Gee, thanks for the vote of confidence Ted. I think it needs quite a bit of fluffing... but... if there is interest in such an article I would be willing to have a go at one.
Paul N1BUG On Tuesday 23 August 2005 01:13 pm, Ted Bleiman K9MDM - MDM Radio wrote: > looks to me like paul just wrote the article. little > fluffing and folding and its good to go. but,,, > thats only my opinion ...i could be wrong.. > mdm > probably need some sexy pictures to augment it... > > 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 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/
