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  1. FT-857
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problem with pkt mode in 9600 baud

 

Hi everyone in the group.

I have a problem with my 857d rig.
I have? one isolated interface. The rig works ok in DIG modes and in PKT modes with menu 73 ( pkt rate )? set to 1200 mode.

But if i change the menu 71 to 9600, the rig don't output any modulation, only carrier outputs. I try a test tone in the computer and with a one handy in the same frequency in FM. and I don't have tone, only carrier.

I try to put the volume of the pc to the max. and the? menu pkt 072 ( 9600 tx gain ) at max ( 100 ). and i can hear the tone in the handy , putting the volume at max. , but at very very low level.
If I set the menu again at 1200 bauds, I can hear the tone at normal level.


I try in packet ax25 to stablish link in 1k2 , and it works without problem. I try to link at 9k6 ( commuting the audio rx output between 1k2 to 9k6 out pins off the rig, and the computer receive the packets, try to answer , but don't works.

What kind of problem I can have?


thanks & 73s
 

¿ªÔÆÌåÓý


Hello Miguel,

I have? one isolated interface. The rig works ok in DIG modes and in PKT modes with menu 73 ( pkt rate )? set to 1200 mode.


Ok... got it but a question for you.. when you say "isolated" interface.. is it something like an EasyDigi or Signalink?? If so, you're going to have deep problems trying 9600bps packet as most solutions use transformers that don't offer a wide enough signal on.


But if i change the menu 71 to 9600, the rig don't output any modulation, only carrier outputs. I try a test tone in the computer and with a one handy in the same frequency in FM. and I don't have tone, only carrier.


Two things here:? Once you change your radio to be "9600", you do realize it's now listening on the OTHER input pin on the 6pin DATA connector right??? This means you WILL need a different data cable going to your TNC, soundcard, etc.? Also note that unlike simple audio or Audio Frequency Shift Keying (AFSK) approach used in 1200bps packet, 9600bps uses audio to then trigger the radio to send the bits in a Frequency Shift Keying (FSK) approach.? FSK will sound like tightly packet hiss to a regular human ear:

?? #Listen to the very bottom one
??


I try in packet ax25 to stablish link in 1k2 , and it works without problem. I try to link at 9k6 ( commuting the audio rx output between 1k2 to 9k6 out pins off the rig, and the computer receive the packets, try to answer , but don't works.

What kind of problem I can have?


I think there be four issues:

?? - you're using the wrong pin on the 6pin DATA connector

?? - the isolation transformers are hurting your signal

?? - I don't think the FT857's "9600bps" support is sufficient (most radio's 9600bps support isn't btw).? Negative reports:
????? -
????? - ? (view the cached version on say google)
????? - etc

?? - G3RUH 9600bps packet requires near perfect / full quieting signals with almost zero interference to work.? This usually means the other station must be very close, running higher power, and are using directional antennas.? When it works, it's amazingly fast but it's hard to get working.? Instead, consider running something slower like 3600bps or 4800bps packet using Direwolf or UZ7HO soundmodem.? Those modes are far more tolerant of radios and paths but .. yes, they are 50% slower.

--David
KI6ZHD
 

I have one variant similar to signalink. Is a Cat/data interface Sm4xiu.?

Yes, is a possiblity that the isolation transformers, can be a source of problems. But now I jumpered it. I have made new tests, and I obtained connections ok, at speed of 7200 bauds in the UZ7HO highspeed sound modem ( with the rig in 9600 mode ). But no at 9600.?
I have good rx, but no TX.
?
Caution: the 857 rig have two rx outputs in pkt mode: One pin? for rx in 1200 and other pin rx pin 9600, in data connector. And only one pin for tx in 9600 and 1200. Yes I put a swtich for switching audio 9k6 to 1k2.
?
I suspect that the problem is that my usb sound cards (? I? am trying two models ) have a line level output sufficient for 1k2, but? with very low level of signal for 9k6. In fact one of the two have a little more high level than the other.
?
I see in the rig with mod indicator at the display, the better sound card, only comes to 1/4 of the modulation scale of the meter.?
?
Looking the cat port radio specs. I see the tx input of the rig, have a signal of 1Vpp 10k Zin. I suspect that in general the usb sound cards line level don't have this level of signal. I will measure later, with a oscilloscope the level of signals.
?
If this suspect is correct I will contruct a little preamplifer for example with operational amplifer ( non inverter amplifier with single power supply with variable gain).?
?
73's? ? ?

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