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Is it worth it? Will I notice?
OK, after the thread on PL-259 losses, I figured
my system (ant gain - connector losses - coax loss) 150 mhz total net gain 1.006 DBi 450 mhz total net gain 2.797 DBi Antenna tip is 32'6" above ground My proposed system would replace the RG 58 coax pieces with a single section of Flexi 4XL and the antenna would be a Comet GP-9. The new figures a 150 mhz total net gain 7.919 DBi 450 mhz total net gain 10.553 DBi Antenna tip is 47'6" above ground 150 mhz = 6.913 db improvement 450 mhz = 7.756 db improvement Antenna tip 15 feet higher Cost - about $250 for the improvement. Now here's my question - will I notice the improvement enough? I've had several OM's tell me that on SSB, CW or HF I would but not on 2m/440 simplex and repeaters. Ken KG0WX |
Now here's my question - will I notice the improvement enough? I've had several OM's tell me that on SSB, CW or HF I would but not on 2m/440 simplex and repeaters. Well, a 6 dB boost would double your range, IF you aren't hitting the limits imposed by your radio horizon. VHF and UHF don't "bend" much, so once you go beyond your radio horizon, you're pretty much done, no matter how much signal you had. It will improve your signal into repeaters, where you were a little noisy before, you should be quiet. On simplex, you'll notice better signal once you get far enough away that you used to be no longer full quieting. In an FM receiver, there is a signal limiter, that caps the signal level, so if you were already "full quieting", then no amount of power increase would result in a better signal. If you are far enough away that you're not full quieting, then yes 6dB will be noticeable. -- KC6ETE Dave's Engineering Page, www.dvanhorn.org Microcontroller Consultant, specializing in Atmel AVR |
I have a couple of GP-9s and can tell you the gain figures are a bit
inflated and not referenced to anything. A dipole array with optimum spacing between dipoles is about the most gain for size that I have encountered in VHF/UHF antennas. For VHF, a four bay dipole array at 20ft in length has 6dBD gain omni and the GP-9 claims 8.5dB(?) from three 5/8 elements. On UHF, a 16 element dipole array has about 9.8dBD gain and the GP-9 claims 11.9dB(?) for eight 5/8 elements. Something looks fishy to me. Mike Ken Bessler wrote: OK, after the thread on PL-259 losses, I figured my system (ant gain - connector losses - coax loss) 150 mhz total net gain 1.006 DBi 450 mhz total net gain 2.797 DBi Antenna tip is 32'6" above ground My proposed system would replace the RG 58 coax pieces with a single section of Flexi 4XL and the antenna would be a Comet GP-9. The new figures a 150 mhz total net gain 7.919 DBi 450 mhz total net gain 10.553 DBi Antenna tip is 47'6" above ground 150 mhz = 6.913 db improvement 450 mhz = 7.756 db improvement Antenna tip 15 feet higher Cost - about $250 for the improvement. Now here's my question - will I notice the improvement enough? I've had several OM's tell me that on SSB, CW or HF I would but not on 2m/440 simplex and repeaters. Ken KG0WX |
"Ken Bessler" wrote in message news:lWKjd.75151$%x.68322@okepread04... OK, after the thread on PL-259 losses, I figured my system (ant gain - connector losses - coax loss) 150 mhz total net gain 1.006 DBi 450 mhz total net gain 2.797 DBi Antenna tip is 32'6" above ground My proposed system would replace the RG 58 coax pieces with a single section of Flexi 4XL and the antenna would be a Comet GP-9. The new figures a 150 mhz total net gain 7.919 DBi 450 mhz total net gain 10.553 DBi Antenna tip is 47'6" above ground 150 mhz = 6.913 db improvement 450 mhz = 7.756 db improvement Antenna tip 15 feet higher Cost - about $250 for the improvement. Now here's my question - will I notice the improvement enough? I've had several OM's tell me that on SSB, CW or HF I would but not on 2m/440 simplex and repeaters. Ken KG0WX The figures speak for themselves. If you are doing any VHF/UHF weak signal work, regardless of mode, it WILL be noticeable. Depending on the distance of the sending station or repeater, it can even be noticeable on FM. Dee D. Flint, N8UZE |
"Mike" wrote in message m... I have a couple of GP-9s and can tell you the gain figures are a bit inflated and not referenced to anything. A dipole array with optimum spacing between dipoles is about the most gain for size that I have encountered in VHF/UHF antennas. For VHF, a four bay dipole array at 20ft in length has 6dBD gain omni and the GP-9 claims 8.5dB(?) from three 5/8 elements. On UHF, a 16 element dipole array has about 9.8dBD gain and the GP-9 claims 11.9dB(?) for eight 5/8 elements. Something looks fishy to me. Mike Nothing can distpute your math - something's up. I've changed plans a bit, though - the Boeing ARC 2 meter repeater is only 4,000 feet away and I'm worried about intermod. So, instead of a high gain antenna at 20', I'm going to go with a moderate gain antenna 10' higher. The idea is to get good gain with a farther horizon rather than high gain with a closer horizon. Plus, it's cheaper, too! Instead of the GP-9 @ 20', I'm going to add a 10' mast and go with a GP-3. Installation sould be a lot easier, too. Now, though, my gain figures are 2.913 db improvement on VHF and 3.056 db improvement on UHF. I'm seriously starting to wonder if I should just leave well enough alone - the MFJ-1729 is performing well. I was talking to N0IDW on the 145.19 Winfield, KS machine (a distance of 32 miles) and I could hit the reverse button and hear him on the input. He, however, could not hear me on the input. Ken KG0WX |
On Mon, 8 Nov 2004 07:56:46 -0600, "Ken Bessler"
wrote: OK, after the thread on PL-259 losses, I figured my system (ant gain - connector losses - coax loss) 150 mhz total net gain 1.006 DBi 450 mhz total net gain 2.797 DBi Antenna tip is 32'6" above ground My proposed system would replace the RG 58 coax pieces with a single section of Flexi 4XL and the antenna would be a Comet GP-9. The new figures a 150 mhz total net gain 7.919 DBi 450 mhz total net gain 10.553 DBi Antenna tip is 47'6" above ground 150 mhz = 6.913 db improvement 450 mhz = 7.756 db improvement Antenna tip 15 feet higher Cost - about $250 for the improvement. Now here's my question - will I notice the improvement enough? I've had several OM's tell me that on SSB, CW or HF I would but not on 2m/440 simplex and repeaters. Everything is relative. As Dee said, if you do weak signal work you will notice it. If you figure investment Vs performance yours is ahead of mine http://www.rogerhalstead.com/ham_files/tower.htm in both dollars per watt and hours to install. Took me two years to install, but I do put it to use. OTOH I've thought of replacing the UHF/VHF arrays with a single Diamond dual band repeater antenna, EXCEPT for the lightening problem. That tower has been taking about 3 hits a year and I have one Diamond repeater antenna in the shop that looks like a well used exploding cigar. The top end is pretty frazzled and the matching network in the base is shorted. Inside it vaporized the top 4 or 5 inches of the end element. In my opinion the height is the important element, but I'd not worry about the extra gain of the antenna. OTOH you *might* receive some intermod, but you *probably* won't. (note weasel words) Roger Halstead (K8RI & ARRL life member) (N833R, S# CD-2 Worlds oldest Debonair) www.rogerhalstead.com Ken KG0WX |
150 mhz = 6.913 db improvement
450 mhz = 7.756 db improvement Antenna tip 15 feet higher Now here's my question - will I notice the improvement enough? I've had several OM's tell me that on SSB, CW or HF I would but not on 2m/440 simplex and repeaters. Ken KG0WX Well, Ken maybe your "OM's" didn't eat their Wheaties. A 6dB improvement means you have quadrupled your ERP over your existing system. You have also increased the distance to your radio horizon with the increse in antenna height. Why they would say you won't notice an improvement is beyond me. In plane language here are a few things just a 6dB improvement mean. You can reduce your radios Tx power by a factor of 4 and have the equivalent ERP, 6dB doubles your range Tx and Rx (within the limits of your stations LOS - line of sight). Stations that were noisy will now be full quieting, be it simplex or repeaters you work. In even simpler terms, "night and day". What are you waiting for? Regards, Hugh KF6HHS Retired, now life moves at my pace. please note spam filter |
I've changed plans a bit, though - the Boeing ARC 2 meter repeater is only 4,000 feet away and I'm worried about intermod. So, instead of a high gain antenna at 20', I'm going to go with a moderate gain antenna 10' higher. The idea is to get good gain with a farther horizon rather than high gain with a closer horizon. Plus, it's cheaper, too! Instead of the GP-9 @ 20', I'm going to add a 10' mast and go with a GP-3. Installation sould be a lot easier, too. Now, though, my gain figures are 2.913 db improvement on VHF and 3.056 db improvement on UHF. I'm seriously starting to wonder if I should just leave well enough alone - the MFJ-1729 is performing well. I was talking to N0IDW on the 145.19 Winfield, KS machine (a distance of 32 miles) and I could hit the reverse button and hear him on the input. He, however, could not hear me on the input. Ken KG0WX Don't change the antenna but go for height and a good grade of coax. It won't show up for about 50 feet or so of coax on 2 meters but if going to 100 feet of coax it will on 440. If your setup is doing what you want it to put the money to something else. I don't do too much with the repeaters and FM so I was just using some rg-59 (75 ohm coax) to a home made dipole about 20 feet up the tower. It does what I want it to on FM. Unless it was to add some tower I would not spend $ 250 for an FM antenna system just to work repeaters. |
Actually, there is quite a lot of fun to be had working FM simplex
and repeaters here when the band opens up. One minute you're rag chewing with the locals on 146.490 simplex & the next thing you know someone checks into the group from 3 states away! That's when it's time to switch over to the beam and the Elecraft. A few years ago I was living on a hill. With a 14 element yagi on a 35' mast, I could just hear the Tulsa 145.110 machine when the band started to open. Then it'd open up 100% and I'd talk to south Texas on 2m FM or 450 miles away on 446.000 simplex. Neat! Ken KG0WX That setup is a big differance than in your first posting. I mentioned I do not do much FM work on 2 meters . I do work weak signal on 2 meter and 432 mhz ssb. It is not too unusual to work long distances that way. Ham radio has many things that can be fun. I usually think of the repeaters and FM as local contacts. I have worked from North Carolina to Canada about twice on 2 meter FM. Using a good antenna and ssb it is common to work out to 200 to 300 miles. The band "opens" a lot more if you have the advantage of about 10 to 20 more db of ssb. |
Ralph Mowery wrote:
That setup is a big differance than in your first posting. I mentioned I do not do much FM work on 2 meters . I do work weak signal on 2 meter and 432 mhz ssb. It is not too unusual to work long distances that way. Ham radio has many things that can be fun. I usually think of the repeaters and FM as local contacts. I have worked from North Carolina to Canada about twice on 2 meter FM. Using a good antenna and ssb it is common to work out to 200 to 300 miles. The band "opens" a lot more if you have the advantage of about 10 to 20 more db of ssb. Good luck following the weak signal VHF/UHF track here. 10 meters is short for this bunch, except for very few. Less than half dozen appear to know what EME is. BTDT |
Well, a 6 dB boost would double your range, IF you aren't
hitting the limits imposed by your radio horizon. _____________ Clarification: the coverage AREA doubles for the above situation, but the "range," or distance from the transmit antenna to a given field strength value increases only by about 40%. Here are the numbers, using the FCC's F50,50 curves for UHF NTSC TV propagation. 50W ERP from 100 feet above average terrain: 60dBuV/m at 2.99 miles Coverage area within the 60dBuV/m contour = 28 sq miles 200W ERP from 100 feet above average terrain (a 6dB ERP increase from the above example): 66dBuV/m at 2.99 miles 60dBuV/m at 4.2 miles Coverage area within the 60dBuV/m contour = 55.4 sq miles The radio horizon for these examples is located about 14 miles from the antenna site (at a 0.15 degree depression angle). RF Visit http://rfry.org for FM transmission system papers. |
"KF6HHS" wrote:
I stand by my statement, " 6dB doubles your range... Anyone who has done path analysis knows that 6dB doubles the range. Check into it - you might learn. _____________ I've checked, thanks. The field strength values I posted are based on empirical data used by the FCC to determine coverage range, and protection ratios for FM & TV broadcast stations. The same physics applies to "hams" as to broadcasters. The free-space path loss formula over a reflection-free path gives different results. But, as the original post asks " Is it worth it? Will I notice?," the real-world values from the FCC curves will give more applicable answers. Verify my numbers and conclusions for yourself at http://www.fcc.gov/mb/audio/includes/curves.html . You might learn g. RF |
KF6HHS wrote:
"I stand by my statement: 6 dB doubles your range." The "Sommerfeld formula" is ancient and accepted. It says: Ground-wave field strength = (A) Eo / d Eo = field strength at the surface of the earth at a unit distance from the transmitting antenna, neglecting earth`s losses d = distance to the transmitting antenna A = factor taking into account ground losses If the earth is perfect, the above reduces to: volts/meter = Eo / d assuming the right scale factors. At twice the distance, the field strength over flat earth is halved. The resulting current is also halved. Thus, the power, their product, is quartered. That`s a 6dB change from doubling the distance. On the other hand, if you want to produce the same field strength at twice the distance, you must use 4X the power by the Sommerfeld formula. Best regards, Richard Harrison, KB5WZI |
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Richard Clark is correct. The FCC family of propagation curves shows
greater attenuation than results from signal spreading into an ever enlarging volume. However, these curves also include an inverse distance line which is the 6 dB per doubled distance line. Its drop, make that decline, only derives from the growth in volume the fixed amount of expanding signal fills as it propagates. Best regards, Richard Harrison, KB5WZI |
A long time ago, when there was not so much man-made noise, I found that in
the almost-flat-country at the extreme edges of coverage from a base station to a mobile station, the rate of decrease was roughly one db per statute mile. This was in the 160 MHz range. The mobile is so far away from the base that the received signal is "noisy." I am considering rural locations and a terrain without significant hills. On the average, +3db of power at the base provided another 3 miles of (poor quality) coverage. More often than not, coverage was limited by the transmitter power of the mobile and the noise level at the base! The question asked can start to be answered when one knows the value placed on increased coverage. 73 Mac N8TT -- J. Mc Laughlin; Michigan U.S.A. Home: |
On Sat, 13 Nov 2004 12:35:32 -0500, "J. Mc Laughlin"
wrote: A long time ago, when there was not so much man-made noise, I found that in the almost-flat-country at the extreme edges of coverage from a base station to a mobile station, the rate of decrease was roughly one db per statute mile. This was in the 160 MHz range. The mobile is so far away from the base that the received signal is "noisy." I am considering rural locations and a terrain without significant hills. On the average, +3db of power at the base provided another 3 miles of (poor quality) coverage. More often than not, coverage was limited by the transmitter power of the mobile and the noise level at the base! The question asked can start to be answered when one knows the value placed on increased coverage. I'll bet I can get good reliable converage to a 100 miles with a 5 watt HT and a rubber duck with todays receivers. 50 to 75 mile coverage to mobiles. It's worked on 52 simplex every time I've tried it. Fasten the belt clip to the strap above the arm rest with the rubber duck sticking straight up into the big window, Hook a boom mike and ear piece to the HT and put my ANR head set over it. Call CQ and darn near get a pile up. Ain't nothing like a good tall antenna. Roger Halstead (K8RI & ARRL life member) (N833R, S# CD-2 Worlds oldest Debonair) www.rogerhalstead.com 73 Mac N8TT |
"KF6HHS" wrote in message ... 150 mhz = 6.913 db improvement 450 mhz = 7.756 db improvement Antenna tip 15 feet higher Now here's my question - will I notice the improvement enough? I've had several OM's tell me that on SSB, CW or HF I would but not on 2m/440 simplex and repeaters. Ken KG0WX Well, Ken maybe your "OM's" didn't eat their Wheaties. A 6dB improvement means you have quadrupled your ERP over your existing system. You have also increased the distance to your radio horizon with the increse in antenna height. Why they would say you won't notice an improvement is beyond me. In plane language here are a few things just a 6dB improvement mean. You can reduce your radios Tx power by a factor of 4 and have the equivalent ERP, 6dB doubles your range Tx and Rx (within the limits of your stations LOS - line of sight). Stations that were noisy will now be full quieting, be it simplex or repeaters you work. In even simpler terms, "night and day". What are you waiting for? Regards, Hugh KF6HHS Retired, now life moves at my pace. please note spam filter Well, I did it. I changed plans at the last second, though, going for the Hustler CG-144 monobander with radial kit. Instead of paying $200 for the GP-9, I paid $27 and got almost as much gain. After figuring my old antenna's gain - coax - connectors, I figured the new coax (Flexi 4XL) and antenna. The new antenna is 5 feet higher and my system gained 3.940 db. My S-meter on my 2 meter rig is stingy, esp. around S8 where it has an almost logritmic scale action. Still, several repeaters went from S3 to S5 and several went from S7 to S9. One repeater remained S1 but it's noise factor went from 50% quieting to 70% quieting. Turns out it probably was a good decision - the Hustler has 5.2 dbi gain and the tip is at 42'. I'm just stating to get intermod at this level of performance (I live between a hospital & Boeing). I'm convinced if I had gone with the GP-9, I would have serious intermod problems (plus my wallet would be $170 lighter) plus raising it would have been MUCH harder. Thanks to all who offered advice on this topic - You guys rule! 73's de Ken KG0WX |
Well, I did it. I changed plans at the last second, though,
going for the Hustler CG-144 monobander with radial kit. Instead of paying $200 for the GP-9, I paid $27 and got almost as much gain. After figuring my old antenna's gain - coax - connectors, I figured the new coax (Flexi 4XL) and antenna. The new antenna is 5 feet higher and my system gained 3.940 db. My S-meter on my 2 meter rig is stingy, esp. around S8 where it has an almost logritmic scale action. Still, several repeaters went from S3 to S5 and several went from S7 to S9. One repeater remained S1 but it's noise factor went from 50% quieting to 70% quieting. Turns out it probably was a good decision - the Hustler has 5.2 dbi gain and the tip is at 42'. I'm just stating to get intermod at this level of performance (I live between a hospital & Boeing). I'm convinced if I had gone with the GP-9, I would have serious intermod problems (plus my wallet would be $170 lighter) plus raising it would have been MUCH harder. The worth it question seems to be that you spent $ 27 for a net gain to get one repeater to go from about 50% to 70 % quieting. The other repeaters were peobably full quieting so you would not gain anything on them even if you spent the full $ 200. Whe 'worth it " will come when you are making contacts that you did not make with what you already had. |
"Ralph Mowery" wrote in message nk.net... The worth it question seems to be that you spent $ 27 for a net gain to get one repeater to go from about 50% to 70 % quieting. The other repeaters were peobably full quieting so you would not gain anything on them even if you spent the full $ 200. Whe 'worth it " will come when you are making contacts that you did not make with what you already had. Well, N0IDW can hear me on simplex at 40 miles away now where he only heard silence before. The real performance factor will kick in during the next band opening. Also, a fringe repeater is now within range (60 miles away) and I can use it's signal to check for band openings. Ken KG0WX |
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