hybridfree/eevblog-posts huggingface dataset:
Dakota Alert MT538-HT (MURS) Rx issue - Page 1
Forum section: electronics / rf-microwave

author: highpower
author_rank: Regular Contributor
timestamp: December 26, 2021, 05:24:18 am
content: I have a couple of these MT538-HT hand held radios and one of them has developed a problem in the receive end. Very broken reception but transmitting seems to be fine. I've searched the net looking for any common problems with these radios but not finding any information at all on them. I did uncover some schematics but that's all I could find. I tried swapping the antennas (stiff rubber ducky with an odd proprietary threaded stud for a connector) with no change in the reception of the unit in question. I was hoping to find someone who might have had a similar issue to point me in the right direction.
Verify my Colpitts Calculator.... - Page 1
Forum section: electronics / rf-microwave

author: antenna
author_rank: Frequent Contributor
timestamp: January 02, 2022, 09:16:37 pm
content: I was hoping someone here could take a look at the calculator I made for building Colpitts oscillators and check it for errors and give me opinions/suggestions regarding improvements because this is fairly new territory for me.Thanks!

author: antenna
author_rank: Frequent Contributor
timestamp: January 02, 2022, 10:24:13 pm
content: I wasn't sure about the 160Ω reactance part, but the way I understand that (which could be wrong) is that with more inductive reactance, more/thinner wire is needed raising the resistance of the coil which affects inductor Q. I picked 160Ω for XL because I have seen a few oscillator examples that used roughly that value.
Rohde and Schwartz Polarad 308 Manual - Page 1
Forum section: electronics / rf-microwave

author: Kraythorne
author_rank: Contributor
timestamp: December 24, 2021, 11:42:34 pm
content: HiI've just purchased a working Rohde and Schwartz Polarad 308 Signal generator but there doesn;t appear to be a user or service manula for this anywhere on the internet (or possibly the entire planet)Does anyone know where this rocking horse s**t can be found?I don't mind paying for it, within reasonThanks
side transition of differential microstrip - Page 1
Forum section: electronics / rf-microwave

author: f4eru
author_rank: Super Contributor
timestamp: December 20, 2021, 01:41:12 pm
content: Hello,I'm looking for how to do a transition for a differential microstrip without ground plane* from one side of the PCB to the other side, without any vias.Any geometry suggestion ?Are there any impedance calculators, given a cross section ?* just found out it's called a "coplanar stripline"

author: ejeffrey
author_rank: Super Contributor
timestamp: December 20, 2021, 03:37:21 pm
content: No vias? Is it a narrowband signal? You can make a directional coupler to do this. What efficiency do you need? How thick is the substrate? How big can the structure be?

author: f4eru
author_rank: Super Contributor
timestamp: December 20, 2021, 03:41:47 pm
content: no vias, because there is high voltage between both sides0.8mm thick FR4the structure can be 60mm long, even more if folded2,4GHztransition should be as low loss as possible...A coupler is a good idea, but wouldn't it have at least 3dB loss ?

author: ejeffrey
author_rank: Super Contributor
timestamp: December 20, 2021, 05:57:09 pm
content: A directional coupler can have ideally unity coupling but directional couplers made with non uniform dielectric (fr4 + air) usually can't be perfect because the odd and even modes don't have the same effective dielectric constant.
Simple NTC biasing for MRF101AN LVDMOS P.A. - Page 1
Forum section: electronics / rf-microwave

author: vu2tve
author_rank: Contributor
timestamp: December 20, 2021, 08:36:09 am
content: Hi,I would like some feedback on a simple NTC based biasing scheme for a MRF101AN reference design for 88-108MHzThis is the reference circuit without the biasing circuithttps://www.eevblog.com/forum/rf-microwave/simple-ntc-biasing-for-mrf101an-lvdmos-p-a/?action=dlattach;attach=1354472Here are reference links for simple biasing schemes with an NTC1.https://www.scitechnol.com/peer-review/biasing-ldmos-amplifiers-employing-a-simple-passive-temperature-to-voltage-converter-agPj.php?article_id=63042.http://www.n4ga.com/biasing-schemes-revisited/(Does not include a schematic)My question is that for a first stab at a bias circuit, should I look at these schemes. I intend to run the amplifier in either class-A (preferably) or class-AB.Thoughts. feedback would be appreciated.Currently I bias the circuit using my lab bench power supply for testing, but I do know some kind of stable temp-compensated bias would be required for proper testing.

author: vu2tve
author_rank: Contributor
timestamp: December 20, 2021, 10:56:52 am
content: I just noticed that the MRF101AN documentation itself gives a simple bias circuit and I somehow missed looking at itPage 2 of thishttps://www.nxp.com/docs/en/quick-reference-guide/MRF101ANEKITQRC.pdfPerhaps this is a good stating point!
Microchip RN2483 LoRa module - what to do with unused antenna port? - Page 1
Forum section: electronics / rf-microwave

author: TomS_
author_rank: Frequent Contributor
timestamp: December 27, 2021, 12:44:23 pm
content: Hi all.I am designing a little personal project using an RN2483. Im based in Europe so I dont need (cant use) the 433MHz antenna.What should I do with that antenna port if I am not going to use it? Im no RF expert, but I believe it should be terminated if not used or connected to an antenna. Should I "simply route it through a 50ohm resistor to ground"?Thanks!

author: jc101
author_rank: Frequent Contributor
timestamp: December 27, 2021, 04:59:24 pm
content: One of the Microchip demo boards, which is 833 only, just has a controlled impedance 50 trace to a large via from the look of it, it isn't terminated.You can always use the Wireless design check service from Microchip, which is free. Bottom of the pagehttps://www.microchip.com/en-us/support/design-help/design-check-services

author: TomS_
author_rank: Frequent Contributor
timestamp: December 28, 2021, 10:59:06 am
content: Quote from: jc101 on December 27, 2021, 04:59:24 pmInteresting.I wonder if the unused radio is simply disabled then (perhaps based on the configured frequency). The datasheet is not clear about what happens.The big via might just be so you can solder on an antenna. A previous topic I started around this module seemed to come to the conclusion that it would probably even work without an attached antenna, even if not strictly technically correct. My plan therefore is to use a piece of wire "about the right length" soldered to a pad immediately at the output from the radio module and hope for the best.
Need help in identifying: Ferretec (Teledyne) YIG Filter (?) FD2506... - Page 1
Forum section: electronics / rf-microwave

author: Uky
author_rank: Regular Contributor
timestamp: December 18, 2021, 03:05:15 pm
content: Greetings Forum,I have two (what I think they are): YIG-filters, marked Ferretec/Litton Model# FD2506.Knowing that Teledyne acquired Ferretec many years ago, I downloaded a catalogfound on the Internet and yes - there were products that looked very much like the filtersI have. They were taken from a scrapped NoiseCom Fading analyzer (Blown PSU, Malfunktioning hard drive,no manual, no support - you can guess...) The part number FD2506 does not appear anywherein the Teledyne catalog so they are obviously custom made or custom marked products.I assume that they are filters because of two SMA-connectors on the opposite side of thehousing. (could also of course be band reject...)The YIG's have four connecting pins marked (left to right): E1 E3 E4 E2. These connectionscan also be seen in the Teledyne catalog. But - the internal connections seems to differ.Between E1 and E2 (outer) I measure 25 Ohms.Between E3 and E4 (inner) I measure 41 Ohms.One of the connections is the heater and the other is the tuning coil.But which is which? The only figures present in the Teledyne catalog are ... 4.5 to 10 Ohms for typical tuning coil resistance.No data for heater resistances are provided.

author: Joel_Dunsmore
author_rank: Regular Contributor
timestamp: December 18, 2021, 03:17:45 pm
content: if you have any way to test the inductance, you could see which one is a very large coil. Maybe in the 100's of milli-henry range. Then hook it up to a DC supply (you might do it through a similar sized resistor) and bias it a little bit and sweep out the response to see what you see. Change the bias and see if it moves center freq. heater coil shouldn't be needed to to get a filter response. Probably in 2-18 GHz range I'd guess.

author: mawyatt
author_rank: Super Contributor
timestamp: December 18, 2021, 03:38:28 pm
content: YIGs filters we've had experience with long ago, do not require any electrical bias and will exhibit a band-pass or band-reject response without such. Just connect the SMAs to a network analyzer and look for a band pass or reject response. Then apply a small DC bias of a few milliamps to the "E" terminals, one of these terminal pair should cause a small change in the YIG response, this is the tuning port, the other is likely the heater. Once you know which is which, you can play around to see what the range of the tuning port is by running the current up/down and maybe change polarity and watch the filter response track.The tuning port adds or subtracts from the fixed magnetic bias by means of the magnetic field created by the coil current.Best,
Intermodulation - Page 1
Forum section: electronics / rf-microwave

author: wa2pux
author_rank: Contributor
timestamp: December 16, 2021, 08:50:13 pm
content: We have a local repeater which is experiencing the effects of intermodulation involving a local 600 KHz AM broadcast station.The repeater is located on a secure tower (cell tower) so our investigation into the exact cause of the problem is prohibited.As a result, the repeater cannot transmit a PL tone or it comes back into the input side of the repeater and holds the squelch open.This whole business caused me to carefully investigate the topic of intermodulation. I was surprised to discover that cell tower installers, wireless microphone manufacturers and, well, basically anyone who is doing anything with RF has to address this issue.After a lot of study, I put together a video which discusses and explains the phenomenon not only in receivers but Passive Inter-Modulation (PIM, as it is called) which is what we are experiencing with our repeater.Ihateto keep my discoveries to myself, so I have provided this video for folks to watch hoping it will help them understand the whole mess (and a mess it is!) It can be found here:https://youtu.be/JhQy2gP9lCM

author: antenna
author_rank: Frequent Contributor
timestamp: December 16, 2021, 09:07:53 pm
content: Quote from: wa2pux on December 16, 2021, 08:50:13 pmIs it possible you provided the wrong youtube link? That link is about PPM, not PIM.

author: antenna
author_rank: Frequent Contributor
timestamp: December 16, 2021, 09:31:41 pm
content: Although finding the PIM source should be a priority, couldn't you simply change the repeater offset?

author: David Hess
author_rank: Super Contributor
timestamp: December 17, 2021, 04:01:48 am
content: Wow, that would be a tough problem unless you can switch to a non-standard repeater offset. The usual solution is to switch frequencies but that obviously will not work on 2 meters if the interfering signal is 600 kHz; every pair is going to have the same problem.That sure sounds like a PIM (passive inter-modulation) problem on the tower itself rather than 600 kHz getting through the diplexer.

author: chrisl
author_rank: Regular Contributor
timestamp: December 17, 2021, 06:33:45 am
content: I believe this is the correct link:
Biasing a LVDMOS MOSFET-MRF101AN for class A - Page 1
Forum section: electronics / rf-microwave

author: vu2tve
author_rank: Contributor
timestamp: January 22, 2022, 07:32:12 am
content: I'm trying to figure out from its data sheet what should be the ideal Idq for MRF101AN for class-A operation, and I can't seem to be able to understand the correct valueData Sheet Link:https://www.nxp.com/docs/en/data-sheet/MRF101AN.pdfQuick Reference Circuit:https://www.nxp.com/docs/en/quick-reference-guide/MRF101ANEKITQRC.pdfThe QRC guide says to set the Idq between 50-500mA, but I'm guessing they're referring to class-AB.I can't find a load line curve, so wondering how to go about figuring out the right Idq.Any suggestions?Thanks! // Anish

author: T3sl4co1l
author_rank: Super Contributor
timestamp: January 22, 2022, 10:38:39 am
content: Load line is basically straight for any transistor; take your pick. Load lines were only important to tubes I think, because the ratings are so constrained, you only get useful output power right at device ratings (Ik and Pd, sometimes Va as well).You might wish to avoid low Vds because of the high capacitance there, and you need to know what peak Id the device can draw, or that the circuit can handle (given constraints such as bandwidth, matching network if any, etc.).Example: Vdd = 100V (free variable)Vds(min) = 20V (less may be acceptable, just spitballing here)Id = 500mA ==> Pd = 50WId(cutoff) ~= 0mA, Id(pk) ~= 1A (this won't happen perfectly due to distortion in the transistor; source degeneration, shunt feedback, or predistorting the gate drive, may be acceptable methods to compensate)RL = (100V - 20V) / (1A - 500mA) = 80V/500mA = 160ΩSay load is 50 ohms, needs 160/50 matching, or 1.789:1 turns ratio transformer for wideband, or equivalent L-match or other network if narrowband.Note that if Coss ~ 50pF, then 1 / (2 pi (160Ω) (50pF) = 20MHz bandwidth, whether baseband (0-20MHz) or tuned (e.g. 90-110MHz at a 100MHz center frequency).Or wait, is that center to band edge? I think it's always total width but I don't actually remember the derivation at this instant... Anyway, proportional to this, whatever the constant factor is. That factor can also be increased by increasing the tuning order (in the same way a baseband circuit can be "peaked"), but only by a modest amount (~2x even for 3rd or 4th order), and the additional reactance of such a load tends to decrease the maximum stable gain so may not be worthwhile in terms of GBW. But gain probably isn't a top priority for a PA so that's probably academic, no worry.Tim
New Adalm-Pluto Dual TX/RX - Page 1
Forum section: electronics / rf-microwave

author: ovenqin
author_rank: Contributor
timestamp: December 11, 2021, 07:31:15 am
content: Hi guysRecently, I bought a new adalm-pluto SDR box, when I ran the ADI-IIO for test, my tx power was still low at -56dbm which measured by my spectrum analyzer. PCB version of Pluto is Rev.C, Serial number:1044730aXXXXX. Then， I open the Pluto to check, I surprise there are extra Ipex interface soldered and marked TX/RX character. As we know the ADC9363 chip have dual tx/rx channels, but it don't open in the old pluto pcb , I don't sure the new pluto which open for dual tx/rx. I search the picture in google, but I don't see anyone have the same pcb picture with mine.1. My new Adalm-Pluto is fake one???2. New Adalm-Pluto is incompatilbe with ADI-IIO software ,so my TX signal still weak at -56dBm, maybe the parameter is error in ADI-IIO?3. anyone try to test dual tx/rx in this new adalm-pluto?Thank youXu

author: Qw3rtzuiop
author_rank: Frequent Contributor
timestamp: December 11, 2021, 10:19:04 am
content: Thats revision D of the SDR.Take a look here:https://wiki.analog.com/university/tools/pluto/hacking/hardwarehttps://forum.amsat-dl.org/index.php?thread/3686-adalm-pluto-rev-d/

author: ovenqin
author_rank: Contributor
timestamp: December 11, 2021, 11:06:16 am
content: Thank your rely! I think ADI-IIO have bugs for Rev.C/D of Pluto.By use SATSAGEN0.6 software, the TX output is OK now.Although the dual TX/RX interface in PCB board, but I don't find the software to support it. Maybe We must wait.
Another question for Microwave VFO.  - Page 1
Forum section: electronics / rf-microwave

author: Cacao
author_rank: Contributor
timestamp: June 26, 2017, 04:07:51 am
content: How can I increase the Vpk-pk of the output? I've tried to vary the voltage and the resistors but it still not enough to make it reach 5V and up. Hope you can help me again. ThanksHere is the simulation:https://ibb.co/caCShk

author: jwet
author_rank: Frequent Contributor
timestamp: December 11, 2021, 05:05:35 am
content: Your bypassed collector load looks suspect to get good swings. The Icc is about 7 mA, this is dropping a lot of voltage across the 1.5k bypass resistor. Consider making this a 220 ohm and up the value of the C from 5 pF to 50 pF.
Yaesu FTDX-10 1st mixer - Page 1
Forum section: electronics / rf-microwave

author: UR5FFR
author_rank: Contributor
timestamp: November 29, 2021, 02:34:20 pm
content: Hello,Analyzing the Yaesu FTDX-10 circuit, I discovered that the first mixer has an original design. Typically, mixers use transformers to separate the signal into antiphase components. But this mixer uses a splitter. In the appendix, I have added the original mixer circuit and its simplified version, more suitable for analysis.I have not come across a similar mixer design. What advantages does it offer compared to using a conventional transformer at the input?PS It is interesting that the Yaesu FTDX-101 transceiver uses a mixer with the same structure and splitter at the input, but it is active and instead of digital switch FTS3257, dual-gate field-effect transistors are used.

author: M0HZH
author_rank: Regular Contributor
timestamp: December 14, 2021, 01:50:46 pm
content: I'm curious about this as well. FTDX-10 and 101 have exceptional dynamic range and to achieve that the 1st mixer is critical; probably this layout allows for better performance?PA3AKE's research shows the transformer makes a big difference in mixer performance:https://martein.home.xs4all.nl/pa3ake/hmode/hmode_intro.html

author: UR5FFR
author_rank: Contributor
timestamp: December 14, 2021, 09:24:05 pm
content: Other non standard in FTDX-10/101 schematic is amplifier between BPF and 1st mixer. Usually this amplifier manually turn on/off. But not here. In FTDX this amplifier can't be turn off - it always working. In FTDX-10 it schematic is very simple - Norton amplifier with BFQ19 at 30mA collector current

author: mag_therm
author_rank: Frequent Contributor
timestamp: December 14, 2021, 10:32:25 pm
content: About your equivalent circuit:I think the ratios and mutual inductances would be needed for the T3004 to see what is going on there.It looks like the old FM "Quadrature detector", the outputs are the voltage on input tuned circuit, +/- the centre tapped windings which are in quadrature.Vector diagrams needed.A question if I may..I am testing an ft8 demodulator here. ( First RF "design" project!)Using MC1496 Gilbert cell with Epson SG8018 carrier oscillators on 458kHz / 452 kHz IF it seems to be working well.I had some trouble with resonant input coupling transformer but now trying an untuned toroid single ended to diff with windings diametrically spaced 12mm.( Low mutual C)Ratio 1:1 and scaling so that -10dBm IF is about -20dBfs audio.Next project is to see if I can use the similar topology on converters for 30 and 20 meter with dedicated XO's just for Ft8 per band.Maybe mast head converters with double conversion to Low IF to computerThe proposed XO are Epson SG8018 .The jitter is quoted in various peak to peak and rms values.For exampleAt 3.3V supply, 10 MHzOffset Frequency 12 kHz to 20 MHz : peak to peak jitter = 66.9 psCan be converted to dB, but I would not be wiser.What is a figure of merit for mixer oscillator's jitter receiving ft8?-thanks
Can I get a just a PCBA FCC/IC certified? - Page 1
Forum section: electronics / rf-microwave

author: grumpy_engineer
author_rank: Newbie
timestamp: December 09, 2021, 03:49:52 am
content: As the title says, I am working on a PCBA that will live inside a larger plastic box, hence, I want to save some costs and not include a plastic box for it.How will this impact FCC testing? Does a product need an enclosure to get FCC certified? I can't find any information on this online.Thanks,
SWL DX on FT8 20 metre -results - Page 1
Forum section: electronics / rf-microwave

author: mag_therm
author_rank: Frequent Contributor
timestamp: December 17, 2021, 05:37:55 pm
content: The attached charts are a summary of reception over 24 hours, 2021 Dec 16 ~ 17.This is after my latest round of hardware mods to the receiver.The antenna is just a tuned longwire.The charts are created in Python, under linux crond, to parse received data from each 6 hourly period.The local USA stations are mostly blocked for clarity of the DX ones.The scripts log on to the Canadian source of Solar Flux Units (SFU)The DX stations go through some geodesic functions,then are plotted using Gnuplot on a great circle centred on the location here in Michigan.Over the past year the SFU has risen from 79 to 110 units.Also recently the antenna noise here is much less on 20 m, over these plots it was fluctuating -95 ~ -105 dBm day and nightSo along with receiver updates I am getting better results compared to last winter.https://app.box.com/s/01798xggergpa3fwz69nnh11gkaq71eghttps://app.box.com/s/1bdh94mh50u8byy2tl8l53umnztq6wimhttps://app.box.com/s/yyvd0iicz3yws0221a9nm7qtktokynh3https://app.box.com/s/ol7dkgxh8s3c8nocrogcnokhte0mfppm

author: radiolistener
author_rank: Super Contributor
timestamp: December 18, 2021, 02:40:34 am
content: I remember on this summer (7 June 2021 at night) I got several FT8 SWL DX on 20m band with the distance more than 12000 kmThe antenna was just a long wire (untuned) near building. And it was in the city with high environment noise.The receiver was hand made DDC SDR with 14 bit high speed ADC.

author: A.Z.
author_rank: Super Contributor
timestamp: December 18, 2021, 02:52:34 pm
content: just curious, why didn't you use pskreporter ? It's easy to capture the maps and post them as images, then one, willing to do so, may add the reception log

author: mag_therm
author_rank: Frequent Contributor
timestamp: December 18, 2021, 07:17:11 pm
content: A.Z. :Yes pskreporter is an excellent job.The python to do the great circle was simple job about 150 lines or so.radio listener :The most distant ft8 received here was from Indonesia and New Zealand, both about 18000 km from Michigan.A reference distant station is Radio New Zealand which broadcasts continuously on various frequencies.100 kW with arrays pointing north westerly I think.https://www.rnz.co.nz/international/listen

author: A.Z.
author_rank: Super Contributor
timestamp: December 19, 2021, 07:45:23 am
content: Quote from: mag_therm on December 18, 2021, 07:17:11 pmI see, now, if you want to add a map to your plot, you may generate it herehttps://ns6t.net/azimuth/and add it as a background/base image for your generated plots
Airspy Server config - Page 1
Forum section: electronics / rf-microwave

author: veedub565
author_rank: Frequent Contributor
timestamp: November 20, 2021, 06:31:10 pm
content: I set up my Raspberry Pi3 with Airspy server, and it worked ok I was able to connect to it remotely using SDR#. I didn't really want it publicly listed so I set this to 0 in the config file. I knew the ip address and was still able to connect remotely. For some reason that's now stopped working. If I set it to be publicly listed on the airspy map it works no probs, set to not publicly listed then won't connect.Thiswasworking, so I don't know why it isn't now. Any idea's ?The other thing, when itwasworking I had a high noise floor some 20dB higher compared to running the server on a laptop. I tried powering the Pi from the same laptop (running on battery) to eliminate any wall wart noise and it made no difference, so it's not that. I tried running the server on the laptop, then powered the Pi on and held it close to the RTL-SDR dongle, and it made no difference. SO it's not the wall wart, it not the Pi spewing out RFi, the only thing I can think is that it's internally generated noise on the USB lines. And the laptop is much cleaner than the Pi in this regard.

author: A.Z.
author_rank: Super Contributor
timestamp: November 21, 2021, 08:58:28 am
content: Is the SDR directly connected to the Pi USB port ? If so, try connecting the SDR using an USB cable with chokes, also, enclose the Pi in a metal box and ensure that the box is properly grounded

author: veedub565
author_rank: Frequent Contributor
timestamp: November 21, 2021, 07:53:38 pm
content: It's directly connected, I'll try with a cable and chokes and see what that does. I don't think putting it in a box will do anything. COnnecting the dongle to a laptop, and holding the Pi next to the dongle doesn't create any noise problems. So it's not radiating that way.

author: A.Z.
author_rank: Super Contributor
timestamp: November 21, 2021, 09:18:53 pm
content: Quote from: veedub565 on November 21, 2021, 07:53:38 pmI was thinking to conducted noise, and that's why I suggested a cable with chokes, the metal box could also help shorting the noise to ground

author: fordem
author_rank: Regular Contributor
timestamp: November 30, 2021, 02:34:41 am
content: Quote from: veedub565 on November 20, 2021, 06:31:10 pmWere you connecting from outside the "local LAN"? If so, you might want to verify the ip address(es), your public ip address may have changed without your realizing it, and the private ip that the pi was on may also have changed if you did not set a static address.

author: veedub565
author_rank: Frequent Contributor
timestamp: December 02, 2021, 08:38:24 am
content: Yes I was connecting from outside the local LAN. I checked the IP on the Raspberry and used that IP to try and connect.
Up/down convert WiFi to 6 GHz - Page 1
Forum section: electronics / rf-microwave

author: rfspezi
author_rank: Regular Contributor
timestamp: November 17, 2021, 09:07:32 am
content: I want to use a mixer to up/down convert a 2.4 GHz Wifi signal to e.g. 6.4 GHz.For that i plan to use an IF-frequency below the RF frequency at 4.0 GHz.Would that be ok or should i place the IF frequency above the RF frequency at 8.0 GHz? (spectral inversion is no problem)Do i miss something concerning the spurious?Another question that comes to mind is what types of non-reflective filters i could use which are easily available and wether i need it on the RF port only?Mabye someone knows a circuit or has implemented such a converter and can give me some hints?Thanks!

author: NiHaoMike
author_rank: Super Contributor
timestamp: November 17, 2021, 12:50:29 pm
content: Not sure on the inner workings but one time I stayed in a hotel where the Wifi was provided using little boxes that plugged into the cable TV network. The boxes just had coax input, a pass through for the TV, and power. Most likely they work by translating the 2.4GHz band to some lower frequency that can go further on the coax.

author: max-bit
author_rank: Frequent Contributor
timestamp: December 01, 2021, 06:32:22 am
content: Do you have the appropriate radio license to broadcast in another band?
new scope capabilitys - Page 1
Forum section: electronics / rf-microwave

author: m3vuv
author_rank: Super Contributor
timestamp: November 23, 2021, 06:04:08 am
content: Hi all,ive just brought one of these cheap ,Hewlett Packard HP54503A 500MHz 4 Channel Digitizing Oscilloscope, just wondered if it will be capable of doing measurements on a 70cm tx/rx?. tia

author: bob91343
author_rank: Super Contributor
timestamp: November 23, 2021, 06:27:37 am
content: What are you trying to measure?

author: m3vuv
author_rank: Super Contributor
timestamp: November 23, 2021, 06:55:05 am
content: nothing at 70 cms,ive a deaf radio on 2mtrs ,i want to look at the rx signals and trace them,my other scope is 50 meggs bandwith so wondered if the new one is capable of doing this at 145 meggs.

author: BrokenYugo
author_rank: Super Contributor
timestamp: November 23, 2021, 05:15:50 pm
content: Google says it's not a true 500MHz, in that it will only handle that as a repetitive signal. So I guess it would work fine for usual inject a signal and see where it stops sort of troubleshooting.

author: bob91343
author_rank: Super Contributor
timestamp: November 23, 2021, 08:20:25 pm
content: I don't know that model. I have a 54542A that works fine well past its claimed limit of 500 MHz. In fact I measured around 650 MHz bandwidth, very high for what I do.Having said that, it's seldom necessary to have a wide bandwidth scope to troubleshoot a receiver. You put a signal in and first see if you have a corresponding IF signal. If not, the problem is near the front end. If so, it's later in the chain. Those radios are almost always at least double conversion so there is a second mixer to investigate.

author: max-bit
author_rank: Frequent Contributor
timestamp: November 30, 2021, 10:59:34 am
content: As the oscilloscope has a 500 MHz band, it measures up to about 500 MHz (usually with a decrease of -3dB) but this is not a rule.

author: MF-jockey
author_rank: Regular Contributor
timestamp: November 30, 2021, 10:13:23 pm
content: The probe plays an important role.There are also nice videos from Daveactive probes

author: radiolistener
author_rank: Super Contributor
timestamp: December 01, 2021, 03:02:09 am
content: At 400-500 MHz it's better to not use probes, but use RF connectors with coax cable. Because probes are working good bellow 100-200 MHz max.
Tuning 70cm duplexers, what -dBm - Page 1
Forum section: electronics / rf-microwave

author: hostile
author_rank: Contributor
timestamp: May 01, 2021, 03:03:58 pm
content: What is a decent dBm attenuation to shoot for on the filtered and passed signal ?Right now I am at -90dBm and -0.8dBmrepeater would be on same antenna and operate 100-200' with 100W. Not sure receiver sensitivity yet.

author: thinkfat
author_rank: Unknown
timestamp: May 01, 2021, 03:31:05 pm
content: That depends on the output power and the noise floor of the receiver, how well it suppresses close-by signals and the maximum no-damage input power. But typically, you'd want more than 100dB between the TX and RX path.

author: N0NB
author_rank: Contributor
timestamp: November 20, 2021, 01:59:49 pm
content: Here I have a TX RX Systems 28-70-02 that is spec'ed at 100 dB isolation per channel and 0.6 dB if insertion loss. I measured 0.6 dB on one side and 0.7 dB on the other and approximately 90 dB notch depth. The receiver has a measured SINAD of -118 dBm and the transmitter is set for 25 Watts with the antenna at about 190 feet, Height Above Average Terrain of 156 feet. The repeater is a Kenwood TKR-850 V1.Range is about 30 miles and after a year I have not noticed any desense and is rather well balanced.
Transceiver Power Protection - Page 1
Forum section: electronics / rf-microwave

author: cemelec
author_rank: Contributor
timestamp: November 14, 2021, 05:05:06 pm
content: I had been wondering why the DC power lead to my Icom IC-7300 had fuses in both positive and negative lines; after some digging around it seems that this is intended for mobile operation where a ground fault in the vehicle could in theory try to pass current through the transceiver ground.I have no intention of mobile use for now, only fixed indoor operation, so can I safely fuse only the positive supply? The reason I ask is that I'm halfway through building a transient suppressor / crowbar over voltage protection unit housed in a small metal box (guitar pedal style) and would prefer the single fuse option. My PSU is a 30A linear, so in the (admittedly unlikely) event of pass transistor failure the voltage could rise to maybe 25V.I've never seen fuses in the ground line on any professional test equipment, and usually ground lines are kept as low impedance as possible, even a fuse volt drop is often detrimental to good operation.Thanks

author: bob91343
author_rank: Super Contributor
timestamp: November 14, 2021, 07:33:02 pm
content: I don't think you need a fuse in the negative lead. Perhaps in the case of replacing a car battery backwards it might save a radio. Or just mistakenly applying reverse voltage to the radio by mistake.

author: David Hess
author_rank: Super Contributor
timestamp: November 15, 2021, 03:01:56 am
content: The risk with a mobile transceiver is the ground loop formed from the negative battery connection to chassis ground, and the the antenna connection to chassis ground, so a fuse is inserted at the negative power lead.

author: TheMG
author_rank: Frequent Contributor
timestamp: November 16, 2021, 11:53:53 pm
content: Many people will wire their transceiver directly to the positive and negative battery terminals. The risk with that is that if the connection between the battery and the vehicle chassis goes bad (which is a surprisingly common occurrence especially in areas that use a lot of road salt), current will flow from the vehicle chassis, through the antenna mount, down the coax shield, and the transceivers negative power wire back to the battery, and since that can be tens or hundreds of amps would be a fire hazard. That is why the manufacturers put a fuse inline with the negative wire.It is not necessary in a base station installation to have this fuse, or even in a vehicle installation as long as the negative wire is connected to its own connection directly to the vehicle chassis instead of the battery terminal.
CMU200 - Page 1
Forum section: electronics / rf-microwave

author: jean françois
author_rank: Contributor
timestamp: November 12, 2021, 12:37:56 pm
content: Hello,How to use the frequency meter of my CMU200?the frequency meter I usually use has broken down.thank youJ.F

author: max-bit
author_rank: Frequent Contributor
timestamp: November 13, 2021, 12:37:39 pm
content: What do you want to know ?What happened ? What are the symptoms of damage?

author: YU7C
author_rank: Regular Contributor
timestamp: November 13, 2021, 02:35:21 pm
content: Hello,try with spectrum analyzer inside CMU200 and markers.73 de Voja/YU7C
s22 of amplifier interacting with s11 of antenna - Page 1
Forum section: electronics / rf-microwave

author: faust1002
author_rank: Contributor
timestamp: November 11, 2021, 10:10:08 pm
content: Hello,Again, I have problems with understanding what my lecturer wantsand I hope that you can help me.The problem is as follows - I have an amplifier, which has output impedance of 63+j80Ω. So, when 50Ω load is connected, then return loss is equal to roughly 4.65dB. So far, so good. But the question is what will happen when 50Ω antenna, which has RL od 30dB, will be connected to this amplifier.My understanding is that RL of the amplifier (4.65dB) represents its s22and RL of the antenna (50dB) corresponds to antenna's s11. Now, because s22is much higher than s11it dominates. As a result, roughly 40% of the power outputted by the amplifier will be reflected.The provided answer says about above 30% of the incident power being reflected. This is more or less aligned with my interpretation. But I want to double-check if my understanding is correct.Kind regards

author: thundertronics.com
author_rank: Contributor
timestamp: November 12, 2021, 04:27:38 am
content: Probably lecturer wants to exercise using these formulas. If Zs=50, Zl=53 or 47, then antenna "RL" would be around 30dB, and reflected % would be between 32.7 and 35.97..See attached image, you can put other numbers using this calculator:Mathnotepad link with formulas.

author: faust1002
author_rank: Contributor
timestamp: November 12, 2021, 08:09:15 am
content: Step by step. Zs and Zl are given and are equal to 63+j80Ω and 50Ω respectively. Besides, RL of 30dB does not correspond to roughly 30% of the incident power being reflected. 4.65dB does.

author: thundertronics.com
author_rank: Contributor
timestamp: November 13, 2021, 03:33:18 am
content: Quote from: faust1002 on November 11, 2021, 10:10:08 pmI think that in this particular question RL of 30dB probably means that antenna is almost 50 Ohm, for example 54 Ohm.Quote from: faust1002 on November 11, 2021, 10:10:08 pmwhen it is connected to 50 ohm load, RL=-20*Log10(Abs((Zl-Zs)/(Zl+Zs)))=4.65dBYour amplifier's Zs=63+i*80, but calculation also includes load's Zl=50.Quote from: faust1002 on November 11, 2021, 10:10:08 pmAntenna's s11 relative to what? I think relative to characteristic impedance Z0=50 Ohm.RL=30db probably means that it's impedance is not 50 Ohm exactly, but Zl=54 Ohm:Zs=50, Zl=54 RL=-20*Log10(Abs((Zl-Zs)/(Zl+Zs)))≈30dBQuote from: faust1002 on November 11, 2021, 10:10:08 pmThis is probably wrong assumption. As soon as we disconnected 50 ohm load, RL of amplifier is no longer may be calculated using Zl=50, we have an amplifier with open connection Zl=large number, and new RL would be almost 0, and reflection would be almost 100%. Amplifier's S22 remains the same: s22 = (Zs-Z0)/(Zs+Z0) ≈ 0.41-0.42*i; backwards from s to z: Zs=Z0*(1+S22)/(1-S22) ≈ 62.5 - i*80.1To sum up,amp + 50 ohm load: Zs=63+i*80 ; Zl=50 ; RL=4.65dB50 ohm 50 ohm antenna: Zs=50; Zl=54; RL=30dB IMO, antenna's RL nothing to do with 63+i*80..
Using IC-705 with RS-BA1 Version 1  - Page 1
Forum section: electronics / rf-microwave

author: msuthar
author_rank: Contributor
timestamp: November 07, 2021, 01:29:35 pm
content: IC-705.zip(4.14 kB - downloaded 190 times.)IC-705.zip(4.14 kB - downloaded 190 times.)IC-705.zip(4.14 kB - downloaded 190 times.)Hi,Attached is IC-705.ini file for theRS-BA1 Version 1software As this version1 does not support IC-705 transceiver.It will add this rig with USB support and if you choose baud rate of 115200 then it will enables theSpectrum Scopewith some what limited functions.copy this IC-705.ini file to following pathC:\Program Files (x86)\Icom\RS-BA1\RemoteController\models\and enjoy.Brgds.73 de vu2ehy
Need. Help for Stanford Research FS275 1oMhz rubibium clock. Test calibration - Page 1
Forum section: electronics / rf-microwave

author: KIKIWILLYBEE
author_rank: Newbie
timestamp: November 01, 2021, 11:54:55 pm
content: Hello,please, I courteously ask for your help with the calibration of aStanford research FS275 benchtop clock.I acquired used on eBay, for audio use, to have a 10 MHz world clock clock, which can distribute its 10 MHz signal, for the synchronization of audio devices: switch 802.3, CD player, USB interface to I2s lvds.....The latter does not lock, and it is not at 10.oooooo MHz.Full newbie,I have no idea of the process to. bring this clock to its nominative frequency. and locking.I have a fluke 68xxx + ocxo in frequency Metre, a Hantek 400 MHz DSO, and a pc connected in RS232 connected in usb. to this clock.And it's not how to proceed, I also have to equip in addition to a gps clock.,I have another time reference at 10 MHz, low phase noise at -121dB, at 1 hz.Thank you very much...Willy ;-).

author: max-bit
author_rank: Frequent Contributor
timestamp: November 02, 2021, 06:58:31 am
content: Do I understand correctly that the FS725 does not go into a LOCKED state ?(this model is 725 or 275?)

author: KIKIWILLYBEE
author_rank: Newbie
timestamp: November 02, 2021, 08:18:24 am
content: Hi sir ,Yess , no locked state (only one time ..?), and of course not really at 10.ooooooo. MHzThanx sir,Yours,W ;-)

author: max-bit
author_rank: Frequent Contributor
timestamp: November 02, 2021, 10:44:47 am
content: One more question is the 725 or 275 model because I can't find the 275 version. And ... more the specification etc.Unfortunately, the causes of "no lock" can be very many, from prosaic to very difficult to repair (e.g. damage to the Rubidium source)As I do not know what model it is, you have any documentation (diagram, service manual) ?

author: 5065AGuru
author_rank: Frequent Contributor
timestamp: November 03, 2021, 03:23:54 am
content: Manual is available athttps://www.thinksrs.com/downloads/man.htmlcheers,Corby
what is this coax - Page 1
Forum section: electronics / rf-microwave

author: m3vuv
author_rank: Super Contributor
timestamp: November 01, 2021, 09:47:50 am
content: hi all,i have some coax it looks the same as rg-213 but has a solid copper wire core not stranded,any ideas ?

author: HB9EVI
author_rank: Frequent Contributor
timestamp: November 01, 2021, 10:44:20 am
content: hmm, but RG213 is a 10,4mm coaxhow does the dielectic material look like; solid PE, foam or othersthe only coax with this diameter and solid conductor I know is Aircom Plus

author: RoGeorge
author_rank: Super Contributor
timestamp: November 01, 2021, 11:18:43 am
content: Quote from: HB9EVI on November 01, 2021, 10:44:20 amOoops, sorry, I've deleted my wrong answer, thank you for letting me know.

author: MartinL
author_rank: Regular Contributor
timestamp: November 01, 2021, 11:38:49 am
content: Is the core actually solid copper, or copper-covered aluminium? What's the core diameter?Could be LMR400 or one of the clones of it e.g. HDF400.

author: vk6zgo
author_rank: Super Contributor
timestamp: November 01, 2021, 12:42:48 pm
content: Quote from: m3vuv on November 01, 2021, 09:47:50 amTry Belden 9913.https://www.talleycom.com/images/pdf/BELRG8U1.pdf

author: Neomys Sapiens
author_rank: Super Contributor
timestamp: November 01, 2021, 08:58:50 pm
content: If it is an older cable, it might be RG-8. M17/223-00001 is for a cable with solid center conductor and double shield like RG-213 (same diameter), which is the successor to RG-223 (M17/84).It is a special chicanery of this standard that the RG-# does not equal the slash sheet number!

author: max-bit
author_rank: Frequent Contributor
timestamp: November 02, 2021, 06:51:42 am
content: List of RG cable:https://en.wikipedia.org/wiki/Coaxial_cableMoreover, some manufacturers did not specify their cables according to the RG standard, but used their own markings. Besides, if the cable has no clear markings on the jacket, it is a bit strange.Can you give a photo?
RFID security - Page 1
Forum section: electronics / rf-microwave

author: antenna
author_rank: Frequent Contributor
timestamp: November 02, 2021, 05:06:04 am
content: I keep seeing videos online talking about aluminum foil and wallets. Why don't card manufacturers add a galvanic skin contact pad (or a blister button) to the cards such that if the person using the card does not have his/her finger on it, the RFID chip transmits incorrect data? Everything works as expected, it just grabs different data from the chip to modulate with. Seems too simple not to implement.

author: ataradov
author_rank: Super Contributor
timestamp: November 02, 2021, 05:23:12 am
content: How is that simple? This would require a lot of tooling for the card itself to incorporate that touch pad.Also, is there evidence that it is a real issue? There is a company that pushes their stupid wallets, but that's just an ad and nothing more.And if you have more than one RFID card, then neither works, which is quite annoying for legitimate uses.And if my understanding of the technology is correct, there is nothing useful you can read from the card. You actually need to perform the transaction right there. You can't collect card info and use it later.This means that you need to use a terminal fully provisioned for banking. And it would be linked to a real bank account opened into someone's name. So the risk is too high to do that in practice.This all assumes credit/debit cards, of course, not hotel keys and security cards. Those things may work differently.
Use HP DSP-1200SB A  a a power source to ham equipment - Page 1
Forum section: electronics / rf-microwave

author: axm1955@yahoo.com
author_rank: Newbie
timestamp: October 17, 2021, 11:09:14 pm
content: Hello all,Acquired a couple HP DSP-1200SB A server power supplies and would like to adapt it (as I did with previous HSTNS-PD18) to supply my ham radio equipment, but have been unable to locate any diagrams on the unit.The actual PN is 656364-B21 and sources on the internet have stated if was Gen 6 of the DSP-1200 series of supplies. As with most other hot plugable units I can easily turn it on, but as with all other server supplies it's set to provide 12V DC to the server circuitry, so wondered if anyone in these forums may have some additional technical information I can use to accomplish my goal.Many thanks in advance for any useful information on this power supply.

author: bob91343
author_rank: Super Contributor
timestamp: October 18, 2021, 01:11:30 am
content: Well, it depends. I assume you want to increase the 12V to 13.8V. That should be simple once you reverse engineer it. There should be a resistive divider somewhere that you can alter.The tradition of supplying schematic diagrams has ended. Seizing on that, now manufacturers have decided to refuse requests for them. Their cost to send one is incidental, and would improve their image. But they are adamant as far as I know.

author: TheMG
author_rank: Frequent Contributor
timestamp: October 22, 2021, 09:28:17 pm
content: Unless you're also float charging a backup battery, there should be no need to modify the output voltage, most gear should perform normally on 12V, since that is the nominal voltage when running from batteries that are not currently being charged (vehicle with the engine off, backup batteries during a power failure, portable operation, etc).

author: MartinL
author_rank: Regular Contributor
timestamp: October 23, 2021, 12:14:20 pm
content: The 12V supply from a switch mode PSU intended for server use might be quite noisy, incidentally. These supplies are designed primarily for high power rather than smooth output.Whether that's an issue will depend on the equipment you want to supply.

author: Melt-O-Tronic
author_rank: Frequent Contributor
timestamp: November 01, 2021, 06:59:30 pm
content: MartinL is very correct. Another problem that makes nearly all computer switching PSU's a poor choice for ham radio is that they are optimized for continuous power into a non-varying load. Even if the DC output is clean enough at high power (transmit), when the power demand is low (receive), the PSU noise tends to dominate the output. There may be exceptions to this, but I've never encountered one.
SAW BP filter proven manufacturer - Page 1
Forum section: electronics / rf-microwave

author: e.sotillet
author_rank: Contributor
timestamp: October 25, 2021, 11:25:57 pm
content: Hi folks! Any has experience with SAW filters for VHF manufacturer?I had a bad experience with one, ask to delivery a custom filter and was lost money: a lot of pass band ripple, poor high band attenuation, etc.Best regards

author: coppercone2
author_rank: Super Contributor
timestamp: October 26, 2021, 12:43:53 am
content: well, how much worse was it then the commercial filter of the closest type. then you know if you got ripped off, are working with people outside of their skill range, or if its just hard.They likely have a test based on a common expected application, likely for telecom, that maybe is not super nice

author: Joel_Dunsmore
author_rank: Regular Contributor
timestamp: November 01, 2021, 03:07:56 pm
content: Well, I know muRata is a very good SAW filter manufacturer with very careful process control and testing to spec. Not sure if their parts are available in low volume.
2SA202D Sanyo Germanium Transistor - Datasheet - Page 1
Forum section: electronics / rf-microwave

author: 2X
author_rank: Frequent Contributor
timestamp: October 26, 2021, 08:37:18 pm
content: Hi,does anyone has the old original datasheet of the 2SA202D Sanyo Germanium Transistor? I found only one old datasheet (at the below link) that didn't say SANYO.https://datasheetspdf.com/pdf-file/622907/ETC/2SA202/1

author: vu2nan
author_rank: Contributor
timestamp: October 29, 2021, 12:11:12 pm
content: Here's one.https://www.datasheets360.com/pdf/8751851082732291229Nandu.