Best RF modulation for dynamic environments?

Discussion in 'Ham Radio Discussions' started by KE7RUX, Mar 25, 2020.

ad: L-HROutlet
ad: l-rl
ad: Left-2
ad: abrind-2
ad: Subscribe
ad: Left-3
ad: L-MFJ
  1. KE7RUX

    KE7RUX Ham Member QRZ Page

    What would you consider the best RF modulation for dynamic environments?

    If there was one "King of the Hill" modulation you had to pick, what would it be?

    This is without the use of repeaters, and for voice simplex use, and it doesn't have to be your typical ham modulation.
    (Let's assume that variables such as the proper equipment and antennas are automatically employed so we don't have the need to discuss that.:rolleyes:)

    If you'd like to pitch in what frequency band you would suggest, that's fine, but I'm not looking nor asking for such in this post. I will be posing that question in a separate post here:

    I live in a peculiar environment, where the city center (where I currently work and reside) has buildings about a 1^2mi on a hill, then just outside of the city center it transitions small buildings for 1-3^2 mi on a flatter terrain, followed by endless miles of farmland.

    I have tree points of contact:
    1. Inside the heart of the city center through endless floors and buildings
    2. City center to city limits approx. 3 mi out
    3. City center to 15 mi out

    Extra details: DMR is great...sort of. It works great with near to mid distance communication without obstructions. Sometimes through 2 buildings (on relatively the same floor level) there are too many obstructions and it cuts out. FM has similar results, with Digital having a better mid range and NO weak signal. Essentially I wish there was a voice modulation with the quality that could also weak signal like SSB. Too good to be true? Perhaps simply increasing the power is the answer?
    Last edited: Mar 25, 2020
  2. WZ7U

    WZ7U Ham Member QRZ Page

    CW. :p
    KY5U, K7KBN, KA4DPO and 1 other person like this.
  3. W1VT

    W1VT Ham Member QRZ Page

    Properly adjusted SSB.
    NL7W and WA9SVD like this.
  4. K7TRF

    K7TRF Premium Subscriber QRZ Page

    If you open it up to modulation and coding not typically used in ham applications I'd go with a QPSK/QAM scheme with link adaptive coding and modulation based on a feedback metric like CQI(Channel Quality Indicator) used in the 3G, 4G and 5G wireless systems. Add adaptive retry mechanisms such as HARQ(Hybrid Automatic Repeat Request) and the links are even more robust.

    Basically in a link adaptive system (aka Adaptive Coding and Modulation or ACM) both the modulation (e.g. QPSK, 16QAM, 64QAM, etc.) and the error correction coding are varied based on the quality of the communications link. If you've got a great signal and low interference you send a lot of data in each transmission using a high modulation rate and relatively low error protection coding. As the communication link degrades you lower the information rate via lower modulation index and or higher error correction coding. Adding mechanisms like HARQ resends part or all of the missed messages when messages are received with data errors which requires additional feedback messaging.

    Link adaptation is commercially used in wideband systems whether spread spectrum or OFDM but the same concepts can be applied to narrow band systems like we use on the ham bands.
    Last edited: Mar 25, 2020
    AE8W likes this.
  5. KE7RUX

    KE7RUX Ham Member QRZ Page

    Could you expand upon "Properly adjusted"?
    KA4DPO likes this.
  6. K1VSK

    K1VSK Ham Member QRZ Page

    My biggest problem is finding my microphone - I put it in a ‘safe place’ and now I can’t find it.

    (Actually, I haven’t looked).
    KY5U and W4NNF like this.
  7. W1VT

    W1VT Ham Member QRZ Page

    I'd have friend listen to you and confirm that it sounds good and doesn't splatter across the band. It is easy to have so much distortion on SSB that intelligibility is affected.
  8. W4NNF

    W4NNF XML Subscriber QRZ Page

    Everything considered... CW is still king. :)
    AE8W likes this.
  9. N3PM

    N3PM Ham Member QRZ Page

    CW on 40 or 80 would fit your distances and terrain.
    Something that the parties you're trying to contact can employ as well may be a consideration.
    Mike N3PM
    I take that back. Looks like CW is out. a thousand pardons.
    KA4DPO likes this.
  10. KA4DPO

    KA4DPO Platinum Subscriber Platinum Subscriber QRZ Page

    Turn all of the knobs on your radio as far to the right as you can.:D
    WA1GXC and KE7RUX like this.

Share This Page