SignaLink mods

[Mel Whitten]

Peter, OZ1PIF has made mods to the Signalink interface.  These were highlighted in August 2014 QST, pg 61.  The mods are detailed on his web side found here:

 

http://www.frenning.dk/OZ1PIF_HOMEPAGE/SignaLinkUSB-mods.html

 

Anyone using the SignaLink for FreeDV may want to consider making these mods.

 

Mel, K0PFX

 

[Steve]

It looks like an opportunity for someone to develop a product that actually interfaces software to radio.

After experiencing the problems myself, with products of the past (I never upgraded - is that the word - to a USB interface) I always felt the soundcard was crippled, by not having a PTT and impedance matching circuit for the radio modulators.

David has the best idea, simply replace the soundcard and the signal interface, with a small PC board.

While he also moves the software from the PC to the same board, there is a case for maybe just making a data interface for the adapter. For example, programmers could just send UDP packets to the device and it would operate the A/D, D/A, and PTT.

So, a nifty add-on to the SM1000 would be a way for programmers to send and receive digital audio data via UDP, and not have to use the soundcard. Admittedly, this would probably be only useful for "data" modes, but I suspect a headphone could be interfaced as well, if someone didn't want to use FDM.

[David Rowe]

Hello Steve,

Actually my unit test programs make the SM1000 act as a "sound card", I
can play and receive files from the Host PC. This is done via a stdio
and gdb, using a "semi hosting" approach.

However I believe it it is possible to make the SM1000 appear as a USB
sound device.

Cheers,

David

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[Steve]

That would be one way. I was thinking putting sound bytes over IP would be more generic.  That way, all the different OS could deal with the USB in their own special way, and the ARM having some IP interfaces could just ride on top of that.  Maybe a UDP port for PTT, a UDP port for sound bytes, and a UDP port for interface switches and indicators.

[Matthew Pitts]

I haven't taken the time to do them to mine, nut everyone that know of that has done them liked the improvements; interestingly enough, Tigertronics claims they are not needed even with the evidence provided on OZ1PIF's site saying otherwise.

Matthew Pitts
N8OHU

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Sent from my Android device with K-9 Mail. Please excuse my brevity.

[Steve]

His biggest claim is switching the original 600/600 transformers with a different type 600/600 transformer.

Looking at the data sheets of the one he likes versus the installed, shows his to be better in frequency response.

The original shows 300-3.4 kHz +/- 3.0 dB and the one he installed has 200-4000 kHz +/- 0.5 dB and about 10 ohms more resistance per winding. The transformer he likes, being used in 56k modems, which need a flat frequency response. The original seem to be designed for microphones maybe, to attenuate the lows..

[Steve]

P.S. I looked at the transformers Richard selected for the SM1000 and they are: 200-4000 +/- 0.25 dB and have 115 ohm resistance.

good stuff !

[jdow]

For ICOM CiV control thank the Arduino for an easy solution. Little USB adapters
that are designed to plug onto an Arduino have turned up. They feature TTL
levels. One Schottky diode later and I have the CiV interface. I use the DTR pin
as is for T/R control. It's a nice hack. The R pin goes to the CiV line. The
diode connects the T pin to the R pin such that if the T pin goes low it pulls
down the R pin. And you have several spare pins you can use, too.

{^_-} Joanne/W6MKU

[jdow]

For sound interfaces USB can still come to the rescue. There are cheap little
USB sound cards. They have plenty adequate audio for the needs of digital modes
working off the audio from your rig. If you get different types you can even
have these audio cards all hooked up unambiguously as long as they have
different names. (The "USB Audio" name is basically useless. And MS does not
provide any further ID to the interfaces when trying to choose one from software.)

The only additional thing to the really cheap hookups that the formal ham that
interface boxes give you is some EMI filtering. If you have even a modest junk
box and a few ferrite beads you can knock that off easily enough.

{^_^} Joanne/W6MKU

On 2014-08-05 11:27, Steve wrote:

[David Rowe]

Hi Steve,

The original +/-3 dB could be an issue for FreeDV, for example if one
carrier was 3 (or even 6) dB higher than another it could lead to a
very high BER.

- David

[Steve]

It looks like the signallink started out as a PSK31 design, and then someone in the garage said "hey it seems to work with XXX too".

The op-amps being biased by a voltage divider is something I would have done in the 90's :-)

Although the op-amp in that device has a faster slew-rate than the SM1000 (4 volts per us versus 1 volt per us).  The 1 volt actually seems pretty slow, but what do I know, as one has 5 volt rails, and the SM1000 only 3 volt (regulated!)...

Film at 11...

[Reuven Z Gevaryahu]

I'm surprised that Tigertronics hasn't come out with an updated version of it, given the interest in these mods, and that it costs little to make the changes. JT65 and other near-noise-level modes are pretty common these days.

The newer laptop that I have only has a single switchable Microphone/Headphone jack- Meaning that my homebrew interface that I've used the past 12 years (with a USB/Serial cable for the past few) might be reaching the end of the road. A signalink would be one way I could go, though the noise floor issues discussed make me unsure.

--Reuven (KB3EHW)

[Mel Whitten]

Yes.. a "Plus" model (SignaLink Plus) with the updates it could be priced a few dollars while still remaining competive.

 

Mel, K0PFX

 

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[Rudy Benner]

I have 2 Signalinks. Someone could make a little money by offering a service to upgrade these.

 

My soldering skills have diminished with my age.

 

Any takers?

 

Rudy