petebrunelli

I took the plunge into operating the amateur radio linear satellites a few weeks back and it has been a fantastic experience. My plan here on the blog is to share a few “blow by blow” accounts about what worked and what didn’t, what I have improved and how, and what’s next.

Phase One – Get on The Air

I’m a fan of “shack-in-a-box” radios so I already had the basic equipment necessary to operate on a linear-transponder LEO satellite. I used my Yaesu FT991A for the uplink, and my Icom IC705 on the downlink. Using the IC705 on receive made sense because the display on the IC705 is better, it has a built-in audio recorder, and it has options for things like bluetooth audio if I wanted wireless RX via earbuds, etc… I had to configure my station so I could manage two radios and point the antenna. I arranged the rigs so I could sit in front of them (I’m not hanging a 991A around my neck) and reach the tripod to point the antenna. I have a Heil Proset6 which I have used on the 991A so I had a wired solution for audio. I was not comfortable enough with the function of my internal “Profanity Suppression Module” (aka PSM) to use VOX, so I used the HEIL PTT trigger switch. This tied up my hands but I was mostly interested in tracking the satellite and finding the downlink.

The antenna I use is an Arrow II, Initially I mounted it to a photo tripod so I could have some kind of sanity while I figured things out. It helped. I was able to track the bird and didn’t have much polarization-related fading. The Arrow is two antennas sharing a common boom, so there are two feedpoints. I purchased mine with the optional duplexer which turned out to be a good thing even if I am not using it as a duplexer. It can serve as a 2M Low-Pass Filter for 2M uplink, or a 70cm high pass filer, by only using half of the duplexer.

I also have a ELK L5 LPDA that I have used often on VHF rover operations, fixed, and handheld. The Elk is a nice fit on the 991A for simplex operation because you don’t need a duplexer as long as you are working one band at a time To work full duplex I would need to split the feed with a duplexer, and I am not confident about noise rejection with both radios on a common feedpoint.

That equipment made up Phase 1: two radios, hand mic, headphones, antenna on a tripod, iPad running GoSatWatch, and the appropriate page out of KE0PBR’s Satellite Cheat Sheet on a clipboard. That is a lot to manage at one time, especially while teaching myself how an inverting linear transponder works and how to operate through it. But those are the pieces-parts and I made exactly one QSO on a RS-44 pass on October 27th 2022. That first contact was not pretty but it did let me get my feet wet. I collected my thoughts and set up for the following pass and made seven contacts! I think that is still my best QSO/Pass figure.

Once Phase 1 got rolling, I knew I needed to assemble a portable setup if I wanted to work sats on a regular basis. My home has a “crow’s nest” feature where I can walk up stairs to a small deck mounted on the roof. That’s a very good operating position and is also where I set up my portable V/U antennas for terrestrial operations. The downside is I don’t have a great horizon due to structures and trees. If I want a clear horizon I need to travel. Also, the setup/teardown for the 991A/705/camp table/tripod… is not practical. The good news is I was very close to having a portable solution. Yay.

Phase Two – Portable Ops

One very common portable satellite station is a pair of Yaesu FT-817/818 radios (aka the FT-1634) in some sort of camera bag, and a few accessories to assist the operator. In my case I already have the deluxe option of the Icom IC705, and all I needed was a second rig. FT-817NDs are not too expensive so I began looking for one. I found a clean FT-817ND on QRZ.com for about $400 and got busy with the station-assembly phase. As an avid amateur photographer and I have a small collection of camera bags. The one that I settled on is a KATA 3N1-20 backpack/sling bag. Frankly, it was horrible for photography use and it has sat around unused for over 10 years. For radio purposes it is almost ideal!

It has a large top compartment, while the main compartment has identical zippered access flaps on both sides of the bag. The symmetry of the bag means I can set it up to have full access to the rig fronts on one side, and full access to the rear on the other side, along with battery storage in the top lid. I used lots of “pluck apart” foam block to support and position the radios and built a simple fused power splitter to deliver 13.8v to both radios. The power harness is made from a factory IC705 power cable, plus some good 16ga zip-cord, and fitted it all with Anderson Powerpole connectors.

For antenna connections I use a BNC pigtail to create strain relief and improve access to the IC705 antenna connector, and am building one for the 817ND. On the audio side I raided my parts bin and found a cheapie 3.5mm extension with a right-angle on one end to extend the headphone jack. On the 817ND I have the Heil AD-1-YM adapter fitted. Those give me the two connections I need to get audio to and from my Heil Proset 6. I’m running the 817ND in VOX mode now and rarely do I have a PSM glitch 🙂

I love to build cables so I started off by making a set of 70-inch (1.7m) cables to reach from the Arrow II feedpoints to the radio. I actually staggered the lengths to compensate for the feedpoint locations so they terminate at about the same point. I used RG-8X to start with since it is cheap, I have it, and it would be good enough. Once I have the station dialed in I will make new jumpers with LMR-240-UF. I might use some double-shield RG-58 style cable for the pigtails. Having a flexible section of cable at rig is a good way to save wear and tear on the rig connectors. I also have to switch cables to switch modes as the 817ND is dedicated to uplink work.

At this point I have a very good portable LEO station with the advantage of the IC705 on RX. That gives me things like built-in audio recorder, easy/excellent filtering and preamp controls, and a waterfall display to watch for my signal and others while operating. I have seen at least one ham running a pair of IC705’s but that is something I will think about for Phase III. The main advantage would be not having to switch antenna feeds when moving from a V/U bird to a U/V bird, and having the duplication of accessories and connectors. Maybe one day…

Practical Issues

Once I started using the 817ND/IC705 pair I was hearing/seeing a rise in the 70cm RX noise floor when I transmitted on 2M (U/V Mode B, used on RS-44), especially on voice peaks. My initial suspicions were RF in the power feed or the headphone cable, or a third harmonic spur from the 817ND. Putting chokes on the power and headphone cables was good for peace of mind, and may have helped a little (noise reduction?), but it didn’t solve the problem. I will post a more complete description of the issue later, but the 3rd harmonic of 146Mhz is 438Mhz. And dang if I couldn’t just tune to 438 and see that signal clear and loud! Ugh.

Thus began a shakedown and testing program to either knock down the spurious signal or keep the third harmonic out of the 435MHz receive rig. My tools are the Arrow II duplexer, a Micro Circuits BLP-300+ LPF, and a HobbyPCB 2M bandpass filter. The best solution at first was using the Arrow II duplexer, connecting the common end to the radio and the 2M side to the 2M feedpoint. I installed a military surplus 5W BNC dummy load on the 435 side to keep things tidy in RF land. It’s not a bad solution, though I am thinking of building a high(er) performance 2M LPF that fits in the boom handle the way the Arrow duplexer does. I haven’t eliminated all of the crosstalk yet but a few changes have helped such as turning off the preamp on the IC705 and holding the antenna further from the radio while operating. I also assigned the BK-IN button on the IC705 to switch the preamp on/off so I can easily switch it while I operate. After initially using the duplexer as a LPF I am now using the Mini-Circuits BLP-300+. One reason is it makes the ARROW II much lighter and easier to point during a long pass, plus I found a cheap one on evilBay. It was actually a pull from a retired Piper aircraft! The standard choice for a LPF in this setup is the BLP-200+, and I have one ordered. We’ll see how that goes. The BLP-300+ only gives me about 38dB of attenuation at 438MHz, but it does help. I’m also not convinced that I don’t also have near-field RF from the 817ND.

Working Portable Solution

As of today the dust has settled and I am running the FT-817ND as my uplink rig, and the IC705 as the downlink rig, Heil PS6 headset, and an Arrow II with a Micro Circuits BLP-300+ low pass filter on the 2M side. I am using VOX with the headset plugged in to the IC705 audio output and the mic into the Heil adapter.

So far I have made 73 contacts to 57 unique stations in 52 grids (41 confirmed), and feel like I am just scratching the surface.

Even with some bugs to work out I am able to operate on linear LEOs and my skills are growing with every pass. I owe a huge debt to the amateur satellite community for their resources and support. The operator resources provided by AMSAT are valuable and motivational, and the community on Twitter, the Groups.io FT817 group, and YouTube, are a veritable master class in LEO equipment and operation. See a future post for a resource listing and more complete shout-outs.

I’ll close by saying I have not been as focused or obsessed over a ham radio project for a very long time. This is proving to be yet another collision of readiness and ability in my life. My fondness for VHF+, weak signal, portable operations has me right where I need to be. The fact that I have two HF+6+2+70 “shack in a box” radios made the initial foray into satellites possible. An understanding spouse has made it possible to make a concerted run at making this setup work in about three weeks of focused effort. See you on the birds! 73