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Re: ICOM 821H and PSK-1...


There's an error in the PSK-1 manual regarding the pinout for one of the
up/down pins mixed with something else.

It's documented on

Maybe that's your problem.

73 Howard G6LVB

----- Original Message -----
From: "Ronald Long" <rlong3@columbus.rr.com>
To: "Chris Souris" <csouris@cescomputers.net>
Cc: <amsat-bb@AMSAT.Org>
Sent: Saturday, November 25, 2000 8:53 PM
Subject: Re: [amsat-bb] ICOM 821H and PSK-1...

> At 08:03 PM 11/21/2000 -0500, Chris Souris wrote:
> >I've tried to get the AFC working correctly with the PSK -1 and
> >the ICOM 821H to track AO-40 correctly, but to no avail. It will
> >auto-correct downward when turning the VFO to increase the freq, but when
> >turning the VFO to decrease the freq, the "up" LED on the PSK-1 flickers
> >ok, but the freq still goes downward even after I've stopped turning the
> >VFO, even with the "up" LED flickering.
> Here is my experience with the G3RUH modem click tuning. Perhaps some of
> the information will apply to your PSK-1 problems.
> ron w8gus
> =====================================
> The following may help in understanding the problems associated with click
> tuning. It applies specifically to the G3RUH 400psk modem. The PSK-1
> is probably similar in some respects.
> The G3RUH modem has a 10 segment barLED which is essentially an audio
> frequency meter. I measured the following using an audio generator
> and counter.
>      <---- lower rf(usb)     higher rf(usb) ---->
>    1    2    3    4    5    6    7    8    9   10   bar# left to right
> 1620 1615 1610 1605 1595 1585 1575 1565 1555 1550  Hz
>                   ^      ^       ^
>                   |      |       |
>                  UP     CTR     DOWN
> The G3RUH modem works as follows. The correct tuning is when the
> center bar is lit, actually 5 or 6 straddles the center. When the
> received radio frequency drifts lower, assuming that the radio is set for
> USB reception, the audio frequency becomes higher. When the #4 bar lights
> an UP click pulse is generated which will move the radio frequecny
> higher and the display back toward the center.
> Conversely, if the frequency drifts higher, the audio frequency
> is lower. When bar#7 lights a DOWN click pulse is generated which will
> again correct the radio frequency and move the display back towards
> The #4 and #7 bars are connected to optoisolators which enable the
> to be communicated to the click pins of the radio microphone input.
> Now comes the problems. We have three radio brands, Kenwood, Icom and
> They implement mic click tuning in different ways. Also the click step
> varies with mode and model. You can see from the chart that the whole
> of the barLED is about +/- 35Hz. A step size of 10Hz is ideal. Although I
> have not tried it, I think a step size of 50 or 100Hz may not work.
> Here is some data I have gathered over the years. I would appreciate being
> informed if there are any inaccuracies or additions. Since most radios
> display to 100Hz, it takes, with the FT-736, 10 clicks to change the last
> frequency digit. Of course if you happen to be part way into the range you
> may get some other number, like 6, the first time. Just keep clicking
> you observe a full range, which will be 10.
> FT-736        10Hz
> IC-275/475    10Hz  (data switch must be on)
> IC-970        10Hz
> FT-726        20Hz
> TS-790        20Hz
> IC-821        50Hz
> IC-820       100Hz
> IC-271/471   100Hz
> TS-711/811     ??
> FT-847         ??
> IC-910H        ??
> TS-2000        ??
> On the Yaesu FT-736 the UP and DOWN pins are at +5Volts. Pressing
> UP or DOWN connects the pin to COMMON. I have used my modem with
> the FT-736 with complete success.
> The TS-790 UP and DOWN pins connect to Ground when pressed. This
> should not cause any problems. There are jumpers in the G3RUH modem
> to set up for Kenwood or Yaesu.
> Icom uses a different system, and I have not been able to make it
> work with my G3RUH modem. A single pin on the mic connects to the UP
> switch, and also to the DOWN switch through a 470 ohm resistor. The
> open circuit voltage of this pin is 5Volts. Both switches connect to
> Ground. The result is that a direct connection of UP to Ground i.e.
> 0Volts generates an UP command. When DOWN is pressed the voltage is
> 0.6Volts across the 470 ohm resistor. All Icom radios use this system
> but there are variations. A different resistor value may be used. I
> have seen 1.4Volts for DOWN.
> In spite of setting the correct jumpers in the G3RUH modem and adding
> the 470 ohm resistor, I have not been able to get the Icom system to work
> with my IC-275. Let's just say I tried it and gave up. Maybe more work
> would have solved the problem. I speculated that perhaps the opto-isolator
> transistors were not being saturated; or that the 0.2 volts at saturation
> would not permit the 0 or 0.6 volts that the system requires to be
> achieved. Perhaps adding external DIP relays driven by the opto-isolators
> would work. Another possible problem is the pulse length.
> Finally what about radios with a larger step size. You might alter the
> circuit in the G3RUH modem so that different bars are used to generate
> the click, for example 3 and 8, but you don't want the frequency to
> change so much that lock is lost. The manual says that lock will occur
> for 1584Hz, plus or minus 80Hz. So perhaps range is not a problem.
> If the radio has a large step size, but also has a PC serial port, you
> might connect the modem clicks to a microprocessor and generate
> frequency changes through the serial port.
> Good luck. I hope this has been informative.
> ----
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