[amsat-bb] DJ-G7T and full-duplex satellite operating - the 2018 sequel

Thu Feb 15 03:47:45 UTC 2018

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 at 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
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