and frequency
> when used in remote antenna switches. Even more so when they are used
> in set-ups where two or more stations may have access to the antennas.
> IOW with my Single Operator, 2 stations setup (SO2R), I may have the
> legal limit from two stations running through a switching set up that
> has power running through adjacent relays and wiring, yet the isolation
> between the two stations has to remain high enough so they do not
> interfere with each other, let alone cause damage.
>
> A small change inside a relay (that used to work) may drop the isolation
> to unacceptable levels and actually cause damage to one or more rigs.
>
> 73
>
> Roger (K8RI)
>
>
>>
>> Here's some notes from 2004
>> http://home.earthlink.net/~w6rmk/relay.htm
>>
>>
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