[Repeater-Builder] UHF Repeater Amps For Sale
I have two UHF repeater Amps for sale 1. TPL PA6-1BE 8 - 20 watts in 70 - 100 watts out, continuous duty. $ 275 includes shipping. 2. GE MASTR II PL19D424895G32 1/2 watt in 110 watts out $ 250, not sure, but I think this is cont. duty, has a real big heatsink. includes shipping. Both work in ham band. Bob W2XL 845-417-1894 or e-mail
Re: [Repeater-Builder] UHF Repeater Amps For Sale
Could you shoot me a photo of the TPL PA6-1BE ? _ Eddie Cope wb5hhz --- On Sun, 7/11/10, wb2bxl w...@hvc.rr.com wrote: From: wb2bxl w...@hvc.rr.com Subject: [Repeater-Builder] UHF Repeater Amps For Sale To: Repeater-Builder@yahoogroups.com Date: Sunday, July 11, 2010, 2:34 PM I have two UHF repeater Amps for sale 1. TPL PA6-1BE 8 - 20 watts in 70 - 100 watts out, continuous duty. $ 275 includes shipping. 2. GE MASTR II PL19D424895G32 1/2 watt in 110 watts out $ 250, not sure, but I think this is cont. duty, has a real big heatsink. includes shipping. Both work in ham band. Bob W2XL 845-417-1894 or e-mail
Re: [Repeater-Builder] UHF Repeater Amps For Sale
I'd also be interested in a photo. Thanks. Hal Brueseke KA9MXW - Original Message - From: Eddie Cope To: Repeater-Builder@yahoogroups.com Sent: Sunday, July 11, 2010 5:42 PM Subject: Re: [Repeater-Builder] UHF Repeater Amps For Sale Could you shoot me a photo of the TPL PA6-1BE ? _ Eddie Cope wb5hhz --- On Sun, 7/11/10, wb2bxl w...@hvc.rr.com wrote: From: wb2bxl w...@hvc.rr.com Subject: [Repeater-Builder] UHF Repeater Amps For Sale To: Repeater-Builder@yahoogroups.com Date: Sunday, July 11, 2010, 2:34 PM I have two UHF repeater Amps for sale 1. TPL PA6-1BE 8 - 20 watts in 70 - 100 watts out, continuous duty. $ 275 includes shipping. 2. GE MASTR II PL19D424895G32 1/2 watt in 110 watts out $ 250, not sure, but I think this is cont. duty, has a real big heatsink. includes shipping. Both work in ham band. Bob W2XL 845-417-1894 or e-mail
[Repeater-Builder] UHF repeater antenna recommendations
Hello all, looking for amateur UHF repeater antenna recommendations. The antenna will be over 700ft in the air, looking for something that will hold up in the wind and what ever Mother Nature might dish out.
Re: [Repeater-Builder] UHF repeater antenna recommendations
Comprod makes an extra heavy-duty folded dipole array. It won't be cheap, but then again you want it to survive for a long time. Tower work at that elevation isn't cheap either. Chuck WB2EDV - Original Message - From: camper161 camper...@yahoo.com To: Repeater-Builder@yahoogroups.com Sent: Monday, March 08, 2010 3:50 PM Subject: [Repeater-Builder] UHF repeater antenna recommendations Hello all, looking for amateur UHF repeater antenna recommendations. The antenna will be over 700ft in the air, looking for something that will hold up in the wind and what ever Mother Nature might dish out. Yahoo! Groups Links No virus found in this incoming message. Checked by AVG - www.avg.com Version: 9.0.733 / Virus Database: 271.1.1/2730 - Release Date: 03/08/10 02:34:00
Re: [Repeater-Builder] UHF repeater antenna recommendations
Sinclair HD (heavy duty) folded-dipoles (various models - how many bays and how much gain do you want?) have served well for decades around here. Have also seen DB products arrays last similarly long lifespans in other clubs/groups in the area. One of those (dual-mast, 8-bay folded-dipole variety) only died when it took a direct lightning strike, welded itself together at the joint between the two masts, and had holes the size of dimes in it where the lightning jumped from mast to tower. It was still working, but SWR was crazy, and of course, radiation pattern was anything but normal... but the repeater (with an isolator) was still on-air and usable. Similar lightning blew fiberglass stick antennas taller than me into so many tiny little white bits, that the remainder of the antenna other than the bottom mount, fit nicely in a kitchen-sized garbage bag, for one unlucky group out here. They were NOT on-air until they replaced it, of course. The only killer out here besides lightning... bad weatherproofing. Go ALL OUT on weather-proofing connections. Have seen more instances of water ingress killed the hardline feeding the antenna, than the antennas themselves failing. We also tend to have almost zero issues with heavy icing -- it's typically too dry here -- but the few times I've seen it, the arrays were so covered that system performance was actually degraded, but no physical damage from the ice hanging from the antennas. Ice FALLING from antennas/platforms/etc when the weather turned warmer and started it melting... from ABOVE... has broken antennas... has sliced hardline, etc. Nate WY0X On 3/8/2010 2:06 PM, Chuck Kelsey wrote: Comprod makes an extra heavy-duty folded dipole array. It won't be cheap, but then again you want it to survive for a long time. Tower work at that elevation isn't cheap either. Chuck WB2EDV - Original Message - From: camper161 camper...@yahoo.com mailto:camper161%40yahoo.com To: Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com Sent: Monday, March 08, 2010 3:50 PM Subject: [Repeater-Builder] UHF repeater antenna recommendations Hello all, looking for amateur UHF repeater antenna recommendations. The antenna will be over 700ft in the air, looking for something that will hold up in the wind and what ever Mother Nature might dish out.
[Repeater-Builder] UHF Repeater For Sale....
FOR SALE: 1-Maggorie Hi-Pro R-1 UHF Repeater 1-Astron RM-50M Power Supply 1-CAT Controller 1-Arcom RC-210 Controller 1-Wacom UHF Duplexer 1-DB Antenna with 7/8 Hardline (If you want to climb the 225 FT Tower) Buyer must either pick up or arriange shipping. Grady L. Evans w4...@yahoo.com 205-270-9030 W4GLE
RE: [Repeater-Builder] UHF Repeater Antenna -- UPDATE
Err, I meant, coax center pin and ground. Oops. JS -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- [EMAIL PROTECTED] On Behalf Of Jacob Suter Sent: Monday, October 20, 2008 12:17 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] UHF Repeater Antenna -- UPDATE DC Grounded, in my experience, means the center pin and the coax will show a dc short when tested with a DMM. Lightning? Corrosion? Manufacturing defect? JS
[Repeater-Builder] UHF repeater amp wanted
Hi guys, Our club is looking for a small repeater amp (50 watts max) for our UHF machine. Right now its putting out a whopping 6 watts - we did a test with a 25 watt strip off a TAD-450 commercial rig and the listening station reported a significant gain. The signal went from 1 s unit on his rig to 8 s-units. I am wondering if any of the GE or Motorola final strips are good enough to handle the duty cycle. The little TAD unit I tried briefly worked, but I'm sure would burn out in short order. You can contact me off list at va2ir at securenet dot net Thanks Ian VA2IR VE2RMP Repeater Group
Re: [Repeater-Builder] UHF repeater amp wanted
where are you at? - Original Message - From: Ian Miller To: Repeater-Builder@yahoogroups.com Sent: Wednesday, October 22, 2008 11:07 AM Subject: [Repeater-Builder] UHF repeater amp wanted Hi guys, Our club is looking for a small repeater amp (50 watts max) for our UHF machine. Right now its putting out a whopping 6 watts - we did a test with a 25 watt strip off a TAD-450 commercial rig and the listening station reported a significant gain. The signal went from 1 s unit on his rig to 8 s-units. I am wondering if any of the GE or Motorola final strips are good enough to handle the duty cycle. The little TAD unit I tried briefly worked, but I'm sure would burn out in short order. You can contact me off list at va2ir at securenet dot net Thanks Ian VA2IR VE2RMP Repeater Group
Re: [Repeater-Builder] UHF repeater amp wanted
how about the PA section off a UHF Maxar ? - Original Message - From: Ian Miller To: Repeater-Builder@yahoogroups.com Sent: Wednesday, October 22, 2008 10:07 AM Subject: [Repeater-Builder] UHF repeater amp wanted Hi guys, Our club is looking for a small repeater amp (50 watts max) for our UHF machine. Right now its putting out a whopping 6 watts - we did a test with a 25 watt strip off a TAD-450 commercial rig and the listening station reported a significant gain. The signal went from 1 s unit on his rig to 8 s-units. I am wondering if any of the GE or Motorola final strips are good enough to handle the duty cycle. The little TAD unit I tried briefly worked, but I'm sure would burn out in short order. You can contact me off list at va2ir at securenet dot net Thanks Ian VA2IR VE2RMP Repeater Group -- Checked by AVG - http://www.avg.com Version: 8.0.175 / Virus Database: 270.8.2/1739 - Release Date: 10/22/2008 7:23 AM
[Repeater-Builder] UHF Repeater Antenna -- UPDATE
Folks, *Continuation of Previous Thread: UHF Repeater Antenna Discussion* We climbed the tower on Sunday and checked things with the wattmeter between the Feedline and the antenna. At the bottom, we were making 75 Watts at the duplexer output. At the top, after going through 105' of LDF4.5-50A (just over 1dB of loss), a PolyPhaser, and a 6' jumper of RG400 (from the duplexer to the PolyPhaser) we were seeing 57 Watts. I show that as about 1.2 dB of loss, which seems quite reasonable. The F10, at the top, showed me about 1.5W reflected... or 1.34:1 VSWR. The antenna is a DC grounded colinear, and we showed no measurable (with my DMM) resistance between the center pin and outer conductor of the Hardline/Antenna combination. Right now, we're of the mind that the feedline is good. 73 DE N0MJS -- Cort Buffington H: +1-785-838-3034 M: +1-785-865-7206
RE: [Repeater-Builder] UHF Repeater Antenna -- UPDATE
DC Grounded, in my experience, means the center pin and the coax will show a dc short when tested with a DMM. Lightning? Corrosion? Manufacturing defect? JS -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- [EMAIL PROTECTED] On Behalf Of Cort Buffington Sent: Monday, October 20, 2008 11:29 AM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] UHF Repeater Antenna -- UPDATE Folks, *Continuation of Previous Thread: UHF Repeater Antenna Discussion* We climbed the tower on Sunday and checked things with the wattmeter between the Feedline and the antenna. At the bottom, we were making 75 Watts at the duplexer output. At the top, after going through 105' of LDF4.5-50A (just over 1dB of loss), a PolyPhaser, and a 6' jumper of RG400 (from the duplexer to the PolyPhaser) we were seeing 57 Watts. I show that as about 1.2 dB of loss, which seems quite reasonable. The F10, at the top, showed me about 1.5W reflected... or 1.34:1 VSWR. The antenna is a DC grounded colinear, and we showed no measurable (with my DMM) resistance between the center pin and outer conductor of the Hardline/Antenna combination. Right now, we're of the mind that the feedline is good. 73 DE N0MJS -- Cort Buffington H: +1-785-838-3034 M: +1-785-865-7206
Re: [Repeater-Builder] UHF Repeater Antenna -- UPDATE
Is not no measureable resistance the same as a short? Zero ohms is just what it should show...why would that indicate damage or defect? - Original Message - From: Jacob Suter To: Repeater-Builder@yahoogroups.com Sent: Monday, October 20, 2008 11:17 AM Subject: RE: [Repeater-Builder] UHF Repeater Antenna -- UPDATE DC Grounded, in my experience, means the center pin and the coax will show a dc short when tested with a DMM. Lightning? Corrosion? Manufacturing defect? JS -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- [EMAIL PROTECTED] On Behalf Of Cort Buffington Sent: Monday, October 20, 2008 11:29 AM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] UHF Repeater Antenna -- UPDATE Folks, *Continuation of Previous Thread: UHF Repeater Antenna Discussion* We climbed the tower on Sunday and checked things with the wattmeter between the Feedline and the antenna. At the bottom, we were making 75 Watts at the duplexer output. At the top, after going through 105' of LDF4.5-50A (just over 1dB of loss), a PolyPhaser, and a 6' jumper of RG400 (from the duplexer to the PolyPhaser) we were seeing 57 Watts. I show that as about 1.2 dB of loss, which seems quite reasonable. The F10, at the top, showed me about 1.5W reflected... or 1.34:1 VSWR. The antenna is a DC grounded colinear, and we showed no measurable (with my DMM) resistance between the center pin and outer conductor of the Hardline/Antenna combination. Right now, we're of the mind that the feedline is good. 73 DE N0MJS -- Cort Buffington H: +1-785-838-3034 M: +1-785-865-7206
Re: [Repeater-Builder] UHF Repeater Antenna -- UPDATE
My intention was to indicate short. On Oct 20, 2008, at 5:56 PM, Paul Plack wrote: Is not no measureable resistance the same as a short? Zero ohms is just what it should show...why would that indicate damage or defect? - Original Message - From: Jacob Suter To: Repeater-Builder@yahoogroups.com Sent: Monday, October 20, 2008 11:17 AM Subject: RE: [Repeater-Builder] UHF Repeater Antenna -- UPDATE DC Grounded, in my experience, means the center pin and the coax will show a dc short when tested with a DMM. Lightning? Corrosion? Manufacturing defect? JS -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater- [EMAIL PROTECTED] On Behalf Of Cort Buffington Sent: Monday, October 20, 2008 11:29 AM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] UHF Repeater Antenna -- UPDATE Folks, *Continuation of Previous Thread: UHF Repeater Antenna Discussion* We climbed the tower on Sunday and checked things with the wattmeter between the Feedline and the antenna. At the bottom, we were making 75 Watts at the duplexer output. At the top, after going through 105' of LDF4.5-50A (just over 1dB of loss), a PolyPhaser, and a 6' jumper of RG400 (from the duplexer to the PolyPhaser) we were seeing 57 Watts. I show that as about 1.2 dB of loss, which seems quite reasonable. The F10, at the top, showed me about 1.5W reflected... or 1.34:1 VSWR. The antenna is a DC grounded colinear, and we showed no measurable (with my DMM) resistance between the center pin and outer conductor of the Hardline/Antenna combination. Right now, we're of the mind that the feedline is good. 73 DE N0MJS -- Cort Buffington H: +1-785-838-3034 M: +1-785-865-7206 -- Cort Buffington H: +1-785-838-3034 M: +1-785-865-7206
Re: [Repeater-Builder] UHF Repeater Antenna -- UPDATE
It is a DC grounded antenna and it measures as a DC short circuit. On Oct 20, 2008, at 7:06 PM, Fred Townsend wrote: It is getting a little blurry here. I hope I can clarify. It is common practice to place a DC ground on the antenna for lightning protection. At frequency the antenna has an impedance of 50 ohms which can not be measured with a DVM. The statement below indicates the antenna has a DC ground but measures open. This would suggest a fault of some kind (either between the headset and ground or at the antenna). Therefore it is legitimate for Mr. Suter to question this statement. de AE6QL, Fred --- [EMAIL PROTECTED] wrote: From: Paul Plack [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] UHF Repeater Antenna -- UPDATE Date: Mon, 20 Oct 2008 16:56:41 -0600 Is not no measureable resistance the same as a short? Zero ohms is just what it should show...why would that indicate damage or defect? - Original Message - From: Jacob Suter To: Repeater-Builder@yahoogroups.com Sent: Monday, October 20, 2008 11:17 AM Subject: RE: [Repeater-Builder] UHF Repeater Antenna -- UPDATE DC Grounded, in my experience, means the center pin and the coax will show a dc short when tested with a DMM. Lightning? Corrosion? Manufacturing defect? JS -Original Message- From: [EMAIL PROTECTED]:Repeater- [EMAIL PROTECTED] On Behalf Of Cort Buffington Sent: Monday, October 20, 2008 11:29 AM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] UHF Repeater Antenna -- UPDATE Folks, *Continuation of Previous Thread: UHF Repeater Antenna Discussion* We climbed the tower on Sunday and checked things with the wattmeter between the Feedline and the antenna. At the bottom, we were making 75 Watts at th e duplexer output. At the top, after going through 105' of LDF4.5-50A (just over 1dB of loss), a PolyPhaser, and a 6' jumper of RG400 (from the duplexer to the PolyPhaser) we were seeing 57 Watts. I show that as about 1.2 dB of loss, which seems quite reasonable. The F10, at the top, showed me about 1.5W reflected... or 1.34:1 VSWR. The antenna is a DC grounded colinear, and we showed no measurable (with my DMM) resistance between the center pin and outer conductor of the Hardline/Antenna combination. Right now, we're of the mind that the feedline is good. 73 DE N0MJS -- Cort Buffington H: +1-785-838-3034 M: +1-785-865-7206 -- Cort Buffington H: +1-785-838-3034 M: +1-785-865-7206
Re: [Repeater-Builder] UHF Repeater Antenna Discussion
[EMAIL PROTECTED] wrote: My 2 cents worth. Many years ago I had a 200' run of LDF5-50 installed by a professional on a 900'tower (rptr at 700' antenna at 900') about a week later we noticed that the TR performance dropped considerably. Personal inspection revealed that water or condensate (about a teaspoon full) had drained down the cable insde the hollow center conductor and had seeped around the inside of the bottom connector. The solution was to completely remove the connector and center pin, drain the cable and let it thoroughly dry then reinstall the connector. I never had another problem with it after that. I suggest you take a look at yours. An issue I've heard come up-if the connector/antenna was installed on a hot, humid day, there will be more water vapor in the air trapped inside. When it cools down, that water will condense out, making it look like it wasn't sealed properly, and of course causing high VSWR. Sometimes putting an antenna up on a hot, humid, sunny day is as bad as putting it up in the rain.
Re: [Repeater-Builder] UHF Repeater Antenna Discussion
Cort Buffington wrote: For you repeater elmers out there: If we don't find a problem with the feedline on the Telewave antenna, does this make any sense? Telewave also HIGHLY recommended that the F10 isn't a good fit for this installation due to its extremely narrow vertical beamwidth, and recommended that a 4-bay dipole of theirs would be MUCH better because of the ability to tune the pattern to our desired coverage area and the increased vertical beamwidth. I always thought I wanted NARROW vertical beamwidth to keep the RF on the horizon. I would have thought that 100' up on relatively high ground (this is Kansas, after all) wouldn't have a real problem shooting over the top 10 - 30 miles away. You're correct. At 100', you won't have a problem. Now if you were up 1000', you might want some downtilt. As far as spacing in a side-mount situation, if you want an omni pattern, you will want to be about one-wavelength out from the tower leg. That gets fairly close to an omni pattern. Spacing of 1/4-wave will put a notch in the pattern through the tower, a half-wave will give you 2 lobes perpendicular to the tower, and 3/4 wave will give you 3 lobes arranged away from the tower in a kind of 'clover-leaf' pattern.
Re: [Repeater-Builder] UHF Repeater Antenna Discussion
Cort, It sounds like a mechanical problem somewhere, as others have mentioned. If you can get your hands on a TDR or similar device to sweep the new antenna and feedline on top (using calibrated 50 ohm load on the feedline, and then adding the antenna on for the next test), you'll probably find the problem. If you can't borrow that kind of gear, perhaps a jumper from the bottom feedline to the top antenna to see if it changes the performance would help you figure out if the problem is the new Telewave antenna, or the feedline going to it. Remember, the wattmeter at the transmitter will show good SWR if something is eating the RF but not radiating it. You may also want to consider sending someone up the tower with the wattmeter and seeing what's going on right at the input to the antenna, if all you have is the wattmeter for test gear. The key thing to remember is that the numbers should match theory, or be real close to it. If you're putting in X amount of power at the transmitter, and you know the feedline loss numbers, you can calculate for what you should see at the base of the antenna measurement. If the RF isn't getting there, you know it's a problem in the hardline. If it is getting there but you have high SWR at the antenna base, something is physically wrong with the new antenna, a connector, something... I think from this text and the replies of others, you can come up with a plan that will eliminate a section at a time... if you have jumpers inside the building to the outside, test those (a high power dummy load is nice here, if you have one that you know is a solid 50 ohm load, and not a hunk of junk that's reactive or cheap -- I like the big Bird dummy loads for this part of the job), test just beyond the Polyphaser (a friend had one show up bad from the factory lately), etc... all depending on how much stuff you have between the TX and the antenna... test at every point. Somewhere you'll find it all falls apart according to the numbers... or... if you don't, the antenna's got problems. At that point, jumper over to the other antenna with a nice solid piece of LMR-400 or better, and see if it behaves normally -- you'll find it! There's an art to finding this type of problem, but it's all based in feedline and antenna theory... if you know what the numbers SHOULD be at each test point, you're WAY ahead of the game. Make up a diagram and calculate feedline losses to each point, etc... it'll make it pretty obvious where the RF is disappearing if there's a mechanical/connection problem or a bad antenna. I'm no RF pro, but the pros I've learned from over the years would all tackle this problem this way... find the place where the theoretical RF behavior falls apart, and you've found the problem, most likely. It's better than just shotgunning in new gear until the problem is fixed. Nate WY0X
Re: [Repeater-Builder] UHF Repeater Antenna Discussion
I'll keep the list posted on what we find. I'm playing it all by the numbers, and I don't have access to a TDR. Calculate and measure, one step at a time is my plan. Sooner or later if we don't find a problem, we plan to replace the Telewave F10 with another DB420 we have and if that works well, consider a problem with the F10. I'm now wise to looking very closely at hardline fittings, and have realized the DC grounded antenna trick, etc. All of the responses here have added additional emphasis or new tricks to try -- Please keep them coming, but I'm probably going to keep them filed and wait for some more testing for a reply on the list. Now the thing I do want to emphasize is that Telewave has been incredibly responsive to us and has not put unreasonable burden on us to prove the F10 is bad before taking it back -- I have no proof of this yet, or reason to think it's the F10, I just want everyone to know that Telewave has been a real class act when I've called them. I was immediately put in touch with John Hilmer, the director of their antenna division, and he has been keeping in touch via e-mail. It is clear that even just one pair of hams buying one antenna is important to them. 73 for now! Cort (N0MJS) On Oct 17, 2008, at 12:26 PM, Nate Duehr wrote: Cort, It sounds like a mechanical problem somewhere, as others have mentioned. If you can get your hands on a TDR or similar device to sweep the new antenna and feedline on top (using calibrated 50 ohm load on the feedline, and then adding the antenna on for the next test), you'll probably find the problem. If you can't borrow that kind of gear, perhaps a jumper from the bottom feedline to the top antenna to see if it changes the performance would help you figure out if the problem is the new Telewave antenna, or the feedline going to it. Remember, the wattmeter at the transmitter will show good SWR if something is eating the RF but not radiating it. You may also want to consider sending someone up the tower with the wattmeter and seeing what's going on right at the input to the antenna, if all you have is the wattmeter for test gear. The key thing to remember is that the numbers should match theory, or be real close to it. If you're putting in X amount of power at the transmitter, and you know the feedline loss numbers, you can calculate for what you should see at the base of the antenna measurement. If the RF isn't getting there, you know it's a problem in the hardline. If it is getting there but you have high SWR at the antenna base, something is physically wrong with the new antenna, a connector, something... I think from this text and the replies of others, you can come up with a plan that will eliminate a section at a time... if you have jumpers inside the building to the outside, test those (a high power dummy load is nice here, if you have one that you know is a solid 50 ohm load, and not a hunk of junk that's reactive or cheap -- I like the big Bird dummy loads for this part of the job), test just beyond the Polyphaser (a friend had one show up bad from the factory lately), etc... all depending on how much stuff you have between the TX and the antenna... test at every point. Somewhere you'll find it all falls apart according to the numbers... or... if you don't, the antenna's got problems. At that point, jumper over to the other antenna with a nice solid piece of LMR-400 or better, and see if it behaves normally -- you'll find it! There's an art to finding this type of problem, but it's all based in feedline and antenna theory... if you know what the numbers SHOULD be at each test point, you're WAY ahead of the game. Make up a diagram and calculate feedline losses to each point, etc... it'll make it pretty obvious where the RF is disappearing if there's a mechanical/connection problem or a bad antenna. I'm no RF pro, but the pros I've learned from over the years would all tackle this problem this way... find the place where the theoretical RF behavior falls apart, and you've found the problem, most likely. It's better than just shotgunning in new gear until the problem is fixed. Nate WY0X -- Cort Buffington H: +1-785-838-3034 M: +1-785-865-7206 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: mailto:[EMAIL PROTECTED] mailto:[EMAIL PROTECTED] * 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/
[Repeater-Builder] UHF Repeater Antenna Discussion
Folks, My repeater partner and I have recently placed our new 440 machine. We have realized some odd issues. We bought a new Telewave ANT450F10 to put on top of the 100' tower, fed with a new piece of Andrew 5/8 heliax. We also side-mounted an old DB420 with the top a few feet down from the top of the tower with about 85' of old 7/8 Andrew heliax. So, we put smokin' new gear on top, and smokin old below it. The DB420 is spaced correctly from the tower and is set up with each half 90 degrees rotated. The tower is on relatively high pasture land (for NE Kansas anyway) with a nice clear view all around. I'll not say we're on a hill, but on relatively high ground. We are attempting to cover two towns approximately 25 miles apart. We are 1/3 of the way from town 1 to town 2 and about 3 miles N of the highway that pretty much is a straight shot connecting them. The Telewave setup on top performs poorly. The DB420 on the side is working great. By this difference, I mean signals that are getting in full quieting on the DB420 are very noisy on the Telewave. Transmit differences mirror receive. S9 reception on the DB420, switch to the Telewave and it's S1-S3. We experience this phenomenon in all directions. Wattmeter (yes, it is a real one -- Telewave 44) says that things look good as far as loading both antennas -- DB420 is 1.43:1, F10 is 1.39:1. We are about to climb and take readings at the top to make sure there is no feed problem with the Telewave 'F10, and I admit that has not been done yet. We did have a discussion with Telewave, who advised that vertical alignment of the F10 (as they refer to it) is critical. We have checked alignment and even implemented a little down- tilt in the most important direction (just a few degrees). We see not real appreciable difference. For you repeater elmers out there: If we don't find a problem with the feedline on the Telewave antenna, does this make any sense? Telewave also HIGHLY recommended that the F10 isn't a good fit for this installation due to its extremely narrow vertical beamwidth, and recommended that a 4-bay dipole of theirs would be MUCH better because of the ability to tune the pattern to our desired coverage area and the increased vertical beamwidth. I always thought I wanted NARROW vertical beamwidth to keep the RF on the horizon. I would have thought that 100' up on relatively high ground (this is Kansas, after all) wouldn't have a real problem shooting over the top 10 - 30 miles away. In any event I seek advice and wisdom, and yes, we are planning to check the coax for loss at the earliest convenience. I would like to take advantage of the top slot on the tower for improved performance rather than stay on the lower spot, and will try another antenna if necessary. I'm just having a hard time imagining that the F10 has appreciably narrower vertical beam as a 9.something dBd antenna than the F10 as a 10dBd antenna, etc. etc. And it also seems counter intuitive that a taller vertical beamwidth and less gain on the horizon in this application would be better. I trust the experience and knowledge of Telewave, but I also trust the wisdom from this list, which has saved me many times. Your thoughts gentlemen? -- Cort Buffington H: +1-785-838-3034 M: +1-785-865-7206
RE: [Repeater-Builder] UHF Repeater Antenna Discussion
Cort, Do you really have 5/8 ? Here are the part numbers for the coax LDF4-50A 1/2 50 ohms - loss at 450MHz ~1.447 LDF5-50A 7/8 50 ohms - loss at 450MHz ~ .808 LDF6-50A 1 1/4 50 ohms LDF7-50A 1 5/8 50 ohms So if you have the real deal feed line loss doesn't look like your problem If you have something else all bets are off send me what number is on the cable. The Telewave antenna (actuality ANY Telewave antenna) is problematic. We tried using several in the paging business most likely for the same reason you did they are cheap. They never performed as well as advertised. If you want a cheap antenna the best for the money is and ASP705K by Decibel Products (or whatever they are this week) They work well have a nice round pattern. And will generally out perform a DB-420 because of less pattern distortion. The statement The DB420 is spaced correctly from the tower concerns me as there is no correct way to side mount an antenna. You must take in to account the desired v. undesired coverage areas and optimize the mount and elements to achieve the desired coverage. On that antenna with an 18 face tower mounted 16 off the point of the tower set in an omni configuration You will see peaks of around 10.5dBd and nulls of around 5dBd. I see nothing here that would indicate that the Telewave system is performing correctly. Remember to take into the feed line loss when calculating SWR. That is if you are putting a 100 watts into the feed line and get 50 watts back That indicates a fault at the top as you have 100 watts and 2.894dB loss (1.447*2 up and down) that would be half power of 50 watts. Do some more looking before you call the antenna bad. Robert / KD4PBC -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Cort Buffington Sent: Thursday, October 16, 2008 9:17 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] UHF Repeater Antenna Discussion Folks, My repeater partner and I have recently placed our new 440 machine. We have realized some odd issues. We bought a new Telewave ANT450F10 to put on top of the 100' tower, fed with a new piece of Andrew 5/8 heliax. We also side-mounted an old DB420 with the top a few feet down from the top of the tower with about 85' of old 7/8 Andrew heliax. So, we put smokin' new gear on top, and smokin old below it. The DB420 is spaced correctly from the tower and is set up with each half 90 degrees rotated. The tower is on relatively high pasture land (for NE Kansas anyway) with a nice clear view all around. I'll not say we're on a hill, but on relatively high ground. We are attempting to cover two towns approximately 25 miles apart. We are 1/3 of the way from town 1 to town 2 and about 3 miles N of the highway that pretty much is a straight shot connecting them. The Telewave setup on top performs poorly. The DB420 on the side is working great. By this difference, I mean signals that are getting in full quieting on the DB420 are very noisy on the Telewave. Transmit differences mirror receive. S9 reception on the DB420, switch to the Telewave and it's S1-S3. We experience this phenomenon in all directions. Wattmeter (yes, it is a real one -- Telewave 44) says that things look good as far as loading both antennas -- DB420 is 1.43:1, F10 is 1.39:1. We are about to climb and take readings at the top to make sure there is no feed problem with the Telewave 'F10, and I admit that has not been done yet. We did have a discussion with Telewave, who advised that vertical alignment of the F10 (as they refer to it) is critical. We have checked alignment and even implemented a little down- tilt in the most important direction (just a few degrees). We see not real appreciable difference. For you repeater elmers out there: If we don't find a problem with the feedline on the Telewave antenna, does this make any sense? Telewave also HIGHLY recommended that the F10 isn't a good fit for this installation due to its extremely narrow vertical beamwidth, and recommended that a 4-bay dipole of theirs would be MUCH better because of the ability to tune the pattern to our desired coverage area and the increased vertical beamwidth. I always thought I wanted NARROW vertical beamwidth to keep the RF on the horizon. I would have thought that 100' up on relatively high ground (this is Kansas, after all) wouldn't have a real problem shooting over the top 10 - 30 miles away. In any event I seek advice and wisdom, and yes, we are planning to check the coax for loss at the earliest convenience. I would like to take advantage of the top slot on the tower for improved performance rather than stay on the lower spot, and will try another antenna if necessary. I'm just having a hard time imagining that the F10 has appreciably narrower vertical beam as a 9.something dBd antenna than the F10 as a 10dBd antenna, etc. etc. And it also seems
Re: [Repeater-Builder] UHF Repeater Antenna Discussion
Cort, I need to understand if I have all the information correct from your post. One 440 machine. One duplexer. Two antennas connected to two feedlines which can either be terminated to the duplexer as you so desire? Only one feedline to one antenna, not coupled or combined in any way? One hardline / antenna works good (DB420) and one hardline / antenna (Telewave ANT450F10) works bad? The first step is to verify the Telewave wattmeter. I'd get a hold of a Bird 43 or equivalent and verify your readings. That's the easiest thing to do. If your forward / reverse numbers are accurate then I'd suspect the Telewave system or it's hardline, unless proven otherwise. You need to rule out either the antenna or the hardline by substitution, and one at a time. Possible issues could be bad connectors either at the antenna base or duplexer termination. How long ago was the antenna system put up? Was there some heavy rain in the area that water could have been introduced into the connector / hardline if they weren't properly water-proofed? Unless someone contradicts me here, I'm having a hard time believing that the vertical alignment of the Telewave is critical. In re-reading your post over a couple of times I'm wondering when you checked the alignment and then implemented a little down-tilt you may have done something wrong to cause the hardline / antenna system to react that way. Keep us posted and good luck with finding out the problem. Don, KD9PT - Original Message - From: Cort Buffington [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Thursday, October 16, 2008 8:16 PM Subject: [Repeater-Builder] UHF Repeater Antenna Discussion Folks, My repeater partner and I have recently placed our new 440 machine. We have realized some odd issues. We bought a new Telewave ANT450F10 to put on top of the 100' tower, fed with a new piece of Andrew 5/8 heliax. We also side-mounted an old DB420 with the top a few feet down from the top of the tower with about 85' of old 7/8 Andrew heliax. So, we put smokin' new gear on top, and smokin old below it. The DB420 is spaced correctly from the tower and is set up with each half 90 degrees rotated. The tower is on relatively high pasture land (for NE Kansas anyway) with a nice clear view all around. I'll not say we're on a hill, but on relatively high ground. We are attempting to cover two towns approximately 25 miles apart. We are 1/3 of the way from town 1 to town 2 and about 3 miles N of the highway that pretty much is a straight shot connecting them. The Telewave setup on top performs poorly. The DB420 on the side is working great. By this difference, I mean signals that are getting in full quieting on the DB420 are very noisy on the Telewave. Transmit differences mirror receive. S9 reception on the DB420, switch to the Telewave and it's S1-S3. We experience this phenomenon in all directions. Wattmeter (yes, it is a real one -- Telewave 44) says that things look good as far as loading both antennas -- DB420 is 1.43:1, F10 is 1.39:1. We are about to climb and take readings at the top to make sure there is no feed problem with the Telewave 'F10, and I admit that has not been done yet. We did have a discussion with Telewave, who advised that vertical alignment of the F10 (as they refer to it) is critical. We have checked alignment and even implemented a little down- tilt in the most important direction (just a few degrees). We see not real appreciable difference. For you repeater elmers out there: If we don't find a problem with the feedline on the Telewave antenna, does this make any sense? Telewave also HIGHLY recommended that the F10 isn't a good fit for this installation due to its extremely narrow vertical beamwidth, and recommended that a 4-bay dipole of theirs would be MUCH better because of the ability to tune the pattern to our desired coverage area and the increased vertical beamwidth. I always thought I wanted NARROW vertical beamwidth to keep the RF on the horizon. I would have thought that 100' up on relatively high ground (this is Kansas, after all) wouldn't have a real problem shooting over the top 10 - 30 miles away. In any event I seek advice and wisdom, and yes, we are planning to check the coax for loss at the earliest convenience. I would like to take advantage of the top slot on the tower for improved performance rather than stay on the lower spot, and will try another antenna if necessary. I'm just having a hard time imagining that the F10 has appreciably narrower vertical beam as a 9.something dBd antenna than the F10 as a 10dBd antenna, etc. etc. And it also seems counter intuitive that a taller vertical beamwidth and less gain on the horizon in this application would be better. I trust the experience and knowledge of Telewave, but I also trust the wisdom from this list, which has saved me many times. Your thoughts gentlemen? -- Cort Buffington
Re: [Repeater-Builder] UHF Repeater Antenna Discussion
LDF4.5-50A http://www.tessco.com/products/displayProductInfo.do?sku=466137eventGroup=4eventPage=1 1.05dB loss at 450MHz @ 100' DB420 spacing -- spacing and mounting per DB Products/Andrew/ComScope, etc. :) instructions, I agree, it's never perfect, just wanted to be clear that it is all by the book. Will keep looking -- measuring power at the feedline-antenna connection is my next step. Thanks for the input Robert -- this helps! On Oct 16, 2008, at 9:18 PM, KD4PBC wrote: Cort, Do you really have 5/8 ? Here are the part numbers for the coax LDF4-50A 1/2 50 ohms - loss at 450MHz ~1.447 LDF5-50A 7/8 50 ohms - loss at 450MHz ~ .808 LDF6-50A 1 1/4 50 ohms LDF7-50A 1 5/8 50 ohms So if you have the real deal feed line loss doesn't look like your problem If you have something else all bets are off send me what number is on the cable. The Telewave antenna (actuality ANY Telewave antenna) is problematic. We tried using several in the paging business most likely for the same reason you did they are cheap. They never performed as well as advertised. If you want a cheap antenna the best for the money is and ASP705K by Decibel Products (or whatever they are this week) They work well have a nice round pattern. And will generally out perform a DB-420 because of less pattern distortion. The statement The DB420 is spaced correctly from the tower concerns me as there is no correct way to side mount an antenna. You must take in to account the desired v. undesired coverage areas and optimize the mount and elements to achieve the desired coverage. On that antenna with an 18 face tower mounted 16 off the point of the tower set in an omni configuration You will see peaks of around 10.5dBd and nulls of around 5dBd. I see nothing here that would indicate that the Telewave system is performing correctly. Remember to take into the feed line loss when calculating SWR. That is if you are putting a 100 watts into the feed line and get 50 watts back That indicates a fault at the top as you have 100 watts and 2.894dB loss (1.447*2 up and down) that would be half power of 50 watts. Do some more looking before you call the antenna bad. Robert / KD4PBC -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Cort Buffington Sent: Thursday, October 16, 2008 9:17 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] UHF Repeater Antenna Discussion Folks, My repeater partner and I have recently placed our new 440 machine. We have realized some odd issues. We bought a new Telewave ANT450F10 to put on top of the 100' tower, fed with a new piece of Andrew 5/8 heliax. We also side-mounted an old DB420 with the top a few feet down from the top of the tower with about 85' of old 7/8 Andrew heliax. So, we put smokin' new gear on top, and smokin old below it. The DB420 is spaced correctly from the tower and is set up with each half 90 degrees rotated. The tower is on relatively high pasture land (for NE Kansas anyway) with a nice clear view all around. I'll not say we're on a hill, but on relatively high ground. We are attempting to cover two towns approximately 25 miles apart. We are 1/3 of the way from town 1 to town 2 and about 3 miles N of the highway that pretty much is a straight shot connecting them. The Telewave setup on top performs poorly. The DB420 on the side is working great. By this difference, I mean signals that are getting in full quieting on the DB420 are very noisy on the Telewave. Transmit differences mirror receive. S9 reception on the DB420, switch to the Telewave and it's S1-S3. We experience this phenomenon in all directions. Wattmeter (yes, it is a real one -- Telewave 44) says that things look good as far as loading both antennas -- DB420 is 1.43:1, F10 is 1.39:1. We are about to climb and take readings at the top to make sure there is no feed problem with the Telewave 'F10, and I admit that has not been done yet. We did have a discussion with Telewave, who advised that vertical alignment of the F10 (as they refer to it) is critical. We have checked alignment and even implemented a little down- tilt in the most important direction (just a few degrees). We see not real appreciable difference. For you repeater elmers out there: If we don't find a problem with the feedline on the Telewave antenna, does this make any sense? Telewave also HIGHLY recommended that the F10 isn't a good fit for this installation due to its extremely narrow vertical beamwidth, and recommended that a 4-bay dipole of theirs would be MUCH better because of the ability to tune the pattern to our desired coverage area and the increased vertical beamwidth. I always thought I wanted NARROW vertical beamwidth to keep the RF on the horizon. I would have thought that 100' up on relatively high ground (this is Kansas, after all) wouldn't have a real problem shooting over the top 10 - 30 miles away. In any event I seek advice and wisdom, and yes
Re: [Repeater-Builder] UHF Repeater Antenna Discussion
Don, two completely different antenna and feedline systems. I swap them where each separate antenna/feedline system connects to the duplexer. The Telewave meter is new because I didn't trust my ham-type meters... (I've needed a real meter for years anyway) The Telewave shows a little less forward power and a little lower VSWR than the cheap comets. I did a quick check of the telewave by transmitting various signal levels into my IFR 1200S (currently in calibration from Aeroflex) I then transmitted the same signals into the telewave with a nice big DB load I've trusted for years on it. The Telewave was within a few % of the IFR. I know that's not a perfect method, but new meter, agrees with IFR in my limited testing format. I'm probably pretty confident of it. Problems before and after vertical alignment. If the feedline/ connector is damaged it was damaged when we put this system up -- from tower on the ground. I mean, we did it ALL three weeks ago. Saturday morning there was a pile of parts, by sundown it was all assembled and installed. No rain at all between erection and the first round of testing. After significant rains, no change. Thanks Don! Cort On Oct 16, 2008, at 9:24 PM, Don Kupferschmidt wrote: Cort, I need to understand if I have all the information correct from your post. One 440 machine. One duplexer. Two antennas connected to two feedlines which can either be terminated to the duplexer as you so desire? Only one feedline to one antenna, not coupled or combined in any way? One hardline / antenna works good (DB420) and one hardline / antenna (Telewave ANT450F10) works bad? The first step is to verify the Telewave wattmeter. I'd get a hold of a Bird 43 or equivalent and verify your readings. That's the easiest thing to do. If your forward / reverse numbers are accurate then I'd suspect the Telewave system or it's hardline, unless proven otherwise. You need to rule out either the antenna or the hardline by substitution, and one at a time. Possible issues could be bad connectors either at the antenna base or duplexer termination. How long ago was the antenna system put up? Was there some heavy rain in the area that water could have been introduced into the connector / hardline if they weren't properly water-proofed? Unless someone contradicts me here, I'm having a hard time believing that the vertical alignment of the Telewave is critical. In re-reading your post over a couple of times I'm wondering when you checked the alignment and then implemented a little down-tilt you may have done something wrong to cause the hardline / antenna system to react that way. Keep us posted and good luck with finding out the problem. Don, KD9PT - Original Message - From: Cort Buffington [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Thursday, October 16, 2008 8:16 PM Subject: [Repeater-Builder] UHF Repeater Antenna Discussion Folks, My repeater partner and I have recently placed our new 440 machine. We have realized some odd issues. We bought a new Telewave ANT450F10 to put on top of the 100' tower, fed with a new piece of Andrew 5/8 heliax. We also side-mounted an old DB420 with the top a few feet down from the top of the tower with about 85' of old 7/8 Andrew heliax. So, we put smokin' new gear on top, and smokin old below it. The DB420 is spaced correctly from the tower and is set up with each half 90 degrees rotated. The tower is on relatively high pasture land (for NE Kansas anyway) with a nice clear view all around. I'll not say we're on a hill, but on relatively high ground. We are attempting to cover two towns approximately 25 miles apart. We are 1/3 of the way from town 1 to town 2 and about 3 miles N of the highway that pretty much is a straight shot connecting them. The Telewave setup on top performs poorly. The DB420 on the side is working great. By this difference, I mean signals that are getting in full quieting on the DB420 are very noisy on the Telewave. Transmit differences mirror receive. S9 reception on the DB420, switch to the Telewave and it's S1-S3. We experience this phenomenon in all directions. Wattmeter (yes, it is a real one -- Telewave 44) says that things look good as far as loading both antennas -- DB420 is 1.43:1, F10 is 1.39:1. We are about to climb and take readings at the top to make sure there is no feed problem with the Telewave 'F10, and I admit that has not been done yet. We did have a discussion with Telewave, who advised that vertical alignment of the F10 (as they refer to it) is critical. We have checked alignment and even implemented a little down- tilt in the most important direction (just a few degrees). We see not real appreciable difference. For you repeater elmers out there: If we don't find a problem with the feedline on the Telewave antenna, does this make any sense? Telewave also HIGHLY recommended
Re: [Repeater-Builder] UHF Repeater Antenna Discussion
Could be a bad-out-of-the-box antenna. I've heard of this happening with fiberglass antennas. It could be broken near the bottom and still show good VSWR but give you no gain. Chuck WB2EDV - Original Message - From: Cort Buffington [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Thursday, October 16, 2008 9:16 PM Subject: [Repeater-Builder] UHF Repeater Antenna Discussion Folks, My repeater partner and I have recently placed our new 440 machine. We have realized some odd issues. We bought a new Telewave ANT450F10 to put on top of the 100' tower, fed with a new piece of Andrew 5/8 heliax. We also side-mounted an old DB420 with the top a few feet down from the top of the tower with about 85' of old 7/8 Andrew heliax. So, we put smokin' new gear on top, and smokin old below it. The DB420 is spaced correctly from the tower and is set up with each half 90 degrees rotated. The tower is on relatively high pasture land (for NE Kansas anyway) with a nice clear view all around. I'll not say we're on a hill, but on relatively high ground. We are attempting to cover two towns approximately 25 miles apart. We are 1/3 of the way from town 1 to town 2 and about 3 miles N of the highway that pretty much is a straight shot connecting them. The Telewave setup on top performs poorly. The DB420 on the side is working great. By this difference, I mean signals that are getting in full quieting on the DB420 are very noisy on the Telewave. Transmit differences mirror receive. S9 reception on the DB420, switch to the Telewave and it's S1-S3. We experience this phenomenon in all directions. Wattmeter (yes, it is a real one -- Telewave 44) says that things look good as far as loading both antennas -- DB420 is 1.43:1, F10 is 1.39:1. We are about to climb and take readings at the top to make sure there is no feed problem with the Telewave 'F10, and I admit that has not been done yet. We did have a discussion with Telewave, who advised that vertical alignment of the F10 (as they refer to it) is critical. We have checked alignment and even implemented a little down- tilt in the most important direction (just a few degrees). We see not real appreciable difference. For you repeater elmers out there: If we don't find a problem with the feedline on the Telewave antenna, does this make any sense? Telewave also HIGHLY recommended that the F10 isn't a good fit for this installation due to its extremely narrow vertical beamwidth, and recommended that a 4-bay dipole of theirs would be MUCH better because of the ability to tune the pattern to our desired coverage area and the increased vertical beamwidth. I always thought I wanted NARROW vertical beamwidth to keep the RF on the horizon. I would have thought that 100' up on relatively high ground (this is Kansas, after all) wouldn't have a real problem shooting over the top 10 - 30 miles away. In any event I seek advice and wisdom, and yes, we are planning to check the coax for loss at the earliest convenience. I would like to take advantage of the top slot on the tower for improved performance rather than stay on the lower spot, and will try another antenna if necessary. I'm just having a hard time imagining that the F10 has appreciably narrower vertical beam as a 9.something dBd antenna than the F10 as a 10dBd antenna, etc. etc. And it also seems counter intuitive that a taller vertical beamwidth and less gain on the horizon in this application would be better. I trust the experience and knowledge of Telewave, but I also trust the wisdom from this list, which has saved me many times. Your thoughts gentlemen? -- Cort Buffington H: +1-785-838-3034 M: +1-785-865-7206
RE: [Repeater-Builder] UHF Repeater Antenna Discussion
Cort, One problem that I don't think has been mentioned, is the possibility that the center conductor of the feedline to the top antenna has somehow disconnected from the center pin at the top end. This doesn't happen very often with foam dielectric Heliax, but it does happen often with air dielectric feedline. When the sun beats on the black exterior of the feedline, it expands longitudinally, but more on the outside than on the inside. After many cycles, the center conductor pulls out of the back of the center pin. On captive-pin Heliax connectors, it looks like the center pin is fine when viewed from the top, but there may be no connection to the cable's center conductor. One quick way to check this is to measure the DC resistance between the center conductor and shield at the bottom end of the feedline, where it connects to the duplexer. When a DC-grounded is properly connected at the top, you should measure close to zero ohms plus the loop resistance of the feedline. Incidentally, this quick and simple measurement is a good one to make on any new installation, right after it is certain that everything is working properly. The measured resistance value should be posted somewhere in the shack so that it can be verified from time to time, or when there is a suspected problem with the antenna or feedline. 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Cort Buffington Sent: Thursday, October 16, 2008 7:38 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] UHF Repeater Antenna Discussion Don, two completely different antenna and feedline systems. I swap them where each separate antenna/feedline system connects to the duplexer. The Telewave meter is new because I didn't trust my ham-type meters... (I've needed a real meter for years anyway) The Telewave shows a little less forward power and a little lower VSWR than the cheap comets. I did a quick check of the telewave by transmitting various signal levels into my IFR 1200S (currently in calibration from Aeroflex) I then transmitted the same signals into the telewave with a nice big DB load I've trusted for years on it. The Telewave was within a few % of the IFR. I know that's not a perfect method, but new meter, agrees with IFR in my limited testing format. I'm probably pretty confident of it. Problems before and after vertical alignment. If the feedline/connector is damaged it was damaged when we put this system up -- from tower on the ground. I mean, we did it ALL three weeks ago. Saturday morning there was a pile of parts, by sundown it was all assembled and installed. No rain at all between erection and the first round of testing. After significant rains, no change. Thanks Don! Cort On Oct 16, 2008, at 9:24 PM, Don Kupferschmidt wrote: Cort, I need to understand if I have all the information correct from your post. One 440 machine. One duplexer. Two antennas connected to two feedlines which can either be terminated to the duplexer as you so desire? Only one feedline to one antenna, not coupled or combined in any way? One hardline / antenna works good (DB420) and one hardline / antenna (Telewave ANT450F10) works bad? The first step is to verify the Telewave wattmeter. I'd get a hold of a Bird 43 or equivalent and verify your readings. That's the easiest thing to do. If your forward / reverse numbers are accurate then I'd suspect the Telewave system or it's hardline, unless proven otherwise. You need to rule out either the antenna or the hardline by substitution, and one at a time. Possible issues could be bad connectors either at the antenna base or duplexer termination. How long ago was the antenna system put up? Was there some heavy rain in the area that water could have been introduced into the connector / hardline if they weren't properly water-proofed? Unless someone contradicts me here, I'm having a hard time believing that the vertical alignment of the Telewave is critical. In re-reading your post over a couple of times I'm wondering when you checked the alignment and then implemented a little down-tilt you may have done something wrong to cause the hardline / antenna system to react that way. Keep us posted and good luck with finding out the problem. Don, KD9PT - Original Message - From: Cort Buffington [EMAIL PROTECTED] mailto:cort%40lawrence-ks.org To: Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com Sent: Thursday, October 16, 2008 8:16 PM Subject: [Repeater-Builder] UHF Repeater Antenna Discussion Folks, My
Re: [Repeater-Builder] UHF Repeater Antenna Discussion
Eric! That's a really, really fantastic idea. That's TOP on the list. On Oct 16, 2008, at 10:16 PM, Eric Lemmon wrote: Cort, One problem that I don't think has been mentioned, is the possibility that the center conductor of the feedline to the top antenna has somehow disconnected from the center pin at the top end. This doesn't happen very often with foam dielectric Heliax, but it does happen often with air dielectric feedline. When the sun beats on the black exterior of the feedline, it expands longitudinally, but more on the outside than on the inside. After many cycles, the center conductor pulls out of the back of the center pin. On captive-pin Heliax connectors, it looks like the center pin is fine when viewed from the top, but there may be no connection to the cable's center conductor. One quick way to check this is to measure the DC resistance between the center conductor and shield at the bottom end of the feedline, where it connects to the duplexer. When a DC-grounded is properly connected at the top, you should measure close to zero ohms plus the loop resistance of the feedline. Incidentally, this quick and simple measurement is a good one to make on any new installation, right after it is certain that everything is working properly. The measured resistance value should be posted somewhere in the shack so that it can be verified from time to time, or when there is a suspected problem with the antenna or feedline. 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Cort Buffington Sent: Thursday, October 16, 2008 7:38 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] UHF Repeater Antenna Discussion Don, two completely different antenna and feedline systems. I swap them where each separate antenna/feedline system connects to the duplexer. The Telewave meter is new because I didn't trust my ham-type meters... (I've needed a real meter for years anyway) The Telewave shows a little less forward power and a little lower VSWR than the cheap comets. I did a quick check of the telewave by transmitting various signal levels into my IFR 1200S (currently in calibration from Aeroflex) I then transmitted the same signals into the telewave with a nice big DB load I've trusted for years on it. The Telewave was within a few % of the IFR. I know that's not a perfect method, but new meter, agrees with IFR in my limited testing format. I'm probably pretty confident of it. Problems before and after vertical alignment. If the feedline/ connector is damaged it was damaged when we put this system up -- from tower on the ground. I mean, we did it ALL three weeks ago. Saturday morning there was a pile of parts, by sundown it was all assembled and installed. No rain at all between erection and the first round of testing. After significant rains, no change. Thanks Don! Cort On Oct 16, 2008, at 9:24 PM, Don Kupferschmidt wrote: Cort, I need to understand if I have all the information correct from your post. One 440 machine. One duplexer. Two antennas connected to two feedlines which can either be terminated to the duplexer as you so desire? Only one feedline to one antenna, not coupled or combined in any way? One hardline / antenna works good (DB420) and one hardline / antenna (Telewave ANT450F10) works bad? The first step is to verify the Telewave wattmeter. I'd get a hold of a Bird 43 or equivalent and verify your readings. That's the easiest thing to do. If your forward / reverse numbers are accurate then I'd suspect the Telewave system or it's hardline, unless proven otherwise. You need to rule out either the antenna or the hardline by substitution, and one at a time. Possible issues could be bad connectors either at the antenna base or duplexer termination. How long ago was the antenna system put up? Was there some heavy rain in the area that water could have been introduced into the connector / hardline if they weren't properly water-proofed? Unless someone contradicts me here, I'm having a hard time believing that the vertical alignment of the Telewave is critical. In re-reading your post over a couple of times I'm wondering when you checked the alignment and then implemented a little down-tilt you may have done something wrong to cause the hardline / antenna system to react that way. Keep us posted and good luck with finding out the problem. Don, KD9PT - Original Message - From: Cort Buffington [EMAIL PROTECTED] mailto:cort%40lawrence-ks.org To: Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com Sent: Thursday, October 16, 2008 8:16 PM Subject: [Repeater-Builder] UHF Repeater Antenna Discussion Folks, My repeater partner and I have recently placed our new 440 machine. We have realized some odd issues. We bought a new Telewave ANT450F10 to put on top of the 100' tower, fed with a new piece of Andrew
Re: [Repeater-Builder] UHF Repeater Antenna Discussion
My 2 cents worth. Many years ago I had a 200' run of LDF5-50 installed by a professional on a 900'tower (rptr at 700' antenna at 900') about a week later we noticed that the TR performance dropped considerably. Personal inspection revealed that water or condensate (about a teaspoon full) had drained down the cable insde the hollow center conductor and had seeped around the inside of the bottom connector. The solution was to completely remove the connector and center pin, drain the cable and let it thoroughly dry then reinstall the connector. I never had another problem with it after that. I suggest you take a look at yours. Years later I ordered 2 runs of LDF4-50 w/ connectors installed from DB and after receiving them checked them for continuitybefore installation. One cable showed a direct short between center conductor and ground. I removed both connectors and found one connector had been improperly installed at DB. Apparently the portion that has the spring fingers on it had been allowed to turn in the tightening process and it had grabbed the copper shield, shredded it and bent it inward to where it made contact with the center conductor. Needless to say ,but I then removed all the other connectors to verify their condition and reinstalled all of them properly. A third case similar to the one above (shredded shield ) but no physical contact (no continuity) showed a 1:1 SWR on Xmit but caused the RF to desense the rcvr. to the point where the perfomance of the rptr. was drastically reduced from what it should have been. Similar to what you are describing. While you might not see a direct short or even an indication of high reflected power when you test the system, if you have any contamination, moisture, or metallic debris in side the connector it can cause you the grief you are describing. Hope this helps some. -- Doug N3DAB/WPRX486/WPJL709 Cort Buffington [EMAIL PROTECTED] wrote: = Don, two completely different antenna and feedline systems. I swap them where each separate antenna/feedline system connects to the duplexer. The Telewave meter is new because I didn't trust my ham-type meters... (I've needed a real meter for years anyway) The Telewave shows a little less forward power and a little lower VSWR than the cheap comets. I did a quick check of the telewave by transmitting various signal levels into my IFR 1200S (currently in calibration from Aeroflex) I then transmitted the same signals into the telewave with a nice big DB load I've trusted for years on it. The Telewave was within a few % of the IFR. I know that's not a perfect method, but new meter, agrees with IFR in my limited testing format. I'm probably pretty confident of it. Problems before and after vertical alignment. If the feedline/ connector is damaged it was damaged when we put this system up -- from tower on the ground. I mean, we did it ALL three weeks ago. Saturday morning there was a pile of parts, by sundown it was all assembled and installed. No rain at all between erection and the first round of testing. After significant rains, no change. Thanks Don! Cort On Oct 16, 2008, at 9:24 PM, Don Kupferschmidt wrote: Cort, I need to understand if I have all the information correct from your post. One 440 machine. One duplexer. Two antennas connected to two feedlines which can either be terminated to the duplexer as you so desire? Only one feedline to one antenna, not coupled or combined in any way? One hardline / antenna works good (DB420) and one hardline / antenna (Telewave ANT450F10) works bad? The first step is to verify the Telewave wattmeter. I'd get a hold of a Bird 43 or equivalent and verify your readings. That's the easiest thing to do. If your forward / reverse numbers are accurate then I'd suspect the Telewave system or it's hardline, unless proven otherwise. You need to rule out either the antenna or the hardline by substitution, and one at a time. Possible issues could be bad connectors either at the antenna base or duplexer termination. How long ago was the antenna system put up? Was there some heavy rain in the area that water could have been introduced into the connector / hardline if they weren't properly water-proofed? Unless someone contradicts me here, I'm having a hard time believing that the vertical alignment of the Telewave is critical. In re-reading your post over a couple of times I'm wondering when you checked the alignment and then implemented a little down-tilt you may have done something wrong to cause the hardline / antenna system to react that way. Keep us posted and good luck with finding out the problem. Don, KD9PT - Original Message - From: Cort Buffington [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Thursday, October 16, 2008 8:16 PM Subject: [Repeater-Builder] UHF Repeater Antenna
Re: [Spam] Re: [Repeater-Builder] UHF Repeater Antennas (combining threads)
Very interesting I have one db-224 installed on the catwalk of a water tank. All the dipoles are on the same side of the mast facing away from the tank. It works super that way as intended. The surprising thing to me is how far on the other side of the water tank it will actually talk. The antenna is completely eclipsed by the water tank to the west, yet it talks very well up to about 7 or 8 miles, then drops completely out. I wouldn't think it would go 2 miles, much less 7. My reasoning in moving the dipoles away from the mast was soley to affect the match at lower frequencies. Mine is acceptable down to about 147.2 and then it gets ugly. At 147.225 it has a 1.8-1 match and certainly I can live with that. I tried adding length to the dipoles by cutting them and sliding in the next smaller sized tubing sacrificed from a db-420. Surprisingly, it hurt the match, not helped. I concluded that the harness must have as much to do with the match as dipole lenghts. I then decided to inquire about moving the dipoles away from the mast an inch or two to affect the match, not considering how it might affect the radiation pattern. I have enought db-224 parts to make a db-228 or create a vhf version of the db-408 (would that be a db-208?). Would the pattern be bad if I created the db-208 with incresed spacing for the match? What do you say? Anyone? - Original Message - From: Repeater-Builder@yahoogroups.com Repeater-Builder@yahoogroups.com To: Repeater-Builder@yahoogroups.com Repeater-Builder@yahoogroups.com Sent: Mon Aug 25 22:34:13 2008 Subject: Re: [Spam] Re: [Repeater-Builder] UHF Repeater Antennas (combining threads) If you extend the dipoles further from the mast, you will loose the capability to stagger the dipoles around the mast to obtain omni coverage. Even with the close spaced dipoles there is a slight scaloping of the vertical angle as you go around 360 degrees. The further out the dipoles are placed, the more variation in the vertical angle you will see. Back when the FCC required an antenna pattern for licensing a repeater, I put a DB-224 on a mast and ran it through an antenna range, and observed the scaloping. From that time on I have always prefered to put all the dipoles on the same side of the mast and accept the 3 dB offset in antenna gain. The plot is perfectly circular, but the center is offset with the aligned dipoles. Gain is only 3 dB off the back of the mast but is 9 dB in the direction the dipoles are pointing. And there is no scaloping in the vertical angle at all - 73 - Jim W5ZIT --- On Mon, 8/25/08, NORM KNAPP [EMAIL PROTECTED] wrote: From: NORM KNAPP [EMAIL PROTECTED] Subject: Re: [Spam] Re: [Repeater-Builder] UHF Repeater Antennas (combining threads) To: Repeater-Builder@yahoogroups.com Date: Monday, August 25, 2008, 4:05 PM What if I added something between the mast and the dipole assembly to increase the distance between the dipole and the mast on the VHF antenna? I have a Cushcraft antenna that looks like a VHF version of a DB-404. The dipoles are a little shoter tip to tip than the ones on a DB-224a but the SWR is good all the way down to 146mhz. The major difference I see is how far from the mast the dipoles are. - Original Message - From: Repeater-Builder@ yahoogroups. com mailto:Repeater-Builder%40yahoogroups.com Repeater-Builder@ yahoogroups. com mailto:Repeater-Builder%40yahoogroups.com To: Repeater-Builder@ yahoogroups. com mailto:Repeater-Builder%40yahoogroups.com Repeater-Builder@ yahoogroups. com mailto:Repeater-Builder%40yahoogroups.com Sent: Mon Aug 25 13:21:44 2008 Subject: [Spam] Re: [Repeater-Builder] UHF Repeater Antennas (combining threads) Thanks Jim -- I have been considering lengthening in such a similar fashion. Did you have any noticeable pattern distortion problems or any other side-effects? On Aug 25, 2008, at 10:36 AM, Jim Brown wrote: I have had good luck modifying VHF antennas cut for the 155 mHz band down into the ham band by adding a short stub to each end of each dipole. I flatten a piece of an old TV antenna that has a round element that is rolled into a tube and put a screw through the flattened end wrapped around the end of each element. After the extension is installed I cut the extension to 2 inches. I don't see why the same idea can't be carried over to the UHF antennas. I would suggest a simple way of adding some length to a 440 element would be to drill a hole through the element on each end and put a brass screw through the hole. You can adjust the length of the extension to center the antenna down in the ham band. I did not modify the harness on my 2 meter antenna conversions, and I doubt you would have to on the 440 antenna. When I modified the VHF
[Spam] Re: [Repeater-Builder] UHF Repeater Antennas (combining threads)
Wow! There is a lot of wisdom on this site, and I certainly appreciate the advice. Thanks, my friends! Question: If I use the folded dipole array, how far away from the mast would be optimum for all-around coverage on 438 Mhz? Steve, XE1UFO a.k.a. KA5SUT
Re: [Spam] Re: [Repeater-Builder] UHF Repeater Antennas (combining threads)
At 8/25/2008 20:34, you wrote: If you extend the dipoles further from the mast, you will loose the capability to stagger the dipoles around the mast to obtain omni coverage. Even with the close spaced dipoles there is a slight scaloping of the vertical angle as you go around 360 degrees. The further out the dipoles are placed, the more variation in the vertical angle you will see. Back when the FCC required an antenna pattern for licensing a repeater, I put a DB-224 on a mast and ran it through an antenna range, and observed the scaloping. From that time on I have always prefered to put all the dipoles on the same side of the mast and accept the 3 dB offset in antenna gain. The plot is perfectly circular, but the center is offset with the aligned dipoles. Gain is only 3 dB off the back of the mast but is 9 dB in the direction the dipoles are pointing. And there is no scaloping in the vertical angle at all - I tried configuring the dipoles of a UHF 4-pole for omni coverage at one site noticed very poor performance. Modeling the antenna in NEC I noticed not only is the pattern scalloped, but the peak gain is lower than the nominal 6 dBd as well. Bob NO6B
[Repeater-Builder] UHF Repeater Antennas (combining threads)
This is why on the UHF arrays the dipoles are paired. Chuck WB2EDV - Original Message - I tried configuring the dipoles of a UHF 4-pole for omni coverage at one site noticed very poor performance. Modeling the antenna in NEC I noticed not only is the pattern scalloped, but the peak gain is lower than the nominal 6 dBd as well. Bob NO6B
Re: [Repeater-Builder] UHF Repeater Antennas (combining threads)
I have had good luck modifying VHF antennas cut for the 155 mHz band down into the ham band by adding a short stub to each end of each dipole. I flatten a piece of an old TV antenna that has a round element that is rolled into a tube and put a screw through the flattened end wrapped around the end of each element. After the extension is installed I cut the extension to 2 inches. I don't see why the same idea can't be carried over to the UHF antennas. I would suggest a simple way of adding some length to a 440 element would be to drill a hole through the element on each end and put a brass screw through the hole. You can adjust the length of the extension to center the antenna down in the ham band. I did not modify the harness on my 2 meter antenna conversions, and I doubt you would have to on the 440 antenna. When I modified the VHF dipoles, I removed one dipole and connected my SWR meter to the dipole terminals and found the center frequency. It turned out to be 155 mHz in my case. I then experimented with the extensions until I got the dipole down to 146 mHz and found the extension to be 2 inches. I would suggest that you do the same, and when you find the extension for the one dipole to get it down to 445 mHz, add the same length screw to each of the other dipole ends. Using a #8 or #10 screw might do the trick. I would allow it to stick through the dipole at least an inch, and see where the center frequency of the dipole winds up and adjust the length to center the frequency where you want it. The dipole may not be 50 ohm, as I recall my VHF dipoles were showing about 100 ohms at resonance, so just move the SWR minimum to where you want it by adjusting the screw length and reattach the feedline harness. 73 - Jim W5ZIT --- On Sun, 8/24/08, Cort Buffington [EMAIL PROTECTED] wrote: From: Cort Buffington [EMAIL PROTECTED] Subject: [Repeater-Builder] UHF Repeater Antennas (combining threads) To: Repeater-Builder@yahoogroups.com Date: Sunday, August 24, 2008, 4:30 PM Folks, I have a similar question about UHF Amateur repeater antennas so I'll try to combine threads if possible. I just tested my two DB-420s with freshly re-taped harnesses and cleaned up connections, etc. I'm getting somewhere around 1.7:1 to 1.8:1 VSWR on 444.825, the repeater transmit frequency. Here are my ponderings to the combined wisdom of the group (religious and highly opinionated advice welcomed). The advice here is ALWAYS helpful, so please folks, don't be bashful :) 1) Just use it as is, after I put the 105' of hardline on it and all that'll be good enough? 2) Try some sort of modification to improve performance in the ham band? 3) Ah, forget the 20' tall antenna, just put up a Diamond X50 and call it good? 4) Give up repeater-ing 73 DE N0MJS P.S. repeater location is the top spot on a 100' tower in a rural location that is relatively high terrain. The repeater is meant to cover between two cities 25 miles apart, and is between them. Transmitter is a 100W TPL RXRF that I'd like to run at the 100W. I have remote receive locations and will place remotes and a voter if I can talk loud enough to warrant it. -- Cort Buffington H: +1-785-838-3034 M: +1-785-865-7206
Re: [Repeater-Builder] UHF Repeater Antennas (combining threads)
Thanks Jim -- I have been considering lengthening in such a similar fashion. Did you have any noticeable pattern distortion problems or any other side-effects? On Aug 25, 2008, at 10:36 AM, Jim Brown wrote: I have had good luck modifying VHF antennas cut for the 155 mHz band down into the ham band by adding a short stub to each end of each dipole. I flatten a piece of an old TV antenna that has a round element that is rolled into a tube and put a screw through the flattened end wrapped around the end of each element. After the extension is installed I cut the extension to 2 inches. I don't see why the same idea can't be carried over to the UHF antennas. I would suggest a simple way of adding some length to a 440 element would be to drill a hole through the element on each end and put a brass screw through the hole. You can adjust the length of the extension to center the antenna down in the ham band. I did not modify the harness on my 2 meter antenna conversions, and I doubt you would have to on the 440 antenna. When I modified the VHF dipoles, I removed one dipole and connected my SWR meter to the dipole terminals and found the center frequency. It turned out to be 155 mHz in my case. I then experimented with the extensions until I got the dipole down to 146 mHz and found the extension to be 2 inches. I would suggest that you do the same, and when you find the extension for the one dipole to get it down to 445 mHz, add the same length screw to each of the other dipole ends. Using a #8 or #10 screw might do the trick. I would allow it to stick through the dipole at least an inch, and see where the center frequency of the dipole winds up and adjust the length to center the frequency where you want it. The dipole may not be 50 ohm, as I recall my VHF dipoles were showing about 100 ohms at resonance, so just move the SWR minimum to where you want it by adjusting the screw length and reattach the feedline harness. 73 - Jim W5ZIT --- On Sun, 8/24/08, Cort Buffington [EMAIL PROTECTED] wrote: From: Cort Buffington [EMAIL PROTECTED] Subject: [Repeater-Builder] UHF Repeater Antennas (combining threads) To: Repeater-Builder@yahoogroups.com Date: Sunday, August 24, 2008, 4:30 PM Folks, I have a similar question about UHF Amateur repeater antennas so I'll try to combine threads if possible. I just tested my two DB-420s with freshly re-taped harnesses and cleaned up connections, etc. I'm getting somewhere around 1.7:1 to 1.8:1 VSWR on 444.825, the repeater transmit frequency. Here are my ponderings to the combined wisdom of the group (religious and highly opinionated advice welcomed). The advice here is ALWAYS helpful, so please folks, don't be bashful :) 1) Just use it as is, after I put the 105' of hardline on it and all that'll be good enough? 2) Try some sort of modification to improve performance in the ham band? 3) Ah, forget the 20' tall antenna, just put up a Diamond X50 and call it good? 4) Give up repeater-ing 73 DE N0MJS P.S. repeater location is the top spot on a 100' tower in a rural location that is relatively high terrain. The repeater is meant to cover between two cities 25 miles apart, and is between them. Transmitter is a 100W TPL RXRF that I'd like to run at the 100W. I have remote receive locations and will place remotes and a voter if I can talk loud enough to warrant it. -- Cort Buffington H: +1-785-838-3034 M: +1-785-865-7206 -- Cort Buffington H: +1-785-838-3034 M: +1-785-865-7206
Re: [Repeater-Builder] UHF Repeater Antennas (combining threads)
I have also made similar modifications to a DB 222 antenna (that's a DB 224 with only two dipoles). I had a Rohde Schwarz spectrum analyzer with tracking generator and VSWR bridge connected directly to the antenna feedline. I tried extending both ends of the dipole with various methods. While fooling around with them,I noticed something very interesting. I observed that extending only one particular end of the dipole gave much better results than extending both ends or just the other end. The best return loss (lowest SWR) was realized when I extended what I would call the "cold end " of the dipole, that is the end furthest from the feedpoint and usually at the bottom. I found that the best method I tried to extend the dipolewas to clamp an aluminum rod (I bought at Home Depot) to the straight part of the element with small stainless steel hose clamps. I could even tell a difference between extending the front or the back of the cold end with the best again at further from the dipole's feedpoint. The best RL at the antenna array feedpoint with this arrangement was about 20 dB or about 1.2 SWR at the frequencyat which I was sweeping (147 MHz). Bandwidth was still good but not as good as before modifications. I haven't tried the procedure on a 224 yet but I suspect the results will be the similar. Dave BaughnDirector of EngineeringThe University of AlabamaCenter for Public Television and RadioWVUA/WUOA-TV WUAL/ WQPR/ WAPR FMBox 870150195 Reese Phifer Hall, 901 University Blvd.Tuscaloosa, Alabama 35487205.348.8622 cell 205.310.8798[EMAIL PROTECTED] KX4I Cort Buffington [EMAIL PROTECTED] 8/25/2008 1:21 PM Thanks Jim -- I have been considering lengthening in such a similar fashion. Did you have any noticeable pattern distortion problems or any other side-effects? On Aug 25, 2008, at 10:36 AM, Jim Brown wrote: I have had good luck modifying VHF antennas cut for the 155 mHz band down into the ham band by adding a short stub to each end of each dipole. I flatten a piece of an old TV antenna that has a round element that is rolled into a tube and put a screw through the flattened end wrapped around the end of each element. After the extension is installed I cut the extension to 2 inches.I don't see why the same idea can't be carried over to the UHF antennas. I would suggest a simple way of adding some length to a 440 element would be to drill a hole through the element on each end and put a brass screw through the hole. You can adjust the length of the extension to center the antenna down in the ham band. I did not modify the harness on my 2 meter antenna conversions, and I doubt you would have to on the 440 antenna.When I modified the VHF dipoles, I removed one dipole and connected my SWR meter to the dipole terminals and found the center frequency. It turned out to be 155 mHz in my case. I then experimented with the extensions until I got the dipole down to 146 mHz and found the extension to be 2 inches. I would suggest that you do the same, and when you find the extension for the one dipole to get it down to 445 mHz, add the same length screw to each of the other dipole ends. Using a #8 or #10 screw might do the trick. I would allow it to stick through the dipole at least an inch, and see where the center frequency of the dipole winds up and adjust the length to center the frequency where you want it. The dipole may not be 50 ohm, as I recall my VHF dipoles were showing about 100 ohms at resonance, so just move the SWR minimum to where you want it by adjusting the screw length and reattach the feedline harness.73 - Jim W5ZIT--- OnSun, 8/24/08, Cort Buffington[EMAIL PROTECTED]ks.orgwrote: From: Cort Buffington [EMAIL PROTECTED]ks.orgSubject: [Repeater-Builder] UHF Repeater Antennas (combining threads)To: Repeater-Builder@yahoogroups.comDate: Sunday, August 24, 2008, 4:30 PM Folks,I have a similar question about UHF Amateur repeater antennas so I'lltry to combine threads if possible.I just tested my two DB-420s with freshly re-taped harnesses andcleaned up connections, etc. I'm getting somewhere around 1.7:1 to1.8:1 VSWR on 444.825, the repeater transmit frequency. Here are myponderings to the combined wisdom of the group (religious and highlyopinionated advice welcomed). The advice here is ALWAYS helpful, soplease folks, don't be bashful :)1) Just use it as is, after I put the 105' of hardline on it and allthat'll be "good enough"?2) Try some sort of modification to improve performance in the ham band?3) Ah, forget the 20' tall antenna, just put up a Diamond X50 and callit good?4) Give up repeater-ing73 DE N0MJSP.S. repeater location is the top spot on a 100' tower in a rurallocation that is relatively high terrain. The repeater is meant tocover between two cities 25 miles apart, and is between them.Transmitter is a 100W TPL RXRF that I'd like to run at the 100W. Ihave remote receive locations and will place remotes and a voter if Ican "talk loud enough" to war
Re: [Spam] Re: [Repeater-Builder] UHF Repeater Antennas (combining threads)
What if I added something between the mast and the dipole assembly to increase the distance between the dipole and the mast on the VHF antenna? I have a Cushcraft antenna that looks like a VHF version of a DB-404. The dipoles are a little shoter tip to tip than the ones on a DB-224a but the SWR is good all the way down to 146mhz. The major difference I see is how far from the mast the dipoles are. - Original Message - From: Repeater-Builder@yahoogroups.com Repeater-Builder@yahoogroups.com To: Repeater-Builder@yahoogroups.com Repeater-Builder@yahoogroups.com Sent: Mon Aug 25 13:21:44 2008 Subject: [Spam] Re: [Repeater-Builder] UHF Repeater Antennas (combining threads) Thanks Jim -- I have been considering lengthening in such a similar fashion. Did you have any noticeable pattern distortion problems or any other side-effects? On Aug 25, 2008, at 10:36 AM, Jim Brown wrote: I have had good luck modifying VHF antennas cut for the 155 mHz band down into the ham band by adding a short stub to each end of each dipole. I flatten a piece of an old TV antenna that has a round element that is rolled into a tube and put a screw through the flattened end wrapped around the end of each element. After the extension is installed I cut the extension to 2 inches. I don't see why the same idea can't be carried over to the UHF antennas. I would suggest a simple way of adding some length to a 440 element would be to drill a hole through the element on each end and put a brass screw through the hole. You can adjust the length of the extension to center the antenna down in the ham band. I did not modify the harness on my 2 meter antenna conversions, and I doubt you would have to on the 440 antenna. When I modified the VHF dipoles, I removed one dipole and connected my SWR meter to the dipole terminals and found the center frequency. It turned out to be 155 m Hz in my case. I then experimented with the extensions until I got the dipole down to 146 mHz and found the extension to be 2 inches. I would suggest that you do the same, and when you find the extension for the one dipole to get it down to 445 mHz, add the same length screw to each of the other dipole ends. Using a #8 or #10 screw might do the trick. I would allow it to stick through the dipole at least an inch, and see where the center frequency of the dipole winds up and adjust the length to center the frequency where you want it. The dipole may not be 50 ohm, as I recall my VHF dipoles were showing about 100 ohms at resonance, so just move the SWR minimum to where you want it by adjusting the screw length and reattach the feedline harness. 73 - Jim W5ZIT --- On Sun, 8/24/08, Cort Buffington [EMAIL PROTECTED] / i wrote: From: Cort Buffington [EMAIL PROTECTED] Subject: [Repeater-Builder] UHF Repeater Antennas (combining threads) To: Repeater-Builder@yahoogroups.com Date: Sunday, August 24, 2008, 4:30 PM Folks, I have a similar question about UHF Amateur repeater antennas so I'll try to combine threads if possible. I just tested my two DB-420s with freshly re-taped harnesses and cleaned up connections, etc. I'm getting somewhere around 1.7:1 to 1.8:1 VSWR on 444.825, the repeater transmit frequency. Here are my ponderings to the combined wisdom of the group (religious and highly opinionated advice welcomed). The advice here is ALWAYS helpful, so please folks, don't be bashful :) 1) Just use it as is, after I put the 105' of hardline on it and all that'll be good enough? 2) Try some sort of modification to improve performance in the ham band? 3) Ah, forget the 20' tall antenna, just put up a Diamond X50 and call it good? 4) Give up repeater-ing 73 DE N0MJS P.S. repeater location is the top spot on a 100' tower in a rural location that is relatively high terrain. The repeater is meant to cover between two cities 25 miles apart, a n d is between them. Transmitter is a 100W TPL RXRF that I'd like to run at the 100W. I have remote receive locations and will place remotes and a voter if I can talk loud enough to warrant it. -- Cort Buffington H: +1-785-838-3034 M: +1-785-865-7206 -- Cort Buffington H: +1-785-838-3034 M: +1-785
Re: [Repeater-Builder] UHF Repeater Antennas (combining threads)
All the antennas that I have modified are in service and work very well. Also a buddy in Florida modified one the same way and his is working fine as far as I know. I would not expect much change in the vertical pattern, as the feeds to the dipole antennas are the same length, so the only thing that would change is the feed impedance (reactance) when you operate the harness at a different frequency. You can make a dipole antenna down-tilt for mountain top operation, but it involves changing the length of some of the interconnect harness, and as I recall from your write-up, you are not looking for any down-tilt. A 1:1 match or near 1:1 is possible by just adding the short stubs to the ends of the dipoles. Lots of folks don't bother and adjust a Z match to give a 1:1 SWR to the duplexer with no modification to the antenna. But the purest will want to have a 1:1 match or as close as possible to 1:1. Our club just ordered a DB-224E to replace an ageing 224 we are using now and I expect it to be pretty close to 1:1 when we get it up. The 224 we are replacing has the stubs to bring it down into the band. All the insulators are broken on the old antenna elements, and the harness is in really sad shape. One section has been replaced since the old one had opened up at a splice due to water leakage. I guess it has been in service for 35 or maybe 40 years - HI. It took a fall several years ago and we had to replace the mast. So time for a new one ($650 or so I think - plus $120 for shipping). 73 - Jim W5ZIT --- On Mon, 8/25/08, Cort Buffington [EMAIL PROTECTED] wrote: From: Cort Buffington [EMAIL PROTECTED] Subject: Re: [Repeater-Builder] UHF Repeater Antennas (combining threads) To: Repeater-Builder@yahoogroups.com Date: Monday, August 25, 2008, 1:21 PM Thanks Jim -- I have been considering lengthening in such a similar fashion. Did you have any noticeable pattern distortion problems or any other side-effects? On Aug 25, 2008, at 10:36 AM, Jim Brown wrote: I have had good luck modifying VHF antennas cut for the 155 mHz band down into the ham band by adding a short stub to each end of each dipole. I flatten a piece of an old TV antenna that has a round element that is rolled into a tube and put a screw through the flattened end wrapped around the end of each element. After the extension is installed I cut the extension to 2 inches. I don't see why the same idea can't be carried over to the UHF antennas. I would suggest a simple way of adding some length to a 440 element would be to drill a hole through the element on each end and put a brass screw through the hole. You can adjust the length of the extension to center the antenna down in the ham band. I did not modify the harness on my 2 meter antenna conversions, and I doubt you would have to on the 440 antenna. When I modified the VHF dipoles, I removed one dipole and connected my SWR meter to the dipole terminals and found the center frequency. It turned out to be 155 mHz in my case. I then experimented with the extensions until I got the dipole down to 146 mHz and found the extension to be 2 inches. I would suggest that you do the same, and when you find the extension for the one dipole to get it down to 445 mHz, add the same length screw to each of the other dipole ends. Using a #8 or #10 screw might do the trick. I would allow it to stick through the dipole at least an inch, and see where the center frequency of the dipole winds up and adjust the length to center the frequency where you want it. The dipole may not be 50 ohm, as I recall my VHF dipoles were showing about 100 ohms at resonance, so just move the SWR minimum to where you want it by adjusting the screw length and reattach the feedline harness. 73 - Jim W5ZIT --- On Sun, 8/24/08, Cort Buffington [EMAIL PROTECTED] ks.org wrote: From: Cort Buffington [EMAIL PROTECTED] ks.org Subject: [Repeater-Builder] UHF Repeater Antennas (combining threads) To: Repeater-Builder@ yahoogroups. com Date: Sunday, August 24, 2008, 4:30 PM Folks, I have a similar question about UHF Amateur repeater antennas so I'll try to combine threads if possible. I just tested my two DB-420s with freshly re-taped harnesses and cleaned up connections, etc. I'm getting somewhere around 1.7:1 to 1.8:1 VSWR on 444.825, the repeater transmit frequency. Here are my ponderings to the combined wisdom of the group (religious and highly opinionated advice welcomed). The advice here is ALWAYS helpful, so please folks, don't be bashful :) 1) Just use it as is, after I put the 105' of hardline on it and all that'll be good enough? 2) Try some sort of modification to improve performance in the ham band? 3) Ah, forget the 20' tall antenna, just put up a Diamond X50 and call it good? 4) Give up repeater-ing 73 DE N0MJS P.S. repeater location is the top spot on a 100' tower in a rural location that is relatively high terrain
Re: [Spam] Re: [Repeater-Builder] UHF Repeater Antennas (combining threads)
If you extend the dipoles further from the mast, you will loose the capability to stagger the dipoles around the mast to obtain omni coverage. Even with the close spaced dipoles there is a slight scaloping of the vertical angle as you go around 360 degrees. The further out the dipoles are placed, the more variation in the vertical angle you will see. Back when the FCC required an antenna pattern for licensing a repeater, I put a DB-224 on a mast and ran it through an antenna range, and observed the scaloping. From that time on I have always prefered to put all the dipoles on the same side of the mast and accept the 3 dB offset in antenna gain. The plot is perfectly circular, but the center is offset with the aligned dipoles. Gain is only 3 dB off the back of the mast but is 9 dB in the direction the dipoles are pointing. And there is no scaloping in the vertical angle at all - 73 - Jim W5ZIT --- On Mon, 8/25/08, NORM KNAPP [EMAIL PROTECTED] wrote: From: NORM KNAPP [EMAIL PROTECTED] Subject: Re: [Spam] Re: [Repeater-Builder] UHF Repeater Antennas (combining threads) To: Repeater-Builder@yahoogroups.com Date: Monday, August 25, 2008, 4:05 PM What if I added something between the mast and the dipole assembly to increase the distance between the dipole and the mast on the VHF antenna? I have a Cushcraft antenna that looks like a VHF version of a DB-404. The dipoles are a little shoter tip to tip than the ones on a DB-224a but the SWR is good all the way down to 146mhz. The major difference I see is how far from the mast the dipoles are. - Original Message - From: Repeater-Builder@ yahoogroups. com Repeater-Builder@ yahoogroups. com To: Repeater-Builder@ yahoogroups. com Repeater-Builder@ yahoogroups. com Sent: Mon Aug 25 13:21:44 2008 Subject: [Spam] Re: [Repeater-Builder] UHF Repeater Antennas (combining threads) Thanks Jim -- I have been considering lengthening in such a similar fashion. Did you have any noticeable pattern distortion problems or any other side-effects? On Aug 25, 2008, at 10:36 AM, Jim Brown wrote: I have had good luck modifying VHF antennas cut for the 155 mHz band down into the ham band by adding a short stub to each end of each dipole. I flatten a piece of an old TV antenna that has a round element that is rolled into a tube and put a screw through the flattened end wrapped around the end of each element. After the extension is installed I cut the extension to 2 inches. I don't see why the same idea can't be carried over to the UHF antennas. I would suggest a simple way of adding some length to a 440 element would be to drill a hole through the element on each end and put a brass screw through the hole. You can adjust the length of the extension to center the antenna down in the ham band. I did not modify the harness on my 2 meter antenna conversions, and I doubt you would have to on the 440 antenna. When I modified the VHF dipoles, I removed one dipole and connected my SWR meter to the dipole terminals and found the center frequency. It turned out to be 155 m Hz in my case. I then experimented with the extensions until I got the dipole down to 146 mHz and found the extension to be 2 inches. I would suggest that you do the same, and when you find the extension for the one dipole to get it down to 445 mHz, add the same length screw to each of the other dipole ends. Using a #8 or #10 screw might do the trick. I would allow it to stick through the dipole at least an inch, and see where the center frequency of the dipole winds up and adjust the length to center the frequency where you want it. The dipole may not be 50 ohm, as I recall my VHF dipoles were showing about 100 ohms at resonance, so just move the SWR minimum to where you want it by adjusting the screw length and reattach the feedline harness. 73 - Jim W5ZIT --- On Sun, 8/24/08, Cort Buffington [EMAIL PROTECTED] ks.org / i wrote: From: Cort Buffington [EMAIL PROTECTED] ks.org Subject: [Repeater-Builder] UHF Repeater Antennas (combining threads) To: Repeater-Builder@ yahoogroups. com Date: Sunday, August 24, 2008, 4:30 PM Folks, I have a similar question about UHF Amateur repeater antennas so I'll try to combine threads if possible. I just tested my two DB-420s with freshly re-taped harnesses and cleaned up connections, etc. I'm getting somewhere around 1.7:1 to 1.8:1 VSWR on 444.825, the repeater transmit frequency. Here are my ponderings to the combined wisdom of the group (religious and highly opinionated advice welcomed
[Repeater-Builder] UHF Repeater Antennas (combining threads)
Folks, I have a similar question about UHF Amateur repeater antennas so I'll try to combine threads if possible. I just tested my two DB-420s with freshly re-taped harnesses and cleaned up connections, etc. I'm getting somewhere around 1.7:1 to 1.8:1 VSWR on 444.825, the repeater transmit frequency. Here are my ponderings to the combined wisdom of the group (religious and highly opinionated advice welcomed). The advice here is ALWAYS helpful, so please folks, don't be bashful :) 1) Just use it as is, after I put the 105' of hardline on it and all that'll be good enough? 2) Try some sort of modification to improve performance in the ham band? 3) Ah, forget the 20' tall antenna, just put up a Diamond X50 and call it good? 4) Give up repeater-ing 73 DE N0MJS P.S. repeater location is the top spot on a 100' tower in a rural location that is relatively high terrain. The repeater is meant to cover between two cities 25 miles apart, and is between them. Transmitter is a 100W TPL RXRF that I'd like to run at the 100W. I have remote receive locations and will place remotes and a voter if I can talk loud enough to warrant it. -- Cort Buffington H: +1-785-838-3034 M: +1-785-865-7206
[Repeater-Builder] UHF Repeater
Hi all, I have a UHF MSR2000 repeater and various RX TX modules. The exciter module is a VTE4001A for 403-430 MHz. The RX module is a VRE4001B for the 450-512 MHz. Has anybody had any success tuning these to the 430-450 MHz Ham band? The curious part is that the existing RX (VRE4001B) was used on 416.9375. Are they that wide band at the front-end preselectors? Any and all information will be appreciated. Tony VE3DWI.
[Repeater-Builder] UHF repeater needed
Hello I would like either a Micor or GE Master II already converted to a 440 repeater. Please email me with what you have. 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/
Re: [Repeater-Builder] UHF repeater needed
hfdxcc wrote: Hello I would like either a Micor or GE Master II already converted to a 440 repeater. Please email me with what you have. You can have which ever you like made to your specifications: http://www.repeater-builder.com/rbtip/custombuilt.html Kevin 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/
Re: [Repeater-Builder] UHF Repeater Preamp
That's a hard question to answer. Some preselectors are based upon the physical package used for mobile duplexers, and may work just fine- but they are not flexible. I prefer to use an 8 inch bandpass cavity that I can tune for almost any selectivity and insertion loss that I want. If you have a good preamp with, say, 10 dB of gain, you can set up a bandpass cavity to be extremely narrow but with 5 dB insertion loss, and you will still be far better off (+5 dB) than without the preamp and you will have reduced the vulnerability to overload and desense. At UHF, with a 5 MHz split, the playing field is a lot different from that at 2m, with a 600 kHz split. 73, Eric Lemmon WB6FLY This just does not seem to be a good way to go. If you put a 5 db loss before the preamp the noise figure can not be made up nomater how much gain the preamp has. To top it all off you have to add about 2 db to that for the losses in the duplexer. You let the bp/br duplexer take care of the in band problems and then use a band pass cavity that does not have to have very much loss to take care of the out of band problems if needed. de KU4PT Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
RE: [Repeater-Builder] UHF Repeater Preamp
You let the bp/br duplexer take care of the in band problems and then use a band pass cavity that does not have to have very much loss to take care of the out of band problems if needed. de KU4PT Or even better, run split antennas with a Tower Top Amp if you are on a 300 ft or better tower. Antenna, Polyphaser, Combline or Cavity, Preamp and Power Pickoff/protector, then down the coax the the injector and equipment. Should really rock and roll. Ssb Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
RE: [Repeater-Builder] UHF Repeater Preamp
Before you fix a receive problem be sure there is a problem. I have used ARR GasFet preamps for some time with excellent results. Be sure you have a filter or cavity ahead of the preamp, and that you do not have so much out of band energy getting to the preamp that it goes into overload and becomes a non-linear mixer. I have used GasFets in tower top systems (one at 600 ft for over 15 years) with PolyPhaser's ahead of the amp. I also built a relay tree to bypass the preamp when power was removed. The relays (GE Pro antenna relays) caused more trouble than they solved because there was no wiping action in the contacts. Aside from the obvious gain of the preamp, the very low noise figure ahead of a not so good front end amp can make a substantial improvement. Be the 3rd order intercept point is as high as possible for intermodulation mixture products. Also test for receiver desentization with an isolated tee incase there is not enough receiver protection from the transmitter. What worked before preamp now needs to be at least 15 db better with the preamp. That is, if you had a little desensitization before adding the preamp, it will probably get worse - double shielded cable and ground is a must. 73, steve nu5d Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] UHF Repeater Preamp
Will it be better to use a bandpass can or an actual preselector? I'm trying to get the NF when the line was swept so I can give it to you to see if I do need a preamp. As far as I can remember it was pretty good I just wanted to improve on it. Thanks.Eric Lemmon [EMAIL PROTECTED] wrote: Adding a preamp to some repeater systems does not always make it "hear"better; sometimes the receiver becomes more sensitive to overload,intermod, desense, and has a higher noise level. You can mitigate someof these problems by placing a bandpass cavity immediately in front ofthe preamp.Most bandpass/bandreject duplexers have surprisingly little bandpasseffect, and will pass an awful lot of signal on either side of thereceive frequency. A dedicated bandpass cavity will act as apreselector to greatly limit the signal seen by the preamp, and thatwill significantly reduce the noise floor.73, Eric Lemmon WB6FLYuplink28 wrote: I'm thinking about putting a receiver preamp in our system. Any words of advice from anyone would be greatly appreciated. Brand, model, etc. If you ahve one for sale let me know too. Thanks.Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/ Do you Yahoo!? Free Pop-Up Blocker - Get it now Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.
RE: [Repeater-Builder] UHF Repeater Preamp
Howdy Dino regarding the preamp and filter. First thing that sticks out is sweeping the line. This is a good figure of merit for an antenna system and cable. The process involves running a sweep across the band and a graphical representation of VSWR across the band. The unit of measure is called rho, or return loss, Measured in dB. There is a direct relation between return loss and VSWR, where a 25 dB return loss represents a very low standing wave ratio, and ideal was 28 to 30 db on microwave antennas. A good return loss or low standing wave is an indication of a good antenna and feedline, needed for good duplex operation. Noise figure is a measure of the inherent noise generated in an amplifier, and the result of several stages in cascade. Each stage contributes gain and noise. A low noise high gain amplifier ahead of several noisy stages can dramatically improve the overall noise figure of a receiver, and is one of the benefits of a low noise preamp. At UHF the most common filter would be either a cavity or else a helical resonator. A good quality BpBr duplexer ahead of the preamp might be just AOK, or else an additional cavity ahead of the preamp might be needed if there is much receiver desense. A lot depends on other transmitters at the same or near by locations, and lots of cut and try is needed. Regards, Steve NU5D Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.
[Repeater-Builder] UHF Repeater Preamp
I'm thinking about putting a receiver preamp in our system. Any words of advice from anyone would be greatly appreciated. Brand, model, etc. If you ahve one for sale let me know too. Thanks. Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] UHF Repeater Preamp
At 04:01 AM 12/5/03 +, you wrote: I'm thinking about putting a receiver preamp in our system. Any words of advice from anyone would be greatly appreciated. Brand, model, etc. If you ahve one for sale let me know too. Thanks. Look at http://www.repeater-builder.com/rbtip/supplyindex.html and scroll down to repeater receiver preamplifiers. Several vendors are listed. My personal choice is Anglelinear - I've had the pleasure of chatting with Chip Angle in person several times and the guy knows his stuff - he is a weak signal enthusiast and repeater owner and has developed most of his products from requirements from his own activities or those of his customers. Various folks I know have collectively purchased over $90k worth of products from him over the last 25 years. Other customers include NASA. His web site (http://www.anglelinear.com) is worth spending a hour perusing, and the Repeater Application Notes page (buried in the Duplexers section) should be required reading for everyone. Just an opinion from a very satisfied customer. Mike WA6ILQ Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] UHF Repeater Preamp
I have had great results with http://www.advancedreceiver.com/index1.html on My 444.750 Repeater had a nearby Lighting strike damage it not the receiver , Sent it in and they repaired it for about $ 15.00 and sent it back right away. 73 De Don KA9QJG Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
Re: [Repeater-Builder] UHF Repeater Preamp
Adding a preamp to some repeater systems does not always make it hear better; sometimes the receiver becomes more sensitive to overload, intermod, desense, and has a higher noise level. You can mitigate some of these problems by placing a bandpass cavity immediately in front of the preamp. Most bandpass/bandreject duplexers have surprisingly little bandpass effect, and will pass an awful lot of signal on either side of the receive frequency. A dedicated bandpass cavity will act as a preselector to greatly limit the signal seen by the preamp, and that will significantly reduce the noise floor. 73, Eric Lemmon WB6FLY uplink28 wrote: I'm thinking about putting a receiver preamp in our system. Any words of advice from anyone would be greatly appreciated. Brand, model, etc. If you ahve one for sale let me know too. Thanks. Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/ Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
