You can build an analog simulcast system on a budget, but you may not be satisfied with the audio quality results.? Using the same brand equipment throughout the system (including RF links) is not mandatory, but it does simplify the process of making the audio sound acceptable.? (Notice the wording "acceptable")
In the budget system you definitely would need to a disciplined oscillator to keep each site on frequency.? But, you do not want both sites on exactly the same frequency.? If both sites are exactly on the same frequency you can experience deep phasing nulls where the two sites cancel each other out.?? Instead, you can offset the two sites by, for example, 20 Hz.? This will cause a 20Hz buzz on the signal, but the low frequency filter in the receivers that filter off Pl tone should minimize the buzz.? This technique was used on a public safety system and documented in a publication many years ago. (Can't remember the name of the publication right now.)
Again, this is the cheap and dirty way of doing simulcast.? Audio quality WILL suffer, but it will give communications quality analog audio.? I did something similar on a large Quintron paging system years ago that did both voice and digital paging.? It worked surprisingly well and the tiny speaker on the voice pagers filtered out the offset buzz.? We used crystal ovens to keep the system on frequency.? Crystal ovens will keep the transmitters on frequency but not in phase like a GPS system can do.
Joe
