FT8 – Tipping Point for Ham Radio? • Hacker News Board

Re: FT8 – Tipping Point for Ham Radio?

#111

Post by ac29 » Sat, Oct 20, 2018, 5:44 PM UTC

hatsunearu wrote: post #105

I think the FCC should remove the 300 baud limit for HF which is super arbitrary and limiting for real digital modes. That limit makes modes that are quite distant from modern day commercial digital modulations viable--FT8, JT65, and so on being examples. They are primarily asynchronous MFSK detectors with tons of symbols--pretty weird design and a work around of the 300 baud limit. We can't get cool stuff like QAM,…

Curious, what about the symbol rate limit limits you from using, say 8PSK or 16QAM? Is it that it also effectively limits channel bandwidth to something that isn't practical to transmit and/or receive with higher order modulation?

Re: FT8 – Tipping Point for Ham Radio?

#112

Post by crankylinuxuser » Sat, Oct 20, 2018, 6:45 PM UTC

bitcoinmoney wrote: post #99

crankylinuxuser wrote: post #45

Earlier quoted context omitted.

I'm not parent/GP... I bought a ADALM-PLUTO from Arrow. $98 shipped. It's a SDR that goes from 325MHz-3.8GHz, and with a "hack" will go from 70 MHz to 6GHz. 7dBm (or 5 mW Tx). You'll need amplifiers to go from 5mW to QRP (~1W). I did find one on Banggood for 1MHz-1GHz with up to 35dBm gain. I'll still need one for 2.4GHz and 5.8GHz, but that's a small price to pay for having nearly 6GHz of spectrum to read. ( https:/…

I also have an amateur license. How much is the cost to go to non voice band for starters??

I'm not entirely sure I can competently answer that.

I know with my ADALM-PLUTO hardware, it can receive from 70MHz to 6GHz, but at only 5mW. So if you want to start Tx-ing, you'll need a low noise amplifier for the band you want to transmit. Also, the antennas are for 325MHz-3.8GHz and are anemic stubby 1dBi. You will want better antennas. Ideally, for the respective bands you want to do stuff with.

I'm still piecing my software together. Right now in open-source land, there's lots of individual decoders and some encoders. I'm having good luck with SDRangel for handling Tx as well - there's some weirdness with encoding data for Tx with the plugins. But that's just growing pains of this being new.

The other problem you'll have, if you just don't pony up kilobucks for "ham radio hardware", is that going from 7dBm (5mW) to 30dBm (1w) is going to be weirdly expensive. And then that only gets you to 'QRP'. You'll then need a second stage amp to go from 1w to higher power.

If you do EME digital modes, you're amping up from 5mW to 1.5KW . $$$$$$$$ lies here. But I'm sure if you talk in freenode IRC in ##hamradio , there are EME hams there.

So to better answer your question, rather than give you a bunch of options, here's a general idea of cost breakdown:

Cost = laptop + ADALM-PLUTO (or relevant SDR for HF) + 30 dBi amplifier for band you want + antennas for band you want

My laptop is $500 and is Dell precision m4800. 4 cores/8 threads, 32GB ram. $500 from ebay. ADALM-PLUTO is $98 shipped from Arrow. I bought 2 1.35GHz-9.5GHz antennas for $13 each from Banggood. I'm looking for a 7dBm->20dBm 2.4GHz amplifier That would bring me up to 100mW output. I also bought a random assortment of SMA connectors for $12

That would leave my current total at $136 for the wireless hardware, or $636 if you want a dedicated laptop. RasPis won't work with SDRangel - it eats CPU for breakfast, lunch, and dinner.

https://www.banggood.com/1_35GHz-9_5GHz-UWB-Ultra-Wideband-L...

https://www.banggood.com/18pcs-1_2G-5_8G-FPV-Telemetry-Anten...

Re: FT8 – Tipping Point for Ham Radio?

#113

Post by tibbon » Sun, Oct 21, 2018, 8:49 PM UTC

geofft wrote: post #11

tibbon wrote: post #5

I've got my technicians license, and have no idea what he's talking about. Can someone explain? Even the AARL page on this that's the top google hit doesn't jargon check itself at all: http://www.arrl.org/news/ft8-mode-is-latest-bright-shiny-obj...

FT8 is a signal encoding mode. My impression is that it is much more robust and therefore also reduces the required skill, luck, etc. in making successful transmissions under unfavorable conditions. "DX" is an abbreviation for "distance", generally used in the sense of "making long-distance contacts." A "QSO" is a successful contact between stations, and "working" refers to the process of making / attempting to make…

Thank you so much!

Re: FT8 – Tipping Point for Ham Radio?

#114

Post by mediocrejoker » Mon, Oct 22, 2018, 5:55 PM UTC

GlenTheMachine wrote: post #56

mediocrejoker wrote: post #38

Earlier quoted context omitted.

What is FT8 and why is it controversial with hams?

It's a digital mode that has impressive ability to hear weak signals. Which means you can have a small, inexpensive radio, a really suboptimal antenna, and still make worldwide contacts. The basic mode only allows you to make contact, it doesn't allow for discussions or data transfer. It's simply a “I'm here, and I can hear you” mode. It's controversial because a) to some hams, conversation is the reason to be on the…

Thanks that makes it more understandable.

Re: FT8 – Tipping Point for Ham Radio?

#115

Post by hatsunearu » Sun, Oct 28, 2018, 11:20 AM UTC

ac29 wrote: post #111

hatsunearu wrote: post #105

I think the FCC should remove the 300 baud limit for HF which is super arbitrary and limiting for real digital modes. That limit makes modes that are quite distant from modern day commercial digital modulations viable--FT8, JT65, and so on being examples. They are primarily asynchronous MFSK detectors with tons of symbols--pretty weird design and a work around of the 300 baud limit. We can't get cool stuff like QAM,…

Curious, what about the symbol rate limit limits you from using, say 8PSK or 16QAM? Is it that it also effectively limits channel bandwidth to something that isn't practical to transmit and/or receive with higher order modulation?

Super late but good question. I should ask some seasoned hams about this. I'm curious as well.