开云体育

On Jun 18, 2024, at 10:21, Jeff via groups.io <jcowall@...> wrote:

?On Mon, Jun 17, 2024 at 12:20 PM, KA9CAR John wrote:

9600 packet it won't work due to Gaussian errors

Classic packet radio uses direct FSK modulation. The technology available at the time to the average ham, both in computer software or TNC hardware was quite limited, there were virtually no noise mitigation stategies available besides AF filtering. ,the%20radios%20and/or%20modems.

I've been working with my local RACES team to set up a prototype county Winlink net. A couple of use have both shack and mobile Winlink stations to research locations and digipeaters. We've played a lot with winlink recently, on a number of different rigs. Here's some of my discoveries after 30+ years of packet (Icom 28 mobile and TRS-80 laptop with a TAPR TNC-2 kit)...

In the last 40 years, the explosive demand for high-speed serial data over media like cable television, fiber, and even twisted pair led to rapid development of modulation methods that would combat gaussian noise by exploiting its randomness. This is still going on. Given Moore's Law (), there's been an exponential growth in signal processing power available to hobbists, driven by the commercial exploitation of this processing power. Modulation methods developed for cable television, cell phones, satellite communication and wi-fi are now well within the processing power of even a modest personal computer.

Quadrature Amplitutude Modulation has become the workhorse modulation method of the current digital world. (). Digital QAM is even more interesting because it implements a serious amount of parralellism to the data stream (,than%20just%20phase.)

The VARA wide modem status display looks a lot like a Digital QAM Constellation:
(). I think it's at least based on Digital QAM concepts. I think of it as 64 ft8 QSOs in parallel without trying so hard to dig down into the noise.

Given that, Amateur FM radios have long used simple analog deemphasis to increase the perceived signal to noise ratio for human voice frequencies. The "9600 baud" ports on rigs simply bypass that filtering. This deemphasis is only on FM mode on RX. Some rigs without the tradtional 6-pin connector have the deemphasis selection in a menu.

If an amateur FM rig does not have a "data" port on it, it almost certainly applies the deemphasis in the output audio chain, and would have trouble with 9600 and up.

I've used an ICOM IC-208H (25 years old), a Yaesu FT-817nd, Yaesu FT-897D (both 20 years+), and a Yaesu FTM-6000R (current) on VARA WIDE with great success on a 14-year old Windows 10 box, and on a new Win 11 laptop. I've seen above 10k baud on all of them on VARA wide to my closest RMS (Thanks, Steve)

BTW, the FTM-6000R has a new, perhaps proprietary, 11-pin DIN on the back. Works great, more expensive, and one wonders why other than profit. I eagerly await a commercial rig in the 5-10 watt range with a PD USB-C connector with all charging, Internal sound card, data, and CAT ports for a couple of hundred dollars.

Hope this helps.
73,
Jeff kn8a