Suggestion for an HF starter rig
I am a newly licensed technician, study for the general exam. I plan to
purchase an HF rig soon and would appreciate suggestions on a good starter rig. I am budgeting $800 for a rig and antenna. I would be happy with a good used rig but I am not sure where to start looking for information. Thanks, Jim KI6ISQ |
Suggestion for an HF starter rig
Jim,
Congratulations on the new ticket! Well I would suggest that you look at some of the late 1970's and 80's vintage rigs to start. Much of this gear is very capable for basic station use (CW and SSB) and may even serve you well on some of the sound card based digital modes. I found a very nice Yaesu FT-101zd at an estate sale for $75 that covers 160-10 meters (sans 60 Meters) that only required some minor repairs that I could do myself. Attend your local radio club meetings and ask around, check E-bay and the local news papers for possible sources. Be patient and you should be able to get a very nice fully working rig for $300 or even less if you don't mind fixing it. On the antenna budget I wouldn't know what to say except that the a good antenna can make a modest rig great and a bad antenna can make even the best rig worthless. Buying expensive antennas usually isn't "you get what you pay for" in terms of performance either so be careful here. Generally speaking, the larger and longer the antenna is, the more performance it will have. If you have the space and are allowed to put up antennas outside, I would suggest you build some wire antennas to start. If you can put up a G5RV or some other multi- band antenna you might be able to have a lot of fun at a pretty low cost. I think you can buy prebuilt versions of this antenna for under $200 or build your own for somewhat less. By all means, spend the time and money necessary to get an antenna system that performs well, or no amount of money spent on the rig will help you. I'll warn you that with the sun spot cycle being at the low end, it will be a number of years before HF will be as active as it's been on the higher frequency bands for long haul communications. This means that you may want to concentrate on the 80-40 meter bands from an antenna perspective right now as the higher frequency bands may be limited to mostly local communications for the time being. (You don't have privileges as a Tech on 160 Meters if I recall correctly so we can forget that band for now.) Other items you may want to consider in your budgeted items include: 1. Ground rods and ground wiring to get the best RF station ground possible. 2. Antenna "tuner" (If one is not included in the rig you buy) 3. 12 V DC power supply (if your purchased rig is DC powered) 4. Coax and connectors (For making up jumpers and antennas) Most of this stuff can be liberated from hamfests and junk sales fairly cheaply, or purchased online from a number of places. -= bob =- On Sep 21, 2:50 pm, wrote: I am a newly licensed technician, study for the general exam. I plan to purchase an HF rig soon and would appreciate suggestions on a good starter rig. I am budgeting $800 for a rig and antenna. I would be happy with a good used rig but I am not sure where to start looking for information. Thanks, Jim KI6ISQ |
Suggestion for an HF starter rig
Hi Jim,
While most rigs these days are at least "pretty good", I would put out a shameless plug for a rig like the Kennwood TS-830. I had the chance to go over one of those old beauties recently, and found it a sweet radio indeed. It has tube finals, and a very nice receiver. It has the Kenwood sound to boot. Lots of knobs if you are a tweaker. These can be found in the 3-400 dollar range. Other radios I've had the chance to evaluate are the: IC-761. A high quality radio. It is a big one though. But I like large radios. IC-745. Second Generation synthesized Rig. Pretty good one. Smaller radio for the day. You could go mobile with this one. IC-756 Pro - A fair radio. The Pro II is better, but probably priced outside your range. I might suggest picking up a tuner such as one of the MFJ 300 watt ones. Then get ladder line, and throw a general purpose dipole in your trees. That for my money is the best starter antenna going, and can service you long after you're a newbie. Some do not like to have to tune the antenna, but I can say that It is possible to contest with such a setup. Finally, look around and be patient, better deals come to the patient. From 5.5 years ago...... My first setup was: IC-745 - $250.00 used MFJ 949 Tuner - $129.00 new Ladder line - $30.00 new Antenna wire - $12.00 for a 500 foot reel of #12 THNN There is $421 dollars and on the air. I don't remember the costs of the nylon rope and misc stuff like end insulaters, but it wasn't much extra. And of course, you won't find copper at that price, but you can expect to pay 60 or so for 100 feet of ladder line, and whatever outrageoous price for wire these days. - 73 de Mike KB3EIA - |
Suggestion for an HF starter rig
"Michael Coslo" wrote
I might suggest picking up a tuner such as one of the MFJ 300 watt ones. Then get ladder line, and throw a general purpose dipole in your trees. That for my money is the best starter antenna going, and can service you long after you're a newbie. Some do not like to have to tune the antenna, but I can say that It is possible to contest with such a setup. I think it's even more than a "starter" antenna -- it's great, loads on just about any frequency, and if decently in the clear will work quite well. When I move to a place with the room for a hundred footer up in the trees, it will be the only antenna I'd really ever need for HF. However, I think a ladder-line fed antenna needs a tuner (i.e., transmatch) that has a pretty beefy balun. I had the MFJ-948 that gave me lots of trouble using a 55' long dipole with ladder line. I learned how to make a bigger and better 4:1 toroid balun to replace the dinky one that came with it... then it worked really well. Right, Cecil? ;-) Howard N7SO |
Suggestion for an HF starter rig
Howard Lester wrote:
"Michael Coslo" wrote I might suggest picking up a tuner such as one of the MFJ 300 watt ones. Then get ladder line, and throw a general purpose dipole in your trees. That for my money is the best starter antenna going, and can service you long after you're a newbie. Some do not like to have to tune the antenna, but I can say that It is possible to contest with such a setup. I think it's even more than a "starter" antenna -- it's great, loads on just about any frequency, and if decently in the clear will work quite well. When I move to a place with the room for a hundred footer up in the trees, it will be the only antenna I'd really ever need for HF. However, I think a ladder-line fed antenna needs a tuner (i.e., transmatch) that has a pretty beefy balun. I had the MFJ-948 that gave me lots of trouble using a 55' long dipole with ladder line. I learned how to make a bigger and better 4:1 toroid balun to replace the dinky one that came with it... then it worked really well. Right, Cecil? ;-) I agree that a random length dipole fed with ladder line makes a great antenna. I've used one for years with a traditional tuner. My question: If I put a balun between the ladder line and the tuner, can I use one of the automatic tuners built into modern rigs? If this works, it provides the advantages of one simple antenna for multiple bands without the hassle of having to retune when changing bands/frequencies. 73, Steve KB9X |
Suggestion for an HF starter rig
"Steve Bonine" wrote I agree that a random length dipole fed with ladder line makes a great antenna. I've used one for years with a traditional tuner. My question: If I put a balun between the ladder line and the tuner, can I use one of the automatic tuners built into modern rigs? If this works, it provides the advantages of one simple antenna for multiple bands without the hassle of having to retune when changing bands/frequencies. Steve, if the auto tuner can handle very high SWR's.. then sure. ;-) Seriously, I don't think it'd work. I had one of those in-line baluns designed for the purpose of being able to run RG8 coax through the wall to the transmatch. The coax length was maybe 8 feet. My antenna was about 50' long, fed with 450 window line, and I used it on all bands from 10 - 40m. The balun was from RadioWorks and was rated at maybe, I forget.... 4KW? I was running 100 watts and that balun got HOT. After a while, it seemed that the balun broke down from the excessive heat and was no longer useable. (Can that really happen?) That should give you an idea about the auto tuner idea for this kind of setup. It's really not that hard to re-tune a transmatch. Find the right settings for each band [segment] and write down the numbers. There are typically just three transmatch knobs to re-set, and it can be done in five seconds. OK, maybe seven seconds. ;-) Howard N7SO |
Suggestion for an HF starter rig
I agree that a random length dipole fed with ladder line makes a great
antenna. I've used one for years with a traditional tuner. My question: If I put a balun between the ladder line and the tuner, can I use one of the automatic tuners built into modern rigs? If this works, it provides the advantages of one simple antenna for multiple bands without the hassle of having to retune when changing bands/frequencies. Depends a lot on the radio and on your individual installation. The ATUs built into a lot of modern rigs are of the "line flattener" persuasion. They're intended to be used with an antenna which isn't too awfully far from a resonant 50-ohm load. As a rule of thumb, I'd say that most of them can match a 3:1 load, some of them will cope with most loads of up to 5:1, and few of them can handle 10:1 loads at all well. For what it's worth, the ATU in my Kenwood TS-2000 won't even attempt to match anything above 10:1. It'll struggle with a lot of loads between 5:1 and 10:1, depending on whether they're low-Z, high-Z, and/or substantially reactive. I suspect that this ATU is probably fairly typical of modern rigs. External tuners often have a substantially wider matching range than an internal line-matcher, and probably have significantly lower losses when handling difficult loads. An unbalanced tuner plus a robust balun is probably going to work better than a rig's ATU plus a balun. The balun can be a problem in either case, with difficult (high-Z) loads - it's not easy to build a balun which has a high enough choking reactance to really balance out the line currents well if it has to work into, say, 5000 ohms or so. Link-coupled tuners seem to be a better technical choice for such difficult loads, although (as per your comment) they aren't the most convenient beasts in the world. If your doublet length and feedline length leave you with reasonably tolerable in-the-shack feedpoint impedances on the bands that you care about, then you might want to consider a sort of hybrid approach. Use a robust balun to connect to the feedline, and feed the unbalanced side of the balun to a (bandswitched) set of L networks. You'd want one L-network per band, selected to bring the impedance down to somewhere in the 3:1 SWR range (or so) in the band center. The output of the L networks would go to the transceiver. With this approach, the L networks would perform the "gross" tuning of the antenna feedpoint Z, and bring it down to the point at which the transceiver's internal ATU could do the rest of the matching across the full width of the band. Since the L networks wouldn't need to provide an exact match for a 1:1 SWR, selecting the component values and tuning the networks would be simplified. -- Dave Platt AE6EO Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads! |
Suggestion for an HF starter rig
"Steve Bonine" wrote in message
... I agree that a random length dipole fed with ladder line makes a great antenna. I've used one for years with a traditional tuner. My I would strongly suggest against a random length doublet. A non-resonant doublet will have impedances all over the place. At some freuencies it cannot be matched at all, at others the losses in the tuner make you wish you hadn't been able to tune it. The trick is keeping those nasty spots out of the ham bands. There are a number of G5RV type antennas that are doublets whose length has been chosen to keep those nasty spots out of the ham bands. Spend a few minutes looking up the right lengths for your doublet and avoid potentially a lot of grief. Random length, of course, is random. you COULD get lucky. Or not .... ... |
Suggestion for an HF starter rig
xpyttl wrote:
Random length, of course, is random. you COULD get lucky. Or not .... I guess I'm lucky. I've never had a problem matching a random-length dipole on any frequency I've tried. That does not imply, of course, that any random length can be successfully used on any arbitrary frequency. And of course, "random length" should have read "as long as possible, given the placement of the trees." Thanks to everyone who chimed in on using an external balum and an automatic tuner. My gut told me that the consensus ("it won't work") was correct, but it was nice to get some more factual backup for that. |
Suggestion for an HF starter rig
Steve Bonine posted on Wed, 26 Sep 2007 10:12:27 EDT
xpyttl wrote: Random length, of course, is random. you COULD get lucky. Or not .... I guess I'm lucky. I've never had a problem matching a random-length dipole on any frequency I've tried. That does not imply, of course, that any random length can be successfully used on any arbitrary frequency. And of course, "random length" should have read "as long as possible, given the placement of the trees." Thanks to everyone who chimed in on using an external balum and an automatic tuner. My gut told me that the consensus ("it won't work") was correct, but it was nice to get some more factual backup for that. Steve, the factual backup on antenna matching has abounded in texts, mostly the 'pro' kind, for years. It's been used for years to impedance-match all kinds of things within a radio box...as well as outside it. As to amateur equipment, the subject gets colored (and both glamorized and defamed) by the lack of comparisons to other matching equipment and the affinity that some have for certain brands from certain manufacturers. If you wish, I can send you a copy of the L-section matching math that I've previously sent to Mike Coslo in e-mail. It isn't "formal" but it is accurate, but it does involve simple algebra. The L- sections are used in most of the automatic antenna tuners because it is simple (and therefore low-cost) and adapts to the measure-and-change L- or C- component algorithms that fit into small microprocessor programs. The heart of all of them is the Bruene RF voltage and current detector that senses the phases of each at the load end. [or variations on that 1955-beginning detector] The micro then determines which parts of the L- or C-components are to be switched in or out to get close to the ideal in-phase E & I of RF for most power transfer. Now the designer-manufacturers don't make auto-tuners that will match ANYTHING...even though it CAN be done. To reduce manufacturing costs they limit the number of internal inductors and capacitors and THAT will reduce the ability to auto-match anything. They are trying to be competitive on price. The newer transceivers have SOME internal auto-tuning capability but they clearly state the limits of their equipment. Not all separate auto- tuners specify that. [I have both just as a backup] "Baluns" aren't all perfect, either. They are good but just not perfect. Some are better than others but it would take ALL of them and some good lab test equipment to do a good comparison. However, MOST work well enough for amateur radio purposes and do allow for balanced-to-unbalanced line conversion at HF. Now ANY impedance-matching tuner will let one load up just about anything. All that serves is to transfer the most RF power into a load. What is NOT known is WHERE all that RF is going. Unless some ham has a balloon-borne sensor and data transfer gizmo, NOBODY can know just where the pattern is going to be. Big trees WILL affect the pattern, especially changing it between dry and wet climate times and between different kinds of trees. So will structures and assorted conductive things (aluminum patio covers, small garden sheds, power, phone, and TV cables) all within the near-field (within five or so wavelengths). Even some houses which have had aluminum siding added on compared to similar houses with just wood or stucco or brick siding. One can take an example of the U.S. Army's little AN/PRC-104 backpack transceiver. It covers the whole of HF using a whip antenna. It has had an auto-tuner built-in since it went operational in 1986. A human bean is a poor counterpoise for any antenna with HF wavelengths and soldiers aren't all "built to spec" for that purpose. Further, the transceiver and whip must operate from unknown field environments, in trees or well away from them, in swampy soil or dry desert. The transceiver can't get any higher than the soldier carrying it. But, the little built- in antenna tuner assures him that the whip antenna is going to get as much RF power into/out-of it as possible. The rest of it is trying to keep the whip as vertical as possible while in-use. Now a PRC-104 won't win any DX awards or enable contacts with Antarctica or Yurp, but it is a case-in-point where an auto- tuner certainly helps maximize signals in a 1:10 frequency range with a practical-minimal fixed antenna, allowing for a highly-variaable counterpoise/ground-plane environment. The vertical whip will probably maximize its pattern between 10 and 40 degrees above horizontal, give-or-take. It works in practice (for the equivalent of QRP amateur-style). Works well enough, that is. The auto-tuner built-in certainly helps it. Everyone's residential location varies greatly and only a very few are "perfect" (as to the antenna analyzer programs). One can load up practically anything with a tuner but only the shape and arrangement of conductive elements is going to determine where most of the RF goes to (or comes from). No tuner can help that. 73, Len AF6AY |
Suggestion for an HF starter rig
"AF6AY" wrote Lots of good stuff snipped.... Now ANY impedance-matching tuner will let one load up just about anything. All that serves is to transfer the most RF power into a load. What is NOT known is WHERE all that RF is going. Unless some ham has a balloon-borne sensor and data transfer gizmo, NOBODY can know just where the pattern is going to be. Big trees WILL affect the pattern, especially changing it between dry and wet climate times and between different kinds of trees. So will structures and assorted conductive things (aluminum patio covers, small garden sheds, power, phone, and TV cables) all within the near-field (within five or so wavelengths). Even some houses which have had aluminum siding added on compared to similar houses with just wood or stucco or brick siding. Everyone's residential location varies greatly and only a very few are "perfect" (as to the antenna analyzer programs). One can load up practically anything with a tuner but only the shape and arrangement of conductive elements is going to determine where most of the RF goes to (or comes from). No tuner can help that. I had to leave the important stuff... sorry to make everyone scroll down.... Len, I'm confused as to just what you're specifically referring to. Do you mean a doublet fed with balanced line (300 or 450 ohm window line) to a transmatch in the shack is something you don't recommend? Or are you referring to this system fed with coax to an autotuner? It'd seem to me that, as long as the system (fed with window line to keep the serious losses down to negligible) is in the clear, the transmission line is 90 degrees to the doublet for the "required" distance... all should be fine and the radiation pattern should emanate properly from the antenna itself, not so much the transmission line. ? Howard N7SO |
Suggestion for an HF starter rig
I have an ICOM T-90A (it's my first radio). It's a good "klunker" handheld
radio for beginners. There's a lot you can learn with it; you can't break it unless you intentionally and deliberately try to. Some things are annoying, like the fact that the battery charge takes 14 hours, unless you have a special charger, and you can't transmit while the battery is charging, but all this is safety-oriented, apparently. -Mindraker wrote in message . .. I am a newly licensed technician, study for the general exam. I plan to purchase an HF rig soon and would appreciate suggestions on a good starter rig. I am budgeting $800 for a rig and antenna. I would be happy with a good used rig but I am not sure where to start looking for information. Thanks, Jim KI6ISQ |
Suggestion for an HF starter rig
On Sep 25, 11:03?pm, "xpyttl" wrote:
I would strongly suggest against a random length doublet. A non-resonant doublet will have impedances all over the place. That's true, but it's not a reason to reject the 'random length' doublet. Spend a few minutes looking up the right lengths for your doublet and avoid potentially a lot of grief. It's not just the doublet length that matters but also the length, impedance and loss of the transmission line. Antennas like the G5RV choose a combination of dipole and transmission line length that present reasonable impedances on several bands. A very useful tool is modeling software such as EZNEC or G4FGQ's DIPOLE3. They will give useful predictions of shack-end impedance, so you can judge if it's in matching range or not. So even if the antenna is 'random' length, you can have a good idea if it will match and how efficient it will be before you put it up. With regard to transmatches, also called antenna tuners, for balanced loads, the two typical amateur approaches are the unbalanced-tuner- followed-by-a-balun method, and the link-coupled method. The unbalanced-tuner-with-balun method assumes the balun does its job over a wide range of impedances, which isn't always a good assumption, while the link-coupled method can be complex to bandswitch. A third method, described by AG6K, consists of a balun followed by an L network - the balun is on the rig side of the transmatch rather than the antenna side. Thus the balun only has to deal with 50 ohms nonreactive once the L network is adjusted. Google AG6K to see a description of his method. Although his tuner uses ganged roller coils, fixed coils with taps could be used in a homebrew version for simplicity and lower cost. Random length, of course, is random. you COULD get lucky. Or not .... Modeling software can be a big help in removing the randomness. 73 es GL de Jim, N2EY |
Suggestion for an HF starter rig
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Suggestion for an HF starter rig
On Sep 26, 3:46?pm, "Howard Lester" wrote:
"AF6AY" wrote Lots of good stuff snipped.... Now ANY impedance-matching tuner will let one load up just about anything. All that serves is to transfer the most RF power into a load. What is NOT known is WHERE all that RF is going. Unless some ham has a balloon-borne sensor and data transfer gizmo, NOBODY can know just where the pattern is going to be. Big trees WILL affect the pattern, especially changing it between dry and wet climate times and between different kinds of trees. So will structures and assorted conductive things (aluminum patio covers, small garden sheds, power, phone, and TV cables) all within the near-field (within five or so wavelengths). Even some houses which have had aluminum siding added on compared to similar houses with just wood or stucco or brick siding. Everyone's residential location varies greatly and only a very few are "perfect" (as to the antenna analyzer programs). One can load up practically anything with a tuner but only the shape and arrangement of conductive elements is going to determine where most of the RF goes to (or comes from). No tuner can help that. I had to leave the important stuff... sorry to make everyone scroll down.... Len, I'm confused as to just what you're specifically referring to. Do you mean a doublet fed with balanced line (300 or 450 ohm window line) to a transmatch in the shack is something you don't recommend? Or are you referring to this system fed with coax to an autotuner? It'd seem to me that, as long as the system (fed with window line to keep the serious losses down to negligible) is in the clear, the transmission line is 90 degrees to the doublet for the "required" distance... all should be fine and the radiation pattern should emanate properly from the antenna itself, not so much the transmission line. ? I'm trying to point out that any good tuner can "load up" to ANYTHING...i.e., transfer RF power out of the transmitter and into whatever the "load" is. If the "load" is just a transmission line, a very lonnnnng one, the tuner will "load up" on that. If the "load" is your favorite antenna type, it will "load up" on that. Once the RF power has been transferred into this load, then it is up to the conductors in the "load" to radiate it into whichever direction you expect it will go. But, do NOT expect ANY antenna to behave properly (for radiation) if its near field is impugned by nearby dielectric material or conductors. Mostly I was making a comment on "loading up" phrases which I consider an incomplete description of what is really happening. A tuner, any tuner, will do the job of transferring RF into the "load." That isn't the whole story. Next is what the "load" does with it to create the EM wavefront. No tuner can help that. If you are satisfied with your particular method of getting RF out of the transmitter and into some antenna, fine. Satisfaction is all part of the game. Such satisfaction is not the example to set for all. It seems to me that every- one's location is different and each presents a unique problem to solve for the more-optimum EM wavefront launch direction in that location. Anyone who says that one kind of antenna is the "best" or one should "always" use a certain kind of balanced transmission line isn't looking at the whole picture. They are probably describing just the only (or a few) antenna installations they used. Yes, some antennas "work better" than others. In a particular location. For someone just starting out, I would suggest just a vertical for HF. It is the least obtrusive to neighbors (can be described as a "flagpole") and most will perform adequately (to launch an EM wavefront) with a few radials for the "ground." No, it won't win awards or work DX "better" than Brand Y using Brand T transmission line, but it WILL radiate adquately...and that's the whole name of the game, ain't it? :-) 73, Len AF6AY |
Suggestion for an HF starter rig
On Sep 27, 10:53?am, Michael Coslo wrote:
wrote: it's not a reason to reject the 'random length' doublet. There are indeed certain lengths that are best avoided. Certainly you don't want the doublet to be near 1/4 wavelength in total length on a band you intend operating on. Why not, other than the fact that such a short dipole will present a feedpoint impedance that has a low resistive part and a high reactive part? In the MFJ tuner manuals, there is some text on lengths you would want to avoid for our purposes. Never had an MFJ - my transmatches are all homebrew. I've read the MFJ manuals, and it seems to me that they were trying to avoid lengths of antenna-plus-feedline that would present very low or very high impedances at the Transmatch end of the line. It's not just the doublet length that matters but also the length, impedance and loss of the transmission line. Antennas like the G5RV choose a combination of dipole and transmission line length that present reasonable impedances on several bands. Trick antennas such as the G5RV and OCF dipoles utilize some clever techniques to match impedance. I don't consider the G5RV and OCF to be 'trick' antennas. They're simply intelligent combinations of dipole and feed systems that have been worked out to present reasonable impedances so that line losses and Transmatch requirements are reasonable. Haven't used a G5RV, but my experience with the OCF has been fairly satisfactory. I would note that after it broke, I elected to put up another doublet with ladder line and tuner. I have been pleased with that. In the dipole-category of HF antennas, I've used G5RVs, OCFs, dipoles fed with ladder line and a Transmatch, coax-fed dipoles, fan dipoles and coax fed trap dipoles. Plus inverted-V versions of most of those. In my experience they are all comparable radiators of RF *if* they are implemented in a way that keeps feedline/transmatch loss low and gets the antenna up and in the clear. IOW, none of them are magic, and they all have their applications. They [antenna software] are also an excellent method of comparing the efficiencies of the various antennas. Not just the antenna but the feedline system as well. One of the biggest reasons that I suggest the general purpose doublet is that the new Op gets an antenna up that doesn't have all of the foibles of a precise dipole, such as antenna height above ground, interaction with nearby objects, and can get multi-band operation in the deal. That's true to a point, but there are other tradeoffs, such as the absolute need for a Transmatch, the need to avoid certain lengths, and the difficulty of handling balanced lines in some situations. IMHO, it is better to have a station that works well on a few bands than to have one that works poorly on all bands. Many multiband antennas, such as many commercially-manufactured "all band" HF trap verticals, are so full of compromises that their performance on some bands is highly compromised. Fortunately my Elmer pulled me aside, and said "try this". Within a week, I had my doublet up and running, and I've worked the world with it. That's the ultimate test of any antenna system: what have you worked with it? My first HF antenna was an inverted L - what some would call a "random wire", even though there was nothing random about it. It was end-fed and worked against a ground/counterpoise system consisting of the radiator piping and a lone ground rod. I made many QSOs with it and later versions. The big problem with HF/MF antennas for the radio amateur is that the best choice is so dependent on the site and what the amateur intends to do. This is why it is impossible to give general advice about HF antenna types that is any good, without knowledge of the available resources and intended use. 73 de Jim, N2EY |
Suggestion for an HF starter rig
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Suggestion for an HF starter rig
wrote
The big problem with HF/MF antennas for the radio amateur is that the best choice is so dependent on the site and what the amateur intends to do. This is why it is impossible to give general advice about HF antenna types that is any good, without knowledge of the available resources and intended use. You're right. We've (I've) made assumptions of property conditions that may not exist for the OP. My little 50 footer with ladder line was technically in the clear, but its apex was only 7 feet above the flat roof. The transmission line could only drop straight down for about 6 feet, then run suspended across the top of the roof for 20 feet, then down to the shack. Yet I worked DXCC with it, including serious long-haul, from 10 - 40 meters. We don't know the OP's situation. Howard N7SO |
Suggestion for an HF starter rig
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Suggestion for an HF starter rig
On Sep 28, 8:22 am, "Howard Lester" wrote:
wrote The big problem with HF/MF antennas for the radio amateur is that the best choice is so dependent on the site and what the amateur intends to do. This is why it is impossible to give general advice about HF antenna types that is any good, without knowledge of the available resources and intended use. You're right. We've (I've) made assumptions of property conditions that may not exist for the OP. (snipp) We don't know the OP's situation. Well, based on his call sign and the FCC's data for the address I did a bit of detective work and found that this guy will have some unique issues to deal with. The aerial photos of the address indicate that there are some mature looking trees about so some random length wire antenna may be possible. The lots seem very small compared to the size of the houses too, what we'd call zero lot line homes in the Texas area. However, the most interesting thing is that it seems that he is located in a valley with some fairly high mountains about that may limit even the best HF antenna situation. This is clearly a problem to the west as the QTH seems to be located on the base of the mountains to the west. I do like the random wire ideas though. This months QST has a brief description of one installation of a random wire loop in an attic. You just never quite know how these will perform until you put them up and try. It can be discouraging if things don't work out though. -= Bob =- |
Suggestion for an HF starter rig
On Sep 27, 2:27?pm, AF6AY wrote:
If you are satisfied with your particular method of getting RF out of the transmitter and into some antenna, fine. Satisfaction is all part of the game. Such satisfaction is not the example to set for all. It seems to me that every- one's location is different and each presents a unique problem to solve for the more-optimum EM wavefront launch direction in that location. Anyone who says that one kind of antenna is the "best" or one should "always" use a certain kind of balanced transmission line isn't looking at the whole picture. They are probably describing just the only (or a few) antenna installations they used. Yes, some antennas "work better" than others. In a particular location. All that is certainly true. But I don't see anyone saying that one kind of antenna is "best" for all locations, or that one should "always" use a certain kind of transmission line in all applications. It's also not the whole story, either, because what must also be considered is the sort of radio operation that is being considered. Does the ham want only DX, or regional/national QSOs? Several bands, or only one or two? Will operation be confined to one part of a band, or spread out over the entire band? What time of day will most operating take place? Will there be ragchewing, net operations, contesting? All that and more have an effect on what the 'best' antenna is for a given location. For someone just starting out, I would suggest just a vertical for HF. Depending on a whole bunch of factors, that could be good advice, or very bad advice. It is the least obtrusive to neighbors Not always. It depends on the location. A wire antenna can be much less noticeable than an HF vertical in many situations. (can be described as a "flagpole") Perhaps, but I don't think anyone who has seen a typical manufactured amateur HF trap vertical would consider "flagpole" an accurate description. and most will perform adequately (to launch an EM wavefront) with a few radials for the "ground." Maybe - and maybe not. The performance of an HF vertical is dependent on many factors, such as the ground system, objects in the near field, how much loading is used to obtain resonance, ground losses in the Fresnel zone, etc. No, it won't win awards or work DX "better" than Brand Y using Brand T transmission line, but it WILL radiate adquately...and that's the whole name of the game, ain't it? :-) It may not radiate adequately. For example, on the lower HF bands such as 80/75 and 40 meters, the dimensions of a full-size quarter-wave vertical and radials may become impractical (60+ feet on 80/75, 30+ feet on 40 meters). Most trap vertical designs use a considerable amount of inductive loading on those bands, reducing the efficiency and radiation resistance as well as the SWR bandwidth. The lack of high-angle radiation from such a vertical may make it almost useless for daytime and closer-than-DX-but-farther-than-local communication on those bands. An amateur located in a valley, such as the one who started this thread, might prefer useful radiation that leaves the antenna at angles that would leave the valley. At this point in the sunspot cycle, the amateur bands above 11 MHz are often useless for ionospheric propagation much of the time, particularly during darkness hours. Having an effective antenna for the lower HF bands can be the difference between making QSOs and not making them. There's also the cost factor. Yes, "everyone's location is different and each presents a unique problem to solve". Which means that recommending a vertical antenna to someone just starting out could be very bad advice unless a lot more information was gathered first. And if Brand Y using Brand T transmission line works better, why not use it? IMHO, the "whole name of the game" is useful radio communication. IOW, making QSOs. I have seen situations where it was good advice to tell a ham starting out on HF to put up a vertical. I have also seen situations where that would be very bad advice. Same for dipoles of various kinds, loops, random wires, etc. 73 de Jim, N2EY |
Suggestion for an HF starter rig
On Sep 28, 9:29?am, Michael Coslo wrote:
wrote: On Sep 27, 10:53?am, Michael Coslo wrote: Why not, [use a 1/4 wave dipole] other than the fact that such a short dipole will present a feedpoint impedance that has a low resistive part and a high reactive part? That's a pretty good reason, though. 1/4 wavelength dipoles - make sure to read that as total antenna length, not 1/4 wavelength per leg, are just a troublesome combination that a lot of tuners can't tune very well. I'm not convinced. Depending on the transmission line impedance and length, the shack-end Z could be within the matching range of the Transmatch. I don't consider the G5RV and OCF to be 'trick' antennas. They're simply intelligent combinations of dipole and feed systems that have been worked out to present reasonable impedances so that line losses and Transmatch requirements are reasonable. They are very clever. The OCF especially is a joyful playground to work on with antenna design programs. It is a great way to learn both the programs and antenna theory. Agreed. But so are other implementations such as trap dipoles and the classic dipole-with-ladder-line feed, where you try different dipole and transmission-line lengths. Often the idea of "low SWR" is put out as if it is the sole criteria. Too often. In defense of SWR lovers, modern Rigs really hate High SWR, especially reactance of the capacitive kind. Well, that depends on how you define 'modern'... But a 50 ohm resistor has 1.1:1 VSWR, and some manufacturers have taken advantage of that sort of thing in the past. Not just in the past. Google "Maxx-comm matcher" (try different spellings). Those folks are still in business. The problem as I see it is that most new folks these days start out with an "all band" radio, and are inclined to want a antenna that is likewise all band. Which may or may not be a good idea. If the only bands that are open when you have time to operate are ones where your antenna works poorly, the result is going to be frustration. A lot of Western and Eastern EU, Great Britain, Iceland, Norway, most of South/Central America, about half of Africa, Israel, Australia, Antarctica, and a couple others. On which bands? No JA or far eastern countries, but I haven't tried really hard, I just work 'em if I happen to hear them. Of course from EPA, VK-land is about the antipodes. I once accidentally worked a fair part of a contest once on 75 meters on probably around 3 watts, mostly into California - I had tuned the antenna, and forgot to turn the power back up. I had works around 25 QSO's before catching that one. Situational awareness, that's all. With my rig, the power level is pretty obvious. Of course, that isn't quantified data, it's just anecdotal. But running at QRP levels does make for a more stern test of an antenna's abilities, especially if there isn't obvious signs of it, such as not getting calls answered. Sold me on the thing. The Ultimate Test is "what have you worked on it?" Theory is great but the real proof is in the QSOs. The technical details are that it is a 96 foot total length dipole, up around 55 feet, the center support is a short length of pvc tubing. I suspect that the 96 foot length was decided because that's what would fit in the available space. The ladder line is soldered to the respective dipole wire. Ladder line makes an almost straight drop to the Shack window. Definitely not the best thing going, but not too bad. Actually, what you describe is pretty close to optimum for a simple multiband antenna system in limited space, which I suspect is the main issue. Are you using true ladder line, or "window line" (Twin Lead with holes punched in the insulation)? True ladder line (heavy wire, wide spacing, mostly air insulation) has lower loss and less weather effects. If the line is short there's not much difference, but as frequency and line length increaseit can be worth changing out. Depending on the shack-end impedances, different Transmatches can have more or less loss. The worst-case scenario is where a 4:1 balun is used with a shack-end impedance that has low resistive and high reactive values. The poor Transmatch has to try to deal with one quarter of the resistive part! 73 de Jim, N2EY |
Suggestion for an HF starter rig
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Suggestion for an HF starter rig
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Suggestion for an HF starter rig
"Michael Coslo" wrote
A few years back I did a modeling of an antenna that was 1/4 wavelength long at I think 40 meters. The SWR of the antenna was approaching infinite. If I get the chance, I'll model it again tonight - I'm doing the mass mailing for the PAQSO party tonight, and if all goes well, I should have a little time. I'd think a strict 1/4 wave, regardless how it's fed, would be pretty horrific on that specific band. (But I couldn't explain why...it's just from what I've read.) That's why I made mine (55 feet) so that it was under 1/4 wave for 40, and more than 1/4 for all the higher bands. As for window line being affected by water... yes, it is, but I never found it a big deal. As I recall, I just retuned some of the transmatch settings to accommodate. I used both 450 and 300 ohm window line... and even tv twinlead. What fun I had one night when I heard a cat playing on my flat roof, and I could tell he was playing with the transmission line that was suspended about a foot off the roof... I transmitted 100 watts and heard him take off like a shot! BTW, I wonder what happened to the OP? Did we drive him away? ;-) Howard N7SO |
Suggestion for an HF starter rig
On Oct 2, 3:20?pm, Michael Coslo wrote:
wrote: On Sep 28, 9:29?am, Michael Coslo wrote: Depending on the transmission line impedance and length, the shack-end Z could be within the matching range of the Transmatch. A few years back I did a modeling of an antenna that was 1/4 wavelength long at I think 40 meters. The SWR of the antenna was approaching infinite. ??? With reference to what sort of feedline? SWR only has meaning wrt a particular line impedance. If I get the chance, I'll model it again tonight - TNX In defense of SWR lovers, modern Rigs really hate High SWR, especially reactance of the capacitive kind. Well, that depends on how you define 'modern'... Non-tube? Don't get me wrong, I LOVE tube rigs. There have been non-tube ham rigs for a couple decades now.... In a way, we have come full circle. Look back 50-odd years, and most ham rigs could match an SWR of 3 or 4 to 1 without a tuner, because they had fairly wide-range pi-networks. That was sacrificed to the desire for miniaturization, but even as late as the early 1980s, there were rigs with tube finals that could match 2:1 SWR or so. Meanwhile the SS rigs wanted 50 + j0 loads for their no-tune finals, so Transmatches became very common - so common, that rigs began to offer them built-in, so the rig could match SWR of 3 or 4 to 1. Only difference was automation. The more things change.... Google "Maxx-comm matcher" (try different spellings). Those folks are still in business. That's the one I was referring to. Hard to imagine they are still doing business. The ARRL Product Review where they tested one, then X-rayed it and opened it up to show the resistors was well over 20 years ago. The fact of the matter is that they *do* work - just not very well. Mostly 20 and 40. Just a few of the near out of country neighbors on 80. WInter nights are coming. That's when 80 and 40 really come into their own. I suspect that the 96 foot length was decided because that's what would fit in the available space. Yup, I tried a few dipoles that were longer, and made a Z shape. They worked okay, but were a lot more maintenance. Lots of tree whipping in storms here, and I almost made plastic pully's into the end insulators to combat the extra movement. But I went back to the 96 foot length IMHO, amateur radio antenna design is no more than 10% electrical engineering and no less than 90% mechanical engineering. In many cases it's 5%/95%. Actually, what you describe is pretty close to optimum for a simple multiband antenna system in limited space, which I suspect is the main issue. I agree. What really surprised me was that the performance on 75 meters was pretty acceptable. Not really a surprise to me. While short, the 96 footer and lowloss feed system will put significant RF in usable directions. I mostly get down there during contests, and have had nice results. Worked enough people to make it worthwhile. CW SS is a month away.... Are you using true ladder line, or "window line" (Twin Lead with holes punched in the insulation)? True ladder line (heavy wire, wide spacing, mostly air insulation) has lower loss and less weather effects. If the line is short there's not much difference, but as frequency and line length increase it can be worth changing out. I use the window line. I have heard of the advantages of the true ladder line, and certainly the higher impedance is one of them. Higher impedance in and of itself doesn't make the difference. What matters is the lower loss due to more copper and less dielectric. The ocarc transmission line loss calculator does balanced lines as well as coax. I've heard of some of the drawbacks of window line, such as it's performance when wet. I did take issue with the test method cited by many, in which the window line was dunked in water that included a wetting agent. My contention is that the experiment showed the effects on window line with wetted line. My experience has been that window line does not wet in this manner. When the experimenter has to add a chemical to coat the line with water, it is altering the conditions and producing results germane to only those conditions. I agree. A spray with the garden hose will adequately simulate a rainy day, I think. I think your biggest possible improvement would be to see how lossy your tuner/transmission line combo really is, and improve it if possible. 73 de Jim, N2EY |
Suggestion for an HF starter rig
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