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Need coax relay to switch ant between K2 & K3

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Alan D. Wilcox, W3DVX

Need coax relay to switch ant between K2 & K3

Hello,

The saga of my K2 in the upstairs office and the K3 downstairs in the
shop continues.

Solution:
1. Run coax from the K2 into the attic; run some red/blk zip cord up too.
2. Chop the K3 coax going to the antenna and run the K3 end into the attic.
3. Run the remaining end of the coax from the antenna into the attic.
4. PL-259s to the 3 wires in the attic.
5. Connect K2, K3, ant to coax relay.
6. Zip cord to relay (12 vdc or 110 ac); other end gets power when I
turn on the K2 supply.

I had a Dow-Key coax relay (just what I want) on my Viking II. Both long
gone.

Anyone have one or something that'll do the trick? Any extra PL-259's
with sleeve for smaller coax?

Many thanks!
Alan

Alan D. Wilcox, W3DVX (K2-5373, K3-40)
570-321-1516
http://WilcoxEngineering.com
Williamsport, PA 17701

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w8fn

Re: Need coax relay to switch ant between K2 & K3

The Top Ten Devices A/B switch will work very well for this
application. It even has a lockout so you cannot "steal" the antenna
from the currently selected port. You will need a control signal that
pulls to ground to activate the A and B selection. A pair of simple
open collector transistors controlled by the +12V output on their
respective radios will do the trick. Run a +12V supply and the two
control lines to the switch. The power supply commons ("grounds") of
the two radios must be tied together somewhere to make this scheme
work, however.

I use one of the A/B switches to switch the output of the B side of
my Array Solutions SixPak between the Sub receiver on my K3 in single
radio mode and the second radio in two radio mode. It works great,
and the switch has very good isolation between the two ports.

73...
Randy, W8FN

>I had a Dow-Key coax relay (just what I want) on my Viking II. Both long
>gone.
>
>Anyone have one or something that'll do the trick? Any extra PL-259's
>with sleeve for smaller coax?

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Don Wilhelm-4

Re: Need coax relay to switch ant between K2 & K3

In reply to this post by Alan D. Wilcox, W3DVX

Alan,

I would suggest something a bit more complex than a simple SPDT relay to
switch between the K2 and K3.
Considering that the antenna should be disconnected when not in use, I
would devise a priority scheme - it would take 3 relays. Two would
switch RF between the antenna and a dummy load. The third would switch
the DC feed to the two RF relays depending on which transceiver has
priority (the K2 or the K3) and the power on state of the K2 or the K3.

Yes, that would take 2 dummy loads, but provides a safe load if the
antenna is not selected for either the K2 or the K3. The priority is
your choice - if you want the K3 to be the priority transceiver, its
power on state will prevent the K2 antenna relay from activating (or
vice-versa).

Tha downside is that if you forget to turn off the K3, you will have to
make a trip to the K3 to turn it off before you can use the K2. The
up-side is that you will always have a safe load to boht the K2 and the
K3 and if you power off the rig when not in use, you will have some
protection from lightning surges on both rigs. Instead of "disconnect
the antenna when not in use", you will have implemented a "power off
when not in use" mechanism that will automatically disconnect the
antenna and connect the rig to a dummy load.

I am working on a similar situation, but I am using mechanical rotary
switches in the hamshack. Of the 3 HF antenna feeds and 1 6 meter feed
coming into the shack, any unused antenna feeds will be routed to the
basement workshop. In the hamshack, the K3 has the priority choice of
antenna feeds, the Yasesu FT-847 has the second choice and the remaining
coax feed is sent to the workbench. The K3 and FT-847 are protected by
dummy loads when powered off, but the workbench feed is manual - i.e. at
the workbench I must physically disconnect the antenna from any rig on
the bench when not in use. Mine is more complex because the 6 meter
must connect to the HF antenna jack on the K3 while the 6 meter feed on
the FT-847 is separate from the HF input.

You will have to come up with your own system based on your particular
desires and priorities. A bit of thought and "midnight sketches" may be
in order.

73,
Don W3FPR

Alan D. Wilcox wrote:

> Hello,
>
> The saga of my K2 in the upstairs office and the K3 downstairs in the
> shop continues.
>
> Solution:
> 1. Run coax from the K2 into the attic; run some red/blk zip cord up too.
> 2. Chop the K3 coax going to the antenna and run the K3 end into the attic.
> 3. Run the remaining end of the coax from the antenna into the attic.
> 4. PL-259s to the 3 wires in the attic.
> 5. Connect K2, K3, ant to coax relay.
> 6. Zip cord to relay (12 vdc or 110 ac); other end gets power when I
> turn on the K2 supply.
>
> I had a Dow-Key coax relay (just what I want) on my Viking II. Both long
> gone.
>
> Anyone have one or something that'll do the trick? Any extra PL-259's
> with sleeve for smaller coax?
>
> Many thanks!
> Alan
>
> Alan D. Wilcox, W3DVX (K2-5373, K3-40)
> 570-321-1516
> http://WilcoxEngineering.com
> Williamsport, PA 17701
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>
>

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W7GJ, Lance

Re: Need coax relay to switch ant between K2 & K3

In reply to this post by Alan D. Wilcox, W3DVX

Hello Alan,

I had used a home built vacuum relay on 6m to switch between antennas, but the
isolation was not good - possibly due to a problem with dirty contact in the old
relay or something. Anyway, I built a very nice SPDT coaxial switch that will handle
plenty of power up through 6m with low SWR, and you could easily do the same thing
with a DPDT coaxial switch done the same way. In fact, mine was based on a design by
WA4NFP for a durable, low loss DPDT switch to switch an amp in and out of the circuit.

You can put any type of connectors you want on it:

http://www.bigskyspaces.com/w7gj/relay.htm

GL and I hope you find this information helpful. VY 73, Lance

On 7/30/2010 1:09 AM, Alan D. Wilcox wrote:

--
Lance Collister, W7GJ (ex: WN3GPL, WA3GPL, WA1JXN, WA1JXN/C6A, ZF2OC/ZF8, E51SIX, 3D2LR)
P.O. Box 73
Frenchtown, MT 59834 USA
QTH: DN27UB
TEL: (406) 626-5728
URL: http://www.bigskyspaces.com/w7gj
2m DXCC #11/6m DXCC #815

Interested in 6m EME? Ask me about subscribing to the MAGIC BAND EME email reflector!
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W8JI

Re: Need coax relay to switch ant between K2 & K3

Vacuum relays can be quite good, as can a proper traditional relay, but all
are only as good as the designer's ability to understand ground loops.

All isolation shortfalls come from either the wrong style relay, or a bad
layout with ground loops or crosstalk between RF conductors. Many of the
problems are because people insist on grounded unused ports, and the ground
point has RF currents flowing through a common ground lead with a signal
path. Worse yet, what applies to RF isolation generally applies to
lightning.

Most trouble occurs because people forget the shield carries exactly the
same current as the center conductor, and even one inch of path can drop
enough voltage to cause a coupling problem.

If we look at the highest isolation switches on the market, the RCS-8V and
the DXE switches, neither depend on RF shield currents flowing through the
circuit boards. Neither use a groundplane transmission line on the boards.
Both have connectors on a single flat plate with a design for radically
flowing shield currents from the center common point. The sheet metal the
connectors mount to is the signal groundplane.

Most "trouble" occurs when people try to run RF grounds up through a
groundplane on a circuit board or through point to point wiring. This is
true in radio, audio lines, and antenna switches. It isn't good for
lighting, ground loops, or RFI unless grounds go to a good common wall with
very low impedance, solid connections, and well-planned current flow.

73 Tom

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W8JI

Re: Need coax relay to switch ant between K2 & K3

> Both have connectors on a single flat plate with a design for radically
> flowing shield currents from the center common point.

That should, of course, have been "radially flowing currents" and not
"radically flowing currents". Darn auto-correct.

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Alan D. Wilcox, W3DVX

Re: Need coax relay to switch ant between K2 & K3 CONCLUSION

In reply to this post by Alan D. Wilcox, W3DVX

All,
Thanks so much for all the responses! Happily, the simple solution will
work for me, because neither the K2 nor the K3 is ever hooked to the
antenna unless it's going to be used. Because I'm the only op, only one
can be used at one time.

That gets me to a simple coax relay solution. Don't want to cut holes in
box, mount connectors, etc; just taking something to the hot attic will
be plenty for me.

One of my clients, for whom I built a KPA100 and tuned his K2 last, saw
my posting. He has a like-new Dow-Key that he's sending (thanks Chuck),
and that'll solve the major problem. All Electronics had the zip cord
and 259's with RG-8x sleeves, so I'll be all set to start soon.

Thanks again,
Alan

Alan D. Wilcox, W3DVX (K2-5373, K3-40)
570-321-1516
http://WilcoxEngineering.com
Williamsport, PA 17701

Alan D. Wilcox wrote: