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Author Topic: What kind of cable for a key?  (Read 8660 times)
W9KDX
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Posts: 770




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« on: August 17, 2011, 09:48:18 AM »

Sorry to keep bugging you guys with small questions.  I have found the right plug in my drawer of spare parts and I need to make sure I use the right kind of cord.  Is anything special required for a simple straight key, like shielding, or can I just use insulated 14 gauge wire?  If shielding is needed, let me know what type of cable works as I might have some around already.  I hate to spend for something I have spent years keeping around for just this need.

Thanks again,

Sam
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Sam
W9KDX
N2EY
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Posts: 3879




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« Reply #1 on: August 17, 2011, 09:53:34 AM »

#14 is way too heavy.

For almost all purposes, #18 to #22 wire is more than adequate. Most keying circuits have very little current flowing, and even old GB gear rarely gets over a few hundred mills.

I use #18 twisted pair I made up. Plastic "speaker wire" is good too.

Stranded is better than solid. Use two different colors and make sure the grounded side of the circuit goes to the ground side of the key (the side that includes the base and lever arm)

What sort of key, rig and plug?


73 de Jim, N2EY
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KQ6Q
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Posts: 976




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« Reply #2 on: August 17, 2011, 02:26:28 PM »

for paddles you may want to use 2-conductor shielded cable. Unfortunately, it comes in a 25 foot roll when all you need is a couple of feet. I can mail you some if you like - have plenty left over!
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W9KDX
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Posts: 770




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« Reply #3 on: August 17, 2011, 06:04:36 PM »

The radio is a Yaesu FT-950 so I know I need to use a three conductor plug and I am starting with an AMECO basic K4.
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Sam
W9KDX
KC9HOZ
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Posts: 103




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« Reply #4 on: August 18, 2011, 08:10:27 AM »

I used a CD-to-soundcard audio cable from an old computer to wire my paddles.  It is a three conductor shielded cable in the #18-20 gauge range.

Scott
kc9hoz
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W5LZ
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Posts: 477




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« Reply #5 on: August 18, 2011, 08:12:34 AM »

For a typical straight key a simple two conductor cable should work just dandy.  Using a shielded two conductor cable certainly won't hurt if you wire it correctly.  Or, a single conductor shielded cable (RG-174 comes to mind) can work just fine too.  It really isn't that big'a deal at all.
 - Paul
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K7GLM
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Posts: 51




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« Reply #6 on: August 18, 2011, 12:35:55 PM »

I have heard about people blowing keying circuits in the FT-897 due to having too much RF on the paddle leads. I always go with shielded cable and wrap through a ferrite a couple of times at the back of the radio. YMMV.
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W9KDX
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Posts: 770




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« Reply #7 on: August 18, 2011, 03:01:57 PM »

I all of a sudden got the feeling that when you guys say "shielded" I should be hearing "coax".  I have a ton of coax, RG-58, RG-8U, RG-8X.  Are any of these what I actually need?  I think the RG-8X has a braided center wire, so I would prefer that is viable.
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Sam
W9KDX
K7KBN
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Posts: 2801




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« Reply #8 on: August 18, 2011, 03:30:58 PM »

No -- "shielded" cable is generally two or more conductors with an overall braided shield.  "Coaxial cable" is shielded, but it's only one conductor, and the construction is a lot different.

Don't overthink things.  A key is nothing more than a single pole, single throw switch.  Off.  On.  Two conductors; don't have to be shielded unless the rig manufacturer recommends it.
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73
Pat K7KBN
CWO4 USNR Ret.
K8AXW
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Posts: 3827




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« Reply #9 on: August 18, 2011, 09:17:34 PM »

Radio Shack sells microphone cable.  It is a single conductor with shield.  The name of the game is flexibility, then small..... I use RG-174 for my straight key.  It is a VERY small coax.Two conductor with shield mic cable is also easily found for paddles to keyer.

A shield is really isn't necessary.  If you wish, take three stranded wires and twist them together and wire up your key, paddles and keyer.  Think KISS!
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KC9TNH
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Posts: 304




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« Reply #10 on: August 19, 2011, 06:04:15 AM »

The radio is a Yaesu FT-950 so I know I need to use a three conductor plug and I am starting with an AMECO basic K4.
You do not necessarily need a 3-conductor plug just for a straight key; but it may be convenient later. Here's what I did to accomodate both paddle and straight-key, to the typical baby-size (and therefore fragile in my book) key interface on a Yaesu radio:
- Couple feet of cheapo 18-ga speaker wire for the straight key to a 3.5mm mono plug. As was mentioned, this isn't rocket science, it's a switch. It's flexible, and wraps around the Mae West key base for when it goes walkabout in the bag with the 817.
- 3-conductor braided cord from the paddle into a 3-conductor (read "stereo") 1/4" to mini plug adapter. I used the original braided 60's style cord that came with the Vibroplex because I'm lazy, it still works, and soldering 3 conductors onto a mini-plug is a PITA (for me).

From the key interface on the rig back under the table is a simple M-F (mini) stereo extension cord; that lets me quickly change to/from SK to paddle if I want (also changing the rig's option). The 3-conductor into the rig covers both bases but, again, you don't need 3 conductors for a straight key only.

 Wink K8AXW: Thanks for the thought about the mic-cable. From my wild band days I have some of that laying around & may retire the vintage Vibroplex paddle cable.
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73
Wes -KC9TNH
"Don't get treed by a chihuahua." - Pete
W9KDX
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Posts: 770




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« Reply #11 on: August 19, 2011, 07:20:39 AM »

The radio is a Yaesu FT-950 so I know I need to use a three conductor plug and I am starting with an AMECO basic K4.
You do not necessarily need a 3-conductor plug just for a straight key...

In this case I do.  Yaesu is very clear that a Mono plug will just short out the connection and generate a constant tone.  2-conductor plugs connect the wrong circuits.
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Sam
W9KDX
KB7QOA
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Posts: 17




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« Reply #12 on: August 19, 2011, 11:44:00 AM »

For my FT-857 I use an old computer audio cable I had laying around.  It was about 6 feet long, and has the green 3 conductor TRS 1/8" plug on both ends.  I simply cut it in half, ran the shield to the center of my paddle, red to the right "DAH" terminal, and the white to the left "DIT" terminal.  If I recall correctly, my straight key uses the shield and the red conductor, but I may be mistaken and it could be the white.

Nearly every computer monitor has speakers built-in these days so there is an abundance of those cables out there.  It is a "universal" cable and in nearly all cases the cable outlasts the monitor and either is replaced when still good or is not replaced when a monitor is changed.  Ask somebody that works with computers to save a few for you and you'll probably end up with more of them than you'll ever be able to use.  I have a drawer full of them and use them for lots of various projects, sometimes keeping the plugs and sometimes just using them for the 2 conductor plus shield cable.
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KC9TNH
Member

Posts: 304




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« Reply #13 on: August 19, 2011, 12:44:50 PM »

The radio is a Yaesu FT-950 so I know I need to use a three conductor plug and I am starting with an AMECO basic K4.
You do not necessarily need a 3-conductor plug just for a straight key...

In this case I do.  Yaesu is very clear that a Mono plug will just short out the connection and generate a constant tone.  2-conductor plugs connect the wrong circuits.
Okey-doke. I only have two Ysu's; both of them have the menu option to select what you have plugged in (key or paddle) and then turn the internal keyer on/off. I see their explanation of the keying voltages present now that you're talking about; got it. 3-conductor it is.

(Nice looking rig by the way.)
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73
Wes -KC9TNH
"Don't get treed by a chihuahua." - Pete
N3QE
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Posts: 2190




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« Reply #14 on: August 19, 2011, 12:59:04 PM »

Any old random wires will work.

14 gauge is probably too thick to comfortably put into any 1/8" plug but may be fine for a 1/4" plug.

If the key is going to be relocated a lot maybe even a coily-cord would be a good idea. Shifting key position is a good idea to prevent glass arm.

If you want the cable to last for an extended period, it has to be properly strain-relieved at both ends and depending on the hardware at both ends you might prefer one type of cabling over another.
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