> Steve,
>
> This switch will work very well at VHF and UHF frequencies. See:
> <http://www.eham.net/classifieds/detail/75982>
>
> Big photo at: <http://www.w2fla.com/switch.jpg>
>
> Regards,
>
> Sherm
> W2FLA
>
[Steve Katz] Hi Sherm, I looked at the photos and I don't see why
this design would work at VHF or UHF -- lots of series inductance shown
there (buss wiring between rotary switch and SO-239 connectors), lots of
stray capacitance in such a design, too. I'd wager to guess that on a
network analyzer, this switch looks bad above about 50 MHz, but if you'd
like me to measure it, I surely can, in about five minutes. The Transco
switches I referred to aren't anything like this, they are built as a
rotating 50 Ohm coaxial line section activated by a motor, kind of like a
motorized Bird Electronics coaxial switch (the kind you have to push,
rotate, then pull, to move from one port to another). That's the kind of
design that has <0.2 dB loss at 1 GHz and >60 dB port to port isolation.
-WB2WIK/6
> At 11:01 AM 02/04/2003 -0800, you wrote:
>
>
> Homebrew switches using relays do not fare well at VHF, and less so
> at UHF.
> Relay and wiring reactance takes over pretty quickly. Even using
> small form
> factor relays interconnected by a good circuit board layout such as
> Ameritron does, performance drops off pretty quickly above 144 MHz
> for the
> "control line" version, and the "biased through the coax" version is
> worse.
>
> For VHF-UHF remote antenna switching, I'd go with surplus Transco
> motorized
> coaxial switches. Pretty much what everybody uses at VHF and above,
> most of
> the Transcos are good to at least 2 GHz, some higher.
>
> -WB2WIK/6
>
> "Success is the ability to go from failure to failure with no loss
> of
> enthusiasm." -Winston Churchill
>
> > -----Original Message-----
> > From: KG4QDZ [SMTP:kg4qdz@arrl.net]
> > Sent: Tuesday, February 04, 2003 9:46 AM
> > To: towertalk@contesting.com
> > Subject: Re: [TowerTalk] Remote Antenna Switches
> >
> > I am trying to design something similar.
> > Have you measured loss? How do you think these would do at VHF/
> low UHF
> > freqs? Has anyone tried these at higher freqs?
> >
> > 73 Skip (KG4QDZ)
> >
> >
> > ----- Original Message ----- >
> > > I made my own switch box. I used 10 amp Radio Shack relays. I
> have had
> > one
> > > relay burn up on me when I was having trouble with one of my
> mono
> > banders,
> > > and I burned the insulator on an SO-239 when the PL-259 barrell
> > loosened.
> > I
> > > run 1500 watts cw & ssb, 160, 80, 40, 30, 20, 15 & 10, and the
> box has
> > been
> > > in service for 9 years. 1500 watts into 50 ohms will have about
> 5 1/2
> > amps
> > > of current.
> > >
> > > And the relays are very similar to the ones in an Ameritron
> relay box
> > that
> > > was given to me.
> > >
> > > As long as the spring contacts have sufficient power rating, a
> little
> > follow
> > > (wiping action) when the contact makes or breaks, and mounted so
> the
> > relay
> > > springs are vertical (so any dust will fall out), You should be
> able to
> > use
> > > just about anybodies box.
> > >
> > > de Paul, W8AEF
> >
> >
> > _______________________________________________
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> > TowerTalk@contesting.com
> > <http://lists.contesting.com/mailman/listinfo/towertalk>
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