Re: [Repeater-Builder] Maxtrac Question
I have had that happen on radios that had been overheated and needed the lead tabs resoldered on the output transistors to get the power back up. maybe not your case though. Usually most radios will make more than their rated power especially at higher input voltages. Sometimes not for long though! You might check dc voltages inside the radio when keyed to make sure you don't get a bad voltage sag when transmitting. Old Regency radios had a bad habit of that when the off on switch got weak. wb5oxq - Original Message - From: tgundo2003 To: Repeater-Builder@yahoogroups.com Sent: Saturday, June 07, 2008 12:52 AM Subject: [Repeater-Builder] Maxtrac Question I have a UHF (D44) 40w 449-470 maxtrac on the bench. All checks out good, except power out. Most I can get out of it is 22 watts, and that happens at 92 on the adjustment scale, any values above 92 yield no difference in power output. Here is the strange thing- I get more out (22W) at 441.300, and only 14w at 467.xxx. Since this is a 449-470 split I would think it would be the opposite. Anyone have any thoughts? Tom W9SRV
RE: [Repeater-Builder] Re: antenna suggestions for 440mhz
Bob, When we as ham use commercial cut antenna in the ham bands that were designed for 450-470 MHz down at 441 MHz you will have what is called electrical down tilt. As a result, your reflected power will rise the more you take the antenna out of band. You can call and ask our friends at Sinclair, Telewave, Andrew, Motorola, and they all will tell you the same thing I said. Mike Mullarkey (K7PFJ) _ From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Friday, June 06, 2008 10:28 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Re: antenna suggestions for 440mhz At 6/6/2008 16:43, you wrote: The next thing that would change would be the downtilt rating. This will increase the more out-of band (in your case lower in freq.) you go, which may be a good thing depending on your particular situation/use/mounting structure / height /etc. If your looking for maximum distance, this may be an issue, but if your looking to,or have a need to fill-in lower areas this would help by bringing the lobes down more than original pattern... To clarify, if the DB-408 has no downtilt to begin with, it won't have any downtilt at frequencies outside it's nominal operating range either. Bob NO6B
RE: [Repeater-Builder] Re: antenna suggestions for 440mhz
First off you will definitely loose some of the gain from the original rated specs. About 1.5 - 2 Dbd. is what I'd expect...Maybe a little worse depending on where the antenna was originally cut for... For example, If the antenna was originally built for say a 454.xxx freq (center freq) the loss would be less at 442.xxx than one that had been built for 467.xxx. The antenna typically has a 20Mhz. bandwidth, +/- 10Mhz each side of center freq so you can see that one cut for the upper 460-ish range would be a little worse than the 450-ish freq. DB404/408/420 antennas were never cut to frequency - they were sold in frequency ranges. For example, a DB408-A is 406-420, DB408-B is 450-470, etc. So the closest one to 440 would be a DB4xx-B. If you ordered an antenna for 454.575, you would get a -B series antenna. In the wayback days, sometimes they would even stamp the label with the exact frequency you ordered, but the antenna wasn't cut for that frequency, they just marked it to identify the requested frequency. Nowadays they don't even bother to do that, the sticker will just say 450-470 MHz and it will come with a return loss sweep showing its performance across the entire band. The more bays, the worse the VSWR will be (speaking in very general terms here) as you operate these types of antennas out of band. For example, a 408-B will likely have better return loss than a 420-B when used at 440 MHz. The next thing that would change would be the downtilt rating. No, parallel-fed antennas do NOT suffer uptilt/downtilt as frequency is varied unless the harness was special-ordered for factory downtilt. If the antenna wasn't ordered with downtilt, all of the elements are fed in phase, and they will always be in phase regardless of frequency. The peak gain will be reduced as you operate them away from their design range as more power ends up in the usually-undesired sidelobes, but the main lobe will still be on the horizon. Series-fed antennas (like Stationmasters) will have the elevation pattern (downtilt/uptilt) affected as frequency changes, because the further up the antenna you go, the more and more the radiating elements end up being out of phase compared to the lower ones, thereby creating the uptilt/downtilt. This issue comes up so many times, and is so misunderstood, that there should probably be a FAQ about it on the web site... I like the DB's but unsure how bad the 450mhz matches when trying to use it down at 440.000mhz. I have 404's, 408's, 411's, 413's, and 420's in stock, all in the B version, a few A version, and a few S-440-450 ham-band versions which they don't make any more. I can sweep one if you want (please don't make me drag all of them out of the warehouse to test). Email direct if you're interested. --- Jeff WN3A
Re: [Repeater-Builder] Re: antenna suggestions for 440mhz
Well said. Thank you Jeff. Chuck WB2EDV - Original Message - From: Jeff DePolo [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Saturday, June 07, 2008 9:25 AM Subject: RE: [Repeater-Builder] Re: antenna suggestions for 440mhz First off you will definitely loose some of the gain from the original rated specs. About 1.5 - 2 Dbd. is what I'd expect...Maybe a little worse depending on where the antenna was originally cut for... For example, If the antenna was originally built for say a 454.xxx freq (center freq) the loss would be less at 442.xxx than one that had been built for 467.xxx. The antenna typically has a 20Mhz. bandwidth, +/- 10Mhz each side of center freq so you can see that one cut for the upper 460-ish range would be a little worse than the 450-ish freq. DB404/408/420 antennas were never cut to frequency - they were sold in frequency ranges. For example, a DB408-A is 406-420, DB408-B is 450-470, etc. So the closest one to 440 would be a DB4xx-B. If you ordered an antenna for 454.575, you would get a -B series antenna. In the wayback days, sometimes they would even stamp the label with the exact frequency you ordered, but the antenna wasn't cut for that frequency, they just marked it to identify the requested frequency. Nowadays they don't even bother to do that, the sticker will just say 450-470 MHz and it will come with a return loss sweep showing its performance across the entire band. The more bays, the worse the VSWR will be (speaking in very general terms here) as you operate these types of antennas out of band. For example, a 408-B will likely have better return loss than a 420-B when used at 440 MHz. The next thing that would change would be the downtilt rating. No, parallel-fed antennas do NOT suffer uptilt/downtilt as frequency is varied unless the harness was special-ordered for factory downtilt. If the antenna wasn't ordered with downtilt, all of the elements are fed in phase, and they will always be in phase regardless of frequency. The peak gain will be reduced as you operate them away from their design range as more power ends up in the usually-undesired sidelobes, but the main lobe will still be on the horizon. Series-fed antennas (like Stationmasters) will have the elevation pattern (downtilt/uptilt) affected as frequency changes, because the further up the antenna you go, the more and more the radiating elements end up being out of phase compared to the lower ones, thereby creating the uptilt/downtilt. This issue comes up so many times, and is so misunderstood, that there should probably be a FAQ about it on the web site... I like the DB's but unsure how bad the 450mhz matches when trying to use it down at 440.000mhz. I have 404's, 408's, 411's, 413's, and 420's in stock, all in the B version, a few A version, and a few S-440-450 ham-band versions which they don't make any more. I can sweep one if you want (please don't make me drag all of them out of the warehouse to test). Email direct if you're interested. --- Jeff WN3A Yahoo! Groups Links
RE: [Repeater-Builder] Maxtrac Question
Tom, It appears that the final transistor Q2740 is dead, and the driver transistor Q2730 is running wide open. The driver normally provides about 13 watts to the final. Check all solder joints and verify the correct DC voltages are present during transmit. An RF millivoltmeter can be a great help in troubleshooting this problem. The complete MaxTrac service manual 6880102W84 is available for download on the RBTIP, and Part 4 of 4 covers the power amplifier. The 17.1 MB file is here: www.repeater-builder.com/maxtrac/files/maxtrac-manual-6880102w84-o-4-of-4.p df or as a TinyURL: http://tinyurl.com/5qoar8 Let's hope that the final PA transistor is okay, because it (4880225C24) costs about $110 from Motorola. I did a cursory search on the Internet and found a supplier in Mexico selling the same part for about $65. 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of tgundo2003 Sent: Friday, June 06, 2008 10:52 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Maxtrac Question I have a UHF (D44) 40w 449-470 maxtrac on the bench. All checks out good, except power out. Most I can get out of it is 22 watts, and that happens at 92 on the adjustment scale, any values above 92 yield no difference in power output. Here is the strange thing- I get more out (22W) at 441.300, and only 14w at 467.xxx. Since this is a 449-470 split I would think it would be the opposite. Anyone have any thoughts? Tom W9SRV
RE: [Repeater-Builder] Maxtrac Question
Cheaper to just buy another UHF MaxTrac or Radius and swap the PA outright. By the time you figure in the troubleshooting and repair time to replace Q2740, you'd be better off with another radio and keep the best looking and working parts. Bob M. == --- On Sat, 6/7/08, Eric Lemmon [EMAIL PROTECTED] wrote: From: Eric Lemmon [EMAIL PROTECTED] Subject: RE: [Repeater-Builder] Maxtrac Question To: Repeater-Builder@yahoogroups.com Date: Saturday, June 7, 2008, 10:57 AM Tom, It appears that the final transistor Q2740 is dead, and the driver transistor Q2730 is running wide open. The driver normally provides about 13 watts to the final. Check all solder joints and verify the correct DC voltages are present during transmit. An RF millivoltmeter can be a great help in troubleshooting this problem. The complete MaxTrac service manual 6880102W84 is available for download on the RBTIP, and Part 4 of 4 covers the power amplifier. The 17.1 MB file is here: www.repeater-builder.com/maxtrac/files/maxtrac-manual-6880102w84-o-4-of-4.p df or as a TinyURL: http://tinyurl.com/5qoar8 Let's hope that the final PA transistor is okay, because it (4880225C24) costs about $110 from Motorola. I did a cursory search on the Internet and found a supplier in Mexico selling the same part for about $65. 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of tgundo2003 Sent: Friday, June 06, 2008 10:52 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Maxtrac Question I have a UHF (D44) 40w 449-470 maxtrac on the bench. All checks out good, except power out. Most I can get out of it is 22 watts, and that happens at 92 on the adjustment scale, any values above 92 yield no difference in power output. Here is the strange thing- I get more out (22W) at 441.300, and only 14w at 467.xxx. Since this is a 449-470 split I would think it would be the opposite. Anyone have any thoughts? Tom W9SRV
RE: [Repeater-Builder] Re: antenna suggestions for 440mhz
In fear of moving off topic... I'd like to ask how one can determine the electrical downtilt of an antenna? I just put into service a RSF/Celwave Super StationmasterR Model 10017-6 that is designed for 925-960 MHz on my 927.5250 repeater. The added gain factor of the antenna (an additional 4dBd over what was previously in place - a Decibel DB586-Y) does not seem to benefit the receive (at 902 MHz). I gained what seems like a little extra receive range, but not equal to what I seem to have gained in transmit coverage. This discussion thread leads me to wonder if maybe some electrical downtilt may be affecting the receive frequency? Is this possible? Antennas are not my strong point. ;-) Thanks, Mark - N9WYS -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Friday, June 06, 2008 11:19 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Re: antenna suggestions for 440mhz At 6/6/2008 19:22, you wrote: The series-fed types (usually fiberglass at these frequencies) *will* tilt their patterns when moving away from their design frequency. Laryn K8TVZ The good news is that the pattern tilts down when used at frequencies below the design frequency. The big question is by how much. Would be easy to calculate in NECWin if I could only get a good NEC model for the coaxial colinear array. I'm not quite expert enough in NEC to figure out how to create that model. Bob NO6B
Re: [Repeater-Builder] Re: antenna suggestions for 440mhz
down-tilt is specified when ordering the unit other than the original paperwork, the only method would be to have it tested on a test range and that would probably cost more than ordering a new one Gary - Original Message - From: n9wys To: Repeater-Builder@yahoogroups.com Sent: Saturday, June 07, 2008 10:22 AM Subject: RE: [Repeater-Builder] Re: antenna suggestions for 440mhz In fear of moving off topic... I'd like to ask how one can determine the electrical downtilt of an antenna? I just put into service a RSF/Celwave Super StationmasterR Model 10017-6 that is designed for 925-960 MHz on my 927.5250 repeater. The added gain factor of the antenna (an additional 4dBd over what was previously in place - a Decibel DB586-Y) does not seem to benefit the receive (at 902 MHz). I gained what seems like a little extra receive range, but not equal to what I seem to have gained in transmit coverage. This discussion thread leads me to wonder if maybe some electrical downtilt may be affecting the receive frequency? Is this possible? Antennas are not my strong point. ;-) Thanks, Mark - N9WYS
RE: [Repeater-Builder] Re: antenna suggestions for 440mhz
Thanks Gary. I was looking for more of a generic answer along the lines of, As you move down in frequency, electrical downtilt . (Enter INCREASES or DECREASES here as necessary -- if this is the case.) I am also wondering if 20MHz on the receive is far enough off to cause a problem. Remember, this stick is within 1 MHz of the bottom of its range on TRANSMIT, and well below it on Receive. So this is why I ask about adverse effects. Not that I'm thinking of scrapping it, but I'm just trying to figure out why I didn't gain the receive sensitivity/coverage I thought I would with the added gain. With all this talk about downtilt... if that is what is happening here, that would explain why I'm experiencing what I am on receive. Or am I worrying about gremlins?? Mark -N9WYS -Original Message- From: Repeater-Builder@yahoogroups.com On Behalf Of Gary Glaenzer Sent: Saturday, June 07, 2008 10:30 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Re: antenna suggestions for 440mhz down-tilt is specified when ordering the unit other than the original paperwork, the only method would be to have it tested on a test range and that would probably cost more than ordering a new one Gary - Original Message - From: n9wys To: Repeater-Builder@yahoogroups.com Sent: Saturday, June 07, 2008 10:22 AM Subject: RE: [Repeater-Builder] Re: antenna suggestions for 440mhz In fear of moving off topic... I'd like to ask how one can determine the electrical downtilt of an antenna? I just put into service a RSF/Celwave Super StationmasterR Model 10017-6 that is designed for 925-960 MHz on my 927.5250 repeater. The added gain factor of the antenna (an additional 4dBd over what was previously in place - a Decibel DB586-Y) does not seem to benefit the receive (at 902 MHz). I gained what seems like a little extra receive range, but not equal to what I seem to have gained in transmit coverage. This discussion thread leads me to wonder if maybe some electrical downtilt may be affecting the receive frequency? Is this possible? Antennas are not my strong point. ;-) Thanks, Mark - N9WYS Yahoo! Groups Links No virus found in this incoming message. Checked by AVG. Version: 8.0.100 / Virus Database: 270.0.0/1489 - Release Date: 6/7/2008 11:17 AM
Re: [Repeater-Builder] Re: antenna suggestions for 440mhz
well, as has been commented, if it was not ordered with down-tilt, there will be none at any freqency you put into it, as all elements are exactly in-phase since the method of acheiving down-tilt was to make the feeds to the lower elements shorter, if it originall had down-tilt I'd venture that the down-tilt would decrease with decreasing frequency (less phase difference) I think. Gary - Original Message - From: n9wys To: Repeater-Builder@yahoogroups.com Sent: Saturday, June 07, 2008 11:17 AM Subject: RE: [Repeater-Builder] Re: antenna suggestions for 440mhz Thanks Gary. I was looking for more of a generic answer along the lines of, As you move down in frequency, electrical downtilt . (Enter INCREASES or DECREASES here as necessary -- if this is the case.) I am also wondering if 20MHz on the receive is far enough off to cause a problem. Remember, this stick is within 1 MHz of the bottom of its range on TRANSMIT, and well below it on Receive. So this is why I ask about adverse effects. Not that I'm thinking of scrapping it, but I'm just trying to figure out why I didn't gain the receive sensitivity/coverage I thought I would with the added gain. With all this talk about downtilt... if that is what is happening here, that would explain why I'm experiencing what I am on receive. Or am I worrying about gremlins?? Mark -N9WYS -Original Message- From: Repeater-Builder@yahoogroups.com On Behalf Of Gary Glaenzer Sent: Saturday, June 07, 2008 10:30 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Re: antenna suggestions for 440mhz down-tilt is specified when ordering the unit other than the original paperwork, the only method would be to have it tested on a test range and that would probably cost more than ordering a new one Gary - Original Message - From: n9wys To: Repeater-Builder@yahoogroups.com Sent: Saturday, June 07, 2008 10:22 AM Subject: RE: [Repeater-Builder] Re: antenna suggestions for 440mhz In fear of moving off topic... I'd like to ask how one can determine the electrical downtilt of an antenna? I just put into service a RSF/Celwave Super StationmasterR Model 10017-6 that is designed for 925-960 MHz on my 927.5250 repeater. The added gain factor of the antenna (an additional 4dBd over what was previously in place - a Decibel DB586-Y) does not seem to benefit the receive (at 902 MHz). I gained what seems like a little extra receive range, but not equal to what I seem to have gained in transmit coverage. This discussion thread leads me to wonder if maybe some electrical downtilt may be affecting the receive frequency? Is this possible? Antennas are not my strong point. ;-) Thanks, Mark - N9WYS Yahoo! Groups Links No virus found in this incoming message. Checked by AVG. Version: 8.0.100 / Virus Database: 270.0.0/1489 - Release Date: 6/7/2008 11:17 AM
RE: [Repeater-Builder] Re: antenna suggestions for 440mhz
At 6/7/2008 08:22, you wrote: In fear of moving off topic... I'd like to ask how one can determine the electrical downtilt of an antenna? I just put into service a RSF/Celwave Super StationmasterR Model 10017-6 that is designed for 925-960 MHz on my 927.5250 repeater. The added gain factor of the antenna (an additional 4dBd over what was previously in place - a Decibel DB586-Y) does not seem to benefit the receive (at 902 MHz). I gained what seems like a little extra receive range, but not equal to what I seem to have gained in transmit coverage. Downtilt shouldn't vary too much between TX RX freqs. What's probably happening is that the increased gain is resulting in increased noise pickup from the horizon as well as signal. Changes in gain directly affect your transmit ERP, but they don't necessarily translate directly into increased RX range depending on where the noise is. Slightly related: I once maintained a repeater at a residential mountain site with lots of elevation but no clear view to the ground (trees in the way). The site RF characteristics on 2 meters were somewhat like an RF black hole: RF could get in but was hard to get out. We needed ~200 watts of TX power on the repeater to balance TX RX with a 50 watt mobile user. I believe the reason was foliage absorption combined with a high noise floor down below. Around here antenna noise temperatures on 2 meters are typically ~3000 K. However this site had much lower noise - it's the only site around here where adding a preamp to a G.E. receiver resulted in actual system sensitivity improvement. So with biological attenuation surrounding the site, both signal noise approaching the site were attenuated. With the low noise RX, the net reduction in S/N due to the attenuation was minimal. However, the attenuation directly reduced the TX signal leaving the site. So the net effect was the site heard OK but TXing out was difficult. Bob NO6B
[Repeater-Builder] Re: antenna suggestions for 440mhz
Maybe you're already hearing as well as you're going to at that site. A given user signal is only going to be so strong compared to the noise level no matter what you do. Jeff --- In Repeater-Builder@yahoogroups.com, n9wys [EMAIL PROTECTED] wrote: In fear of moving off topic... I'd like to ask how one can determine the electrical downtilt of an antenna? I just put into service a RSF/Celwave Super StationmasterR Model 10017-6 that is designed for 925-960 MHz on my 927.5250 repeater. The added gain factor of the antenna (an additional 4dBd over what was previously in place - a Decibel DB586-Y) does not seem to benefit the receive (at 902 MHz). I gained what seems like a little extra receive range, but not equal to what I seem to have gained in transmit coverage. This discussion thread leads me to wonder if maybe some electrical downtilt may be affecting the receive frequency? Is this possible? Antennas are not my strong point. ;-) Thanks, Mark - N9WYS -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Friday, June 06, 2008 11:19 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Re: antenna suggestions for 440mhz At 6/6/2008 19:22, you wrote: The series-fed types (usually fiberglass at these frequencies) *will* tilt their patterns when moving away from their design frequency. Laryn K8TVZ The good news is that the pattern tilts down when used at frequencies below the design frequency. The big question is by how much. Would be easy to calculate in NECWin if I could only get a good NEC model for the coaxial colinear array. I'm not quite expert enough in NEC to figure out how to create that model. Bob NO6B
Re: [Repeater-Builder] Re: antenna suggestions for 440mhz
Hi Guys, My question is have you ever put up a downtilt antenna to replace an antenna of the same configuration, i.e. gain, etc. and have been able to say with 100% certainly that the downtilt worked? My 911 center went to high band for fire. Within a few days Industry Canada was on the phone saying that our cross band repeater from low band to high band was severely causing interference to a fire department in Canada. While I was on the phone, I would hear our units coming in loud and clear at the Industry Canada Office. Make a long story short, I had many conference calls between the FCC and Industry Canada and I agreed to Canada's request to mount a down tilt antenna at the same location of the existing antenna. A week later the antenna was installed and there was NO difference in signal quality from the Alma Hill New York Tower 2,558' to the location in Canada some 125 miles away. I cut the amp out and used the six watt exciter and I could still hear the signal over the phone from Canada just fine. We finally negotiated a frequency change and I walked away knowing that downtilt in this application didn't work. I might add that this was not inversion or ducking, the signal was there 24 X7 day after day. 73 JIM KA2AJH Wellsville, NY - Original Message - From: [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Saturday, June 07, 2008 12:35 PM Subject: RE: [Repeater-Builder] Re: antenna suggestions for 440mhz At 6/7/2008 08:22, you wrote: In fear of moving off topic... I'd like to ask how one can determine the electrical downtilt of an antenna? I just put into service a RSF/Celwave Super StationmasterR Model 10017-6 that is designed for 925-960 MHz on my 927.5250 repeater. The added gain factor of the antenna (an additional 4dBd over what was previously in place - a Decibel DB586-Y) does not seem to benefit the receive (at 902 MHz). I gained what seems like a little extra receive range, but not equal to what I seem to have gained in transmit coverage. Downtilt shouldn't vary too much between TX RX freqs. What's probably happening is that the increased gain is resulting in increased noise pickup from the horizon as well as signal. Changes in gain directly affect your transmit ERP, but they don't necessarily translate directly into increased RX range depending on where the noise is. Slightly related: I once maintained a repeater at a residential mountain site with lots of elevation but no clear view to the ground (trees in the way). The site RF characteristics on 2 meters were somewhat like an RF black hole: RF could get in but was hard to get out. We needed ~200 watts of TX power on the repeater to balance TX RX with a 50 watt mobile user. I believe the reason was foliage absorption combined with a high noise floor down below. Around here antenna noise temperatures on 2 meters are typically ~3000 K. However this site had much lower noise - it's the only site around here where adding a preamp to a G.E. receiver resulted in actual system sensitivity improvement. So with biological attenuation surrounding the site, both signal noise approaching the site were attenuated. With the low noise RX, the net reduction in S/N due to the attenuation was minimal. However, the attenuation directly reduced the TX signal leaving the site. So the net effect was the site heard OK but TXing out was difficult. Bob NO6B
RE: [Repeater-Builder] Antenna downtilt (WAS: antenna suggestions for 440mhz)
OK, thanks Jeff. That could well be. I'm aware that higher gain figures on an omni antenna result in a narrower vertical beam width, so maybe the stations that aren't getting in as well as I'm expecting are under the optimal antenna beamwidth/pattern. Or am I just trying to be too cerebral about all this? Mark - N9WYS -Original Message- From: Repeater-Builder@yahoogroups.com On Behalf Of Jeff Kincaid Sent: Saturday, June 07, 2008 11:47 AM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Re: antenna suggestions for 440mhz Maybe you're already hearing as well as you're going to at that site. A given user signal is only going to be so strong compared to the noise level no matter what you do. Jeff --- In Repeater-Builder@yahoogroups.com, n9wys [EMAIL PROTECTED] wrote: In fear of moving off topic... I'd like to ask how one can determine the electrical downtilt of an antenna? I just put into service a RSF/Celwave Super StationmasterR Model 10017-6 that is designed for 925-960 MHz on my 927.5250 repeater. The added gain factor of the antenna (an additional 4dBd over what was previously in place - a Decibel DB586-Y) does not seem to benefit the receive (at 902 MHz). I gained what seems like a little extra receive range, but not equal to what I seem to have gained in transmit coverage. This discussion thread leads me to wonder if maybe some electrical downtilt may be affecting the receive frequency? Is this possible? Antennas are not my strong point. ;-) Thanks, Mark - N9WYS -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Friday, June 06, 2008 11:19 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Re: antenna suggestions for 440mhz At 6/6/2008 19:22, you wrote: The series-fed types (usually fiberglass at these frequencies) *will* tilt their patterns when moving away from their design frequency. Laryn K8TVZ The good news is that the pattern tilts down when used at frequencies below the design frequency. The big question is by how much. Would be easy to calculate in NECWin if I could only get a good NEC model for the coaxial colinear array. I'm not quite expert enough in NEC to figure out how to create that model. Bob NO6B Yahoo! Groups Links No virus found in this incoming message. Checked by AVG. Version: 8.0.100 / Virus Database: 270.0.0/1489 - Release Date: 6/7/2008 11:17 AM
RE: [Repeater-Builder] Re: antenna suggestions for 440mhz
So throwing in an RX pre-amp wouldn't help much either, then... hehehehe Thanks, Bob! Mark - N9WYS -Original Message- From: Repeater-Builder@yahoogroups.com On Behalf Of [EMAIL PROTECTED] Sent: Saturday, June 07, 2008 11:35 AM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Re: antenna suggestions for 440mhz At 6/7/2008 08:22, you wrote: In fear of moving off topic... I'd like to ask how one can determine the electrical downtilt of an antenna? I just put into service a RSF/Celwave Super StationmasterR Model 10017-6 that is designed for 925-960 MHz on my 927.5250 repeater. The added gain factor of the antenna (an additional 4dBd over what was previously in place - a Decibel DB586-Y) does not seem to benefit the receive (at 902 MHz). I gained what seems like a little extra receive range, but not equal to what I seem to have gained in transmit coverage. Downtilt shouldn't vary too much between TX RX freqs. What's probably happening is that the increased gain is resulting in increased noise pickup from the horizon as well as signal. Changes in gain directly affect your transmit ERP, but they don't necessarily translate directly into increased RX range depending on where the noise is. Slightly related: I once maintained a repeater at a residential mountain site with lots of elevation but no clear view to the ground (trees in the way). The site RF characteristics on 2 meters were somewhat like an RF black hole: RF could get in but was hard to get out. We needed ~200 watts of TX power on the repeater to balance TX RX with a 50 watt mobile user. I believe the reason was foliage absorption combined with a high noise floor down below. Around here antenna noise temperatures on 2 meters are typically ~3000 K. However this site had much lower noise - it's the only site around here where adding a preamp to a G.E. receiver resulted in actual system sensitivity improvement. So with biological attenuation surrounding the site, both signal noise approaching the site were attenuated. With the low noise RX, the net reduction in S/N due to the attenuation was minimal. However, the attenuation directly reduced the TX signal leaving the site. So the net effect was the site heard OK but TXing out was difficult. Bob NO6B Yahoo! Groups Links No virus found in this incoming message. Checked by AVG. Version: 8.0.100 / Virus Database: 270.0.0/1489 - Release Date: 6/7/2008 11:17 AM
RE: [Repeater-Builder] Antenna Downtilt (WAS Re: antenna suggestions for 440mhz)
The Stationmaster is a collinear array (I believe that is how it is best described?) and not a multiple folded dipole array; so the elements are not fed in parallel but rather in series. If I was reading the thread correctly, parallel fed dipole arrays are not susceptible to frequency-dependent downtilt, whereas collinear arrays can be. Or did I misread? Mark - N9WYS From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Gary Glaenzer Sent: Saturday, June 07, 2008 11:27 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Re: antenna suggestions for 440mhz well, as has been commented, if it was not ordered with down-tilt, there will be none at any freqency you put into it, as all elements are exactly in-phase since the method of acheiving down-tilt was to make the feeds to the lower elements shorter, if it originall had down-tilt I'd venture that the down-tilt would decrease with decreasing frequency (less phase difference) I think. Gary - Original Message - From: n9wys mailto:[EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Saturday, June 07, 2008 11:17 AM Subject: RE: [Repeater-Builder] Re: antenna suggestions for 440mhz Thanks Gary. I was looking for more of a generic answer along the lines of, As you move down in frequency, electrical downtilt . (Enter INCREASES or DECREASES here as necessary -- if this is the case.) I am also wondering if 20MHz on the receive is far enough off to cause a problem. Remember, this stick is within 1 MHz of the bottom of its range on TRANSMIT, and well below it on Receive. So this is why I ask about adverse effects. Not that I'm thinking of scrapping it, but I'm just trying to figure out why I didn't gain the receive sensitivity/coverage I thought I would with the added gain. With all this talk about downtilt... if that is what is happening here, that would explain why I'm experiencing what I am on receive. Or am I worrying about gremlins?? Mark -N9WYS -Original Message- From: Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com On Behalf Of Gary Glaenzer Sent: Saturday, June 07, 2008 10:30 AM To: Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com Subject: Re: [Repeater-Builder] Re: antenna suggestions for 440mhz down-tilt is specified when ordering the unit other than the original paperwork, the only method would be to have it tested on a test range and that would probably cost more than ordering a new one Gary - Original Message - From: n9wys To: Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com Sent: Saturday, June 07, 2008 10:22 AM Subject: RE: [Repeater-Builder] Re: antenna suggestions for 440mhz In fear of moving off topic... I'd like to ask how one can determine the electrical downtilt of an antenna? I just put into service a RSF/Celwave Super StationmasterR Model 10017-6 that is designed for 925-960 MHz on my 927.5250 repeater. The added gain factor of the antenna (an additional 4dBd over what was previously in place - a Decibel DB586-Y) does not seem to benefit the receive (at 902 MHz). I gained what seems like a little extra receive range, but not equal to what I seem to have gained in transmit coverage. This discussion thread leads me to wonder if maybe some electrical downtilt may be affecting the receive frequency? Is this possible? Antennas are not my strong point. ;-) Thanks, Mark - N9WYS Yahoo! Groups Links No virus found in this incoming message. Checked by AVG. Version: 8.0.100 / Virus Database: 270.0.0/1489 - Release Date: 6/7/2008 11:17 AM No virus found in this incoming message. Checked by AVG. Version: 8.0.100 / Virus Database: 270.0.0/1489 - Release Date: 6/7/2008 11:17 AM image001.jpg
RE: [Repeater-Builder] Re: antenna suggestions for 440mhz
I was looking for more of a generic answer along the lines of, As you move down in frequency, electrical downtilt . (Enter INCREASES or DECREASES here as necessary -- if this is the case.) I know you wanted a short answer, but this got kind of long-winded... A series-fed antenna will have more downtilt as you go down in operating frequency, and likewise more uptilt as you go up in operating frequency. I vaguely recall seeing a plot of uptilt/downtilt in an antenna catalog back in the early 80's (maybe Antenna Specialists) that showed a little less than 2 degrees of beamtilt per 10 MHz of frequency change for a collinear omni at UHF. Considering a 10 dB stick has a half-power beamwidth of only 7 degrees, the tilt can become very noticible very quickly as you get out of band. In contrast, a 6 dB stick has a much wider beamwidth (around 15 degrees), so the uptilt/downtilt is less of an issue. If your antenna has a fairly wide beamwidth, unless your antenna height is extremely high and the target coverage area is very close to the tower site, purposely adding downtilt is rarely necessary for the purposes of covering the target area (for the purposes of putting less power on the horizon for interference reduction, that's a different story). Antennas that are up that high tend to have clear line-of-sight to the close-in coverage areas, and like they say up on 24 GHz, if you can see 'em, you can work 'em. As a trig refresher, you can determine how far out from the tower site the bottom of the main lobe (-3 dB point) hits the ground using the following equation (assumes flat earth, which is good enough for what we're doing): d = h / tan(b/2 + t) where h = antenna height b = half-power beamwidth in degrees t = downtilt in degrees, uptilt being a negative number d = radial distance from tower base So for a 10 dB stick (7 degree beamwidth), with no downtilt, at 1000 feet: d = 1000 / tan (7/2 + 0) d = 1000 / tan (3.5) d = 0.06116 d = 16,350 (3.1 miles) If you add 3 degrees of downtilt, d becomes 1.7 miles. The trade-off, however, is that now your gain on the horizon is reduced to something closer to 7 dB instead of the full 10 dB, so although you've improved your close-in coverage, the long-distance performance suffers. So in this example, at distances less than 3.1 miles from the tower, the users aren't in the main lobe. This may or may not pose a problem. If they're mobile, or even outdoor handheld, they probably won't have problems because the repeater antenna probably has clear line of sight to them (since they're less than 3 miles away, and the repeater antenna is 1000' up), so even if they're somewhere in the nulls and minor lobes, they'll probably do OK. Building penetration is whole different issue, as nulls may be on the order of 30 dB deep or more (some may be perfect nulls in theory, but in the real world that doesn't happen due to both near-field and far-field reflections). It would be perfectly understandable to learn that you have better indoor handheld coverage 4 miles out than you do 2 miles out in this example. Keep in mind when you do these kind of beamwidth touchdown analyses that you need to leave some wiggle room to account for antenna flexing, mounting imperfections, and other real-world limitations that will cause the antenna to be something other than perfectly plumb. It should also be obvious that if there is too much uptilt the main lobe never hits the ground, which is fine if you want to talk to space aliens... I have a repeater (440) with an antenna (PD1151, 12 degree beamwidth) at 700' above ground level. I have a warehouse about 3/4 of a mile away from the repeater at roughly the same ground elevation as the repeater (within 50 feet or so). The warehouse is cinderblock with steel beams and a metal roof, no windows. If I stand in the doorway to the warehouse I can see the repeater antenna, yet there are spots inside the warehouse where people tell me I'm noisy running a 4-watt handheld. In this example, I'm below the main lobe which hits the ground at about 1.25 miles. However, with that same handheld, I can sit in my living room 20 miles away and work the repeater fine. In ham radio, maximizing total coverage area is often the goal when the population density is fairly uniform (and when you think about population density, you can't limit it to just where people live, you have to consider where they work, where they go on weekends, the travel routes they use in their communits as well as interstates and other highways used by non-residents, etc. - it's not as simple as it might seem, but I digress...). Since area varies with the radial distance squared, giving up some close-in coverage perfection is usually an acceptable trade-off if it gets you another few miles out on the horizon. Let's say, for example, you have a nice high site and your repeater has a 50 mile coverage radius with a zero-downtilt antenna. That's about 7854 square miles.
Re: [Repeater-Builder] Re: antenna suggestions for 440mhz
At 6/7/2008 10:24, you wrote: Hi Guys, My question is have you ever put up a downtilt antenna to replace an antenna of the same configuration, i.e. gain, etc. and have been able to say with 100% certainly that the downtilt worked? My 911 center went to high band for fire. Within a few days Industry Canada was on the phone saying that our cross band repeater from low band to high band was severely causing interference to a fire department in Canada. While I was on the phone, I would hear our units coming in loud and clear at the Industry Canada Office. Make a long story short, I had many conference calls between the FCC and Industry Canada and I agreed to Canadas request to mount a down tilt antenna at the same location of the existing antenna. A week later the antenna was installed and there was NO difference in signal quality from the Alma Hill New York Tower 2,558 to the location in Canada some 125 miles away. I cut the amp out and used the six watt exciter and I could still hear the signal over the phone from Canada just fine. We finally negotiated a frequency change and I walked away knowing that downtilt in this application didnt work. I might add that this was not inversion or ducking, the signal was there 24 X7 day after day. What was the antenna gain how much downtilt? If you starting with only 7 dBi then put 3° of downtilt on it, you're not going to drop the on-horizon gain very much. Since dropping the power from (amp) watts to 6 watts (let's say that's 10 dB?) didn't make a difference, you'd almost have to add enough downtilt to put the antenna's 1st null on the horizon for downtilt to work in this case. Unless you're dealing with a very high gain antenna, doing that would also cut out some of your desired coverage. Bob NO6B P.S.: you will definitely get ducking if your repeater is in their migratory path ;)
Re: [Repeater-Builder] Re: antenna suggestions for 440mhz
Hello Mark - I wondering at what height your antenna is mounted? Or going to be mounted - Dave / NØATH - Original Message - From: n9wys To: Repeater-Builder@yahoogroups.com Sent: Saturday, June 07, 2008 11:17 AM Subject: RE: [Repeater-Builder] Re: antenna suggestions for 440mhz Thanks Gary. I was looking for more of a generic answer along the lines of, As you move down in frequency, electrical downtilt . (Enter INCREASES or DECREASES here as necessary -- if this is the case.) I am also wondering if 20MHz on the receive is far enough off to cause a problem. Remember, this stick is within 1 MHz of the bottom of its range on TRANSMIT, and well below it on Receive. So this is why I ask about adverse effects. Not that I'm thinking of scrapping it, but I'm just trying to figure out why I didn't gain the receive sensitivity/coverage I thought I would with the added gain. With all this talk about downtilt... if that is what is happening here, that would explain why I'm experiencing what I am on receive. Or am I worrying about gremlins?? Mark -N9WYS -Original Message- From: Repeater-Builder@yahoogroups.com On Behalf Of Gary Glaenzer Sent: Saturday, June 07, 2008 10:30 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Re: antenna suggestions for 440mhz down-tilt is specified when ordering the unit other than the original paperwork, the only method would be to have it tested on a test range and that would probably cost more than ordering a new one Gary - Original Message - From: n9wys To: Repeater-Builder@yahoogroups.com Sent: Saturday, June 07, 2008 10:22 AM Subject: RE: [Repeater-Builder] Re: antenna suggestions for 440mhz In fear of moving off topic... I'd like to ask how one can determine the electrical downtilt of an antenna? I just put into service a RSF/Celwave Super StationmasterR Model 10017-6 that is designed for 925-960 MHz on my 927.5250 repeater. The added gain factor of the antenna (an additional 4dBd over what was previously in place - a Decibel DB586-Y) does not seem to benefit the receive (at 902 MHz). I gained what seems like a little extra receive range, but not equal to what I seem to have gained in transmit coverage. This discussion thread leads me to wonder if maybe some electrical downtilt may be affecting the receive frequency? Is this possible? Antennas are not my strong point. ;-) Thanks, Mark - N9WYS Yahoo! Groups Links No virus found in this incoming message. Checked by AVG. Version: 8.0.100 / Virus Database: 270.0.0/1489 - Release Date: 6/7/2008 11:17 AM No virus found in this incoming message. Checked by AVG. Version: 8.0.100 / Virus Database: 270.0.0/1489 - Release Date: 6/7/2008 11:17 AM
[Repeater-Builder] Spectra Radio
I Have A Spectra D43KXA7JA5BK . How Can I Fix To Make It Scan My Freq. Do I Need To Reprogrammed ? Or Change The MLM Module ? Or What ? Someone . PLEASE HELP !! Thanks
Re: [Repeater-Builder] Spectra Radio
You need to add the channels to a scan list to get them to be scanned. Whether your radio will scan or not is controlled by the firmware. Some will, some won't. It requires programming to enter the scan list and test it. If the radio's feature-set and firmware won't support it, the programming software will let you know. A new blank MLM will support scanning, but replacing it is not just a matter of plugging it in and turning it on. All sorts of other things need to be done. A used MLM may create more problems than it cures. Once the scan list has been set up, some control heads (i.e. A7 and A9) will let you delete some channels temporarily, until the radio's power is removed, but from the model number you supplied, I don't think yours can do that. Bob M. == --- On Sat, 6/7/08, r_wedgeworth [EMAIL PROTECTED] wrote: From: r_wedgeworth [EMAIL PROTECTED] Subject: [Repeater-Builder] Spectra Radio To: Repeater-Builder@yahoogroups.com Date: Saturday, June 7, 2008, 3:15 PM I Have A Spectra D43KXA7JA5BK . How Can I Fix To Make It Scan My Freq. Do I Need To Reprogrammed ? Or Change The MLM Module ? Or What ? Someone . PLEASE HELP !! Thanks
RE: [Repeater-Builder] Re: antenna suggestions for 440mhz
Jeff Thank you - you did an excellent job of explaining / writing the answer. Now save it, so you can cut and paste it next month when someone asks the question again. I am a Spirit Dealer, and at New-Tronics (the parent company for Hustler Antennas too), we actually make the antennas after you order them, cut and stamp the frequency on them, and ship them out, including custom to the ham band frequencies. They are end fed (what you call series fed), like the old Stationmasters. Frankly, I became a Spirit dealer because I could buy them cut for any frequency including the ham band from 420 - 450 in 10 MHz segments, (the last antenna manufacturer that I know of that will do that) and the HD models held up as good as Stationmasters. I have never had one fail through a winter. They radiate as well (all personal perception of signal strengths, but real piece of mind with almost zero reflected power in the ham frequencies) so I am a happy camper. The radial ice on the fiberglass sometimes falls off if the fiberglass will whip enough, but the HD and EXTRA HD models just don't bend enough. I don't know if the picture will come through or not - but it is the close antenna on 441 MHz, with the 420 MHz Kathreine radomed yagi at the bottom. Note the radial ice on the exposed element antennas. Imagine what's happening to a short via water with that radial ice all over it. Bill - W6CBS Well said. Thank you Jeff. Chuck WB2EDV - Original Message - From: Jeff DePolo [EMAIL PROTECTED] mailto:jd0%40broadsci.com com To: Repeater-Builder@ mailto:Repeater-Builder%40yahoogroups.com yahoogroups.com Sent: Saturday, June 07, 2008 9:25 AM Subject: RE: [Repeater-Builder] Re: antenna suggestions for 440mhz First off you will definitely loose some of the gain from the original rated specs. About 1.5 - 2 Dbd. is what I'd expect...Maybe a little worse depending on where the antenna was originally cut for... For example, If the antenna was originally built for say a 454.xxx freq (center freq) the loss would be less at 442.xxx than one that had been built for 467.xxx. The antenna typically has a 20Mhz. bandwidth, +/- 10Mhz each side of center freq so you can see that one cut for the upper 460-ish range would be a little worse than the 450-ish freq. DB404/408/420 antennas were never cut to frequency - they were sold in frequency ranges. For example, a DB408-A is 406-420, DB408-B is 450-470, etc. So the closest one to 440 would be a DB4xx-B. If you ordered an antenna for 454.575, you would get a -B series antenna. In the wayback days, sometimes they would even stamp the label with the exact frequency you ordered, but the antenna wasn't cut for that frequency, they just marked it to identify the requested frequency. Nowadays they don't even bother to do that, the sticker will just say 450-470 MHz and it will come with a return loss sweep showing its performance across the entire band. The more bays, the worse the VSWR will be (speaking in very general terms here) as you operate these types of antennas out of band. For example, a 408-B will likely have better return loss than a 420-B when used at 440 MHz. The next thing that would change would be the downtilt rating. No, parallel-fed antennas do NOT suffer uptilt/downtilt as frequency is varied unless the harness was special-ordered for factory downtilt. If the antenna wasn't ordered with downtilt, all of the elements are fed in phase, and they will always be in phase regardless of frequency. The peak gain will be reduced as you operate them away from their design range as more power ends up in the usually-undesired sidelobes, but the main lobe will still be on the horizon. Series-fed antennas (like Stationmasters) will have the elevation pattern (downtilt/uptilt) affected as frequency changes, because the further up the antenna you go, the more and more the radiating elements end up being out of phase compared to the lower ones, thereby creating the uptilt/downtilt. This issue comes up so many times, and is so misunderstood, that there should probably be a FAQ about it on the web site... I like the DB's but unsure how bad the 450mhz matches when trying to use it down at 440.000mhz. I have 404's, 408's, 411's, 413's, and 420's in stock, all in the B version, a few A version, and a few S-440-450 ham-band versions which they don't make any more. I can sweep one if you want (please don't make me drag all of them out of the warehouse to test). Email direct if you're interested. --- Jeff WN3A No virus found in this incoming message. Checked by AVG. Version: 8.0.100 / Virus Database: 270.0.0/1486 - Release Date: 6/5/2008 6:29 PM image002.jpg
RE: [Repeater-Builder] Re: antenna suggestions for 440mhz
I guess I'm going to have to post the picture to the group... it's relevant to good repeater building in rugged ice conditions... W6CBS - CBS Bill -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Bill Hudson Sent: Saturday, June 07, 2008 2:30 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Re: antenna suggestions for 440mhz Jeff Thank you - you did an excellent job of explaining / writing the answer. Now save it, so you can cut and paste it next month when someone asks the question again. I am a Spirit Dealer, and at New-Tronics (the parent company for Hustler Antennas too), we actually make the antennas after you order them, cut and stamp the frequency on them, and ship them out, including custom to the ham band frequencies. They are end fed (what you call series fed), like the old Stationmasters. Frankly, I became a Spirit dealer because I could buy them cut for any frequency including the ham band from 420 - 450 in 10 MHz segments, (the last antenna manufacturer that I know of that will do that) and the HD models held up as good as Stationmasters. I have never had one fail through a winter. They radiate as well (all personal perception of signal strengths, but real piece of mind with almost zero reflected power in the ham frequencies) so I am a happy camper. The radial ice on the fiberglass sometimes falls off if the fiberglass will whip enough, but the HD and EXTRA HD models just don't bend enough. I don't know if the picture will come through or not - but it is the close antenna on 441 MHz, with the 420 MHz Kathreine radomed yagi at the bottom. Note the radial ice on the exposed element antennas. Imagine what's happening to a short via water with that radial ice all over it. Bill - W6CBS Well said. Thank you Jeff. Chuck WB2EDV - Original Message - From: Jeff DePolo [EMAIL PROTECTED] mailto:jd0%40broadsci.com To: Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com Sent: Saturday, June 07, 2008 9:25 AM Subject: RE: [Repeater-Builder] Re: antenna suggestions for 440mhz First off you will definitely loose some of the gain from the original rated specs. About 1.5 - 2 Dbd. is what I'd expect...Maybe a little worse depending on where the antenna was originally cut for... For example, If the antenna was originally built for say a 454.xxx freq (center freq) the loss would be less at 442.xxx than one that had been built for 467.xxx. The antenna typically has a 20Mhz. bandwidth, +/- 10Mhz each side of center freq so you can see that one cut for the upper 460-ish range would be a little worse than the 450-ish freq. DB404/408/420 antennas were never cut to frequency - they were sold in frequency ranges. For example, a DB408-A is 406-420, DB408-B is 450-470, etc. So the closest one to 440 would be a DB4xx-B. If you ordered an antenna for 454.575, you would get a -B series antenna. In the wayback days, sometimes they would even stamp the label with the exact frequency you ordered, but the antenna wasn't cut for that frequency, they just marked it to identify the requested frequency. Nowadays they don't even bother to do that, the sticker will just say 450-470 MHz and it will come with a return loss sweep showing its performance across the entire band. The more bays, the worse the VSWR will be (speaking in very general terms here) as you operate these types of antennas out of band. For example, a 408-B will likely have better return loss than a 420-B when used at 440 MHz. The next thing that would change would be the downtilt rating. No, parallel-fed antennas do NOT suffer uptilt/downtilt as frequency is varied unless the harness was special-ordered for factory downtilt. If the antenna wasn't ordered with downtilt, all of the elements are fed in phase, and they will always be in phase regardless of frequency. The peak gain will be reduced as you operate them away from their design range as more power ends up in the usually-undesired sidelobes, but the main lobe will still be on the horizon. Series-fed antennas (like Stationmasters) will have the elevation pattern (downtilt/uptilt) affected as frequency changes, because the further up the antenna you go, the more and more the radiating elements end up being out of phase compared to the lower ones, thereby creating the uptilt/downtilt. This issue comes up so many times, and is so misunderstood, that there should probably be a FAQ about it on the web site... I like the DB's but unsure how bad the 450mhz matches when trying to use it down at 440.000mhz. I have 404's, 408's, 411's, 413's, and 420's in stock, all in the B version, a few A version, and a few S-440-450 ham-band versions which they don't make any more. I can sweep one if you want (please don't make me drag all of them out of the warehouse to test). Email direct if you're
[Repeater-Builder] Re: antenna suggestions for 440mhz
OK - I put 3 pictures in the photos section at Yahoo Groups - repeater builders. its at the end of the pictures because the album is W6CBS - Spirit Antennas in Snow... Bill - W6CBS --- In Repeater-Builder@yahoogroups.com, Bill Hudson [EMAIL PROTECTED] wrote: I guess I'm going to have to post the picture to the group... it's relevant to good repeater building in rugged ice conditions... W6CBS - CBS Bill -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Bill Hudson Sent: Saturday, June 07, 2008 2:30 PM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Re: antenna suggestions for 440mhz Jeff Thank you - you did an excellent job of explaining / writing the answer. Now save it, so you can cut and paste it next month when someone asks the question again. I am a Spirit Dealer, and at New-Tronics (the parent company for Hustler Antennas too), we actually make the antennas after you order them, cut and stamp the frequency on them, and ship them out, including custom to the ham band frequencies. They are end fed (what you call series fed), like the old Stationmasters. Frankly, I became a Spirit dealer because I could buy them cut for any frequency including the ham band from 420 - 450 in 10 MHz segments, (the last antenna manufacturer that I know of that will do that) and the HD models held up as good as Stationmasters. I have never had one fail through a winter. They radiate as well (all personal perception of signal strengths, but real piece of mind with almost zero reflected power in the ham frequencies) so I am a happy camper. The radial ice on the fiberglass sometimes falls off if the fiberglass will whip enough, but the HD and EXTRA HD models just don't bend enough. I don't know if the picture will come through or not - but it is the close antenna on 441 MHz, with the 420 MHz Kathreine radomed yagi at the bottom. Note the radial ice on the exposed element antennas. Imagine what's happening to a short via water with that radial ice all over it. Bill - W6CBS Well said. Thank you Jeff. Chuck WB2EDV - Original Message - From: Jeff DePolo [EMAIL PROTECTED] mailto:jd0%40broadsci.com To: Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com Sent: Saturday, June 07, 2008 9:25 AM Subject: RE: [Repeater-Builder] Re: antenna suggestions for 440mhz First off you will definitely loose some of the gain from the original rated specs. About 1.5 - 2 Dbd. is what I'd expect...Maybe a little worse depending on where the antenna was originally cut for... For example, If the antenna was originally built for say a 454.xxx freq (center freq) the loss would be less at 442.xxx than one that had been built for 467.xxx. The antenna typically has a 20Mhz. bandwidth, +/- 10Mhz each side of center freq so you can see that one cut for the upper 460-ish range would be a little worse than the 450-ish freq. DB404/408/420 antennas were never cut to frequency - they were sold in frequency ranges. For example, a DB408-A is 406-420, DB408-B is 450-470, etc. So the closest one to 440 would be a DB4xx-B. If you ordered an antenna for 454.575, you would get a -B series antenna. In the wayback days, sometimes they would even stamp the label with the exact frequency you ordered, but the antenna wasn't cut for that frequency, they just marked it to identify the requested frequency. Nowadays they don't even bother to do that, the sticker will just say 450-470 MHz and it will come with a return loss sweep showing its performance across the entire band. The more bays, the worse the VSWR will be (speaking in very general terms here) as you operate these types of antennas out of band. For example, a 408-B will likely have better return loss than a 420-B when used at 440 MHz. The next thing that would change would be the downtilt rating. No, parallel-fed antennas do NOT suffer uptilt/downtilt as frequency is varied unless the harness was special-ordered for factory downtilt. If the antenna wasn't ordered with downtilt, all of the elements are fed in phase, and they will always be in phase regardless of frequency. The peak gain will be reduced as you operate them away from their design range as more power ends up in the usually-undesired sidelobes, but the main lobe will still be on the horizon. Series-fed antennas (like Stationmasters) will have the elevation pattern (downtilt/uptilt) affected as frequency changes, because the further up the antenna you go, the more and more the radiating elements end up being out of phase compared to the lower ones, thereby creating the uptilt/downtilt. This issue comes up so many times, and is so misunderstood, that there should probably be a FAQ about it on the web site... I like the DB's but unsure how bad the
RE: [Repeater-Builder] Antenna Downtilt (WAS: antenna suggestions for 440mhz)
HI, Jeff. I realize that yours was a rather lengthy reply, but I appreciate it! Anyway, in answer to your inquiry the specs on the antenna are: Vertical Beamwidth: 6° Gain: 10dBd If you want the spec sheet, I can send it. -Original Message- From: Repeater-Builder@yahoogroups.com On Behalf Of Jeff DePolo (snip) I know you wanted a short answer, but this got kind of long-winded... (much snippage) What is the advertised gain and beamwidth of the antenna? --- Jeff WN3A Yahoo! Groups Links No virus found in this incoming message. Checked by AVG. Version: 8.0.100 / Virus Database: 270.0.0/1489 - Release Date: 6/7/2008 11:17 AM
RE: [Repeater-Builder] Re: antenna suggestions for 440mhz
Hi, Dave, It is atop a building at 240 ft AGL the tallest building in Joliet. wink Mark N9WYS From: Repeater-Builder@yahoogroups.com On Behalf Of N0ATH Hello Mark - I wondering at what height your antenna is mounted? Or going to be mounted - Dave / NØATH
Re: [Repeater-Builder] Re: antenna suggestions for 440mhz
No, parallel-fed antennas do NOT suffer uptilt/downtilt as frequency is varied unless the harness was special-ordered for factory downtilt. If the antenna wasn't ordered with downtilt, all of the elements are fed in phase, and they will always be in phase regardless of frequency. Jeff, the pattern depends on both phasing and spacing. As frequency drops, the interelement phasing, expressed in degrees, remains the same, but the spacing, expressed in degrees or wavelengths, drops. If you model a colinear array of parallel-fed dipoles in an antenna software program, and don't scale the dimensions as you scale the frequency, you'll see the main lobe shift up or down, and butterfly lobes appear, as you get a few per cent off-frequency. In an extreme case, a pair of vertical colinear dipoles fed in phase with half-wave spacing has the familiar big lobe toward the horizon. As frequency rises, the pattern degrades until, at a frequency of 2X, it becomes an end-fire array, with most energy directed straight up and down. This happens with no change in phasing or spacing. 73, Paul, AE4KR
Re: [Repeater-Builder] Re: antenna suggestions for 440mhz
At 6/7/2008 17:18, you wrote: No, parallel-fed antennas do NOT suffer uptilt/downtilt as frequency is varied unless the harness was special-ordered for factory downtilt. If the antenna wasn't ordered with downtilt, all of the elements are fed in phase, and they will always be in phase regardless of frequency. Jeff, the pattern depends on both phasing and spacing. As frequency drops, the interelement phasing, expressed in degrees, remains the same, but the spacing, expressed in degrees or wavelengths, drops. If you model a colinear array of parallel-fed dipoles in an antenna software program, and don't scale the dimensions as you scale the frequency, you'll see the main lobe shift up or down, and butterfly lobes appear, as you get a few per cent off-frequency. I don't see the main lobe shift up or down with frequency in the NEC simulations; it stays on the horizon. It does get narrower at higher frequencies wider at lower frequencies. The butterfly side lobes appear mainly at higher frequencies. Bob NO6B
Re: [Repeater-Builder] Re: antenna suggestions for 440mhz
Paul, Perhaps you can now explain how the radiation pattern changes on a single center fed, 1/2 wave length simple dipole when the frequency is changed both above and below the dipole resonant frequency, and how that relates to the statements you have made below. 73 Allan Crites WA9ZZU Paul Plack [EMAIL PROTECTED] wrote: No, parallel-fed antennas do NOT suffer uptilt/downtilt as frequency is varied unless the harness was special-ordered for factory downtilt. If the antenna wasn't ordered with downtilt, all of the elements are fed in phase, and they will always be in phase regardless of frequency. Jeff, the pattern depends on both phasing and spacing. As frequency drops, the interelement phasing, expressed in degrees, remains the same, but the spacing, expressed in degrees or wavelengths, drops. If you model a colinear array of parallel-fed dipoles in an antenna software program, and don't scale the dimensions as you scale the frequency, you'll see the main lobe shift up or down, and butterfly lobes appear, as you get a few per cent off-frequency. In an extreme case, a pair of vertical colinear dipoles fed in phase with half-wave spacing has the familiar big lobe toward the horizon. As frequency rises, the pattern degrades until, at a frequency of 2X, it becomes an end-fire array, with most energy directed straight up and down. This happens with no change in phasing or spacing. 73, Paul, AE4KR
Re: [Repeater-Builder] Re: antenna suggestions for 440mhz
Allan, I question the relevance, but here goes. I just modeled an ordinary half-wave dipole in free space in EZNEC. 20 MHz low at 450 MHz is about 4.5%. At 4.5% above design frequency, the difference in the pattern of the single dipole is negligible, and the gain rises 0.04 dB. At 4.5% below design frequency, the difference in the pattern of the single dipole is negligible, and the gain drops 0.04 dB. For entertainment's sake, I modeled it at 100% above design frequency. Impedance is 1754 ohms, for an SWR of 44.9:1, but assuming you could match it without loss, you'd enjoy 1.79 dB gain at the horizon, slightly elongating the major lobes in a polar plot. Is it your position that combining a bunch of dipoles in a colinear phased array does not change their behavior compared to a single dipole? If that's true, we're all been wasting lots of money. By the way, my recent modeling experience has been almost exclusively with half-wave dipoles, fed in-phase, spaced a half-wave apart, for applications involving single-site low-band repeaters using separate antennas to achieve isolation through vertical separation. In this application, the null in the vertical axis is much more important than the beamwidth at the horizon. I acknowledge that the available bandwidth before the pattern decays may be different in the commercial antennas being discussed. If someone can tell me the spacing and phasing of the elements in the popular folded-dipole arrays, I'll try modeling them at some point, and see how they behave differently from my application. I've also played a little with antennas spaced at 3/8- and 5/8-wave, with phasing leading or lagging by 45 degrees, and some very interesting fill patterns can be created. 73, Paul, AE4KR - Original Message - From: allan crites To: Repeater-Builder@yahoogroups.com Sent: Saturday, June 07, 2008 7:14 PM Subject: Re: [Repeater-Builder] Re: antenna suggestions for 440mhz Paul, Perhaps you can now explain how the radiation pattern changes on a single center fed, 1/2 wave length simple dipole when the frequency is changed both above and below the dipole resonant frequency, and how that relates to the statements you have made below. 73 Allan Crites WA9ZZU Paul Plack [EMAIL PROTECTED] wrote: No, parallel-fed antennas do NOT suffer uptilt/downtilt as frequency is varied unless the harness was special-ordered for factory downtilt. If the antenna wasn't ordered with downtilt, all of the elements are fed in phase, and they will always be in phase regardless of frequency. Jeff, the pattern depends on both phasing and spacing. As frequency drops, the interelement phasing, expressed in degrees, remains the same, but the spacing, expressed in degrees or wavelengths, drops. If you model a colinear array of parallel-fed dipoles in an antenna software program, and don't scale the dimensions as you scale the frequency, you'll see the main lobe shift up or down, and butterfly lobes appear, as you get a few per cent off-frequency. In an extreme case, a pair of vertical colinear dipoles fed in phase with half-wave spacing has the familiar big lobe toward the horizon. As frequency rises, the pattern degrades until, at a frequency of 2X, it becomes an end-fire array, with most energy directed straight up and down. This happens with no change in phasing or spacing. 73, Paul, AE4KR
Re: [Repeater-Builder] Re: antenna suggestions for 440mhz
Paul, No, it is not my position that combining a bunch of dipoles in a co-linear array does not change their behavior compared to a single dipole. I was interested in having the explanation made to show that radiation pattern down tilt of a parallel feed multiple dipole antenna is negligible or non-existent when operated at a frequency not significantly below the design frequency when all dipoles are fed equally in phase. Changes in gain when a multiple dipole antenna is operated beyond the designed frequency range is an altogether different subject related to impedance matching and the manufacturer's honesty. Thank you. 73 Allan Crites WA9ZZU Paul Plack [EMAIL PROTECTED] wrote: Allan, I question the relevance, but here goes. I just modeled an ordinary half-wave dipole in free space in EZNEC. 20 MHz low at 450 MHz is about 4.5%. At 4.5% above design frequency, the difference in the pattern of the single dipole is negligible, and the gain rises 0.04 dB. At 4.5% below design frequency, the difference in the pattern of the single dipole is negligible, and the gain drops 0.04 dB. For entertainment's sake, I modeled it at 100% above design frequency. Impedance is 1754 ohms, for an SWR of 44.9:1, but assuming you could match it without loss, you'd enjoy 1.79 dB gain at the horizon, slightly elongating the major lobes in a polar plot. Is it your position that combining a bunch of dipoles in a colinear phased array does not change their behavior compared to a single dipole? If that's true, we're all been wasting lots of money. By the way, my recent modeling experience has been almost exclusively with half-wave dipoles, fed in-phase, spaced a half-wave apart, for applications involving single-site low-band repeaters using separate antennas to achieve isolation through vertical separation. In this application, the null in the vertical axis is much more important than the beamwidth at the horizon. I acknowledge that the available bandwidth before the pattern decays may be different in the commercial antennas being discussed. If someone can tell me the spacing and phasing of the elements in the popular folded-dipole arrays, I'll try modeling them at some point, and see how they behave differently from my application. I've also played a little with antennas spaced at 3/8- and 5/8-wave, with phasing leading or lagging by 45 degrees, and some very interesting fill patterns can be created. 73, Paul, AE4KR - Original Message - From: allan crites To: Repeater-Builder@yahoogroups.com Sent: Saturday, June 07, 2008 7:14 PM Subject: Re: [Repeater-Builder] Re: antenna suggestions for 440mhz Paul, Perhaps you can now explain how the radiation pattern changes on a single center fed, 1/2 wave length simple dipole when the frequency is changed both above and below the dipole resonant frequency, and how that relates to the statements you have made below. 73 Allan Crites WA9ZZU Paul Plack [EMAIL PROTECTED] wrote: No, parallel-fed antennas do NOT suffer uptilt/downtilt as frequency is varied unless the harness was special-ordered for factory downtilt. If the antenna wasn't ordered with downtilt, all of the elements are fed in phase, and they will always be in phase regardless of frequency. Jeff, the pattern depends on both phasing and spacing. As frequency drops, the interelement phasing, expressed in degrees, remains the same, but the spacing, expressed in degrees or wavelengths, drops. If you model a colinear array of parallel-fed dipoles in an antenna software program, and don't scale the dimensions as you scale the frequency, you'll see the main lobe shift up or down, and butterfly lobes appear, as you get a few per cent off-frequency. In an extreme case, a pair of vertical colinear dipoles fed in phase with half-wave spacing has the familiar big lobe toward the horizon. As frequency rises, the pattern degrades until, at a frequency of 2X, it becomes an end-fire array, with most energy directed straight up and down. This happens with no change in phasing or spacing. 73, Paul, AE4KR
