Antenna Recommendations

Submitted ⁨⁨1⁩ ⁨week⁩ ago⁩ by ⁨I_am_10_squirrels@beehaw.org⁩ to ⁨amateur_radio@lemmy.radio⁩

I’m looking for some advice about selecting an antenna. I live in an apartment, so I can’t install anything permanent and can’t anchor anything to the house. There is a small backyard about 30ftx30ft, some arborvitaes but no strong trees. My radio is on the second floor. There are also two-story houses behind and on either side. I am currently a technician, planning to upgrade to general in the next few months. Right now I’m mostly interested in 10m and 20m, would also like 2m to reach my local repeater. I plan to use SSB and digital modes. Some possible options I’ve come up with: using a stand like this www.dxengineering.com/parts/wmo-18320 with a mast to put up an inverted V, but I haven’t done the measurements and math to see what the angle would be; my initial instinct is that it’s too sharp of an angle to be effective. I also looked at this www.dxengineering.com/parts/dxc-expedition or www.dxengineering.com/parts/but-hf9v, but I don’t have good line-of-sight with all the houses. I could do the mast stand and a mast with something like this www.dxengineering.com/parts/mkr-11-251.

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667@lemmy.radio ⁨1⁩ ⁨week⁩ ago
This is such a fun time!

Lots of good advice here. Bear in mind that multi-band antennae often have tradeoffs in terms of SWR.

Depending on how industrious you’re feeling, I’ve found tremendous success with a homebuilt vertical monoband ladder line j-pole. KB9VBR has an excellent build video. Downside is that on 20m, you’ll want a mast at least as long as the length of the antenna, but if it’s impractical, you can keep the radiating element vertical and the matching section horizontal, and even then if that’s not possible, the entire antenna can be horizontal.

Welcome to amateur radio!

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- Wahots@pawb.social ⁨14⁩ ⁨hours⁩ ago
  This might be kinda a stupid question, but does the direction of the antenna affect the output of the wave? (Eg, if the antenna is tilted 45 degrees from vertical, is the radio wave it transmits also 45 degrees from anyone else’s vertical antenna?) Or does the wave stay the same (parallel to the earth, but most of the power is just dumped in an unhelpful direction, so it doesn’t transmit nearly as far?)
  
  I know this is silly, but I don’t actually know the answer, and it makes me curious, since I tend to ski with radios, transmitting while skiing down steep slopes while people are above or below me by hundreds/thousands of feet.
  
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  - 667@lemmy.radio ⁨9⁩ ⁨hours⁩ ago
    This is a great question. There is generally a null point which extends from the top of the antenna such that if you were to point the tip of the antenna at some distant receiver, the signal would be greatly attenuated. It’s not eliminated completely for the same reason if someone is yelling but not facing you; signals can bounce or bleed around and still be intelligible.
    
    When I think about antennas, I like to imagine a donut: 🍩, the antenna extends through the center and the actual donut is the radiation pattern. This is good for mental modeling, but in application there are more things which influence radiation patterns. It’s still a good start.
    
    When an antenna is placed on its side, the closer it is to the ground, the more of its energy is directed into the ground (or it may reflect back and nullify signal coming from the antenna), but for handheld radios (which are most likely VHF or UHF), having sufficient line of sight is what’s needed to have the system work properly, and where one needs to occasionally go through walls or other simple obstructions, a little more power can be helpful.
    
    When skiing as you mentioned, have you been having any difficulty communicating with others in your current setup?
    
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- I_am_10_squirrels@beehaw.org ⁨1⁩ ⁨week⁩ ago
  Thanks for the suggestion, the ladder-line J or slim jim seems fairly straightforward to construct with good performance.
  
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  - 667@lemmy.radio ⁨1⁩ ⁨week⁩ ago
    For a monoband, they’re quite versatile. I feel one of their best qualities is that they can be rolled up, and still get excellent performance. Another quality is that they are balanced; it almost seems like magic.
    
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- I_am_10_squirrels@beehaw.org ⁨1⁩ ⁨week⁩ ago
  From what I’ve been reading in QST, this sun spot cycle is opening up lots of dx on 10m
  
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  - 667@lemmy.radio ⁨1⁩ ⁨week⁩ ago
    It’s a great time to be on 10m. My first QSOs went ~1200mi and I was only using a 1/4-wave CB mag mount whip on my car; imo the real fun is on 20m; from New Mexico I was making QSOs with Indonesia on SSB.
    
    Follow your interests, you’re going to have a great time.
    
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BenDoubleU@lemmy.radio ⁨1⁩ ⁨week⁩ ago
Those are all great options for sure. And while not an exact answer to your question, you could maybe go a bit simpler (and cheaper) for just 2, 10, & 20m like an end fed half wave.

Thoughts on how you’ll run it to your second floor?

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- I_am_10_squirrels@beehaw.org ⁨1⁩ ⁨week⁩ ago
  I currently have an end fed half wave for 10 meter. I’ve been able to receive fairly well, picking up beacons from Australia (I’m in Washington state), but haven’t been able to make contacts. I just ordered a nanoVNA so I can check the swr with the feed line.
  
  For the feed line, I’m planning to make a feedthrough window insert using some thin plywood and barrel connectors. I’ll put some mason line on the plywood so I can lower it to the ground during storms, raise it up to the window and connect when I’m operating.
  
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  - skillissuer@discuss.tchncs.de ⁨1⁩ ⁨week⁩ ago
    you might have problems with your EFHW being too lossy/undersized. check if ferrite heats up when transmitting
    
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skillissuer@discuss.tchncs.de ⁨1⁩ ⁨week⁩ ago
you’re looking for 2 or 3, possibly more, separate antennas. consider: a groundplane, sleeve dipole, copper cactus, halo antenna or small yagi (2-3 el) for 2m; you might get away with operating them on temporary stand, or even from inside apartment. groundplane for 10m (can be made from wire; 10m is wide and you want separate, single band dipole for this reason); and some kind of wire antenna for 20m, maybe also for 10m. depending on conditions one or another might be better (vertical vs horizontal polarization, height above ground etc).

one way to make the latter is OCFD, this way you can make antenna for both 10m and 20m; for this one you’d need some matching scheme based on specific feedpoint position, specific coax lengths (5m is halfwave at 10m so won’t change impedance at this band, but can be used to match 20m) or 1:4 or some other balun. see there for more info you can also try a full-wave loop for 20m if you have enough space, it’ll work for 10m as well. same applies for matching, that is, if you don’t have autotuner (but where’s fun in that?)

these commercial antennas are expensive, you can have another radio for this kind of money

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- skillissuer@discuss.tchncs.de ⁨1⁩ ⁨week⁩ ago
  antenna making is art of tradeoffs. there are different ones between size, cost, weight, mechanical and electrical complexity, wideband performance, radiation pattern, efficiency, and use of harmonics if any.
  
  for VHF and up, it only makes sense to make single band antennas because cost and size savings are tiny otherwise, but bandwidths are large and there are no reasonable autotuners. there are special cases such as 2m/70cm antennas that can do both, but that’s it. this is area of simple or folded dipoles, halos, yagis, LPDAs, helical antennas, and in bigger end of scale antenna arrays and optical-like systems like parabolic reflectors
  
  for HF, if you have budget and real estate for it, some of best antennas money can buy would be LPDA for entire range you’re interested in. this thing, however, for 3-30MHz range would be a giant aluminum triangle 40m wide, 50m long, weights well over a ton and needs mast and rotator because it’s directional, not to mention that it costs fortune. but on balance it can reject noise from wrong directions and is always matched
  
  some typical approaches are as follows:
  
  single band wire antennas. these would be halfwave dipoles in any shape (straight, inverted-v, slopers, off-center and so on), j-poles, groundplane antennas, quarterwave dipoles (requires good ground) and couple other variations. these are light, cheap, efficient, fit entire single band without gross abuse of finals, have uniform radiation pattern. but only on one band, and having multiple of them in proximity can lead to weird effects, so these are best if you’re hiking for example, but good in general
  
  principally single band wire antennas but now we also want to squeeze some other bands out of it. these are dipoles - normal or OCFDs, full wave loops in one approach and trapped dipoles in other. in first case, we exploit the fact that there are usable harmonics on some bands - 80m has 40m, 30m, 20m, 17m, 15m, 12m and 10m. 40m has 20m, 15m and 10m. 20m has 10m. but depending on type not all are always usable and higher harmonics will have narrowed usable band compared to single band case. in trapped dipole approach there’s a limit on how many traps you can put (mitigated to some degree if you make it asymmetric and put traps on one side only), and as traps work as coils, these shorten antenna which also narrows usable bandwidth but now for lower bands, opposite of the former. use of autotuner and low loss transmission line can make it work over wider bandwidth, but this only goes so far. note that some bands are narrower than others (12m, 17m, 30m, 60m) and it can be made to work for these pretty well, but less so for others (80m, 40m, 20m, 15m, 10m), but it can still work if there’s less bands on one antenna, especially if you’re not interested in entire band (like for CW-only or voice-only operators), are willing to accept some loss of power, or use tuner, or combination of some of these
  
  antennas that are by themselves not resonant at all. these are either lossy (like terminated dipole) or require tuner, sometimes purpose-built and can be narrowband when tuned (doublets, magloops) both can be reasonably compact. because match lies in tuner, these are multiband by virtue of changing tuner settings. terminated antennas have good match but also you can be dumping half of power or more in resistor. there are also ways to use mast antennas in this way, even if they are grounded (using gamma-match for example)
  
  antennas that have to be extensively electrically shortened because wavelength is huge. these are generally everything from 160m down. these are things like magloops and bespoke wire antennas with loading coils and capacitive hats and such. because these are short in comparison to wavelength, efficiency is small and bandwidth is tiny (but can fill entire band) but also require extensive space just due to how huge wavelength is
  
  some directivity can be achieved by making yagis (higher part of HF) or by deploying multiple antennas in an array. depending on band and type of antennas this can get very elaborate and expensive. simplest and cheapest way uses multiple radiating halfwave elements connected by coils, or with parallel parasitic elements. this can get decently directional while also being a bit compact but also this makes it more narrowband and due to large size only makes sense for higher HF and VHF
  
  but start simple. single band wire dipole or j-pole would be probably best in your situation
  
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