Guidance on FM receiver antenna made of a single (insulated) wire - Page 1
Forum section: electronics / rf-microwave

author: VinzC
author_rank: Frequent Contributor
timestamp: June 19, 2024, 06:12:35 pm
content: Hi.I'm currently designing an FM radio (87-108MHz) receiver module based on aSi4705. The receiver will be placed in a device that is made of an aluminium enclosure, about 10-20cm long and 5-6cm diameter. Not all faces might be metallic but let's assume they'll all be, which rules out the possibility of an embedded antenna inside the device.Unfortunately Skyworks design guidelines do not seem to provide any hint about using a single wire as an antenna, like many portable radio receivers I've seen that are designed that way. I imagined several possibilities, which includes piercing a whole in the enclosure and let the (insulated) antenna wire pass through it but I don't like that idea very much as it would damage the wire in the long run (unless I mount some protective ring/gasket around the wire).I am also considering a connector; but then what? A panel-type connector that is mounted onto the enclosure? If so, what connector type makes sense? And how about the path between the connector and the PCB? I guess another connector on the PCB is overkill, right? On the other hand, soldering a wire between that connector and the PCB might make the whole device a little bit more fragile, e.g. when tearing it apart. Or would it?So I'm a bit out of ideas. Or maybe I'm just overthinking it, I don't know.What kind of practical options are available?Thanks in advance for any hint/suggestion.

author: Grandchuck
author_rank: Super Contributor
timestamp: June 19, 2024, 06:58:55 pm
content: https://www.amazon.com/Antenna-Ancable-Telescopic-Connector-Receiver/dp/B07PT76LW4/ref=sr_1_1_sspa?crid=13RTPZIUP6KPO&dib=eyJ2IjoiMSJ9.cUSd5X9C1i2lXZNVLpnIoLdMVlxB22ZssYxebIuqRh0nABym_-a7E6iAr6OPZafIQvMtSr5CT-CkLSzbcBTYDqypx9yGpLrJZUjDCY1op3_2KMSY1CcBiYdMWEXDPOeFpfdXHrTCda8akz4ywWHOcyqQs5Q1HzlG3GLo0xiiBowNnq77w1fyf9aaUHBO2TzHHIiwEXhmZRufTIWAuPKPpkgYONPWOkfSlJrDJc42j48.vu7fYNjV4v8QU5X8URkEJmzCuSPaehAXeZjsHRgc_2c&dib_tag=se&keywords=telescopic%2Bfm%2Bantenna&qid=1718823472&sprefix=telescopic%2Bfm%2Ban%2Caps%2C119&sr=8-1-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9hdGY&th=1

author: RoGeorge
author_rank: Super Contributor
timestamp: June 19, 2024, 07:25:58 pm
content: Maybe use a 3mm audio jack and a headset (or just a wire on a jack) as antenna, just like the FM radio does in the mobile phones with a jack connector for wired headsets.

author: VinzC
author_rank: Frequent Contributor
timestamp: June 19, 2024, 10:25:54 pm
content: Quote from: Grandchuck on June 19, 2024, 06:58:55 pmErm... Could you please elaborate?Quote from: RoGeorge on June 19, 2024, 07:25:58 pmI thought about that, too, in the end... Just wasn't too sure about it. Looks like hassle free and totally viable. So thanks a lot for the suggestion.

author: radiolistener
author_rank: Super Contributor
timestamp: June 20, 2024, 12:29:52 am
content: Quote from: VinzC on June 19, 2024, 06:12:35 pmSingle wire antenna is very bad antenna. This is because this is unbalanced antenna and needs counterweight. Usually handheld radio uses metal chassis/case or PCB ground as antenna counterweight. But if such device is powered from mains or connected to some other equipment which is connected to mains, it means that antenna counterweight is connected to the mains and other noise sources. As result, it leads to pretty high noise interference on receiver.Symmetric dipole antenna is much better from this point of view, because it don't needs counterweight, so all what you need is just to put RF choke on coax cable which is used to connect antenna. In such way you can easily block common mode currents from mains and other equipment which is connected to your receiver.With asymmetric antenna (like single wire) it is impossible, because it always uses something as counterweight and adding RF choke will reduce antenna efficiency, and useful signal will be attenuated the same as interference from mains and other equipment.This is why signle wire antenna works good for handheld radio receivers which works from the batteries and is not connected to mains and other equipment. But if there is some connection to mains and other equipment, it makes single wire antenna very bad.But again, it depends on conditions. If you're planning to use such receiver in a deep forest, where is no noise sources, single wire antenna may work pretty good.

author: themadhippy
author_rank: Super Contributor
timestamp: June 20, 2024, 12:42:18 am
content: QuoteAnd yet they've been used fairly successfully on 1000's of commercial fm receivers in the guise of a telescopic rod

author: shabaz
author_rank: Frequent Contributor
timestamp: June 20, 2024, 01:50:01 am
content: This one uses a near-similar Silabs chip. It was a toy for kids. I used a 2mm banana socket. Alligator clip (not electrically connected) on the other end so that it can be clipped to (say) blinds/curtains. The box is all-metal, and opens to store the antenna cable inside.The white stuff holding the power on/off button PCB at right-angles, is Polydoh. It's great for quickly doing simple structural things without a 3D printer.

author: radiolistener
author_rank: Super Contributor
timestamp: June 20, 2024, 07:22:40 am
content: Quote from: themadhippy on June 20, 2024, 12:42:18 amIt's the same as talking that night vision camera is useless to record video of a scene which is illuminated by the sun and high-power spotlights. Yes, when you have very illuminated scene, you're don't needs proper optics and infrared sensor to capture video. But if you're want to record video with no powerful spotlights, it requires proper good optics and sensitive camera sensor.The same cheap WFM broadcast receiver is intended to receive very powerful signals from a powerful nearby transmitters (1-30 kW power). Such signal is about 60-90 dB above noise floor. Broadcast WFM are very strong signals, because they using very high power kilowatt-range transmitter and working on a short distance. So weak interference doesn't affect it much, because signal is hundred and thousands times stronger than these interference.But if you're trying to get DX WFM reception from transmitter on a long distance, it's the same case - single wire antenna will be bad choice, especially in presence of nearby noise sources and mains, especially if it's connected to receiver.

author: ftg
author_rank: Frequent Contributor
timestamp: June 20, 2024, 07:38:51 am
content: I'd personally use a 50ohm BNC connector on it.But it all depends on the intended users.If it is radio hobbyists, 50ohm BNC is a nice choise that gives a lot of flexibility.If normal consumers, then F-connector or Belling-Lee "PAL" connectors might be options.For something portable and handheld I have seen 3.5mm jacks being used for external antennas, but mostly in portable shortwave radios.If a connector is used, I'd make the internal connection from it to the RF input on the module via coaxial cable.Consumer products often just use a piece of wire for it and it's not a huge problem in a plastic case.And most importantly, a piece of wire is the cheapest option.

author: radiolistener
author_rank: Super Contributor
timestamp: June 20, 2024, 07:50:49 am
content: Regarding to connectors, SMA is a good choice. This is de-facto standard for different RF gadgets.You can also use BNC, it is more easy to connect/disconnect, but it has less reliable connection and more large dimension.Since you're making WFM broadcast receiver, you can use standard 50 Ω input, it allows to put random wire for RX for a strong signals in the city and also allows to connect proper antenna for DX RX on long distance with very weak signals.If you're building cheap WFM broadcast radio which is not intended to receive weak signals, then you can just solder a piece of wire directly on the PCB pad, it will be cheap and enough solution which will works good.

author: tautech
author_rank: Super Contributor
timestamp: June 20, 2024, 08:10:37 am
content: Quote from: radiolistener on June 20, 2024, 07:22:40 amTell that to my dear departed dad that listened to transmissions from the northern hemisphere 20,000 km away !And got dozens of Q cards from his reports of such transmissions.....and 70 years ago with just 30m of wire.

author: radiolistener
author_rank: Super Contributor
timestamp: June 20, 2024, 08:22:12 am
content: Quote from: tautech on June 20, 2024, 08:10:37 amIf you read me carefully I already note, that such antenna can work good enough in some specific conditions when you are far away from noise sources and mains or when your radio is not connected to anything else. Like deep forest, desert or grain fields, it includes northern pole.You're needs to understand that the issue with such antenna is that it has a hidden part (counterweight) which leads to unexpected reception of interference from mains and connected equipment, because mains and connected equipment become a part of such antenna. If there is no such noise source, it can works pretty good. This feature is used in handheld radio, because it galvanically isolated from mains and other equipment and allows to use simple cheap and dumb single wire as antenna.To be clear, I also was used long wire antenna for QSO. But this doesn't means that this is a good antenna. I can say that this kind of antenna is the most worst antenna for noisy environment. But it can works pretty good in the deep forest far away from cities and buildings, just make sure that you're not use any kind electronic gadget (like smartphone, tablet, or even electronic wrist watch) near such antenna and receiver.Also don't be surprised if such antenna will give you some noise received from your receiver, especially if your receiver has digital circuits...

author: iMo
author_rank: Super Contributor
timestamp: June 20, 2024, 08:44:13 am
content: Quote from: tautech on June 20, 2024, 08:10:37 amI've been doing the same with a 21m long antenna, and it could be done with even shorter antenna, indeed..But you cannot compare ham radio HF receivers/transceivers with the standard "VHF FM broadcast" radios, moreover the way the standard VHF FM broadcast propagates is different to the ham radio HF propagation.Back to the OP question - the easiest way is tho have a panel type BNC or SMA connector mounted on the box and a piece of coax (or even a short straight twisted wire) soldered to the PCB. You may use a 2 pin header on the pcb as well. For the local VHF FM broadcast reception the type of connectors does not matter much. The antenna could be a telescopic antenna (or a piece of insulated wire), usually lambda/4 long.For DX VHF FM (DX aka "long distance", mind the DX reception is matter of rather special short live tropo/ionospheric conditions) you would need a higher gain antenna, for example a 3+ element Yagi antenna.https://en.wikipedia.org/wiki/TV_and_FM_DXhttps://en.wikipedia.org/wiki/Antenna_types

author: tautech
author_rank: Super Contributor
timestamp: June 20, 2024, 09:04:53 am
content: Quote from: iMo on June 20, 2024, 08:44:13 amQuoteSW directional broadcast I don't think can be called ham.Back nearly 60 years ago pop showed me how to wind antenna coils, some tapped and others tunable and even wave traps that we detected with everything from blocks of Germanium crystal and cats whiskers, Germanium diodes, silicon diodes and 6H6 double diode valves and none were of any use without a length of wire to the nearest tree.Even now for decent FW reception my shed radio has a few meters of plain wire strung in the rafters .......

author: radiolistener
author_rank: Super Contributor
timestamp: June 20, 2024, 10:36:21 am
content: Quote from: tautech on June 20, 2024, 09:04:53 amProbably you're mean WFM broadcast reception. As I said before, you can listen local strong WFM broadcast stations in the city with no antenna at all. Just because it uses 10-30 kW transmitter just several kilometers away, so it's signal is thousands times stronger than RFI.For example, here is WFM broadcast band, as you can see LNA gain is off and the all stations SNR is about 60 dB. And I'm not too close to transmitter:For comparison, with LNA gain off there is even no sign of signal presence for ham radio transmitters with 10-20 W power - they below noise floor and I need to set +40 dB gain in order to listen them.But if you want to receive WFM broadcast 150-200 km away from transmitter, a short random wire is not suitable for that. You're needs a good antenna.

author: themadhippy
author_rank: Super Contributor
timestamp: June 20, 2024, 10:59:34 am
content: Quoteand whats the op asking about?Quote

author: radiolistener
author_rank: Super Contributor
timestamp: June 20, 2024, 11:06:38 am
content: Quote from: themadhippy on June 20, 2024, 10:59:34 amI answered totautechpost, which mention "FW reception", I don't know what is "FW reception".I think he mistyped "FM", so this is why I clarified it.If you want DX WFM reception it needs good antenna because there is high attenuation due to bad propagation on long distances.Small piece of wire will not work, it just will be flooded in noise. But during power outage, when all noise sources are off, I can receive DX WFM stations even on telescopic antenna, but it is very sensitive if there is working power bank.The same, when I used long wire antenna with tuner on 40 meters band, it just flooded in a very high noise, so I cannot hear something. But during power outage when all noise sources are off I can get on the same long wire antenna QSO with operators which are >10000 km away (opposite side of Earth).North Pole is also good condition, because there is no cities and noise sources, so using long wire can give you good result, but definitely not the best in comparison with a a good proper antenna.

author: pienari
author_rank: Regular Contributor
timestamp: June 20, 2024, 06:47:18 pm
content: I have used SDR for WFM dx .Now is es time and i have received few OIRT FM stations from Ukraine over 2000km away.I used my 4m band 6el quad beam.

author: VinzC
author_rank: Frequent Contributor
timestamp: June 21, 2024, 04:13:28 pm
content: Thanks for taking the time to answer and for all your suggestions.For the record, here's what the relevantapplication notes for the Si4705has to say about whip antenna (the only thing close to what I want to implement):QuoteAnd that's about it. I have thus far not found any reference to mounting recommendations. So I need something practical for a portable FM radio receiver. So since I am used to devices with a single wire attached, I thought about going that way. A telescopic antenna is less practical though. However, I'll see what gives when I'm done with the whole design.So thanks for the options. I might report my findings here when everything is finalized.

author: A.Z.
author_rank: Super Contributor
timestamp: June 21, 2024, 04:49:53 pm
content: Quote from: VinzC on June 19, 2024, 06:12:35 pmuse thishttps://nomonsuhendar.blogspot.com/2020/12/flower-pot-antenna-calculator.htmlcalculate it for the desired center band frequency and use a BNC connector for the receiver, if used "at home" use a run of RG6 to connect the antenna to the receiverif you, then, feel the need for a preamp, this onehttp://sm0vpo.altervista.org/antennas/preamp-0.htmis both simple and effective.

author: VinzC
author_rank: Frequent Contributor
timestamp: June 23, 2024, 01:01:56 pm
content: Quote from: iMo on June 20, 2024, 08:44:13 amThanks, that is indeed interesting. I am extremely curious about the following points:Doesn't the impedance of a 50 ohms coax cable and connector affect the signal if the antenna is [supposed to be] a mere wire (say λ/4)?How about the difference in impedance between the PCB trace and the input FM integrated circuit?If the insulated wire should be a fourth of the wavelength, doesn't the length of the small coax cable between the PCB and the connector on the case/enclosure matter?Theschematic in the application notesassumes a whip antenna, which I suppose is the same as a single wire¹. What are the consequences of inserting a controlled impedance path (of, say, 50 ohms) between the PCB and a connector on the case/enclosure (assuming the external antenna wire is attached to the central conductor of that external connector)?¹ FTR the advertised input impedance of the RF amplifier is 4kΩ / 5pF.

author: radiolistener
author_rank: Super Contributor
timestamp: June 23, 2024, 02:51:38 pm
content: Quote from: VinzC on June 23, 2024, 01:01:56 pmWhen you use unbalanced wires as antenna, you're needs to understand that coax cable also become a part of antenna and receive a lot of noise from your nearby equipment which will flood the signals from remote transmitters.Quote from: VinzC on June 23, 2024, 01:01:56 pmproperly designed PCB has transmission line with 50 Ω impedance which is well matched with connectors and coax cable. It take into account PCB dielectric properties and use specific trace sizes and a gap to the ground which size is calculated in that way to get proper impedance.Quote from: VinzC on June 23, 2024, 01:01:56 pmYou're needs to understand, that if your antenna is not matched with coax cable and don't use balun, your coax cable will become a part of antenna, so there is no sense to talk about wire size, because you're don't know your coax cable size which matters very much because it will be a part of antenna.It's mandatory to understand, that current don't behave like smart substance that can see difference between antenna wire and coax cable. If you connect wire to coax cable with no special measures, your coax cable will just extend your wire and become a part of antenna.Quote from: VinzC on June 23, 2024, 01:01:56 pmNo, whip antenna is not the same as single wire. The whip antenna is a kind of antenna with a small size in order to reduce near field coupling. Such antenna has very bad efficiency due to small size, so it uses low noise amplifier to amplify the signal. But it's performance is limited with noise floor.And there is no such term as "single wire antenna". Such antenna doesn't exists - it's just impossible. Any antenna has at least two wires - radiator and counterweight. One wire can be shorter or longer than other (in this case this is unbalanced antenna), but any antenna has at least two wires or more from the feeding point.If you're see that some antenna consists of one wire, for example handheld radio, it doesn't means that it uses signle wire, such kind of antenna just uses its metal case or some massive metal element under plastic cover as a counterweight.

author: A.Z.
author_rank: Super Contributor
timestamp: June 23, 2024, 06:59:19 pm
content: for an antenna to work some current has to flow on itfor a current to flow, there must be an equal and opposing current flowing "elsewhere"think at a light bulb and a battery, will the bulb light on if you only connect a single wire between the bulb and the battery ?

author: VinzC
author_rank: Frequent Contributor
timestamp: June 23, 2024, 09:46:29 pm
content: Quote from: radiolistener on June 23, 2024, 02:51:38 pmPlease do not nit pick vocabulary, I'm not a complete beginner in RF. You know *exactly* what I meant. My goal here is to understand how it works, not to debate about the vocabulary/jargon. So if you know the term or expression to be used in this case, please be my guest and kindly inform me how it must be called. There are zillions of antenna types and I haven't so far figured out the term.

author: radiolistener
author_rank: Super Contributor
timestamp: June 23, 2024, 10:11:41 pm
content: Quote from: VinzC on June 23, 2024, 09:46:29 pmI talked not about vocabulary.What I said is that there is no single wire antenna, because this is impossible from physics point of view. This is typical misunderstanding of beginners. If you're using a wire as antenna, it needs counterweight wire.You can imagine antenna as a water pipe, where pipe is wire and water is electrons. The goal is to pump water back and forth in the pipe, you cannot do that if your pump is connected to a single pipe and second side of pump is closed (no counterweight).The same thing with antenna, if you use single wire, you cannot move electron gas in the wire back and forth if you don't have second wire at feeding point.

author: VinzC
author_rank: Frequent Contributor
timestamp: June 23, 2024, 10:26:06 pm
content: Quote from: radiolistener on June 23, 2024, 02:51:38 pmOk, fair enough. That I suppose makes for a "yes" to my third question.Quote from: radiolistener on June 23, 2024, 02:51:38 pmYou're assuming a lot of things here (besides me not even understanding those concepts, which is a bit hasty to begin with). Not even sure you're actually replying in the context of the information I spent time to share about the FM chip... I don't know if you've read my other messages but the schematics doesn't imply a 50 ohms impedance of the PCB trace that goes out of the FM antenna input of the Si4705. There is neither any information about impedance matching of the path between the antenna and the input of the chip. Did you actually check the datasheet and the application notes I linked to?The thing is I'm not asking for some random receiver. I'm asking for details about the antenna given that I'm not going to use a whip but a single wirein the context of a Si4705 as the receiver. So, I don't know, let's say, for instance, should I use the LPI input instead of the FMI input?Quote from: radiolistener on June 23, 2024, 02:51:38 pmI understand the concept of impedance matching, which is why I asked how the suggestion (of using a coax cable to link to the antenna connector from the PCB) would work and what the implications would be, given the information dispensed in the application notes, which *doesn't provide any information about mounting* and even less about a coax cable as a temporary path between the PCB and the antenna wire.Quote from: radiolistener on June 23, 2024, 02:51:38 pmErm... how d'you call...I'm an electronics design engineer, just not specialized in RF. Can you please switch to another register? I'm not a 3-year old anymore.Anyway...So far I'm not really much further in my understanding, including all the questions I asked before.No offense but I haven't found in your... (how d'you call...) details (is that the right term?) anything that I would qualify a substantial answer to either of my questions, except for the first one which is more about answering to third question I asked earlier. Quite the contrary, your answers appear way more confusing than if I hadn't asked anything...So does that make sense to use a coax cable from the PCB (which is, by the application notes, I guess, supposed to be designed for a whip antenna) to the antenna connector?If it makes sense, I also assume I shall do impedance matching, right?So if I need to do that, back to my first question in this message: does it even make sense given the application notes doesn't mention that at all?You've also said that making the single-wire antenna a quarter of the wave length is irrelevant without impedance matching (or whatever). But then why does the application notes recommend such a length (especially given that there's no mention of impedance matching)?You've also said there's a difference between a whip antenna (did you actually see/check/verify the model I linked to?) and a single wire but you didn't explain what these differences are, nor what to do/change (with respect to the application notes) to use a single wire instead of a whip antenna...which was the reason I started asking here...And lastly: what's the difference between (sorry, you didn't give any hint as to how to call it) a single wire antenna and a whip antenna¹?¹ Please refrain from mentioning the efficiency part, you've already mentioned that a couple of times, I've read that, gotten that, so thanks.

author: VinzC
author_rank: Frequent Contributor
timestamp: June 23, 2024, 10:35:58 pm
content: @radiollinstener:Also bear in mind that, despite your theoretical knowledge, which, from what I understand, seems to deny the existence of radio receivers equipped with a single wire as an antenna, such receivers **do** exist and have been around for a long time — they still are BTW, regardless of the theoretical impossibility you seem to clutch onto. And, yes, contrary to your bald assertion, there are which are supplied from mains and not batteries. If I could ram into my ex-wife's house, I'd take a picture of the radio in question (if only the damn cat hadn't chomped the wire). And, yes, the efficiency may be tragically low but those FM circuits are designed by RF specialists and they **do** account for that.Ah, and if there's "no such thing as a single wire antenna", please be so kind as to provide the **exact** terminology, so that I no longer look like some "illiterate" electronics n00b.

author: radiolistener
author_rank: Super Contributor
timestamp: June 24, 2024, 12:49:17 am
content: Quote from: VinzC on June 23, 2024, 10:26:06 pmI understand that you're don't familiar with RF things, and I just trying to explain things in simple words which should be easy to understand for you. I think it should be pretty easy to understand with no knowledge in RF. But if it still looks complicated, probably it will be better to start from basic physics questions related to electricity.I'm afraid, without basic knowledge on how RF power flows in the feeder, it will be almost impossible to understand how to properly design RF frontend for your FM chip...For frequencies above 100 MHz it even much more important than for short wave...Quote from: VinzC on June 23, 2024, 10:26:06 pmThere is no such concept as "single wire antenna", it is physically impossible.If you're think that single wire can work as antenna, then you're don't understand how antenna works.Quote from: VinzC on June 23, 2024, 10:26:06 pmThere is no sense to provide information about antenna mounting in the receiver chip datasheet. It will be useless and not relevant information for the chip. All what you need is to match impedance between the chip input (it is 4 kΩ according to datasheet) and coax feeder. This helps to get the best receiver sensitivity. The antenna mounting questions is antenna design related questions and is not related to receiver chip.

author: shabaz
author_rank: Frequent Contributor
timestamp: June 24, 2024, 01:21:07 am
content: QuoteHi, he doesn't need to design a front-end. The documentation already mentions what's required between the IC and the antenna.@OP:As I understand, you wish to use a single wire as an antenna for a portable FM broadcast receiver. Very practical choice.If it were me, I'd lay out the circuit that they mention in the guide, i.e. capacitor, inductor, and the protection diodes, and then just pick any connector. I used a 2 mm banana socket for my metal cookie-tin Silabs radio project, but you could equally use a 2.5mm or 3.5mm audio plug, or a BNC socket or SMA socket as people mention, or anything really. It makes little difference which of these connectors you choose, and it can be a low-quality connector, because you're not relying on 50 ohm impedance, you're merely relying on simple electrical insulation from the pin that you will use in the connector, to the metal enclosure.SMA and BNC will allow you to use an off-the-shelf telescopic antenna if you wish, since they frequently come with SMA or BNC plugs on the end. If you're not interested in telescopic, simply use any connector you want.It's actually hard to get it wrong with these Silabs chips with solely the info they provide (no need for any RF expertise), you will certainly receive all the local FM broadcasts, and quality will be very reasonable too (it won't ever be "Hi-Fi", because these Silabs chips can't achieve that, but it will be typical portable radio or basic car stereo quality).

author: radiolistener
author_rank: Super Contributor
timestamp: June 24, 2024, 02:01:13 am
content: Yes, for local WFM broadcast reception it doesn't matter much how you implement it. It should work even if you just put a random wire to the input pinBut for a weak DX reception there is a sense to implement impedance match circuit, because input impedance of that chip is 4 kΩ according to the datasheet. Adding impedance match circuit can help to improve noise figure and get better sensitivity.

author: shabaz
author_rank: Frequent Contributor
timestamp: June 24, 2024, 02:11:47 am
content: The documentation already discusses the impedance match, for the whip antenna. That's already part of the circuit. What impedance match are you referring to? Bearing in mind, the OP specifically asked for a single wire as an antenna in the very first post. Please stick to the topic now, because it's already unnecessarily clouded a lot of things for the OP.

author: radiolistener
author_rank: Super Contributor
timestamp: June 24, 2024, 03:02:09 am
content: Quote from: VinzC on June 23, 2024, 10:26:06 pmIt depends on your requirements for receiver, if receiver performance is important for your receiver, then yes - it has a sense to use impedance match circuit and coax cable with RF chokes to antenna and use proper good antenna.But if you're planning to listen for a very strong local stations then there is no sense for that, you can simply use a random wire which will works and adjust its size experimentally.Quote from: VinzC on June 23, 2024, 10:26:06 pmYes, if you're want to get the best receiver performance (noise figure, sensitivity).No, if you're planning to listen for a strong local stations.Quote from: VinzC on June 23, 2024, 10:26:06 pmAN383 just explains how you can practically use it for a local strong station reception, like usual cheap WFM broadcast receiver, for example it provides example on how to use headphone wire as antenna.If you want to get the best result from that chip, there is a sense to experiment with impedance matching circuits. The ideal solution would not necessarily be complete impedance matching, it may appears that partial impedance matching can give you better compromise between receiver performance, price, complexity, bandwidth and distortions (it is problematic to implement high ratio impedance match with a good parameters).Quote from: VinzC on June 23, 2024, 10:26:06 pmApplication note has impedance matching inductor L1 on schematic.But actually the result will be pretty significantly depends on your counterweight geometry (ground wires) which is hard to predict.So, it's better to tune it experimentally exactly for your implementation.They recommend wire size as an example for using with their PCB layout. But it may appears that even using their PCB layout may require a little different wire size. It's just impossible to predict precisely when your PCB and ground wires will be a part of antenna and needs to be adjusted experimentally.Quote from: VinzC on June 23, 2024, 10:26:06 pmSince it's hard to predict geometry of counterweight in your implementation, there is no sense to talk about exact radiator length. You can assume it as random length wire with random resonance. And adjust it later with VNA or with testing on weak stations.Quote from: VinzC on June 23, 2024, 10:26:06 pmThe difference is that whip antenna uses two conductors connected to the feeder - radiator and counterweight.The single wire antenna just doesn't exists, the same as a single terminal battery doesn't exists. And the same as single terminal power supply doesn't exists. Such concept just don't have sense and is a kind of misunderstanding.

author: shabaz
author_rank: Frequent Contributor
timestamp: June 24, 2024, 03:53:07 am
content: Quote from: radiolistener on June 24, 2024, 03:02:09 amSo.. this has absolutely nothing to do with the single wire the OP wishes to use as an antenna!QuoteA single wire as an antenna certainly does exist. Every handheld radio has a whip or telescoping antenna on it. It's a single wire. Sure, some of them may have a helix, and others may look like a single wire but are not, but certainly a single wire as an antenna is used for decades, especially for portable broadcast FM receivers. See photo of military portable transceiver. Again, a single wire, this time, folding whip.QuoteYou're expecting an end user to pull out a VNA each time the single wire is moved/adjusted?

author: radiolistener
author_rank: Super Contributor
timestamp: June 24, 2024, 10:55:12 am
content: Quote from: shabaz on June 24, 2024, 03:53:07 amNo. This is typical misunderstanding. Telescopic / whip antenna on handheld radio is NOT SINGLE WIRE, it has two wires. The second one is counterweight placed within radio, this is a ground trace on PCB and/or aluminum chassis inside plastic cover. And you're needs to take into account counterweight size the same as telescopic / whip antenna radiator size.And when you're design input frontend impedance for such antenna, you're needs to take into account this counterweight size and geometry. Smaller size of this counterweight leads to higher impedance of antenna and going to infinity Ω at feeding point for zero size counterweight. And since zero size ground is impossible for circuit, this is impossible case and it means that such telescopic antenna / whip antenna always have second wire. The counterweight can be small but it always present and it's size has effect on antenna impedance, the same as size of main radiator. So, you can't say that this is single wire antenna.But using single wire as antenna is possible, it requires to use two terminals and connect both sides of such wire to these terminals (loop antenna). But this is definitely not the antenna OP talking about.The main issue of such antenna is that it has pretty high impedance (due to small second wire counterweight) and almost impossible to perfectly match it, so it's performance will be crap. And smaller counterweight size leads to worse performance.When counterweight size will be the same as main radiator, this antenna turns into classic center fed dipole.But since usually counterweight is smaller than radiator, such telescopic / whip antenna is an example of off-center fed dipole.Quote from: shabaz on June 24, 2024, 03:53:07 amNo, it will be annoying and don't worth the effort because such antennas are very sensitive to position and environment.Using VNA for tuning it has a sense just one time to get better performance for average conditions and counterweight size/geometry.

author: VinzC
author_rank: Frequent Contributor
timestamp: June 24, 2024, 11:42:43 am
content: Quote from: shabaz on June 24, 2024, 01:21:07 amIndeed that's the dealQuote from: shabaz on June 24, 2024, 01:21:07 amAaaaah, that now makes perfect sense to me! Thank you so much for clarifying this all for me, much appreciated. That is what I needed to know. I believe you nailed it all, thanks again.