Knife Switch
 

My weekend project, last weekend, involved 100' of wire and a ladder.
My new random works great and supplements the 50' one I had up
already. Since I have 2 receivers on my desk, I decided to find an
inexpensive way to switch them. Using a pair of DPDT knife switches
(SPDT would have worked also), I wired each radio to the center pole,
the 50' antenna to one side and the 100' to the other. I can now
switch between antennas with ease. I mounted the switches upside-down
to the bottom of a shelf within easy reach of the radios. This lets
the gravity hold the switch straight down when not in use, keeping the
antennas disconnected for an added measure of lightning protection. I
was concerned about signal loss through the switch but I haven't
noticed any compared to connecting the antenna straight to the
receiver. Thankfully I live in a fairly low-noise rural area.

The probem I have is the only knife switches I could find were cheap
Radio Shack models (Universal sells the same ones). The pivot points
are riveted and the metal fairly thin. I'd like to find a more robust
switch, but I haven't been able to locate anything locally or on the
internet. I remember my grandfather having a bunch of heavy, ceramic
based, copper armed switches in his workshop...

Does anyone know a source where I could find some high-quality knife
switches?

Dean

Satellit 800
Realistic DX-160
Sony 7600GR
Grundig FR-200 (junk)
MFJ-1020C

Does anyone know a source where I could find some high-quality knife
switches?

Dean


Ebay?? I'd imagine that demand and therefore winning price would be low.

You could also use toggle switches.

You can never have too many antennas, have fun!

jw
K9RZZ

Dean wrote:

Does anyone know a source where I could find some high-quality knife
switches?


Is it possible to drill out the rivets and replace them with machine
screws and a spring washer? That way the tension could be set to what
you like. A nylon throated self locking nut would stay where you put it,
keeping the adjustment where you left it. A regular flat washer between
the spring one and the head of the bolt would be a good addition.



mike

Hardware stores may still have pocelain based knife switches. Shack's switch
has a fiber base.

Bill, K5BY

I've considered replacing the rivets with screws, and I still may, but
it will only fix one of the shoddy construction issues with this
switch.

I'm off to check Ebay next (good idea, I hadn't considered it)

If all else fails, maybe I'll try some high quality toggle switches...

Dean

"Dean" wrote in message
om...
I've considered replacing the rivets with screws, and I still may, but
it will only fix one of the shoddy construction issues with this
switch.

I'm off to check Ebay next (good idea, I hadn't considered it)

If all else fails, maybe I'll try some high quality toggle switches...

Dean

Just a thought. My radio is an Rx-320, so I'm always concerned about noise
(computer and otherwise). My primary antenna is a folded dipole in my roof,
connected via 300 to 75 ohm tv transformer to coax to my receiver. The
setup is quite good at reducing/eliminating household noise.

I'm considering adding additional antennas to be fed by coax. I will
probably use cable A-B switches, or the 'multi' switch type coaxial switches
found at Wal-Mart to switch antennas. My thought was that a knife switch
located near the radio would act like an antenna as far as household noise
is concerned, while the coax, properly grounded, would help to eliminate
noise.




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I'm sure you're correct, the knife switch does act as an antenna in
some way. For my current setup, I have unshielded lead-in line which
is acting as an antenna also, so the knife switch's noise input is
trivial.

I live in a rural area of New Mexico, in an adobe house. My radios
are far from my TV's and the only real noise I contend with is the
electric clothes dryer. Lucky, I guess.

Terry wrote:

Between the TVs, VRCs, PIR outside lights, bug-zappers
(A UV light with a nasty HV section fry bugs),
and the 1001 other noise sources. hearing anything on
SW is sometimes impossible.

Those bug zappers should be outlawed. They kill more beneficial insects
than bad ones. A rumour should be started that they cause sterility or
cancer in humans.



mike

In article KwpFc.45252$_5.16297@clgrps13,
m II wrote:
Terry wrote:

Between the TVs, VRCs, PIR outside lights, bug-zappers
(A UV light with a nasty HV section fry bugs),
and the 1001 other noise sources. hearing anything on
SW is sometimes impossible.

Those bug zappers should be outlawed. They kill more beneficial insects
than bad ones. A rumour should be started that they cause sterility or
cancer in humans.

Just point out that to get mosquitos, you need one of those expensive
CO2 lures that need a tank of propane, and that an ordinary bug zapper
just attracts sh*t eating flies.

And blows them to bits all over their BBQ grill.

(It was in the science press a couple of years ago, reporting a study
an Entomologist did of what UV bug zappers actually killed).

Mark Zenier Washington State resident