RE: [Repeater-Builder] Re: Yet Another split antenna Question
We have a VHF TV station on top at 1500' and until recently had an FM broadcast station at 1200'. We had to run a notch filter tuned to the FM station to keep it out of the receiver. Of course in recent years they added a big UHF slot antenna on the side of the tower for HDTV. We had to move our top antenna down to just above the FM antenna to get out of the way of the UHF antenna. That move cost us about $5k for the climb. We haven't been able to decide if the loss in height was offset by the reduction in feedline loss but it seems pretty close. John Lock kf0m at arrl.net > -Original Message- > From: Repeater-Builder@yahoogroups.com > [mailto:repeater-buil...@yahoogroups.com]on Behalf Of skipp025 > Sent: Friday, December 19, 2008 11:43 AM > To: Repeater-Builder@yahoogroups.com > Subject: [Repeater-Builder] Re: Yet Another split antenna Question > > > Hi John, > > Very Nice... > > You didn't indicate how much and what type of broadcast is > also on the tower? > > One of the saving grace items in your system is the quality of > the Master II Receiver and it's well designed front end. > > cheers, > s. > > > > "kf0m" wrote: > > We were at 1400 ft and 1100 ft for a while with the repeater > > on the tower running 40 watts TX. That separation was OK for > > the Tx and Rx isolation. We ran one can on the RX. an HT > > could be full quieting at 50 miles from the repeater. > > > > The repeater was a Mstr II inside a surplus traffic light > > controller box. > > > > Unfortunately we lost access to the elevator and so we brought the > repeater > > to the bottom of the tower because of the climbing costs. Takes a > lot more > > watts and a good preamp and still doesn't equal the range > performance but it > > is a lot easier to work on especially in cold weather. > > > > With the repeater in the air, everything needs to be super rugged > with as > > much redundancy as you can manage and as modular for swapping parts > in and > > out as possible. It is absolutely no fun to try and work on anything at > > that height in the winter. > > > > > > John Lock > > kf0m at arrl.net > >
[Repeater-Builder] Re: Yet Another split antenna Question
Hi John, Very Nice... You didn't indicate how much and what type of broadcast is also on the tower? One of the saving grace items in your system is the quality of the Master II Receiver and it's well designed front end. cheers, s. > "kf0m" wrote: > We were at 1400 ft and 1100 ft for a while with the repeater > on the tower running 40 watts TX. That separation was OK for > the Tx and Rx isolation. We ran one can on the RX. an HT > could be full quieting at 50 miles from the repeater. > > The repeater was a Mstr II inside a surplus traffic light > controller box. > > Unfortunately we lost access to the elevator and so we brought the repeater > to the bottom of the tower because of the climbing costs. Takes a lot more > watts and a good preamp and still doesn't equal the range performance but it > is a lot easier to work on especially in cold weather. > > With the repeater in the air, everything needs to be super rugged with as > much redundancy as you can manage and as modular for swapping parts in and > out as possible. It is absolutely no fun to try and work on anything at > that height in the winter. > > > John Lock > kf0m at arrl.net > > > -Original Message- > > From: Repeater-Builder@yahoogroups.com > > [mailto:repeater-buil...@yahoogroups.com]on Behalf Of kb5vjy > > Sent: Wednesday, December 17, 2008 11:05 PM > > To: Repeater-Builder@yahoogroups.com > > Subject: [Repeater-Builder] Yet Another split antenna Question > > > > > > Folks, > > > > I have read just about every split antenna post that I can find.. I > > hate to be a "yet another" poster but here is my situation. I just > > want to know if it is do able. And what problems I might run into. > > > > After months of waiting, I have been issued a repeater pair of > > 147.255 for a long range 2m repeater that will be installed. This is > > my first 2m repeater, but I do have 3 70cm repeaters (all Mastr > > II's).. > > > > My situation is the following: > > > > I have a Mastr II Station 100w Cont. Duty PA for the project... I > > still have to order the xtals. I will run a PL as needed on 127.3. > > The controller will be a CAT (version unsure of) > > > > I have a 2000' broadcast tower with a platform at 1300' and another > > at 1000'. There is a DB 224 mounted under the 1300' and one under > > the 1000' platform with a section of 7/8 feedline running from the > > top platform and the bottom platform. There is a full rack size NEMA > > 12 enclosure on the 1300' platform. After Feb '09 there will be NO > > VHF transmitting equipment on this tower at all. The closest > > transmitter is 6 miles away. > > > > What I would like to do, is mount the radio in the enclosure at the > > top platform. Use the top DB 224 for the Receive antenna, and the > > 1000' DB 224 for the Transmit antenna. What are the problems that I > > will run into with this situation, and should I look for some type of > > filter for the receiver. I do plan on putting an APRS Digi at 1300' > > as well moving one of my 70cm repeaters to the same platform some > > time early next year. > > > > Any comments would be helpful. Thanks.. > > > > 73 de Joe KB5VJY Sorry.. RTTY dayz! > > > > > > > > > > > > > > Yahoo! Groups Links > > > > > > > > >
[Repeater-Builder] Re: Yet Another split antenna Question
> I have a 2000' broadcast tower with a platform at 1300' and another > at 1000'. There is a DB 224 mounted under the 1300' and one under > the 1000' platform with a section of 7/8 feed line running from the > top platform and the bottom platform. > What I would like to do, is mount the radio in the enclosure at the > top platform. Use the top DB 224 for the Receive antenna, and the > 1000' DB 224 for the Transmit antenna. What are the problems that I > will run into with this situation, and should I look for some type > of filter for the receiver. Stray RF will be everywhere and there will probably be a relatively high noise floor at the site. The receivers will tend to block or hose up (not work well) from all the shear amount of RF. For a great system, you will need a decent amount of both the proper type of receiver and transmitter filtering Performance will at first start up probably be less than you might expect or desire... but over time you'll learn how to deal with all the nearby RF. Poorly contained and controlled GasFet Pre-amplifiers will become really good mixers and grunge generators. The hopefully free lunch will probably cost you more than the advertised price. cheers, s.
[Repeater-Builder] Re: Yet Another split antenna Question
Joe, I would use a 6-8" pass can on both the transmitter and receiver. That will give you plenty of isolation. On a large site, I would recommend using a circulator or isolator on the transmitter, just to be a good neighbor, and the VHF Mastr II PA's really like them also. Add a Angle Linear preamp and that thing will be a pretty wild repeater. I would also use 1/4" or 3/8" superflex in the cabinet to cable everything with, even the preamp. Good Luck. Joe - WA7JAW --- In Repeater-Builder@yahoogroups.com, "kb5vjy" wrote: > > Folks, > > I have read just about every split antenna post that I can find.. I > hate to be a "yet another" poster but here is my situation. I just > want to know if it is do able. And what problems I might run into. > > After months of waiting, I have been issued a repeater pair of > 147.255 for a long range 2m repeater that will be installed. This is > my first 2m repeater, but I do have 3 70cm repeaters (all Mastr > II's).. > > My situation is the following: > > I have a Mastr II Station 100w Cont. Duty PA for the project... I > still have to order the xtals. I will run a PL as needed on 127.3. > The controller will be a CAT (version unsure of) > > I have a 2000' broadcast tower with a platform at 1300' and another > at 1000'. There is a DB 224 mounted under the 1300' and one under > the 1000' platform with a section of 7/8 feedline running from the > top platform and the bottom platform. There is a full rack size NEMA > 12 enclosure on the 1300' platform. After Feb '09 there will be NO > VHF transmitting equipment on this tower at all. The closest > transmitter is 6 miles away. > > What I would like to do, is mount the radio in the enclosure at the > top platform. Use the top DB 224 for the Receive antenna, and the > 1000' DB 224 for the Transmit antenna. What are the problems that I > will run into with this situation, and should I look for some type of > filter for the receiver. I do plan on putting an APRS Digi at 1300' > as well moving one of my 70cm repeaters to the same platform some > time early next year. > > Any comments would be helpful. Thanks.. > > 73 de Joe KB5VJY Sorry.. RTTY dayz! >
