Re: [digitalradio] Re: How Can We Push HF Emcomm Messages to the Field?
Hi Rick, The numbers for the models seem very optimistic. Normal gain for J-pole (theoretical) can not be more than a dipole, since the antennas is an end fed dipole with the Q section for matching. This means at most 2.14 dBi, but maybe you are experiencing some ground gain which you can get on vertical too from my limited understanding? Yes, ground gain is mostly responsible for the higher gain figures. The J-pole in free space has a modeled gain of 2.34 dBi at 10.2 degrees, very close to the isotropic dipole value of 2.2 dBi, or 2.14 dBi. However, over real ground, 10 feet up, the gain increases to 5.17 dBi at 6.2 degrees. Flipping it horizontally, the gain increases to 7.81 dBi at 9.7 degrees, but for a better comparison, the gain horizontally is 6 dBi at 6 degrees and 10 feet. Mounted on a car at 5 feet, the takeoff angle increases to 19.1 degrees and the gain at 6 degrees is only 1.2 dBi horizontally. Rotated back to vertical at 5 feet, the gain is 4 dBi at 8 degrees, or 3 dBi at 6 degrees. In comparison, the square quad loop has 9.21 dBi of gain at 14 degrees, or 5.3 dBi at 6 degrees. So, in an apples-to-apples comparison, the single quad loop still excels the J-pole by 3 dB, which appears to be what we are finding, instead of the 6 dB difference previously noted, which did not normalize everything to a 6 degree takeoff angle. When the CSVHFS does annual parking lot type tests each year and they seem to come up with higher numbers than the theoretical. That may be why KU4AB's halo antenna exceeds the theoretical maximum by quite a bit. And the take off angle is very important as you note. There are companies that make claims of very high gain numbers but they are not toward the horizon, HI. I have a KU4AB square loop - in fact I started on 2m with a stacked pair. Comparing it to a dipole on my beacon, I find that the pattern has serious nulls, especially in the back (-6 dB!), and is just not omnidirectional. I tracked NK4Q across the center of South Carolina comparing the KU4AB loop to a single stretched quad loop (facing me) and there were many times that he could not even copy me on the KU4AB loop when copy was perfect on the stretched quad loop. A true halo works much better. The nice thing about quads is that they are easier to match than yagis often requiring only a direct connection to the driven element since the other elements reduce the impedance closer to 50 ohms and away from the 100+ ohms of a single loop. Although a bit bulky, with a three dimensional form factor, it is less likely you will poke out your eye. For portable use, my OptimizedQuad (two stretched rectangles in a diamond configuration) in a driven element/reflector arrangement, is probably a good compromise. It is only 20 x 20 x 13, so will fit in a trunk and does not have to be reassembled in the field - only put it up on a portable mast as high as is practical. If that gain (8.2 dBi at 6 degrees over real ground) is not enough for the distance or terrain, I also have a 4-element quad design with 14 dBi of gain (over read ground) at 6 degrees at 10 feet which can be unplugged and also fit in a trunk. The big 3 x 5/8 collinears may be able to reach just over 8 dBi, but it just is not enough for the longer reach. It is of course way better than a half wave J-pole. When you need over 12 dBi or more on one end, (vertical or horizontal), it is pretty hard to do better than a rotatable yagi. An important question to ask: If you need to operate on battery power, will you be able to rotate the base station antenna? Most would at least need AC generator power although an inverter used for short periods, might be possible. Good point! The 4-element quad beam with its 5 foot boom fills that bill nicely and is easy to set up! The beamwidth is a wide 60 degrees, so it can be just pointed by hand in the general direction of the EOC and does not need a rotator. In a true field situation, the antenna will probably never be out of reach, so it can be turned by the arnstrong method. Four of the recent Cebik triple dipole arrays look like one of the ways to get the most gain for a stationary antenna. I have asked some antenna companies if they are considering making such an antenna, but no response. Are you talking about his horizontal polling array paper? That was written because I asked him if he could find out what spacing I needed between 3-element quad antennas placed around a circle, but he did the article using moxon rectangles. In our area, we have some hams with rotating twist type Cushcraft 10 element V and H switchable beams, smaller beams, and some with double 13 element vertically stacked. Interestingly, these are hams who are also more into public service and don't normally get involved in weak signal work. It is a tough call to decide which way to polarize since hardly anyone is going to have H with any mobile setup and you need to have mobile
Re: [digitalradio] Re: How Can We Push HF Emcomm Messages to the Field?
Judy and I did further testing of 1/4 wave and 5/8 wave antennas for 2 meters on her vehicle using the ICOM IC-7000 at 50 watts out. The base station continued to be the 30 foot high homebrew J-pole and now has 100 watts out from the ICOM 746 Pro. The mobile antennas were only mag mounts, but then again, that is what most of us use. The furthest point out was 40 miles and we could still communicate on 2 meter SSB, but signals were quite weak. When she was mobile, there were locations that were so weak as to be unreadable at times. Some of those areas are difficult to even work the local FM repeater which is about 200 feet higher than our home QTH antenna and about 6 miles closer than our QTH! There were slight differences between the 5/8 wave and 1/4 wave. Sometimes the quarter wave would out perform the 5/8, but in general, the 5/8 did slightly better, especially farther out. Because of the convenience of the quarter wave (entering the garage), it is hard to beat, but I would like to try a half wave Larsen some time. If I had been using even my modest 4 element Arrow beam, signals would have been quite good at all times, based upon the nearly unity gain verticals. I still need to come up with even rudimentary horizontal dipoles at each end and see how well they compare. Now on the KU4AB squalo antennas, this is one of the only halo types that does not seem to have water ingress detuning issues. Even the M Squared products got low ratings on eham because of this problem. The KU4AB design is the one that got the good numbers on the Central States VHF Society test. They did not mention that there were any anomalies in the omnidirectional pattern, but your experience sounds unacceptable! According to the M Squared advertising on the 144HO loop, they claim as you do that only horizontal type antennas can give you the ground reflection gain. Their numbers and shape of the antenna look very much like the KU4AB. I wonder why so many are going with the squalo shape over what would seem to be a stronger shape when in a circle? Can you recommend any current manufacturer for circular halos? The other well known manufacturer has been SK for some time and no one was interested in taking over the business. Maybe build my own? A single halo may not be too bad, but I don't know if I can do a good job with phasing lines. And those gamma matches are a challenge. What are stretched quad loops? Can't seem to find anything on them. Or is that the optimized quad, but not intended for mobile operation, more for portable? The Cebik antenna was in March 2008 QST entitled, A New Spin on the Big Wheel. While the three dipole design could be homebrewed, a well made more wheel like design would be needed to operate mobile due to his HPOD triangle probably not handling vibration and wind as well. I like the easy matching approach taken. The article has some background information I have not seen elsewhere. He considers the gain to be about 7.2 dBi at 20 feet height, and with very accurate omni characteristics. The second design can be accessed by ARRL members and is a circle of dipoles rather than having them unconnected with any supports to stiffen up the antenna. Harder to build though. 73, Rick, KV9U kh6ty wrote: Hi Rick, The numbers for the models seem very optimistic. Normal gain for J-pole (theoretical) can not be more than a dipole, since the antennas is an end fed dipole with the Q section for matching. This means at most 2.14 dBi, but maybe you are experiencing some ground gain which you can get on vertical too from my limited understanding? Yes, ground gain is mostly responsible for the higher gain figures. The J-pole in free space has a modeled gain of 2.34 dBi at 10.2 degrees, very close to the isotropic dipole value of 2.2 dBi, or 2.14 dBi. However, over real ground, 10 feet up, the gain increases to 5.17 dBi at 6.2 degrees. Flipping it horizontally, the gain increases to 7.81 dBi at 9.7 degrees, but for a better comparison, the gain horizontally is 6 dBi at 6 degrees and 10 feet. Mounted on a car at 5 feet, the takeoff angle increases to 19.1 degrees and the gain at 6 degrees is only 1.2 dBi horizontally. Rotated back to vertical at 5 feet, the gain is 4 dBi at 8 degrees, or 3 dBi at 6 degrees. In comparison, the square quad loop has 9.21 dBi of gain at 14 degrees, or 5.3 dBi at 6 degrees. So, in an apples-to-apples comparison, the single quad loop still excels the J-pole by 3 dB, which appears to be what we are finding, instead of the 6 dB difference previously noted, which did not normalize everything to a 6 degree takeoff angle. When the CSVHFS does annual parking lot type tests each year and they seem to come up with higher numbers than the theoretical. That may be why KU4AB's halo antenna exceeds the theoretical maximum by quite a bit. And the take off angle is very important as you note. There are
Re: [digitalradio] Re: How Can We Push HF Emcomm Messages to the Field?
Skip, Realistically, the 5/8 wave will be maybe around the gain of a dipole. I would use 2 dBi, maybe 3 dBi at the most. I don't think there are any 5/8 wave verticals that can do much better than that and some antenna gurus point out that they can perform worse than half wave antennas. I have both quarter and 5/8 wave so I will try and do at least a local test. We must not loose sight of the fact that almost no hams have horizontal polarization and almost all have do have vertical polarization. And weak signal hams do not tend to focus on public service activities so you may not have any stations that you can work. I don't know of anyone who has any interest in my area. I would suggest that hams ask their weak signal operators whether or not they would be willing to participate in this. It takes a LOT of practice to make this work. You may not get it to work at the time you most need it. Since voice communication is not going to be used (too weak a signal) for many of these digital transfers, you would need to set up a specific frequency and offset. I have been monitoring and sending on 144.144 as suggested by others, but have never heard anything. But that is mostly on vertical polarization for now. The period transmission is very clever, something like Patrick, F6CTE's Multipsk programs sending of repeated characters. You could just have a macro set with the repeating character, and you probably do this. 73, Rick, KV9U kh6ty wrote: If the signals are in the marginal range, how do you do the coordinating between the stations? To date, we have been able to use a cell phone. How do you calculate the error rate (such as the 6% mentioned)? We send 50eroids.(..). Anything that is not a period is easily recognized as an error. Three on-perionds equates to a 6% error rate. If I understand this correctly, the test was between a 5/8 vertical to quad for vertical polarization vs. quad to quad for horizontal, wouldn't it be about right to see 6 dB difference considering that you are increasing the path budget with the inclusion of the quad? The test was a vertically polarized quad to a 5/8 wavelength whip, and a horizontally polarized quad to a horizontally polarized quad. The quad had 7.5 dBi of gain versus perhaps 5 dBi of gain for the vertical whip. That makes up about 2.5 dBi of the 6 dBi, and the rest is an approximation of the S/N as measured by flidit in both cases. As you can imagine, it is extremely difficult to make exact quantitative measurements under such conditions, but even modeling shows the 6 dB that Cebik references. Our experience is that the 6 dB is about correct. Several ways to do this is with quad to quad vertical and quad to quad horizontal polarization, or some other gain antenna that can switch properly between polarizations. I wonder if you would see such a difference? Based on two different modeling programs, and our own simple tests, I think so. The most significant finding is that we lose communicaton over about 30 miles using vertical-to-vertical, but easily over 70 miles using horizontal-to-horizontal, even though the horizontal antenna on the mobile end is 5 feet higher than the whip is. In the end, anectodal evidence from others also suggests a 15 to 20 mile range with vertical whips, and we already know we can exceed 70 miles in flat country using a low, horizontally-polarized quad instead of a vertical, and that is all that is important to our purpose. It would be nice to have more and better controlled tests, but you can just imagine the difficulty in arranging for such tests without doing it on an antenna range. You have to switch polarization on both ends, and one existing antenna may be on a tower, 50 feet in the air. Of course, any such tests are possible, but the difficulty of finding people to participate is difficult, at best. As far as we are concerned, together with the common knowledge that all weak signal communications on 2m use horizontal polarization, TV stations use horizontal polarization because long ago it was found to be better for propagation, and the confirming results from modeling, are sufficient enough reasons to insist on using horizontal polarization for distances longer than a repeater can provide. Add to that the probability that many existing vertical beams are not mounted on rotators, and the change to horizontal polarization appears to be well worth the effort, based on available information. You can also include the possibility that using a horizontally polarized quad provides a lower takeoff angle close to ground that a yagi, and you can see why there are many reasons to insist on using horizontal polarization. Finally, in a serious emcomm situation, NBEMS only needs to reach connectivity with the Internet for email delivery or POTS for phone delivery, so any
Re: [digitalradio] Re: How Can We Push HF Emcomm Messages to the Field?
Rick, Skip, Realistically, the 5/8 wave will be maybe around the gain of a dipole. I would use 2 dBi, maybe 3 dBi at the most. I don't think there are any 5/8 wave verticals that can do much better than that and some antenna gurus point out that they can perform worse than half wave antennas. I have both quarter and 5/8 wave so I will try and do at least a local test. Please do! We need as many field tests as possible. This morning I did some modeling studies over real ground with the following results: J-pole at 3m, 5.17 dBi at 6.2 degrees (vertical) J-pole at 3m, 7.7dBi at 9.8 degrees (horizontal) 3 section 5/8 wave collinear at 3m, 6.67 dBi at 9 degrees (vertical) Single vertically stretched quad loop at 3m, 9.65 dBi at 9 degrees (horizontal) Single vertically stretched quad loop at 3m, 6.28 dBi at 7.8 degrees (horizontal) Ground plane at 3m, 4.4 dBi at 46 degrees (vertical) Ground plane gain at 9 degrees, -0.2 dBi. A 3 section, 5/8 wave, collinear is 12 feet tall. A stretched quad loop is only 14 tall in comparison. Turnstiling two of these (like a stretched eggbeater antenna, reduces the gain by 3 dB, resulting in a horizontally-polarized antenna of 6.65 dBi gain, but with a 9 degree takeoff angle, and omnidirectional coverage for mobile use. Compare this to maybe 2.5 dBi for a single 5/8 wave whip (unknown takeoff angle, but somewhere between 46 degrees and 9 degrees). The big problem with any shortened vertical whip is that too much of the energy is radiated at a high angle. The takeoff angle probably accounts for a significant part of the 6 dB disadvantage of low vertical antennas that we have found during actual field tests. The three section 5/8 wave collinear gets its gain by compressing the high angle radiation, but it takes three 5/8 wave sections just to get the takeoff angle down to 9 degrees. The study with the J-pole rotated horizontally was only for comparison and it not a practical solution. The total antenna gain for us to reach 70 miles in flat country was 16 dBi. If an EOC is using a three-section collinear at 30 feet for omnidirectional coverage, and a mobile is using at best a 3 dBi antenna, the total available gain is only 6.7 + 3 dBi = 9.7 dBi, or a huge 6 dB short of the gain that we had but is omnidirectional. The higher gain horizontally-polarized setup is an EOC with four stacked Big Wheels, for about 9 dBi of gain and an eggbeater style, stretched loop, mobile antenna of 6.6 dBi of gain, for a total system antenna gain of 15.6 dBi, and still have a low takeoff angle. This puts the burden on the EOC to have a high, tall antenna, which may not always be practical, so the alternative is to make up the necessary gain on the portable end by using a higher gain quad that can be broken down to fit in the trunk of a car. I have developed three designs - a two element quad that is only 13 thick and does not have to be broken down, and 3 and 4 element quads that can be and reassembled on site. The 4-element quad has 12 dBi of gain if needed to reach an EOC. We must not loose sight of the fact that almost no hams have horizontal polarization and almost all have do have vertical polarization. This again begs the question as to how many have ROTATABLE vertically polarized GAIN antennas. Most I have talked to do not have a rotator. Instead they use multielement vertical collinears. Those that do use yagi's generally have them fixed in direction and pointed at a favorite repeater. None of these installations are going to get much range without a repeater and a way to rotate a yagi. And weak signal hams do not tend to focus on public service activities so you may not have any stations that you can work. I don't know of anyone who has any interest in my area. I would suggest that hams ask their weak signal operators whether or not they would be willing to participate in this. It takes a LOT of practice to make this work. You may not get it to work at the time you most need it. The good thing about the NBEMS concept is that in a pinch ANY ham receiving an emcomm CQ can forward the messages to any EOC with Internet connectivity, phone service or cell phone service. This intermediate station does not have to have emcomm training. He is simply a relay station to the EOC. Takes very little practice as the software is very simple. Since voice communication is not going to be used (too weak a signal) for many of these digital transfers, you would need to set up a specific frequency and offset. I have been monitoring and sending on 144.144 as suggested by others, but have never heard anything. But that is mostly on vertical polarization for now. With vertical polarization, you are 20 dB down from using horizontal polarization, so you will not hear anything. Anyway, currently, there is not much PSK31 activity on 144.144 and probably none in range of your station, even if you have a horizontally-polarized yagi. The
Re: [digitalradio] Re: How Can We Push HF Emcomm Messages to the Field?
Hi Skip, The numbers for the models seem very optimistic. Normal gain for J-pole (theoretical) can not be more than a dipole, since the antennas is an end fed dipole with the Q section for matching. This means at most 2.14 dBi, but maybe you are experiencing some ground gain which you can get on vertical too from my limited understanding? When the CSVHFS does annual parking lot type tests each year and they seem to come up with higher numbers than the theoretical. That may be why KU4AB's halo antenna exceeds the theoretical maximum by quite a bit. And the take off angle is very important as you note. There are companies that make claims of very high gain numbers but they are not toward the horizon, HI. The nice thing about quads is that they are easier to match than yagis often requiring only a direct connection to the driven element since the other elements reduce the impedance closer to 50 ohms and away from the 100+ ohms of a single loop. Although a bit bulky, with a three dimensional form factor, it is less likely you will poke out your eye. You might remember the portable 2 meter quad that QST published in the early 1980's. The big 3 x 5/8 collinears may be able to reach just over 8 dBi, but it just is not enough for the longer reach. It is of course way better than a half wave J-pole. When you need over 12 dBi or more on one end, (vertical or horizontal), it is pretty hard to do better than a rotatable yagi. An important question to ask: If you need to operate on battery power, will you be able to rotate the base station antenna? Most would at least need AC generator power although an inverter used for short periods, might be possible. Four of the recent Cebik triple dipole arrays look like one of the ways to get the most gain for a stationary antenna. I have asked some antenna companies if they are considering making such an antenna, but no response. In our area, we have some hams with rotating twist type Cushcraft 10 element V and H switchable beams, smaller beams, and some with double 13 element vertically stacked. Interestingly, these are hams who are also more into public service and don't normally get involved in weak signal work. It is a tough call to decide which way to polarize since hardly anyone is going to have H with any mobile setup and you need to have mobile to base communications. NBEMS, which I support wholeheartedly since it is the only cross platform open source digital software program of this type, is not really that easy to use compared with some other systems. You do have to practice this on a regular basis to get hams comfortable with how it works. And the weak signal NBEMS, where there is no phone communication possible, is going to need some very savvy ops who also know where the other station is located on the dial. The only 144.144 signals on 2 meters in my area likely originate from my station. I may be able to get some others to try. One of our local hams unfortunately decided to buy a Yaesu FT-450 instead of an 857D/897D so even though he is on digital with some OJT with the two of us getting together earlier this week, no go on 2 meters. We did OK on 10 meters though. 73 for now, Rick, KV9U kh6ty wrote: Rick, Skip, Realistically, the 5/8 wave will be maybe around the gain of a dipole. I would use 2 dBi, maybe 3 dBi at the most. I don't think there are any 5/8 wave verticals that can do much better than that and some antenna gurus point out that they can perform worse than half wave antennas. I have both quarter and 5/8 wave so I will try and do at least a local test. Please do! We need as many field tests as possible. This morning I did some modeling studies over real ground with the following results: J-pole at 3m, 5.17 dBi at 6.2 degrees (vertical) J-pole at 3m, 7.7dBi at 9.8 degrees (horizontal) 3 section 5/8 wave collinear at 3m, 6.67 dBi at 9 degrees (vertical) Single vertically stretched quad loop at 3m, 9.65 dBi at 9 degrees (horizontal) Single vertically stretched quad loop at 3m, 6.28 dBi at 7.8 degrees (horizontal) Ground plane at 3m, 4.4 dBi at 46 degrees (vertical) Ground plane gain at 9 degrees, -0.2 dBi. A 3 section, 5/8 wave, collinear is 12 feet tall. A stretched quad loop is only 14 tall in comparison. Turnstiling two of these (like a stretched eggbeater antenna, reduces the gain by 3 dB, resulting in a horizontally-polarized antenna of 6.65 dBi gain, but with a 9 degree takeoff angle, and omnidirectional coverage for mobile use. Compare this to maybe 2.5 dBi for a single 5/8 wave whip (unknown takeoff angle, but somewhere between 46 degrees and 9 degrees). The big problem with any shortened vertical whip is that too much of the energy is radiated at a high angle. The takeoff angle probably accounts for a significant part of the 6 dB disadvantage of low vertical antennas that we have found during actual field tests. The three
Re: [digitalradio] Re: How Can We Push HF Emcomm Messages to the Field?
Hi Rick, Have you found that DominoEX is the best overall digital mode for FM? I know that PSK modes can have doppler errors from aircraft, but otherwise seem pretty good for weak signal. Yes, definitely! DominoEx is a frequency shift keying mode, not a phase shift mode, but doppler problems are still sometimes a problem, but not nearly as much as on PSK31 or PSK63, so that is one reason why we now use DominoEx. Once the reflected signal arrives 180 degrees out of phase with the direct signal, it cancels out the direct signal for a while and there is no mode that is going to print under that condition. The wider, multitone modes have less problem because the data is redundant and spread over the width of the signal, but even they are no completely immune. However, on our twice-weekly net, since we switched to DominoEx, the number of multipath problems is considerably down, even on SSB. Initial tests suggest that MFSK16 might even be better on FM, since it is the most sensitive mode we currently have with almost enough speed for messaging. It is completely unusable on VHF SSB, though, because many transceivers in the field are not frequency-stable enough to stay tuned. On FM, the carrier frequency sweeps over the entire passband, so only the audio frequency stability is important. DominoEx is especially valuable for drifting signals on SSB, because it can tolerate mistuning of 50% of the signal width. The IC-746Pro and the FT-857D, if without an optional TCXO, just drift too much to be usable on SSB, but are OK on FM, even though the S/N of FM is worse than on SSB. Note that any multipath cancellations simply cause repeated blocks when using ARQ, so they only slow down the transfer while the reflected signal is moving across the direct signal. Last night on our net, we had positive confirmation of the better performance of SSB over FM. The error rate between two stations was running at 6% on SSB, but when we all switched to FM, there was zero copy. The fact that there were any errors at all on SSB indicated that the stations were fringe area to each other, so it was a good demonstration of the advantage of SSB over FM. One station was beaming toward me and the other was 45 degrees away from the beampath of that station. It was the same as if a station with a high gain yagi were pointed away from me and even if I pointed directly at him, he was not radiating enough energy in my direction for me to copy him. We have to make more tests, but I think the secret of the OptimizedQuad is that the pattern is bulbous instead of being pencil-shaped - more like an omnidirectional pattern, but with gain over a wide beamwidth. Stacking OptimizedQuads vertically would increase the gain by 2.5 dB and still retain the wide beamwidth. It sure is interesting stuff! Your point is well taken that many of the hams who participate in public service activities, may tend to be the younger ones who are Technician class and can mostly operate on 6 meters and up with their vertical antennas and FM only rigs. The number of hams with the multimode/multiband rigs is increasing, at least in our area. It is not easy to get them to try SSB, much less SSB digital though. I have found that the main problem is lack of VOX with the FM transceivers, which cost under $200 for a single band one, so you need to spend another $100 for a SignaLinkUSB interface in order to use macros to do the PTT switching. The FM Transceiver Interface solves that problem for only $10. I have built 10 of them which I will be giving out to the first few people who want to join the net but have only FM transceivers, but they also need to have an OptimizedQuad, or small yagi, horizontally polarized. The claim about the ground gain for horizontal antennas may be true but I have not seen this definitely tested. Have you done some comparisons with low 2 meter antennas, such a mobile to low base antenna with V and H and found H consistently better? I don't hold too much stock in software modeling and only would go with empirical data for that kind of test. I have done only one test so far, as it is difficult to arrange, since both stations have to switch polarization, but that first test did show a huge advantage using horizontal polarization. Range on FM between a 5/8 wavelength whip mounted on a Prius and my quad turned for vertical polarization was only 25-30 miles, depending on whether or not the mobile was clear of trees, but 70 miles was a piece of cake between the OptimizedQuad and my own quad turned for horizontal polarization. We could have gone even farther if we had time. Next opportunity, we hope to be able to keep going. I am now more than convinced that the difference is real. There was once a reference, which I cannot find, that found that a quad near a ground surface retains a low takeoff angle, but the takeoff angle of a yagi of the same gain increases to as much at 40 degrees off
[digitalradio] Re: How Can We Push HF Emcomm Messages to the Field?
Regarding horizontal antennas... they also have a big advantage in rejecting intermod due to being cross-polarized with most commercial services... --- In digitalradio@yahoogroups.com, Rick W [EMAIL PROTECTED] wrote: Skip, Have you found that DominoEX is the best overall digital mode for FM? I know that PSK modes can have doppler errors from aircraft, but otherwise seem pretty good for weak signal. Your point is well taken that many of the hams who participate in public service activities, may tend to be the younger ones who are Technician class and can mostly operate on 6 meters and up with their vertical antennas and FM only rigs. The number of hams with the multimode/multiband rigs is increasing, at least in our area. It is not easy to get them to try SSB, much less SSB digital though. The claim about the ground gain for horizontal antennas may be true but I have not seen this definitely tested. Have you done some comparisons with low 2 meter antennas, such a mobile to low base antenna with V and H and found H consistently better? I don't hold too much stock in software modeling and only would go with empirical data for that kind of test. We will probably bite the bullet eventually and put a rotor back up on the low tower and maybe go with a Gulf Alpha 11 element V and H antenna for some reasonable gain. Then we could do the test. The ham that was going to help us lost his QTH and will not be able to relocate his VHF antenna farm. Of course they are quite high so maybe there would not have been as much difference in such a case. One of the best known VHF ops in my Section says that after running many tests he has never found either polarization is any different. But he has high antennas so maybe that accounts for it. We hope at least soon do some digital mode comparisons on 2 meters, whether SSB or FM. 73, Rick, KV9U kh6ty wrote: Hi Rick, Thank you for your comments on Howard's and my posts. Of course, we prefer using SSB on VHF, because the range is longer. First tests indicate that DominoEX with SSB has at least a 3 dB advantage over using FM with DominoEx. We are arranging more tests to be sure. However, the fact that today, maybe half of the U.S. amateurs hold only a Technician license, and do not have access to full HF priviledges, together with the fact that many hams only have inexpensive FM-only transceivers (but only a relative few may have VHF or multimode 2m transceivers with SSB capability), we have decide to explore ways that more hams can participate in emcomm activities, which means finding out how to use FM-only transceivers without repeater assistance. Although you have previously pointed out that many hams already have vertical antennas, the fact remains that a vertical antenna close to the ground (2 wavelengths), has about 6 dB less gain than the same antenna horizontally polarized. At VHF, a 6 dB disadvantage is an enormous disadvantage, plus many of the directive antennas used for FM are fixed on a particular repeater, and cannot currently be rotated anyway. Just model a vertically-polarized antenna over real ground at 2 wavelengths and compare the gain to the same antenna rotated 90 degrees to horizontal polarization to see the difference. In order to confirm Cebik's assertion about the gain difference, I did the modeling myself and found that he is absolutely correct. No difference in free space, but a huge difference over real ground. So, putting it all together, we can get significantly more range by simply investing in a horizontally-polarized antenna, using the same FM transceiver that people already have, and, better yet, in an inexpensive TV antenna rotator so we can communicate in any direction. The optimized two- element quad that we used for the FM/DominoEx tests (7.5 dBi in free space) can be built for less than $15 in an hour with all parts from Lowes, plus a SO-239 connector, and turned with a $60 Philips TV antenna rotator from Walmart, because its wind loading and boom length (13) is so small. A picture of the little quad is here: http://home.comcast.net/~hteller/OptimizedQuad.jpg. It is only 20 x 20 x 13, so it will fit in the trunk of a car without having to be dismanteled. Construction uses schedule 40 PVC, fiberglass driveway markers for spreaders, and #14 insulated house wire, so it is very rugged. I wish that all existing equipment could be used intead, but without a gain antenna and horizontal polarization, range without repeater assistance appears to be just too limited. It would be useful to know how much range you can get in your hilly rural area by using FM, DominoEx, and horizontal antennas on 2m. 73, Skip KH6TY NBEMS Development Team
Re: [digitalradio] Re: How Can We Push HF Emcomm Messages to the Field?
Very good information, Skip, If the signals are in the marginal range, how do you do the coordinating between the stations? How do you calculate the error rate (such as the 6% mentioned)? If I understand this correctly, the test was between a 5/8 vertical to quad for vertical polarization vs. quad to quad for horizontal, wouldn't it be about right to see 6 dB difference considering that you are increasing the path budget with the inclusion of the quad? Several ways to do this is with quad to quad vertical and quad to quad horizontal polarization, or some other gain antenna that can switch properly between polarizations. I wonder if you would see such a difference? 73, Rick, KV9U kh6ty wrote: Hi Rick, Have you found that DominoEX is the best overall digital mode for FM? I know that PSK modes can have doppler errors from aircraft, but otherwise seem pretty good for weak signal. Yes, definitely! DominoEx is a frequency shift keying mode, not a phase shift mode, but doppler problems are still sometimes a problem, but not nearly as much as on PSK31 or PSK63, so that is one reason why we now use DominoEx. Once the reflected signal arrives 180 degrees out of phase with the direct signal, it cancels out the direct signal for a while and there is no mode that is going to print under that condition. The wider, multitone modes have less problem because the data is redundant and spread over the width of the signal, but even they are no completely immune. However, on our twice-weekly net, since we switched to DominoEx, the number of multipath problems is considerably down, even on SSB. Initial tests suggest that MFSK16 might even be better on FM, since it is the most sensitive mode we currently have with almost enough speed for messaging. It is completely unusable on VHF SSB, though, because many transceivers in the field are not frequency-stable enough to stay tuned. On FM, the carrier frequency sweeps over the entire passband, so only the audio frequency stability is important. DominoEx is especially valuable for drifting signals on SSB, because it can tolerate mistuning of 50% of the signal width. The IC-746Pro and the FT-857D, if without an optional TCXO, just drift too much to be usable on SSB, but are OK on FM, even though the S/N of FM is worse than on SSB. Note that any multipath cancellations simply cause repeated blocks when using ARQ, so they only slow down the transfer while the reflected signal is moving across the direct signal. Last night on our net, we had positive confirmation of the better performance of SSB over FM. The error rate between two stations was running at 6% on SSB, but when we all switched to FM, there was zero copy. The fact that there were any errors at all on SSB indicated that the stations were fringe area to each other, so it was a good demonstration of the advantage of SSB over FM. One station was beaming toward me and the other was 45 degrees away from the beampath of that station. It was the same as if a station with a high gain yagi were pointed away from me and even if I pointed directly at him, he was not radiating enough energy in my direction for me to copy him. We have to make more tests, but I think the secret of the OptimizedQuad is that the pattern is bulbous instead of being pencil-shaped - more like an omnidirectional pattern, but with gain over a wide beamwidth. Stacking OptimizedQuads vertically would increase the gain by 2.5 dB and still retain the wide beamwidth. It sure is interesting stuff! Your point is well taken that many of the hams who participate in public service activities, may tend to be the younger ones who are Technician class and can mostly operate on 6 meters and up with their vertical antennas and FM only rigs. The number of hams with the multimode/multiband rigs is increasing, at least in our area. It is not easy to get them to try SSB, much less SSB digital though. I have found that the main problem is lack of VOX with the FM transceivers, which cost under $200 for a single band one, so you need to spend another $100 for a SignaLinkUSB interface in order to use macros to do the PTT switching. The FM Transceiver Interface solves that problem for only $10. I have built 10 of them which I will be giving out to the first few people who want to join the net but have only FM transceivers, but they also need to have an OptimizedQuad, or small yagi, horizontally polarized. The claim about the ground gain for horizontal antennas may be true but I have not seen this definitely tested. Have you done some comparisons with low 2 meter antennas, such a mobile to low base antenna with V and H and found H consistently better? I don't hold too much stock in software modeling and only would go with empirical data for that kind of test. I have done only one test so far, as it is difficult to arrange, since both
Re: [digitalradio] Re: How Can We Push HF Emcomm Messages to the Field?
If the signals are in the marginal range, how do you do the coordinating between the stations? To date, we have been able to use a cell phone. How do you calculate the error rate (such as the 6% mentioned)? We send 50eroids.(..). Anything that is not a period is easily recognized as an error. Three on-perionds equates to a 6% error rate. If I understand this correctly, the test was between a 5/8 vertical to quad for vertical polarization vs. quad to quad for horizontal, wouldn't it be about right to see 6 dB difference considering that you are increasing the path budget with the inclusion of the quad? The test was a vertically polarized quad to a 5/8 wavelength whip, and a horizontally polarized quad to a horizontally polarized quad. The quad had 7.5 dBi of gain versus perhaps 5 dBi of gain for the vertical whip. That makes up about 2.5 dBi of the 6 dBi, and the rest is an approximation of the S/N as measured by flidit in both cases. As you can imagine, it is extremely difficult to make exact quantitative measurements under such conditions, but even modeling shows the 6 dB that Cebik references. Our experience is that the 6 dB is about correct. Several ways to do this is with quad to quad vertical and quad to quad horizontal polarization, or some other gain antenna that can switch properly between polarizations. I wonder if you would see such a difference? Based on two different modeling programs, and our own simple tests, I think so. The most significant finding is that we lose communicaton over about 30 miles using vertical-to-vertical, but easily over 70 miles using horizontal-to-horizontal, even though the horizontal antenna on the mobile end is 5 feet higher than the whip is. In the end, anectodal evidence from others also suggests a 15 to 20 mile range with vertical whips, and we already know we can exceed 70 miles in flat country using a low, horizontally-polarized quad instead of a vertical, and that is all that is important to our purpose. It would be nice to have more and better controlled tests, but you can just imagine the difficulty in arranging for such tests without doing it on an antenna range. You have to switch polarization on both ends, and one existing antenna may be on a tower, 50 feet in the air. Of course, any such tests are possible, but the difficulty of finding people to participate is difficult, at best. As far as we are concerned, together with the common knowledge that all weak signal communications on 2m use horizontal polarization, TV stations use horizontal polarization because long ago it was found to be better for propagation, and the confirming results from modeling, are sufficient enough reasons to insist on using horizontal polarization for distances longer than a repeater can provide. Add to that the probability that many existing vertical beams are not mounted on rotators, and the change to horizontal polarization appears to be well worth the effort, based on available information. You can also include the possibility that using a horizontally polarized quad provides a lower takeoff angle close to ground that a yagi, and you can see why there are many reasons to insist on using horizontal polarization. Finally, in a serious emcomm situation, NBEMS only needs to reach connectivity with the Internet for email delivery or POTS for phone delivery, so any available forwarding station will suit the purpose, whether a part of an organized emcomm effort or not. The need is only to get the message to the EOC or other recipient, and all existing weak signal 2m stations are using horizontal polarization. Our main interest is emcom messaging, and even a single dB of advantage may mean getting the traffic through or not, so we have use the best methods at our disposal, and the preponderance of evidence says that horizontal polarization has an advantage over vertical polarization. 73, Skip KH6TY NBEMS Development Team 73, Rick, KV9U kh6ty wrote: Hi Rick, Have you found that DominoEX is the best overall digital mode for FM? I know that PSK modes can have doppler errors from aircraft, but otherwise seem pretty good for weak signal. Yes, definitely! DominoEx is a frequency shift keying mode, not a phase shift mode, but doppler problems are still sometimes a problem, but not nearly as much as on PSK31 or PSK63, so that is one reason why we now use DominoEx. Once the reflected signal arrives 180 degrees out of phase with the direct signal, it cancels out the direct signal for a while and there is no mode that is going to print under that condition. The wider, multitone modes have less problem because the data is redundant and spread over the width of the signal, but even they are no completely immune. However, on our twice-weekly net, since we switched to DominoEx, the number of multipath problems is considerably down, even on SSB. Initial tests suggest
Re: [digitalradio] Re: How Can We Push HF Emcomm Messages to the Field?
50eroids should read 50 periods, and on periods should read non periods, fldigit should read fldigi. Sorry - must be the wine - just got back from a family dinner! Skip KH6TY - Original Message - From: kh6ty [EMAIL PROTECTED] To: digitalradio@yahoogroups.com Sent: Thursday, November 27, 2008 8:19 PM Subject: Re: [digitalradio] Re: How Can We Push HF Emcomm Messages to the Field? If the signals are in the marginal range, how do you do the coordinating between the stations? To date, we have been able to use a cell phone. How do you calculate the error rate (such as the 6% mentioned)? We send 50eroids.(..). Anything that is not a period is easily recognized as an error. Three on-perionds equates to a 6% error rate. If I understand this correctly, the test was between a 5/8 vertical to quad for vertical polarization vs. quad to quad for horizontal, wouldn't it be about right to see 6 dB difference considering that you are increasing the path budget with the inclusion of the quad? The test was a vertically polarized quad to a 5/8 wavelength whip, and a horizontally polarized quad to a horizontally polarized quad. The quad had 7.5 dBi of gain versus perhaps 5 dBi of gain for the vertical whip. That makes up about 2.5 dBi of the 6 dBi, and the rest is an approximation of the S/N as measured by flidit in both cases. As you can imagine, it is extremely difficult to make exact quantitative measurements under such conditions, but even modeling shows the 6 dB that Cebik references. Our experience is that the 6 dB is about correct. Several ways to do this is with quad to quad vertical and quad to quad horizontal polarization, or some other gain antenna that can switch properly between polarizations. I wonder if you would see such a difference? Based on two different modeling programs, and our own simple tests, I think so. The most significant finding is that we lose communicaton over about 30 miles using vertical-to-vertical, but easily over 70 miles using horizontal-to-horizontal, even though the horizontal antenna on the mobile end is 5 feet higher than the whip is. In the end, anectodal evidence from others also suggests a 15 to 20 mile range with vertical whips, and we already know we can exceed 70 miles in flat country using a low, horizontally-polarized quad instead of a vertical, and that is all that is important to our purpose. It would be nice to have more and better controlled tests, but you can just imagine the difficulty in arranging for such tests without doing it on an antenna range. You have to switch polarization on both ends, and one existing antenna may be on a tower, 50 feet in the air. Of course, any such tests are possible, but the difficulty of finding people to participate is difficult, at best. As far as we are concerned, together with the common knowledge that all weak signal communications on 2m use horizontal polarization, TV stations use horizontal polarization because long ago it was found to be better for propagation, and the confirming results from modeling, are sufficient enough reasons to insist on using horizontal polarization for distances longer than a repeater can provide. Add to that the probability that many existing vertical beams are not mounted on rotators, and the change to horizontal polarization appears to be well worth the effort, based on available information. You can also include the possibility that using a horizontally polarized quad provides a lower takeoff angle close to ground that a yagi, and you can see why there are many reasons to insist on using horizontal polarization. Finally, in a serious emcomm situation, NBEMS only needs to reach connectivity with the Internet for email delivery or POTS for phone delivery, so any available forwarding station will suit the purpose, whether a part of an organized emcomm effort or not. The need is only to get the message to the EOC or other recipient, and all existing weak signal 2m stations are using horizontal polarization. Our main interest is emcom messaging, and even a single dB of advantage may mean getting the traffic through or not, so we have use the best methods at our disposal, and the preponderance of evidence says that horizontal polarization has an advantage over vertical polarization. 73, Skip KH6TY NBEMS Development Team 73, Rick, KV9U kh6ty wrote: Hi Rick, Have you found that DominoEX is the best overall digital mode for FM? I know that PSK modes can have doppler errors from aircraft, but otherwise seem pretty good for weak signal. Yes, definitely! DominoEx is a frequency shift keying mode, not a phase shift mode, but doppler problems are still sometimes a problem, but not nearly as much as on PSK31 or PSK63, so that is one reason why we now use DominoEx. Once the reflected signal arrives 180 degrees out of phase
[digitalradio] Re: How Can We Push HF Emcomm Messages to the Field?
SKIP SKIP SKIP READ READ READ I, HOWARD, AM not not NOT NOT not THE PERSON WITH THE QUESTION NOR THE PROBLEM. GEEZ, I TRY TO ANSWER SOMEONE'S QUESTION, AND SUDDENLY IT BECOMES MY QUESTION AND MY PROBLEM. If you are going to address someone - address the individual who has the problem or question in the first place. Personally - I don't care. Personally, I am an emergency worker who will never ever be sent to help in an ARES/RACES HAM group, because my agency will need me here. If it snows 20 feet one day, I'll be disciplined if I do not get to work - lose all bonuses and raises for a year. Personally, I already own expensive HF equipment and consider VHF short range no matter what you do with it - compared to a few hundred miles one gets via HF with a NVIS antenna 10 feet above ground. Personally, I think VHF is nice for 10 to 20 miles - you can go further - nice for you. I'll keep it in mind if anyone gets a team of bulldozers and makes Maryland flat - I can't walk a block or two with reaching a hill. I am not the one who asked the question. I am not the one who asked the question. Don't try giving me advise when I am not the one who asked the question. The original poster who posed the question and who has the problem was considering HF as a solution. Watson, I think he's got it... maybe. Howard --- In digitalradio@yahoogroups.com, kh6ty [EMAIL PROTECTED] wrote: Howard, We already achieved successful, error-free, VHF communication (with no repeated blocks) using NBEMS software over a 70 mile path in flat country between two 50 watt FM transceivers, one with a 7.5 dBi antenna at 10 feet off the ground and the other with a 7.5 dBi antenna 25 feet off the ground. I have also developed a DOX interface for FM transceivers which have no VOX. A schematic is here: http://home.comcast.net/~hteller/Interface%20schematic.jpg We are now in the process of determining just how much farther we can go using FM. However, using SSB with DominoEX, we have already reached 100 miles consistently between a 9 dBi antenna and a 13 dBi antenna. We think that a 100 mile capability is sufficient to reach outside connectivity for email or phone delivery and confirmation. If so, then VHF can be used most of the time. By using 2m, if the S/N is sufficient, we can also use phone and data interchangably on the same frequency, which is not permitted on HF. When the terrain is too hilly for VHF, NBEMS also supports Hf using NVIS antennas with several modes specifically tailored to work under very high static conditions. However, it obviously easier to put up a small beam than it is to always find supports for a NVIS antenna for portable use. A picture of my 2m portable setup is here: http://home.comcast.net/~hteller/sideview.jpg. By using a two section mast, everything will fit in the trunk or in the back seat. NBEMS does not support push emcomm email, because there is no confirmation of delivery. Instead, there must just be an operator present at each end of the link. This also helps prevent transmitting on an already active frequency. As you correctly note, VHF FM transceivers cost only a couple of hundred dollars instead of a thousand for SSB-capable transceivers, however, it is absolutely necessary to use horizontally-polarized, gain, antennas to go farther than a repeater can go. The portable station antenna is usually going to be near the ground, and at 10 feet off the ground, there is a huge 6 dB penalty to using vertical polarization. We are now changing the emphasis of NBEMS from SSB to FM with DominoEX in order to make it possible for more people to use NBEMS and also take advantage of the low cost FM-only transceivers in the field. There appears to be a 3 dB or greater disadvantage to using FM over SSB, even with horizontally-polarized antennas, but that can be made up with increased antenna gain or power. Phone will not work on VHF over the same long distances as DominoEX or MFSK16 will work, because the noise level is often so high, the voice just cannot be understood or even heard at all. However, DominoEX and MFSK16 can still decode when the S/N is 10 or 12 dB UNDER the noise level, and that is how we get such long distance communication on 2m. 73, Skip KH6TY NBEMS Development Team - Original Message - From: Howard Z. [EMAIL PROTECTED] To: digitalradio@yahoogroups.com Sent: Tuesday, November 25, 2008 6:58 PM Subject: [digitalradio] Re: How Can We Push HF Emcomm Messages to the Field? Is the volunteer out of VHF range? If the base station has a 100 watt VHF radio like the 746pro - you might be able to still reach the volunteer, but he may not have enough power to get back to you. Or he may be out of VHF range. HF is the way to go - but both ends of the conversation need NVIS antennas. HF antennas tend to be large, and NVIS
Re: [digitalradio] Re: How Can We Push HF Emcomm Messages to the Field?
Hi Howard, If you respond to someone's response to a question, with asking questions of your own, then it might be reasonable for some to respond as Skip did. It seems reasonable to me considering you asked Is the volunteer out of VHF range? You also asked about setting up something in the bed of a truck and asked about setting up something on HF after arrival at the destination. All good questions. While your particular job situation does not seem relevant to this discussion, the use of VHF, especially SSB VHF does seem particularly relevant since it is the only other way to get increased distance of communication between a mobile and fixed/portable/mobile station if HF is not workable. The most expensive HF equipment may of of no value when you are trying to communicate between two points that do not have NVIS propagation. It can be frustrating, especially during high QRN as well as the skywave signal just going through the ionosphere and not reflecting back down. For those experienced with Section level nets that only use 75/80 meters, you know what I mean. Going higher in HF frequency doesn't work any better (actually shorter ground/direct wave), and that is why STANAG systems won't work for local communication. VHF simplex with FM and with minimal antennas are not going to go all that far as you point out. In fact, in our area, it is difficult enough for mobiles to repeaters. Sometimes 15 to 20 miles is the best you can do in shaded areas. With 2 meter SSB, we seem to be able to still get through when FM can not get through although signals can be very weak. That is using half wave base to quarter wave mobile antennas. With improved antennas, depending upon terrain, the distance is going to extend out to as much as 50 to 100 miles. This is important because you reduce QRN problems from lightning static and other noise (admittedly less likely though during a time when power has failed), and you rarely would need that much distance for Incident Command to the dispatched mobile. Bottom line is that HF may not be able to do it 24/7, but 2 meter SSB may be the best choice. With today's relatively low cost multimode/multiband rigs, the cost is around $700 or so for 50 watts on 2 meter SSB. As you point out, these rigs are more expensive than 2 meter FM, but tremendously more flexible and a very good value since you also get an HF rig too. 73, Rick, KV9U Moderator, HFDEC yahoogroup Howard Z. wrote: SKIP SKIP SKIP READ READ READ I, HOWARD, AM not not NOT NOT not THE PERSON WITH THE QUESTION NOR THE PROBLEM. GEEZ, I TRY TO ANSWER SOMEONE'S QUESTION, AND SUDDENLY IT BECOMES MY QUESTION AND MY PROBLEM. If you are going to address someone - address the individual who has the problem or question in the first place. Personally - I don't care. Personally, I am an emergency worker who will never ever be sent to help in an ARES/RACES HAM group, because my agency will need me here. If it snows 20 feet one day, I'll be disciplined if I do not get to work - lose all bonuses and raises for a year. Personally, I already own expensive HF equipment and consider VHF short range no matter what you do with it - compared to a few hundred miles one gets via HF with a NVIS antenna 10 feet above ground. Personally, I think VHF is nice for 10 to 20 miles - you can go further - nice for you. I'll keep it in mind if anyone gets a team of bulldozers and makes Maryland flat - I can't walk a block or two with reaching a hill. I am not the one who asked the question. I am not the one who asked the question. Don't try giving me advise when I am not the one who asked the question. The original poster who posed the question and who has the problem was considering HF as a solution. Watson, I think he's got it... maybe. Howard
Re: [digitalradio] Re: How Can We Push HF Emcomm Messages to the Field?
Howard, First of all, there is no need to shout! My old eyes are still fine for reading without your using caps! :-) This group is for the purpose of discussion about using digital modes in amateur radio, all opinions are welcome, and nothing should not be held against a person for posting a contrary opinion. Personally, I already own expensive HF equipment and consider VHF short range no matter what you do with it - compared to a few hundred miles one gets via HF with a NVIS antenna 10 feet above ground. Personally, I think VHF is nice for 10 to 20 miles - you can go further - nice for you. I'll keep it in mind if anyone gets a team of bulldozers and makes Maryland flat - I can't walk a block or two with reaching a hill. Your statement that VHF is nice for 10-20 miles, is what we find also (using phone, and a 5/8 wavelength vertical whip on a car), but I was only tryng to point out that if you use horizontal polarization and sensitive digital modes, you can go much, much, farther, and we have established that over flat country. Vertical polarization with omnidirectional antennas are perfect for mobile use, and that is why we have repeaters today, but the range is very limited, as you point out. However HF is also often not reliable, especially during the time of day that 40m fades out and 80m comes up, or later, when 80m fades also, even using NVIS antennas. We have made many months of NBEMS tests on HF to realize that. In contrast, when VHF can be used, propagation is always consistent up to about 100 miles away. We are continually looking for ways to provide the most dependable messaging system at any time of day or night, and using VHF is one of those ways. I also clearly stated, When the terrain is too hilly for VHF, NBEMS also supports Hf using NVIS antennas with several modes specifically tailored to work under very high static conditions. However HF is not the only way reliable communications can be achieved, at least in non-hilly country. I was not trying to give you any advice, or make someone elses problem yours, but only to address the opinions in your own post. It is not necessary to be sarcastic - if my post, opinions, or findings displease you, simply use your delete key! ;-) For everyone else, please take note that it is a significant finding that long-range communications using FM and DominoEx can more than triple the range of FM phone communications in flat country, but we still have to find out what ranges are possible in hilly country compred to phone communications. Perhaps someone will explain it better, but my guess that when all signals encounter an obstacle such as the curvature of the earth (line of sight?), they diffract and scatter, losing most of their original strength. However, sensitive digital modes can still recover information from the very weak scattered waves, and that is why we can still copy with digital modes when you cannot even tell that a phone signal is no longer present. Since VHF phone signals are limited in general by the encounter with the curvature of the earth, it just makes sense to see what can be done with those weak scattered waves, and that is what we are trying to find out. If anything in my previous post is useful to anyone, please feel free to use it. Even the digital interface for FM transceivers can be useful, as it can be built for $10, which is much less than the $100 SignaLink USB, which also has its own DOX. 73, Skip KH6TY NBEMS Development Team - Original Message - From: Howard Z. [EMAIL PROTECTED] To: digitalradio@yahoogroups.com Sent: Wednesday, November 26, 2008 1:42 PM Subject: [digitalradio] Re: How Can We Push HF Emcomm Messages to the Field? SKIP SKIP SKIP READ READ READ I, HOWARD, AM not not NOT NOT not THE PERSON WITH THE QUESTION NOR THE PROBLEM. GEEZ, I TRY TO ANSWER SOMEONE'S QUESTION, AND SUDDENLY IT BECOMES MY QUESTION AND MY PROBLEM. If you are going to address someone - address the individual who has the problem or question in the first place. Personally - I don't care. Personally, I am an emergency worker who will never ever be sent to help in an ARES/RACES HAM group, because my agency will need me here. If it snows 20 feet one day, I'll be disciplined if I do not get to work - lose all bonuses and raises for a year. Personally, I already own expensive HF equipment and consider VHF short range no matter what you do with it - compared to a few hundred miles one gets via HF with a NVIS antenna 10 feet above ground. Personally, I think VHF is nice for 10 to 20 miles - you can go further - nice for you. I'll keep it in mind if anyone gets a team of bulldozers and makes Maryland flat - I can't walk a block or two with reaching a hill. I am not the one who asked the question. I am not the one who asked the question. Don't try giving me advise when I am not the one who asked the question. The original poster who posed the question and who has the problem
Re: [digitalradio] Re: How Can We Push HF Emcomm Messages to the Field?
Hi Rick, Thank you for your comments on Howard's and my posts. Of course, we prefer using SSB on VHF, because the range is longer. First tests indicate that DominoEX with SSB has at least a 3 dB advantage over using FM with DominoEx. We are arranging more tests to be sure. However, the fact that today, maybe half of the U.S. amateurs hold only a Technician license, and do not have access to full HF priviledges, together with the fact that many hams only have inexpensive FM-only transceivers (but only a relative few may have VHF or multimode 2m transceivers with SSB capability), we have decide to explore ways that more hams can participate in emcomm activities, which means finding out how to use FM-only transceivers without repeater assistance. Although you have previously pointed out that many hams already have vertical antennas, the fact remains that a vertical antenna close to the ground (2 wavelengths), has about 6 dB less gain than the same antenna horizontally polarized. At VHF, a 6 dB disadvantage is an enormous disadvantage, plus many of the directive antennas used for FM are fixed on a particular repeater, and cannot currently be rotated anyway. Just model a vertically-polarized antenna over real ground at 2 wavelengths and compare the gain to the same antenna rotated 90 degrees to horizontal polarization to see the difference. In order to confirm Cebik's assertion about the gain difference, I did the modeling myself and found that he is absolutely correct. No difference in free space, but a huge difference over real ground. So, putting it all together, we can get significantly more range by simply investing in a horizontally-polarized antenna, using the same FM transceiver that people already have, and, better yet, in an inexpensive TV antenna rotator so we can communicate in any direction. The optimized two-element quad that we used for the FM/DominoEx tests (7.5 dBi in free space) can be built for less than $15 in an hour with all parts from Lowes, plus a SO-239 connector, and turned with a $60 Philips TV antenna rotator from Walmart, because its wind loading and boom length (13) is so small. A picture of the little quad is here: http://home.comcast.net/~hteller/OptimizedQuad.jpg. It is only 20 x 20 x 13, so it will fit in the trunk of a car without having to be dismanteled. Construction uses schedule 40 PVC, fiberglass driveway markers for spreaders, and #14 insulated house wire, so it is very rugged. I wish that all existing equipment could be used intead, but without a gain antenna and horizontal polarization, range without repeater assistance appears to be just too limited. It would be useful to know how much range you can get in your hilly rural area by using FM, DominoEx, and horizontal antennas on 2m. 73, Skip KH6TY NBEMS Development Team - Original Message - From: Rick W [EMAIL PROTECTED] To: digitalradio@yahoogroups.com Sent: Wednesday, November 26, 2008 3:38 PM Subject: Re: [digitalradio] Re: How Can We Push HF Emcomm Messages to the Field? Hi Howard, If you respond to someone's response to a question, with asking questions of your own, then it might be reasonable for some to respond as Skip did. It seems reasonable to me considering you asked Is the volunteer out of VHF range? You also asked about setting up something in the bed of a truck and asked about setting up something on HF after arrival at the destination. All good questions. While your particular job situation does not seem relevant to this discussion, the use of VHF, especially SSB VHF does seem particularly relevant since it is the only other way to get increased distance of communication between a mobile and fixed/portable/mobile station if HF is not workable. The most expensive HF equipment may of of no value when you are trying to communicate between two points that do not have NVIS propagation. It can be frustrating, especially during high QRN as well as the skywave signal just going through the ionosphere and not reflecting back down. For those experienced with Section level nets that only use 75/80 meters, you know what I mean. Going higher in HF frequency doesn't work any better (actually shorter ground/direct wave), and that is why STANAG systems won't work for local communication. VHF simplex with FM and with minimal antennas are not going to go all that far as you point out. In fact, in our area, it is difficult enough for mobiles to repeaters. Sometimes 15 to 20 miles is the best you can do in shaded areas. With 2 meter SSB, we seem to be able to still get through when FM can not get through although signals can be very weak. That is using half wave base to quarter wave mobile antennas. With improved antennas, depending upon terrain, the distance is going to extend out to as much as 50 to 100 miles. This is important because you reduce QRN problems from lightning static and other noise (admittedly less likely though
Re: [digitalradio] Re: How Can We Push HF Emcomm Messages to the Field?
In this county you can sum up the biggest problem in one word manpower. Within my zip code there is 3 hams living in town. One is up in the years and has not been on the air in years as well as to weak to do much. As far as the other 2, one is chief of police. The other is #2 in command on the fire department.
Re: [digitalradio] Re: How Can We Push HF Emcomm Messages to the Field?
One obvious choice for pushing messages to the field would be multicast ( on any band, depending on the range you are after, etc.. ) One transmitter pushes the data to an unlimited number of recipients, who all get it at the same time. No point-to-point system can compete with it, multicast is much, much faster for distributing the same data to many locations. Learn about multicast at these plasces: http://uspacket.org/smf/index.php?board=6.0;sort=subject http://uspacket.org/smf/index.php?topic=9 The second link is only for the truly curious - the article is long-winded! Pardon my typing, my vision is not good today and I'm a hunt 'n peck typist. 73 DE Charles Brabham, N5PVL - Original Message - From: John Becker, WØJAB To: digitalradio@yahoogroups.com Sent: Wednesday, November 26, 2008 4:41 PM Subject: Re: [digitalradio] Re: How Can We Push HF Emcomm Messages to the Field? In this county you can sum up the biggest problem in one word manpower. Within my zip code there is 3 hams living in town. One is up in the years and has not been on the air in years as well as to weak to do much. As far as the other 2, one is chief of police. The other is #2 in command on the fire department.
[digitalradio] Re: How Can We Push HF Emcomm Messages to the Field?
I deleted that posting soon after I made it. However, I suppose those who get emails still got it. My posting was not appropriate. I appologize. Howard
Re: [digitalradio] Re: How Can We Push HF Emcomm Messages to the Field?
No hard feelings, Howard! Your passion for the hobby is appreciated, and many of us have hit the Send key, wishing immediately afterward that we had not! Regardless, I thought many of your points were well made and bared repeating. 73, Skip KH6TY NBEMS Development Team - Original Message - From: Howard Z. [EMAIL PROTECTED] To: digitalradio@yahoogroups.com Sent: Wednesday, November 26, 2008 6:32 PM Subject: [digitalradio] Re: How Can We Push HF Emcomm Messages to the Field? I deleted that posting soon after I made it. However, I suppose those who get emails still got it. My posting was not appropriate. I appologize. Howard Internal Virus Database is out of date. Checked by AVG - http://www.avg.com Version: 8.0.138 / Virus Database: 270.9.2/1785 - Release Date: 11/13/2008 9:12 AM
[digitalradio] Re: How Can We Push HF Emcomm Messages to the Field?
I deleted the posting a few minutes after I made it. I realized it was inappropriate. I somehow felt I was being challenged to a debate, All I did was give someone my 2 cents, and dozens of others would also likely give their opinions. I don't know why, but I reacted badly to the post directed to me. I thought the identity of the original person with the problem who posted the question had been lost and I had been nominated in his place. But, I re-read my posting, and considered it inappropriate, and I deleted it hoping nobody would read it. Howard --- In digitalradio@yahoogroups.com, kh6ty [EMAIL PROTECTED] wrote: Howard, First of all, there is no need to shout! My old eyes are still fine for reading without your using caps! :-)
[digitalradio] Re: How Can We Push HF Emcomm Messages to the Field?
Yes indeed - I have found that nothing on HF is reliable 24/7. One can not reliably reach another country at will regardless of equipment. Local NVIS operation also has problems. In my MARS group before DST ended, conditions were pretty bad because we started before sunrise - and then everything was find after sunrise. Sometimes we change frequencies which can help, but few members have antennas for 2 Mhz, so there are limits to that approach. I used to use an inverted dipole 10 to 20 ft above ground. I found one member who always sounded great and could always hear me no matter what. Turns out he uses a one wavelength loop, and that is what I use now. I think just about everyone hears me fine - I get good reports, but I don't hear everyone well under those occassional bad conditions. I am using a 1:1 balun, and I read that a balun is unnecessary with a one wavelength loop antenna, so I'm going to try eliminating the balun next month to see if it makes a difference. MARS uses NVIS SSB HF from 2 Mhz to 30 Mhz as the primary emcomm mode. Voice, digital, and winlink. I do admit it does not work 24/7, but nothing on HF does. Since morse code is eliminated, it is relatively easy for people to upgrade to General licenses - but it does take some effort. If VHF can get the job done for your circumstances - it's cheaper, antennas are smaller, mobile use is easy, etc etc. Howard
RE: [digitalradio] Re: How Can We Push HF Emcomm Messages to the Field?
In this county you can sum up the biggest problem in one word manpower. Within my zip code there is 3 hams living in town. One is up in the years and has not been on the air in years as well as to weak to do much. As far as the other 2, one is chief of police. The other is #2 in command on the fire department. I passed the question to my ARES crew that is posted in the subject area as it is an important question and with great scenarios. We just went through the largest mass exercise in Ontario called Trillium Exercise here in Thunder Bay Ontario. ARES was not involved as much as they should have been but we did have a chance to pass traffic via radio during the time. Anyhow, we too are in an area where we have a large mass of land and few hams to fill it. I have many areas in my ARES district that are vacant, so again getting those messages there are going to be tough both ways if all power and communications are down. Consensus here has MT63 as the mode of choice in digital traffic and use of NVIS antennas. We use it for CFARS as well Anyway, I think it is a great question and some good answers have come out of it. Regards Fred VE3FAL -Original Message- From: digitalradio@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Charles Brabham Sent: Wednesday, November 26, 2008 6:22 PM To: digitalradio@yahoogroups.com Subject: Re: [digitalradio] Re: How Can We Push HF Emcomm Messages to the Field? One obvious choice for pushing messages to the field would be multicast ( on any band, depending on the range you are after, etc.. ) One transmitter pushes the data to an unlimited number of recipients, who all get it at the same time. No point-to-point system can compete with it, multicast is much, much faster for distributing the same data to many locations. Learn about multicast at these plasces: http://uspacket.org/smf/index.php?board=6.0;sort=subject http://uspacket.org/smf/index.php?topic=9 The second link is only for the truly curious - the article is long-winded! Pardon my typing, my vision is not good today and I'm a hunt 'n peck typist. 73 DE Charles Brabham, N5PVL - Original Message - From: John Becker, mailto:[EMAIL PROTECTED] WØJAB To: digitalradio@yahoogroups.com Sent: Wednesday, November 26, 2008 4:41 PM Subject: Re: [digitalradio] Re: How Can We Push HF Emcomm Messages to the Field? In this county you can sum up the biggest problem in one word manpower. Within my zip code there is 3 hams living in town. One is up in the years and has not been on the air in years as well as to weak to do much. As far as the other 2, one is chief of police. The other is #2 in command on the fire department.
Re: [digitalradio] Re: How Can We Push HF Emcomm Messages to the Field?
Skip, Have you found that DominoEX is the best overall digital mode for FM? I know that PSK modes can have doppler errors from aircraft, but otherwise seem pretty good for weak signal. Your point is well taken that many of the hams who participate in public service activities, may tend to be the younger ones who are Technician class and can mostly operate on 6 meters and up with their vertical antennas and FM only rigs. The number of hams with the multimode/multiband rigs is increasing, at least in our area. It is not easy to get them to try SSB, much less SSB digital though. The claim about the ground gain for horizontal antennas may be true but I have not seen this definitely tested. Have you done some comparisons with low 2 meter antennas, such a mobile to low base antenna with V and H and found H consistently better? I don't hold too much stock in software modeling and only would go with empirical data for that kind of test. We will probably bite the bullet eventually and put a rotor back up on the low tower and maybe go with a Gulf Alpha 11 element V and H antenna for some reasonable gain. Then we could do the test. The ham that was going to help us lost his QTH and will not be able to relocate his VHF antenna farm. Of course they are quite high so maybe there would not have been as much difference in such a case. One of the best known VHF ops in my Section says that after running many tests he has never found either polarization is any different. But he has high antennas so maybe that accounts for it. We hope at least soon do some digital mode comparisons on 2 meters, whether SSB or FM. 73, Rick, KV9U kh6ty wrote: Hi Rick, Thank you for your comments on Howard's and my posts. Of course, we prefer using SSB on VHF, because the range is longer. First tests indicate that DominoEX with SSB has at least a 3 dB advantage over using FM with DominoEx. We are arranging more tests to be sure. However, the fact that today, maybe half of the U.S. amateurs hold only a Technician license, and do not have access to full HF priviledges, together with the fact that many hams only have inexpensive FM-only transceivers (but only a relative few may have VHF or multimode 2m transceivers with SSB capability), we have decide to explore ways that more hams can participate in emcomm activities, which means finding out how to use FM-only transceivers without repeater assistance. Although you have previously pointed out that many hams already have vertical antennas, the fact remains that a vertical antenna close to the ground (2 wavelengths), has about 6 dB less gain than the same antenna horizontally polarized. At VHF, a 6 dB disadvantage is an enormous disadvantage, plus many of the directive antennas used for FM are fixed on a particular repeater, and cannot currently be rotated anyway. Just model a vertically-polarized antenna over real ground at 2 wavelengths and compare the gain to the same antenna rotated 90 degrees to horizontal polarization to see the difference. In order to confirm Cebik's assertion about the gain difference, I did the modeling myself and found that he is absolutely correct. No difference in free space, but a huge difference over real ground. So, putting it all together, we can get significantly more range by simply investing in a horizontally-polarized antenna, using the same FM transceiver that people already have, and, better yet, in an inexpensive TV antenna rotator so we can communicate in any direction. The optimized two-element quad that we used for the FM/DominoEx tests (7.5 dBi in free space) can be built for less than $15 in an hour with all parts from Lowes, plus a SO-239 connector, and turned with a $60 Philips TV antenna rotator from Walmart, because its wind loading and boom length (13) is so small. A picture of the little quad is here: http://home.comcast.net/~hteller/OptimizedQuad.jpg. It is only 20 x 20 x 13, so it will fit in the trunk of a car without having to be dismanteled. Construction uses schedule 40 PVC, fiberglass driveway markers for spreaders, and #14 insulated house wire, so it is very rugged. I wish that all existing equipment could be used intead, but without a gain antenna and horizontal polarization, range without repeater assistance appears to be just too limited. It would be useful to know how much range you can get in your hilly rural area by using FM, DominoEx, and horizontal antennas on 2m. 73, Skip KH6TY NBEMS Development Team
[digitalradio] Re: How Can We Push HF Emcomm Messages to the Field?
Is the volunteer out of VHF range? If the base station has a 100 watt VHF radio like the 746pro - you might be able to still reach the volunteer, but he may not have enough power to get back to you. Or he may be out of VHF range. HF is the way to go - but both ends of the conversation need NVIS antennas. HF antennas tend to be large, and NVIS needs to be horizontal. I'm not sure there exists an NVIS antenna for a car or truck. Maybe something horizontal can be setup in the bed of a pick up truck? In general HF antennas for vehicles do not perform very well - but they are better than nothing. There are portable NVIS HF antennas available that can be setup rather quickly. Perhaps this is something to be done when he arrives at his destination, and then call the base on HF? Also keep in mind that HF radios typically cost over a thousand dollars compared to maybe two hundred for a VHF radio. Howard N3ZH --- In digitalradio@yahoogroups.com, expeditionradio [EMAIL PROTECTED] wrote: The following questions are asked to the amateur radio Emcomm community... how can we work together on this? THE TYPICAL SCENARIO It is a dark and stormy night... You are an amateur radio operator, volunteering with a relief organization, for communication to set up shelters in a hurricane disaster. There has been no power in the area for 24 hours. There is no mobile phone service, and all the VHF/UHF repeaters and digipeaters in the area are out of range or out of service. It is 3AM. You are driving in your vehicle, half-way to your first shelter destination, making your way on back roads. The main highway is flooded. You use your chain saw to pass a downed tree. The road ahead looks worse. THE CALL The relief organization wants to call you now. They have new information since you left on your mission, and they now want to change your destination, to divert you to another shelter location not far from your route. They want you to give the workers at the other shelter a list of supplies that are on the way. They want you to check the shelter's status. They want to know where you are, and if you can possibly divert to the other shelter, so they won't need to send out yet another expedition to the other shelter. THE QUESTIONS How will the relief organization call you? How will they get the actual message to you? How will they know where to route the message to be sure it gets to you? How will they get urgent feedback from you? THE BACKGROUND In the past, Ham radio has generally been very good at a One Way Traffic situation. We can initiate messages. We can pull messages into the field using automatic email systems. It is easy to send messages initiated from the field. But, not as easy to call someone in the field, unless the operator in the field decides to actually initiate some sort of 2-way contact. CAN WE PUSH MESSAGES? What about pushing calls and messages to the field? What are the types of ham radio methods presently in place to call hams in the field when the ham in the field doesn't initiate the contact? What are the existing techniques, and how can these be improved? How is the ham in the field alerted to a call? Can we devise standard method(s) for routing Emcomm push messages to the field? Is ham radio HF viable for pushing messages? Can we make the call day or night, without prior notice? Bonnie VR2/KQ6XA P.S. In case you are wondering, the scenario above was taken from the Katrina Hurricane Disaster. .
RE: [digitalradio] Re: How Can We Push HF Emcomm Messages to the Field?
And further, this thought should be considered as VHF FM, or VHF SSB? In a base/mobile or mobile/mobile environment, SSB on VHF works over much greater distances. With voice communications, VHF SSB benefits from having flutter resulting in the desired signal amplitude going up and down, while the background noise level is held pretty constant, by the AGC in the receiver. FM is opposite in that regard - when the signal gets weak, the background noise level comes up, at least until the squelch closes. In my perception, I seem to be better able to fill in the gaps in syllables when the signal drops out, than when it's filled with noise. VHF SSB also has the benefit of probably not requiring the mobile station to have to take time to set up an antenna. If the mobile station is parked in a null, chances are that moving the vehicle a few inches will change a multipath situation enough to provide good copy. If there's benefit to be had by setting up a portable (v.s. mobile) antenna, putting a VHF omnidirectional stick up 10-20' is a pretty trivial task. While there can be benefit to be had by using horizontal antennas, unless you're into serious weak-signal work, it's not necessary to realize large gains in coverage, even using omni antennas on both ends, using SSB. Digital modes that are designed to work well in weak signal circumstances on HF SSB rigs will similarly work well on weal signal VHF SSB rigs, because the same linear-mode technology is involved. Probably the biggest caveat to that will be frequency accuracy and stability. Radios on a net will need to be well warmed up, or have high stability oscillators, if they are operating unattended, and expected to be able to be received by the sender. I've encouraged those that are working on upgrading our regional hospital network to use the IC-706's that they already have set up for HF pactor, to try VHF pactor using the SSB mode, as a way to gain from the more readily available spectrum, so they don't have to compete for access to the very few frequencies available on HF for digital operations. It'll be interesting to see how they do. 73, Bob, KD7NM -Original Message- From: digitalradio@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Howard Z. Sent: Tuesday, November 25, 2008 3:59 PM To: digitalradio@yahoogroups.com Subject: [digitalradio] Re: How Can We Push HF Emcomm Messages to the Field? Is the volunteer out of VHF range? If the base station has a 100 watt VHF radio like the 746pro - you might be able to still reach the volunteer, but he may not have enough power to get back to you. Or he may be out of VHF range. HF is the way to go - but both ends of the conversation need NVIS antennas. HF antennas tend to be large, and NVIS needs to be horizontal. I'm not sure there exists an NVIS antenna for a car or truck. Maybe something horizontal can be setup in the bed of a pick up truck? In general HF antennas for vehicles do not perform very well - but they are better than nothing. There are portable NVIS HF antennas available that can be setup rather quickly. Perhaps this is something to be done when he arrives at his destination, and then call the base on HF? Also keep in mind that HF radios typically cost over a thousand dollars compared to maybe two hundred for a VHF radio. Howard N3ZH --- In digitalradio@yahoogroups.com, expeditionradio [EMAIL PROTECTED] wrote: The following questions are asked to the amateur radio Emcomm community... how can we work together on this? THE TYPICAL SCENARIO It is a dark and stormy night... You are an amateur radio operator, volunteering with a relief organization, for communication to set up shelters in a hurricane disaster. There has been no power in the area for 24 hours. There is no mobile phone service, and all the VHF/UHF repeaters and digipeaters in the area are out of range or out of service. It is 3AM. You are driving in your vehicle, half-way to your first shelter destination, making your way on back roads. The main highway is flooded. You use your chain saw to pass a downed tree. The road ahead looks worse. THE CALL The relief organization wants to call you now. They have new information since you left on your mission, and they now want to change your destination, to divert you to another shelter location not far from your route. They want you to give the workers at the other shelter a list of supplies that are on the way. They want you to check the shelter's status. They want to know where you are, and if you can possibly divert to the other shelter, so they won't need to send out yet another expedition to the other shelter. THE QUESTIONS How will the relief organization call you? How will they get the actual message to you? How will they know where to route the message to be sure it gets to you? How will they get urgent feedback from you? THE BACKGROUND In the past, Ham radio has generally been very
Re: [digitalradio] Re: How Can We Push HF Emcomm Messages to the Field?
Howard, We already achieved successful, error-free, VHF communication (with no repeated blocks) using NBEMS software over a 70 mile path in flat country between two 50 watt FM transceivers, one with a 7.5 dBi antenna at 10 feet off the ground and the other with a 7.5 dBi antenna 25 feet off the ground. I have also developed a DOX interface for FM transceivers which have no VOX. A schematic is here: http://home.comcast.net/~hteller/Interface%20schematic.jpg We are now in the process of determining just how much farther we can go using FM. However, using SSB with DominoEX, we have already reached 100 miles consistently between a 9 dBi antenna and a 13 dBi antenna. We think that a 100 mile capability is sufficient to reach outside connectivity for email or phone delivery and confirmation. If so, then VHF can be used most of the time. By using 2m, if the S/N is sufficient, we can also use phone and data interchangably on the same frequency, which is not permitted on HF. When the terrain is too hilly for VHF, NBEMS also supports Hf using NVIS antennas with several modes specifically tailored to work under very high static conditions. However, it obviously easier to put up a small beam than it is to always find supports for a NVIS antenna for portable use. A picture of my 2m portable setup is here: http://home.comcast.net/~hteller/sideview.jpg. By using a two section mast, everything will fit in the trunk or in the back seat. NBEMS does not support push emcomm email, because there is no confirmation of delivery. Instead, there must just be an operator present at each end of the link. This also helps prevent transmitting on an already active frequency. As you correctly note, VHF FM transceivers cost only a couple of hundred dollars instead of a thousand for SSB-capable transceivers, however, it is absolutely necessary to use horizontally-polarized, gain, antennas to go farther than a repeater can go. The portable station antenna is usually going to be near the ground, and at 10 feet off the ground, there is a huge 6 dB penalty to using vertical polarization. We are now changing the emphasis of NBEMS from SSB to FM with DominoEX in order to make it possible for more people to use NBEMS and also take advantage of the low cost FM-only transceivers in the field. There appears to be a 3 dB or greater disadvantage to using FM over SSB, even with horizontally-polarized antennas, but that can be made up with increased antenna gain or power. Phone will not work on VHF over the same long distances as DominoEX or MFSK16 will work, because the noise level is often so high, the voice just cannot be understood or even heard at all. However, DominoEX and MFSK16 can still decode when the S/N is 10 or 12 dB UNDER the noise level, and that is how we get such long distance communication on 2m. 73, Skip KH6TY NBEMS Development Team - Original Message - From: Howard Z. [EMAIL PROTECTED] To: digitalradio@yahoogroups.com Sent: Tuesday, November 25, 2008 6:58 PM Subject: [digitalradio] Re: How Can We Push HF Emcomm Messages to the Field? Is the volunteer out of VHF range? If the base station has a 100 watt VHF radio like the 746pro - you might be able to still reach the volunteer, but he may not have enough power to get back to you. Or he may be out of VHF range. HF is the way to go - but both ends of the conversation need NVIS antennas. HF antennas tend to be large, and NVIS needs to be horizontal. I'm not sure there exists an NVIS antenna for a car or truck. Maybe something horizontal can be setup in the bed of a pick up truck? In general HF antennas for vehicles do not perform very well - but they are better than nothing. There are portable NVIS HF antennas available that can be setup rather quickly. Perhaps this is something to be done when he arrives at his destination, and then call the base on HF? Also keep in mind that HF radios typically cost over a thousand dollars compared to maybe two hundred for a VHF radio. Howard N3ZH
RE: [digitalradio] Re: How Can We Push HF Emcomm Messages to the Field?
FWIW, in the response to Gustav It was known that Region 4 Resources would be deploying into the area in support of the Southern Baptist Disaster Relief Organization. Days ahead, info was exchanged on formal net operations in that area to allow members from Region 4 to check propagation and effective communications into what was projected to be the effective area; region 6, which is a fairly big target area. Propagation, time of day and available frequencies were reviewed and a net plan was decided on to allow the best chance for reliable communications into the affected area for 24 hour operations to support the deployed members from region 4 as they traveled into the affected area, in-transit to their various support locations and to get them safely back home to region 4. NCS were lined up on 2 hour shifts, and a pool of 12 were scheduled to make sure each day was covered in every 2 hour slot with a minimum of operator fatigue. One member was appointed to gather status reports on the deployed teams and report up the chain of command Weather conditions were constantly given directly to the teams via voice to advise them what they were traveling into, as Gustav was leaving and they were traveling into the edges of the affected area. NVIS can be achieves with two 102 whips, one front and one back, joined in the center over the vehicle, but it is better to have a support team, trained and ready, to understand propagation, MUF, general band conditions and be in emergency net operation with as many members as possible making every attempt possible to shut and listen. The net can periodically be extended by NCS (Net Control Station) calling for only stations with Good Readable to Loud and Clear copy on NCS, and in turn having them make the same call to determine the relay path. An accurate region roster and some idea of geography helps NCS to determine effectives of net and who to use for relay from deployed team members, if NCS does not have directly copy. NCS always chooses an alternate NCS, the furthest distance possible with reliable copy. This allows them to work together and achieve the broadest working net, with just 2 members to start and direct the net. The net is closed at the end of the 2 hours, and a new net is established with each oncoming NCS, which allows maintenance of the most accurate net roster. One member is appointed to track weather conditions in the path of the deployed teams, as radio station coverage is minimal at best from local broadcast stations, Major media resources are monitored to keep abreast of the fuel and power situation along the route. Having plenty of fuel in the ground is no good if the station has no electricity to pump it out of the ground. An open fuel station may clog one lane of a 4 lane divided highway as vehicles line up for miles to exit and refuel. The deployed members need to be in the proper lane, before the traffic snarl happens. They also need to be in touch with federal resources in convoy to keep them abreast, as the federal response may not be as well organized. Cellular coverage is monitored. MCS and ANCS use Skype to coordinate the net via text chat. Deployed members use Echolink where cellular coverage allows use of their air card for wireless access to an ISP. Winlink is used via aircard telnet/internet connectivity to direct messages to a single or group address, giving a little privacy if they are the first to arrive to a delicate situation and wish not to be in the clear with their Sitrep.. SHARES stations are active in the net, or on standby for direct access to federal entities. Phone Patch operators are on hand, ready to provide first access into a developing situation that may involve hazmat, mass casualty, etc. While traveling, something like a TS-2000 in cross band mode could give all members of a amateur caravan access to the HF net, if each member had something useful to report; otherwise, VHF from car to car, and one vehicle contained the team leader from each deployment group to relay the Intel back into the net for distribution. OK, How am I doing so far? Point to ponder: Anyone who deploys without prior notice has a highly technical tactical designator assigned to them - fool David KD4NUE -Original Message- From: digitalradio@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Howard Z. Sent: Tuesday, November 25, 2008 6:59 PM To: digitalradio@yahoogroups.com Subject: [digitalradio] Re: How Can We Push HF Emcomm Messages to the Field? Is the volunteer out of VHF range? If the base station has a 100 watt VHF radio like the 746pro - you might be able to still reach the volunteer, but he may not have enough power to get back to you. Or he may be out of VHF range. HF is the way to go - but both ends of the conversation need NVIS antennas. HF antennas tend to be large, and NVIS needs to be horizontal. I'm not sure there exists an NVIS antenna
RE: [digitalradio] Re: How Can We Push HF Emcomm Messages to the Field?
Conditions just now are at night hostile to even NVIS. We sometimes eke out ground wave between MARS members here with vertical antennas below -- well below -- 3.5 MHz. Some nights I'd like something below 1.8! Nevertheless, my mobile setup, when I have it installed, covers 160-440. MARS frequencies too, of course. I dont rely on the mobile antenna, with a spool of telco CO wire cheap and handy. I have Elk 2/440 LPDA's and painters poles, too. Making a communication system work requires forethought as to HOW it can be done for the requirement of the time. Frequency coordination that doesn't allow for propagation can hobble even a California Kilowatt, assuming anyone had a big enough generator and a 6X6. -- and ravine comms on VHF is really not a good idea. Some prior planning and practice is needed. A club I used to belong to supported bicycle rides over some pretty poor VHF radio paths. It helped when we TESTED those paths. Sometimes a remote cross band mobile repeater was needed. Sometimes an FRS radio link (but the Feds can't legally use those) to the rest stop or aid station from a nearby hill. But we can't rely on such things appearing from thin air. Or helping when large amounts of message traffic must be passed. There has been some discussion involving communication to customer WiFi and Bluetooth.Where it has been tried it has apparently been well received and these are of course well suited for digital traffic. The holes in our planning are not yet all known, either. Cortland KA5S AAR5UT [Original Message] From: Howard Z. [EMAIL PROTECTED] To: digitalradio@yahoogroups.com Date: 11/25/2008 6:59:21 PM Subject: [digitalradio] Re: How Can We Push HF Emcomm Messages to the Field? Is the volunteer out of VHF range? If the base station has a 100 watt VHF radio like the 746pro - you might be able to still reach the volunteer, but he may not have enough power to get back to you. Or he may be out of VHF range. HF is the way to go - but both ends of the conversation need NVIS antennas. HF antennas tend to be large, and NVIS needs to be horizontal. I'm not sure there exists an NVIS antenna for a car or truck. Maybe something horizontal can be setup in the bed of a pick up truck? In general HF antennas for vehicles do not perform very well - but they are better than nothing. There are portable NVIS HF antennas available that can be setup
RE: [digitalradio] Re: How Can We Push HF Emcomm Messages to the Field?
The last time I got into something like this I was called (all be it direct reply) a fool. What works for you in the large city may not work for me in the rural area with hills all around. In the floods this spring I at times had the only HF mobile rig in the county.
RE: [digitalradio] Re: How Can We Push HF Emcomm Messages to the Field?
We get quite good results in the 45 to 50 mile range using VHF SSB (2M) and 5 watts with Olivia from fixed location to fixed location and low gain omni vertical antennas. From a mobile to a fixed location, I would estimate as good a signal on SSB as can be expected from the same mobile to a repeater input on FM; unless there is a tremendous height difference to offset the signal to noise gain of the SSB transmission. David KD4NUE -Original Message- From: digitalradio@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Bob Donnell Sent: Tuesday, November 25, 2008 7:47 PM To: digitalradio@yahoogroups.com Subject: RE: [digitalradio] Re: How Can We Push HF Emcomm Messages to the Field? And further, this thought should be considered as VHF FM, or VHF SSB? In a base/mobile or mobile/mobile environment, SSB on VHF works over much greater distances. With voice communications, VHF SSB benefits from having flutter resulting in the desired signal amplitude going up and down, while the background noise level is held pretty constant, by the AGC in the receiver. FM is opposite in that regard - when the signal gets weak, the background noise level comes up, at least until the squelch closes. In my perception, I seem to be better able to fill in the gaps in syllables when the signal drops out, than when it's filled with noise. VHF SSB also has the benefit of probably not requiring the mobile station to have to take time to set up an antenna. If the mobile station is parked in a null, chances are that moving the vehicle a few inches will change a multipath situation enough to provide good copy. If there's benefit to be had by setting up a portable (v.s. mobile) antenna, putting a VHF omnidirectional stick up 10-20' is a pretty trivial task. While there can be benefit to be had by using horizontal antennas, unless you're into serious weak-signal work, it's not necessary to realize large gains in coverage, even using omni antennas on both ends, using SSB. Digital modes that are designed to work well in weak signal circumstances on HF SSB rigs will similarly work well on weal signal VHF SSB rigs, because the same linear-mode technology is involved. Probably the biggest caveat to that will be frequency accuracy and stability. Radios on a net will need to be well warmed up, or have high stability oscillators, if they are operating unattended, and expected to be able to be received by the sender. I've encouraged those that are working on upgrading our regional hospital network to use the IC-706's that they already have set up for HF pactor, to try VHF pactor using the SSB mode, as a way to gain from the more readily available spectrum, so they don't have to compete for access to the very few frequencies available on HF for digital operations. It'll be interesting to see how they do. 73, Bob, KD7NM -Original Message- From: digitalradio@ mailto:digitalradio%40yahoogroups.com yahoogroups.com [mailto:digitalradio@ mailto:digitalradio%40yahoogroups.com yahoogroups.com] On Behalf Of Howard Z. Sent: Tuesday, November 25, 2008 3:59 PM To: digitalradio@ mailto:digitalradio%40yahoogroups.com yahoogroups.com Subject: [digitalradio] Re: How Can We Push HF Emcomm Messages to the Field? Is the volunteer out of VHF range? If the base station has a 100 watt VHF radio like the 746pro - you might be able to still reach the volunteer, but he may not have enough power to get back to you. Or he may be out of VHF range. HF is the way to go - but both ends of the conversation need NVIS antennas. HF antennas tend to be large, and NVIS needs to be horizontal. I'm not sure there exists an NVIS antenna for a car or truck. Maybe something horizontal can be setup in the bed of a pick up truck? In general HF antennas for vehicles do not perform very well - but they are better than nothing. There are portable NVIS HF antennas available that can be setup rather quickly. Perhaps this is something to be done when he arrives at his destination, and then call the base on HF? Also keep in mind that HF radios typically cost over a thousand dollars compared to maybe two hundred for a VHF radio. Howard N3ZH --- In digitalradio@ mailto:digitalradio%40yahoogroups.com yahoogroups.com, expeditionradio [EMAIL PROTECTED] wrote: The following questions are asked to the amateur radio Emcomm community... how can we work together on this? THE TYPICAL SCENARIO It is a dark and stormy night... You are an amateur radio operator, volunteering with a relief organization, for communication to set up shelters in a hurricane disaster. There has been no power in the area for 24 hours. There is no mobile phone service, and all the VHF/UHF repeaters and digipeaters in the area are out of range or out of service. It is 3AM. You are driving in your vehicle, half-way to your first shelter destination, making your way on back roads. The main highway is flooded. You use your chain saw to pass a downed tree. The road
Re: [digitalradio] Re: How Can We Push HF Emcomm Messages to the Field?
This is something that would likely be more at home at the HFDEC yahoogroup that discusses disaster and emergency communications but lets look at some of the practical aspects. Distance was not specified, but it would be rare to send someone out at night, under dangerous conditions, in unfamiliar territory, to handle communications at a shelter. It would be unusual to be out of range of the EOC unless a very rural area with difficult terrain (OK, maybe not too unlike my region, HI). After recent testing that my wife and I have been doing with 6 meters vs 2 meters with different modes, we have found that 2 meters works the best when there are any possible noise problems (less likely with power lines inoperative though), and using SSB is superior to FM when signals become weak. This can give you a significant coverage area, especially if the base station has some gain. We also use HF mobile since Judy has a Texas Bug Catcher that can be attached to the receiver hitch. While not optimum according to expert mobileers, this is the way we are willing to do HF. Contrary to some claims that bending the antenna over will improve signals, we have not found this to be true and it does not give you NVIS signals. Using an extended wire might be of help but we have yet to test that as it can not be used in motion. There are very large and expensive antennas that are claimed as operating NVIS, but not something that most of us would consider. And I have not seen any tests done to show how efficient or how vertical the radiation really is. When Judy came back from our daughter's home (200 miles) last week, as is our usual custom, we again performed a number of tests at different distances and as long as the FoF2 is above 4 MHz, things are often OK with daytime signals of S5 to S8 (almost no QRN) when she is at the maximum distance. As she gets closer, her signal often drops lower in strength since she is likely transmitting with lower angle radiation than we would like on 75 meters. Her signal got worse and worse and at 100 miles out things became unusable at times. Even when she was only 15 miles out, she was barely able to communicate. And then even at only 7 or 8 miles where she refueled and had to take off the quick release top whip on her last transmission she was extremely difficult copy. The FoF2 had dropped below 2 MHz by then. Some of you may have noticed that lately we have had barely 1 MHz FoF2 in the evening. I just checked and at about ~8 pm CST, almost the entire U.S. is at 2 MHz. This means that you may find HF to be of very limited value in the evening. Since higher frequencies are even worse at close distances, other than ground wave, (which is only a few miles), and since 160 is so difficult to use for mobile, I am convinced that there really needs to be more of a focus on VHF SSB. One other supporting point is that many new mobile transceivers now include VHF and UHF SSB. 73, Rick, KV9U Howard Z. wrote: Is the volunteer out of VHF range? If the base station has a 100 watt VHF radio like the 746pro - you might be able to still reach the volunteer, but he may not have enough power to get back to you. Or he may be out of VHF range. HF is the way to go - but both ends of the conversation need NVIS antennas. HF antennas tend to be large, and NVIS needs to be horizontal. I'm not sure there exists an NVIS antenna for a car or truck. Maybe something horizontal can be setup in the bed of a pick up truck? In general HF antennas for vehicles do not perform very well - but they are better than nothing. There are portable NVIS HF antennas available that can be setup rather quickly. Perhaps this is something to be done when he arrives at his destination, and then call the base on HF? Also keep in mind that HF radios typically cost over a thousand dollars compared to maybe two hundred for a VHF radio. Howard N3ZH --- In digitalradio@yahoogroups.com, expeditionradio [EMAIL PROTECTED] wrote: The following questions are asked to the amateur radio Emcomm community... how can we work together on this? THE TYPICAL SCENARIO It is a dark and stormy night... You are an amateur radio operator, volunteering with a relief organization, for communication to set up shelters in a hurricane disaster. There has been no power in the area for 24 hours. There is no mobile phone service, and all the VHF/UHF repeaters and digipeaters in the area are out of range or out of service. It is 3AM. You are driving in your vehicle, half-way to your first shelter destination, making your way on back roads. The main highway is flooded. You use your chain saw to pass a downed tree. The road ahead looks worse. THE CALL The relief organization wants to call you now. They have new information since you left on your mission, and they now want to change your destination, to divert you to another shelter
