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DJ-G7T for FM satellites

Discussion in 'Satellite and Space Communications' started by WD9EWK, Feb 14, 2018.

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  1. WD9EWK

    WD9EWK Ham Member QRZ Page

    It might take a fair bit of work to get that usable for 23cm satellite uplinks, which are at 1260-1270 MHz. From the FM satellite frequency list on the AMSAT web site, you would want to prepare for uplinks around 1267 MHz (AO-92, Fox-1Cliff) and 1263 MHz (FUNcube payload on ESEO). Since you said that unit was supposed to output across a 4 MHz range, it might be possible to adjust it so that the 4 MHz range is 1263-1267 MHz instead of 1296-1300 MHz. Looks like someone may have been trying that already, given that tag showing 1291.976 MHz as an output frequency.

    You could use an SDRplay SDR (or other receiver covering that band) to see where the output is for that device. Set a wide range in the SDR software, and transmit at low power. Do you have an antenna for the 1.2 GHz band? I don't know how far away from 432 MHz you can transmit, to bring the output frequency down to 1263 or 1267 MHz. I'd guess you would still need to make adjustments to get the output down to the satellite subband, instead of the weak-signal subband at the high end of the band.

    It might be useful to visit other forums/mailing lists related to EME or general weak-signal activity with your questions about this, as well as the satellite-related forums/lists.

    73!
     
  2. K8TDN

    K8TDN Subscriber QRZ Page

    I found someone that had more knowledge of what I have.. The unit is a tripler so the input frequentf is tripled in the output so I need to trasmit around 422 mhz or About still need to test..and maybe pick up antenna at hamvention this weekend. Again thanks for replying
     
  3. WD9EWK

    WD9EWK Ham Member QRZ Page

    Just find a radio that radio that can transmit just above 420 MHz, and you can test it for the satellite subband. Depending on the radio, a modification may be needed. Many HTs covering the 70cm band will transmit down to 430 MHz, not 420 MHz.

    Hope to hear you on L/V sometime!
     
  4. K8TDN

    K8TDN Subscriber QRZ Page

    Thinking of this for use on 1.2 ...KENWOOD TM-541.
    Would this do for uplink inputs appreciated

    Terry k8tdn
     
  5. WD9EWK

    WD9EWK Ham Member QRZ Page

    Like most mobile radios for 1.2 GHz, it has a 10W transmitter. The challenge for this radio is its tuning steps (10, 12.5, 20, and 25 kHz). With the AFC on the uplink receivers of the Fox-1 satellites like AO-92, you might have some success with the radio using 10 kHz steps. Unfortunately, most older HTs and mobile radios for 1.2 GHz didn't come with 5 kHz tuning steps like the DJ-G7T which has been on the market since 2009.

    73!
     
  6. K8TDN

    K8TDN Subscriber QRZ Page

    Thanks .I think I will just hettje DJ-G7T
     
  7. WD9EWK

    WD9EWK Ham Member QRZ Page

    If you are only going to use a 1.2 GHz radio as an uplink for AO-92 and the upcoming Fox-1Cliff, the HT may be a good way to go. If the price of that TM-541 is low enough, it might be worth it just to have around for anything 1.2 GHz in analog FM.

    I am still improving on the fine art of tuning the uplink on those passes, and that's with 5 kHz steps. One of these days or evenings, I may try my HT with 10 kHz steps. It would be interesting to see if the AFC on the uplink receiver can deal with the larger steps. Don't know if I will go to 12.5 or 25 kHz steps, as that might be going a bit too far, but we'll see. I can always reset the tuning steps on the DJ-G7T if the larger steps don't work out. Without the L/V time this weekend, any experimenting with the larger tuning steps will probably have to wait until next weekend...

    73!
     
    KA2CZU and W5PFG like this.
  8. KA2CZU

    KA2CZU XML Subscriber QRZ Page

    The DJ-G7T is still "on sale" at HRO.

    I never pulled the trigger, but will do so in July once I get back from a vaca (since they mention it as their summer sales
    promo, hopefully the sale will continue)....
     
    Last edited: Jun 18, 2018
    WD9EWK and WE4B like this.
  9. WD9EWK

    WD9EWK Ham Member QRZ Page

    I think it came off the $229 sale price briefly a couple of months ago, but it seems HRO likes to keep it at $229. Whatever the case, it remains the only HT with 1.2 GHz currently in production, and the alternative to the 1.2 GHz modules for the larger TS-2000 and IC-9100, or the resale market for an older 1.2 GHz radio of any sort - HT, mobile radio, or base-station transceiver.

    73!
     
  10. KA2CZU

    KA2CZU XML Subscriber QRZ Page

    Been looking at the alternatives (including the FEX-736-1.2 module for my FT-736R, which is available on fleabay from time to time)
    and keep coming back to the DJ-G7T...
    been holding off as I assess how often I'm available to play satellites on Sundays.... I think I'll carve out enough time to make
    it worthwhile over the summer.
     

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