Trying to get answers on Full duplex HT for satellite

Discussion in 'Satellite and Space Communications' started by KE7GVK, Jun 25, 2015.

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  1. KE7GVK

    KE7GVK Ham Member QRZ Page

    I've recently become rather interested in working satellites, however I don't have a xcvr that will work full duplex (in case I've messed up the definition - I mean that you can tx on vhf and rx on uhf simultaneously).

    I'm looking for opinions on current production models of HT xcvr's. I'm looking at the following - however can't tell, nor can I find much, on whether or not these are devices capable of what I'm looking for.

    Yeasu VX-8DR
    Yeasu FT1DR
    Kenwood TH-F6A

    I'm foregoing ICOM as the only one they've got at the moment that looks like it would work is waaayyy out of my price range. I'm looking for sub $400 new. I'm also open to recommendations, but I would prefer reference to current devices, not something that worked well 10 years ago and is impossible to find (the W32A for example). If I can avoid it - I don't want to have separate devices to tx and

    73
    KE7GVK
     
  2. N8HM

    N8HM Premium Subscriber QRZ Page

    None of those can. The Kenwood TH-D72 is the only current production model that will do it and do it well enough for satellite work.
     
    N1EMH likes this.
  3. KE7GVK

    KE7GVK Ham Member QRZ Page

    great....that's discouraging. What do people use for satellite work then...?
     
  4. N1EN

    N1EN Premium Subscriber QRZ Page

    For SO-50: Two HTs

    A couple of the Chinese HTs are capable of operating full duplex, but they have desense issues on UHF, precluding full duplex on SO-50. One or two models might be fine for the Fox-1 satellites.
     
    K9EI likes this.
  5. WD9EWK

    WD9EWK Ham Member QRZ Page

    Lots of options...

    You can look for the old, out of production, HTs that do full-duplex. This includes the IC-W32A you mentioned, along with others like the IC-W2A, IC-W31A, IC-Z1A, FT-470, FT-530, TH-78, TH-79, TH-D7, and there were some from Alinco that also worked full-duplex like the DJ-G5 (definitely NOT the current DJ-G7T).

    You can use any HT you have, and add another HT to have a full-duplex station. An option for a second radio could be one of the inexpensive Chinese-made HTs. With an antenna like an Arrow Yagi, you'd connect each radio to a feedpoint, bypassing any duplexer. You'd need a duplexer if you use a log periodic antenna like an Elk, which has only one feedpoint.

    Many on SO-50 are not working it full-duplex. They can use a variety of radios programmed with a group of memory channels that deal with the Doppler effect on the 70cm downlink. The preferred way to work satellites - FM, SSB, or CW - is to go full-duplex as you are looking to do, and that's a good thing.

    If you were looking at mobile transceivers, there are more options for full-duplex operation. Kenwood's TM-D710GA and TM-V71A, at least a couple of Yaesus (FT-8800 and FT-8900 - I haven't looked at the newer FTM-numbered models), Icom's IC-2730A (haven't tried the ID-5100 yet). Many more that are out of production also do full-duplex operating.

    What radio(s) do you already have?

    73!
     
  6. KE7GVK

    KE7GVK Ham Member QRZ Page

    Help me to understand the purpose of having a full duplex HT then - Is this just to hear yourself hitting the bird on the downlink? Is this necessary to confirm you're hitting it? Or could I just use any dual band HT to get to the uplink and hear the downlink on the same device?...
     
  7. WD9EWK

    WD9EWK Ham Member QRZ Page

    A radio - or two radios - that allow you to work full-duplex lets you know you are making it through the satellite, without relying on other stations answering you. It is not mandatory, but full-duplex operation is encouraged for this reason. There are times you could be missing the satellite, and wouldn't know it for sure, if you weren't able to monitor the satellite's downlink while transmitting.

    Many dual-band HTs can be programmed with a group of memory channels to work SO-50, with one channel to activate the 10-minute timer (transmit on 145.850 MHz with 74.4 Hz tone), then other channels where you would talk through the satellite. You can see this setup in a PDF document offered by AMSAT:

    http://www.amsat.org/wordpress/wp-content/uploads/2014/01/Work_FM_Sats-20131010.pdf

    (look at the last page of this PDF for the frequencies for each of the memory channels)

    Most Icom dual-band HTs made since the IC-W32A was discontinued are not capable of having memory channels programmed in this manner. You end up jumping between VFOs, or between memory channels and a VFO, every time you go from receive to transmit and back. I have an ID-51A, which has a nice receiver to copy the SO-50 downlink. It is not a good radio to work SO-50, since you have to jump around between the VFOs. I have used this radio with a second HT, so I could work the satellite full-duplex (most of the time, the ID-51A is my receiver when working SO-50, and the other radio would be the transmitter).

    Hope that helps. 73!
     
    Last edited: Jun 26, 2015
  8. WD9EWK

    WD9EWK Ham Member QRZ Page

    I tested my Wouxun KG-UV8D against an engineering model of the Fox-1A satellite, at the ARRL Centennial Convention in Hartford and the AMSAT Symposium in Baltimore during 2014. I would transmit on 435.180 MHz, and listen on 145.980 MHz. The engineering model had a very poor antenna, effectively a dummy load. I used low power on the HT, and a small duckie antenna. I wanted to try and make the signals be similar to those I'd hear from a satellite. The KG-UV8D is no good for full-duplex operation on SO-50, but worked very well with the Fox-1A engineering model. I received good signal reports from other hams who were listening to my transmissions through the Fox-1A engineering model.

    The AnyTone TERMN-8R radio, which had been on sale earlier this year, is another example of Chinese-made dual-band HT that is no good for working SO-50 full-duplex, but should work fine for Fox-1A and the other Fox-1 FM satellites with 70cm uplinks and 2m downlinks. I found the TERMN-8R's receiver to be slightly better than the KG-UV8D's receiver when working SO-50, but I have not had a chance to test the TERMN-8R against a Fox-1 model.

    I am holding onto both of these HTs, waiting for the Fox-1A launch later this year. Once Fox-1A is operational, I intend on using these radios, and many other radios (and combinations of radios) to work the satellite.

    73!
     
    Last edited: Jun 26, 2015
  9. KE7GVK

    KE7GVK Ham Member QRZ Page

    I've got a Baofeng UV5R and an IC-2200H mobile rig. Do these little Chinese radios work well for satellite RX? I'd find something else for TX....a new toy... :)

    I'm looking at getting an Arrow yagi as well - mostly because I don't know what other commercial options are available that are set up for satellite work (dual feed lines). A different beast entirely - but are you aware of any other portable (handheld seems like a good option? - like the arrow) commercial options for an antenna?
     
  10. WD9EWK

    WD9EWK Ham Member QRZ Page

    You could go with the IC-2200H as the transmit radio (try the low power setting on this radio), and receive with the UV-5R. You'll want to set the UV-5R to tune in the smallest steps it can handle, 2.5 kHz. Its receiver has front-end filtering that is a little sharper than what we normally have with the Icom/Kenwood/Yaesu amateur HTs. Keep in mind that there are HTs with better receivers than what you get in the UV-5R, and that you could see differences in performance between two UV-5Rs. Quality control on the Baofeng assembly line isn't what it should be, but they can work for SO-50 and the upcoming Fox-1 FM satellites.

    If you get another dual-band HT made by the traditional ham manufacturers (Icom, Kenwood, Yaesu), you'd probably want to use that HT as a receiver, and transmit with the UV-5R you already have. Any of the 3 HTs you listed in the first message of this thread would be good options for a second HT. The TH-F6A would also give you the opportunity to receive the downlinks from the SSB/CW satellites (AO-7, FO-29, AO-73), as it has an all-mode receiver. The two Yaesu HTs have APRS capabilities, and you could use that to send signals through the ISS digipeater, even make contacts using APRS messages with other stations as the ISS passes by.

    For a dual-band Yagi that can be used for satellite operating, the Arrow is probably the best choice for a commercially-made antenna. If you pull back the handlegrip, you'll see the holes where the antenna could be mounted on a camera tripod.

    You might also consider a homebrew antenna. A good example of a design for a dual-band Yagi comes from Kent Britain WA5VJB, in his PDF document:

    http://www.wa5vjb.com/references/Cheap Antennas-LEOs.pdf

    Have you looked over the useful information for satellite station and operating hints on the AMSAT web site:

    http://www.amsat.org/?page_id=2144

    73!
     

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