Re: [Repeater-Builder] DB212-3
NORM KNAPP nkn...@twowayradio.net wrote: Took down a set of DB212-3 dipoles in good shape with harness. I want to use them on 6m for a repeater antenna. I also want to add one additional dipole. I guess I will need to modify the harness and the dipoles as they are marked for 35.960 mhz I will be mounting all four (or 3) on one leg of a tower that is 4 feet on a face. Is it worth my while to go for the 4th dippole? The loops are 155 inches from tip to tip now. Looks like they need to be about 105 inches. Anyone with any tips, pointers or advise? Thanks Hi Norm...I've used a few sets of the db212s and can say that they are real hard to beat. If the tower is 3 sided use the -3 and shorten the trombones and harness. If the tower has 4 legs, use all 4 antennas and make up 3 harnesses for 2 antennas each. If you are in an area which has a lot of blowing sand, consider wrapping the trombones in good poly tape to reduce static. I know the antennas are grounded, but it does make a difference. Also, when placing the antennas on a tower, use one antenna stuffed between the other 2 to make a good field spacing of the antennas. This would result in a spacing of about 0.8 wavelength. Remember these antennas must be tuned against a suitable tower, not in free air, and a couple of wavelengths off the ground. If you don't understand the 3 pairs harness, remember that antennas 1 and2 will be paired; antennas 3 and 4 will be paired; and pair1,2 and pair 3,4 will be paired . Thus 3 pairs! good luck Jeff N5SXQ
[Repeater-Builder] DB212-3
Took down a set of DB212-3 dipoles in good shape with harness. I want to use them on 6m for a repeater antenna. I also want to add one additional dipole. I guess I will need to modify the harness and the dipoles as they are marked for 35.960 mhz I will be mounting all four (or 3) on one leg of a tower that is 4 feet on a face. Is it worth my while to go for the 4th dippole? The loops are 155 inches from tip to tip now. Looks like they need to be about 105 inches. Anyone with any tips, pointers or advise? Thanks
Re: [Repeater-Builder] DB212-3
I'd suggest using four if you have the tower real estate. Adjust each element individually on the tower up in the clear (not necessarily in the final location, but away from obstructions). I don't know how the harness was designed for three elements, but making one for four is easy. Each pigtail from the element must be the same length. Two elements combine with a tee, then a 35-ohm 1/4 wave matching section is needed. Do this for both halves of the antenna. Then take two equal lengths of 50-ohm cable to a final tee, then another 35-ohm matching section. From there it's 50-ohms. Chuck WB2EDV - Original Message - From: NORM KNAPP nkn...@twowayradio.net To: Repeater-Builder@yahoogroups.com Sent: Monday, August 30, 2010 11:51 AM Subject: [Repeater-Builder] DB212-3 Took down a set of DB212-3 dipoles in good shape with harness. I want to use them on 6m for a repeater antenna. I also want to add one additional dipole. I guess I will need to modify the harness and the dipoles as they are marked for 35.960 mhz I will be mounting all four (or 3) on one leg of a tower that is 4 feet on a face. Is it worth my while to go for the 4th dippole? The loops are 155 inches from tip to tip now. Looks like they need to be about 105 inches. Anyone with any tips, pointers or advise? Thanks
Re: [Repeater-Builder] DB212-3
Might take a little while, but 4 is what we will shoot for. If things go as planned, we will have all the tower space we want above 675' on an 850' tower. The legs are 4 solid steel and the face is at least 4' across. We still got to come up with the feedline and cans. I am building a 100watt mastr II for the task now. 73 - Original Message - From: Repeater-Builder@yahoogroups.com Repeater-Builder@yahoogroups.com To: Repeater-Builder@yahoogroups.com Repeater-Builder@yahoogroups.com Sent: Mon Aug 30 10:53:43 2010 Subject: Re: [Repeater-Builder] DB212-3 I'd suggest using four if you have the tower real estate. Adjust each element individually on the tower up in the clear (not necessarily in the final location, but away from obstructions). I don't know how the harness was designed for three elements, but making one for four is easy. Each pigtail from the element must be the same length. Two elements combine with a tee, then a 35-ohm 1/4 wave matching section is needed. Do this for both halves of the antenna. Then take two equal lengths of 50-ohm cable to a final tee, then another 35-ohm matching section. From there it's 50-ohms. Chuck WB2EDV - Original Message - From: NORM KNAPP nkn...@twowayradio.net mailto:nknapp%40twowayradio.net To: Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com Sent: Monday, August 30, 2010 11:51 AM Subject: [Repeater-Builder] DB212-3 Took down a set of DB212-3 dipoles in good shape with harness. I want to use them on 6m for a repeater antenna. I also want to add one additional dipole. I guess I will need to modify the harness and the dipoles as they are marked for 35.960 mhz I will be mounting all four (or 3) on one leg of a tower that is 4 feet on a face. Is it worth my while to go for the 4th dippole? The loops are 155 inches from tip to tip now. Looks like they need to be about 105 inches. Anyone with any tips, pointers or advise? Thanks
RE: [Repeater-Builder] DB212-3
In a previous life I managed the communications for a state police agency. We used 45 MHz for our main system and had forty some odd tower sites, almost all running DB212-3 antennas. Two of the sites were on 1000+ towers and used a single DB-212 element due to the large tower face and the great height. One was a repeater using a receive antenna at 1450' and a transmit antenna at 1350'. The other was a remote base station with the single loop at about 850'. As we were an investigative agency, almost all of the mobiles were using AM/FM disguise antennas. (Yeah, I know, but we were stuck with the band that the State Division of Communications had dictated...) Despite the radiating dummy load antennas, we had excellent mobile coverage in virtually all of the state. A consideration for DB212 antennas is that lining them up on one leg can make them pretty directional. For towers that were very close to the coast, I would put all three elements on a single leg, but skew them so that only one was pointed directly off of the leg. This seemed to give me a somewhat cardioid pattern, but with a little better pattern to the back than if all three elements were in line. Another consideration is that they were designed to be used on Rohn 45/55/65 sized tower. If you put them all on one leg, a larger tower face doesn't matter much except that the rearward pattern will likely have a larger null. Mounting them on all three legs of a larger face tower will result in reduced gain and a pretty messed up pattern. I don't know if I'd worry a whole lot about adding a fourth element- the three element antenna will deliver excellent results. Doug K4AC (Running for ARRL Southeastern Division Director- please check out my website at www.k4ac.com)
Re: [Repeater-Builder] DB212-3
Doug - Do you know how the phasing harness was constructed for the three-element version? I don't, and that's why I suggested to Norm that he go with four - the phasing harness is easy. Or, he could use two elements for transmit and one for receive. I don't know how much isolation he'll need, but he might just get away without a duplexer if there's enough tower. Chuck WB2EDV - Original Message - From: Doug Rehman d...@k4ac.com To: Repeater-Builder@yahoogroups.com Sent: Monday, August 30, 2010 2:28 PM Subject: RE: [Repeater-Builder] DB212-3 In a previous life I managed the communications for a state police agency. We used 45 MHz for our main system and had forty some odd tower sites, almost all running DB212-3 antennas. Two of the sites were on 1000+ towers and used a single DB-212 element due to the large tower face and the great height. One was a repeater using a receive antenna at 1450' and a transmit antenna at 1350'. The other was a remote base station with the single loop at about 850'. As we were an investigative agency, almost all of the mobiles were using AM/FM disguise antennas. (Yeah, I know, but we were stuck with the band that the State Division of Communications had dictated...) Despite the radiating dummy load antennas, we had excellent mobile coverage in virtually all of the state. A consideration for DB212 antennas is that lining them up on one leg can make them pretty directional. For towers that were very close to the coast, I would put all three elements on a single leg, but skew them so that only one was pointed directly off of the leg. This seemed to give me a somewhat cardioid pattern, but with a little better pattern to the back than if all three elements were in line. Another consideration is that they were designed to be used on Rohn 45/55/65 sized tower. If you put them all on one leg, a larger tower face doesn't matter much except that the rearward pattern will likely have a larger null. Mounting them on all three legs of a larger face tower will result in reduced gain and a pretty messed up pattern. I don't know if I'd worry a whole lot about adding a fourth element- the three element antenna will deliver excellent results. Doug K4AC (Running for ARRL Southeastern Division Director- please check out my website at www.k4ac.com)
Re: [Repeater-Builder] DB212-3
I'm glad somebody brought this up. I've got 2 of the DB212 antennas, without any phasing harness. The tower that the repeater is going up on is 90', wide spaced triangular tower (about 20' at the bottom 8' at the top). I'm just wondering if the work in building the harness, building the supports (the tower is not vertical, so I will have to 'make' a vertical support for them) is really worth the effort for an additional element. Seems I saw that with the 2 element configuration you only get about 2dB out of it. Doesn't seem like all the work is worth it. The reduced coverage off the back of the tower is not a concern. Just thought I'd throw this up into the wind. Thanks, Tim W5FN
RE: [Repeater-Builder] DB212-3
Unfortunately it’s been so many years since I handled one that I’m pretty foggy on the phasing harness. The manual on Repeater Builder http://www.repeater-builder.com/db/pdfs/db-212-assembly-and-mounting-instructions-(andrew).pdf shows the feeds from all three elements coming together, but doesn’t give a hint as to the length or impedance of each leg. If the original harness was retained, he should be able to reverse engineer it or shorten it if it’s still in good shape. I’ve got a DB212-1 sitting beside the house now to use on our clubhouse tower for a 6m PropNet beacon antenna. Too many projects… Doug K4AC (Running for ARRL Southeastern Division Director- please check out my website at www.k4ac.com) From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Chuck Kelsey Sent: Monday, August 30, 2010 2:35 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] DB212-3 Doug - Do you know how the phasing harness was constructed for the three-element version? I don't, and that's why I suggested to Norm that he go with four - the phasing harness is easy. Or, he could use two elements for transmit and one for receive. I don't know how much isolation he'll need, but he might just get away without a duplexer if there's enough tower. Chuck WB2EDV - Original Message - From: Doug Rehman d...@k4ac.com mailto:doug%40k4ac.com To: Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com Sent: Monday, August 30, 2010 2:28 PM Subject: RE: [Repeater-Builder] DB212-3 In a previous life I managed the communications for a state police agency. We used 45 MHz for our main system and had forty some odd tower sites, almost all running DB212-3 antennas. Two of the sites were on 1000+ towers and used a single DB-212 element due to the large tower face and the great height. One was a repeater using a receive antenna at 1450' and a transmit antenna at 1350'. The other was a remote base station with the single loop at about 850'. As we were an investigative agency, almost all of the mobiles were using AM/FM disguise antennas. (Yeah, I know, but we were stuck with the band that the State Division of Communications had dictated...) Despite the radiating dummy load antennas, we had excellent mobile coverage in virtually all of the state. A consideration for DB212 antennas is that lining them up on one leg can make them pretty directional. For towers that were very close to the coast, I would put all three elements on a single leg, but skew them so that only one was pointed directly off of the leg. This seemed to give me a somewhat cardioid pattern, but with a little better pattern to the back than if all three elements were in line. Another consideration is that they were designed to be used on Rohn 45/55/65 sized tower. If you put them all on one leg, a larger tower face doesn't matter much except that the rearward pattern will likely have a larger null. Mounting them on all three legs of a larger face tower will result in reduced gain and a pretty messed up pattern. I don't know if I'd worry a whole lot about adding a fourth element- the three element antenna will deliver excellent results. Doug K4AC (Running for ARRL Southeastern Division Director- please check out my website at www.k4ac.com)
Re: [Repeater-Builder] DB212-3
Given what you need to do, I'd probably use a single element. The mast needs to extend above and below the ends of the element, the further you can, the better. I'd probably use a 20' schedule 80 aluminum pipe and center the element on it. Chuck WB2EDV - Original Message - From: Tim tahr...@swtexas.net To: Repeater-Builder@yahoogroups.com Sent: Monday, August 30, 2010 2:51 PM Subject: Re: [Repeater-Builder] DB212-3 I'm glad somebody brought this up. I've got 2 of the DB212 antennas, without any phasing harness. The tower that the repeater is going up on is 90', wide spaced triangular tower (about 20' at the bottom 8' at the top). I'm just wondering if the work in building the harness, building the supports (the tower is not vertical, so I will have to 'make' a vertical support for them) is really worth the effort for an additional element. Seems I saw that with the 2 element configuration you only get about 2dB out of it. Doesn't seem like all the work is worth it. The reduced coverage off the back of the tower is not a concern. Just thought I'd throw this up into the wind. Thanks, Tim W5FN Yahoo! Groups Links No virus found in this incoming message. Checked by AVG - www.avg.com Version: 9.0.851 / Virus Database: 271.1.1/3102 - Release Date: 08/30/10 02:35:00
Re: [Repeater-Builder] DB212-3
Doug, what were the State Police using for mobile radios back when you were involved? I'm finding that the newer, wider front end, radios don't hear as well as the old 0.5-1 MHz wide receivers did. I can hit my 6-meter repeater full quieting, yet sometimes can hardly hear it due to mobile environment noise that you can't avoid driving past (computers, LAN equipment, etc., etc.) Chuck WB2EDV - Original Message - From: Doug Rehman To: Repeater-Builder@yahoogroups.com Sent: Monday, August 30, 2010 3:00 PM Subject: RE: [Repeater-Builder] DB212-3 Unfortunately it’s been so many years since I handled one that I’m pretty foggy on the phasing harness. The manual on Repeater Builder http://www.repeater-builder.com/db/pdfs/db-212-assembly-and-mounting-instructions-(andrew).pdf shows the feeds from all three elements coming together, but doesn’t give a hint as to the length or impedance of each leg. If the original harness was retained, he should be able to reverse engineer it or shorten it if it’s still in good shape. I’ve got a DB212-1 sitting beside the house now to use on our clubhouse tower for a 6m PropNet beacon antenna. Too many projects… Doug K4AC (Running for ARRL Southeastern Division Director- please check out my website at www.k4ac.com)
RE: [Repeater-Builder] DB212-3
When I first started, the existing radios were GE Mastr II’s. They actually had two receiver decks to cover the 800 KHz or so of our channel spread. When the system was finally phased out, we were using Motorola Maratracs with the handheld controllers. I had mine programmed with six meter channels as well; it was around 1 uV or so in the ham band as I recall. I was very impressed with the performance we got out of the Maratracs. With the exception of the repeater at 1400’ which was a Mastr III, all of the stations were Mastr II’s. Doug From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Chuck Kelsey Sent: Monday, August 30, 2010 3:08 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] DB212-3 Doug, what were the State Police using for mobile radios back when you were involved? I'm finding that the newer, wider front end, radios don't hear as well as the old 0.5-1 MHz wide receivers did. I can hit my 6-meter repeater full quieting, yet sometimes can hardly hear it due to mobile environment noise that you can't avoid driving past (computers, LAN equipment, etc., etc.) Chuck WB2EDV attachment: winmail.dat
RE: [Repeater-Builder] DB212-3
I'm doing this from memory - I have the docs at home and can verify later. The DB lowband dipoles are 50 ohm feed Z due to the close spacing to the tower leg. 1 dipole - fed directly with 50 ohm coax (VB-8) 2 dipoles - fed with equal legs of 50 ohm coax (VB-8) to a tee, match 25 ohms from tee to 50 ohm feedline with quarter-wave transformer (35 ohm VB-83) 3 dipoles - fed with equal legs of 50 ohm coax (VB-8) to two mated tees (two mated tees give you four ports - three to bays, one for input) yielding 17 ohms. First transform 17 ohms to 72 ohms via a quarter-wave of 35 ohm VB-83. Then transform 72 ohms to 50 ohms with a 'twelfth-wave' transformer (1/12 wave of 50 ohm cable then 1/12 wave of 72/75 ohm cable) to result in 50 ohms to feedline. 4 dipoles - same as 2 dipole case, but add another tee, two more equal-length 50 ohm cables from the added tee to the 35 ohm matching sections on the bay pairs described above, and another final 35 ohm Q section from the new tee to the feedline These dipoles couple a lot of energy to the tower - you'll likely need even more vertical isolation than what free-space curves might otherwise predict. --- Jeff WN3A -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Chuck Kelsey Sent: Monday, August 30, 2010 2:35 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] DB212-3 Doug - Do you know how the phasing harness was constructed for the three-element version? I don't, and that's why I suggested to Norm that he go with four - the phasing harness is easy. Or, he could use two elements for transmit and one for receive. I don't know how much isolation he'll need, but he might just get away without a duplexer if there's enough tower. Chuck WB2EDV - Original Message - From: Doug Rehman d...@k4ac.com mailto:doug%40k4ac.com To: Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com Sent: Monday, August 30, 2010 2:28 PM Subject: RE: [Repeater-Builder] DB212-3 In a previous life I managed the communications for a state police agency. We used 45 MHz for our main system and had forty some odd tower sites, almost all running DB212-3 antennas. Two of the sites were on 1000+ towers and used a single DB-212 element due to the large tower face and the great height. One was a repeater using a receive antenna at 1450' and a transmit antenna at 1350'. The other was a remote base station with the single loop at about 850'. As we were an investigative agency, almost all of the mobiles were using AM/FM disguise antennas. (Yeah, I know, but we were stuck with the band that the State Division of Communications had dictated...) Despite the radiating dummy load antennas, we had excellent mobile coverage in virtually all of the state. A consideration for DB212 antennas is that lining them up on one leg can make them pretty directional. For towers that were very close to the coast, I would put all three elements on a single leg, but skew them so that only one was pointed directly off of the leg. This seemed to give me a somewhat cardioid pattern, but with a little better pattern to the back than if all three elements were in line. Another consideration is that they were designed to be used on Rohn 45/55/65 sized tower. If you put them all on one leg, a larger tower face doesn't matter much except that the rearward pattern will likely have a larger null. Mounting them on all three legs of a larger face tower will result in reduced gain and a pretty messed up pattern. I don't know if I'd worry a whole lot about adding a fourth element- the three element antenna will deliver excellent results. Doug K4AC (Running for ARRL Southeastern Division Director- please check out my website at www.k4ac.com)
Re: [Repeater-Builder] DB212-3
On 8/30/2010 2:08 PM, Chuck Kelsey wrote: Doug, what were the State Police using for mobile radios back when you were involved? I'm finding that the newer, wider front end, radios don't hear as well as the old 0.5-1 MHz wide receivers did. I can hit my 6-meter repeater full quieting, yet sometimes can hardly hear it due to mobile environment noise that you can't avoid driving past (computers, LAN equipment, etc., etc.) Chuck WB2EDV I'll bet 99-44/100% of this is the lack of an effective noise blanker. I was running a LB SyntorX 9000 at the peak of the last cycle and it ran rings around everything else. It ran FULL band 10 and 6. Bench sensitivity of all the radios were pretty close, but the moto mobile noise blankers were a major ( 10 dB) advantage. I'll bet those 'old' radios have good noise blankers. -- mailto:o...@ozindfw.net Oz POB 93167 Southlake, TX 76092 (Near DFW Airport)
Re: [Repeater-Builder] DB212-3
The radio I'm using in the mobile is a GE Orion with a noise blanker. However, a noise blanker is designed to help with impulse-type noise. Microprocessor hash and similar noise sources are continuous, so I doubt a blanker is very effective. The problem, in my mind, is the huge increase in this type of noise compared to 20 or 30 years ago. Chuck WB2EDV - Original Message - From: Oz-in-DFW To: Repeater-Builder@yahoogroups.com Sent: Monday, August 30, 2010 5:00 PM Subject: Re: [Repeater-Builder] DB212-3 On 8/30/2010 2:08 PM, Chuck Kelsey wrote: Doug, what were the State Police using for mobile radios back when you were involved? I'm finding that the newer, wider front end, radios don't hear as well as the old 0.5-1 MHz wide receivers did. I can hit my 6-meter repeater full quieting, yet sometimes can hardly hear it due to mobile environment noise that you can't avoid driving past (computers, LAN equipment, etc., etc.) Chuck WB2EDV I'll bet 99-44/100% of this is the lack of an effective noise blanker. I was running a LB SyntorX 9000 at the peak of the last cycle and it ran rings around everything else. It ran FULL band 10 and 6. Bench sensitivity of all the radios were pretty close, but the moto mobile noise blankers were a major ( 10 dB) advantage. I'll bet those 'old' radios have good noise blankers. -- mailto:o...@ozindfw.net Oz POB 93167 Southlake, TX 76092 (Near DFW Airport)
Re: [Repeater-Builder] DB212-3
Noise blankers also target broadband noise. If some computer is dumping right on your intended receive frequency, you're out of luck. 73, Paul, AE4KR - Original Message - From: Chuck Kelsey To: Repeater-Builder@yahoogroups.com Sent: Monday, August 30, 2010 3:10 PM Subject: Re: [Repeater-Builder] DB212-3 The radio I'm using in the mobile is a GE Orion with a noise blanker. However, a noise blanker is designed to help with impulse-type noise. Microprocessor hash and similar noise sources are continuous, so I doubt a blanker is very effective. The problem, in my mind, is the huge increase in this type of noise compared to 20 or 30 years ago. Chuck WB2EDV - Original Message - From: Oz-in-DFW To: Repeater-Builder@yahoogroups.com Sent: Monday, August 30, 2010 5:00 PM Subject: Re: [Repeater-Builder] DB212-3 On 8/30/2010 2:08 PM, Chuck Kelsey wrote: Doug, what were the State Police using for mobile radios back when you were involved? I'm finding that the newer, wider front end, radios don't hear as well as the old 0.5-1 MHz wide receivers did. I can hit my 6-meter repeater full quieting, yet sometimes can hardly hear it due to mobile environment noise that you can't avoid driving past (computers, LAN equipment, etc., etc.) Chuck WB2EDV I'll bet 99-44/100% of this is the lack of an effective noise blanker. I was running a LB SyntorX 9000 at the peak of the last cycle and it ran rings around everything else. It ran FULL band 10 and 6. Bench sensitivity of all the radios were pretty close, but the moto mobile noise blankers were a major ( 10 dB) advantage. I'll bet those 'old' radios have good noise blankers. -- mailto:o...@ozindfw.net Oz POB 93167 Southlake, TX 76092 (Near DFW Airport)
Re: [Repeater-Builder] DB212-3
Plans are Chuck, to measure the harness and post results for group information and reference. While I really want 4 loops, I may end up settling for the set of 3. - Original Message - From: Repeater-Builder@yahoogroups.com Repeater-Builder@yahoogroups.com To: Repeater-Builder@yahoogroups.com Repeater-Builder@yahoogroups.com Sent: Mon Aug 30 13:35:16 2010 Subject: Re: [Repeater-Builder] DB212-3 Doug - Do you know how the phasing harness was constructed for the three-element version? I don't, and that's why I suggested to Norm that he go with four - the phasing harness is easy. Or, he could use two elements for transmit and one for receive. I don't know how much isolation he'll need, but he might just get away without a duplexer if there's enough tower. Chuck WB2EDV - Original Message - From: Doug Rehman d...@k4ac.com mailto:doug%40k4ac.com To: Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com Sent: Monday, August 30, 2010 2:28 PM Subject: RE: [Repeater-Builder] DB212-3 In a previous life I managed the communications for a state police agency. We used 45 MHz for our main system and had forty some odd tower sites, almost all running DB212-3 antennas. Two of the sites were on 1000+ towers and used a single DB-212 element due to the large tower face and the great height. One was a repeater using a receive antenna at 1450' and a transmit antenna at 1350'. The other was a remote base station with the single loop at about 850'. As we were an investigative agency, almost all of the mobiles were using AM/FM disguise antennas. (Yeah, I know, but we were stuck with the band that the State Division of Communications had dictated...) Despite the radiating dummy load antennas, we had excellent mobile coverage in virtually all of the state. A consideration for DB212 antennas is that lining them up on one leg can make them pretty directional. For towers that were very close to the coast, I would put all three elements on a single leg, but skew them so that only one was pointed directly off of the leg. This seemed to give me a somewhat cardioid pattern, but with a little better pattern to the back than if all three elements were in line. Another consideration is that they were designed to be used on Rohn 45/55/65 sized tower. If you put them all on one leg, a larger tower face doesn't matter much except that the rearward pattern will likely have a larger null. Mounting them on all three legs of a larger face tower will result in reduced gain and a pretty messed up pattern. I don't know if I'd worry a whole lot about adding a fourth element- the three element antenna will deliver excellent results. Doug K4AC (Running for ARRL Southeastern Division Director- please check out my website at www.k4ac.com)
Re: [Repeater-Builder] DB212-3
Most of this is true, but good noise blankers only operate on impulse noise. More to my point is that noise blankers were a big factor in my observation, therefore the dominant problem still appears to be impulse noise. In a similar vein, many of the newer, inexpensive small wide band Low VHF radios have foregone noise blankers entirely. There is no question that there has been a rise in the urban noise floor at all frequencies. Computers and networks are a major contributor. But like any other radio source, path loss is a reality and when operating mobile other vehicles have the proximity advantage. The fact also remains that even if you presume that FE bandwidth is a factor, it's only likely a 15 or so dB factor with respect to broadband noise - and that's only.Adjacent vehicles on the road have a lot more impact than that, probably starting at 30+ dB. Oz On 8/30/2010 4:36 PM, Paul Plack wrote: Noise blankers also target broadband noise. If some computer is dumping right on your intended receive frequency, you're out of luck. 73, Paul, AE4KR - Original Message - *From:* Chuck Kelsey mailto:wb2...@roadrunner.com *To:* Repeater-Builder@yahoogroups.com mailto:Repeater-Builder@yahoogroups.com *Sent:* Monday, August 30, 2010 3:10 PM *Subject:* Re: [Repeater-Builder] DB212-3 The radio I'm using in the mobile is a GE Orion with a noise blanker. However, a noise blanker is designed to help with impulse-type noise. Microprocessor hash and similar noise sources are continuous, so I doubt a blanker is very effective. The problem, in my mind, is the huge increase in this type of noise compared to 20 or 30 years ago. Chuck WB2EDV - Original Message - *From:* Oz-in-DFW mailto:li...@ozindfw.net *To:* Repeater-Builder@yahoogroups.com mailto:Repeater-Builder@yahoogroups.com *Sent:* Monday, August 30, 2010 5:00 PM *Subject:* Re: [Repeater-Builder] DB212-3 On 8/30/2010 2:08 PM, Chuck Kelsey wrote: Doug, what were the State Police using for mobile radios back when you were involved? I'm finding that the newer, wider front end, radios don't hear as well as the old 0.5-1 MHz wide receivers did. I can hit my 6-meter repeater full quieting, yet sometimes can hardly hear it due to mobile environment noise that you can't avoid driving past (computers, LAN equipment, etc., etc.) Chuck WB2EDV I'll bet 99-44/100% of this is the lack of an effective noise blanker. I was running a LB SyntorX 9000 at the peak of the last cycle and it ran rings around everything else. It ran FULL band 10 and 6. Bench sensitivity of all the radios were pretty close, but the moto mobile noise blankers were a major ( 10 dB) advantage. I'll bet those 'old' radios have good noise blankers. -- mailto:o...@ozindfw.net Oz POB 93167 Southlake, TX 76092 (Near DFW Airport) -- mailto:o...@ozindfw.net Oz POB 93167 Southlake, TX 76092 (Near DFW Airport)
