However, I was not aware that AFSK could provide a better and
narrower signal than FSK.
Only if you are scrupulous in keeping the drive level to the rig
below the distortion/saturation point, keep RF off the audio cable
*and* make sure the "ground" (audio return) is not broken.
In addition, it is crucial that Windows be configured so that it
will not send any of its own noises, streaming audio, DX Alerts,
etc. to the sound card/audio port being used for AFSK.
I am bound and determined to get FSK working and plan to try a
switching transistor as you suggest.
Many newer serial ports are 3.3V logic instead of 5V or even 10V
as in the old days. With a lower voltage, the base (current limiting)
resistor in both opto-isolator and switching transistor interfaces
need to be much lower than shown in older designs. Measure the
voltage on the FSK (TxD?) line from your serial port and choose
a resistor that allows enough current to saturate the LED in the
opto-isolator and/or create +1V on the base of a switching transistor.
Note: with MMTTY and a USB to serial adapter, you will probably need
to use the EXTFSK driver as, except in limited cases, most USB to
serial adapters no longer support data rates below 300 bps.
73,
... Joe, W4TV
On 2/23/2018 5:18 PM, groupsrichart@gmail.com wrote:
Hi David,
Thanks for the input. I am bound and determined to get FSK working and
plan to try a switching transistor as you suggest. However, I was not
aware that AFSK could provide a better and narrower signal than FSK. I
will have to learn a bit about that and consider switching! My previous
forays into RTTY were in the '70s when AFSK was shunned by most
operators. I imagine improvements in producing clean audio signals has
changed that.
73,
Tim WS4V
On 2/23/2018 3:47 PM, David G3YYD wrote:
Tim
Use a switching transistor as per N1MM wiki on interfaces see
http://n1mm.hamdocs.com/tiki-index.php?page=Serial+Parallel+and+Sound+Card+Interfacing&highlight=interface+cw#Interfacing_for_PTT_and_CW_Keying
Opto-Isolators are not needed.
Even better would be to use AFSK as that will have narrower
transmission width than rig based FSK. It will also be jitter free
unlike MMTTY FSK making copy at the far end better. If you use MMTTY
AFSK then configure it for the TX filter on with tap set at 51, the
default setting for this is not very good.
73 David G3YYD
-----Original Message-----
From: RTTY [mailto:rtty-bounces@contesting.com] On Behalf Of
groupsrichart@gmail.com
Sent: 23 February 2018 19:49
To: KenwoodTS-590@yahoogroups.com; rtty@contesting.com;
TS-590@groups.io; TS-590S@yahoogroups.com
Subject: [RTTY] FSK Keying of TS-590SG
I would like to hear from anyone who is successfully keying the FSK
and PTT lines via the ACC2 connector on the rear panel of the
TS-590SG. What serial adapter and what hardware interface are you
using to do so?
I have tried two different interfaces using optoisolators to attempt
FSK and PTT keying from a serial card to the rear panel ACC2
connector. Both attempts have failed. I am using MMTTY software for
keying and I do get the requisite signal change on TXD pin 3 (FSK) and
RTS pin 7 (PTT) lines. I have also verified proper setup of the '590
by manually grounding the inputs PKS pin 9 (PTT) and RTTY pin 2 (FSK)
on the ACC2 connector.
However, I *think* the problem lies with the serial card not providing
enough voltage/current for the optoisolators to completely turn on and
provide a hard ground to the ACC2 inputs. I have tried two different
serial cards and one swings from -4.9 to +5.0 VDC on the data lines
and the other card swings from -3.8 to +3.9 VDC. The cards I am using
are a two port generic PCI Express SI-PEX15037 and a four port Perle
Fast 4 PCI card. Does anyone know of a serial card that has a full -12
to +12 VDC swing?
One of the hardware interfaces has 4N25 optoisolators and the other
uses Fairchild FOD852 optoisolators. There are 1K series resistors in
the input line to the optoisolators and I have tried various values (100,
220 & 470Ω) with limited success but nothing consistent.
While my objective was to keep the rig isolated from the computer, I
am thinking about building an interface that uses NPN transistors for
keying. Is anyone using NPN transistors to key their '590? Are you
tying the ground from pin 5 of the RS-232 port to the pin 4, 8 or 12
ground of the ACC2?
Any input is appreciated...I have been off RTTY since purchasing this
rig in November and I want to get back on the bands.
Thanks,
Tim WS4V
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