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2400 vers A or B?

 

I would like to add a 2nd port (on 440Mhz) at a local mtn. top node--
As I have users that use UZ7HO I would like to be compatible for them.
I see there are (2) 2400 modes--A and B in UZ7HO. From the Direwolf
side of things, which would be better?(line of sight links)
Has anyone tested in real world links?
And what about the 3600 bit modem?
Thoughts?
Oh --also-- the radios I am using DO NOT have the 9600 HS ports
so any mode would need to go thru the MIC connector.
(old public safety radios)

Tnx de Trip - KT4WO
 

On Sun, Mar 7, 2021 at 08:48 AM, kt67 wrote:
And what about the 3600 bit modem?
That should have been 4800 bit modem.
 


And what about the 3600 bit modem?
3600 may be a good option sometimes when the radio won't work at 4800.? Research needs to be done.
 

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Hello Trip,

Per the 2400-4800-PSK-for-APRS-Packet-Radio.pdf document, the "B" modem is the one you should use.? Neither version of this modem is superior as it's just a difference in starting "phase".? Read the PDF for details. ? Btw, you can run this "2400" modem all they way up to 3600bps using a standard MIC connector and it should work.? Warning: I did test this but not using real radios.. I was just testing two sound cards connected back to back.

As for the 4800 modem, you WILL need a connection to the radio's discriminator (aka the 9600 pin) for this wider mode.

--David
KI6ZHD






On 03/07/2021 08:48 AM, kt67 wrote:

I would like to add a 2nd port (on 440Mhz) at a local mtn. top node--
As I have users that use UZ7HO I would like to be compatible for them.
I see there are (2) 2400 modes--A and B in UZ7HO. From the Direwolf
side of things, which would be better?(line of sight links)
Has anyone tested in real world links?
And what about the 3600 bit modem?
Thoughts?
Oh --also-- the radios I am using DO NOT have the 9600 HS ports
so any mode would need to go thru the MIC connector.
(old public safety radios)

Tnx de Trip - KT4WO

 

Tnx for the reply's.? I will do some testing and post results.
Trip - KT4WO
 

Just some FYI on real world testing of 2400b.

Over the last few weeks my mtn top node has been on
2400 V26B and the results have been nothing short
of GREAT!? Users(3) are using UZ7HO in "DW QPSK V26B 2400" mode
and it's working at least as well as AFSK1200. This is on NON-line
of sight paths(4 to 8 miles) where multipath can be a real issue.
Other than to be compatible with old equipment I can see no
reason to use 1200b any longer.

Trip - KT4WO?
 

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Hello Trip,

Great to hear about your success!? Curious, what sound device and radios are you using here?? By any chance, did you try the 4800bps 8PSK modems as well?

--David
KI6ZHD


On 03/30/2021 07:02 AM, kt67 wrote:

Just some FYI on real world testing of 2400b.

Over the last few weeks my mtn top node has been on
2400 V26B and the results have been nothing short
of GREAT!? Users(3) are using UZ7HO in "DW QPSK V26B 2400" mode
and it's working at least as well as AFSK1200. This is on NON-line
of sight paths(4 to 8 miles) where multipath can be a real issue.
Other than to be compatible with old equipment I can see no
reason to use 1200b any longer.

Trip - KT4WO?

 
Edited

Back in the 1990s there were at least three commercial TNCs that implemented 2400 bits per second.

  • ? which is an optional board for the MFJ-1270 or MFJ-1274.
  • ? .
  • ? .

They all used the XR-2123 modem chip.? Now it is done with software.

The "B" version is known to be compatible with the MFJ-2400.
 

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Thanks for clarifying this; I was just about to ask.?

I've got one of the MFJ units, MFJ-1278T with the 2400 bps modem.? Never used it in that mode, and am wondering if there are any "watering hole" frequencies where the "B" standard might be in use?

Greg? KO6TH


WB2OSZ wrote:

Back in the 1990s there were at least three commercial TNCs that implemented 2400 bits per second.

  • ·????????? which is an optional board for the MFJ-1270 or MFJ-1274.
  • ? .
  • ? .

They all used the XR-2123 modem chip.? Now it is done with software.

The "B" version is known to be compatible with the MFJ-2400.

 

"Curious, what sound device and radios are you using here?? By any chance, did you try the 4800bps 8PSK modems as well?"

A mix of the RL-20--- ?
Signalinks and a homebrew interface via RS-232 PTT.

4800b---? Yes, but no luck going through the MIC port.

I just glad to get 2400bps working so well!!
When I find time to "mod" a few radios for higher speed I will test and post results.
Tnx for the GREAT software!!

Trip - KT4WO

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