Full Duplex Satellite, It’s in the Bag – Part 1

Opening Salvo directed at amateur radio transceiver manufacturers: The lack of affordable full-duplex all-mode radios is why I have to write this. You would think the shack in a box (SIAB) market segment would have at least one or two full-duplex-capable radios. You would be wrong. Buying new? You can buy the Icom IC-9700 VHF/UHF All Mode, and that is pretty much the whole list. It’s a great radio but close to $2k USD when new, and $1500-1800 on the used market. It can be used in a portable station but the radio plus battery are on the heavy side. For a “hang it around your neck” portable station it is not a great choice. For everything else it is the modern standard for the V/U weak signal and satellite operator.

Icom IC-9700

Thankfully the world of QRP SIAB rigs provides an easy hack: Bolt two affordable Yaesu FT-817/818 radios together and you now have a dual-VFO all-mode 5-watt ground station for communicating through low-Earth-Orbit (LEO) satellites. That setup has proven to be effective on LEOs, and has put a lot of grids in the log for operators across the globe.

A few years back I was looking at QRP radios and the Icom IC-705 had just come on the market. After some extensive gear-liquidation I bought one and it is a little miracle of a radio. It comes close to being a ham radio for the iPhone generation. It is everything the FT-817ND isn’t. It is feature-rich with a big display, easy menus, well placed controls, single-USB access to a built in audio card and two virtual serial ports. I have used it for field-portable operation, in my shack, mobile, and as an all purpose travel radio. It is a modern classic in the way their IC-706-series radios were 25 years ago.

Icom IC-705

I mostly use Yaesu gear but Yaesu doesn’t make anything like the 705. I’m not sure they are philosophically capable of making anything like it. They infamously countered the release of the 705 with the FT818ND, a mild FT-817ND update (6 Watts!!). It was the most Yaesu thing ever, further cementing their commitment to zagging when all anyone wanted was a zig. They also released a direct competitor to their own FTdx10 in 2022 with the FT-710. Anyone who was hoping for a FTdx10-like successor to the FT-991A (Raises Hand) was left kicking dirt and letting out a Shatner-worthy “Yaaaaaeeeeessssuuuuuuuu!!!!” over their clenched fist.

I have to put in a strong word of support regarding the FT-817ND. On one. It is a brilliant little radio and the ham landscape would be much worse without it. I have owned one at least three times and it always punched above its weight. It is so small you can’t really grasp that it covers 160m through 70cm including general coverage shortwave, air band, and VHF utility. It’s not a museum piece.

Yaesu FT817ND

I know it isn’t a museum piece because I recently purchased another one to use as the uplink radio in my LEO setup. Firing one up again was like meeting an old friend. Those menus are simple and effective. The front and rear antenna connectors are a gift. The internal battery gets you half power, and there are now modern battery chemistry replacements delivering more voltage. The display is good enough. Yes, the VFO/MEM button sits right on top of the main dial. Same for the F/MENU button. You will QSY while using those buttons. You will forgive the radio.

Meanwhile, here in the 21st century I like my IC-705 with the big waterfall display, cushy controls, and features like built in audio recording with frequency and time stamp data. That’s what I am using for my downlink radio. The waterfall makes it a breeze to find yourself on the downlink and spin the uplink VFO to get where I need to be. (Yes, the 817 can tune while in transmit on SSB. Not on FM. The more you know…) The Twin Bandpass Tuning is easy to adjust and can fight QRM from adjacent stations. The internal preamp is not a feedpoint-mounted LNA, but it does the job. You want that stuff. The 705 is fantastic downlink radio.

First iteration of my portable satellite station

My hybrid 817/705 station is just fine until I squirrel enough funds to get a second 705. Maybe it isn’t even necessary. The next blog post will examine the growing pains and issues I encountered while building his rig, but as we head in to December 2022 I have worked out the worst of the bugs.

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