Re: [Repeater-Builder] Re: Dual receivers on one antenna for RX only site
At 3/10/2010 02:42, you wrote: On Mar 9, 2010, at 8:37 PM, n...@no6b.com wrote: t most certainly does. Try random length cables from the cavities to the T instead of 1/4 wavelength (like one local did several years ago) watch your sensitivity drop by over 20 dB if you're unlucky (as he was). That mistake literally killed off a local radio club, as few of the members were able to use the repeater following the addition of the T wrong cables. Thanks both Bob and Skipp for explaining that one odd-ball configuration that would crush the receivers with random cable lengths that just happen to hit the right sweet spot to do this. I suspect, that if someone saw a 20 dB loss while installing this setup, they'd at least STOP and start asking questions -- maybe they wouldn't get it that they'd hit this perfect storm combination -- maybe they'd think they had some kind of receiver failure when it suddenly was really deaf -- but I also doubt that *most* people would hit the problem. Would you agree with that assessment? (Skipp's comment that if there's a train wreck to be found, he'll be there... I know that feeling.) In this case, the owner wrote the poor sensitivity off to site noise. The club was based a good 30 miles from the repeater, but before it was transferred it worked just fine in the target area. After the system was modified/deafened, an article was written in the club newsletter explaining how the repeater was too far away from the club's user base for HTs to work there. Funny how after the repeater was sold off to yet another trustee, it suddenly began to receive well again. That's when I found out what was done that made it so deaf in the interim. Bob NO6B
Re: [Repeater-Builder] Re: Dual receivers on one antenna for RX only site
On Mar 9, 2010, at 8:37 PM, n...@no6b.com wrote: t most certainly does. Try random length cables from the cavities to the T instead of 1/4 wavelength (like one local did several years ago) watch your sensitivity drop by over 20 dB if you're unlucky (as he was). That mistake literally killed off a local radio club, as few of the members were able to use the repeater following the addition of the T wrong cables. Thanks both Bob and Skipp for explaining that one odd-ball configuration that would crush the receivers with random cable lengths that just happen to hit the right sweet spot to do this. I suspect, that if someone saw a 20 dB loss while installing this setup, they'd at least STOP and start asking questions -- maybe they wouldn't get it that they'd hit this perfect storm combination -- maybe they'd think they had some kind of receiver failure when it suddenly was really deaf -- but I also doubt that *most* people would hit the problem. Would you agree with that assessment? (Skipp's comment that if there's a train wreck to be found, he'll be there... I know that feeling.) I guess what I'm saying here in a round-about way is... random cable lengths really shouldn't be that much of an issue in a setup like this, but yeah... agreed... once in a while it'll bite you like an alligator (had to get that elephant/alligator theme in here, just one more time! GRIN!)... I've seen lots of people get away with it. As far as the 3dB lost in a true broadband splitter -- also true, of course, Bob -- at most of the sites where we have to share a receive antenna with multiple rigs, the site measured noise-floor is so high the 3dB doesn't have much of an impact... just keeping the local crud out of the receivers is difficult enough -- sometimes that 3dB loss helps, instead of hinders, so to speak. :-) I guess we should all probably also mention the evils of not terminating all the unused ports on a multi-splitter with 50 Ohm loads, too... if we're going to get this picky, right? ;-) -- Nate Duehr, WY0X n...@natetech.com facebook.com/denverpilot twitter.com/denverpilot
RE: [Repeater-Builder] Re: Dual receivers on one antenna for RX only site
with the same kind of loss that you get on a transmitter due to high vswr. 73 Gary K4FMX -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- buil...@yahoogroups.com] On Behalf Of Nate Duehr Sent: Wednesday, March 10, 2010 5:42 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Re: Dual receivers on one antenna for RX only site On Mar 9, 2010, at 8:37 PM, n...@no6b.com wrote: t most certainly does. Try random length cables from the cavities to the T instead of 1/4 wavelength (like one local did several years ago) watch your sensitivity drop by over 20 dB if you're unlucky (as he was). That mistake literally killed off a local radio club, as few of the members were able to use the repeater following the addition of the T wrong cables. Thanks both Bob and Skipp for explaining that one odd-ball configuration that would crush the receivers with random cable lengths that just happen to hit the right sweet spot to do this. I suspect, that if someone saw a 20 dB loss while installing this setup, they'd at least STOP and start asking questions -- maybe they wouldn't get it that they'd hit this perfect storm combination -- maybe they'd think they had some kind of receiver failure when it suddenly was really deaf -- but I also doubt that *most* people would hit the problem. Would you agree with that assessment? (Skipp's comment that if there's a train wreck to be found, he'll be there... I know that feeling.) I guess what I'm saying here in a round-about way is... random cable lengths really shouldn't be that much of an issue in a setup like this, but yeah... agreed... once in a while it'll bite you like an alligator (had to get that elephant/alligator theme in here, just one more time! GRIN!)... I've seen lots of people get away with it. As far as the 3dB lost in a true broadband splitter -- also true, of course, Bob -- at most of the sites where we have to share a receive antenna with multiple rigs, the site measured noise-floor is so high the 3dB doesn't have much of an impact... just keeping the local crud out of the receivers is difficult enough -- sometimes that 3dB loss helps, instead of hinders, so to speak. :-) I guess we should all probably also mention the evils of not terminating all the unused ports on a multi-splitter with 50 Ohm loads, too... if we're going to get this picky, right? ;-) -- Nate Duehr, WY0X n...@natetech.com facebook.com/denverpilot twitter.com/denverpilot
[Repeater-Builder] Re: Dual receivers on one antenna for RX only site
One thing was missed regarding cable lengths. The loops in the cans are part of the equation for figuring the 1/4 wave length. I've seen that discussed here many times in postings related to inter-cable lengths on duplexers. But the 1/4 wave length issue only applies to the inter-cabling between the cans. It is my understanding that the antenna to duplexer lengths are irrelevant since the T connector and the rest of the feedline are all part of the equation. It's not like the T is some magical device that makes the rest of the feedline disappear electrically. The only time length might be a problem is if the entire feedline happens to be a resonant length. If by some chance that happens, then changing the jumper a couple of inches will clear that. Dan N8DJP Posted by: n...@no6b.com n...@no6b.com no6b Date: Tue Mar 9, 2010 8:29 pm ((PST)) At 3/9/2010 20:12, you wrote: OK, question... If you put a cable which is 1/4-wavelength at VHF between the T and the UHF cavity, it's 3/4-wavelength at UHF. Since any odd multiple of a quarter wavelength will invert the impedance, what will this really accomplish on the UHF cavity side? Doesn't matter at UHF, since the cavity looks like (hopefully something close to) 50 + j0 ohms @ UHF, so the cable length has no effect (other than plain ol' cable loss) @ UHF. At VHF, the short at the UHF cavity connector (I'll take Gary's word that it looks like a short off-resonance, though to be sure you'd want to put the can on a VNA to get the actual phase angle at the connector) needs to be transformed to an open at the T so it has no effect VHF. The short-to-open transformation @ VHF is accomplished with a 1/4 wavelength of coax @ VHF. The dual-band diplexers are usually high-pass/low-pass arrangements, and lose something like 0.2 dB while providing 40 dB or more isolation. Assuming you get a real one, and not something made with PIM-prne materials, would this not be a safer bet? It's true you wouldn't need to mess with cable lengths if a cross-band diplexer were used, but OTOH it would be another piece of hardware in the system that really isn't necessary, since the cavities are already there. Plus if you're really worried about PIM, you'd probably have to move up to something like a cross-band coupler from TX-RX, which IIRC runs over $300. Bob NO6B
[Repeater-Builder] Re: Dual receivers on one antenna for RX only site-cable length
In all of the discussion on cable lengths between a T and cavities to split to receivers, I'm wondering if the loop length inside of each cavity is to be included in cable lengths. It seems it always is included when calculating cavity interconnect cables on a duplexer, for example, but has not been mentioned in this thread. If loop length IS to be included, what is the assumed velocity factor of a cavity loop? Laryn K8TVZ
RE: [Repeater-Builder] Re: Dual receivers on one antenna for RX only site
Well yes the T is sort of a magical device that makes the OTHER SIDE of the T disappear electrically. Actually it is not the T itself that does the job (that is just where IT happens) but it is the quarter wave length cables that perform the magic! Without the quarter wave length cables between the T and each set of cavities the duplexer would not work! That is what provides the 50 ohm isolation between tx and rx cans so the feed line still sees 50 ohms. The quarter wave cable effectively disconnects the transmitter from the feed line at the T (at the receive frequency). The quarter wave cable on the receive side of the T effectively disconnects the receive side from the feed line (at the transmit frequency). Without doing this each would load the other down and there would not be 50 ohms at the antenna port of the T. Once you are on the other side of the T (the antenna port) the feed line length has no effect on the duplexer operation. All that the quarter wave lines do on the duplexer side of the T are to give isolation to the opposite side (tx-rx) so each does not short out the feed line. A similar thing happens between can cables in a duplexer but rather than using them for isolation they are used to enhance the notch of each can by presenting a high impedance at each cans T from the previous cavity. Working with a high impedance is easier to notch out than a low impedance. The notch in the first cavity presents a short (low impedance) at the unwanted frequency and 50 ohms at the wanted frequency. By coupling the next cavity with a quarter wave length cable (at the unwanted frequency) that short is transformed to a quite high impedance at the next cavity while at the same time the wanted signal being at 50 ohms is passed to the next cavity where it sees 50 ohms and goes on its way unatenuated. But we are left with the high impedance at the unwanted frequency that was transformed by the quarter wave cable. The second cavity notch is also tuned to the unwanted frequency which it pulls down to a short (low impedance) to give further attenuation. When I say the notch presents a short it is not really a short but a very low impedance of say a few ohms. But by having the unwanted source impedance high rather than at 50 ohms it is much easier to pull the high impedance down with the few ohms short circuit than it would be if we were working at 50 ohms for the unwanted. It works like a voltage divider between the two impedances. The higher the source is (from previous cavity) to the short the more loss there will be which is just what we are looking for. In the case of the quarter wave cable to the T on the output of the duplexer we want to transform the low impedance up to a very high impedance at the T so that it does not load the circuit at that point on that frequency. 73 Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Dan Hancock Sent: Wednesday, March 10, 2010 12:50 PM To: repeater builders Subject: [Repeater-Builder] Re: Dual receivers on one antenna for RX only site One thing was missed regarding cable lengths. The loops in the cans are part of the equation for figuring the 1/4 wave length. I've seen that discussed here many times in postings related to inter-cable lengths on duplexers. But the 1/4 wave length issue only applies to the inter-cabling between the cans. It is my understanding that the antenna to duplexer lengths are irrelevant since the T connector and the rest of the feedline are all part of the equation. It's not like the T is some magical device that makes the rest of the feedline disappear electrically. The only time length might be a problem is if the entire feedline happens to be a resonant length. If by some chance that happens, then changing the jumper a couple of inches will clear that. Dan N8DJP Posted by: n...@no6b.com http://us.mc1104.mail.yahoo.com/mc/compose?to=n...@no6b.com n...@no6b.com http://us.mc1104.mail.yahoo.com/mc/compose?to=n...@no6b.com no6b Date: Tue Mar 9, 2010 8:29 pm ((PST)) At 3/9/2010 20:12, you wrote: OK, question... If you put a cable which is 1/4-wavelength at VHF between the T and the UHF cavity, it's 3/4-wavelength at UHF. Since any odd multiple of a quarter wavelength will invert the impedance, what will this really accomplish on the UHF cavity side? Doesn't matter at UHF, since the cavity looks like (hopefully something close to) 50 + j0 ohms @ UHF, so the cable length has no effect (other than plain ol' cable loss) @ UHF. At VHF, the short at the UHF cavity connector (I'll take Gary's word that it looks like a short off-resonance, though to be sure you'd want to put the can on a VNA to get the actual phase angle at the connector) needs to be transformed to an open at the T so it has no effect VHF. The short-to-open transformation @ VHF is accomplished with a 1/4 wavelength of coax @ VHF. The dual
RE: [Repeater-Builder] Re: Dual receivers on one antenna for RX only site
When I say the notch presents a short it is not really a short but a very low impedance of say a few ohms. But by having the unwanted source impedance high rather than at 50 ohms it is much easier to pull the high impedance down with the few ohms short circuit than it would be if we were working at 50 ohms for the unwanted. It works like a voltage divider between the two impedances. The higher the source is (from previous cavity) to the short the more loss there will be which is just what we are looking for. Your use of the voltage divider description is probably the best way to explain the effect, and shows why having the correct intra-cavity cable length is important for getting the maximum rejection. Using exactly the right cable length between two cavity filters will give somewhere around 5 or 6 dB of additional rejection (i.e. if the cavities individually afforded 40 dB of isolation, when cascaded with the right cable length you'll get about 85 dB total). If you use exactly the wrong cable length (i.e. if you're off by a quarter-wave), the combined isolation will be LESS than that of the cavities individually; a good indication that you have the wrong cable length is when you can't get the notches to overlay at the same frequency (often the notches will look like they're chasing each other on the VNA as you adjust them). Between the right and wrong cable lengths you'll end up with a net isolation somewhere between the two extremes. Assuming the cavities individually present a good match at the pass frequency, varying the interconnecting cable length between two cascaded filters will not affect the insertion loss or return loss. In contrast, the cable length from the tee to the first cavity on each side of the duplexer primarily affects only the insertion loss through the duplexer, and the return loss from antenna to/from either Tx or Rx port, unlike the cable between adjacent cavities which affects the isolation (rejection) afforded by that half of the duplexer. A while back I posted a blurb that demonstrates the effects of using the wrong cable length between cascaded filters. I don't know if that made it to the web site? --- Jeff WN3A
[Repeater-Builder] Re: Dual receivers on one antenna for RX only site
Actually, Gary, you are 180 degrees out. On a pass cavity, off frequency signals see a very high impedence path, an open not a short. If your version were true you could never use pass cans as a duplexer since both sets of cans together would show a short to EVERYTHING. The T connector is just an impedence bump to the radio equipment, nothing more. It is not an active device, like a preamp would be, that makes the rest of the feedline disappear. He can use the T connector and any random length of cable to connect, as long as the whole feedline doesn't show up as a resonant length. Dan N8DJP Posted by: Gary Schafer gascha...@comcast.net k4fmx Date: Wed Mar 10, 2010 10:47 am ((PST)) Well yes the T is sort of a magical device that makes the OTHER SIDE of the T disappear electrically. Actually it is not the T itself that does the job (that is just where IT happens) but it is the quarter wave length cables that perform the magic! Without the quarter wave length cables between the T and each set of cavities the duplexer would not work! That is what provides the 50 ohm isolation between tx and rx cans so the feed line still sees 50 ohms. The quarter wave cable effectively disconnects the transmitter from the feed line at the T (at the receive frequency). The quarter wave cable on the receive side of the T effectively disconnects the receive side from the feed line (at the transmit frequency). Without doing this each would load the other down and there would not be 50 ohms at the antenna port of the T. Once you are on the other side of the T (the antenna port) the feed line length has no effect on the duplexer operation. All that the quarter wave lines do on the duplexer side of the T are to give isolation to the opposite side (tx-rx) so each does not short out the feed line. A similar thing happens between can cables in a duplexer but rather than using them for isolation they are used to enhance the notch of each can by presenting a high impedance at each cans T from the previous cavity. Working with a high impedance is easier to notch out than a low impedance. The notch in the first cavity presents a short (low impedance) at the unwanted frequency and 50 ohms at the wanted frequency. By coupling the next cavity with a quarter wave length cable (at the unwanted frequency) that short is transformed to a quite high impedance at the next cavity while at the same time the wanted signal being at 50 ohms is passed to the next cavity where it sees 50 ohms and goes on its way unatenuated. But we are left with the high impedance at the unwanted frequency that was transformed by the quarter wave cable. The second cavity notch is also tuned to the unwanted frequency which it pulls down to a short (low impedance) to give further attenuation. When I say the notch presents a short it is not really a short but a very low impedance of say a few ohms. But by having the unwanted source impedance high rather than at 50 ohms it is much easier to pull the high impedance down with the few ohms short circuit than it would be if we were working at 50 ohms for the unwanted. It works like a voltage divider between the two impedances. The higher the source is (from previous cavity) to the short the more loss there will be which is just what we are looking for. In the case of the quarter wave cable to the T on the output of the duplexer we want to transform the low impedance up to a very high impedance at the T so that it does not load the circuit at that point on that frequency. 73 Gary K4FMX
Re: [Repeater-Builder] Re: Dual receivers on one antenna for RX only site
At 3/10/2010 11:16, you wrote: Actually, Gary, you are 180 degrees out. On a pass cavity, off frequency signals see a very high impedence path, an open not a short. If your version were true you could never use pass cans as a duplexer since both sets of cans together would show a short to EVERYTHING. I wish I had the VNA data from the pass cavities I measured several years ago when I built a 2-port UHF combiner using them, but they were measured while the pen plotter was connected to the VNA before I wrote a program to convert the Citifile output from the VNA to Excel spreadsheets, so the data was only saved on paper I have no idea where I would've stuffed the plots. But my best recollection is that at the reference plane of the cavities (front surface of the female N or SO-239 connector, they looked fairly close to an open, but not quite - maybe 10 to 15 degrees off of an open, on the inductive side. Bob NO6B
[Repeater-Builder] Re: Dual receivers on one antenna for RX only site
Ross Johnson kc7...@... wrote: Hello to the group, My name is Ross KC7RJK This is my first post. Hi Ross, My name is skipp and I'm a junkoholic... hi skipp and I %#*^ scuse me, lost my mind for a moment. Moving along Most questions are answered from that amazing and up to date web site! I thank you all involved very very much for that. We don't play up the RB web site nearly enough... we also don't let Kevin, Scott or Mike run with scissors. Well here's the question I've found little and conflicting info on the web about. So feel free to point me the right way here. Simple, go west... better weather and less humidity. Can a dualband antenna VHF/UHF for RX ONLY be fed to two receivers one VHF, one UHF, without a quote duplexer using a T instead? Of course, but it may not be the best situation. Here's the idea. This is a remote RX site. The idea is to run something like a beefed up X500 dualbander at tower top, then 7/8 hardline 100 feet down to the receivers. Both receivers will have one or two bandpass cavities inline before the T. Would a duplexer be necessary in this case. Or could it be done with proper cable lengths and a T? Doesn't even need the special cable lengths but there is a reason for doing everything and here comes questions 101. Will the receivers stay on one frequency as in a repeater receiver or do you need to move around each band a bit? How much other RF is around? ... does the site have a lot of transmitters and are any of the high power monsters as in the case of paging or broadcast? If you don't have a lot of adjacent frequency operation going on there are two other options to consider. One is the Diamond or Comet type of band splitter, which actually would take the place of your T and be much better. Model CF-4160K http://www.universal-radio.com/CATALOG/hamantm/cduplex.html And another very nice option would be the DCI dual band filter Model: DCI-146-444-DB. http://www.dci.ca/?Section=ProductsSubSection=Amateur And you can use the plain T, a more traditional signal divider and various combination of band-pass cavity layouts. Thanks for your time and for the probably obvious answer I'm not sure of. Regards Ross KC7RJK be more worried when you feel sure of yourself. cheers, skipp
[Repeater-Builder] Re: Dual receivers on one antenna for RX only site
On 3/9/2010 4:53 PM, Gary Schafer wrote: Without the proper length cables between the cavities and the antenna T connector both UHF and VHF signals will be attenuated depending on the luck of the cable length. Nate Duehr n...@... wrote: What technical reason causes this? Nate I could think of one really bad luck example... the cable length between the receivers through the T is x-value wave-length and the front end pre-selection of one or both receivers also has an unexpected (third) odd wave length response on the other band. Could happen... and in my case probably would happen when I need something to work in a middle of the night pinch. s. If there's a train wreck gonna happen, I'll probably be there...
Re: [Repeater-Builder] Re: Dual receivers on one antenna for RX only site
At 3/9/2010 16:29, you wrote: Here's the idea. This is a remote RX site. The idea is to run something like a beefed up X500 dualbander at tower top, then 7/8 hardline 100 feet down to the receivers. Both receivers will have one or two bandpass cavities inline before the T. Would a duplexer be necessary in this case. Or could it be done with proper cable lengths and a T? Doesn't even need the special cable lengths It most certainly does. Try random length cables from the cavities to the T instead of 1/4 wavelength (like one local did several years ago) watch your sensitivity drop by over 20 dB if you're unlucky (as he was). That mistake literally killed off a local radio club, as few of the members were able to use the repeater following the addition of the T wrong cables. but there is a reason for doing everything and here comes questions 101. Will the receivers stay on one frequency as in a repeater receiver or do you need to move around each band a bit? If he's got bandpass cavities in front of the RXs already, they're very likely not frequency-agile. How much other RF is around? ... does the site have a lot of transmitters and are any of the high power monsters as in the case of paging or broadcast? If you don't have a lot of adjacent frequency operation going on there are two other options to consider. One is the Diamond or Comet type of band splitter, which actually would take the place of your T and be much better. That would be my choice, but if he's already got the cans, a pair of 1/4 wavelength cables will be much cheaper. I'd stay away from using a broadband isolated power divider (splitter), as you'll lose 3 dB in the split. The frequency-splitting options lose virtually no signal. Bob NO6B
RE: [Repeater-Builder] Re: Dual receivers on one antenna for RX only site
Thanks for the replys everyone. That cleared it up for sure. I will go ahead and build the T to cavity cables to one electrical wave length for the other band. And is that ¼ wave plus velocity factor of cable? Which will be FSJ1. Here is some more detail on the system. It will go in stages. The final stage will be this remote receive setup with a UHF link on the bottom of the tower to the transmitter site. Also toying with a VOIP link with UHF as a failsafe. At this point the receivers are on separate antennas at the top of the tower, with 2 bandpass Sinclair 1-150-1S7 cavitys on the VHF, and one big Wacom cavity on the UHF receiver. The remote TX site hasnt been installed yet (waiting to find a MSR2000 UHF RX board for this divorced VHF TX site) so the transmitter is temporally at this site also. There are two bandpass cavitys DB4001s on this Mastr II transmitter with the antenna 40-50 feet down from the receive antenna. Sensitivity is shocking good right now with this setup. Very little RX loss, and very little desens. Will the receivers stay on one frequency as in a repeater receiver or do you need to move around each band a bit? Yes they will stay put. How much other RF is around? ... Does the site have a lot of transmitters and are any of the high power monsters as in the case of paging or broadcast? None in these bands! :-) But wireless ISP Ive found to be very noisy allover the place there. 50Mhz and up! Thanks again everyone! -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of skipp025 Sent: Tuesday, March 09, 2010 4:29 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Re: Dual receivers on one antenna for RX only site Ross Johnson kc7...@... wrote: Hello to the group, My name is Ross KC7RJK This is my first post. Hi Ross, My name is skipp and I'm a junkoholic... hi skipp and I %#*^ scuse me, lost my mind for a moment. Moving along Most questions are answered from that amazing and up to date web site! I thank you all involved very very much for that. We don't play up the RB web site nearly enough... we also don't let Kevin, Scott or Mike run with scissors. Well here's the question I've found little and conflicting info on the web about. So feel free to point me the right way here. Simple, go west... better weather and less humidity. Can a dualband antenna VHF/UHF for RX ONLY be fed to two receivers one VHF, one UHF, without a quote duplexer using a T instead? Of course, but it may not be the best situation. Here's the idea. This is a remote RX site. The idea is to run something like a beefed up X500 dualbander at tower top, then 7/8 hardline 100 feet down to the receivers. Both receivers will have one or two bandpass cavities inline before the T. Would a duplexer be necessary in this case. Or could it be done with proper cable lengths and a T? Doesn't even need the special cable lengths but there is a reason for doing everything and here comes questions 101. Will the receivers stay on one frequency as in a repeater receiver or do you need to move around each band a bit? How much other RF is around? ... does the site have a lot of transmitters and are any of the high power monsters as in the case of paging or broadcast? If you don't have a lot of adjacent frequency operation going on there are two other options to consider. One is the Diamond or Comet type of band splitter, which actually would take the place of your T and be much better. Model CF-4160K http://www.universa http://www.universal-radio.com/CATALOG/hamantm/cduplex.html l-radio.com/CATALOG/hamantm/cduplex.html And another very nice option would be the DCI dual band filter Model: DCI-146-444-DB. http://www.dci. http://www.dci.ca/?Section=ProductsSubSection=Amateur ca/?Section=ProductsSubSection=Amateur And you can use the plain T, a more traditional signal divider and various combination of band-pass cavity layouts. Thanks for your time and for the probably obvious answer I'm not sure of. Regards Ross KC7RJK be more worried when you feel sure of yourself. cheers, skipp
Re: [Repeater-Builder] Re: Dual receivers on one antenna for RX only site
Ross Johnson wrote: Thanks for the reply’s everyone. That cleared it up for sure. I will go ahead and build the T to cavity cables to one electrical wave length for the other band. And is that ¼ wave plus velocity factor of cable? Which will be FSJ1. Actually, it's 1/4-wave times the velocity factor, sorta. If the VF is, say, 85%, then you multiply the 1/4-wave by .85. Also, you can use any ODD multiple of a 1/4-wave: 3/4, 1-1/4, 1-3/4, etc. It'll be a real pain to try to connect to that 6 long(-ish) UHF 1/4-wave cable! Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * Your email settings: Individual Email | Traditional * To change settings online go to: http://groups.yahoo.com/group/Repeater-Builder/join (Yahoo! ID required) * To change settings via email: repeater-builder-dig...@yahoogroups.com repeater-builder-fullfeatu...@yahoogroups.com * To unsubscribe from this group, send an email to: repeater-builder-unsubscr...@yahoogroups.com * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
