Amateur Radio Satellites

Allen Mattis N5AFV, Houston, TX

I made my first satellite contact on 16-July-2000, after seeing a satellite demonstration at Field Day a few weeks earlier.  The equipment used at the Field Day demonstration consisted of an Icom W32A HT with an AL800 telescoping antenna.  I own an Icom W32A HT, and I immediately realized that I could use it to make satellite contacts.  I soon became hooked on operating satellites, and amateur radio satellite operation has become my primary hobby. 

One of my favorite amateur radio activities is to operate on the OSCAR satellites whenever I travel. I have operated on amateur radio satellites from 144 different Maidenhead grid squares, from 17 different DXCC entities, and from three continents.  I especially enjoy operating on the satellites from cruise ships while on vacation. See my Cruise web page more for information about operating on cruise ships.

I also enjoy meeting in person with the many different people I have worked through the satellites. Pictures of a number of these operators may be found in Gallery 1, Gallery 2, Gallery 3. and Gallery 4.

E-mail - afmattis@hal-pc.org

Links to Useful Amateur Radio Satellite-Related Websites

AMSAT and ARRL

Satellite Operator Home Web Sites

Satellite-Specific Web Sites

Call Sign Databases

Pass Prediction and Keplerian Elements

Maidenhead Grid Squares

HT and AL800 Antenna – An Excellent Portable Satellite Station

I do a great deal of operating on the FM LEO satellites with my Icom W32A HT and a Premier (Pryme) AL800 antenna.  As of July 6, 2008, I have made 8943 satellite contacts using that equipment.  The AL800 does not receive as well as an Arrow, but it is far more portable and does not attract unwanted attention.  I wrote an article for the AMSAT Journal that describes how I use the AL800 antenna and the success I have had using it.

AMSAT Journal Article: HT and AL800 Antenna – An Excellent Portable Satellite Station

 


An HT with an AL800 telescoping antenna makes a very compact satellite station that can fit in your pockets when disassembled.

 

QHtenna 70 cm Turnstile Antenna

In the August 2004 issue of QST (page 60), Steve Ford, WB8IMY, reviewed the 2 meter and 70 cm turnstile antennas made by QHtenna. I have worked Steve on SO-50, and know that he has experience on the amateur radio satellites.  In his review, Ford wrote “I had consistently good reports working through the OSCAR 27 and 29 satellites.”   In his tests, Steve used the QHtenna turnstiles for both uplink and downlink.  I had been looking for a small 70 cm antenna to use mobile for my downlink antenna when working the LEO satellites and the review piqued my interest. Lyle Dysinger, N4QH, designed, manufactures and sells the QHtenna.  Lyle lives in Toccoa, GA, and maintains a web site at ( http://www.qhtenna.com/main/page_turnstyle_enlarged.html ) where you can learn more about the QHtenna.  

 

The QHtenna 70 cm turnstile is made from one-inch PVC pipe and 3/16-inch aluminum rods.  It comes disassembled, but is easy to put together.  The components consist of a 10-inch long piece of PVC pipe with pre-drilled holes, a PVC cap to seal the top of the antenna, four bolts, four aluminum rods with locking nuts, and a coax phasing harness with terminal lugs already attached to both ends You must supply the coax feedline and any hardware needed to mount the turnstile.  I used a 10-foot piece of RG-58 coax that had a PL259 on one end, and soldered lugs on the other end of the coax to use to attach the feedline to the antenna.  At Home Depot I picked up another PVC cap for base of the antenna, and drilled holes in it to attach the coax feedline, and to bolt the antenna to a mag-mount base.  My completed 70 cm turnstile is approximately 12 inches tall and 12 inches wide.  This turnstile antenna reminds me very much of the antennas featured on the K5OE web page ( http://members.aol.com/k5oe/). It would be easy to build yourself, but at a cost of $19.95 plus shipping, I had no hesitation in ordering one.

 


QHtenna 70 cm turnstile fully assembled with mag-mount base. Approximate height and width 12 inches.

 

The first two passes I worked with the turnstile antenna were encouraging. On an AO-27 pass with an elevation of 88 degrees, I made four contacts from my mobile while in motion on a city street at a speed of 25 mph. I heard the satellite continuously for approximately four minutes of the pass. On an SO-50 pass with an elevation of 67 degrees, I made three contacts from my mobile while in motion on an expressway at a speed of 60 mph. I heard the satellite continuously for approximately two minutes of the pass.  I have now used the QHtenna 70cm turnstile for 18 months, and have worked 77 satellite passes and made 277 contacts.

 

 

I have worked AO-27, SO-50 and AO-51 while using the turnstile antenna, and I have found that it is generally easiest to hear AO-51 and it is the most difficult to hear SO-50. The most contacts I have made in a single pass with the turnstile was on an AO-51 pass with a maximum elevation of 89 degrees when I made 16 contacts. This was clearly an exceptional situation with all conditions being favorable, and such performance can not be expected on a regular basis. The lowest elevation pass I have worked with the turnstile antenna was also on AO-51 with a maximum elevation of 18 degrees, and I made five contacts.   The QHtenna 70cm turnstile works quite well to receive the LEO satellites for passes with a maximum elevation greater than 30 degrees.

 

 

 

Most of the time I use the turnstile antenna while my vehicle is in motion, but I have also used it while parked when I did not want to draw attention by holding a beam antenna out the window. I use an ARR SP432VDG preamp with the turnstile antenna. When I first began using the turnstile antenna, I would seldom hear myself in the downlink due to desensing. I have solved that problem by putting as much distance as possible between the turnstile and the trunk-mounted 2m vertical I use for uplink.

 


Putting as much distance as possible between the turnstile and the trunk-mounted 2m vertical

I use for uplink has, for the most part,  solved a desensing problem.

 

I currently operate many passes from my mobile while stationary, and hold an Arrow antenna with only the 70 cm elements installed out the window for my downlink antenna. Using this configuration often gets me questioned by police and security guards. The QHtenna turnstile antenna allows me to work some satellite passes from my mobile without attracting unwanted attention.  It also gives me the ability to operate while in motion. 

Using the MFJ-1800 2.4 GHz Antenna for a V/S Mode Downlink Antenna

When I read the excellent article by Drew Glasbrenner, KO4MA, (Mode V/S on AO-51: Something New Under the Sun, The AMSAT Journal, July/August 2005, pp. 14-16) and the short note by Aruni Perera, VE4WMK, (Field Day Fun in Canada, The AMSAT Journal, July/August 2005, p. 22) I decided that I needed to try this mode.  After all, I enjoy operating on the amateur radio satellites because I continually learn new things, and using a downconverter and radio wave propagation on 2400 MHz were two areas that I had no experience with. I ordered a K5GNA downconverter (www.k5gna.com) and was soon making contacts on AO-51 when it was in V/S mode.

 


The K5GNA downconverter with 2400 MHz dipole and corner reflector for working V/S mode is advertised as having 12 dBi gain.

 

The K5GNA downconverter with corner reflector is advertised as having 12 dBi gain; however, I have difficulty hearing the downlink when the satellite is below eight degrees elevation. I was looking through the latest MFJ catalog when I noticed a 2.4 GHz 16-element WiFi Yagi with an advertised gain of 15 dBi, and decided to order one and see how it compared to the K5GNA dipole and corner reflector. 

 

 

The MFJ-1800 antenna is actually quite fragile, and the instructions that come with it state that “The MFJ-1800 WiFi Yagi Antenna is intended for applications protected from the elements – out of the weather.   It can be made weatherproof by mounting inside a 3-inch PVC pipe.”  The MFJ-1800 comes with a standard “N” connector, and I used a CABLE-X-PERTS CXP1318FN 3-foot jumper to connect the MFJ-1800 to the K5GNA downconvertor. 

 


The MFJ-1800 antenna is actually quite fragile and should be mounted inside 3-inch PVC pipe if it is installed where it is exposed to the elements.

 

I was anxious to compare the performance of the antennas to see if the 15 dBi Yagi would outperform the 12 dBi dipole and corner reflector.  I used the MFJ-1800 to work three passes of AO-51 when it was in V/S mode.  On the first pass (16 degree maximum elevation) I was unable to hear the satellite; however, it was a Sunday evening and AO-51 may not have been switched over to V/S mode until late in the pass.  I tried a second pass (35 degree maximum elevation) and had much better results.  I could hear the downlink and managed to make four contacts; however, the downlink signals seemed to be weaker than with the dipole and corner reflector, and there was considerable fading.  I tried a third pass (14 degree maximum elevation) and heard many stations, but was unable to complete a contact.  Whenever I called another station, significant fading made it impossible for me to tell if the station I had called answered me. 

 

So, what did I learn about the MFJ-1800 antenna in this first attempt to use it for V/S mode?  Amateur radio operators soon learn that the gain numbers published in antenna advertisements are commonly exaggerated.  Also, note that in the MFJ catalog description shown above, both 15 dB and 15 dBi gain are used to describe the antenna.  My very limited use of the MFJ-1800 suggested that it may have less gain than the K5GNA dipole and corner reflector.  I discussed the performance of the MFJ-1800 antenna with two friends that have had more experience working with higher frequencies.  Both Andy Mac Allister, W5ACM, and Jerry Brown, K5OE, felt that using the 3-foot jumper cable to connect the MFJ-1800 antenna to the K5GNA downconverter might have caused significant signal loss.  Jerry’s exact words to me were “If you want to make a fair comparison, get a M-M N-connector and directly couple the antenna to the downconverter.” 

 


The MFJ-1800 antenna coupled directly to the K5GNA downconverter with an M-M N-connector

 

The March 13-19 and May 2-3, 2006 periods of V/S mode on AO-51 provided a good opportunity to test the MFJ-1800 antenna coupled directly to the K5GNA downconverter.  I was pleased to find that the MFJ antenna appears to outperform the K5GNA dipole with corner reflector.  Using the MFJ antenna, I operated an AO-51 pass with a four degree maximum elevation from the top of a parking garage where I had a clear horizon and made three contacts, and a five degree maximum elevation pass I made one contact.  I also tried a pass with a two degree maximum elevation from the same parking garage using the MFJ-1800 antenna and I heard a carrier on the downlink frequency, but was unable to detect any voice or modulation.  During an earlier period of V/S operation on AO-51, I operated from the same location on two eight degree maximum elevation passes and struggled to make two and three contacts with the K5GNA dipole and corner reflector.  On higher elevation passes I did not observe any significant difference between the two antennas.  With either antenna it was common to make five to eight contacts depending on how many people were working the higher elevation passes.

 

I also observed that it was necessary to rotate the K5GNA dipole with corner reflector quite frequently to compensate for fading of the downlink signal.  The MFJ Yagi antenna did not appear to be affected as much by fading and required less rotation.  I must also state, however, that the K5GNA dipole with corner reflector is very sturdy and rugged, while the MFJ-1800 antenna is somewhat fragile.  Another drawback to using the MFJ-1800 is that it is quite directional, and I sometimes lost the bird for short periods of time until I repositioned the antenna to point more directly at the satellite.

 



The bottom line is that the MFJ-1800 antenna allows me to work lower elevation passes of AO-51 in V/S mode than I can with the K5GNA dipole and corner reflector.  The slight difference in performance of the two antennae on high elevation passes may result from the directivity and difficulty aiming the MFJ Yagi directly at the satellite. My purpose in posting these observations is to make others aware of this antenna and its possible use in working satellites.  After all, experimentation and learning is what satellite and space communications are all about. 

 

E-mail - afmattis@hal-pc.org

Created: October 26, 2002 by Allen F. Mattis
Last Updated: July 6, 2008