Paul, Thank you very much for the very enlighting information, it gives me a place to start. I plan on trying to get the hardware/software working here at my house. If I'm sucessful I will try to coordinate a frequency pair through the local club. If all that works I'll start looking for an elevated site, since I'm in western washington It shouldn't be to hard to find a place that is fairly quiet. Again thanks for the Information.
Scott N7ANY --- In [email protected], Paul Kelley <[EMAIL PROTECTED]> wrote: > I haven't seen any replies to this yet so I'll take a stab > at explaining the basics. (Hey guys, this sort of thing is > a FAQ, obviously... maybe we need a good basic "Repeater > Building 101" article for RBTIP? If there is one, I > haven't found it. I am aware of the "What's a Repeater" > article but that seems to be aimed more at repeater USERS > and is a bit too basic for the novice builder, IMHO. Just > curious / asking....) > > Scott, I gather you are thinking of using both radios... one > as a receiver and one as a transmitter. That will work, > but with those radios I think another option is to use just > one of them. Take out the receiver and transmitter, mount > them in two separate metal boxes (for shielding). > Preferably all wires coming out of each box would by via > feedthrough capacitors to filter any stray RF (except the > coax of course). I will leave it at that since I have not > built a repeater from those rigs myself. > > You will probably want to add a tone decoder to the > receiver. I know I'll open a can of worms with this, but I > pretty much subscribe to the belief that most, if not all > repeaters these days should use tone access... not just > carrier squelch. There's just soooooo much RF out > there.... in and out of band. > > You will need a repeater controller. This could be very > basic, providing ID, timeout timer, and of course keying > the transmitter whenever the receiver goes active. Or it > could have many other features like fancy courtesy beeps, > voice ID, DTMF control of repeater functions, etc. etc. I > would suggest you check out the repeater controller > suppliers listed on this page to see what they have to > offer. That may give you a better idea what you want... > > http://www.repeater-builder.com/rbtip/supplyindex.html > > The controller, at its most basic level, takes audio and > carrier / tone detect from the receiver and supplies audio > and PTT to the transmitter as needed. > > If you want to run on a single antenna (repeater transmits > and receives on the same antenna) you will need a duplexer. > This is an expensive component. Its function is to block > the transmitter carrier from entering the receiver and > either damaging it or overloading it so that it can't hear > what it is supposed to be hearing... and also to keep noise > generated by the transmitter (which spreads out around the > carrier and some of it will fall on the repeater receive > frequency) from degrading receive performance. > > If you have enough space you can run on two antennas without > a duplexer. Since I haven't built a 222 repeater this is a > guess, but I'll take a stab in the dark and say perhaps 50 > feet of vertical separation between antennas or 200 feet > horizontal separation. Perhaps someone with 222 experience > will offer to correct me on this. Vertical separation is > more effective because most repeater / base station > antennas are designed to radiate best toward the horizon > and have nulls in the up / down directions. Vertically > spaced antennas are mounted in each other's null, thus > increasing isolation between them... whereas horizontally > spaced antennas are in each other's maximum radiation lobe. > One difficulty with two antennas is trying to match receive > and transmit coverage... especially if one antenna is > mounted above the tower and one is side mounted. > > Antennas can be chosen to suit your requirements (where do > you have to mount them and what coverage do you need?) but > there are a few things to watch out for. It is desirable > to use an antenna that is rugged enough to survive > conditions at your repeater site. Wind and ice factors > vary with location, tower height, height of hill / > mountain, etc. Also be aware that some "ham grade" > antennas may be noisy in duplex service (single antenna > repeater). > > All interconnecting cables on the repeater should be good > quality double shielded cable. I like RG-214 but RG-400 is > suitable for short runs to interconnect receiver, > transmitter, duplexer, etc. The feedline run to the > antenna(s) can be RG-214 if it is very short, otherwise > hardline. > > It is important (especially for the single antenna repeater) > that all connections and hardware in and around the antenna > / tower be tight and not able to move... also free of rust. > Loose parts or rusty hardware can cause noise that your > duplexer will not be able to keep out of the receiver. > > Where do you plan to put the repeater? If at a managed site > with other repeaters / communications, there may be > specific technical requirements you have to meet in order > to be allowed at the site. Some of them may require > additional equipment not mentioned here (for example an > isolator). > > What did I forget to mention? Of course there are many fine > points I didn't attempt to cover here. > > Paul, N1BUG > > > On Sunday 21 August 2005 02:46 am, n7any_1 wrote: > > I'm new to building repeaters, I have had a cobra 200 > > since they came out and used it as mobil rig, I have > > aquired a midland 13-509 and would like to build a 222 > > mhz repeater out of them. Since I know almost nothing of > > the details of building a repeater any information would > > be welcome. I am especially interested in a description > > of the main parts of a simple repeater ie. radios > > controllers, antennas, duplexers, whatever I will need to > > put this together. I am also interested any experiences > > others have had building a repeater from these rigs? > > Thanks > > Scott Frazier > > N7ANY Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
