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

   Home   Help Search  
Pages: [1]   Go Down
  Print  
Author Topic: Using a DB9 A/B Switch to Support Two Serial Ports  (Read 1049 times)
KF9SQ
Member

Posts: 4




Ignore
« on: November 20, 2004, 09:57:44 AM »

I want to use a CW HARD KEYING interface on my PC. However, I only have one DB9 serial port. I see some cheap A/B switches on the market, but I wonder if they are safe for the PC and the rig.

If they are OK to use, is it safe to switch from one serial cable to another while either the PC or the rig is on?
Logged
AA6YQ
Member

Posts: 1807


WWW

Ignore
« Reply #1 on: November 20, 2004, 11:37:30 PM »

You could do that, but its probably not much more expensive to add a second serial port to your PC, either a PCI card or a USB adaptor. Then you wouldn't need to manually switch.

    73,

         Dave, AA6YQ
Logged
KF9SQ
Member

Posts: 4




Ignore
« Reply #2 on: November 21, 2004, 02:38:36 AM »

Good idea!  Thanks....
Logged
WA9SVD
Member

Posts: 2198




Ignore
« Reply #3 on: November 29, 2004, 09:04:02 AM »

Adding a USB port won't help much if the software and hardware are looking for a "COM:" type port to accomplish keying.  The DB-9 switch should work in theory; one of the specs for RS-232 is that the lines are SUPPOSED to be short circuit proof, and thus there shouldn't be any (physical)  damage caused by switching.  Unfortunately, you can only be sure by trying the switch.  Some operating systems will not recognize that a switch has occurred, or worse yet, get confused by the change, and the port won't work either way properly without a re-boot.  (BUMMER.)
    Try the switch.  Good luck!
 
Logged
AA6YQ
Member

Posts: 1807


WWW

Ignore
« Reply #4 on: November 29, 2004, 09:25:22 AM »

WA9SVD wrote "Adding a USB port won't help much if the software and hardware are looking for a "COM:" type port to accomplish keying."

That's not correct! USB serial port adaptors include virtual com port drivers, and thus appear like a native serial port to Windows, applications, and external hardware. I use such adaptors from MicroHam, Belkin, VSComm with a wide range of amateur radio software, as do many other hams.

    73,

       Dave, AA6YQ
Logged
WA9SVD
Member

Posts: 2198




Ignore
« Reply #5 on: November 30, 2004, 07:46:06 PM »

That's not correct! USB serial port adaptors include virtual com port drivers, and thus appear like a native serial port to Windows, applications, and external hardware. I use such adaptors from MicroHam, Belkin, VSComm with a wide range of amateur radio software, as do many other hams.

73,

Dave, AA6YQ  

==================================

    Some, but not ALL adaptors will work, depending upon how well the adaptor and drivers are designed.

    But more importantly, now we're talking about not just adding a USB port, but ALSO a USB-to-RS232 adaptor.  The solution is getting more expensive, and requires Windoze 98 (at least) to support USB.  (That may not even be an option with an older computer; it would also require an empty PCI slot for the USB Port.)
Logged
AA6YQ
Member

Posts: 1807


WWW

Ignore
« Reply #6 on: November 30, 2004, 08:16:35 PM »

WA9SVD: my original suggestion was "add either a PCI card or a USB adaptor".

If KF9SQ's PC doesn't support USB, then obviously adding a PCI serial port would be the less expensive solution.

Most PCs built in the past 5 years support USB; the Windows 9X family is plagued by serious defects and and is long obsolete. Adding a single USB serial port adaptor to a PC that supports USB costs ~$29, which is not very expensive compared to a manual A/B RS232 switch.

    73,

        Dave, AA6YQ
Logged
WA9SVD
Member

Posts: 2198




Ignore
« Reply #7 on: December 01, 2004, 08:49:55 PM »

If KF9SQ's PC doesn't support USB, then obviously adding a PCI serial port would be the less expensive solution.

Most PCs built in the past 5 years support USB; the Windows 9X family is plagued by serious defects and and is long obsolete. Adding a single USB serial port adaptor to a PC that supports USB costs ~$29, which is not very expensive compared to a manual A/B RS232 switch.

73,

Dave, AA6YQ

=========================

Dave,
    I don't mean to argue, and much of what you say is true.  But USB isn't always "bug-free" when adapted to RS-232, and the purported "USB" support built into some later OEM versions of Windoze 95 was useless, as you say.  Win 98, however, had (has) a credible implementation of USB, and is still in use by many people, whether or not Microsoft says it's obsolete.  (Especially hams; you KNOW how eager they are to go out and spend money... <GRIN>  I have XP Home and Pro, but I also use an XT laptop for packet, running DOS 3.3.  Hoeplessly obsolete?  Perhaps, but it gets the job done!)

    Again, it seems the original post was looking for an inexpensive way to switch, and at least here in So. California, we can buy a manual A/B switch (either 9 or 25 pin) for $5 to $10, which is much less expensive than a PCI card and an adaptor.

73,

Larry WA9SVD
Logged
AA6YQ
Member

Posts: 1807


WWW

Ignore
« Reply #8 on: December 01, 2004, 09:45:07 PM »

WA9SVD:

re "at least here in So. California, we can buy a manual A/B switch (either 9 or 25 pin) for $5 to $10, which is much less expensive than a PCI card and an adaptor."

1. under no circumstances would KF9SQ need to purchase both a PCI card and an adaptor. If his PC doesn't already have a USB port, then he purchases an RS232 PCI card; if his PC has a USB port, then he purchases an USB-to-RS232 adaptor.

2. my original post said

"its probably not much more expensive to add a second serial port to your PC, either a PCI card or a USB adaptor"

At least here in eastern Massachusetts, we can buy a used serial PCI card for ~$10. And as I said before, new USB-to-RS232 adaptors are closer to $30 -- more expensive than a manual A/B switch, but also more functional.

Its true that there are poorly-designed USB adaptors around. There are also poorly-designed motherboards, coffee grinders and automobile engines. Yet we don't all count on our fingers, smash beans with rocks, or walk -- we choose good designs over bad ones. I recommended several good quality USB adaptors in my earlier post.

   73,

        Dave, AA6YQ
Logged
CLEBOT
Member

Posts: 100




Ignore
« Reply #9 on: December 09, 2004, 08:27:35 AM »

I had the same problem...Trying to use 1 nine pin serial port to run a Davis weather station, scanner and receiver.  I have been using a 4 poistion DB9 switch for over a year and it has worked perfectly.
I found mine at www.cablesonline.com.  If I mis-spelled that you can try Google and look for it under cables online or cablesonline.
Good luck.
Logged
CLEBOT
Member

Posts: 100




Ignore
« Reply #10 on: December 09, 2004, 08:32:22 AM »

Oops!
Forgot to mention...the switch I got was relatively inexpensive (I think it was about 15 bucks or so.)
Didn't know if price was a factor; it was for me.
Hope this helps some.
Logged
N4ZOU
Member

Posts: 340




Ignore
« Reply #11 on: December 18, 2004, 02:49:13 PM »

Check your local thrift store for the RS-232 switch boxes. Normal price for them is $1. Not only have I used them for what it was made for but also make very nice project boxes! My sound card interface is inside one and the switch is still in it and used for selecting the PK-232MBX when I want to use Packet, Amtor, and Pactor. I normally buy every one of them I can get my hands on for projects.
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!