Thursday, October 21, 2010

AO-51 Handheld!

Tonight's contact on AO-51 was quite fun! Rather than use my usual sat setup (the twin FT-817ND's and Elk antenna) I took my older Yaesu FT-530 dual-band radio hiking in a nearby park. The park is bisected by the -122 longitude line, so half is in CM88 and the other half is in CM98; there's a fire road that goes up to the top of a 800-foot hill with some radio towers. I arrived at the top of the hill just before an AO51 pass at 10/22/2010 0056 UTC -- and didn't expect to hear anything since I had only the stock 8" rubber duck on the antenna. The pass was a western (ocean) ascending pass with a max elevation of 30 degrees.

I was quite suprised at mid-pass when I could more-or-less clearly hear KI6IUJ in DM13! He was commenting that there weren't many people on the bird at the time, so quickly I gave him a call -- again, just using the stock duck on the antenna, with only two watts output. Imagine my amazement when he came right back to answer my call! Woohoo!! We exchanged grid squares, and I heard another ham calling me but at that point I lost contact with the bird, just noise after that.

Compounding the difficulty of this one was the fact that the Yaesu FT-530 is a true full-duplex dual band radio, so since I had forgotten to bring earphones or a speaker mike, every time I transmitted I had to manually turn the volume down and then back up again for RX. And it was raining at the time. But the contact with just a stock HT, out in a park in the rain on a hilltop with the sun setting, was a whole lot of fun!

Tuesday, October 19, 2010

Ham Radio Satellite Observations and Tips!

In no particular order, here is a list of the ham radio satellites that I have used so far. There's definitely a learning curve for using each satellite, and I've tried to add as much of the useful information as I can remember! Just FYI, the full rig setup is described in an earlier post, but to summarize I work portable with twin FT-817ND QRP radios and an Elk log-periodic dual-band antenna, for full-duplex operation on all of the linear and FM satellites.

AO-51: FM (2m up, 70cm down)
A fun satellite to work, easy to do with even a handheld. It's possible to work this bird with a rubber duck! There is no set daily schedule of operations, however the control team will change the uplink/downlink configuration periodically for a few days at a time. Often very crowded during weekends and during passes over central North America. From here in the west coast, ocean passes (west) are often fairly quiet, with just two to five hams on. Often hear Hawaii and Alaska from here in California. 5W into a directional antenna works great. Polarization stays pretty constant until mid-pass then seems to flip 30 to 90 degrees. The bird is sun-synchronous so there are good passes at start and end of day - the western passes at the end of the day are accompanied by a nice sunset. Often requires a CTCSS tone. The latest updates for AO-51 are located here.

SO-50: FM (2m up, 70cm down)
Less traffic than AO-51. No pre-set schedule, seems to use the same mode day-in and day-out. Also easy to work with 5W and a directional antenna. One quirk is that this bird seems to spontaneously change downlink frequency: I have recently seen it appear 10 kHz below published, and sometimes 5 kHz below. When this happens, it appears to be gone entirely (if using computer tuning) unless you switch to manual adjustment. You can overcome this by having multiple instances of the nominal downlink frequency in your control software. Requires a CTCSS tone to activate it (stays on for 10 minutes), and a separate CTCSS tone for uplink TX. Since this bird is not exactly sun-synchronous, there are some nice passes during the day, as well as nighttime passes.

AO-27: FM (2m up, 70cm down)
Fairly busy during passes. This satellite has scheduled operations, and is typically turned on as it comes over North America in afternoon passes. Fairly easy to work. There aren't any real quirks with this one, other than to be prepared for it to either not be there (if not turned on) or to suddenly turn off part way through the pass.

HO-68: FM/Linear (2m up, 70cm down)
This bird is often very crowded during weekend passes when in FM mode! This satellite is also scheduled, sometimes it's off, sometimes on, sometimes in FM, and sometimes in linear transponder (SSB) mode. The website usually has the current schedule for activation, and the satellite is often turned on for daylight passes over North America. If nothing is heard on FM when the satellite is expected to be active, check SSB because it's probably in linear transponder mode. The FM repeater also relays packets. so there are quite a few packet bursts during a typical pass. Requires a CTCSS tone. Seems to have a bit larger footprint than the other FM birds. This satellite often "ignores" uplink transmissions, for example, you can TX once, hear nothing on the downlink, then TX a few seconds later and hear yourself full quieting. This bird also seems to be "tumbling", in that the downlink polarization changes about every 30 seconds or so -- so handheld antenna polarization control is especially helpful. The latest updates for HO-68 are located here.

FO-29 Linear/SSB (2m up, 70cm down)
This linear transponder sat has a 2m uplink and 70cm downlink, and had a pretty much sun-synchronous shedule with morining and evening passes. However, as of mid-October, the power budget on the sat forced the operators to turn the unit off entirely, and then the bird failed to respond to any command signals. Currently it's silent. 5W and a directional antenna was plenty to work this one. We'll see if it comes back to life.

VO-52: Linear/SSB (70cm up, 2m down)
This one is 70cm uplink and 2m downlink, and makes some nice mid-morning and early-evening passes. The mid-morning passes usually have one or two conversations on them, while the evening passes (9pm local time, 0400UTC) are virtually devoid of anyone else! I find this to be a good sat for testing my radios with uplink/downlink calibration, etc -- even though I just talk to myself (call CQ) on this bird on the evening passes, it's still handy to make sure everything's working well. It's also good for practicing aiming the antennas, optimizing polarization, etc. The bird is fairly sensitive and quiet. Works well with 5W and a directional antenna.

AO-07: Linear/SSB (70cm up, 2m down)
This is the satellite that went "dead" many years ago with shorted batteries, then came "back to life" after the short went open-circuit. Since there are no functional batteries, the bird is only active in sunlight (which right now, given its orbit, is 24 hours a day), and switches between Mode A (2m up, 10m down) and Mode B (70cm up, 2m down) every 24 hours (currently around 0000 UTC). The website is a good one to check for the current mode. Since AO-07 is in a much higher orbit than any of the other satellites listed here, it has a much larger footprint. One thing I've found is that AO-07 seems to "disappear" on passes that go nearly directly overhead; this might be because when looking up underneath the sat, the antennas may not be oriented for best reception of my QRP signal with the small log-periodic. I haven't tried Mode A, but on Mode B, I've made some nice contacts out to 3000-mile range (maybe 15 degrees elevation).

Key Resources:
Real-time satellite status:
The AMSAT site:

Thursday, October 14, 2010

Twins! Portable QRP Satellite Station

For anyone that's interested, here's a complete description of the set-up I'm using for my portable sat operation. This is what I use for the satellite contacts, and is basically two twin FT-817ND radios hanging on a tripod, with an antenna above, and a netbook computer sitting beside. The system works great so far! I'll try to keep this description updated as things change, but this is what works for me right now...

1. Antenna, feedline, and diplexer.

I use an Elk Dual Band 2M/440L5 log-periodic antenna . The antenna is mounted to a lightweight photo tripod, with the mounting PVC pipe modified to fit the quick release adapter on the tripod (this allows easy removal of the antenna from the supporting tripod). This arrangement allows for easy azimuth, elevation, and polarization control during the pass.

The antenna is connected to the diplexer via a 6-foot length of RG-8X cable. The diplexer is a Diamond MX-72H unit that reportedly provides 60 dB of isolation between the 2m and 70cm input/output lines. The 2m ouput is marked with orange tape, the 70cm output is marked with blue tape; this color scheme helps to identify the appropriate cable connections for the whole system.

2. Radios.

The radios that I use are twin Yaesu FT-817ND all-band multimode portable QRP units. I don't have one radio dedicated to TX one to RX, but instead one is dedicated to 2m (RX and TX) while the other is dedicated to 70cm (RX and TX). In keeping with the color scheme, the 2m radio is marked with orange tape, while the 70com radio is marked with blue tape (quite necessary since both FT-817ND's look identical!). I also have the radio displays set so that the 70cm radio has a blue display while the 2m radio has an orange display:

The two radios hang via their shoulder straps from the apex of the tripod, and the appropriate feedlines from the diplexer feeds into the two radios. When working statellites in V/U mode (2m up and 70cm down, ie. AO-51, SO-50, HO-68, FO-29), I simply plug the microphone into the "orange" radio and the earphones into the "blue" radio. When working statellites in U/V mode (ie. VO-52 and AO-7), I simply unplug the mike and earphones and swap. The microphone is the stock Yaesu mike, and the earphones are an inexpensive pair on a retractable reel (this keeps them from getting tangled when not in use). Both radios are essentially using the default out-of-the-box settings. The two settings of importance are CAT BAUD RATE (32400) and make sure that the Squelch/RF Gain selector is set to Squelch, not RF Gain.

3. PC Connection.

Both radios are connected to the computer with CT-62 CAT cables. One cable is the authentic Yaesu CT-62 cable with a 6-pin mini-DIN connector on one end and a 9-pin serial DB9 connector on the other; this connects to a Cables-To-Go USB-Serial adapter. Both ends of this combined cable are marked with blue tape, and are used with the UHF radio. The other cable is an all-in-one CT-62 USB cable from Valley Electronics, which goes directly from the radio 6-pin mini-DIN to a USB connector. This cable is marked orange at both ends and controls the VHF radio. Both cables use the Prolific PL-2303 chipset, and I'm using driver version (installed in Vista SP2 compatibility mode, run as admin). The cables work equally well. Within Windows, one cable appears as COM4 (this is the orange "VHF" radio) and the other cable appears as COM3 (this is the blue "UHF" radio). As long as the same cables and same USB ports are used, this numbering is consistent, so the corresponding software settings only need to be set once.

4. Netbook Computer.

The computer that I use is a lightweight Samsung N150-Plus nebook . It comes with Windows 7 Starter, has three USB ports, and roughly a six-hour battery life. I chose the Samsung because of its matte screen; most netbooks these days have glossy screens, and I think the matte screen is easier to view in direct sunlight. Since I operate exclusively outdoors, it's important to have a screen that I can see! The backlight is plenty bright enough on the netbook to see the screen at any time of day.

So far, the Windows 7 on the netbook runs all the same applications as my home PC, with barely any performance difference (I don't notice it any slower). I've marked the USB ports on the computer orange and blue, to be sure that the interface cables for each radio always get plugged into the same port. This ensure that COM port number does not change. To keep things simple, I set the time zone on the computer is UTC so all software runs in UTC by default as well.

5. Software.

The software I use for radio control is SatPc32. The software is pretty easy to use, but more importantly, works very well!

I use the software with the default settings for everything except for the radio setup. The settings I use in the radio configuration screen are as follows: Setup > Radio Setup then Radio 1 = Yaesu, Model = FT-817, Baudrate = 38400, Com Port = 3, CAT Delay = 70, Autom RX/TX Change = checked, Radio 2 = Yaesu, Model = FT-817, Baudrate = 38400, Com Port = 4. (Note that the baudrate settings are part of the drop-down menu that toggles "Model" with "Baudrate". ) The screenshot below shows the radio setup for the twin FT-817ND's:

The software I use for satellite tracking is actually the satellite module from Ham Radio Deluxe. I use this software in "radar" mode, and have the radar plot of the satellite path on the screen underneath the SatPC32 software; this way I can see exactly where to aim the antenna, since the radar plot gives a nice graphical view of direction and elevation of the selected satellite. The radar view is also a good quick way to look for future passes.

I originally tried to use HRD for both radio control and tracking, but had fits with HRD locking up under Windows 7 when controlling the radio; SatPC32 has no such problem. In addition, SatPC32 seems to use a much more streamlined and efficient method of radio control than HRD (if you use both you'll see what I mean).

6. Power.
Everything runs on battery power, so this arrangement is super-portable! I simply use the internal rechargeable packs on the twin FT-817ND's and the laptop, and recharge them as necessary. On occasion I'll use a 7 ampere-hour sealed led acid (SLA) battery to power both radios: The battery has an Anderson PowerPole connector with fuse on top, that connects to a 1-foot-long 10-gauge jumper (with ferrite cores on either end). The jumper connects to a 4-way PowerPole splitter, into which are plugged two short barrel-connector-to-powerpole jumpers (one for each radio). The use of heavy-gauge wire on all but the short jumpers to the FT-817ND's prevents voltage drop that can affect the RX radio during transmit on the TX radio (important when listening to yourself on the downlink). While testing, and transmitting on 2m with the jumper disconnected from the SLA, I managed to reset the TX radio to factory defaults (!!!) probably via RF-feedback into the 1/4-wavelength long power cord. Hence the ferrite cores, and no more transmitting on internal batteries with the cord hanging loose.

7. Operation.

For portable operation (which is all I ever do since I don't operate indoors!), I carry the tripod (with attached antenna and radios) to the backyard (or to the pickup truck). I'll then start up the netbook computer and plug the CAT control cables into the orange/blue marked USB ports. I'll next start HRD to bring up the radar plot for the selected satellite, and after that start SatPC32. Next I'll select the satellite on SatPC32, and turn on CAT control (C+). I'll verify the radios are tracking the frequencies shown in the software, and also verify that the software frequency display tracks movement of the VFO knob on the radio used for RX. I'll then check to be sure the radios are in full-power (5W) mode by clicking the appropriate soft-menu buttons on the radio. At this point, the system is ready to go -- aim antennas and talk!

For the linear satellites (SSB), there is an extra step of using the SatPC32 CAT control dialog box to adjust the uplink frequency so that I can hear my audio clearly on the downlink -- out of the box, SatPC was needed about -2000 Hz correction for FO-29 and VO-52 and no correction for AO-07. This correction (calibration) can be saved so it's only necessary to adjust this a few times at first. The screenshots below show what the CAT control screen looks like:

And pressing "Change/Store Data File" brings up a new box allowing you to store the new uplink calibration in the DOPPLER.SQF file:

Occassionally, adjustments during the pass are necessary, sometimes if the keps are out of date, or if the computer clock isn't dead on (needs to be within about a second of UTC), or if the temp of the radios (or satellite!) has thrown off the frequency a little. During the pass, I'm sure to aim the antenna at the portion of the sky indicated in the radar plot, and I'll quickly toggle the polarization of the antenna side-to-side to find the best downlink polarization. This seems to be stable for the first and second half of the pass, but often changes during the middle.

Here's the operations checklist I typically use on a pass:

[] Start Netbook
[] Connect orange/blue CAT cables
[] Start both FT-817ND radios
[] Adjust TX radio power to 5W
[] Verify mike to TX radio and earphones to RX
[] Launch HRD sat tracking
[] Launch SatPC32
[] Select desired sat on SatPC32
[] Turn on CAT control on SatPC32
[] Turn on CTCSS encoding (AO-51, SO-50, HO-68)
[] Verify FT-817NDs are tracking
[] Turn VFO on RX radio; verify TX radio tracks freq changes
[] Adjust uplink calibration (linear sats only) using CAT menu

8. Results.

The system works great!! Working the FM sats (AO-51, SO-50, HO-68, and AO-27) is easy with the computer-controlled dopper correction, and there's no more need to manually tune the VFO's with these ones. In addition, having full-duplex on FM makes it much easier to tell if my transmission has collided with another ham, or if I'm making it into the bird at all (ie. HO-68 is a little bit finnicky, sometimes you transmit and no audio appears). Working the linear sats (HO-68, VO-52, FO-29, AO-07) is fun as well, and the arrangement works quite well. The only negative to the FT-817ND is that it doesn't update TX frequency while the PTT is keyed, so you need to unkey every once in a while for the TX to update for doppler shift.

It's amazing to me how well the Elk antenna and the diplexer work (thanks to N3TL for posting this idea!). It wouldn't seem possible to be able to hear a 250 mW signal coming from >2000 miles away on the exact same antenna that is transmitting 5W PEP simultaneously, but I've seen over and over again that it works. And works well!

So far, I've made quite a few contacts on all of the aformententioned birds. When operating out in the open (ie. sitting in back of pickup truck with clear view to west) I have found I can easily hear myself coming back on the downlink for sats down to about 3 degrees above the horizon (over 6,000 miles round-trip!). I've also found that the hams in the satellite community are a great group, and really appreciate all the help and advice they've provided so far!