DJ-G7T and full-duplex satellite operating - the 2018 sequel
Hi!
After dusting off my old Alinco DJ-G7T for use with AO-92's L/V configuration, I have been using it for AO-92's U/V mode and on other satellites. I wanted to see how it would do with U/V satellites in particular, given how it performed with V/U satellites like AO-27 and AO-51 when I bought the radio in 2009. I have also seen some recent comments online stating that this radio is good for satellite work. It can be, but only in certain situations.
Back in 2009, I was able to make the DJ-G7T work full-duplex with AO-51, with a post titled "DJ-G7T and full-duplex satellite operating":
http://amsat.org/pipermail/amsat-bb/2009-May/019177.html
I turned off the extended (non-ham) receive coverage in my DJ-G7T, and it worked. I remember that, even at the city park I used for much of my operating then, the radio would be very sensitive to other signals way outside the 70cm band when working the U/V FM satellites of that time. I never was able to work SO-50 full-duplex then, with its weaker downlink compared to AO-51 and AO-27. After almost 9 years, nothing has changed there. I just tried to work SO-50 this morning with the DJ-G7T and Elk log periodic, yet I never even heard the downlink once during a 39-degree pass. The downlink VFO's S-meter was pegged for most of the pass, probably from some other RF the radio was receiving. Even using the clock- shift menu setting didn't improve things. I won't bother using my DJ-G7T with SO-50 in the future, unless I have another radio for the downlink.
In the past couple of years, we have had some U/V FM satellites (AO-85, AO-91, AO-92) that we never had back in 2009. Simply switching the uplink and downlink bands has been a cure for receiver desense in other radios like the Icom IC-W32 or Wouxun KG-UV9D when trying to work full-duplex, but it's not so simple with the DJ-G7T. Depending on the pass and the antenna I'm using, I can still have receiver desense on 2m while transmitting on 70cm to any of these satellites. When I am able to overcome the receiver desense on 2m, the DJ-G7T works fine for the U/V FM satellites. This normally means I am using my Elk, and not other antennas like the MFJ-1717 long duckie I have used with a few other HTs. For higher passes, I am able to use the DJ-G7T with the MFJ-1717 and hear myself while transmitting through AO-91 or AO-92, but not near AOS or LOS when the receiver desense covers up the downlink.
If I am only receiving the 2m downlinks from the 3 current Fox-1 satellites, and not trying to transmit to the satellite, the DJ-G7T can be a good receiver. All of this is dependent on the surrounding RF that the DJ-G7T might pick up, of course. What works in one location, may not work the same in another location. I demonstrated this with two videos I recently posted on YouTube. Here is an AO-91 pass from 6 February:
https://www.youtube.com/watch?v=jSK_v3L_RHk
And an AO-92 pass, earlier on the same day:
https://www.youtube.com/watch?v=E3nfO4tKEAI
I have also posted some audio recordings and pictures of the DJ-G7T used with these two antennas on AO-91 and AO-92 passes in my Dropbox space. Go to http://dropbox.wd9ewk.net/ and look for the "DJ-G7T" folder. In there, I have subfolders for different passes I have worked with this radio. Some of the U/V passes were worked with the Elk as the antenna, and some with the MFJ-1717.
As an uplink radio, the DJ-G7T has performed well with the U/V FM satellites and for AO-92's L-band uplink. I had to increase the mic gain from 3 to 4 (maximum), and I have only received good reports on my transmitted audio. My signals may be down a bit on 1.2 GHz if my tuning isn't keeping up with the Doppler and AO-92's uplink AFC is having to work, but I have been getting through with this HT (1W on 1.2 GHz) and an old 5-band Yagi mounted on the antenna connector. I have not tried using this radio for the uplink with SO-50, but I am confident that using a DJ-G7T with a different radio for the downlink would also be acceptable for SO-50.
I went back and read through the QST review of this radio from April 2010. The review mentioned trying this radio on AO-27. The reviewer mentioned hearing slight interference when working full-duplex. That must have been done from a very RF-quiet location, and on a very high pass. When I heard any non-ham intermod on 70cm, that would tend to cover up the downlinks from AO-27 or AO-51.
I have liked my DJ-G7T for non-satellite uses, as it is a neat little radio which includes 1.2 GHz. This HT, along with the 5-element Yagi I have had for a long time, has been my uplink setup for AO-92's L/V configuration over the past couple of weekends. For satellite use, I think it would be great as an uplink radio for the 3 bands, and might be useful for full-duplex operation on the U/V satellites, but comes up way short with the only V/U FM satellite we currently have (SO-50). I don't have an antenna that would let me see if the DJ-G7T could work AO-92's L/V configuration full-duplex, but that would be interesting to see. I won't sell my DJ-G7T, and will continue to recommend the TH-D72 for anyone looking for an HT currently in production to work V/U and U/V FM satellites full-duplex. Otherwise, there are many HTs that can work V/U and U/V FM satellites that have been out of production, or there is always the option of using two radios.
73!
Patrick WD9EWK/VA7EWK http://www.wd9ewk.net/ Twitter: @WD9EWK or http://twitter.com/WD9EWK
As always, an excellent and insightful writeup. Thank you for taking the time to test and document the DJ-G7T.
I was hoping for a better outcome, but can work around its shortcomings. I bought mine to provide a more portable solution for AO-92 and the soon to launch Fox-1Cliff and Funcube ESEO satellites. Even if I can only use it as an L-band uplink, I still think I made a smart choice.
I will let you know how the eBay 5-element yagi performs, once that slow boat arrives from China (due NLT Mar8).
Thank you and 73,
Robert Bankston | KE4AL Website: www.ke4al.wordpress.com Twitter: @KE4ALabama
On Feb 14, 2018, at 9:58 AM, Patrick STODDARD (WD9EWK/VA7EWK) amsat-bb@wd9ewk.net wrote:
Hi!
After dusting off my old Alinco DJ-G7T for use with AO-92's L/V configuration, I have been using it for AO-92's U/V mode and on other satellites. I wanted to see how it would do with U/V satellites in particular, given how it performed with V/U satellites like AO-27 and AO-51 when I bought the radio in 2009. I have also seen some recent comments online stating that this radio is good for satellite work. It can be, but only in certain situations.
Back in 2009, I was able to make the DJ-G7T work full-duplex with AO-51, with a post titled "DJ-G7T and full-duplex satellite operating":
http://amsat.org/pipermail/amsat-bb/2009-May/019177.html
I turned off the extended (non-ham) receive coverage in my DJ-G7T, and it worked. I remember that, even at the city park I used for much of my operating then, the radio would be very sensitive to other signals way outside the 70cm band when working the U/V FM satellites of that time. I never was able to work SO-50 full-duplex then, with its weaker downlink compared to AO-51 and AO-27. After almost 9 years, nothing has changed there. I just tried to work SO-50 this morning with the DJ-G7T and Elk log periodic, yet I never even heard the downlink once during a 39-degree pass. The downlink VFO's S-meter was pegged for most of the pass, probably from some other RF the radio was receiving. Even using the clock- shift menu setting didn't improve things. I won't bother using my DJ-G7T with SO-50 in the future, unless I have another radio for the downlink.
In the past couple of years, we have had some U/V FM satellites (AO-85, AO-91, AO-92) that we never had back in 2009. Simply switching the uplink and downlink bands has been a cure for receiver desense in other radios like the Icom IC-W32 or Wouxun KG-UV9D when trying to work full-duplex, but it's not so simple with the DJ-G7T. Depending on the pass and the antenna I'm using, I can still have receiver desense on 2m while transmitting on 70cm to any of these satellites. When I am able to overcome the receiver desense on 2m, the DJ-G7T works fine for the U/V FM satellites. This normally means I am using my Elk, and not other antennas like the MFJ-1717 long duckie I have used with a few other HTs. For higher passes, I am able to use the DJ-G7T with the MFJ-1717 and hear myself while transmitting through AO-91 or AO-92, but not near AOS or LOS when the receiver desense covers up the downlink.
If I am only receiving the 2m downlinks from the 3 current Fox-1 satellites, and not trying to transmit to the satellite, the DJ-G7T can be a good receiver. All of this is dependent on the surrounding RF that the DJ-G7T might pick up, of course. What works in one location, may not work the same in another location. I demonstrated this with two videos I recently posted on YouTube. Here is an AO-91 pass from 6 February:
https://www.youtube.com/watch?v=jSK_v3L_RHk
And an AO-92 pass, earlier on the same day:
https://www.youtube.com/watch?v=E3nfO4tKEAI
I have also posted some audio recordings and pictures of the DJ-G7T used with these two antennas on AO-91 and AO-92 passes in my Dropbox space. Go to http://dropbox.wd9ewk.net/ and look for the "DJ-G7T" folder. In there, I have subfolders for different passes I have worked with this radio. Some of the U/V passes were worked with the Elk as the antenna, and some with the MFJ-1717.
As an uplink radio, the DJ-G7T has performed well with the U/V FM satellites and for AO-92's L-band uplink. I had to increase the mic gain from 3 to 4 (maximum), and I have only received good reports on my transmitted audio. My signals may be down a bit on 1.2 GHz if my tuning isn't keeping up with the Doppler and AO-92's uplink AFC is having to work, but I have been getting through with this HT (1W on 1.2 GHz) and an old 5-band Yagi mounted on the antenna connector. I have not tried using this radio for the uplink with SO-50, but I am confident that using a DJ-G7T with a different radio for the downlink would also be acceptable for SO-50.
I went back and read through the QST review of this radio from April 2010. The review mentioned trying this radio on AO-27. The reviewer mentioned hearing slight interference when working full-duplex. That must have been done from a very RF-quiet location, and on a very high pass. When I heard any non-ham intermod on 70cm, that would tend to cover up the downlinks from AO-27 or AO-51.
I have liked my DJ-G7T for non-satellite uses, as it is a neat little radio which includes 1.2 GHz. This HT, along with the 5-element Yagi I have had for a long time, has been my uplink setup for AO-92's L/V configuration over the past couple of weekends. For satellite use, I think it would be great as an uplink radio for the 3 bands, and might be useful for full-duplex operation on the U/V satellites, but comes up way short with the only V/U FM satellite we currently have (SO-50). I don't have an antenna that would let me see if the DJ-G7T could work AO-92's L/V configuration full-duplex, but that would be interesting to see. I won't sell my DJ-G7T, and will continue to recommend the TH-D72 for anyone looking for an HT currently in production to work V/U and U/V FM satellites full-duplex. Otherwise, there are many HTs that can work V/U and U/V FM satellites that have been out of production, or there is always the option of using two radios.
73!
Patrick WD9EWK/VA7EWK http://www.wd9ewk.net/ Twitter: @WD9EWK or http://twitter.com/WD9EWK _______________________________________________ Sent via AMSAT-BB@amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb
participants (2)
-
Patrick STODDARD (WD9EWK/VA7EWK) -
Robert Bankston