Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

donate to eham
   Home   Help Search  
Pages: [1]   Go Down
  Print  
Author Topic: V and A values when connecting key to 7300?  (Read 1545 times)
HAMSTUDY
Member

Posts: 477




Ignore
« on: January 20, 2018, 11:02:18 AM »

When connecting a straight key to an Icom 7300 I get about 3.25 Volts between the key and 7300 and when I key down I get about .07 mA (67-70 uA).  Do those values sound about right?  Thx
Logged
K0UA
Member

Posts: 1817




Ignore
« Reply #1 on: January 20, 2018, 01:13:52 PM »

I dunno.. never tried to measure it... If I may ask, why would you want to? I just go into the menu an tell it what is connected to the port (straight, paddle or bug) and then start using it.
Logged
SOFAR
Member

Posts: 1029




Ignore
« Reply #2 on: January 20, 2018, 01:26:25 PM »

When connecting a straight key to an Icom 7300 I get about 3.25 Volts between the key and 7300 and when I key down I get about .07 mA (67-70 uA).  Do those values sound about right?  Thx

A key is nothing more than a switch.

Why are we over-analyzing this?
Logged
PA0WV
Member

Posts: 401




Ignore
« Reply #3 on: January 21, 2018, 09:24:03 AM »



A key is nothing more than a switch.

Why are we over-analyzing this?

Maybe because he wants to key the transmitter with a keyer, and has to know the current, and the open voltage being positlive or negative to ground?

73
Wim PA0WV
Logged

K0UA
Member

Posts: 1817




Ignore
« Reply #4 on: January 21, 2018, 09:48:07 AM »



A key is nothing more than a switch.

Why are we over-analyzing this?

Maybe because he wants to key the transmitter with a keyer, and has to know the current, and the open voltage being positlive or negative to ground?

Why would he want to do that?  It has a very nice built in keyer.  It truly is a mystery to me.

73
Wim PA0WV
Logged
K8AXW
Member

Posts: 6578




Ignore
« Reply #5 on: January 21, 2018, 10:37:48 AM »

Wim:  He named the brand of radio and no question(s) about polarity so no problem with any keyer handling the current or voltage.

With my CMOS II keyer, I had to add a modification because I have one rig that will not key with this keyer.  But all other rigs key properly without the mod.

If he was cathode keying......that's a different story.  Even with a keyer that uses a relay for keying he would need to know the current/voltage rating to be sure the relay could handle the current.

I've never heard of anyone needing to know the I/E across a key with a modern rig.  Of course there is nothing wrong with knowing this information and can be filed with other irrelevant things.   Grin
Logged

A Pessimist is Never Disappointed!
HAMSTUDY
Member

Posts: 477




Ignore
« Reply #6 on: January 21, 2018, 01:41:52 PM »

Just curious.  Happened to notice that the recommended plug was a standard 1/4" plug; had one of those around and cut the connector off the other end off so I could hook the wires to the key.  Noticed that in this particular (old/1970s?) cable the wire strands were very small; almost too small to reliably (with some reasonable mechanical strength) connect to the key terminals.  Setting aside the fragile nature of the wires I figured if they could handle hifi signals they should be good for just keying the "switch", but the hair size diameters of the strands got me thinking about how much V and A were actually involved.  So I measured and got the results I shared.  No big deal but if anyone happens to have a DMM I'm curious to see what values you get.  Thx
Logged
K0UA
Member

Posts: 1817




Ignore
« Reply #7 on: January 21, 2018, 02:27:51 PM »

The wire in your cable is called Tinsel wire. It is common in some audio and many telephony cables. Very difficult to solder, and as you noted has low mechanical strength by itself.  Most of its strength is derived from the string it it usually wound around and its jacket material. With the low voltages and low currents required here for keying your rig, you are not going to have a problem with this wire carrying the load.  Tinsel wire is made so that the cable is "soft" and flexible and can be flexed for a long time without breaking inside.
Logged
HAMSTUDY
Member

Posts: 477




Ignore
« Reply #8 on: January 21, 2018, 03:50:39 PM »

The wire in your cable is called Tinsel wire. It is common in some audio and many telephony cables. Very difficult to solder, and as you noted has low mechanical strength by itself.  Most of its strength is derived from the string it it usually wound around and its jacket material. With the low voltages and low currents required here for keying your rig, you are not going to have a problem with this wire carrying the load.  Tinsel wire is made so that the cable is "soft" and flexible and can be flexed for a long time without breaking inside.

Thanks.  I have a bunch of older RCA cables like this but never knew the wires inside are called Tinsel.  Just as you described the outside jacket and the wires themselves are very pliable; it was hard to even get the wires to twist together on themselves but after some fiddling I was able to tin the bunch and then solder a piece of 18 AWG solid wire onto the bunch.  Added some heatshrink and the whole thing should be strong enough stay attached to the key terminals and to carry electrons but not much weight.  I figured the V and A would be ok but after putting the cable together I measured just to see what was present.  At that point the measuring was a lot easier than the soldering had been.  According to Wikipedia (now that I know to look under "Tinsel") the spec is 0.5A so it should be fine electrically.  Again, no big deal, just trying to learn and enjoy the hobby.  73
Logged
K0UA
Member

Posts: 1817




Ignore
« Reply #9 on: January 21, 2018, 06:09:07 PM »

Cool.  We understand now.  I figured there was a reason you asked, but it eluded me.  It is all about learning. And you learned how maddening it is to solder and work with tinsel wire cables. When I first encountered them, I made up some new curse words.   Grin
Logged
K8AXW
Member

Posts: 6578




Ignore
« Reply #10 on: January 21, 2018, 09:58:05 PM »

UA:  I thought I knew them all!  Sad
Logged

A Pessimist is Never Disappointed!
K0UA
Member

Posts: 1817




Ignore
« Reply #11 on: January 21, 2018, 10:47:59 PM »

UA:  I thought I knew them all!  Sad

I bet I could have taught you some new ones the day I dropped a big hot blob of solder down on top of my nylon sock. It is way worse than dropping solder on to your bare skin.  Something about molten nylon just seems to burn and melt to your skin. Like sticky napalm or something.  Cotton socks don't do that, they insulate you.
Logged
Pages: [1]   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!