Category: radio

Clint Bradford

Work AO-51 with your FT-817…or just about any dual-band HT!

Summary: Program a channel with split freqs, per your owners manual.

The Details: The two primary modes of operations for AO-51 are FM analog voice and 9600-baud packet. AO-51’s transmitters have variable power output, and can operate as high as 8 Watts output on 70cm. Hams are successfully working the satellite with HTs!

In AO-51’s V/U mode, the UPLINK (to AO-51) freq for voice is 145.920MHz with a 67.0Hz CTCSS tone. The DOWNLINK (from AO-51) freq is 435.300MHz (no tone).

First, you need to know WHEN and WHERE the satellite will be passing over your location. There are several computer programs that will tell you. In the home office, I use Nova for Windows[1]. Outside, though, I use PocketSat[2] on my Garmin iQue 3600 PDA and Verizon Wireless Treo 650. Both programs are easily updated with current satellite tracking data that is available on the Internet. Or, you can go to…

http://www.heavens-above.com -or- http://www.amsat.org

…and sign up. Using your longitude and latitude coordinates, you can access amateur satellite pass information (and a lot more!).

The one “absolute” for success is to open up your squelch. Working satellites starts off as a process of finding weak signals, so don’t expect the satellite to be anywhere as strong enough to break squelch like your local repeater. It’s noisy, but that’s part of the process. Noise can also be an aid in locating the satellite because when the frequency starts to exhibit QUIETING, that’s a sure sign that you are hearing the satellite!

Use a good antenna for your handheld. A good gain whip antenna like Pryme’s AL-800[3] (not for SMA connectors, though!) will make the difference. Using an Arrow dual-band[4] is better, and if you prefer to homebrew your antenna, Alex Diaz XE1MEX[5] has an excellent Yagi-Uda.

Set up your radio so you can to tune for the doppler effect. Start listening 5 KHz above the center frequency[6] – you will hear the satellite sooner and clearer. When you hear the downlink signals get scratchy or fuzzy, tune down 1KHz at a time, and reception should be clearer. Follow the signal down in frequency as the pass continues.

Don’t hold your whip antenna upright. Vertical antennas are not as efficient, and a HT held upright isn’t either. The satellite isn’t on the ground (which is what HTs and vertical antennas were designed for). TILT IT about the same amount as the satellite’s ELEVATION. This means that if you are FACING the satellite, tilt it down towards the ground from HORIZONTAL an equal amount. If the satellite is to your back, tilt it up an equal amount away from the satellites position off the vertical. You will be surprised at the difference.

Many use headphones – especially if working full duplex. If you have an Icom IC-W32A, you can listen to your own downlink (helpful, but not necessary). Your brain can be better at discriminating signals than most expensive DSPs.

Knowing your gridsquare – and having a gridsquare map – is a quick way of identifying locations of what you will be hearing. The ARRL and Icom have some dandy gridsquare maps, the latter of which are free at better amateur radio stores[7].

Remember the “three Ps” for working amateur satellites: preparation, planning, and patience. Not every pass is workable with an HT or listenable with a scanner – so don’t go after the 10 degree passes. Pick your passes, and work the ones you know will give you the best chance.

When you hear others, try to find a break in the action, and announce your callsign, grid square, and op mode, like this:

“KILO-SIX-LIMA-CHARLIE-SIERRA, D-M – ONE-THREE, handheld.”

Many hams record their sessions for later review. Even if you don’t make contacts, it helps to accustom yourself to the callsigns, voices and personalities of the other operators. When I first started out, I found it more valuable to know which contacts I missed rather than the ones I made.

Ask questions! Find an elmer or look up the AMSAT[8] area coordinator for your area. Posting specific questions on the AMSAT bulletin board will also help you find answers.

Clint Bradford, K6LCS
Email: clint@clintbradford.com
Updated 07/17/06

Notes

[1] Nova for Windows is available from Northern Lights Software Associates’ Web site at: http://www.nlsa.com

[2] PocketSat is available from Big Fat Tail’s site: http://www.bigfattail.com

[3] The Pryme AL-800 telescopes to 34″ and collapses to 10″. Is is packaged with a 9″ rat tail – which you can use for everyday use. Use caution with this massive, heavy antenna: It has the potential of placing a lot of stress on your radio’s BNC connector. Pryme claims gain figures of 3.2 dB on VHF and 5.5 dB on UHF. Available at better amateur dealers – including Ham Radio Outlet – HRO.

[4] Arrow’s Model 146/437-10WBP is a dual-band cross-Yagi design, with a duplexer built into the handle. It has three elements on 2M and 7 elements on 440. (You’ve seen pictures in QST and elsewhere of operators using this great antenna!) Also available at HRO – see it on Arrow’s Web site at…
http://www.arrowantennas.com/146-437.html

[5] Alex has performed a lot of work on suitable homebrew antennas for satellite enthusiasts. His Web site is: http://xe1mex.gq.nu/antenas/yagi.html

[6] For example, here’s how I have programmed my FT-817 for AO-51:

Ch # Name TX Freq CTCSS RX Freq CTCSS
101 51 -2 145.920 67.0 435.310 None
102 51 -1 145.920 67.0 435.305 None
103 51 MID 145.920 67.0 435.300 None
104 51 +1 145.920 67.0 435.295 None
105 51 +2 145.920 67.0 435.290 None

[7] Icom’s map is available at the Anaheim HRO, and also available as a .pdf file on their Web site at: http://www.icomamerica.com/downloads/usgridsq.pdf

[8] AMSAT deserves your support! Membership isn’t that expensive, and members are entitled to discounts on AMSAT publications and satellite tracking software!

http://www.amsat.org

Clint Bradford, K6LCS
clint@clintbradford.com