Davis wireless repeaters can be invaluable for transmitting weather data over longer distances than the ~250m maximum hop-length that direct ISS-to-console transmission can support. Communication of data from ISS to console is possible over distances of up to a few miles with a suitable multi-repeater configuration and where line of sight allows. Repeaters can be used with both Davis VP2 and Vue stations (which use an identical wireless protocol), but there is no support for the older Vantage Pro (VP1) models.
Originally, Davis marketed four distinct repeater models for the VP2 range: standard and long-range (LR) in both AC-powered (7626 and 7653) and solar-powered (7627 and 7654) versions. The AC-powered types had no solar panel on the doors while solar versions use the standard Davis design of solar panel / supercapacitor / backup CR123 lithium battery.
But by 2015 the two AC-powered versions had been discontinued. In practice, it is possible to AC-power the solar-powered models by connecting a standard Davis 6625 5V mains adapter to the small jack that will be found on the repeater circuit board and this is a configuration that should work perfectly well. Given the relatively limited sales of the 6726/7653 AC parts and the ease of powering 7627 and 7654 from AC mains, Davis presumably felt that continuing to offer 7626 and 7653 separately was unnecessary duplication.
The circuit boards on standard and LR repeaters seem to be essentially identical other than one key difference: The standard 7627 repeater has the familiar fixed whip (or dipole as Davis term it) antenna with both receive and retransmit functions being handled by this single antenna. But on the LR 7654 model the antenna connections on the PCBA are taken to two separate connectors to allow connection to separate external receive and retransmit antennas. The greater potential range of the LR version appears to derive totally from the ability to connect antennas with much higher gain than the standard whip provides.
But there’s no doubt that introducing repeaters into the configuration can also make it more tricky to troubleshoot apparent reception problems and for this reason it’s always prudent not to use more repeaters than necessary in a repeater chain to carry the signal over longer distances. So if one repeater will do the job adequately then stick with one repeater. If the distances or topography are such that two standard 7627 repeaters seem likely to be needed then consider using one 7654 long-range (LR) repeater instead – the cost will be much the same overall and the configuration is likely to be simpler to troubleshoot if there are any problems and also more reliable.
Davis have published an Application Note (No 25) that provides a lot of additional detail about configuring repeater systems and that may well answer many initial support questions – see:
To be added