hybridfree/eevblog-posts huggingface dataset:
What's the difference between these antennas? - Page 1
Forum section: electronics / rf-microwave

author: Thermoelectric
author_rank: Contributor
timestamp: January 23, 2022, 01:32:56 am
content: Hey all,Bit of background, these antennas are for LoRaWAN hotspots (specifically Helium) and there's a lot of noise about some antennas being better than others. I bought a couple of each and haven't seen massive differences in performance, however the antennas seem reasonably physically different to eachother. I tried delving into researching antenna design to make sense of it and it seems like quite the rabbit hole.The grey one is a 6dBi "tuned" 915MHz antenna VSWR 1.02 (this is the "better" antenna), the white one is 5.8dBi 915MHz VSWR 1.13.Given they're about the same gain, why does one have more "sections" than the other? A friend suggested this could be due to one being half wave vs full wave etc. but that's well over my head and wasn't overly apparent from information I could find online.Here are some other cheapies from Aliexpress, same design but also with differing numbers of segmentsMy guess is they're some weird collinear design, like figure 3 here. This also seems to be some RF voodooThanks for any help!edit: seems I can't make the inline attachments work but you get the idea

author: cdev
author_rank: Super Contributor
timestamp: January 23, 2022, 02:14:13 am
content: The bottom antenna appears to be missing its top.These are collinear antennas. You found the patent which explains how they work. You can make them yourself, easily, and they work, well, for UHF, but it makes sense to measure theexactvelocity factor of that specific batch/kind of coax.
VNA Saver - Page 1
Forum section: electronics / rf-microwave

author: Grandchuck
author_rank: Super Contributor
timestamp: January 10, 2022, 04:46:51 pm
content: There is a relatively new version, 3.10. It works on my Windows 11 PC whereas the earlier version would not. I could not increase the number of sweep segments and now I can. Thought this might help someone else.

author: Grandchuck
author_rank: Super Contributor
timestamp: January 10, 2022, 07:29:39 pm
content: Here is a Smith Chart of port CH0 of a Nano VNA using a NanoVNA V2Plus4. The sweep was from 10 MHz to 900 MHz with 11 segments.

author: Grandchuck
author_rank: Super Contributor
timestamp: January 10, 2022, 08:31:18 pm
content: Here is a better Smith Chart result. I removed a coax segment that should have been removed the first time

author: clytle374
author_rank: Regular Contributor
timestamp: January 23, 2022, 07:34:15 am
content: Thanks, runs in Linux. Just built and installed it, will check it out better later. Cory
PCB Review: First Radio Project - Page 1
Forum section: electronics / rf-microwave

author: derGraph
author_rank: Newbie
timestamp: January 22, 2022, 07:42:16 pm
content: Hello,My Name is Paul and I am a higher Secondary Student on a electrotechnic focused school.I found this really cool RF Transceivers from TI. It is the CC112x Family and now im trying to design a PCB around it. I found the BALF wich is, in a nutshell all the passive components that would be needed. Can some of you more experienced Volks take a glance over it. The BALF is connected exactly like the datasheet states and the output to the antenna should be impedance matched to 50 Ohms. I did this with the Layer Stack Manager.Thanks,Paul

author: derGraph
author_rank: Newbie
timestamp: January 22, 2022, 10:58:53 pm
content: Thanks for the help, I implemented some of your Tips and will send this PCB of soon.

author: Bud
author_rank: Super Contributor
timestamp: January 22, 2022, 11:56:21 pm
content: As an RF best ptactice , run separate grounding vias right next to each component that is grounded, do not run a bus grounded with a single via. And if space allows, make 2-3 grounding vias for each component.When will be soldering, solder the SMA connector last, otherwise it will suck much of heat and you may have difficulties soldering other components close to it.
BLE Antenna impedance matching - Page 1
Forum section: electronics / rf-microwave

author: ivonenand
author_rank: Contributor
timestamp: January 21, 2022, 08:06:19 pm
content: Hi guys,I'm looking for a small Bluetooth 2.4Ghz SMD antenna and I came across a part from Wurth Elektronik, part no. 7488960245. The Antenna is specified to have a 50 Ohm impedance, great.However, one page below in the datasheet, there is a typical connection diagram, which includes an impedance matching circuit made of a 1.2pF capacitor and 2.2nH inductor.There's even a PCB example, where if you enter with a 50 Ohm line, you go through the matching circuit first, and then to the antenna.Now here's what's confusing me. If the feed/input impedance is 50 Ohms and the Antenna impedance is also 50 Ohms, why do you need an impedance matching circuit?Thanks for any input on this topic,Regards,Ivo

author: E Kafeman
author_rank: Regular Contributor
timestamp: January 22, 2022, 08:51:36 am
content: Correct, no need for matching if feed to antenna and antenna is conjugate matched.IRL does it never happen.Transmission line is not ideal and TX/RX radio impedance is neither ideal 50 Ohm.Antenna real impedance is an factor of its nearfield environment. Ground size and enclosure dielectric properties will affect antenna impedance.Big enough ground area and length is even more critical for selected type of short quarterwave ceramic antenna, which needs to be mirrored in ground with low losses to create a full halfwave antenna without to much losses and less efficiency.That is why by Wurth provided PCB example have a rather big ground area at 2.4GHz, to achieve decent measured antenna efficiency, bandwidth and for simpler tuning.
2-4W VHF Linear PA suggestions - Page 1
Forum section: electronics / rf-microwave

author: vu2tve
author_rank: Contributor
timestamp: January 21, 2022, 03:49:46 pm
content: Hi,I need to build a driver stage that will sit between a LimeSDR and a MRF101AN based final output stage.I'm shooting for about 16-18 dB of gain, and a final output power of 33-35dBm.Any suggestions where I can look for to begin design? I'm not averse to building PCB's if there are good reference designs available. I'm looking specifically at the FM Band of 88-108MHzP.S. I know that the drive needed by the MRF101AN is just 1W. However, I would like to have some legroom so having a max output power of 2-3W is desirable. I can tweak the signal power from the LimeSDR to get the right output power.Thanks!

author: David Hess
author_rank: Super Contributor
timestamp: January 21, 2022, 11:45:00 pm
content: Other than cost, why not cascade two MRF101AN stages?

author: M0HZH
author_rank: Regular Contributor
timestamp: January 22, 2022, 12:26:00 am
content: LimeSDR will require some output filtering before amplifying.RD06HVF1 is commonly used for HF/VHF and will fit the bill on gain and output power; it runs at a lower voltage (13.5V typically) than the MRF101 stage and there is an official application note for 175MHz that could be adapted:https://www.mitsubishielectric-mesh.com/products/pdf/rd06hvf1.pdfThere are 88-108MHz designs out there that use it, it's worth looking around.

author: vu2tve
author_rank: Contributor
timestamp: January 22, 2022, 06:32:20 am
content: I was just thinking that myself!! Thanks for nudging me further. I have an MRF101AN on hand and am going to build another PCB for it.Also, I contact NXP and they recommended these two active part numbers - MW6S004N and AFIC901N.Thanks!

author: vu2tve
author_rank: Contributor
timestamp: January 22, 2022, 06:34:40 am
content: Yeah. I can see some ebay sellers selling this part.Long ago, I had purchased a "15 Watt FM amplifier" from aliexpress that used RD15HVF1, and after much headache, it turned out that the transistor was a dudSo I'm thinking I'll order a couple of RD06HVF to experiment with, but possible go with active part numbers sold through mouser/digikey etc, so that I don't run the risk of getting a dud.

author: vu2tve
author_rank: Contributor
timestamp: January 22, 2022, 06:38:24 am
content: Also, I see this part number being mentioned a bit too - rqa0009 (does not seem to be an active part, except being found on ebay)wonder if there is some experience in the community here with this (https://aliot.com.ua/pdf/rqa0009.pdf)
Colby variable delay lines - Page 1
Forum section: electronics / rf-microwave

author: KrudyZ
author_rank: Frequent Contributor
timestamp: January 22, 2022, 05:32:43 am
content: For anyone interested in these, there are two hiding inside this box that can be had for cheap.Also includes six DIN rail power supplies, some FPGA board and a nice box with fans...https://www.ebay.com/itm/294592027949?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m1438.l2649Please someone buy it so I won't
Mixer usage in spectrum analyzer  - Page 1
Forum section: electronics / rf-microwave

author: prutser
author_rank: Regular Contributor
timestamp: January 21, 2022, 03:54:19 pm
content: Most analyzers start at 9kHz, which is upconverted to a IF. The mixer output will be LO+9kHz and LO-9kHZ.If The RBW > 18kHZ (which is not so strange) the detector 'sees' both signals, for lower RBW it might just see 1 of the 2If it would be an FFT analyzer which f.i. takes an FFT of an IF bandwidth of 10MHz it will show both signals.Does anyone know if my assumption is correct and how an SA deals with this behaviour, which mainly applies at the lower end of the spectrum ?Thanks

author: coppercone2
author_rank: Super Contributor
timestamp: January 21, 2022, 09:35:16 pm
content: in a nut shell people don't like using spectrum analyzers for audio work so much

author: David Hess
author_rank: Super Contributor
timestamp: January 21, 2022, 11:50:13 pm
content: The solution I have seen is a warning in the documentation or lockout to prevent a wider RBW than the sweep start.
Recommended design for a 50 ohm matched FM band class-A RF PA with 1W output - Page 1
Forum section: electronics / rf-microwave

author: vu2tve
author_rank: Contributor
timestamp: January 13, 2022, 05:15:19 am
content: Wishing : class-A FM band PA with 1W outputThe reason for this post is that I'm ordering a bunch of components from lcsc and owing to high shipping costs, it makes sense to get "wishlist" components on top of the required components.I'm using an AliExpress linear pre-amp at the output of a LimeSDR and it's output is driving a MRF101AN reference design. Eventually, I'd like to be able to have everything on a single PCB (integrate the reference design of the MRF with a pre-amp on the same board).I guess there are all kinds of 50 ohm matched gain blocks available, and perhaps some standard transistor designs offering 1w output power in the FM band with not too complicated matching, so asking if anyone has any experience or suggestions for the same.I'm ordering a nanoVNA to take guesswork out of matching impedances in the future if need be.Thanks. 73 // VU2TVE

author: vk3yedotcom
author_rank: Frequent Contributor
timestamp: January 14, 2022, 08:05:02 pm
content: You would generally use Class C amplifiers for an FM transmitter.Class A isn't needed and Class C is more efficient.

author: vu2tve
author_rank: Contributor
timestamp: January 19, 2022, 10:44:05 am
content: I understand, but I'm experimenting with creating a multi carrier signal, so a linear amplifier is required.My basic internet research tells me that a company called micro-circuits makes amplifier ic's that may be suitable...https://www.minicircuits.com/pdfs/PHA-13HLN+.pdfIf anyone knows more such modules, or even transistors/mosfets offering a simple design, i'm willing to try
Anyone experience with 28V microwave relays ? Bought one, coil current ~ 150mA ? - Page 1
Forum section: electronics / rf-microwave

author: prutser
author_rank: Regular Contributor
timestamp: January 18, 2022, 06:51:02 pm
content: I have no expererience with microwave relais. Bought 2 used 18GHz relays. One from Sivers/Philips, draws about 40mA @ 28VThe other one from Microwave Associates (brand seems to be sold regularly on Ebay, but I cannot find any details)Coil does 160mA @ 28V which is over 4 Watts.Does anyone knows if this is usual for those kines of relays ?

author: TheMG
author_rank: Frequent Contributor
timestamp: January 19, 2022, 01:27:36 am
content: It can be normal depending on the design and size of the relay. Some have quite large and multiple mechanical moving parts that require a stronger coil.

author: Bud
author_rank: Super Contributor
timestamp: January 19, 2022, 02:01:41 am
content: Maybe it was designed for fast switching with higher energizing voltage and then to lower holding voltage.

author: radar_macgyver
author_rank: Frequent Contributor
timestamp: January 19, 2022, 06:39:01 am
content: Some include a freewheel diode internally (HP/Keysight relays in particular), so polarity matters for those. If forward biased, current draw will be high.

author: Whales
author_rank: Super Contributor
timestamp: January 19, 2022, 07:19:15 am
content: Are the eBay ones cheap? Crack one open and see what's inside.I'd also try and verify that their coils have been wound correctly (thickness of wire + number of turns) for 28V. Try hooking up the coil inputs to a power supply and slowly turn up the voltage until the relay clicks. If it moves at only 3V then you know it's wound incorrectly, if it latches at a bigger fraction (eg 12V?) of the full 28V then it's probably wound correctly for 28V.

author: cj
author_rank: Contributor
timestamp: January 19, 2022, 09:56:09 pm
content: It might also be a bi-stable relais which only requires a short pulse to switch after that no power is required anymore. The polarity of the pulse determines which port is selected.160mA @ 28V is excessive, as Bud says it may require a lower holding voltage.I just measured a 28V SMA relay (Transco) and it draws 80mA @ 24V which should be about 90mA @ 28V and it holds fine at 12V 40mA.CJ

author: jonpaul
author_rank: Super Contributor
timestamp: January 20, 2022, 09:27:23 am
content: Most of the RF relays I have do not include any diode.Check the resistance of the coil.Perhaps the high current relay is not 28V but 12?Jon

author: Joel_Dunsmore
author_rank: Regular Contributor
timestamp: January 20, 2022, 04:38:51 pm
content: Check if it is a latching relay (someone mentioned bi-stable). You will can switch it then remove the drive voltage and see if it holds the state. If it does, then you can just send a pulse and to switch and switch back. Some have both latching RF and DC (Keysight switches work this way) where there is also a relay on the DC side so when you apply the drive voltage, the relay snaps across and the DC contact is broken as the switch is moving. A couple of tests will sort out if you need to drive them all the time.
evaluation of rogowski coil bobbin? - Page 1
Forum section: electronics / rf-microwave

author: coppercone2
author_rank: Super Contributor
timestamp: January 17, 2022, 05:37:23 pm
content: There are 3 rogawski coil bobbins on thingiverse that you can download and 3d print. I wanted to make one.https://www.thingiverse.com/thing:1055336https://www.thingiverse.com/thing:935605https://www.thingiverse.com/thing:283430Does anyone have any information on if these would be considered quality parts?And how well do they resize.. if I rescale the print for smaller wire, do other parameters need adjustment or is it essentially dimensionless?

author: coppice
author_rank: Super Contributor
timestamp: January 17, 2022, 05:47:44 pm
content: Making a Rogowski coil measure well is easy. Making a Rogowski coil give good suppression of external fields is hard. Good suppression usually involves a lot of mathematical modelling in design, and precision manufacture. I've seen labs that look like component graveyards, where people have invested a lot in trying to achieve a current sensor that eliminates the cost and non-linearities of the core in a current transformer and failed to achieve adequate performance. This is why most of the Rogowski coils you see in real world use are measuring large currents, where the signal of interest generally swamps any external fields.

author: coppercone2
author_rank: Super Contributor
timestamp: January 17, 2022, 05:57:14 pm
content: The immunity problem is a hard one... but this seems like a fun way to kill a few hoursWhat do you think the most promising design is? This looks downright fun compared to what I was trying to do with bending plastic tubes and threading wire etc (bunch of horse shit).. this could be the first time I used my 3d printer for a electrical device
Frequency doubling using diodes - Page 1
Forum section: electronics / rf-microwave

author: Aiy
author_rank: Regular Contributor
timestamp: January 15, 2022, 08:04:46 pm
content: Hello Everyone,As some may have seen I have a broken Anritsu SDM module (Topic here:https://www.eevblog.com/forum/repair/wiltron-anritsu-switched-frequency-doubler-module/)This module has a frequency doubler which mutiplies the fundamental 2-20GHz YIG oscillator in the Anritsu machine to give output up to 40GHz.My question is this:If I attempt a repair and switch out the diodes, can I in principle use any Schottky diodes with enough power tolerance to repair my unit, or is there something else to it?I see that Macom has the step-recovery type listed for multipliers and comb generation (possible candidate would behttps://www.macom.com/products/product-detail/MMDB45-B11), but my knowledge is lacking in this field.The original diodes in the SDM device seem to be four diodes in series, anchored in between the middle. The whole thing is a beamlead thing that I have not found anywhere, so its probably custom..ASCII CAD: ( ->| = diode )GND - 50R - ->| ->| - Sig ->| ->| - 50R - GNDI have measured the forward voltage drop between the "inside of the 50Ohm resistors to the "Sig" point, and it's 1.2V-isch, indicating two diodes.Pictures of the SDM unit is in my other topic..Best regards

author: Joel_Dunsmore
author_rank: Regular Contributor
timestamp: January 15, 2022, 08:14:46 pm
content: posted in the link instead of here:If you happen to attend the ARFTG / RWW conference starting next week, you'll likely find Jon Martens there, and I guess he might have either designed the part or knows a lot about it.www.arftg.orgorwww.radiowirelessweek.orgtiny diodes, likely with very low parasitic capacitance.

author: RoV
author_rank: Regular Contributor
timestamp: January 16, 2022, 09:24:33 am
content: I think they are GaAs Schottky diodes, a couple in series each side to handle the required peak voltage.Referring to the other post of yours: the input 20 GHz signal enters from the top in microstrip; then there is a transition from microstrip to slotline: the diodes rectify the signal and send the opposite half waves on opposite sides, so the signal that propagates along the slotline is a full-wave rectified version of the original, hence at double frequency. Follow matching and filtering stages, probably based on varactor diodes with bias adjusted according to the frequency. The end of the slotline seems to be just below the main line of the 1st figure.Replacing those diodes is really hard...
OT? visualizing waves in real world - Page 1
Forum section: electronics / rf-microwave

author: A.Z.
author_rank: Super Contributor
timestamp: January 13, 2022, 12:54:21 pm
content: forgive me, please, for this offtopic, just had my 3rd vax shot and maybe those are the side effectsSeriously, I was checking "sciencealert" and found thishttps://www.sciencealert.com/new-study-reveals-the-secret-math-hidden-in-sand-megaripplesand while it isn't about RF waves, I think it's still fascinating (together with the Nature article linked at bottom); with the due differences, paralleling the above with RF waves is somewhat mind blowing, so I thought to share it hereIf you believe it's inappropriate, just tell me so and I will delete this post !anyhow..."if the wind gets too strong, the mechanisms creating the megaripples get overpowered."overmodulation?
Needed information about Motorola MT2100 transivers - Page 1
Forum section: electronics / rf-microwave

author: bborisov567
author_rank: Regular Contributor
timestamp: January 12, 2022, 08:24:44 pm
content: Recently i got a pair of Motorola MT2100 units. Could somebody share some information about theese transivers? Nothing comes up on Google, except that site:https://www.rigpix.com/protrx/motorola_mt2100.htmWhat are the other two units with displays on the second picture? Any information would be appreciated!

author: TheSteve
author_rank: Unknown
timestamp: January 13, 2022, 01:53:30 am
content: Looks like an MT2000 - perhaps an updated version?Your best bet is probably Batlabs and the forum -https://batboard.batlabs.com/
An interesting old antenna (10dBi at 17° TOA) - Page 1
Forum section: electronics / rf-microwave

author: A.Z.
author_rank: Super Contributor
timestamp: January 12, 2022, 11:58:18 am
content: Just stumbled upon an antenna design from P.Carr (N4PC) dating back to 1995 and describing a simple, cheap wire antenna offering a gain of about 10dBi with a takeoff angle around 17° from horizon and a feedpoint impedance in the 50 Ohm range; being interested I decided to model the thing using NEC and the results confirmed what reported in the Carr article (see attached PDF) showing that the antenna should be a pretty good "DX gun"On the "cons" side, given the dimensions, such an antenna isn't really suitable for the "top bands", yet, for the bands from 17m up to 6m and for the VHF it will be viable, the antenna in object is made by stacking two horizontally "squished" quad loop elements one above the other and the performance of such a simple design is quite impressive; for further informations and pointers about this antenna, please seehttps://sites.google.com/site/wvfisher/hdoublebayAs for the NEC model I used, it's pretty raw, but if someone wants to fiddle a bit and run some simulations, here it isCode:CM --------------------------------------------------------------------CM H-DoubleBay https://sites.google.com/site/wvfisher/hdoublebayCM Note: according to the informations found at the above site, theCM optimal height for this antenna is the one which places the midCM junction at an height of about 1/2 lambda, also notice that theCM characteristic impedance of this antenna is about 50 OhmCM --------------------------------------------------------------------CE' calculated valuesSY freq=29.000 ' calculation frequencySY wire=0.00125 ' wire radiusSY conv=3.281 ' feet-meters conversion factorSY wave=(300/freq) ' wavelengthSY spcr=(110/freq)/conv ' horizontal elementsSY vert=(365/freq)/conv ' vertical elementsSY hspc=(spcr/2) ' half horizontalSY hght=(wave*0.75)-vert ' height of bottom from groundSY base=hght ' lower pointSY midp=base+vert ' mid pointSY uppr=midp+vert ' upper pointSY segm=51 ' vertical segmentsSY segs=7 ' horizontal segments' vertical elementsGW 1 segm -hspc 0 base -hspc 0 midp wireGW 2 segm -hspc 0 midp -hspc 0 uppr wireGW 3 segm hspc 0 base hspc 0 midp wireGW 4 segm hspc 0 midp hspc 0 uppr wire' horizontal elementsGW 5 segs -hspc 0 uppr hspc 0 uppr wireGW 6 segs -hspc 0 midp hspc 0 midp wireGW 7 segs -hspc 0 base hspc 0 base wire' ground (real, standard)GE -1GN 2 0 0 0 13 0.005' loading (copper=58000000, aluminium=37700000)LD 5 0 0 0 58000000' feedpointEKEX 0 7 (segs/2) 0 1. 0 0' test frequencyFR 0 0 0 0 freq 0' end of modelENas a note, an alternate way of building such an antenna (other than the one described in the PDF) is to use a pair of "squidpoles" to support the antenna vertical sections, with such an approach the squidpoles will be almost free to swing in the wind and the antenna should be able to support even strong winds, then, some "T" support at the bottom could allow to rotate the antenna and aim it as desired
433MHz Maximum Tx level in Texas if that matters) ? - Page 1
Forum section: electronics / rf-microwave

author: Jester
author_rank: Frequent Contributor
timestamp: February 01, 2022, 02:48:38 am
content: I did some preliminary testing of HC-12 modules operating at 433MHz, they seems to work pretty well. Near 1000' at 1/10 output power level.I'm not up on the FCC rules, any of you Southern guys and gals no if these HC12 modules can be used license free in the USA and if so, at what maximum power levels? Idea was to use in Texas if that matters. Data will be sent very intermittently perhaps a few seconds per day total in a few bursts of 15-50 ms.Thanks

author: nealix
author_rank: Regular Contributor
timestamp: February 07, 2022, 05:15:17 pm
content: These boards can transmit in two licensed bands, requiring the appropriate radio license in order to be legaland to coordinate/avoid interference. 430-450 MHz requires an amateur radio license, and channels above450 MHz would require a different license.Permitted power level is based on which band you are using, and what class your license is.For those who enjoy ignoring the rules, licensed users in both of the above bands haveexcellent equipment and skills for locating rogue signals and pin-pointing the exactlocation.Get licensed or DO NOT USE.Just because an international seller can offer something on eBay, that does notautomatically mean it is legal to use it in your specific country/location.In fact, various vendors paid $millions$ in fines last year due to this sametype of thing; Selling modules and equipment to USA buyers that violatedlocal licensing and use requirements.Ignoring the rules can be very expensive.

author: bdunham7
author_rank: Super Contributor
timestamp: February 07, 2022, 05:32:09 pm
content: Quote from: nealix on February 07, 2022, 05:15:17 pmThe law actually appears to allow this sort of use without licensing, within certain limitations and subject to interpretation. There are all sorts of these devices and the only reason I can think of why they'd be illegal is exceeding power limits, which is what the OP appears to want to know about. I don't know anything about the HC-12 specifically, but the rules are here:https://www.ecfr.gov/current/title-47/chapter-I/subchapter-A/part-15/subpart-C/subject-group-ECFR2f2e5828339709e/section-15.231It looks to me that the OP's device would at least be permissible under section (e) provided it meets the power limits.
Help with  Microwave Modules 2m Linear Amp -  MML 144/100-S - Page 1
Forum section: electronics / rf-microwave

author: rjmusto
author_rank: Contributor
timestamp: January 03, 2022, 12:25:40 pm
content: Hi Guys,Have been handed one of these 1980's (?) 2m amplifiers to check out and have a couple of things I am unsure about, so hoping someone here is familiar with them....It is basically working; I can set the bias current to be around 1.4A and and, having tuned it up am seeing 12dB of gain. Nice.But...setting the bias (and I know the spec says it should be 1A) is very sensitive, the trimmer pot is almost at zero and just a tiny tweak will lift the current from a few hundred milliamps, to over 1A. And it's not very stable. Is this just and ageing transistor maybe?The other issue, is the 22ohm dropper resistor to the bias circuit gets very hot - not surprising really, as the bias voltage is around 0.7v, so the resistor is having to handle around 8W. So no wonder it gets very hot. I don't see that as a good long term situation though, and there's no sign of past heating on the pcb. So what am I missing here?Any thoughts much appreciated.I've attached the MM info sheet which has the schematic and an image show the innards of this one.Thanks,Ralph

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: January 04, 2022, 12:35:44 am
content: Can you look for spurious frequencies, i.e. oscillations? Probably on a spectrum analyzer.If there are any then try to tune them out?Wally KC9INK

author: rjmusto
author_rank: Contributor
timestamp: January 05, 2022, 01:26:51 pm
content: Hi Wally,Haven’t seen any sign of instability.And having got the amp tuned up properly (phantom twiddlerer had been here) it is producing close to 100W, so happy with that.I’m just not happy with the stability of the bias circuit. I know these clamp diode types can be improved by adding a transistor, but I’m reluctant to mess with it - it’s not mine, belongs to a friend. “If it aint broke, don’t fix it” and all that…..Ralph

author: Flux-Sucking Shunt
author_rank: Newbie
timestamp: January 10, 2022, 02:17:59 am
content: Declare victory and move on.But that rats-nest wiring makes my skin crawl a bit.
Simple Class-D audio level shifter/amplifier (or PWM level shifting from 3.3V)? - Page 1
Forum section: electronics / rf-microwave

author: wb0gaz
author_rank: Frequent Contributor
timestamp: January 08, 2022, 10:33:46 pm
content: I have a PWM audio source (24 kHz "carrier", width modulated to carry audio envelope.) It is working fine, but with 3.3V out of the microcontroller, it's quite feeble to drive (through a large blocking capacitor) a (4 ohm) speaker.I added four parallel gates from a 74ACT244 level shifter (at 5V) into the path from the microcontroller PWM output to the (4 ohm) speaker. I now get reasonably good quality audio (tone) and adequate, but not excess volume.I'd like to carry this one step further.I would like to buy/build a level shifter that functions like the 74ACT244 parallel gates, but runs from a higher voltage, say 6-12V. I'm open to building, but it would also be of interest if such a thing exists as an IC (3.3V logic in, "6-12V logic" out, 6-12V power supply, and saturated current of up to several amperes (6V/4 ohms = 1.5 amps, at least as a starting point.)I'm looking for recommendation of such a level shifter or amplifier stage. I'm new to Class D, but I imagine this is what I've stumbled into, and it's fascinating stuff!Thanks for any getting-started guidance...Dave

author: langwadt
author_rank: Super Contributor
timestamp: January 08, 2022, 10:38:24 pm
content: a gate driver like a TC4422 could work

author: wb0gaz
author_rank: Frequent Contributor
timestamp: January 08, 2022, 10:41:00 pm
content: Thanks! I hadn't thought of using a gate driver, and that certainly makes sense as a starting point, certainly easier than discrete fets!Dave
A nose for electronics?  - Page 1
Forum section: electronics / rf-microwave

author: cdev
author_rank: Super Contributor
timestamp: January 07, 2022, 12:28:01 am
content: This paddlefish has a "rostrom" an electro sensor . Could it act as a receiver at high frequencies?But its almost extinct. I thought it was interesting with itsampulae of lorenzini.How can it be saved? The Chinese paddlefish is already extinct.The US paddlefish species is ancient, 150 million years old. And its almost extinct.....
When use which Cable Type? - Page 1
Forum section: electronics / rf-microwave

author: Lord of nothing
author_rank: Super Contributor
timestamp: January 06, 2022, 10:48:17 pm
content: Hi everyoneI a rush I bought from a Store some RG-405 Cable who I needed. The are just SMA to SMA in variable length.The are very sturdy and more like a roll of Alu Folil.Did I bought some wrong? I want mount them in a Case where the splitter and SDR mount to a Plate to avoid slipping and crashing.Thanks!

author: jjoonathan
author_rank: Frequent Contributor
timestamp: January 06, 2022, 11:29:11 pm
content: Ah, semi-rigid coax. The RF performance is excellent: the isolation is nearly perfect, the frequency range approaches theoretical, and it's about as phase stable as you can get with a solid teflon dielectric. This is the stuff HP used to plumb the internals of their 50 GHz VNAs! In these regards it is overkill. However, as you note, it's mechanically unwieldy. It needs to be bent into shape and you can only bend it once. Well... you can probably get away with a small number of bends, but nobody's going to give you any guarantees beyond the first.Yes, it's really meant for situations where all the components are mounted and not expected to move relative to one another.Still, if you have it, you might as well use it. If you "test it to failure" you will buy yourself valuable physical intuition that can apply to cable assemblies 10x or 100x the cost.
Quagi antenna, vertical - feedline where? - Page 1
Forum section: electronics / rf-microwave

author: TinkeringSteve
author_rank: Frequent Contributor
timestamp: January 06, 2022, 04:42:21 am
content: Hello,I built a Quagi antenna for 70cm to be used on FM, so I'd use it in vertical polarization.When using horizontal, it seems intuitive how to lay the RG58 cable going to the feed point - feeding from the lowest point of the driven loop, if the cable hangs downwards for some distance before getting close to the mast, it is the furthest away from all elements and won't influence them significantly (I guess).But for the side-fed driven element in vertical polarization: How should the coax cable, from the feed point, be led towards the mast?

author: A.Z.
author_rank: Super Contributor
timestamp: January 06, 2022, 08:54:58 am
content: see here for an ideahttps://www.hamuniverse.com/3el2meterquad.html

author: TinkeringSteve
author_rank: Frequent Contributor
timestamp: January 06, 2022, 11:35:24 am
content: Quote from: A.Z. on January 06, 2022, 08:54:58 amThey show it going to the boom. And then? Just downwards from ther? Doesn't disturb the cable almost going inside the loop?(I mean, if I then go down from the boom to the mast, in my vertical Quagi, that would be like a half extra director pointing downwards, that's connected to shield / is the shield)

author: Bud
author_rank: Super Contributor
timestamp: January 06, 2022, 09:25:06 pm
content: See if this article from the ARRL Antenna Book is useful. Fig.52 on the second page and last paragraph on page 3 provide details on construction of the feeder.

author: TinkeringSteve
author_rank: Frequent Contributor
timestamp: January 06, 2022, 10:53:27 pm
content: Thanks!
BG7TBL filter power ratings? - Page 1
Forum section: electronics / rf-microwave

author: Ultrapurple
author_rank: Super Contributor
timestamp: January 07, 2022, 10:17:27 am
content: Hi allNew to this section, not new to EEVblog.Has any one found any info on the power ratings for those very nice metal-cased filters by BG7TBL? I'm using a 50MHz version on the output of a Chinesium 3Wsquare wave generatorRF amplifier for a WSPR transmitter and it works very nicely, but pointing a thermal camera at the beastie's internals shows that the inductors are warming at aquarterof that power level (the input attenuator in the image was 6dB). To be fair, the filter is removing a significant amount of unwantedness and that power has to gosomewhere. But I don't want to pop the filter, as I'm generally pretty impressed with its performanceSo, any ideas on the actual power dissipation limit? Are there any published specs?Thoughts welcome.
Frequency Multiplier circuit / phase contorle circuit design - Page 1
Forum section: electronics / rf-microwave

author: Kashif khan
author_rank: Contributor
timestamp: January 04, 2022, 08:27:27 pm
content: Hello, i need a frequency multiplier circuit and phase control circuit with which i can adjust the output multiplied frequency phase with respect to input given signal.The circuit should be based on analog componenet, thankyou in advance for guidance.

author: David Hess
author_rank: Super Contributor
timestamp: January 05, 2022, 06:22:30 am
content: What frequency range were you interested in? PLLs (phase locked loops) can both multiply frequency and modulate phase.

author: Kashif khan
author_rank: Contributor
timestamp: January 05, 2022, 11:17:15 am
content: My input to the circuit will be a single wire video signal which goes to a CRT television.I will be taking in that video signal and multiply it to x1-x32 and change phase with respect to input signal at the same time.Thankyou in advance for help.

author: David Hess
author_rank: Super Contributor
timestamp: January 05, 2022, 12:48:50 pm
content: It will not work with a composite video signal, and I am not sure why it would be multiplied.

author: Kashif khan
author_rank: Contributor
timestamp: January 05, 2022, 01:31:52 pm
content: Can you recommend me some example circuits or some dedicated ICs which serves the purpose well. So i can multiply input frequency with turning variable pot.Thanks.

author: gf
author_rank: Super Contributor
timestamp: January 05, 2022, 02:57:16 pm
content: Do you want something likethis?While it may be possible to apply the same algorithms to a composite video signal, the result becomes useless.The result is no longer a valid video signal then, and a TV won't be able to show it correctly.

author: Kashif khan
author_rank: Contributor
timestamp: January 05, 2022, 03:44:13 pm
content: I want to design my own like the Picture attached. Hope the attachments make sense.

author: Bud
author_rank: Super Contributor
timestamp: January 05, 2022, 03:50:23 pm
content: Can you describe what you are trying yo achieve, what you expect the TV to display? Do you want a video stream with one monkey to put through this multiplier so the TV displays 32 monkeys?

author: Kashif khan
author_rank: Contributor
timestamp: January 05, 2022, 04:25:59 pm
content: Yeah exactly if i feed a circle shape or an ape to the circuit and set frequency multiplication to 32 then the TV will show 32 circles shapes/apes.is it possible to achieve what i need, by now you would have clearly understood what i need.

author: Bud
author_rank: Super Contributor
timestamp: January 05, 2022, 09:42:07 pm
content: Nope, never heard of such device.

author: ahbushnell
author_rank: Frequent Contributor
timestamp: January 06, 2022, 03:39:29 am
content: Is this a NTSC or PAL video signal. it won't work with digital.

author: Kashif khan
author_rank: Contributor
timestamp: January 06, 2022, 11:57:54 am
content: it is NTSC signal.(USA)
Do Radio Amateurs need Promotion or a Superhero - Page 1
Forum section: electronics / rf-microwave

author: jonovid
author_rank: Super Contributor
timestamp: December 29, 2021, 01:28:37 pm
content: the question is do radio amateurs need promotion?if a Superhero was a Radio Amateur would it fly?in need of an explanationI make animated videos for a hobbyI created the concept art for an animated cartoon for the promotion of amateur radio.inspired by a real life character in VK3the 1950s audio was also for or to be the intro in the video.but decided not to proceed further as im not a radio amateur.will no longer be making the video.IMO better served by their own. others better understand the demographic then I would.rather then let the concept art go to waste. I did post here.have fun if your an amateur and like cartoon superheros. say something for the kidsthe superhero that keeps radio bands free from interferencehere to fight for radio and the Amateurs key1950 fun with Radio Jingle re-mixedhttps://drive.google.com/file/d/1ITrHvw9lHdJNUvdrP34-coVwF05l89BI/view?usp=sharing

author: M0HZH
author_rank: Regular Contributor
timestamp: January 06, 2022, 04:37:51 pm
content: Superheroes appeal to kids and Amateur Radio is mostly a very aged demographic known for using ancient technology. Probably a McGyver-ish character that has the superpower to "hear" RF transmissions / communicate with any electronic device might work, in today's world there's plenty of opportunity there and Amateur Radio could be the overarching theme etc.
If you have the space isn't a full wave legnth best? - Page 1
Forum section: electronics / rf-microwave

author: Beamin
author_rank: Super Contributor
timestamp: January 01, 2022, 09:09:34 pm
content: I know bigger is not better but wouldnt full wave length be best for transmitting and receiving, assuming your SWR is right? I once heard that a 1/4 wavelength antenna is quieter for receiving but can't verify that. If you have space isn't fullwavelength best?

author: HB9EVI
author_rank: Frequent Contributor
timestamp: January 01, 2022, 09:24:48 pm
content: you cannot say much about quieter or noisier in relation to the physical length of an antenna. in today's world noise is mostly a matter where your antenna is situated; in most cases at most times QRM exceeds QRN, at least on short wave.what you have to focus on when comparing the length of the antenna related to the wavelength is the radiation pattern. A simulation will show you that the best

author: Whales
author_rank: Super Contributor
timestamp: January 01, 2022, 10:35:32 pm
content: Quote from: HB9EVI on January 01, 2022, 09:24:48 pm+1. A quarter wavelen whip or dipole has a different radiation pattern to a half wavelen, full wavelen, 2x wavelen, etc.This is only considering simple whip-style or dipole-style antennas. There are many designs much more complicated than those that don't have one component you can measure the length of and then guess/infer the performance anywhere as easily.
RF signal extractor comparator charging up - Page 1
Forum section: electronics / rf-microwave

author: cmorgan
author_rank: Newbie
timestamp: December 25, 2021, 02:18:33 am
content: I've got a comparator circuit used turn small voltage changes in an RF signal from an RF detector into digital outputs. In this case I'm trying to extract a 1Mhz signal out of the RF detectors. It's based on some circuits I've seen for others trying to extract ADSB singles.The circuit, attached here, works well except at times it stops working, I think because it charges up due to the diode, then after touching the circuit, in particular the diode side, or waiting a number of seconds, it starts working again.I tried to resolve by adding a resistor between the +/- of the comparator, say 100k or 200k, but this entirely breaks the functionality of the circuit that I'm testing here, although it works with LTspice.Thoughts on how to resolve?

author: w2aew
author_rank: Super Contributor
timestamp: January 05, 2022, 03:13:36 am
content: Quote from: cmorgan on December 25, 2021, 02:18:33 amCould be that the common mode voltage is going too high since you're not establishing a stable DC operating point for the inputs. The common mode input range goes from VSS to VDD-1.1V. Maybe a large resistor to ground at the common input point, like TP2 to ground.

author: cmorgan
author_rank: Newbie
timestamp: January 07, 2022, 03:46:00 pm
content: Hmm.We've got a 1M to ground, this is the circuit that feeds into the comparator attached below, sorry I should have included this with the other one.Would it help to measure the +/- into the comparator to see what is occurring there? That was one of the next ideas I had just to see what voltages were there (assuming the probes on those pins won't affect the voltage/capacitance enough to affect the circuit).Regards,Chris
HP's IAM-81008 - Active Mixer... But what about the datasheet pinning !? - Page 1
Forum section: electronics / rf-microwave

author: Uky
author_rank: Regular Contributor
timestamp: December 29, 2021, 06:13:02 pm
content: Greetings Forum,Planning a small project and having found a few HP IAM-81008 Active mixers.When it comes to the datasheets, both the one in my databook and those found on the internet.... I wonder if there is amismatchsomewhere: The "Pin Configuration" picture that shows the fp from above shows one pin description and the "Typical Biasing Configuretion"picture shows another. Another type, the IAM-82008 a few pages further on seems to have a proper pin description.Anyone that can shed some light on the -81008?
Agilent 83732B and 8657B Synthesized Gen - Page 1
Forum section: electronics / rf-microwave

author: jonpaul
author_rank: Super Contributor
timestamp: December 28, 2021, 01:06:47 pm
content: Agilent 83732B and 8657B Synthesized GenHello all looking at these fine units, to expand my lab capability to mm wave.My ancient HP 8640B is 1.024 GHz and a fine unit but showing its age....Your thoughts of comparison of 83732B and 8657B ?looking on ebay, any tips on potential faults, optionsMany thanksJon

author: wn1fju
author_rank: Frequent Contributor
timestamp: December 30, 2021, 02:34:28 am
content: Am I missing something here? The 8657B is a 2 GHz signal generator and the 83732B is a 20 GHz signal generator. There's a big difference between the two units. The 8657B is more or less a standard 1 GHz synthesizer with an internal doubler. The 83732B I am sure is packed with a lot of microwave goodies.Take a look at the data sheets of the two and compare modulation capabilities, phase noise, accuracy, harmonics, etc.Incidentally, in my 1997 HP catalog, the HP 8657B is priced at $14,200 (USD) with no options and the 83732B starts at $33,150.Also, you might get many more opinions by posting your question on the Test Equipment forum rather than the RF & Microwave forum.

author: max-bit
author_rank: Frequent Contributor
timestamp: January 01, 2022, 08:08:23 am
content: Perhaps the first and basic question is what funds do you want to spend on it?
Simple RF radio transmitter - ADF4351 - Page 1
Forum section: electronics / rf-microwave

author: bipolunipol
author_rank: Contributor
timestamp: December 27, 2021, 05:19:01 am
content: Hello!I would like to build a simple RF radio transmitter with the ADF4351 Development Board like:https://www.ebay.com/itm/35M-4-4GHz-PLL-RF-Signal-Source-Frequency-Synthesizer-ADF4351-Development-Board-/322520746831The transmitter will be used for quick testing of the work of the repaired receivers.The emitted wave should have the frequency set by this chip (mainly 2 - 3.5GHz). Without any modulation.I don't need a high power of the transmitter, let's say, for example, 6 mW.What could I do to build such a transmitter on a ADF4351 chip?Thanks

author: radiolistener
author_rank: Super Contributor
timestamp: December 27, 2021, 07:51:29 pm
content: you're needs to connect it with controller and write software to program ADF4351 registers for desired frequency.I think it will be easier for you to buy LTDZ:https://www.aliexpress.com/item/1005003086682197.htmlit has 2 x ADF4351, the mixer and STM32 controller on the board. You can use NWT software to control it.

author: bipolunipol
author_rank: Contributor
timestamp: December 27, 2021, 08:00:02 pm
content: Thank you!Do I need an output amplifier in this case? Is it enough to just connect the antenna?

author: radiolistener
author_rank: Super Contributor
timestamp: December 28, 2021, 06:42:49 pm
content: if you want to test receivers, it will be enough. No needs for amplifier, because it's output is about 0 dBm (0.22 Vrms). You may need to use some attenuator, because it's output may be too high for receiver input.yes, you can connect it to antenna. But be careful, if you use external antenna, static electricity from wind or high voltage pulse from lightning can damage it.
HP8712ET Hack - Page 1
Forum section: electronics / rf-microwave

author: Kraythorne
author_rank: Contributor
timestamp: December 24, 2021, 06:13:33 pm
content: Hi ThereI know that there is a firmware hack that enables the HP 8711C be upgraded to a full 8712C VNA by editing and reflaching the firmware and I am wondering if the same sort of hack is possible for the HP 8712ET ? For example, changing it to an 8714ET using a similar firmware hack?If so, is it worth it? what additional features would you get?Thanks

author: 0culus
author_rank: Super Contributor
timestamp: December 26, 2021, 03:15:23 pm
content: You might get more traction on the HPAK list or scalar and vector network analyzers list, both on groups.io.

author: TheSteve
author_rank: Unknown
timestamp: December 26, 2021, 06:04:56 pm
content: I do believe the hardware is different between 1.3 GHz and 3 GHz models, so there is no easy hack.

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: December 26, 2021, 07:28:13 pm
content: There is an easy hack. for the 8711, did not look up ET. I will attach it.It is the same for 8711 to 12 s it is from 8713 to 14.I did it. It works just fine and will give you all the options available. The options that need hardware of course are not upgradable without the hardware. So if you do not have the attenuator or the delay line, you will not get them with the hack.Here we go:

author: TheSteve
author_rank: Unknown
timestamp: December 26, 2021, 07:41:14 pm
content: The ET will already have the full VNA enabled. You can probably add some of the firmware options such as enabling the network port.