Repeater Power output being a function of RSSI...Have another think on this one ... What about all the other mobiles or handhelds that could be in fringe or poor coverage areas, what will happen to their repeater reception if suddenly the repeater power is suddenly dropped at the expense of a high powered mobile. This feature is sometimes utilised on the Portables or mobiles if the system is relatively balanced (5W repeater, 5W portables)... But never on the repeater for above reasons.This feature is good at saving battery life for the portables, but the repeater should be specified for this anyway.
The best repeaters are simple, and simple to use This is how I tackled the portable repeater problem for our emergency services: http://www.signals.net.nz/contributed/documents/VXP-820brochure.pdf Just my 10c worth. Regards to all Gareth Bennett ----- Original Message ----- From: vhsproducts To: Repeater-Builder@yahoogroups.com Sent: Wednesday, August 05, 2009 5:08 PM Subject: [Repeater-Builder] Re: Portable repeater Thanks for all the great input! I agree that it would be a lot easier to manage a portable repeater as a UHF station,or UHF/VHF cross band, but the VHF mode is a hard and fast requirement of my clients that want a truly portable repeater. Just to clarify a couple of points, I won't be converting commercial or ham radios to fit inside an ammo can with an off-the-shelf controller. This is pretty much a ground-up project, and we will build the whole unit including the RF sections and the controller. I especially like the idea of power output being a function of the RSSI-very intriguing! Power is clearly going to be a problem, and rechargeable batteries, while economical, are not so wonderful on power to weight ratios. In my first generation digipeater, I had a 10 Watt transceiver in a package about the size of a handheld radio (A pelican 1030 case) including a pack of 8 AA alkaline batteries. It had a service life of about 24 hours. Of course, the operational intervals are much different than voice repeaters; a typical transmission is about 300 ms long, but they happen very frequently, about once every three seconds on the average. I will plan on making the enclosure ( almost certainly a Pelican Case of some variety) based on having a planned field battery life of at least 24 hours, with an auxiliary input for a piggy backed power supply. Experimenting with a 300 mW repeater, I found that I could have six inches of antenna separation with a 600 KHz split, but the antennas had virtualy no gain, and not too many people are going to want a 1/3 Watt repeater! ( yes, I know that having antennas within 6 inches is not a good thing, but my bench is to small to really separate them!) Considering that I am going to have to have a bit of antenna separation, I am also thinking about having the transmitter and amplifier in a separately powered module, and having the receiver and controller in the main case, along with batteries. This will keep me from having to carry massive quantities of heavy coax cable: the control cable between the units just needs to be heavy enough to resist damage. Things I have absolutely ruled out are having a duplexor (denies us frequency agility) Marine deep cycle batteries ( you need a forklift to deliver them!) and ammo cans, steel cases, or other stuff to heavy to walk up a hill with. More gee-whiz ideas are being able to remotely turn the unit into a simplex repeater ( although I truly hate them) and be able to monitor the talk frequency for APRS and ax.25 packets, and shoot them out over the APRS network channel. My design goal is to go as small and light as possible with a 24 hour service life, and robust enough to survive field deployment. Like all designers, I have to kick myself occasionally to prevent myself from over-complicating what should be a very simple tool. If I can make it work, I would very much like to work on a next-gen unit with a few more bells and whistles, but still cheap enough to fit into a hans budget, and not requiring a team of sherpas to carry around. once again, thanks for all your great ideas! Allen AF60F www.byonics.com
