hybridfree/eevblog-posts huggingface dataset:
locating cell towers (LTE) - Page 1
Forum section: electronics / rf-microwave

author: electrolust
author_rank: Unknown
timestamp: August 14, 2020, 10:55:31 pm
content: I am in a commercial building (concrete structure and metal framing internally) in a suburban location. Outside signal is 4 bars everywhere around, but I only get 1 bar inside. I put a directional antenna on the roof, part of a cell booster kit.I used the various mapping tools available to locate the 2 closest candidate cell towers. Only one of which (the closest one) shows my building being in its defined coverage area. All candidate towers are generally south of my building, per the maps. I've verified a couple locations with google earth (can't see the towers but you can see the shadow they cast).With the antenna in that direction, I only get 2-3 bars inside. wtf.With the antenna 180° from that, in the direction that the maps show that there are no towers, I get 4 full bars everywhere inside. I definitely do not have the antenna "backwards". This points towards an "unverified" tower which google earth shows as a disconnected floating blob. It's close enough that I walked there and no, there is no tower near that location nor evidence that there ever has been. Just long standing trees, and no not a camouflaged tower. But, this is generally in the direction of the airport, under 10 miles away. Maybe there's strong coverage there that is better than the actual closest tower, at least as is able to be picked up by the booster antenna.So, with the uselessness of the tower mapping apps/sites, I would like to locate the best signal myself. Is it as simple as I think?1. Impedance match the directional booster 75r antenna to 50r analyzer.2. Calibrate analyzer.3. Set appropriate freq span.4. Rotate antenna to find strongest peak signals. Confirm this is a 4G/LTE band and note the top 3 candidates.5. Back inside, in order 1-2-3 see which gives the strongest signal on a phone.#5 maybe can be skipped if I can eliminate signals that aren't my provider, I guess per FCC data.I've already experimentally determined a 4-bar antenna direction, so in theory it's already done and done. Regardless of if I am locating the absolute strongest signal. But I wouldn't mind mapping it out if it's that easy. Maybe I don't even have to do #1 and #2 because I don't care about ampl accuracy, just relative strength. impedance mismatch would be ok in that use case?
FCC certified FOB - Page 1
Forum section: electronics / rf-microwave

author: Jester
author_rank: Frequent Contributor
timestamp: August 13, 2020, 09:10:54 am
content: A while ago I designed a simple device that receives a simple on/off msg from a smart phone. The receiver side used a $5-6 FCC certified WiFi/Bluetooth module. Works great, breezed through compliance testing for North America.I now have a request to make a version that uses a FOB instead of the smartphone for the TX side. Needs to pass FCC/IC compliance testing. So I’m looking for an economical FCC certified FOB transmitter. Volume will be in units of 1000. I will also need the compatible Rx chip set for the receive side to replace the present module.So far I have discovered some pre-certified FOB’s modules and matching Rx chipsets from LINX technology, however cost is about 4-5 times that of the Expressif module and that breaks the budget.433MHz FOB’s are dirt cheap about $1 from Aliexpress etc in volume, however finding a supplier that actually has a FCC certified FOB and valid certificate as opposed to a FOB with a fake FCC sticker is a challenge.Does anyone know of a economical <$10 certified FOB source?
QUCS assigning S1P file to a port - Page 1
Forum section: electronics / rf-microwave

author: radar_macgyver
author_rank: Frequent Contributor
timestamp: August 13, 2020, 07:29:32 pm
content: Is there a way to assign an S1P file to a port? In other words, have a port whose Zo varies with frequency? I wanted to optimize a matching network for a device that I have an S1P file for its output. I can design a simple matching network, but to optimize it, I need to have a constraint on S21. I had done this in Genesys by assigning an S1P file to a port, but I can't find a similar option for this in QUCS. Is there a different way?Thanks
RF switching PIN diode experts despartely sought! - Page 1
Forum section: electronics / rf-microwave

author: Chris Wilson
author_rank: Super Contributor
timestamp: August 12, 2020, 09:12:14 pm
content: I have a used Alpha 86 HF amateur band amplifier on the bench. It appeared to be working fine when I received it, but subsequently I have found an issue that may be related to the PIN diode RF switching that is used to enable fast CW with break in.It has two operating conditions. STANDBY where RF goes in to the antenna socket and out to the transceiver via the relay K3. So when this relay is closed RF comes in from the antenna, via the closed relay contacts, to the transceiver. in this state RX is fine. In its OPERATE mode K3 opens and RF is sent via, as far as I can read the schematic, the RX PIN diodes D3, D4, and D5. In this state the RX signal is attenuated some 3dB. More so on the higher bands.But I have just found another anomaly, in the OPERATE status if I move the TUNE and LOAD capacitor positions from where the amp is happy to load up and TX into a dummy load, but not transmitting, just receiving via the transceiver, the attenuation reduces or virtually goes altogether, depending on band. As such I am wondering if the big, rare and expensive UR4001 stud mount PIN diodes are leaking the RX signal back in to the tank circuit? I could REALLY do with someone that understands the schematic and PIN diodes far better than I to advise. If you didn't hear the drop in RX receive sensitivity, or look at the S meter, you might think, as I initially did, there was nowt wrong with it.I find it hard to believe the PIN diode set up normally attenuates 3dB!I was tempted to convert it to two vacuum relays and bypass the fast PIN diode switching, a fairly common mod, but I would rather leave it in the more valuable original state if possible. I attach two schematics, if anyone would be able to find the time and inclination to study them I would be extremely grateful as I don't want to spend a lot of dosh on fitting new stud mount PIN diodes if it might be just D3, D4 and D5. These are also near unobtanium, but Alpha now say it's OK to replace them with "low capacitance" 1N4007's. I can find nothing lower than 8pF ones, so i guess they mean those. Alpha have shut for the virus with no signs of opening again any time soon.Thanks a lot!

author: cdev
author_rank: Super Contributor
timestamp: August 12, 2020, 09:26:59 pm
content: ? ?http://www.sm5bsz.com/pindiode.htmhttp://www.sm5bsz.com/linuxdsp/tx/safe/tx_control.htmDon't know if this is exactly what you need, but Leif the author of Linrad has a lot on his site about using PIN diodes for QSK.Recently its emerged that an 1n4007 could substitute for a PIN diode in many applications.Just poke around on his site, maybe you'll find something useful.http://www.sm5bsz.com/linuxdsp/rxhfa/rfamp_hfa.htm
Who know/ use "DIGTRX"? - Page 1
Forum section: electronics / rf-microwave

author: Lord of nothing
author_rank: Super Contributor
timestamp: August 20, 2020, 07:26:50 pm
content: HiI found some Videos that Cuban Number Station use that but beside of that I found no Video about.Does anyone use that? Is this the "official" Site for?https://www.qsl.net/py4zbz/hdsstv/HamDRM.htmThanks!
Microstrip High- and Low-Impedance Short-Line Sections - Page 1
Forum section: electronics / rf-microwave

author: promach
author_rank: Frequent Contributor
timestamp: July 29, 2019, 08:37:25 am
content: Expression 4.50 can be obtained by equating the ABCD parameters of the two circuits ?Could anyone advise ?Note: Screenshots below are taken fromMicrostrip Filters for RF Microwave Applications, 2nd Edition

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: July 29, 2019, 10:02:33 am
content: Quote from: promach on July 29, 2019, 08:37:25 amIt literally says that they can be obtained from the ABCD parameters.What you can try is look up is the following:How to go from a difference in impedance to ABCD parametersHow to go from lumped components to ABCD parametersHow to deal with electrical length in ABCD parametersAnd from what you learn about this, you should try and set up the ABCD parameters for both the situations and show equivalence.

author: promach
author_rank: Frequent Contributor
timestamp: July 30, 2019, 03:10:03 am
content: Now the question ishow to derive expression 4.50 given the following ABCD matrix ?I am still trying to derive the ABCD matrix for the following circuit configuration.Any help ?Edit : The derivation process could be found at page 25 of the pdf attachmentMicrowave_Network_Parameter.pdf(387.32 kB - downloaded 110 times.)

author: promach
author_rank: Frequent Contributor
timestamp: August 14, 2019, 07:02:38 am
content: The following is the derivation process for expression 4.50ABCD matrix for transmission line at Figure 4.7(a)ABCD matrix for π-circuit network at Figure 4.7(b)Comparing the two ABCD matrices above gives :Applying trigonometry double angle formula :

author: promach
author_rank: Frequent Contributor
timestamp: August 17, 2019, 03:40:11 pm
content: Ok, now to more detailed part:How to derive expressions (5.3) ?I suppose that this involves eliminating the assumption : ZC<< Z0<< ZLNote: In the post above, I have derived expression (5.2) for inductor, which is equivalent to expression (4.50)

author: promach
author_rank: Frequent Contributor
timestamp: August 09, 2020, 01:00:02 pm
content: The following is the derivation process for expression 4.52ABCD matrix for transmission line at Figure 4.8(a)ABCD matrix for T-circuit network at Figure 4.8(b)Comparing the two ABCD matrices above gives :Applying trigonometry double angle formula :

author: promach
author_rank: Frequent Contributor
timestamp: August 09, 2020, 01:05:02 pm
content: Summarizing the derivation result from reply #3 and reply #5 , we could derive equation (5.3) easily.However, what I do not understand is why the extra term for the inductor equation (5.3) is labeled as "shunt susceptance of the high-impedance line" ?If I am not wrong, the book might have a typo mistake and the correct version of the sentence should be as follows :The results of Eq. (5.2) do not take into account theseries reactance of the HIGH-impedance lineandshunt susceptance of the LOW-impedance lines.
DIY SDR EMF Field Strength meter - Page 1
Forum section: electronics / rf-microwave

author: DonnieBrodan
author_rank: Contributor
timestamp: August 16, 2020, 01:52:52 am
content: If I plug a $30 SDR with some antenna variety into an RPi, by viewing the the waterfall might I get an idea of EMF Field Strength? Further... produce code that does this automatically and plots a nice graph of EMF Field strength over time

author: 0culus
author_rank: Super Contributor
timestamp: August 16, 2020, 03:17:18 am
content: You will be able to do qualitative and relative measurements. It will not be calibrated, at all, so you won't be able to get any accurate absolute measurements. What field's strength are you trying to measure?

author: DonnieBrodan
author_rank: Contributor
timestamp: August 16, 2020, 06:46:54 am
content: just to measure radiation exposure in the environment, something similar to say TF2 Trifield Meter. Perhaps could find a suitable antenna. Could potentially calibrate it with some real gear.. lots of work.. one day..

author: wilhe_jo
author_rank: Regular Contributor
timestamp: August 23, 2020, 05:35:54 pm
content: EMF is a quite wide field and covers dc-300GHz...So, what kind of EMF are you interested in?73
what is this circuit - Page 1
Forum section: electronics / rf-microwave

author: jafal
author_rank: Contributor
timestamp: August 04, 2020, 10:29:35 am
content: hiwhat is this circuit and how its work ??the 555 timer not shown but it is run in Relaxation modthe circuit was in laser rangefinder

author: jafal
author_rank: Contributor
timestamp: August 04, 2020, 10:51:53 am
content: hithis is the 555 connected to transistor base

author: ArthurDent
author_rank: Super Contributor
timestamp: August 04, 2020, 01:59:37 pm
content: Possibly a way to add modulation to the beam. Google indicates this is a way to measure distances in a laser rangefinder.
Derivation of DFT equation for BASEBAND 2FSK - Page 1
Forum section: electronics / rf-microwave

author: Ralphy007
author_rank: Contributor
timestamp: August 03, 2020, 09:08:45 am
content: The attachment shows my attempt at deriving the dft equation for baseband 2FSK.Although the equation I have derived is not correct, I believe its not far away.I have already done it for time periods Tb and 2Tb, were Tb is the bit period, and the equations seem correct.The attached file is for 3Tb, which I am having difficulty with.If you read the attachment it will be obvious I am not a mathematician as I have made some uniformed assumptions in an effort to get the correct answer.By the way I have been using SIMULINK to test/prove my theory.Many thanks
Dual zone microwave sensor, car alarm - Page 1
Forum section: electronics / rf-microwave

author: afm
author_rank: Newbie
timestamp: August 02, 2020, 05:38:27 pm
content: Hello, I would like to know how this sensor kit works.I have an alarm with this type of sensor, but it is not dual zone, I would like to know how it works with dual zone, with adjustment "inside the vehicle and outside" and if it is better than mine.I know how the sensor works in my alarm! I don't know how this works.How does the sensor work inside the vehicle?How does the sensor work outside the vehicle?https://www.ebay.com/itm/New-DUAL-ZONE-PROXIMITY-SENSOR-for-any-bike-car-alarm/400350832159?hash=item5d36c4e61f:g:SX0AAOSwEetV-WYkThank you.
GPS Dead Reckoning  - Page 1
Forum section: electronics / rf-microwave

author: thelearner
author_rank: Contributor
timestamp: July 29, 2020, 04:00:17 am
content: Hello,I want a GPS module that can work indoor and outdoor also. Then i came up with dead reckoning type GPS modules, but there are many modules that support dead reckoning. So is there any parameter through which i can differentiate the performance of the dead reckoning of the modules.TIARegards,thelearner

author: cdev
author_rank: Super Contributor
timestamp: August 02, 2020, 02:57:04 am
content: There are a lot of papers on Google Scholar. Typically DR involves linking an IMU and possibly a digitak compasss to a high accuracy RTK gps. But the longer it is since you last GPS fix the residual error adds up. Still they can be fairly good. Most recently visual slam is incorporating visual clues in the solution. Extebnsive databases of landmarks can be built up in memory and SIFT used to determine from the environments geometry where a robot is. The science of indoor navigation and mapping is becoming better very quickly. The more imputs your robot has the better. RGBD sensors give you images plus depth. very useful.
RF Monitor Circuits - How Do They Work? - Page 1
Forum section: electronics / rf-microwave

author: Dan_CA
author_rank: Contributor
timestamp: July 28, 2020, 08:24:35 pm
content: I have been working on a Metcal soldering station, which is basically a 40W13.56 MHz generator. At the RF output there is the following circuit:The function of the circuit is to sense an open output and turn on the transistor. If the output load is mismatched (but not open) the transistor remains off. It does work, but my attempts to model it in LTspice do not.In my internet searches I came across a very similar circuit from a DIY Metcal build based on Metcal MX-5000. It's on a Russian website athttps://habr.com/en/post/451246/. The author says that he copied the circuit from the Metcal. I extracted the relevant part of the circuit.The function is to sense when the load changes from about 50 Ohms to a mostly capacitive load when the soldering tip heats up. My spice simulation does seem to work with this one.My question is how do these circuits really work? I first thought that they were a Bruene directional coupler (much info on the net), but the circuit configuration is not right. Also there is not directional coupler action for resistive loads. The fact that the secondaries are shorted by the diodes is puzzling.Has anyone seen circuits like this or do they have any insight? I guess it's just my compulsive desire to figure things out. Thanks for reading.
JLCPCB dielectric constant - Page 1
Forum section: electronics / rf-microwave

author: veeti
author_rank: Contributor
timestamp: July 28, 2020, 03:27:11 pm
content: HelloHave people used JLCPCB for 6Ghz designs? I have understood that fr4 dk changes quite much over freq range. But they don’t offer anything else. I contact them but i only got FR-4 dk @ 1MHz for response.Or does someone have good alternative place to suggest - i only have used OSHPark.br. Veeti

author: eb4fbz
author_rank: Regular Contributor
timestamp: July 31, 2020, 07:42:33 pm
content: FR4 Er not only changes with frequency, but also between manufacturers and batches. FR4 is just Flame Retardant type 4, which means it's a laminate made of woven glass reinforced epoxy resin. What weave design? How much epoxy? How much glass fiber? Who knows!At high frequency, the losses are high and the weave makes the Er not constant along the surface. Better ask for 7628 and avoid 106 or 1080 weaves.There are some better "premium" FR4 type laminates for RF. But your stackup must use cores on the RF layers instead of prepeg. RF layers are commonly routed on outer layers, and 4 layer boards are usually made of one core and two prepegs. You would have to use a 2 or 6 layer PCB, or order a custom stackup to have advantage of these laminates.You can ask for controlled impedance too, but cost increases, and the high loss tangent is unavoidable. For certain applications it's sort of ok for 50ohm lines up to 6GHz, but forget about microstrip filters or impedance matchings.

author: bd139
author_rank: Super Contributor
timestamp: July 31, 2020, 08:35:47 pm
content: PCBway will do Rogers laminate which has better defined microwave characteristics. I’ve never played with it though (yet)
What is the best way to learn SDR?  - Page 1
Forum section: electronics / rf-microwave

author: thelearner
author_rank: Contributor
timestamp: July 30, 2020, 03:07:06 pm
content: Hello,I want to learn software defined radio. I have hackRF one with me. I am searching for resources that can teach me SDR.Can you suggest any best way to learn SDR and resources to learn SDR.TIARegards,Thelearner

author: bob91343
author_rank: Super Contributor
timestamp: July 30, 2020, 08:27:32 pm
content: I suggest joining the groups.io SDR forum. Lots of knowledgeable people there, eager to help.

author: radiolistener
author_rank: Super Contributor
timestamp: July 30, 2020, 10:02:25 pm
content: You can start from learning how analog radio works.SDR works almost the same as analog radio but operations are performed in digital domain and it allows to perform it more better.I can suggest you this book:JOY LASKAR "MODERN RECEIVER FRONT-ENDS Systems, Circuits, and Integration"
DSP Geometric series - Page 1
Forum section: electronics / rf-microwave

author: Ralphy007
author_rank: Contributor
timestamp: July 27, 2020, 12:03:53 pm
content: Hi just wondering ifN N/3∑ y(n) * e-J2πfn = ∑ y(n) * e-J2πfn } ?(2*N/3) 0

author: Nominal Animal
author_rank: Super Contributor
timestamp: July 27, 2020, 01:58:47 pm
content: Do you mean, if$$\sum_{n=0}^{N/3} y_n e^{-2 i \pi n f} = \sum_{n = 2 N / 3}^{N} y_n e^{-2 i \pi n f}$$or, in other words, if the Fourier series sum at \$f\$ has symmetric contributions from \$n = 0 \dots N/3\$ and \$n = 2N/3 \dots N\$?The answer is generallyno. (There are some specific configurations of \$y_n\$ for which it is true, but they tend to be uninteresting.)
hugens new  - Page 1
Forum section: electronics / rf-microwave

author: m3vuv
author_rank: Super Contributor
timestamp: July 27, 2020, 09:53:59 am
content: just a heads up folks,the guys who put together the nanovna have brought out a mini spectrum analyser (rectum paralyser along the same lines as the nanovna,,have a look at nanovna users.org,73 m3vuv.
Need filter simulation program for Linux - Page 1
Forum section: electronics / rf-microwave

author: cdev
author_rank: Super Contributor
timestamp: July 26, 2020, 10:33:31 pm
content: Hello, for a long time Ive been looking for a program that I can use to design different kinds of RF filters on Limux. Low pass filters, high pass filters, band pass filters and band stop filters. My usual go-to program is RFSim99 but the program is ancient and recently my Wine installation broke and I am in dependency hell and really need to find something newer and better, or get RFSim99 working again. Is there anything that compares to RFSim99?It seems to me that qucs may have the features I need? At some point I had it installed on my machine but something broke it. it may only be available in Debian unstabble, if so if its good I can install it, probably. Would qucs do what I use RFSim99 for? I really need that capability again.Old and clunky as it is that program is super useful and at this point I am familiar with its limitations so get pretty decent use out of it.----Update, qucs does filter design, although I still prefer RFSim99 I may warm to qucs as I learn more about it.It will do for now.

author: profdc9
author_rank: Frequent Contributor
timestamp: July 27, 2020, 12:58:07 pm
content: I have used qucs, and more recently, qucs-S (qucs with ngspice) for simulations and it is quite a nice program. The harmonic balance needs work, but for linear simulations it should be more than adequate. It won't do filter design though.
Pse help with Yagi design (647MHz, 7% bandwidth, low gain) - Page 1
Forum section: electronics / rf-microwave

author: Yansi
author_rank: Super Contributor
timestamp: July 26, 2020, 10:49:04 am
content: Hello,I have a specific application, that would benefit from replacing an OEM receiver antenna (if you can call the thing as such) with something lil better to improve the range a bit.It is a receiver, centered on 647 MHz, requiring 42 Mhz operating bandwidth (6.5% relative bandwidth).What I had in mind was to design a 4 element (ref-rad-dir-dir) Yagi-Uda antenna with a square cross section boom (such as 15x15mm) and the elements coming through the boom, electrically connected with it (adds significant durability to the thing). What I think it would benefit from is using an open dipole radiator with < 50ohm impedance (such as 28 or 12.5 ohm) due to apparently much easier matching using a simple 1/4 lambda coaxial transformer (receiver is 50 ohm input).Folded dipole is complicated for manufacturing (not easy to achieve tolerances) and not easy to mount.I am no antenna expert by any means, but I can access a VNA to get a proper validation of the resulting design and probably even try to measure if there is any directionality/gain using another antenna as a reference.So much for what I (think) I need and how I think it should be approached.What I lack is the knowledge where to obtain design data. If there is any "simple" (I know it is never that simple) calculator tool for this or not. There is not any exact directivity or gain goals to be met, so if the result will be little or less off from the ideal result won't likely matter. I just want to try improving at least a bit on the OEM "rubber whip" antenna, that just sucks.What are your opinions and/or recommendations?Of course I could buy a good off-the-shelf antenna for this, but I need to relieve a bit of stress in a machine shop playing with some shiny aluminium metal.But on a serious note - how to design it or at least obtain some baseline design data to stat off of?There are tons of HAM radio band yagi designs out there to copy, but this one is quite "special".ThanksY

author: Yansi
author_rank: Super Contributor
timestamp: July 26, 2020, 11:29:24 am
content: Or maybe just a stupid question, but how well do yagi designs scale? If I take for example design one like this:https://www.qsl.net/dk7zb/70cm/4.htmand scale it properly from 432 to 647 MHz, will it work? I guess so. Of course, one would need to make it a bit bigger to be able to fine-tune. But, is this approach even possible?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: July 27, 2020, 12:33:15 am
content: Correct, the fields don't care, scale everything proportionally (diameter/width/thickness included!) and you get the same impedance and percent bandwidth.Tim
Difference between Amphenol RFX series and non - Page 1
Forum section: electronics / rf-microwave

author: tkamiya
author_rank: Super Contributor
timestamp: July 25, 2020, 05:32:10 pm
content: I always wondered about this, and I am about to buy BNC in bulk quantity. I prefer Amphenol as I always had good luck with its products.Amphenol seems to be divided into different sub-companies and they all make similar connectors. For example, BNC. There are parts like 31-320 and 31-320RFX for example. There are many other examples like this across all RF connector types, yet the differences are unclear. Prices seem to vary quite a bit. Does anyone know how they are distinguished?https://www.digikey.com/products/en/connectors-interconnects/coaxial-connectors-rf/437?k=bnc&k=&pkeyword=bnc&sv=0&pv31=334919&pv31=334949&pv31=405002&pv1652=330651&pv1652=334919&sf=1&FV=-1%7C115%2C-1%7C1946%2C60%7C238650%2C69%7C349292%2C518%7C318854%2C801%7C320955%2C1989%7C0%2Cmu4GHz%7C2157%2C-8%7C437%2C28%7C387942%2C1401%7C402831&quantity=&ColumnSort=0&page=1&pageSize=25

author: TimFox
author_rank: Super Contributor
timestamp: July 25, 2020, 08:55:46 pm
content: The "RFX" connectors are not guaranteed over the full military frequency range specified for BNCs, but are adequate for most test-equipment purposes. The RFX metal shells can be die-cast.

author: tkamiya
author_rank: Super Contributor
timestamp: July 26, 2020, 02:11:56 am
content: Thank you. I guess one is consumer/industrial and the other is MIL. I wish Amphenol made that clear. Prices explain well though, there got to be something quite different among them.
TX/RX switching and transmitter finals damage - Page 1
Forum section: electronics / rf-microwave

author: profdc9
author_rank: Frequent Contributor
timestamp: July 03, 2020, 02:30:17 pm
content: I would like to design a device that would rapidly switch between a TX and RX antenna. I would prefer to support both a keying output from a transceiver as well as autodetection of TX power to switch over for those transceiver who for some reason can not supply a keying output.Naturally, there is some delay from when the keying signal is grounded and power is delivered by the transmitter. This presents the possibility of both hot switching a TX/RX relay as well as the transceiver briefly delivering power to a badly mismatched load.How is this presented in practice? There is usually some kind of sequencer. My ICOM 7300 has a selectable TX delay of 10, 15, or 20 ms. Is this a common feature on transceivers one can usually depend on to prevent hot switching? Or is the ICOM 7300 an exception in this regard?Does such a sequencing basically prevent effective QSK operation because it can not switch rapidly enough between TX and RX?Is it possible to design a device that keys off of transmitted power quickly enough so that as the transmitted power ramps up, the amount of power being reflected is small during the time the hot switching occurs? Do most transceivers transmit full power in only a millisecond or so or does the power ramp up, say on a CW transmit, over many milliseconds?

author: shved
author_rank: Regular Contributor
timestamp: July 22, 2020, 08:37:01 pm
content: Try looking at some old CB Italian linear amps. They used to include loads of amp activation options. External trigger(ptt line on the radio), "VOX" automatic mode, and manual "tune" mode.
Steam Link Teardown Question (RF?) - Page 1
Forum section: electronics / rf-microwave

author: henrylucken
author_rank: Newbie
timestamp: July 20, 2020, 04:13:48 pm
content: Hey everyone!In the image attached,1. What is the purpose of the square pads next to the stamped metal antenna?2. What is the purpose of the copper slot?

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: July 21, 2020, 08:02:38 am
content: Could you get a picture of the slot on the other side? I wonder if there is something connecting to it to have it radiate as a slot antenna, or something similar.The squares - I don't know honestly. Only thing I can think of, but seems very unlikely in this situation, is some kind of tuned loading structure to load the antenna next to it depending on manufacturing or similar?

author: KE5FX
author_rank: Super Contributor
timestamp: July 21, 2020, 08:48:25 am
content: That appears to be a variation on thegamma matchtheme.

author: radiolistener
author_rank: Super Contributor
timestamp: July 21, 2020, 07:37:39 pm
content: Quote from: henrylucken on July 20, 2020, 04:13:48 pmprobably it is reserved to solder matching network with SMD inductors and capacitors, for antenna with different impedance... For example if manufacturer will needs to use different type of antenna in future
Are there any online resources available to make my own signal jammer? - Page 1
Forum section: electronics / rf-microwave

author: novicefedora
author_rank: Contributor
timestamp: July 28, 2020, 02:33:28 am
content: Are there any online resources available to make my own signal jammer?I want to be able to set a custom frequency.I looked at Wave Bubble but it seems to be outdated requiring components which are hard to procure.

author: ataradov
author_rank: Super Contributor
timestamp: July 28, 2020, 05:12:09 am
content: That would be very illegal, even in India. So don't do it, or at least don't ask about it on public forums.

author: tggzzz
author_rank: Super Contributor
timestamp: July 30, 2020, 11:05:58 am
content: The OP has taken that advice, sort of...https://www.eevblog.com/forum/chat/will-going-through-undergraduate-textbooks-allow-me-to-design-my-devices/msg3164580/#msg3164580

author: cdev
author_rank: Super Contributor
timestamp: July 30, 2020, 06:32:32 pm
content: Don't jam, period.Live and let live.

author: ataradov
author_rank: Super Contributor
timestamp: July 30, 2020, 06:33:22 pm
content: OP seems to have some mental issue. He is not likely to build anything working, so it is fine.
German Weather Balloon Teardown, Vaisala RS41-SGP Radiosonde/Probe - Page 1
Forum section: electronics / rf-microwave

author: madsbarnkob
author_rank: Frequent Contributor
timestamp: July 18, 2020, 12:11:42 pm
content: During my vacation at the island of Langeland, Denmark, I found a washed up radioprobe from a German weather balloon on the beach. It is a Vaisala RS41-SGP single use instrument in a styrofoam enclosure that can measure air temperature, humidity, pressure, speed and direction. It uses a STM32F100 microcontroller as the heart of the unit, has a UBLOX UG8010 GPS chip and a RPM411 barometric add-on board.Not a part of the video, but it has a Si4032 ISM transmitter for the 400 MHz band:https://www.silabs.com/documents/public/data-sheets/Si4030-31-32.pdf

author: radar_macgyver
author_rank: Frequent Contributor
timestamp: July 19, 2020, 08:16:50 pm
content: The spiral is an near-field communications antenna, prior to launching a sonde, one must initialize it by placing it on an NFC pad that talks to the ground station, sets the tx frequency, calibrates the sensors, etc. The wire antenna below is for telemetry back to the ground station. The data collected is plotted on aSkew-T diagram, which is one of the strangest plots I've ever seen.

author: cdev
author_rank: Super Contributor
timestamp: July 20, 2020, 04:32:09 pm
content: Their radiosondes used to contain a high quality GPS quadrifilar helix antenna. I guess they no longer do.

author: TheMG
author_rank: Frequent Contributor
timestamp: July 21, 2020, 03:49:51 am
content: Quote from: cdev on July 20, 2020, 04:32:09 pmNo need for it anymore. These newer GPS chips have much better sensitivity and can offer the same or better performance with simpler, less expensive PCB antennas, not unlike what you'd find in modern smartphones.
Need help indentify this Russian/Soviet RF connector - Page 1
Forum section: electronics / rf-microwave

author: electronicsguru222333
author_rank: Newbie
timestamp: July 20, 2020, 02:54:55 pm
content: Hi,I’m working on this project with Russian/Soviet RF connector as I list in attach files.To anyone who knew, please help me identify this connector.Thanks in advance!

author: radiogeek381
author_rank: Regular Contributor
timestamp: July 20, 2020, 03:23:25 pm
content: How close is it to a TNC?

author: cdev
author_rank: Super Contributor
timestamp: July 20, 2020, 04:28:46 pm
content: I am looking at a TNC. Your connector is not a TNC.TNC male looks almost identical to a BNC except it screws on, it does not lock on with a spring lock. It has a sharp machined pin with a conical tip, like a BNC.

author: khach
author_rank: Contributor
timestamp: July 20, 2020, 07:56:46 pm
content: Check dimension. Possible this is very old obsolete connector from GOST 20265-74

author: electronicsguru222333
author_rank: Newbie
timestamp: July 21, 2020, 12:16:18 am
content: Quote from: khach on July 20, 2020, 07:56:46 pmThank you, sir. This standard totally matches my connector dimension!

author: vk6zgo
author_rank: Super Contributor
timestamp: July 21, 2020, 01:32:12 am
content: It is quite large from the pix & spec sheet, & looks a lot like a Chinese L27 connector.The latter are available from the PRC, but are not cheap.
MOVED: Source of good, but cheap RF coaxial cable connectors, like SMA, N, BNC, etc - Page 1
Forum section: electronics / rf-microwave

author: cdev
author_rank: Super Contributor
timestamp: July 20, 2020, 07:39:24 pm
content: This topic has been moved toBuy/Sell/Wanted.https://www.eevblog.com/forum/index.php?topic=247770.0because its more appropriate there.
Need high permeability at high frequency torroids for common mode choking - Page 1
Forum section: electronics / rf-microwave

author: ocset
author_rank: Super Contributor
timestamp: July 19, 2020, 12:21:01 pm
content: Hi,We have a comms system noise problem. The comms doesnt work when the SMPS PSUs are working. Therefore We wish to thread signal and power cables through torroids to reduce noise. But most ferrite torroids have almost unity relative permeability at 10MHz and above. Do you know of any better ferrite torroid materials for the higher MHz frequencies?Also, i appreciate that the location of the torroid along the cable will make a difference.Also, i appreciate that the position of the "grounding" wire which connects circuit ground to the outer metal chassis will affect EMC performance. We have common mode chokes and diff mode filters on the board, but still noise is whipping us.

author: ignilux
author_rank: Unknown
timestamp: July 19, 2020, 08:07:59 pm
content: Fair-rite's61 materialgoes at least an order of magnitude higher in frequency before it hits unity relative permeability.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: July 19, 2020, 10:26:28 pm
content: "Most" ferrites of what type?I see hundreds of options with substantial added impedance at 100MHz and above.Tim

author: A.Z.
author_rank: Super Contributor
timestamp: July 21, 2020, 03:18:25 pm
content: Quote from: ignilux on July 19, 2020, 08:07:59 pmwhat about #31 ?https://www.fair-rite.com/31-material-data-sheet/https://palomar-engineers.com/ferrite-products/ferrite-cores/ferrite-mix-selection
RF antenna design - Multiple antennas on one PCB - Page 1
Forum section: electronics / rf-microwave

author: NW27
author_rank: Regular Contributor
timestamp: July 17, 2020, 02:56:14 am
content: Hi All,I need to make a low (<20mm) profile antenna array that is extremely rugged and can handle multiple feeds.Basically I have three separate RF circuits:- Telstra GSM band 28 (700MHz) and B3 (1800MHz). This is a transmitter & receiver.- WiFi @2.4GHz. General purpose for connection to a WiFi network.- GPS signal reception. This appears to be L1 @ (1575.42MHz) & L2 (1227.60MHz).I would like to make one physical antenna block that houses the three antenna's.I picture the block as being say the size of an A5 sheet of paper and 20mm thick. This could then be placed on top of a vehicle roof or similar.I was thinking of taking the three aerial leads from the RF equipment, up in a common flexible but rugged conduit (approximately 2m) and into the under side of the block.These three cables would then individually connect to each of there respective antenna's.I was thinking of just laying out the antenna's on a PCB e.g. 3 * Inverted-F antenna shape.I refer to it as a block because ideally the PCB and incoming aerial leads would be fully encapsulated?Thoughts?Thanks,Neil.

author: geggi1
author_rank: Frequent Contributor
timestamp: July 17, 2020, 08:06:30 pm
content: Have a look into patch antennas.

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: July 18, 2020, 08:54:14 am
content: Do you want it to be omnidirectional? If so, patch antennas could be annoying since they tend to have some (though not a lot of) gain. Do you have access to tools to simulate the performance? 3D EM solvers?Just make sure not to underestimate the impact of your case. You can't just slap on some antenna from a datasheet, put it in a box, and expect good performance.
No more PL on local 2m repeater - Page 1
Forum section: electronics / rf-microwave

author: CaptDon
author_rank: Super Contributor
timestamp: July 14, 2020, 02:09:37 pm
content: Our local 2 meter repeater owned by the local clubwas of course originally PL'ed at 123hz. The repeaterwas being brought up by users of another repeaterabout 50 miles away on same frequency and samePL tone. Our group (I am no longer a member)decided to drop the PL entirely and go DCS only.What a sad decision!!! So all of the older really niceall-mode units and a lot of the older mobile equipmentthat was connected as battery powered stand-byemergency base station equipment instantly becameobsolete on the repeater due to no 'DCS' feature.This was an already under-utilized repeater whichsuddenly became even more useless unless youowned one of the Chinese ButtFag handy-talkieslike the 'push button commandos' use aroundthe hamfests and such. I begged them "Just switchthe PL tone and that will eliminate the ker-chunkingfrom the distant repeater guys". No dice!! So nowa club of 30+ people is down to about 10 max becausethe guys with the older nice base station type equipmentwon't support a 'repeater club' that took away thePL access feature. Have any of you 'Old Phartz' alsofelt alienated by moves like this??? I have beenlicensed since 1973 and I know technology movesalong but why remove PL, why not have both???

author: vk6zgo
author_rank: Super Contributor
timestamp: July 16, 2020, 03:19:50 am
content: It sounds like using a sledgehammer to squash a bug!I haven't heard anything about it in VK6, but luckily, most of our repeaters are far enough apart that it isn't a major problem, so most don't even use CTCSS(PL).The Perth 10m & 6m repeaters do, & some 70cm ones, but 2m is pretty much free of such things.We get major ducting events along the West coast, & slightly less so from the Eastern States.Often the first inkling of such an event is when a distant station keys up a local repeater.We, understandably, are sparing in our use of CTCSS!OK, I suppose a distant station with a modern rig could set it up with the right CTCSS or DCS signal, but, as you pointed out in your case, that makes a lot of older equipment unuseable.Home brewing a single frequency CTCSS tone source for my "vintage" rig is one thing, making or buying one with multiple tones, plus wedging it into my radio is something altogether different.From my reading, I would have to redesign my FM modulator to allow me to use DCS.I am quite sure, though some "bright spark" in VK6 will decide DCS is a wonderful idea & want to implement it here.If they want to do digital signalling, they can do it to their heart's delight on "D Star" & the like, & keep their hands off our analog repeaters.What's more, they can "Get off my lawn!"
Tuning of helical antenna - Page 1
Forum section: electronics / rf-microwave

author: thelearner
author_rank: Contributor
timestamp: July 15, 2020, 06:54:50 am
content: Hello,I am using a SAM R34 based LoRa module. I want to use a helical antenna for my application. The antenna that I procured doesn't have 50 Ohm impedance at 865MHz. So I need to tune it to 865MHz. How can I tune it have 50Ohm at 865MHz? In the module, they didn't give a PI matching circuit for antenna tuning. So is there any way to tune helical antenna without a matching circuit?Can i use the NanoVNA for this antenna tuning?Regards,learner

author: cdev
author_rank: Super Contributor
timestamp: July 15, 2020, 10:24:50 pm
content: Yes, you definitely could use most of the newer iterations of nanovna especially the saa2 to get a good impedance match although I would if I was going to try to do that I would put the antenna on a dummy PCB - an approximation of the PCB, because I don't know how the nanovna would interact with the real PCB. But you could definitely use it to tweak the tuning, you should ask the manufacturer what the design recommends as far as orientation and ground plane (if applicable) They probably have application notes dealing with it. The antenna doesnt necessarily have to be 50 ohms, low power devices may not even be optimally 50 ohm.
SSA3032X, DSA832E-TG - Comments? - Page 1
Forum section: electronics / rf-microwave

author: ridgerunnersjw
author_rank: Contributor
timestamp: July 14, 2020, 07:37:53 pm
content: All....Looking to purchase my first spectrum analyzer....Want to use it for IoT development work.After much deliberation (cost, value, etc.) I seem to be leaning pretty heavily towards the SSA3032X or the DSA832E-TG.I would love to hear comments, recommendations and gotcha's to look out for?Thanks
Need help bad fuse ATMEGA32A-AU - Page 1
Forum section: electronics / rf-microwave

author: awehh
author_rank: Newbie
timestamp: July 19, 2020, 06:01:30 pm
content: Hello.Any one can solve this problems.dead DDS VFO,wrong fuse setting.is ATMEGA32A-AU SMD and Si5351 chip with 27mhz X-tal on itfirst time it works, but sometimes its shows 8888888 and distortion. i just save the hex.with AVR burner,and re-flash it but it dead.now i lost the hex files,and no eeprom.i try to contact the seller but they ignore it.i just need new Eeprom and hex if available.Hope any one can help..Many thanks
SDR based on GPUs - Page 1
Forum section: electronics / rf-microwave

author: rakeshm55
author_rank: Regular Contributor
timestamp: July 11, 2020, 08:58:53 am
content: I have some experience in working with FPGA + GPP +DSP based SDRs.I plan to try out GPU based SDRs and check its performance. I want to eliminate porting signal processing algorithms to FPGA (development process is painful) and use it for mere data acquisition , down conversion ,up conversion etc and allow signal processing to be offloaded to GPU. I am looking for real time performance. Not sure how suitable these processing nodes are for SDR.In order to create a test bed I plan to connect USRP to Jetson TX2 and bench mark the performance.Which interface I should use for this USB or ethernet?? I guess this interface should be high throughput interface (both direction) ?? Is there any examples for this??UHD driver once installed in Jetson can I not use it to access data from USRP to Jetson.Is there any example designs for Interfacing audio codec to Jetson ??

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: July 11, 2020, 11:58:36 am
content: What kind of application are you targeting?I guess ethernet can be faster (10 GbE ethernet).

author: radiolistener
author_rank: Super Contributor
timestamp: July 11, 2020, 01:07:34 pm
content: USB interface has less noise interference than ethernet, so it's better for SDR receiver.So, I suggest to use USB 3.0, it supports up to 5 Gbit/s.But ethernet solution may be more easy, because you're don't needs to deal with USB drivers.

author: rakeshm55
author_rank: Regular Contributor
timestamp: July 11, 2020, 04:28:24 pm
content: Quote from: radiolistener on July 11, 2020, 01:07:34 pmWont USRP have UHD drivers which once installed enable Linux systems (Jetson) to access USRP??....I have not used its USB ports before but this is my guess.

author: rakeshm55
author_rank: Regular Contributor
timestamp: July 11, 2020, 04:33:50 pm
content: Quote from: TheUnnamedNewbie on July 11, 2020, 11:58:36 amI am trying to create a test bed for GPU based SDRs. I intend to develop traditional waveforms (AM/FM types) and high end Waveforms (wimax) also ML based RF classification on it.
Dividing sensor network into multiple connections - Page 1
Forum section: electronics / rf-microwave

author: mrburnzie
author_rank: Regular Contributor
timestamp: July 10, 2020, 11:04:14 am
content: Hi everybody, I already posted this in the projects section, but got no reply. Maybe more luck with the RF guysI have a project where I have parking sensors on the streets. The streets are very dense and full of traffic.For now I'm using LoRaWAN to communicate with all the sensors. The gateways are on top of buildings.My requirement is to have a stable network that is of course also low power (>10 yrs). Till now the gateway price and position was always a negative thing when it comes to the LoRaWAN system, especially talking parking sensors. My idea is to divide the connections into two parts.The first part would be to change the sensors RF IC/module into something more generic (something like:https://datasheet.octopart.com/ADF7024BCPZ-Analog-Devices-datasheet-27843825.pdf) and the second part would be to create small gateways that are battery powered. The gateways would have the same RF IC/modules and an NB-Iot device that sends the data to the server (API).What are the thoughts on this?Also I found haystack, that mentions a lot of issues with LoRaWAN:https://medium.com/@patburns/announcing-haystacks-lorawan-replacement-program-1a72cb4cf201andthat is one of the reasons I want to skip LoRaWAN if possible. It is a great protocol (I don't want to offend the LoRaWAN fanboys), but I want to look at other solutions too.