hybridfree/eevblog-posts huggingface dataset:
Antenna Manufacturers in India - Page 1
Forum section: electronics / rf-microwave

author: thelearner
author_rank: Contributor
timestamp: July 01, 2020, 08:50:55 am
content: Hello,I am working on a LoRa product and need an antenna for LoRa 865MHzI am looking for aHelical antennawith following specifications1. Gain = 3dBi2. VSWR = <23. Impedance = 50 Ohm4. Polarization = Linear5. Connector = Soldering6. RoHS CompliantCan anyone provide information about antenna manufacturers in India that produce helical antenna?TIARegardLearner

author: Lord of nothing
author_rank: Super Contributor
timestamp: July 03, 2020, 04:17:44 pm
content: Maybe building your own?For what Freq do you need such?

author: Neomys Sapiens
author_rank: Super Contributor
timestamp: July 03, 2020, 08:48:51 pm
content: When I had a requirement for a directional antenna with an unusual characteristic, the company given below surprised me with their unconventional solution, which was a horn antenna where the other responses either were monopoles with reflector and resonant director or (the classic solution suggested by textbooks for wide angle and smooth gain diagram) or short LPDAs.Their proposal was solid and they have experience with a very wide range of antenna types and applications. QM system with the usual certificates is in place.http://www.antennaexperts.in/

author: Lord of nothing
author_rank: Super Contributor
timestamp: July 03, 2020, 10:51:25 pm
content: Pls ask what the Sat come one:https://www.antennaexperts.in/product-detail.asp?cat=satcom-antenna&id=38cost.

author: mc172
author_rank: Frequent Contributor
timestamp: July 03, 2020, 11:17:23 pm
content: Quote from: thelearner on July 01, 2020, 08:50:55 amThose two requirements are contradictory.

author: profdc9
author_rank: Frequent Contributor
timestamp: July 05, 2020, 12:52:47 am
content: I think this depends on whether or not the helical antenna is many turns with the spacing between the coils being a quarter wavelength (axial-mode helical), or a very short monopole with linear polarization where the helix is just a distributed inductor used to cancel the capacitance of the short element (normal-mode helical). I think OP is looking for a normal-mode helical, however, typically the impedance of these are less than 50 ohms because the radiation resistance is reduced because of their shorter length. I don't think these are very difficult to design but the feedpoint impedance will be important depending on the LoRa chipset (e.g. SX1276 or such) and matching network. I think most manufacturers just tolerate the lower impedance but if you want to match the antenna more precisely a network should be designed (like a pi network) that matches the antenna's lower impedance.

author: eb4fbz
author_rank: Regular Contributor
timestamp: July 05, 2020, 02:26:39 pm
content: Quote from: mc172 on July 03, 2020, 11:17:23 pmNo, they are not. Normal or axial mode, endfire, backfire...
About an old RF Switch - Page 1
Forum section: electronics / rf-microwave

author: Joaquin
author_rank: Newbie
timestamp: July 03, 2020, 03:22:05 pm
content: 345/5000Regards from Spain:I am looking for any type of information about the handling of the Olektron RSV1202HF.It is a 12 x 2 RF switch managed via RS232, for more tests I do not manage, via telnet I get a response from it at 9600 Baud but everything ends there.Can someone guide me?Thanks in advance.Joaquin EA3IHPMore information: The inner RS232 Controller as the reference:32252-ASSY-9800-5075-3
Ku band BUC on 3cm - Page 1
Forum section: electronics / rf-microwave

author: geggi1
author_rank: Frequent Contributor
timestamp: June 30, 2020, 09:37:40 pm
content: Hi!Does anybody got any experiece modifying a Ku band BUK for the 3cm ham band.I got 2 of them a 4w unit and a 50w unit.If it si possible to convert one it would be a simpel start on 10Ghz.
433MHz PCB trace for Antenna - Page 1
Forum section: electronics / rf-microwave

author: maurosmartins
author_rank: Regular Contributor
timestamp: June 25, 2020, 09:45:34 am
content: Hello all,I've been playing around with LoRa related stuff (@434MHz) and I've layout some PCBs where I would like to clarify some doubts.On my first board (rectangular shape) the trace going out to the antenna connector has random width and clearance, nevertheless I had good results in terms of range with it.on my second board (the round one) I've decided to use a calculator (saturn PCB toolkit) to calculate the required width and clearance for 50Ohms impedance with the following results:afterwards I've soldered a 49.9Ohms smd resistor between the "ant" pad and GND on both boards and using a nanoVNA measured the s11 parameters with the following results:the blue trace is from the new board while the golden trace is from the old board, oddly it seems that the old random parameters worked better than the new ones.a more complete list of measures for the new board can be found on this image:In either case and since my RF related knowledge is not that great my questions are:Is this test valid, or should I make other setup to measure the RF impedance of the PCB trace.In case it is ok, are the values any good? I see that they are not a complete match to 50Ohms but they are very close to.The RF trace is very small maybe it isn't affected that much, what is your opinion?looking forward your reply,Best regards, Mauro.

author: schratterulrich
author_rank: Regular Contributor
timestamp: June 25, 2020, 10:06:16 am
content: I think the trace itself has the least impact on the result.-There are greater differences between the boards due to the different connectors.-There is a much shorter trace on the old board.-The new connector makes a via stub.-Also the GND return is somehow undefined - There are no nearby vias at the GND Pin to connect directly to the bottom GND plane, so there will be a undefined inductance...

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: June 25, 2020, 10:16:00 am
content: Your trace is so short it shouldn't really matter all that much.The free-space wavelength at 500 MHz is about 60 cm. Both of these traces are so short that the tolerance and variability easily accounts for the results you are seeing. The performance is just fine, I wouldn't worry about it too much.What I would worry about is that on your round PCB the trace goes underneath what i assume will be an SMD can or module. That could actually hurt performance, esp if there are metals on the bottom of that module.You also need a via near the ground of the lora module pin to connect ground pad to the ground plane

author: maurosmartins
author_rank: Regular Contributor
timestamp: June 25, 2020, 09:51:00 pm
content: Hello schratterulrich and TheUnnamedNewbie,thank you very much for your replies! in future revisions I'll add layer stitching to better connect GND on both layers. in the meanwhile I'm waiting for RFM98W modules so I can test the new boards.Best regards, Mauro.
How to build a 40dB or more attenuator up to 3GHz or more - Page 1
Forum section: electronics / rf-microwave

author: Tuxgvf33
author_rank: Newbie
timestamp: July 26, 2020, 01:00:09 pm
content: Hi all,I have tried to build an homebrew attenuator let's say a 40dB attenuator using online calculator.I used a 50ohm line and a pi structure with 2 resistor in parrallel at the input and the output.The result is poor as the smd component natural isolation is around 30dB (natural isolation of a 50ohm line ).Does anybody have any trick to improve the isolation to build high attenuator value? (As flat as possible not 0.1 dB but couples of db flatness around 40dB or greater will be a good start). I assume that it is not possible to build a 80 to 90dB attenuator in a single pi structure. I bet i need 2 attenuator of 40db cascadable.Many thanks,Regards

author: 9aplus
author_rank: Regular Contributor
timestamp: July 26, 2020, 02:35:01 pm
content: While ago I built something old fashion way, using switches and through hole resistors on perfboard.My goal was just to assist/test SDR reception on HF.One day while doing some tests on ADSB 1090 MHz freq. I was missing some more attenuation and used that device...all within acceptable results.My setup is 5 + 5 + 10 + 10 + 20 dB so all ON result is 50 dB it is not far from that numbereven on 1 GHz.

author: radiolistener
author_rank: Super Contributor
timestamp: July 27, 2020, 11:48:34 am
content: Quote from: Tuxgvf33 on July 26, 2020, 01:00:09 pm40 dB for a single cascade is too much. I suggest to use less than 10-20 dB per cascade.And use proper shielding, for 40-60 dB and higher it is very important.

author: ejeffrey
author_rank: Super Contributor
timestamp: July 27, 2020, 08:36:19 pm
content: Is this to use on a PCB? What power handling? Mini-circuits, Susumu, and probably others make surface mount attenuators. For low power applications these will perform much better than trying to make one out of discrete components. Don't do more than 20 dB/stage, and do use shielding, I try to keep no more than 40 dB of attenuation or gain without shielding.

author: RadioNerd
author_rank: Regular Contributor
timestamp: July 28, 2020, 11:10:40 am
content: how about four of these?https://www.susumu.co.jp/common/pdf/n_catalog_partition30_en.pdf?v=20180406you'll certainly get better performance than using discrete resistor arrangements

author: djidji
author_rank: Newbie
timestamp: August 03, 2020, 11:50:24 pm
content: don't waste your time and money. you will never ever DIY any decent 3GHz attenuator especially not the cheap one. better go to the some online e-commerce website and buy real RF attenuator for a fraction of the money what would you spent on DIY.
Is 7.023 MHz a popular QRP frequency in China? - Page 1
Forum section: electronics / rf-microwave

author: rhb
author_rank: Super Contributor
timestamp: June 19, 2020, 07:37:17 pm
content: There are numerous cheap kits for CW rigs using VXOs around 7.023 MHz on ebay. In the US that's an extra class only frequency.What is the structure of licensing and frequencies of operation in China? Is 7.023 usable by entry level A class licensees? If so, it suggests the kits are mostly intended for domestic sale in China.Have Fun!Reg

author: radiolistener
author_rank: Super Contributor
timestamp: June 19, 2020, 08:28:59 pm
content: Just found this doc:https://www.ncc.gov.tw/english/files/07060/92_070605_1.pdfQuote

author: rhb
author_rank: Super Contributor
timestamp: June 19, 2020, 09:22:43 pm
content: That's the basic ITU allocation. Doesn't say anything about classes of license. From what I found the licenses classes seem to be strictly PEP related.I'm hoping that a Chinese ham will clarify.Reg
Alinco DR-11 C1 repeater shift help needed. - Page 1
Forum section: electronics / rf-microwave

author: christopher iles
author_rank: Regular Contributor
timestamp: June 16, 2020, 08:29:09 am
content: Hello,I have an Alinco DR-11 C1 2 metre fm transceiver which works fine except that the repeater shift is around -5MHz!Does anyone know how to change this to -600KHz?I've trawled the internet but there is very little information on this radio; maybe not many were made.Any help greatly appreciated.Very kind regards,Chris, G0VOE. Somerset.
Yaesu FT-5100 - Page 1
Forum section: electronics / rf-microwave

author: christopher iles
author_rank: Regular Contributor
timestamp: June 16, 2020, 08:23:29 am
content: Hello,The display driver has packed in on my ft-5100. I was wondering if anyone may have a surplus to requirements donor radio for sale so I can get the old faithful back to normal again.Very kind regards,Chris, G0VOE. Somerset.
AM detector in modern car radios - Page 1
Forum section: electronics / rf-microwave

author: Circlotron
author_rank: Super Contributor
timestamp: June 18, 2020, 06:55:21 am
content: I've been wrestling lately with a 1940s valve radio, trying to get the detector circuit work better. It was good enough back in the day, but nowadays every AM station uses volume compression to get the average loudness higher and old timey AM detectors don't always take kindly to high modulation indexes. Once you start getting past 50% things get a bit nonlinear. Anyway, during all this I grabbed a car radio that I bought about 10 years ago and applied a 100% modulated signal to it and it handled it just fine! So... the question is, what do these modern sets use for an AM detector? Likely it's all inside a big IC, but what is the details of the detector to get such good performance?

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: June 18, 2020, 09:24:01 am
content: I'm not sure but I would imagine some kind of DSP for the radio. Might depend on the brand.

author: Circlotron
author_rank: Super Contributor
timestamp: June 18, 2020, 11:44:46 am
content: It’s a Kenwood KDC-U349R.Just found a service manual!https://www.manualslib.com/products/Kenwood-Kdc-U349r-5129552.html

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 18, 2020, 11:59:47 am
content: Could be lack of bias current in the detector. Depends on type. If it's diodes hugging a common cathode (e.g. 6AV6), there may be some built in bias which cuts it off at small signal, or conversely maybe it's prebiased and should perform pretty well. If it's something like a grid leak detector, depends on the grid conductance and biasing. AVC response may be slow or nonlinear, again depends on things. If it's a regenerative receiver, meh, it's just not very good to begin with, heh...And yeah, modern sets can put a whole ass SDR in there and not care. Don't know if they do...Tim

author: CaptDon
author_rank: Super Contributor
timestamp: June 19, 2020, 01:58:24 pm
content: I worked in commercial broadcast for many years. Our GatesMW-5 was typically doing 98% negative with 110% forwardbeing driven by the normal Optimod-AM which itself wasdownstream of a CBS Laboratories Level Devil. I have listenedto the over-exaggerated audio on tons of radios includingfloor models from the 20's and 30's and never heard 'bad'audio from any radio unless the radio had a malfunction.As for AM detectors, Steve WD8DAS (he has a website)has dabbled in many different detectors and was sellingkits to update old SWL and Ham receivers. Maybe lookaround his website for some info. He was a chief engineerfor an AM/FM outlet where I worked.
WTB: Yaesu FT-707 switch bezel - Page 1
Forum section: electronics / rf-microwave

author: christopher iles
author_rank: Regular Contributor
timestamp: June 16, 2020, 08:19:40 am
content: Hello,I'm looking for a little black square plastic switch bezel (the ones that go in the seven square holes on the front panel).If you have one that would be great.Also, I am interested in any FT-707 parts, broken rigs, anything really.Thank you for looking, please reply if you can help.Very kind regards,Chris, G0VOE. Somerset.
toroids 42 material  - Page 1
Forum section: electronics / rf-microwave

author: salviador
author_rank: Regular Contributor
timestamp: June 14, 2020, 01:25:32 pm
content: where can i find toroids with material 42?I can't find anywhere. Do you know any retailers?

author: geggi1
author_rank: Frequent Contributor
timestamp: June 14, 2020, 02:46:44 pm
content: This is a low frequency core.I would consider using a core meant for switching power supplies.There are a lot of manufacturers that are making cores for power suppies from the small 1w supplies to multiple kW supplies.
Experience with the Infineon Sense2GoL? (Radar Demo Board) - Page 1
Forum section: electronics / rf-microwave

author: Lord of nothing
author_rank: Super Contributor
timestamp: June 13, 2020, 09:56:30 pm
content: https://www.infineon.com/cms/en/product/promopages/makeradar/applications-and-devices/sense2gol-devkit/Does anyone here play with that?Thanks
Cylindrical cavity resonator for Oscillator - Page 1
Forum section: electronics / rf-microwave

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: May 31, 2020, 11:54:41 am
content: I want to make an oscillator using a cylindrical cavity as resonant element. Anyone have any pointers on how to start this? I want to use en existing cavity (a drinks can) as this is to be a kind of 'RF/electrical engineering magic demonstrator' for educational purposes.

author: retrolefty
author_rank: Super Contributor
timestamp: May 31, 2020, 12:02:54 pm
content: It would be helpful to know the operating frequency you would like to demonstrate at. VHF needs much larger size then UHF.

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: May 31, 2020, 01:00:41 pm
content: As I already stated, I will be using a drinks can as resonator. These have a dimension of about 66mm x 115 mm.After some research I've found that this should have a resonant mode around 2.6 GHz, which is what I will start my idea on. I will do some simulation to figure out more of what is going on, but was hoping I could get some tips as to feeding structures or how to optimally do this (EG, is it best to use 1-port impedance as resonant tank, or use 2-port resonace as feedback network?)

author: RoGeorge
author_rank: Super Contributor
timestamp: May 31, 2020, 01:36:40 pm
content: From Google, not exactly an oscillator, but has plenty of cylindrical cavity:https://pdfs.semanticscholar.org/56a0/6962022a7d2b17414f52180440f96308f2d7.pdf

author: CaptDon
author_rank: Super Contributor
timestamp: June 02, 2020, 01:46:23 am
content: 2.6 gig sounds very high for that dimension. I have seenold WWII cavity resonators with a 2C40 lighthouse triodesmaller than your can and resonant around 1.1 gig. Thesize of the can seems like an old 450mhz band pass filter.

author: geggi1
author_rank: Frequent Contributor
timestamp: June 10, 2020, 02:16:02 pm
content: Have a look at this one.http://85.226.112.143/use/resonator_1.htmAs the feirst resonance is at 1/4 wave lenght your first resonance will be in the area of about 652Mhz [ 300/(4*0,115)] but there can be harmonics at other ferquencies typical 3rd (1956Mhz) and 5th (3260Mhz).To get a resonance in the 2,6 Ghz area your resonating pin must be about 28mm.The calculation you have done is for a full wavelength resonator that is the 4th harmonic. You will get your first harmonic on 1/4wl. normaly the 4th harmonic has a lower value. The most dominant is normaly the odd order 1th, 3rd, 5th, 7th.https://www.ahsystems.com/EMC-formulas-equations/frequency-wavelength-calculator.phpI did a test of rezonanse wit a T-connector, 0,5l drink can (abt. 200mm hight), a 150mm teflon coated wire and the DSA815TG and found a sharp resonanse at 390Mhz or there about. It is some time ago and I can not remember the exsact lenghts.
SAQ transmission today, july 1 - Page 1
Forum section: electronics / rf-microwave

author: Martin.M
author_rank: Frequent Contributor
timestamp: July 01, 2018, 05:11:42 am
content: SAQ . 17,2kHz cw1. Juli1. Startup of tuning at 10:15 (08:15 UTC) with a transmission of a message at 10:45 (08:45 UTC).2. Startup of tuning at 12:15 (10:15 UTC) with a transmission of a message at 12:45 (10:45 UTC)3. Startup of tuning at 14:15 (12:15 UTC) with a transmission of a message at 14:45 (12:45 UTC)at tuning the frequency will go up and down, of coarse they have no crystals there.take a look to your personally time zone. Good luckgreetingsMartin

author: Henrik_V
author_rank: Regular Contributor
timestamp: June 10, 2020, 08:59:07 am
content: next transmission July 5th 2020https://alexander.n.se/alexanderson-day-2020/?lang=en
GNSS LNA  - Page 1
Forum section: electronics / rf-microwave

author: thelearner
author_rank: Contributor
timestamp: June 09, 2020, 09:28:40 am
content: Hello,In the GNSS receiver path, the power supply is connected to the LNA (BGA524N6) VCC pin and also to the RF output pin. I am using a passive antenna.Why do we need to connect the power supply to the RF output pin?What is the logic behind it?TIA

author: rf-messkopf
author_rank: Regular Contributor
timestamp: June 09, 2020, 10:25:42 am
content: Quote from: thelearner on June 09, 2020, 09:28:40 amThe supply voltage is actually not connected to the RF input of U8 since there is a DC blocking capacitor in between. The supply voltage can, however, be switched to the ANT_GNSS jack by means of U6, U9, and the signal RFSW2-V1 or LNA_CTRL_MCU, presumably to power an external LNA.
UHF DRM Android Radio? - Page 1
Forum section: electronics / rf-microwave

author: Lord of nothing
author_rank: Super Contributor
timestamp: June 07, 2020, 10:51:35 pm
content: HiDoes anyone here use a UHF DMR Radio with Android?The question is if there a Radio/ Smartphone on the Market who support that I put in a Freq, Radio ID,.. and the other fun little thinks on the fly without the need of a Pc or Laptop.I have a TYT MD390 who is nice but the suck when it come to change anything.Suche the Accu must be replaceable. I found a promessing one but I dont know if the is good enough or not.Thanks

author: NiHaoMike
author_rank: Super Contributor
timestamp: June 08, 2020, 03:47:25 am
content: The Doogee S80 supports DMR.There's an attempt to reverse engineer it but it hasn't gotten very far.https://github.com/travisgoodspeed/s80tools/wiki

author: Lord of nothing
author_rank: Super Contributor
timestamp: June 08, 2020, 12:39:24 pm
content: Well I thought about that:https://boxchiptt.com/products/smart-mission-critical-communication?variant=2568694333467+ "Using the code: USD101 you will get a discount of $100.00USD on your purchase"I found other Website who are 100€ below that maybe the are not a serious one.I find the feature good who is a Gateway between a Push to Talk over Cellular and a DMR.I hope the work with a Mumble Client to.
Help required with University paper (Trigonometry / Satellites) - Page 1
Forum section: electronics / rf-microwave

author: Halcyon
author_rank: Unknown
timestamp: May 29, 2020, 04:31:58 am
content: I hate asking for help with assignments but this one has me absolutely stumped since my maths skills aren't strong and I've bitten off more than I can chew.If any of you wonderful people have the time over the next few days to assist me with a University paper in relation to satellite orbits and the maths behind the RF itself, there is a case of beer (or beverage of your choice) in it for you. Alternatively, we can come to some kind of other arrangement.If you have some spare time and wouldn't mind assisting, please PM me and we'll talk one-on-one.

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: May 29, 2020, 06:53:44 am
content: Why not just put the information out here so everyone interested can help?

author: Halcyon
author_rank: Unknown
timestamp: May 29, 2020, 08:12:18 am
content: Quote from: TheUnnamedNewbie on May 29, 2020, 06:53:44 amI thought about that but the content is copyrighted by the university, so I'm not allowed to reproduce or publicise it.Also, because the questions/answers are changed slightly for each semester. Based on the questions, they could determine which group of people it came from. Not something I want to deal with. They deliberately put those "markers" in so they can be somewhat traced.

author: vk4ffab
author_rank: Frequent Contributor
timestamp: May 30, 2020, 09:27:44 am
content: Quote from: Halcyon on May 29, 2020, 08:12:18 amWhat is the actual math you do not understand? No one is going to show you HOW to work it all out, but we will happily help you UNDERSTAND the math you do not. We can explain processes and you can do then do your assignment.

author: Halcyon
author_rank: Unknown
timestamp: June 07, 2020, 06:52:54 am
content: Here is one I can share...The math confuses the crap out of me.
ID this receiver - Page 1
Forum section: electronics / rf-microwave

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: June 06, 2020, 08:31:09 pm
content: Found this in my junk. Yes I hoard...It must be more than 30 years old.It is obviously a pretty good analog receiver for a 27MHz RC toy. But what is confusing is why it's a module, why it has screw holes, and why the crystal is removable.It isn't the usual all-in-one toy RC PCB but I don't quite recognize it as the usual "pro" Futaba-ish RC radio receiver of the 1980s/1990s analog era either.Anyone ever seen something like this? What does it come from? It has no markings on the case or the PCB.The transistor that is at the antenna is marked 901 with some squiggle. It's cool, but I don't recognize it. A 2SK901 is a power MOSFET.I might power it up later but I'm in the middle of "sort and decide to junk" of all my ridiculous boxes of nonsense.

author: themadhippy
author_rank: Super Contributor
timestamp: June 06, 2020, 09:02:34 pm
content: Quoteso you can switch to another frequency easily.In the uk the crystals were colour coded and you'd put similar coloured flag on your aerial so other users could see at a glance what frequency's were being used.
Is Comm. with RF95 modules possible witout LoRa network?  - Page 1
Forum section: electronics / rf-microwave

author: MaiMariarti
author_rank: Newbie
timestamp: June 03, 2020, 01:39:44 pm
content: Hellooooo;Just found 5x RF95 modules I thought I lost 2 years ago.I bought them to get into LoRa, then lost interest and lost these at the back of a drawer.Can I use 2 of them to communicate with each other without the LoRa network or any other gateway middleman?Like a regular point-to-point transceiver?Thanks in advance for your input and any links that might answer this in deatil.

author: georges80
author_rank: Frequent Contributor
timestamp: June 03, 2020, 07:04:21 pm
content: Yes, the radios can talk point to point without an underlying lora network. You of course need more than just the radios. You'll need a host processor (I use an STM32Fxxx) and load appropriate software to deal with all of the comms. It's not a small task...cheers,george.

author: gregger2k
author_rank: Newbie
timestamp: June 06, 2020, 04:17:26 am
content: Check out the RadioHead libraryhttps://www.airspayce.com/mikem/arduino/RadioHead/I am doing a project with RF95's using Reliable Datagrams and it is working well.Greg
868MHz LNA matching, Skyworks SKY66420 - Page 1
Forum section: electronics / rf-microwave

author: Peter_SB
author_rank: Newbie
timestamp: February 06, 2020, 02:48:19 pm
content: Hello everyone,I am building a ISM 860-872MHz receiver for LoRa application. As a LNA I am using Skyworks SKY66420 front end.I tried to measure the return loss from the input connector, and it is not impressive, I am not sure where those fluctuation in the passband come from. If I terminate the RF path with 50Ohm resistor just before the LNA input the fluctuations disappear so I would assume it is because the LNA is not matched correctly, but there is no information about its input impedance. Also I don't think I am getting the +18dB of gain.So to describe what I did better:My schematic looks like this:It is very similar to skyworks ref design. X4 SMA connector is my input connector. I've put a SAW filter between RX_FILT and LNA_IN.When I connect the VNA to the SMA connector I get the following return loss:And when I measured with Spectrum Analyzer with tracking generator the gain I get from the output of the LNA (the input signal is -80dBm) I get something around 12dB from 18dB advertised.Can anyone help?

author: Gerhard_dk4xp
author_rank: Frequent Contributor
timestamp: February 06, 2020, 05:10:11 pm
content: Good input return loss of an LNA is absolutely unusual.Noise matching has not much to do with power matching.cheers, Gerhard

author: Peter_SB
author_rank: Newbie
timestamp: February 06, 2020, 06:02:03 pm
content: Yes this is true, you can optimize amplifier for noise figure or power output or efficiency but usually you can't have everything. But datasheet promises 18dB gain and antenna port return loss of -12dB and I am not getting close to it. I suspect some impedance mismatch, this LNA should be already matched to 50Ohm so need to do more measurements.

author: virtualparticles
author_rank: Regular Contributor
timestamp: June 04, 2020, 09:12:28 pm
content: I see that you have trace rules between your filter components. Making these traces 50 ohm lines is not at all optimal. The traces have parasitic inductance and capacitance which must be accounted for in the filter path. The inductance will always be about 25 nH per inch and the capacitance per unit length will vary with the width of the trace and its separation from the ground plane beneath it. Always use a trace that is as skinny as you can get away with. This will reduce the parasitic capacitance. You'll have to factor in the inductance or keep the lines really short.Cheers,Brian
Knob Wanted! (Trio TR-2300). Kindly donated by Paul, thank you! - Page 1
Forum section: electronics / rf-microwave

author: christopher iles
author_rank: Regular Contributor
timestamp: May 19, 2020, 10:52:21 am
content: Hello,Have you got a volume or squelch knob for a Trio TR-2300 please?Kind regards,Chris, G0VOE.

author: m3vuv
author_rank: Super Contributor
timestamp: May 20, 2020, 09:12:30 am
content: hi chris,ive some knobs on an old scrap tr-9000,would they fit?,cheers Paul m3vuv.

author: christopher iles
author_rank: Regular Contributor
timestamp: May 21, 2020, 08:11:51 am
content: Hello Paul,Thank you very much for your reply. I am sure that some of the TR-9000 knobs are virtually identical so should fit.The shafts on the TR-2300 are all 1/4" diameter.I have just finished replacing the synthesiser on the '2300 with an old CB one (MC145106) and now have 12.5 KHz spacing and it works great.I have changed the meter and dial lamps to l.e.d. reducing current drain when on batteriesThe CTCSS board is also in now so basically the rig is now up to modern standards.Been a bit fiddly, but fun to do and IT WORKS!Just the missing knob that spoils it now.Kind regards,Chris. G0VOE.

author: m3vuv
author_rank: Super Contributor
timestamp: May 21, 2020, 12:46:15 pm
content: i will post a couple on sat chris ok

author: christopher iles
author_rank: Regular Contributor
timestamp: May 22, 2020, 06:08:09 am
content: Hi Paul,Thanks ever so much, that's really kind.Should you ever get stuck for a part, I will be more than happy to return the favour if I can.My address:Moon Cottage,2,Mountview Terrace,Pawlett,Somerset.TA6 4SL.If you put your address on I will refund the postage to you.Thanks again and kind regards,Chris, G0VOE.

author: m3vuv
author_rank: Super Contributor
timestamp: May 25, 2020, 03:04:42 pm
content: they are ready to post in the morning.

author: m3vuv
author_rank: Super Contributor
timestamp: May 28, 2020, 02:23:42 am
content: posted yesterday royal mail 1st class ok.

author: m3vuv
author_rank: Super Contributor
timestamp: June 03, 2020, 05:53:36 am
content: have you received them yet?
Strange beat note against WWV 5mhz and 10mhz - Page 1
Forum section: electronics / rf-microwave

author: CaptDon
author_rank: Super Contributor
timestamp: May 31, 2020, 11:42:21 pm
content: Anyone else got a signal about 20hz away from WWVon their 5mhz and 10 mhz signals?? My 15mhz is clearwith no problem. The signal is not generated within myhousehold. I have three railroads close to me with allkinds of wayside signalling gear. Haven't gone lookingyet, but perhaps something coming from them?

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: June 01, 2020, 11:21:58 am
content: Capt:I do not see anything with 3 or 10 Hz resolution. 10 Hz per division. I looked at 5 and 10 MHz.Nothing 20 Hz from the signals. Signals look pretty clear and are strong.There are lots of RR lines and switching stuff near here also.Wally

author: radiogeek381
author_rank: Regular Contributor
timestamp: June 01, 2020, 05:07:50 pm
content: I see signals near WWV all the time. Some come from 10MHz reference oscillators in the room. Network adapters, appliances with crystal driven clocks. One of the radios in the shack has a synthesizer whose coarse ref freq is 10MHz. If I don't lock that one, it can beat with WWV.What kind of radio are you using?

author: CaptDon
author_rank: Super Contributor
timestamp: June 01, 2020, 08:57:01 pm
content: The receiver is a Kenwood TS-690S. I think the internal ref oscillatoris 4mhz. If I remember correctly, the guy I bought the radio frompaid a little extra to have the TCXO installed as opposed to the plainvanilla oscillator in a can they normally ship with. When calibrating mybench counters and AFG units I have been using beat notes againstthe 15mhz WWV as there is no interfering signal near it and I receivethe 15mhz signal around S9 during the mid afternoon. I switch the receiverto CW mode giving me a 700hz tone then zero beat against that toneto calibrate my bench test gear. I do have a double oven military 10mhzTCXO that is always on. The daily drift is about 1 cycle in ten secondsor 1 part in 100,000,000. I could tweak the trimmer for less drift butit is fine as is, close enough for what I need.

author: 0culus
author_rank: Super Contributor
timestamp: June 02, 2020, 03:22:47 am
content: Bet you have a local source of 5 or 10 MHz from your equipment. I've had this happen in my lab due to using a poor quality coax to connect the GPSDO to the distribution amplifier. Replaced it and the stray 10 MHz tone went away.
A Christmas Tranceiver - Page 1
Forum section: electronics / rf-microwave

author: vk4ffab
author_rank: Frequent Contributor
timestamp: May 30, 2020, 05:36:33 am
content: I added some paint to something I have been working on for a while now and if you squint slightly and imagine some snowflakes my little red transceiver will look very Christmas indeed LOL

author: vk6zgo
author_rank: Super Contributor
timestamp: May 30, 2020, 06:39:11 am
content: Quote from: vk4ffab on May 30, 2020, 05:36:33 amYes, very festive!When you finally get everything going "just so", you'll think it's Christmas!

author: vk4ffab
author_rank: Frequent Contributor
timestamp: May 30, 2020, 07:55:17 am
content: Quote from: vk6zgo on May 30, 2020, 06:39:11 amyeah i know, I have a new revision of the receiver board coming next week, hopefully i will have fixed the its deaf as a door knob issues and it should be good to go. the TX works fine, just needs the spit and polish on the RX to make it all happen.

author: Lord of nothing
author_rank: Super Contributor
timestamp: May 30, 2020, 04:42:09 pm
content: The red colour look like more a Dooms day device!
Chip antenna on ground - Page 1
Forum section: electronics / rf-microwave

author: blueskull
author_rank: Unknown
timestamp: May 29, 2020, 02:27:36 am
content: Is there a solution to put an 2.4G antenna on top of a solid ground plane? So far I've been designing with 2450AT42E0100, which is globally in short supply, so I need another solution.I know Taoglas has their SWLP2450 series ceramic antenna blocks, but I can't accept their sizes either. Something like 2mm*5mm is good, maybe I can stretch to 2.5mm*8mm, but that's it.I'm experimenting on common antennas+RF absorbing sheet on bottom side, but as I'm waiting for parts, it will be days before I can confirm the results.

author: ThomasDK
author_rank: Regular Contributor
timestamp: May 29, 2020, 12:12:51 pm
content: Look at the PIFAs from ProAnt. They are larger than 8x2, but you can place components below them.
LTE Cat4 and Cat1 Comparison - Energy requirement? - Page 1
Forum section: electronics / rf-microwave

author: marinelad
author_rank: Newbie
timestamp: May 25, 2020, 07:23:24 pm
content: I'm looking to make the jump from 3G to LTE over the summer for a fleet of data buoys. For the datarates I need (4-10MB/hour transmit every 15-30 minutes) I think that LTE Cat1 makes the most sense for me from a cost and power standpoint. Cat4 is also an option, but seems like a hammer to kill an ant. What interests me is that the Cat1 chipset I'm considering is rated to 5Mb/s for UL while Cat4 is rated to 50Mb/s. The peak transmit power of cat4 over cat1 is just ~20% more.If it takes 1/10th the time to transmit the same (fixed) payload at 20% more power, wouldn't this result in an 88% power savings per byte?Assumptions in this statement are:1) same TX power in dBm is required to get a given message out for a given location/time/weather condition.2) The modem can be turned off between transmits - the dominant power draw is in xmit mode. I'm not aware of network restrictions requiring me to stay continuously connected in my region, but that would be an obstacle if any such restrictions existed.The specific chipsets in questions are the ublox LARA-R2 and TOBY-L2 series.
Post some pictures of your vintage ham radio equipment - Page 1
Forum section: electronics / rf-microwave

author: joeqsmith
author_rank: Super Contributor
timestamp: May 23, 2020, 03:38:17 pm
content: While I had my old radio apart, I thought I would take a few pictures of it. Some of the parts used are mechanically complex.I am the third owner of it. The original owner had passed away and his wife sold it to a friend of mine in non working condition. I ended up doing the repairs and alignment but it's never been on the air since. It's basically all original and still operational.Do you still have/use an old tube type radio? Let's see some pictures and hear some details about yours.
SSMCX cable needed - Page 1
Forum section: electronics / rf-microwave

author: w2hx
author_rank: Contributor
timestamp: May 18, 2020, 11:42:20 pm
content: Hello friends,I am not completely sure if this is the right/best forum for me to post my question. Ok, real long shot, here goes.I am in need of a cable a few inches long at least with a right-angle ssmcx connector on one end and something more "normal" on the other end. Dont care what, but like sma/3.5 for example. It is just for troubleshooting, so I just need to mate with the other end and cable quality is unimportant.Here is the picture of the kind of cable I need. The side on the ruler is this SSMCX connector (I believe, please correct me if I am wrong!)https://w2hx.com/x/Harris/RF-310M-HH/Repair%20Pix/0518201908a.jpgAs for the gender, I am not sure what it is called. The cable connector fits within the connector on the board that I am trying to mate with. Is it male? However the center of this cable connector has a tiny socket for a tiny pin to go into. So is it female? Maybe female?here is a picture of what I need to mate with on the pcbhttps://w2hx.com/x/Harris/RF-310M-HH/Repair%20Pix/0518202023a.jpgI am located in the USA and will gladly pay for the cable and postage from anywhere in the world. Any help greatly appreciated! Also interested if anyone can suggest another forum for me to ask for help would also be appreciated.Thank you73 Eugene W2HX

author: Gribo
author_rank: Frequent Contributor
timestamp: May 21, 2020, 07:27:46 pm
content: Digikey carries some molex PNs and cable assemblies.https://www.digikey.com/en/product-highlight/m/molex/ssmcx-coaxial-rf-connectorsMeasure the outer diameter, it might not be SMMCX.

author: w2hx
author_rank: Contributor
timestamp: May 21, 2020, 07:29:27 pm
content: Thank you for the reply. As it ends up, I think you are right. At this point I believe this is an SMP connector. I have ordered a mating cable so in a few days I will know for sure.thank you!73 Eugene W2HX
Odd data signal - Page 1
Forum section: electronics / rf-microwave

author: veedub565
author_rank: Frequent Contributor
timestamp: May 23, 2020, 11:51:21 am
content: I'm picking up a data signal around 14274.0 (20m band) in the UK. Been trying to work out what it is. I've attached a picture of the waterfall in FLdigi

author: veedub565
author_rank: Frequent Contributor
timestamp: May 23, 2020, 11:54:25 am
content: And in Sorcerer (14272.2)

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: May 23, 2020, 12:16:09 pm
content: I mean it is kinda impossible to say what it is just by looking at a plot. Any half-decent modulation scheme will have a pretty flat spectral response.I would ask to add units to your frequencies. I'm gonna take a while guess that 14272.2 was in kHz, since 10 MHz is about 30m wavelength. Could be lots of things I guess.

author: veedub565
author_rank: Frequent Contributor
timestamp: May 23, 2020, 12:24:14 pm
content: Yeah frequencies are in khz 14272.2khz and 14274.0khz so it's in the 20m HF bandI tried to upload an audio recording but the site won't allow it.

author: m3vuv
author_rank: Super Contributor
timestamp: May 23, 2020, 01:51:53 pm
content: is it one of those 5g death rays? lol

author: veedub565
author_rank: Frequent Contributor
timestamp: May 23, 2020, 04:46:01 pm
content: They give you Coronavirus those 5G masts, I stay away from them
So, a rash and crazy purchase, or a jewel of a 2 metre amp in the making? - Page 1
Forum section: electronics / rf-microwave

author: Chris Wilson
author_rank: Super Contributor
timestamp: May 18, 2020, 11:48:13 pm
content: I would normally have been in the pub, not buying stuff I almost certainly do not need off the Internet, but the hostelries are shut down here in the UK because of the Corona Virus outbreak. Whatever, my finger stopped wavering and hovering and a last moment bid was made resulting in this obvious, if incomplete, labour of love by a German ham, now sadly deceased, becoming mine. A two tube, 2 metre amp using a pair of G17B's with internal PSU.I have not picked it up yet, but would welcome any comments as to whether it may have been from a known design, or, if as I suspect, it was a unique but unfinished labour of love by a gentleman with excellent machine shop skills and a desire to produce something of shiny machined alloy beauty? Will it ever work, or will I be left with an ornament that will become testament to too much time on my hands browsing web sites during the virus lock down?The 11 photos can be seen in the Zip file athttp://www.chriswilson.tv/2m-amp.zip

author: M0HZH
author_rank: Regular Contributor
timestamp: May 19, 2020, 12:06:33 am
content: Those are almost certainly GI-7B tubes, good for about 250W each. Very popular russian triode about 20 years ago (probably due to a large volume of Cold War new old stock being dumped in the market), the internet is full of designs using them. Looks like the guy most likely removed the standard anode heatsinks (or used the GI-70B version that comes without heatsinks) and used his own.

author: Nuno_pt
author_rank: Frequent Contributor
timestamp: May 19, 2020, 02:58:18 am
content: Well, they are GI7b with a modified heatsink, soon as I put my eyes on the schematic, I saw that I recognize that drawing, it's made by YU1AW you can see that particular on here <https://www.qsl.net/yu1aw/VHF_PA/shema%202xGI7B%202m%20LB.gif> or more from here <https://www.qsl.net/yu1aw/Misc/engl.htm>

author: Chris Wilson
author_rank: Super Contributor
timestamp: May 21, 2020, 02:07:54 pm
content: They are definitely GI7B valves with the stock anode coolers removed and a complex custom one made and fitted. The amp came with some documentation suggesting the deceased builder might have been one Peter Jacobs DK2EU. There is no built safety circuitry in it, but there are some components like switches and LED's that seem to have been added to work with safety stuff. I may use a commercial triode safety board, I have some unbuilt ones from GM3SEK :http://www.ifwtech.co.uk/g3sek/boards/triode/triode-1.htmThanks for the replies.
Shielding against C band interference - Page 1
Forum section: electronics / rf-microwave

author: 1alan1
author_rank: Newbie
timestamp: May 19, 2020, 03:59:09 am
content: We are having issues with 5G interference on a C - Band down link. I moved the antenna around and found the direction with the highest level of interference. On the roof I see two sets of antennas within 200 yards in the same direction. Not sure they are both 5G but pretty sure one of them is. This problem popped up last year. The dishes are fiberglass and installed years ago. I suspect they are not designed to operate in this environment.So I am looking into some ways to try to mitigate this interference. I have a couple of ideas and wanted to have someone give me their opinions and or ideas how to deal with this if possible. Another guy I work with it looking into filtering.At the moment I am looking at possibly installing a grounded mesh next to a couple of our dishes. I am also considering if its possible to install a grounded mesh on the back and sides of the dishes. Or a combination of both. I am pretty sure I will not be able to block it completely, but if I could knock it down a ways might work.Thanks!!

author: Ian.M
author_rank: Super Contributor
timestamp: May 19, 2020, 05:46:43 am
content: https://www.fcc.gov/reports-research/guides/interference-complaintsWhile you are witing for the bureaucracy, you could try spraying the backs of the dishes with nickel EMI screening paint, then overcoat it when fully dry and cured with clear auto lacquer for weather protection. Do a small test panel first to check the lacquer is compatible with the nickel paint - its thinners mustn't redissolve the paint as any extra resin between the nickel particles will drastically reduce its conductivity and thus screening effectiveness. Don't get any nickel paint on the dish faces or LNBs.

author: 1alan1
author_rank: Newbie
timestamp: May 19, 2020, 06:11:58 am
content: Ian.M,Interesting Idea. I never looked into any coatings. I will run this up through management and see what they say.Thanks!!Alan
RF probe results - Page 1
Forum section: electronics / rf-microwave

author: profdc9
author_rank: Frequent Contributor
timestamp: May 17, 2020, 10:41:25 pm
content: I have tried out my RF probe and it seems to be working ok. Here's the gain curve I just measured with the spectrum analyzer I received today (D6 JTGP-1033).I had to make a couple of component changes, but I think it's turning out pretty good. It's based on the 2SC3356 transistor. It has about 3 dB gain in the passband and a -3 dB frequency at 1.25 GHz, which was better than I was expecting. I had to add couple of 22 ohm resistors to damp oscillations but it seems to work anyways.Dan

author: StillTrying
author_rank: Super Contributor
timestamp: May 18, 2020, 12:46:58 am
content: I don't get why you post little bits of useful info on the same probe over multiple threads, how are any readers supposed the follow it, now or in the future.

author: profdc9
author_rank: Frequent Contributor
timestamp: May 18, 2020, 02:33:19 am
content: I suppose I thought that once it's done it would just be on the githubhttp://www.github.com/profdc9/ActiveRFProbeso all of the information would be there. I am actually going to combine five projects into onehttp://www.github.com/profdc9/RFUtilityKnifeso that the RF Probe, RF Differential Probe, Noise Source, a Gilbert cell mixer, and a LNA can be built together.After you posted this I tried to locate the original message to add it to there also, but I couldn't find it. But I hope that the github will be around for awhile so that one can download or clone it as needed.

author: tggzzz
author_rank: Super Contributor
timestamp: May 18, 2020, 07:10:05 am
content: Quote from: profdc9 on May 18, 2020, 02:33:19 amYou currently have 139 posts, so it shouldn't be difficultfor youto locate here:https://www.eevblog.com/forum/profile/?area=showposts;u=429404If the information cannot be found, it doesn't exist.Why should anybody bother to look at a random github; they need a reason.

author: Mechatrommer
author_rank: Super Contributor
timestamp: May 18, 2020, 10:56:40 am
content: it'll be much easier here.. only 22 topics..https://www.eevblog.com/forum/profile/?area=showposts;sa=topics;u=429404

author: profdc9
author_rank: Frequent Contributor
timestamp: May 18, 2020, 04:30:03 pm
content: I usually use google to find existing projects, and then the github shows up. I added the results to the original thread.