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Author Topic: Recommend best "null modem" cable for CAT?  (Read 3356 times)
KG4RUL
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« Reply #15 on: November 03, 2017, 01:12:25 PM »

I have a similar setup with an inverted 'L' antenna 25' up and broadside to my station.  Running 100W with my Kenwood TS2000 (it also is RS232 using a straight-through cable for the CAT interface), I have never had any problems with RFI on the CAT cable. 
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KE2KB
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« Reply #16 on: November 03, 2017, 03:16:07 PM »

I am going to make my own cable. I purchased a lot of 50 9-pin D female connectors on Ebay for under $8 - they are described as new - in mfr pkg, but for that price I'm afraid they'll be unusable due to oxidation. So I also ordered some 9 pin D both female and male by Amphenol from Mouser.
I also bought the metal hoods from Mouser. I just want to cover all bases. I will be using the shielded Cat6 cable - also from Ebay - mainly for its tight twisted pairs, but I figure that shield may be needed for some projects.

I'm not sure what to make of that information on pin connections in the FT-450D manual, but I figure I'll just wire my cable straight through. Since the Cat6 cable is 8 wires plus shield/drain, I can wire all pins of the 9-pin D if I want, but I doubt that is necessary.

Now I'm looking for a good ferrite mix for HF RFI mitigation. Not sure where I may need it, but I would like to have some around.
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K0UA
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« Reply #17 on: November 03, 2017, 05:04:58 PM »

When I had the FT450at, and I used a premade CAT cable.  some $5 cheapie, and I don't remember where I got it. I never had any problem with RFI getting in to it.   You will need CAT for digital modes if you want optimum operation, especially on the fast modes like FT8,  you can kludge and get away without it on some of the modes, but it sucks.  One way you can operate your station remotely for no cost it to load teamviewer 12 on your station PC, then connect to your pc from any other PC or even from a phone as the teamviewer app is available for android I know, and maybe apple, but I am not sure.  it might be a "bit" busy on a phone though, maybe a good tablet.  I have done it from a laptop, and it works very well.  You don't need to worry about the audio, as you don't need it.  Of course you could run skype too I guess.
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AA4PB
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« Reply #18 on: November 03, 2017, 05:11:04 PM »

Like I said before, twisted pairs do no good unless the inputs and outputs are balanced. If you use one wire of the pair for Txd and the other for Rxd and use a common ground for both then there will be no benefit to the use of twisted pairs. There could even be a disadvantage as the Txd and Rxd signals may couple to each other via the capacitance of the tightly twisted pairs (depending on how long the run is). You'd probably be better off NOT putting Txd and Rxd on the same pair.

Twisted pairs only work when the signal in each is exactly the same but with the opposite polarity. Outside signals couple into the two wires of the pair equally and get cancelled out at the input.

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Bob  AA4PB
Garrisonville, VA
KE2KB
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« Reply #19 on: November 03, 2017, 05:23:19 PM »

Like I said before, twisted pairs do no good unless the inputs and outputs are balanced. If you use one wire of the pair for Txd and the other for Rxd and use a common ground for both then there will be no benefit to the use of twisted pairs. There could even be a disadvantage as the Txd and Rxd signals may couple to each other via the capacitance of the tightly twisted pairs (depending on how long the run is). You'd probably be better off NOT putting Txd and Rxd on the same pair.

Twisted pairs only work when the signal in each is exactly the same but with the opposite polarity. Outside signals couple into the two wires of the pair equally and get cancelled out at the input.


So I guess it's pretty much pot luck then.
I'll have to play around with it.
Does anyone know which RS232 lines are actually in use for CAT?
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NA4IT
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« Reply #20 on: November 04, 2017, 03:53:09 AM »

For connecting the CAT jack to the PC:
What is meant by this?



To me, it says connect pins 1,4, & 6 together.

Correct...

Really, all you need to do is this...



If you do hook up the extra grounds, I would bridge them together to stop any "ground loops".
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KE2KB
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« Reply #21 on: November 04, 2017, 08:04:03 AM »

Thanks for your excellent diagram.
I guess the purpose of connecting pins 1 [DCD], 6 [DSR], & 4 [DTR] together is that they are unused, and doing so may prevent RFI issues?
In any case, when I build my cable, I'll start with the simplest and go from there.
« Last Edit: November 04, 2017, 08:20:33 AM by KE2KB » Logged
WA2ISE
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« Reply #22 on: November 15, 2017, 01:08:21 PM »

I ordered 250ft of shielded Cat6e cable on Ebay. Whether or not I use this cable for my CAT cable remains to be seen. But the fact that this cable is twpr and has a shield, it should work.

You'll need to get special RJ45 connectors that have the shield, for the cat5 shield to mean anything. 
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NA4IT
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« Reply #23 on: November 16, 2017, 03:43:49 AM »

Quote
You'll need to get special RJ45 connectors that have the shield, for the cat5 shield to mean anything.

The cat connector on a Yaesu FT-450D and the computer is DB9. He's just using the CAT6e cable to make up a serial cable.
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KE2KB
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« Reply #24 on: November 16, 2017, 09:35:04 AM »

I have the USB to 9-pin cable connected and working. Haven't tried it while transmitting yet though. The cable has no ferrites, but I believe it is "shielded". I will try it out and make changes as necessary.
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WA2ISE
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« Reply #25 on: November 16, 2017, 01:51:50 PM »

If the serial cable has just two signals and a ground, you could use decent small diameter coax for both signals (RG58 would do, one coax per signal).  And of course the shields are ground. 
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