SSB Repeater?

Discussion in 'Ham Radio Discussions' started by KE7RUX, Nov 2, 2017.

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

    KE7RUX Ham Member QRZ Page

    Theoretically, how effective would a Single Sideband repeater be? Pros and Cons? What components would be best for the job? How many watts would be a good repeater output on SSB? Please leave your genius THEORETICAL no nonsense comments! :)
  2. AG6QR

    AG6QR Premium Subscriber QRZ Page

    SSB has no carrier, so there's no carrier to detect, and no way to easily determine when the repeater should start and stop transmitting, the way a typical FM repeater does.

    A linear transponder, such as is used on some satellites, can handle SSB. It continuously receives and transmits 100% of the time, thus avoiding the issue around determining when it should turn itself on and off. A transponder may repeat a wide swath of frequencies, allowing it to carry many independent conversations at once.

    How much power is appropriate? Enough to reach the receiver, I guess. Note that a wide-bandwidth transponder will spread its power out over a wide swath of frequencies, and may therefore require more power than a transmitter that carried only a single SSB signal.
    K0UO, N4GKS and WZ7U like this.
  3. WZ7U

    WZ7U Ham Member QRZ Page

    There is such a thing as a simplex repeater, but for all I know it is an FM only device.
  4. W6RZ

    W6RZ Premium Subscriber QRZ Page

    The correct terminology is linear translator. On 2 meters, there's even an allocation in the band plan at 144.5 to 144.6 MHz for inputs and 145.1 to 145.2 MHz for outputs.

    Linear translators pose some technical issues. You need a very high dynamic range receiver and a very effective AGC on the transmitter. Also, you need a very low noise site. As AG6QR states, the translator continuously receives and transmits 100% of the time. If your site is noisy, then that noise gets re-transmitted and the output frequency sounds like a jammer.
    AG5DB, K0UO, NL7W and 2 others like this.
  5. G0GSR

    G0GSR Ham Member QRZ Page

    We did this as an experiment on 2m in the 1970's!
    25kHz wide linear transponder. A few Watts output on a high site.
    Suffered badly from the "strong signal effect" which reduced the gain for other weaker signals.
    Worked OK otherwise but was not exactly legal...
    KA4DPO and AG1W like this.
  6. KT1F

    KT1F Ham Member QRZ Page

    I guess the distinction between a linear transponder and "real" repeater is quite blurry. I was thinking of a real SSB repeater with transmitter and receiver connected via audio. I guess you could simply leave it "on" all the time. But then that would essentially be a narrow bandwidth linear transponder. You could have multiple PSK-31 or similar mode QSOs going on at the same time.

    It would be fun to setup a cross band system as an experiment. I'm not sure how useful it would be or how well it would work.
    Last edited: Nov 2, 2017
  7. KK4YWN

    KK4YWN Ham Member QRZ Page

    I was thinking about building one using an sdr chip to convert to baseband, digitize and filter, convert back to analogue, and upconvert with one of the SDR modulators. I wanted to see if its possible to code agc loops that are freq-dependent. Suppose there is 20khz of bandwidth being translated: divide that 20kz into four 5khz slots and brickwall filter them. then build the agc loops to operate independently within the filters.

    as long as you can keep the lids off it the old problems with linear translators should be minimized.
    K6LPM likes this.
  8. N3HGB

    N3HGB Ham Member QRZ Page

    Why would you build this thing? For 2 meter SSB? Repeating HF seems kind of silly. I never really got 10 meter FM repeaters either, if I could get into a distant repeater on 29 MHz, I could also reach the people at that end directly.
    N2EY likes this.
  9. K9STH

    K9STH Platinum Subscriber Volunteer Moderator Platinum Subscriber QRZ Page

    It is definitely possible to build an SSB repeater. There have been ACSB (amplitude companded side band) repeaters for decades.

    However, to insure frequency stability, a very low power "pilot carrier" is transmitted, outside of the "normal" signal and an AFC (automatic frequency control) circuit "locks onto" that signal to make sure that the receiver is always tuned to the transmitted signal.

    AFC circuits have been around since at least World War II and were incorporated in FM broadcast receivers since that time. For years, there was a switch, on a good number of FM receivers, that allowed the AFC to be turned on or not activated.

    Glen, K9STH
    NL7W and AB2YC like this.
  10. W4NNF

    W4NNF XML Subscriber QRZ Page

    It's not a question of technology; it's a question of "why?"
    K7KBN and N2EY like this.

Share This Page