What can JT65 do that PSK31 can't do? What can JT9 do that JT65 can't do?

Discussion in 'Working Different Modes' started by KC0BUS, Oct 14, 2016.

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  1. KJ4VTH

    KJ4VTH Ham Member QRZ Page

    Joe Taylor is wrong. :D

    JT65 is a great mode for HF. I'm working stations right now on 80m.
     
  2. KV6O

    KV6O Premium Subscriber QRZ Page

    The answer to both questions is get thru when the other one can't. The minimum SNR for RTTY is about +5 dB at 2.5kHz BW, and about -7dB for PSK-31 at 2.5 kHz BW, and about -24dB for JT65. So, you need a 100W PSK signal to have the same "punch" as a 2W JT65 signal - all things being equal. Or an 8KW RTTY signal to equal a 10W JT65.

    This allows small gun stations to make contacts with places previously unreachable. There is a price for this, reduced bit rate (slow data transfer) and compute power needed for the decoder.

    They are truly amazing - thanks Joe!

    Steve
    KV6O
     
  3. W0BTU

    W0BTU Ham Member QRZ Page

    Sure it is. I'm not debating that. But it shouldn't be that way!

    That's why that portion of the bands get so jammed with signals. JT9 has a 2 dB advantage below 20 meters while using only 1/10 of the bandwidth of a JT65 signal. Translation: you can fit 10 JT9 signals in the bandwidth of one JT65 signal. Those are just facts.
     
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  4. W9FTV

    W9FTV XML Subscriber QRZ Page

    Yep, and it's a fact that JT-65 is far more popular than JT-9 on HF.
    Why? I've no idea, but I'm not going to argue with success.
     
    Last edited: Oct 15, 2016
    K8KJG and W0BTU like this.
  5. KC4YLV

    KC4YLV Ham Member QRZ Page

    I think it's just that people think the 'doodly waterfall thing' is neater than the 'sounds like a carrier' thing
     
    K8KJG likes this.
  6. N0IU

    N0IU Ham Member QRZ Page

    The "JT" modes release you from the possibility that someone may actually want to talk to you!
     
  7. K8KJG

    K8KJG Premium Subscriber QRZ Page

    This is in no way meant to be a derogatory answer to anyone on this thread. Nor is it meant to be a lecture of any kind towards anyone.

    This is strictly my perspective on the present state of the digital HF QRP operations that I have really grown to enjoy in the recent past. It is meant for those who may not be familiar with the fun of using digital signals, whether you are operating from home, a mountain summit, a beach, a national park, etc.

    It allows us to use really simple low power technology to do some very interesting things - like knowing where our signals are being heard. I can run WSPR with an extremely simple $20 Raspberry Pi computer hooked to a non-resonant piece of wire. All of WSPR operation per HF band doesn't take up much more space than a single CW signal per band. Yet, with a 15 year old laptop, running a LINUX operating system, I can quickly determine where my signals are being heard.

    The JT modes, particularly JT-65 and JT-9 allow some incredible signal confirmations around the world, using QRP and very little bandwidth. That JT-65 is more popular than JT-9 is just one of those things that has no real rational explanation. For those of us in my age category, it has the same explanation of why VHS beat out BETA, which was a superior system?

    As I mentioned in the first answer in this thread, it is not even real obvious using WSJT-X if a CQ is JT-65 or JT-9 as you prepare to answer the CQ -- unless your brain is a lot faster than mine. You only have a few seconds to decide which of the decoded signals you want to respond to. If like me, you are going for things like 40 meter QRP DXCC from a crazy location, you don't have much time to decide if it is a DXCC country you might need, PLUS, you need to quickly decide if it is of sufficient signal strength so that you might have a chance of working it with your QRP station and minimal antenna, etc.

    If we look at the HF band plans for all of JT-65 plus all of JT-9 per band, they take up just a little more than one single modern SSB voice signal per band. That's pretty darn impressive -- that also represents dozens of signals.

    Much of the same can be said of PSK31 and PSK63. It takes minimal bandwidth. It takes minimal power. It takes minimal equipment. It just takes enthusiasm. None are right or wrong. But, as our bands get more crowded, these characteristics become more important.

    Please, lets not turn this into a mode vs. mode argument while lambasting each other. We all have our likes and dislikes. Yes, I love my low power digital modes, but come this winter, I hope you will be hearing me on HF AM again after many years.

    Regards,
    Ken
    K8KJG
     
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  8. W0BTU

    W0BTU Ham Member QRZ Page

    I believe the reason is, that JT65 got real popular (somehow; maybe has to do with the JT65-HF software fork?), but the word just hasn't got out about JT9.

    You have spoken well. Your point is well taken.
    If my pro-JT9/anti-JT65 posts sounded like I was angry, flaming, etc. I certainly didn't mean it that way! My apologies, gentlemen.

    When I see a post like this, I sometimes reply with the facts I mentioned, to help get the word out about JT9. And that's the only reason I said what I did. :)

    After the word gets out about JT9 (if it ever does), then those places on the bands will get a WHOLE lot less crowded!! Let me say it again:

    JT9 has a 2 dB advantage below 20 meters while using only 1/10 of the bandwidth of a JT65 signal.

    Translation: you can fit 10 JT9 signals in the bandwidth of one JT65 signal.
     
    Last edited: Oct 16, 2016
    W9FTV and K8KJG like this.
  9. SV2EVS

    SV2EVS Ham Member QRZ Page

    with jt65, you can work a dx with low power and a low cost antenna...with bpsk31, you have a less more change for that...jt65 i believe has a maximum of 30w output, that what it says on the web
     
  10. KJ4VTH

    KJ4VTH Ham Member QRZ Page

    Sounds reasonable.
     

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