PSAT NO84

Discussion in 'Satellite and Space Communications' started by KE3LB, Dec 24, 2016.

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  1. AD5KO

    AD5KO Ham Member QRZ Page


    I just checked on the LMR-400. For some reason I thought it was stranded, and it’s not. So it’s no good for the rotor, thanks for that info!

    I can add preamps after the duplexer at the rotor if needed. But I am more likely to stack the antennas before using preamps, if need be.

    I designed the 70cm antenna in 4NEC2, it is not phased and based on the NEC results and actual tests it’s not needed. Testing with an analyzer shows the SWR is very good, the feed point is 50 Ohms, and band width is about 4MHz. According to 4NEC2 it has a nice pattern and gain shows to be over 10dBi.

    The design of the 70cm antenna is based solely on NEC results and actual field tests.

    4NEC2 is good software, I would not attempt to design an antenna without it.

    73,

    AD5KO
     
    Last edited: Dec 29, 2016
  2. N4UFO

    N4UFO Ham Member QRZ Page

    Then you will likely have to run separate power cables to the preamps as I don't think you will be able to piggyback the DC+ to the preamps on the feedlines.


    I have never played with modelling software, so I have no idea if it can tell you if there is a circular polarity component in that design or not. But with the sats we have these days, that's fine in my opinion. I think it's more about covering both H & V and all in between. (At one time some sats HAD CP antennas; now it's more about dealing with the rotational fading.) So if that design works as good in practice as in theory and avoiding polarity fading, then you are onto something there my friend! I know that W5PFG for one, put up H & V antenna with separate feedlines (4 total, 2 UHF and 2 VHF) with switches in the shack. He flips from H to V or V to H depending on where the bird is in it's rotation. If you have a design that makes that obsolete, you should eventually write up a how to and distribute it. (Unless you want to go into the antenna manufacturing business.) :D At the very least, maybe share the details of feeding both yagis at the same time at 50 ohms.

    I'll be watching how your design plays out... please let us know, good or bad. :) or :(

    73! Kevin N4UFO
     
  3. N4UFO

    N4UFO Ham Member QRZ Page

    moving to another thread... sorry for the hi-jack.
     
  4. WD9EWK

    WD9EWK Ham Member QRZ Page

    Hi!

    Last night (Saturday, 11 February), the NO-84 digipeater on 145.825 MHz was back on. It passed by about 20 minutes after an ISS pass, a very high pass for the southwestern USA, and I was able to make a couple of quick QSOs from my back yard. Don't know how long it will stay on this time, but it is nice to have it on again.

    73!
     
  5. K3RLD

    K3RLD Well-Known Member QRZ Page

    Thanks for the update, Patrick!
     
  6. WD9EWK

    WD9EWK Ham Member QRZ Page

    Keep an eye on http://pcsat.aprs.org/ to make sure the call sign remains PSAT (digipeater on) vs. PSAT-1 (digipeater off). It's still on this morning...

    73!
     
  7. K3RLD

    K3RLD Well-Known Member QRZ Page

    Just had a 85deg pass here, didn't seem to be many (if any) live operators. I did achieve a first, however.

    I addressed a message to PSAT and received an *ACK. Later, it appears, PSAT sent me some LOS information, however I never received that one. Still pretty cool!
     
    AD5KO and WD9EWK like this.
  8. WD4ELG

    WD4ELG Ham Member QRZ Page

    Can you help me? I don't know what an ACK looks like with APRS. Is it just a repeat?
     
  9. K3RLD

    K3RLD Well-Known Member QRZ Page

    This is it. On my D710G, it just flashes up as a message from "PSAT", and all it says is "*ACK".

    [edit] Note that this will only happen if you send a message directly to "PSAT". A simple beacon isn't enough.

    [second edit] And here is the personalized LOS message it sent me, but I never received:

     
  10. WD9EWK

    WD9EWK Ham Member QRZ Page

    Hi Mark!

    An ACK is an acknowledgement of a message received by a station via APRS, sent back to the station that originated the message. It is a way of knowing that a message was delivered to the destination station. For space-borne APRS, many times these ACK packets won't make it back to the sending station, but can do so on occasion. Not all stations will request an acknowledgement of an APRS message, but all stations that are aware of APRS messaging will send an ACK whenever a message is received where an acknowledgement is requested. Almost all APRS-ready transceivers will send messages where an acknowledgement is requested. Some software, like UISS, has that as an option that can be turned on or off. Some keep it off, so the ACKs (or the attempts to send an ACK back to the station sending a message) won't clutter the channel.

    Using a screenshot from ariss.net, here is an example of a message that was sent by me (WD9EWK) to KK6OTJ-7 in California via ISS on Saturday morning, along with an acknowledgement that came back to me...

    WD9EWK_message_and_KK6OTJ7_ACK.jpg

    Reading from the bottom up, my message was sent at 13:57:17 UTC on Saturday (18 March). After the two colons and before the space and colon is the destination of the APRS message, KK6OTJ-7. The "{2" at the end of that line is a serial number for my message. These numbers are usually numeric, but can be alphanumeric depending on the radio or software used. Its presence means that an acknowledgement is requested from KK6OTJ-7 once his station receives my message.

    Other packets sent during this ISS pass would have shown our locations. In these packets with the APRS messages and acknowledgements is an identifier for the radio or software being used for APRS - APK003 is a TH-D72 (KK6OTJ uses that), and APK004 is a TH-D74 (my radio). You would see UISSxx (two digits after UISS) if the station was using the popular UISS software, and there are many other identifiers for radios or software that could be in this position in an APRS message/acknowledgement packet.

    The upper line, two seconds later, shows KK6OTJ-7 sending me an "ack2" - acknowledging the message originally sent by WD9EWK with serial number 2.

    Other packets sent during this ISS pass would have shown our locations. In these packets with the APRS messages and acknowledgements is an identifier for the radio or software being used for APRS - APK003 is a TH-D72 (KK6OTJ uses that), and APK004 is a TH-D74 (my radio). You would see UISSxx (two digits after the UISS) if the station was using a version of the popular UISS software, and there are many other identifiers for radios or software that could be in this position in an APRS message/acknowledgement packet.

    On my TH-D74, this is what the message looked like:

    WD9EWK_APRS_message_to_KK6OTJ-7.jpg


    In the blue bar at the top of the screen, there is a star to the left of the line with the message icon and the arrow pointing to KK6OTJ-7. The star indicates that my radio received the ACK from KK6OTJ-7, and the arrow to KK6OTJ-7 shows this was an outgoing message to that call sign. If the arrow was pointing to the left away from the call sign, that means the message was received from that call sign, and there wouldn't be a star to the left of the message icon (my radio wouldn't know if the sender of a message successfully received the ACK from me).

    Hope that helps explain the ACKs and how they factor in APRS messaging. 73!
     

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