hybridfree/eevblog-posts huggingface dataset:
How can I improve this LPF PCB Layout Design?  - Page 1
Forum section: electronics / rf-microwave

author: kml183
author_rank: Contributor
timestamp: February 26, 2023, 09:41:18 pm
content: Hello! Attached is the layout for a 7th order chebyshev LPF (150Mhz cutoff) that I am testing for a RF Transmitter. This is a 50 ohm line. I am using a coplanar stripline with a ground plane for the RF trace. This filter sits between the transmitter and antenna.I have a couple questions:- What could I do to improve the geometry of the ground pours on the top plane? Is there going to be a noticeable impedance difference because the ground pours are not rectangular? The shape of the ground pours was to give space between the centre and gnd terminals of the sma connector.- I designed this module so I can test its performance independently. If I had integrated this into a larger PCB with the transmitter, could I have added RF connectors in a way that would allow me to independently test this block without impacting the impedance matching?

author: kml183
author_rank: Contributor
timestamp: February 26, 2023, 09:42:01 pm
content: here is the 3D view

author: Bud
author_rank: Super Contributor
timestamp: February 26, 2023, 10:51:37 pm
content: Do not sweat for 150MHz.

author: Odysseus
author_rank: Regular Contributor
timestamp: February 27, 2023, 05:29:15 am
content: I'll agree that at 150MHz, I wouldn't worry about the transition. Can you provide the dimensions and Dk of your substrate and line geometry? Make sure you have at least modeled the SRF and Q of your passives. Assuming ideal Ls and Cs will give disappointing results. What is your transmitter power level? And any particular reason for the mix of 0603 and 0402 package sizes?

author: nctnico
author_rank: Super Contributor
timestamp: February 27, 2023, 01:50:46 pm
content: I'd make sure to move the vias as close to the capacitors as possible and have 2 vias per capacitor pad. For 150MHz it won't matter much but at a couple of hundred MHz it gets important.

author: yl3akb
author_rank: Regular Contributor
timestamp: February 27, 2023, 05:21:49 pm
content: Quote from: Bud on February 26, 2023, 10:51:37 pmIn case of only the passband thats would be true, but that being LPF, it may be required to attenuate up few GHz range (I dont know the application).One comment regarding the layout - do no use copper pour on TOP layer, but instead use two individal vias for each grounding point!But as already mentioned by others, check SRF of Your components because that wil dominate the performance in upper frequencies.
Printing from DosBox to PDF - Page 1
Forum section: electronics / rf-microwave

author: geggi1
author_rank: Frequent Contributor
timestamp: February 25, 2023, 07:33:55 pm
content: Hi!I'm putting the question in this section of the forum because it is HAM related.I have a IC-M710 that I'm running the programming software (EX1726) in Dosbox.There is probably a way to get printing to work but any descriptions I have found is a cryptic and I cant figure out how to set this up in the config file.Is there anybody here that can guide me in the right direction to get this working.

author: Co6aka
author_rank: Unknown
timestamp: February 27, 2023, 06:59:15 am
content: Suggestion:https://dosbox-x.com/Setting up printing in DOSBox-X:https://dosbox-x.com/wiki/Guide%3ASetting-up-printing-in-DOSBox%E2%80%90X
S11 and S22 parameters - Page 1
Forum section: electronics / rf-microwave

author: Nahim
author_rank: Contributor
timestamp: February 24, 2023, 09:34:58 am
content: For a powerful Gan transistor (100W) I calculate the matchingI received theS11 and S22 -12dBS21 -0,5dBFreq SPAN 500-2500MHzHow bad or good are the results? What consequences can appear?

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: February 24, 2023, 10:35:32 am
content: The idea that S11 and S22 must always be great (and under 'great' is usually understood <-10 dB) is a myth. It all depends on the situation and networks around the device you are discussing the S11/S22 of.In fact, demanding good S11/S22 when it is not in fact needed can lead to sub-optimal performance.Low-speed analog design usually has S11 = 0 dB or something, and I've never seen anyone complain about that.That said, in situations where it does matter, having bad S11 or S22 can result in standing waves, oscillations, suckouts, damaged components, poor performance, bad SNR, etc...

author: Nahim
author_rank: Contributor
timestamp: February 24, 2023, 12:16:22 pm
content: In fact, the parameter S21 is more important? Is it responsible for the loss of the signal?

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: February 24, 2023, 12:22:51 pm
content: I would say in amplifiers (and even some passive networks), S21 is often more important, but again, it depends on the situation.A classic example is a power amplifier, where it is not uncommon to sacrifice S22 and even S21 in order to improve the maximum output power and compression points.And then you haven't even started going down the rabithole of power/voltage/current gain, which are not the same if input and output impedance are not equal. For example, your transistor has an S21 that is less than 0 dB, ie, it seems to be worse than a wet noodle. But I suspect that might be because you are plotting it with 2 50 ohm ports, instead of actually matching the thing for gain or power.
Attenuator vs Termination? - Page 1
Forum section: electronics / rf-microwave

author: rfengg
author_rank: Regular Contributor
timestamp: February 23, 2023, 02:44:11 pm
content: Hi all,I need to test an amp at 10Ghz and rated for 20W output power.I am torn between deciding to go whether for a Attenuator or Termination (dummy load : 50ohms) .The load I was looking at is rated for DC-20GHz and 50W, while the attenuator is rated for DC-20GHz and 50W and has 50dB attenuation......both are around the same price.Am I right in assuming that the attenuator would be a better choice since I can hook it up to the amp and then monitor the output of the attenuator on a spectrum analyzer?If I use a load then I have no method of monitoring the power......any limitations in using a attenuator for this use case?Even if I leave the attenuator output end open, it should act like a reasonable dummy load with -100dB reflecting back to the amp?

author: xrunner
author_rank: Super Contributor
timestamp: February 23, 2023, 02:51:03 pm
content: Quote from: rfengg on February 23, 2023, 02:44:11 pmYou want the attenuator. The load will simply absorb all the power and you can't measure anything really. 20W is +43 dBm so the output of the 50 dB att. will be -7 dBm. You can then use a spectrum analyzer to check out the signal power and other parameters. Whatever power you measure with the spec analyzer will have to have 50 dBm added to it for the real power output of the unit. or you can probably tell the spec. analyzer to add it back in on a menu.

author: ejeffrey
author_rank: Super Contributor
timestamp: February 23, 2023, 05:38:07 pm
content: Quote from: rfengg on February 23, 2023, 02:44:11 pmCorrect. The return loss of a common attenuator or dummy load is rarely better than -30 dB (equivalent to VSWR ~ 1.06) anyway so a 20 dB or larger attenuator will normally have negligible degradation in matching even when the output is left open.

author: switchabl
author_rank: Frequent Contributor
timestamp: February 23, 2023, 06:02:24 pm
content: Quote from: rfengg on February 23, 2023, 02:44:11 pmThis is only the case if you assume that the attenuator is perfectly matched. It is true that leaving the termination open will not make a big difference at 50 dB attenuation. However I would not necessarily expect a power attenuator to have much better than 20 dB return loss at 10 GHz in the first place. Some are quite good (and some loads are quite bad), you will have to check the datasheet.If you go with the dummy load you will need an additional coupler for your measurements.
Interference Requirements for Homebrewed Transmitters  - Page 1
Forum section: electronics / rf-microwave

author: kml183
author_rank: Contributor
timestamp: February 22, 2023, 11:49:26 pm
content: I am just I am trying to find information about filtering requirements for harmonic interference for transmitters. I am located in north america.I want to design and build a LPF for my DRA818v radio module (https://www.tindie.com/products/dorji_com/ham-amateur-radio-module-dra818v/). I need to filter out the harmonic components on transmit for 144Mhz. I just don't know by how much!I have my ham license but unfortunately I don't have my study booklet. I can't find the regulation for this in the FCC guidelines. Any thoughts?

author: xrunner
author_rank: Super Contributor
timestamp: February 22, 2023, 11:57:10 pm
content: It's in Part 97, if I am understanding your question.§ 97.307 Emission standards.(e) The mean power of any spurious emission from a station transmitter or external RF power amplifier transmitting on a frequency between 30-225 MHz must be at least 60 dB below the mean power of the fundamental. For a transmitter having a mean power of 25 W or less, the mean power of any spurious emission supplied to the antenna transmission line must not exceed 25 µW and must be at least 40 dB below the mean power of the fundamental emission, but need not be reduced below the power of 10 µW. A transmitter built before April 15, 1977, or first marketed before January 1, 1978, is exempt from this requirement.

author: kml183
author_rank: Contributor
timestamp: February 23, 2023, 12:53:58 am
content: Awesome that is exactly what I was looking for! Thanks!
RF connector for Litz Wire Inductor - Page 1
Forum section: electronics / rf-microwave

author: jm_sanz
author_rank: Contributor
timestamp: February 22, 2023, 03:47:30 pm
content: Good afternoon folks,I am having some thermal issues with a connector for our PCB. The inductor frequency is around 2MHz, it istriangular and can reach from -20A to 20A. Right now we are using an standard Terminal Block (First Pic) like the one in the picture. Is it possible that the bad material and the little surface contact have a strong impact on the heating?. Would you have any recommendation of how to connect it without remaking the PCB?One possible solution I have thought of is in the second picture. Removing some pins of a RF connector an placing two of them (one for each current flow) and then crimp the litz into a male connector.Thank you in advance.

author: Ian.M
author_rank: Super Contributor
timestamp: February 22, 2023, 04:13:19 pm
content: Abusing RF crimp connectors isn't going to help.What current is the terminal block actually rated for?How are you preparing the Litz wire ends before inserting them in the terminal block?As Litz wire has individually insulated strands, you need to effectively strip that insulation and bond all the strands together when you terminate it. Normally one buys Litz wire with solder-through insulation so it can simply be tinned in a solder pot, but as solder is highly undesirable in a screw terminal, if you want to directly insert in in the terminal block, you are probably going to have to chemically strip it and crimp on a bootlace ferrule.Seehttps://www.newenglandwire.com/litz-wire-termination-guide/

author: TimFox
author_rank: Super Contributor
timestamp: February 22, 2023, 04:42:15 pm
content: There can be some confusion about the term "Litz wire".In the US, that usually means individually-insulated strands in a twisted wire, as in Ian.M's reply.The original German meaning of "Litzendraht" is just stranded wire, as in normal hook-up wire, without individually insulated strands.If your transformer uses the insulated Litz wire to reduce high-frequency resistance, it is mandatory to strip the strands at the termination, and the resulting fine stranded wire will be a problem in a screw terminal without a ferrule.Before solder-soluble insulation, the standard recipe was first to renew your fire insurance, then to heat the end of the wire in a Bunsen burner or alcohol lamp and plunge the heated end into an open container of alcohol.
1960's era CW Keyboard Magazine Article? - Page 1
Forum section: electronics / rf-microwave

author: rcbuck
author_rank: Frequent Contributor
timestamp: February 22, 2023, 01:10:06 am
content: OK, this is a long shot but will give it a try anyway.Back in 1969 I built a CW keyboard from a magazine article. I thought it was from a 73 magazine. I have looked at the indexes for 1967, 1968, and 1969 but didn't find the article. Maybe it was in CQ magazine but I can't be sure. CQ is not available online so I can't do any search of their back issues. I did see online where someone said CQ had a CW keyboard article in the September 1964 issue. That "could" be the one I am looking for. It is also possible that it was in a different year of 73. It probably wasn't in QST since I wasn't a member of ARRL back then.The thing I remember about the keyboard is it used some sort of magnetic cores to generated the code. There was a separate wire for each letter and number on the keyboard. There was a table in the article that told you which core number(s) to route each wire through for each character. If I remember correctly there were also a couple of RTL chips in the design.I'm just curious and want to read the original article to see what it was that I built back then. Maybe someone as old as me remembers the article.Today you would use a micro if you wanted a CW keyboard. I use a key with the transceiver keyer and am not interested in a keyboard to send CW.
Active inductor Design - Page 1
Forum section: electronics / rf-microwave

author: nq93
author_rank: Newbie
timestamp: February 20, 2023, 06:19:35 am
content: i am looking for a design of mH value Active-inductor using ads software. i have searched and tried gyrator circuit to get it but the maximum value is few nH. i could not find a circuit for mH value of active inductor. Could anyone guide me or share a link of the materials related to the topic.
Suggestions for 80 MHz VCO with fast tuning (>1 MHz -3dB bandwidth) - Page 1
Forum section: electronics / rf-microwave

author: dnadlinger
author_rank: Newbie
timestamp: February 17, 2023, 06:10:14 pm
content: Hi all,For a PLL-like application (laser stabilisation, with optical modulators in the loop), I am looking for an 80 MHz VCO with a high small-signal tuning bandwidth (at least a MHz or two). The absolute steady-state frequency range can be quite small, ±2 MHz or so would probably be enough.MiniCircuits used to have the ROS-… series, but apparently the low-frequency parts are all EOL now. Would anybody have any suggestions for alternative parts/manufacturers to look into?I suppose I could use a higher-frequency VCO and mix or divide it down, but that seems like unfortunate extra complexity. For much the same reason, I'd quite like to avoid designing my own Colpitts oscillator/… – I only need a few of these boards for internal research use, so the less RF design overhead, the better.Edit: It's quite possible that I'm asking the wrong question, as I've never looked into the internal topology of these commercial VCOs in much detail. One might imagine that the tuning bandwidth could effectively just be limited by how quickly the (RF-bypassed) internal tuning node can be driven.Thanks!— David

author: switchabl
author_rank: Frequent Contributor
timestamp: February 17, 2023, 07:17:11 pm
content: Crystek has some low frequency VCOs:https://www.crystek.com/home/vco/cvco.aspx?m=CVCO55CLModulation bandwidth is mostly determined by how fast you can drive the input capacitance of the tuning port.
Does this make sense as an AM RX - Page 1
Forum section: electronics / rf-microwave

author: MathWizard
author_rank: Super Contributor
timestamp: February 15, 2023, 05:30:54 am
content: I made a basic AM TX that's at 1.4MHz. I can hear in the kitchen pretty well, so now I'm improvising a RX. So I made a 270uH inductor, with a Q of 55. So 1st I just chained a 3 CE amp's together, and yeah it just amplifies everything, especially the strong 800kHz local station.And adding a few extra tank circuits didn't help much, so I tried a Sallen-Key type filter, by making a basic op-amp, with another the diff.pair like I used for the mixer in the TX.Now for the BJT's, I only chose the collector currents and Rbb's and haven't tried to calculate any closed or open loop gains. For the Sallen-key Q, I just chose 400kHz BW, and that gave a resistor divider gain of 3.5, but for now it's closer to 2.7, and plus I added a bypass cap. I'll try a smaller BW next time.And it oscillates a lot without the bypass cap. I guess it's a phase shift oscillator too. But I think it worked. Although it takes a lot of BJT's, and will need more yet, so maybe it's just not an economical way to do it.So there's just the antenna and tank, then with the circuit below without the bypass cap, then with it. My TX is the 1.4MHz signal. In ltspice I forgot 1 extra LC tank right after the 1st RF-amp
Vaguely interesting passive probe construction - Page 1
Forum section: electronics / rf-microwave

author: mblinov
author_rank: Contributor
timestamp: February 15, 2023, 01:37:46 am
content: Hi all,I've recently purchased one of those super-cheap passive probe sets that you canget on amazonfor £16 or so (I'm ripping them up for use as Z0 probes.)Since I had no need for the probe tip, I decided to do an extreme teardown. Ripping apart the aluminium enclosure, I find a PCB, with three resistors:- One 4.7Mohm,- One 4.3Mohm,- One 240 ohmI can visually tell that they are all wired in series. I do wonder why the manufacturer chose to use 3 separate resistors like this. Is the 240 ohm resistor footprint there to essentially play the role of a fine-grained adjustment resistor to get the total value as close as 9Mohm as possible?Pictures (open in new tab to see full size):

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 15, 2023, 05:12:47 am
content: Huh, PCB inside? I never did take mine apart... lemme see here, I've got a dead one laying around I think. Ah yeah, here we go.Ha, mine has 3 x 3M 0805 in it, clearly the superior voltage rating!Very similar design overall.And a 120R out in front. Note the traces going to the switch. This resistor is connected in 1x mode. In which the cable capacitance and resistance strongly attenuates the signal at high frequencies (these have a cutoff around 6MHz). The cable measures 130 ohms end to end (or something like that; it's an impressively small core that I can't even strip the end of without also chopping the wire itself!), and I don't know the Zo but it's probably somewhere around there.Anyways, in 10x mode, the small resistor out front does almost nothing; it doesn't affect the total, and the resistors are probably standard 1% so the 120 or 240 ohm difference is irrelevant. What it does do however, is set the high-frequency impedance and gain with respect to the compensation capacitor there. Not using it would result in ringing, or too low of a probe tip impedance.Another way to construct these probes is as a resistor divider at LF, capacitive divider at MF, and "low-Z" probe at HF. The equivalent circuit might look like this:Note that voltage distributes evenly along the divider chain at all frequencies, maximizing voltage rating. The divider capacitors are also large enough (hopefully?) to swamp "hook" (poles and zeroes in the MF range due to stray capacitance from midway along the chain to ground, or to surroundings if not shielded). And, this 100x example matches to a 50 ohm cable just fine so it doesn't need fancy-shmancy lossy mossy cable to work right.Basically, by the properties of the cable, some shortcuts can be made, greatly simplifying the tip end. The main downside is the cable itself has to be designed (or designed around, as you have no control over it once it's done), and the bandwidth at 1x is pretty awful.Tim
Cardioid loop #2 - Page 1
Forum section: electronics / rf-microwave

author: A.Z.
author_rank: Super Contributor
timestamp: February 28, 2023, 07:52:21 pm
content: maybe this is a shameless plug, but it's the result of a bunch of NEC simulations and field tests, which matched almost precisely them, the result is what we (I and my pard 13dka) named SULA (Small Unidirectional Loop Antenna)https://swling.net/viewtopic.php?t=55the antenna is a quite small receiving loop which shows a cardioid pattern from LW up to UHF (where the pattern is reversed); if one builds it "by the book", following the directions, it will be a surprise, while the loop is aimed at HF bands, it will go below and above; just FOLLOW the instructions and do NOT think it's another "magnetic loop", since it is NOT that, and won't work well if placed inside, give it a yard or a balcony, build it as designed and it will surprise you
Ubitx: what is the minimum I need to add? - Page 1
Forum section: electronics / rf-microwave

author: rthorntn
author_rank: Frequent Contributor
timestamp: February 13, 2023, 10:02:04 am
content: Hi,I'm getting ready to sit my foundation test, it's quite a bit to take in but it doesn't delve too much into actual hardware...I just got a ubitx, the full kit and I have a 13.8v toroidal PSU.So there is an antenna connector on the back, what would be the minimum cost parts I could pick up to get going, I just want the smallest and cheapest antenna I can get acceptable results with, what else do I need?I see mention of ATUs, do I need one, are there low cost units, also same question for SWR?Say I was interested in 40m, can I get a folding, somewhat portable antenna for messing about with initially?Just in case it helps I have a bunch of gadgets, is there anything here that's useful for improving my Ham setup:Raspberry PiNextion displaymoRPeus (not sure why I bought this)rtlsdrbladeRF (from their 2013 kickstarter)heaps of PC componentsI can also solder.Thanks for looking.CheersRichard

author: F4IUJ
author_rank: Newbie
timestamp: February 13, 2023, 03:22:52 pm
content: Hello,I have got bad news for you : it is all about the antennaI have good news for you : I operate with a length of speaker wire in the attic.You can start cheaply in many ways, for instance :a Endfed antenna resonnant on 40m (a roughly 20m long wire with 49:1 Unun), that should give you 40m, 20m, 15m and 10m band or if you have space resonnant on 80m (roughly 40m long wire). There are cheap unun kits on the internet, I've just bought one for 12€a doublet tuned with a Z-match : you buy speaker wire, separate the end in two, that is the antenna, the unseparated bit is the feeding line. Hang the antenna as high as you can then run the rest to of the wire to a balanced ATU, there are Z-match kit on the internet for little money as the Ubits is a QRP radioYou will need to add a bit of coaxial between your radio and the ATU or balun. You really want a small SWRmeter to avoid frying your finals by error and if you can afford it, buy a NanoVNA to fine tune your antennas.CheersYannig - F4IUJ
Simple Walkie Talkie project - Page 1
Forum section: electronics / rf-microwave

author: PamelaS
author_rank: Newbie
timestamp: February 17, 2023, 04:26:38 am
content: I am building two Walkie Talkies and I need some advice of mixers that are as good as SA612A which is out of stock. My plan is to use it with a 8MHz crystal oscillator. Thanks in advance

author: luiswen
author_rank: Newbie
timestamp: February 17, 2023, 11:45:23 am
content: is it SA612AD/01? i can find stock for you.

author: M0HZH
author_rank: Regular Contributor
timestamp: February 17, 2023, 02:06:28 pm
content: Default walkie-talkie choice for me would be the DRA818U module.SA612 is in stock ar RS:https://uk.rs-online.com/web/p/up-down-converter-mixer-circuits/1038044
CMU200 50Watt with B95 Option? - Page 1
Forum section: electronics / rf-microwave

author: chick0n
author_rank: Regular Contributor
timestamp: July 23, 2021, 11:38:43 pm
content: HiI own a cmu200 with option B95 (2nd generator). So I can only use the cmu with 2Watt input.Option B95 is Sandwiched to the RF-Frontend Board. I opened the Frontend, and there is a 50Watt 17dB attenuator placed. Also there is place for another one.Maybe it is possible to use the cmu with more than 2W input, when option B95 is disconnected/removed?Maybe someone with a 50Watt unit could make pictures of his frontend. To compare and see if a 2nd attenuator is placed?

author: xmo
author_rank: Regular Contributor
timestamp: July 24, 2021, 04:28:07 am
content: I think port RF1 has that attenuator so it can accept 50 watts whereas RF2 has no attenuator and can only handle 2 watts.Option CMU-U99/B99 deletes the attenuator and makes the range of RF1 and RF2 be the same.

author: chick0n
author_rank: Regular Contributor
timestamp: July 24, 2021, 02:36:39 pm
content: Quote from: xmo on July 24, 2021, 04:28:07 amBut every CMU200 with B95/96 has a Warning Sticker on Port RF1 and RF2 "Only 2 Watts". Mine too. Why?Maybe its just the cooling... The 50Watt frontend has a fat heatsink installed, and B95 Option has none.

author: xmo
author_rank: Regular Contributor
timestamp: July 25, 2021, 11:39:08 pm
content: You are probably right about the heatsink.I looked in the datasheet again and found that it does say you get reduced power with B95 so that accounts for the sticker.

author: Bravo
author_rank: Contributor
timestamp: August 26, 2022, 01:27:55 pm
content: You could use an external high power attenuator, & enter the +dB amount on the port 1 settings.

author: RBBVNL9
author_rank: Frequent Contributor
timestamp: February 10, 2023, 01:01:06 pm
content: Dear all,The maximum power level of the CMU200 is a topic that comes back in this forum every once in a while. Recently, I recorded a video that digs deeper into that topic (see below).Installing options B95 or B96 brings down the maximum power level of RF1 from +47 dBm (~50W) to +33 dBm (~2W). The technical reason is that the board of these options actually take the physical space where otherwise the heat sinks and fan are for cooling the shunt resistor of the 50W version. With these options, you get some more functionality at the price of less input power. Fine, that is a choice you can make.More intriguing is option CMU-U99/B99, titled "RF1 level range identical to RF2 option". As far as I can see, this 'option' is always a downgrade. You give up the 50W capability and get nothing in return. (Unless you have an automated setup where you need to switch between input channels that are both exactly –8 to +33 dBm ?!?). I find it strange to call this an 'option'..Anyway, here is the video:https://youtu.be/BtFvhvN3d8A
RF PCB partial mask reason ? - Page 1
Forum section: electronics / rf-microwave

author: fmkit
author_rank: Contributor
timestamp: February 05, 2023, 08:05:13 am
content: after googling for no avail. I'm asking here what is thr reason for having some areas of PCB unmasked ? I've designed PCB for myself and measured no difference in masked / no mask boards but keep seeing partial mask in commercial design.

author: TC
author_rank: Contributor
timestamp: February 05, 2023, 02:27:25 pm
content: Most likely to have better control over impedance. Solder mask as a dielectric constant between 3.5 and 4.0 (if I remember correctly). Effects will vary based on the solder mask thickness which isn't precisely controlled. Air has a dielectric constant of 1.0 (nominally).

author: yl3akb
author_rank: Regular Contributor
timestamp: February 05, 2023, 04:50:14 pm
content: At higher frequencies is may reduce the loss a little bit. See here Fig 3. for example:https://www.circuitinsight.com/pdf/effects_pcb_fabrication_high_frequency_electrical_performance_ipc.pdfIn practice its worth doing on some particular edge coupled microstrip structures such as directional couplers and band pass filters where material/medium between the edges is critical.

author: RoV
author_rank: Regular Contributor
timestamp: February 05, 2023, 05:52:04 pm
content: I think it's mostly done to limit losses. Besides, it allows some fine tuning (move/add capacitors, add a bit of silver paint somewhere), but this approach has almost disappeared, at least on production boards.

author: tchiwam
author_rank: Regular Contributor
timestamp: February 06, 2023, 05:42:24 pm
content: Then if you do ENIG it kind of negates the benefit as the ENIG is very rough on the surface. so you are often better off with the solder mask.Hard gold or ENEPIG is better but more expensive. best being bare copper, for a short while.Just this to say, YMMVIf you play under 2 or even 3GHz ... Meh don't worry too much.

author: ConKbot
author_rank: Super Contributor
timestamp: February 06, 2023, 11:07:55 pm
content: Quote from: tchiwam on February 06, 2023, 05:42:24 pmThat, and the gold is thin enough that for some (surprisingly high, but I forget off the top of my head) frequencies, the RF current will end up in the nickel plating.So from a pure loss perspective, not the best, but for consistency between board runs, no mask and using ENIG will at least be more consistent impedance/vswr wise than SMOBC, due to varying soldermask thickness or dK.Can you get hard gold mid-board like that? I'm used to card-edge fingers, which require the bus bar that gets used to electroplate them, but the bus bar gets routed away. Not saying it's not possible, just not familiar with it.
Bluetooth class 1 (100mW) causes severe Wi-Fi (802.11b/g/n) interference - Page 1
Forum section: electronics / rf-microwave

author: 2N2222A
author_rank: Regular Contributor
timestamp: February 13, 2023, 06:31:48 pm
content: Bluetooth is normally class 3 or 2, which is 1mW or 2.5mW @1MHz bandwidth. This fairly weak signal causes interference with Wi-Fi but only within the same house.Bluetooth is becoming more common. Class 1 operates at 100mW @1MHz bandwidth. Wi-Fi is typically 100mW @20Mhz bandwidth, which is the same as 5mW @1MHz. This means that Bluetooth class 1 is 20 times more powerful than Wi-Fi as far as interference is concerned. Wi-Fi cannot handle any narrow band interference, at least not the 11g OFDM modes. Many Wi-Fi devices today 2023 are operating in 1, 2, or 5.5mbps legacy 11b modes due to interference.A bluetooth class 1 device that is more than 4 times the distance between two Wi-Fi devices can significantly disrupt the Wi-Fi signal.Bluetooth frequency hops so frequently that long Wi-Fi frames (which is the result of lower bitrates) often get dropped. It doesn't matter what channel the Wi-Fi is on because Bluetooth frequency hops over all of them. Even 5% packet loss can render a network connection nearly useless. The default frame retransmission attempts for Wi-Fi is something like 7. Wi-Fi is also susceptible to strong signals operating on different frequencies. For instance a strong signal on channel 6 can interfere with wifi on channel 11 if the devices are fairly close together, usually less than 3 meters.I'm not even talking about 40Mhz 11n signals. That would be even worse!What can be done about this problem? If nothing, the at least there can be more awareness and our own devices can be switched away from class 1 if possible.
Hughes 889H Traveling Wave Tube (TWT) Amplifier - Page 1
Forum section: electronics / rf-microwave

author: graybeard
author_rank: Frequent Contributor
timestamp: January 28, 2023, 11:41:22 pm
content: I picked up this Hughes at theW6TRW swap meettoday. The guy gave it to me for free after I spent $200 on attenuators, adapters, filters, amplifiers, and test cables.I can't find any information online about it. I hope someone on this forum might have some information. I was hoping to see if it works.Thanks . . . Chris

author: KE5FX
author_rank: Super Contributor
timestamp: January 29, 2023, 01:07:40 am
content: Try the WA1MBA microwave list. Some of the OTs on there have seen it all.

author: coppercone2
author_rank: Super Contributor
timestamp: February 01, 2023, 05:09:27 am
content: yeah they go in rackmount boxes, I was wondering how hard it is to get a replacement tube for that thing, looks like you found one.It is basically HV power supply with interlock (heat time) for tube and some monitoring. I noticed in general the voltage goes up when frequency goes up, that takes 2kV+Don't start it without a load and find the correct sequence of power. 2 min warm up time on the tube and then not sure if the other rails need to be sequenced.You have a 20W unit between 8-18GHz.I have a few of them, one of them has blown up electronics. I replaced the transistors and noticed every single diode in the power supply was cleaved in two.. A different unit had the main transformer smoke and blow a fuse.https://www.axiomtest.com/documents/models/Hughes%208010H%20Datasheet.pdf

author: graybeard
author_rank: Frequent Contributor
timestamp: February 02, 2023, 12:38:35 am
content: Quote from: coppercone2 on February 01, 2023, 05:09:27 amThank you. I foundthis copy of the manualthat shows the lead connections to the tube.I have a 2KV 20mA supply, which is not enough. I do not have a 8-16 GHz source (yet). I have an HP power meter frequency counter that work in that range.-

author: 0culus
author_rank: Super Contributor
timestamp: February 02, 2023, 03:07:20 am
content: I have an HP 495A TWT amp that has a 1W Watkins-Johnson TWT in it. As other posters mention, that 495A box is mostly just power supplies plus a cathode current meter. You'll want to do your research before bringing your TWT up to avoid destroying it. Also, if it is really capable of 20W, be careful of legal issues and safety. 20W of microwaves directed into your remaining eye via open waveguide won't do that eye any favors. That said, very cool find!
Wireless speakers for elderly (not Bluetooth) - Page 1
Forum section: electronics / rf-microwave

author: JoeyG
author_rank: Regular Contributor
timestamp: February 01, 2023, 12:05:54 am
content: Hearing loss is very common in elderly and most don't want a headset.When listening to a TV in groups (say nursing homes) the TV is not loud enough for all of them to hear.Bluetooth only works one speaker and pairing a management is needed.Rather than build it, have you come across a wireless system or modules with multiple wireless speakers.IE Buy it before build it.Surely in this situation there is already a solutuon - but my search haven't any sucess.What do you think?THanks in advance

author: JoeyG
author_rank: Regular Contributor
timestamp: February 01, 2023, 12:09:16 am
content: Oh, I did find one Bluetooth solution in concert modehttps://ww1.microchip.com/downloads/en/DeviceDoc/00003118B.pdf

author: edavid
author_rank: Super Contributor
timestamp: February 01, 2023, 12:48:40 am
content: Infrared and analog RF headphones are still available and are a good solution for this.
(Help need) 433.92MHz Remote controller strange issue - Page 1
Forum section: electronics / rf-microwave

author: BD1QMP
author_rank: Contributor
timestamp: January 22, 2023, 02:56:48 am
content: A small product use standard 433.92MHz Remote controller module from Taobao. The transmitter and receiver is in figure 1the reverse schematic drawn by myself, in figure 2 and figure3.More than 100 unite are installed in different sites. the sites room is lead shield.Normal case: push the transmitter button, the receiver will enable output, when release the button, the receiver will stop output.Only 2 sites have this issue.The issue is: push the transmitter button, the receiver will enable output, when release the button, the receiver will stop output. about 200-500ms later, the receiver will enable output again, and after about ~1s (it is random), the receiver stop output. It is easy to repeat the issue once per 3 times. I tried to turn off the transmitter power supply, the receiver has the same issue.I tried 4 units in that site, all the 4 units have same issue. when I take the products back, cannot repeat the issue.It is so strange!Can any one give me some advice for investigation?Thank you very much!DE BD1QMP" alt="" class="bbc_img" />" alt="" class="bbc_img" />" alt="" class="bbc_img" />

author: AFTORF
author_rank: Contributor
timestamp: January 27, 2023, 07:29:43 am
content: It's seems to be RFI. Did you check RF field with receiver or spectrum analyzer ?

author: BD1QMP
author_rank: Contributor
timestamp: February 02, 2023, 02:21:29 pm
content: Quote from: AFTORF on January 27, 2023, 07:29:43 amno，I didnot check it

author: AFTORF
author_rank: Contributor
timestamp: February 02, 2023, 10:50:36 pm
content: You said "more than 100 units installed" but you don't have any receiver or analyzer to hear or watch RF path between transmitter and receiver...
Looking for data: Herotek DT1812-121, Rf ("crystal") detector - Page 1
Forum section: electronics / rf-microwave

author: Uky
author_rank: Regular Contributor
timestamp: May 27, 2022, 04:13:42 pm
content: Greetings,Looking for datasheet for a RF detector, HEROTEK DT1812-121, p/n 01-004916-00.It is supposed to be a negative out RF detector diode with a frequency range 12-18 GHz.It has been verified to work in a much wider frequency range and also with a good RL.No data has been found on the internet. The design is SMA (male) for RF input and SMA (female) for DCoutput. Length is 62mm and diameter 8mm. Judging from a gap in the label, this isa "multi-stage" design, possibly consisting of an integrated attenuator in front ofthe diode assembly itself.CheersUlf K

author: RoV
author_rank: Regular Contributor
timestamp: May 28, 2022, 12:29:07 pm
content: Herotek DT devices are Tunnel diode detectors. Look athttp://www.herotek.com/datasheets/pdf/Tunnel_Diode_Detectors_0.1-40GHz.pdfSure it is DT1812 and not DT1012? Coding seems always <low freq><high freq>, not the opposite.You say good RL, but this is not generally true for tunnel detectors, that tend to have poor VSWR. Unless -121 actually stands for attenuator input option... You could check by comparing typical sensitivity with yours.

author: Testnerd
author_rank: Newbie
timestamp: February 08, 2023, 06:45:04 pm
content: Hello Ulf,did you find any data for this detector. I also have such a DT1812-121 and would like to know for which frequency range it is intended.Measuring S11 of the device mine seems to be rather narrow-band with a optimum return loss of approx. 11dB at 2150MHz.Below 1.8GHz the return loss is less than 6dB and the same above 2550MHz.Kind regardsTestnerd
Baofeng UV-9R Plus modifications - Page 1
Forum section: electronics / rf-microwave

author: okw
author_rank: Frequent Contributor
timestamp: January 29, 2023, 03:47:29 pm
content: I've read a lot about various UV-5R modifications, so I decided to disassemble my UV-9R Plus in the hope it was only a rebranded UV-5R.It is not, board is entirely different. I've enclosed some pictures of it.Anyone modified this board?

author: okw
author_rank: Frequent Contributor
timestamp: January 29, 2023, 03:50:57 pm
content: Here are the rest.

author: Bicurico
author_rank: Super Contributor
timestamp: January 29, 2023, 04:22:28 pm
content: Hi,What do you want to modify?The Baofeng radios hardly comply with amateur bands as they are. Also, they have lots of unfiltered harmonics.You should be aware of what you are doing when modding these devices.Also, any reported frequency enhancement through hacked settings will only display the out of band frequencies, but you won't be able to use them.Kind regards,Vitor

author: okw
author_rank: Frequent Contributor
timestamp: January 29, 2023, 05:15:17 pm
content: Being a Chinese cheap radio, whatever enhancement it can have. I'm sure lot of people have been playing around with it and enhanced it.I don't use it for traditional ham radio, just for hunting (a set of 12 channels in the 2M band).I don't have any measurement tools except a Surecom SW-33 and a PS200.

author: iMo
author_rank: Super Contributor
timestamp: January 29, 2023, 05:38:25 pm
content: "12ch in 2m band" - are you a licensed ham operator?When not licensed do use PMR radios, good for hunting too..https://en.wikipedia.org/wiki/PMR446

author: bingo600
author_rank: Super Contributor
timestamp: January 29, 2023, 06:24:02 pm
content: Seens like they have "Upped the RF stage" in the newGT-5R Modelshttps://www.onesdr.com/baofeng-uv-5r-vs-gt-5r/

author: okw
author_rank: Frequent Contributor
timestamp: January 30, 2023, 12:08:51 am
content: I'm a registered member of the Hunters and Shooters Association, which has a license exception for the 12 channels.
Odd CB amp construction - Page 1
Forum section: electronics / rf-microwave

author: Mark19960
author_rank: Regular Contributor
timestamp: January 29, 2023, 07:05:05 pm
content: I saw this being done to one of these CB homebrew amps....They have these 8 or 10 gauge wires running over the tops of the transformers into the collectors, and then into some ferrites that appear to form yet another transformer...They call this some kind of "mod".Supposedly it's the "eye mod" and its supposedly to get more power to the transistors instead of via the center tapped winding.Whaaaaa?What am I missing? I can't even see how this works without oscillating and going boooooom...

author: vk6zgo
author_rank: Super Contributor
timestamp: January 30, 2023, 12:44:40 am
content: Quote from: Mark19960 on January 29, 2023, 07:05:05 pmPossibly an attempt at "shunt feeding" of the supply, but that would normally require a change of the whole architecture of the stage, to do it properly.

author: M0HZH
author_rank: Regular Contributor
timestamp: January 30, 2023, 04:35:01 pm
content: That is a balanced feed transformer, used so the supply current doesn't saturate the output transformer; as collector impedance is very low, you need surprinsingly little choking impedance.Good resource, if you have the patience to read the whole thing:https://ludens.cl/Electron/RFamps/RFamps.html

author: Mark19960
author_rank: Regular Contributor
timestamp: January 31, 2023, 05:33:32 am
content: Interesting. Thanks for the link. So far it's answered a few burning questions.
Copper-tape microstrip prototyping on a PCB of unknown dielectric substrate - Page 1
Forum section: electronics / rf-microwave

author: szoftveres
author_rank: Regular Contributor
timestamp: January 24, 2023, 06:01:23 am
content: It was fun doing it, so wrote up the process:First we need to determine the Er of the substrate. We have a 1/4" wide copper tape and a 1.4mm thick single-sided PCB with a ~35um thick copper layer on it to work with:After building a transmission line with this copper strip of known width on the PCB of known thickness, we need to determine its characteristic impedance; we can use the 1/4 wave impedance transformer method for this: a 1/4 wave impedance transformer terminated by 50ohm on one side looks purely resistive on its other side at the frequency where it's behaving as a 1/4 wave impedance transformer, and the impedance it's showing (measured by VNA) is based on how it's reflecting the 50ohm termination back, based on its own characteristic impedance. The characteristic impedance of the transmission line can then be derived from the impedances at its two sides: Zt = sqrt(Z1 * Z2), where Z1 is the termination impedance (50ohm) and Z2 is the measured impedance (16ohm) at its other side.The resulting characteristic impedance of the transmission line is 28.28ohms, which checks out, as the trace is quite wide and impedace gets lower with more capacitance (Z = sqrt(L/C)).Next, we can use an online microstrip calculator tool to come up with an Er for the substrate, knowing that building a 1/4" wide trace on a 1.4mm thick piece of it results in a 28.28ohm transmission line:The resulting Er is around 4.3, which also checks out; it's a common number for FR4 substrates. We can use the same tool to come up with a width for the final, 50ohm transmission line:The resulting width is 2.72mm.We can verify the new 2.72mm wide transmission line, by again using the 1/4 wave impedance transformer method. The new, 50 ohm terminated 1/4 wave impedance transformer is showing impedances between 44ohm and 50ohm, corresponding to 47-50ohm transmission line characteristic impedance.

author: joeqsmith
author_rank: Super Contributor
timestamp: January 24, 2023, 12:22:54 pm
content: About 50 minutes into the review, I show several copper-tape experiments. Nothing too complex. Just needed some props to show the VNA making some higher frequency measurements.

author: szoftveres
author_rank: Regular Contributor
timestamp: January 25, 2023, 03:02:23 am
content: Now that this thread turned into a collection of Youtube videos, let me also post one that actually inspired the idea in the original post of measuring the Er of the substrate (as opposed to just assuming Er=4.5):
saw filter Will the adapter have an effect on the impedance of the filter ? - Page 1
Forum section: electronics / rf-microwave

author: DavidAzulay5000
author_rank: Regular Contributor
timestamp: January 24, 2023, 03:40:24 am
content: a questionI ordered Today the filtersTo repair the RXTX boardof my CMU200SAW 836.5MHZSAW 1842.5MHZ B39182-B4139-U410 1842.5MHz SAW Filter 50 Ohm SMD B69813-N1847-X475 PCN RX Filter 1842MHz SMD B39841-B4122-U410 836MHz SAW Filter SMDSince the filters I ordered are small size3 mm x 3 mmI am considering soldering them on a PCB adapter.the questionWill the adapter have an effect on the impedance of the filter??...??

author: geggi1
author_rank: Frequent Contributor
timestamp: January 24, 2023, 09:14:13 am
content: Most likely it will have an effect because the traces on your radiotest-set i matched lines.

author: DavidAzulay5000
author_rank: Regular Contributor
timestamp: January 24, 2023, 09:49:21 am
content: Quote from: geggi1 on January 24, 2023, 09:14:13 amThanks, that's what I thought tooi will stitch the filter directly to the PCB.I sailorsSmall copper wires to the pads of the filterThen solder them directly to the PCBThis is going to be a bit of a headacheWith such a small filterThe original was huge
Mini circuits programmable attenuator 31dB 5 bit - Page 1
Forum section: electronics / rf-microwave

author: Vaman
author_rank: Newbie
timestamp: January 22, 2023, 05:06:45 pm
content: I posted this elsewhere but realised this forum would be more appropriate.I purchased a Mini Circuits ZX76-31A-PPS+ off Ebay and I am trying to source the 10 way control connector. Mouser etc want £35.00 for a 1.5mtr cable, which is more than paid for the attenuator. I have seen the connector sometime ago but do not know what it is called in order to trace it.Link to official cable below as you can see they do not give anything away.

author: berke
author_rank: Frequent Contributor
timestamp: January 22, 2023, 06:43:31 pm
content: I couldn't find anything similar on Digikey. I looked for 10-way connectors and cable assemblies.Minicircuits modules are easy to open. How about you remove their weird-ass custom connector and solder your own wires directly? It would be interesting if you posted pictures of the inside. Are you planning to change the attenuation at a particularly high rate? If not it shouldn't require anything particular.

author: Vaman
author_rank: Newbie
timestamp: January 22, 2023, 08:47:56 pm
content: That certainly is an option, however the construction is in solid brass and the sma are machine engineered to fit, so de-soldering will be difficult without damaging the smd components. I will have another look on my bench tomorrow. I will photograph it as well. It is much smaller than the photo suggests.

author: paul@yahrprobert.com
author_rank: Regular Contributor
timestamp: January 22, 2023, 11:41:45 pm
content: I looked at mine, and it had HRS printed on the label, and the pitch looks like .5 mm. A search on digikey yielded Hirose ST40X-10S-CV, which looks right. There's also a CVR, which seems to be bottom mount (on the PC board).

author: Vaman
author_rank: Newbie
timestamp: January 23, 2023, 06:40:08 am
content: Thank you very much Paul. I have done a bit more research on that part number and find that it is actually listed in very small typeface on one of the other Mini Circuits products (USB-1SP2T-A44) for a serial interface. So the confidence level is now very high and at £2.45 plus tax that will be on my next Mouser order.Thanks again.