AO-51 set-up for ARRL Field Day

AO-51 Field Day Announcement from the Echo Operations Group

For the ARRL Field Day Event this year AO-51 will be configured in Mode V/S FM Repeater. The uplink will be 145.920 mHz. The 67 Hz tone will NOT be used. The downlink will be 2401.200 mHz.

There will be a long duration operating session leading up to Field Day when AO-51 will be configured in Mode V/S to give users the opportunity to test their Field Day stations.

In June, AO-51 will be in Mode V/S the weekend and entire week before Field Day. Take advantage of these operating sessions to setup and test your Field Day station before the actual day arrives.

Gould Smith, WA4SXM, listening to Echo in his backyard during one of the first times that Echo's S band transmitter was turned on. Hardware includes a G3RUH patch feed, Transystem Downconverter, and a HT as the IF receiver. Just about as simple as it gets, and it shows that the S band downlink on AO-51 is accessable with a very small hardware package

Working the Mode S downlink on AO-51 does not require a large investment in equipment for your Field Day station. A satellite dish is not required to operate this mode. Gould, WA4SXM, copied the S downlink using just his G3RUH patch feed during the early days of testing the S band transmitter on Echo.

Drew, KO4MA, has operated portable with a Transystems downconverter using the dipole feed and a corner reflector on numerous occasions.

Mike, KE4AZN, has operated portable with either a 3.5 turn helix feed (feed only, no dish) or a homebrew K5OE patch antenna, held out the window of the car. Mike has also operated mobile on Mode V/S by attaching the helix feed and downconverter to the trunk of the car.

Clare, VE3NPC, has reported excellent receive signals using a 3.5 turn helix and a K5GNA downconverter.

Any of these Amsat members can be contacted at their "@amsat.org" email address and would be happy to help Field Day users get setup for Mode V/S. If your IF is on VHF (which most are), an HT or other mobile FM rig will work fine as your downlink receiver. The large 5 kHz steps of these radios actually make tuning the fast moving Doppler on S band much easier.

Use the scheduled Mode V/S sessions to practice before heading out for Field Day. If you have not worked the S band downlink on AO-51 previously, a few passes monitoring the downlink and practicing the Doppler correction will be very helpful. The Doppler shift on an AO-51 pass is approximately +/- 50 kHz. There will be lots of activity on Field Day, therefore getting your Receive capability working well before transmitting to the satellite, will keep your station from causing unnecessary QRM.

The uplink for AO-51 does not require a large Yagi antenna to be successful. Any good mobile omni direction whip antenna or other omni directional antenna will work fine, especially if all stations work together during the passes and not try to dominate the satellite. Therefore, it should not be difficult to setup an antenna that will work for the uplink to AO-51. If you have a Field Day station with Mode V/U capability, you already have the uplink covered.

A webpage will be setup with a few pictures and text on various AO-51 Mode V/S station options. This will not include every option available, but will hopefully assist a new Mode V/S user with some ideas to get started setting
up their station, and show that is it not difficult to get setup and working the S downlink on AO-51.

Web URL: http://www.graceba.net/~mkmk518/echofieldday.html

With the V/S configuration of AO-51 and the other satellites available, we will have a nice compliment of modes to operate during Field Day.

73 KE4AZN for the Echo Operations Group

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