I'm reactivating this old thread because of the last Flex Radio Friends TeamSpeak session.
Phil, VK6APH mentioned his experience with phasing two SoftRock 40s running on the same clock. He said that the phase was rapidly changing, even with the short distance between his antennae. Perhaps some sort of adaptive scheme will be needed. A couple of ways for optical telescopes to compensate for atmospheric turbulence is to use a bright, nearby star for reference or to transmit a laser beam upwards where a nearby star is not available. How do radio astronomers compensate for ionospheric fluctuations? Surely that must be an issue for the Very Large Array (VLA) in New Mexico and the Very Long Baseline Array (VLBA). Do they use statistical methods? Or is it sufficiently transparent at the observing wavelengths? Mike - AA8K Jim Lux wrote: > At 01:19 PM 6/16/2006, Nicholas Bastin wrote: >> On 6/16/06, Mike Naruta <[EMAIL PROTECTED]> wrote: >> > We could also link the transmitters to be >> > sure to get through the pile-up. At least >> > for the initial call. Then when he comes >> > back to you, you can use just your own >> > transmitter. Getting all the transmitters >> > on the same Hertz is easy. You would need >> > to measure network delay and compensate in >> > order for the voice/dits to be in unison. >> >> You would have to sync to GPS. You can't accurately measure network >> delay and compensate, because congestion and network delay are >> dynamic. Even then it would be odd, because you'd have to introduce >> delay to allow for all the stations to receive the source signal >> before transmitting (basically turning your radio into a >> store-and-foward device like a network switch). All this assuming >> that it isn't illegal, which I'm sure it is, at least in some >> countries. > > > You'd also need to compensate for the (varying) delay in the propagation > path from the intended receiver. One *might* be able to approximate it > by listening to the call from the intended receiver, but that would > require you to communicate with all the transmitters. That is, all the > stations would record the time they received the QRZ?. Then, you'd > calculate a reference time that it must have been transmitted by the > caller (which doesn't necessarily have to be the exact time it > occurred). Then, you'd all agree on when you wanted the signal to arrive > at the receiver, back up by your propagation delay, and then send at > that time. The propagation delay isn't particularly stable, but then, > it's not unstable either. It can be well represented as a FM with a > deviation of a few Hz. There's some data from folks doing the ARRL > Frequency Measurement Test (FMT) you can look at for examples. > > In any event, you'd definitely have a phase control issue. You might be > better off all transmitting at a slightly different carrier frequency, > and trying to synchronize the modulation. Say, each of the remote > stations transmits at spacings of, say, 20-30 Hz, all transmitting the > same thing. That would be pretty noticeable to the receiver<grin>. > > > Jim > > > _______________________________________________ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://www.mail-archive.com/flexradio%40flex-radio.biz/ FlexRadio Knowledge Base: http://kb.flex-radio.com/ FlexRadio Homepage: http://www.flex-radio.com/
