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  1. 2m frequency allocation for channels

    I'm studying for my ham test and have a question that isn't clearly answered in my study guide.

    On 2m, it seems channels are spaced 15Khz or 20 Khz or 30KHz apart, and (I think) channels have a bandwidth of 16KHz. Wouldn't that means the channels overlap on 15KHz channel spacing?

    Next, I read somewhere that there is 6KHz guard band between channels. But mathematically that doesn't fit either 15KHz or 20KHz spacing.

    Can someone clarify this for me? Are there supposed to be 6KHz guard bands between channels? And the above assume 16KHz channel bandwidth (but I read somewhere online about narrow and wide band channels, so I don't know if that is a factor)

    I'm in Canada in case that affects the answer.

  2. Why do biconical antennas have a wide bandwidth?

    Why does a horizontal biconical antenna have a wider bandwidth than a dipole of similar length? What's the physics behind the biconical geometry having a bandwidth uncoupled from its length in wavelengths, as for a (near) resonant half-wave dipole.

  3. Best HF Ham Radio Transceiver for Startup

    I was wondering what would be the best startup HF transceiver. It would be used in the 3-30 MHz band, have frequency flexibility, have decent quality audio with use in skywave propagation, and be for the best price, under $200 Canadian. This could include any of the following: analog, SDR, QRP, transceiver kits, etc. This would not include cheap Chinese models unless they meet the requirements. Does this exist? Thank you.

  4. FSK Synchronisation

    I am trying to write my own AFSK decoder with QT/C++.

    I can read/and identify the SPACE and MARK in the audio stream.... And whilst I can see how to encode (depending on which variant of encoding that you use) - I am unable to figure out how to synchronize the data stream.

    For example:

    If I were to send HI

    This would be encoded as (ITA2 LSB)

    10100 00110

    So on decoding... is there a preamble i.e. ? Note: This is my made-up preamble.

    01010 10100 00110
    <PRE> <H>   <I> 

    Any pointers/links would be appreciated if not a direct answer.


    Tim. DU3TW.

  5. NooElec for Startup HF Communication

    I am working on setting up a Ham Radio shack for long distance communication on the HF frequency. The goal is to transmit 1,200km from Alberta to Manitoba using skywave propagation. I would need to be able to transmit and receive 10mhz at 30 degrees on a low budget. I am considering using the Nooelec NESDR Smart HF Bundle. What are your thoughts on this for transmitting, and do you have any recommendations on what would be good antennas to use? Thank you.

  6. What DSP functionality is used for Direwolf?

    Direwolf is a sound card TNC for FX.25/AX.25 communications. Direwolf "Uses computer's "soundcard" and digital signal processing."

    I checked the code on github and found the dsp.h header file. It contains four functions including a window function, and two band pass filter functions. Surely these four functions are not enough to do the type of DSP Direwolf does.

    So my question is what are ALL the functions and functionality used that constitutes Direwolf's entire DSP functionality. Citing Direwolf source files and or an accompanying high level explaination would be very welcome.

  7. Help designing a random wire antenna to work with my tuner

    I recently picked up an Icom M802 marine HF radio that includes ham bands and an Icom AT-140 antenna tuner. I have a ham license, but have been away from HF for many years and have never used a random wire antenna before.

    Ultimately I may want this on my boat for WX data, GRIBs, email and so on, but before doing that I want to get it running at home and experiment with some data over HF. I need an antenna and don't want to spend much on a pricy indoor loop or the like, and I don't have an attic. I live on a small lot with an HOA and based upon the layout it's best physically to use an end fed long / random wire. I would like to operate on 80 to 10 meters, although I'm not sure I have enough space for that.

    The house is on a slab and all the plumbing is plastic. The radio needs to go on the second floor. Fortunately there is a window that leads out to a roof and I can put a mounting hook into the side of the house. I can also mount the tuner there (it's designed for outdoor mounting). This would give me 20 or more feet above ground.

    The tuner has a screw lug to connect the end of the long wire, but I'm concerned about connecting the wire directly to the tuner. I don't know how strong that lug is.

    The tuner manual says to avoid multiples of half wavelength as the radiating element, and says if I use a 15 meter wire I can operate all marine bands from 1.6 MHZ to 25 MHz. Further, consulting this link is helpful:


    This would rule out a 49 foot 2.5 inch (15m) length due to wanting to use 80 meters but allow 71 feet, although I may not have enough space. I could do 40 feet for sure. If I do 40 feet I can go between two points on the house (preferable because the house won't swing in the wind) but for 71 feet I would need to go to a tree on someone else's property (which I can do if need be).

    My questions are:

    Can I string the wire between two mounting points and use another, shorter wire from the tuner to the antenna wire? It could be very short, like a foot or so.

    If the end of the antenna has to go directly to the tuner, I'm concerned about a strain relief so the tuner mount point is not damaged. That's why I asked the above question. Is there a better approach?

    How do I do a ground or centerpoise? The tuner is supposed to be grounded, so do I put a ground rod into the dirt and run a wire down to it? Would that be a centerpoise?

    Can I use the ground lug of an electrical outlet as a counterpoise?

    Can I use a wire shorter than 71 feet for 80 meters effectively? The tuner manual seems to imply that I can use antennas less than 1/4 wavelength in length.

    What type and gauge of wire is best to use for the antenna? Can it be insulated to prevent rust?

    I know this is asking a lot, sorry, but I would greatly appreciate the help, thanks!!

  8. What is a diode for in a JFET-based audio mute circuit?

    I've build the following audio mute circuit:

    enter image description here

    It works fine. However in many circuits I've seen people add an extra diode on the gate of Q1:

    enter image description here

    For instance, see "QRP Classics" page 120 / page 159, or google for "JFET Audio Switch". I gave it a try but didn't notice any difference. (Nor should I expect any according to the theory of how JFETs work.)

    What is this extra diode for?

  9. How do I set the spectrum scope gain on the Icom IC-7300?

    I have an IC-7300.

    When observing weak signals, the spectrum scope has signal peaks that are way too small. Just now I was listening to a clearly audible CW signal that was easily heard but hardly moved the spectrum scope at all. I had to squint at it!

    I'd like to set the gain of the 'signal scope' (not the waterfall!).

    I can set the reference level of the scope, but this only shifts the zero-value of both the spectrum and the waterfall up/down. I can set the Waterfall Peak Color Level, but this only changes the gain of the color scale of the waterfall. It does not set the decibels per vertical line in the scope itself.

    How do I set the gain of the spectrum scope?

    Compound image of two Icom 7300 screenshots, one with a small and the other with a large deflection of the spectrum scope.

  10. Help me find a book about starting my own AM radio station [closed]

    I am looking for a book that will tell me everything I need to know about starting my own radio station (not an online station). Everything from purchasing a frequency to the equipment I need to playing music over the airwaves.

    Ideally, the book would include how this was done in the 1970s or 1980s, but that's not a requirement.

  11. 1/2 wave dipole instead of 1/4 wave + ground plane

    I have a transceiver operating at 150MHz using a 1/4 wave vertical whip and horizontal ground plane at 90 degrees.

    My end user doesn't like the antenna sticking up in the air (trip hazard) so I'm looking at a lower profile solution.

    Is there any technical reason why something like this dipole couldn't be scaled up to suit 150MHz?

    I have run some rudimentary tests with lengths of wires and a simple dipole seems to work but I'm not sure if a pcb trace would perform as well as a wire.

  12. Do I need a precision wattmeter or will a $50 one suffice?

    My transceiver has a built-in wattmeter but I've decided to buy an outboard one to monitor the antenna system before it reaches the ATU. I'm capable of putting out 100 Watts and I see that several manufacturers offer meters in the $50 range that look to be adequate for my purpose.

    On the other hand, I see that there are a lot of hams who have opted to spend around 500 - 750 bucks for a portable, lab-grade wattmeter. Is it really that critical to get another 3% - 5% accuracy to be worth the additional cost? Obviously, there are many who believe so. What am I missing to see here? Would I be wasting my money to buy a cheap meter?

  13. After upgrading the firmware on my IC-7300, there's a new preset in a language I can't understand, what is it?

    I recently upgraded the firmware on my Icom IC-7300 and a new menu item appeared: "Preset". I assume this is a way to save different radio configurations but I haven't looked into it yet. Inside "Preset" there were two items, FT8 which I'm familiar with and another written in a language I don't understand:

    enter image description here

    I guess it's Japanese, but I don't speak so I can't be sure. What does it say? What is it?

  14. Transmitting high-speed PWM over RF

    First, let me apologize in advance if this isn't the correct exchange to post this question on.

    I have a 50 MHz PWM signal (it's actually a 50 MHz 50% DC clock with a 1PPS clock embedded with PWM) that I would like to transmit over the 2.4 GHz ISM band with as low latency as possible. My original thought was to digitize the clock with a high-speed ADC, then stream the samples to GNU Radio and transmit via SDR, then recover on the receive side and playback the samples with a high-speed DAC. The problem I'm running into is that the only capture cards I've been able to find capable of running at the sample rate needed (>500MS/s) and streaming in real-time to GRC are prohibitively expensive ($8000+).

    My question is, is anyone aware of any alternative methods of transmitting the 50 MHz PWM over ISM? I would be willing to entertain a different method of streaming to GRC or an entirely different setup. I don't know of any radios that could take the signal as input directly and transmit it, then receive it and output it directly, but admittedly I am new to the world of RF so it's possible there's a solution that exists that I'm simply unaware of.

  15. Bandwith for streaming multiple channels

    what is the preferred bandwith for streaming multiple channels? How does the antenna affects the frequency when your hosting in the computer?

  16. Baofeng UV-9G unlock

    I have a ham and a gmrs HT. I read that my GMRS radio can be unlocked, so I don't have to carry two radios with me. The GMRS radio is a Baofeng UV-9G, SoC radio (so cheap, poor selectivity) but fine for experimenting or high risk activities where I don't want my yaesu to get wet.

    I found videos for physically identical models (to my Baofeng UV-9G) which show holding PTT, Monitor, Scan, and then power on, will unlock the unit, removing all tx range limits.

    This doesn't seem to work for the UV-9G. Would anyone know of a button combo to unlock the UV-9G?

    Note: Naturally, if you are not authorized to tx on a certain band then don't. Don't want to start a flame war.

  17. Can an antenna be affected if mounted to a bull bar?

    When I say 'mounted to a bull bar' I mean the antenna being metal on metal contact to the bull bar without any rubber or fiber glass keeping the materials from touching.

    • Could this affect the performance of receiving and transmitting a signal?
    • Does the antenna transfer current to the bull bar if there is nothing in-between?

    I ask since my mounted UHF radio isn't receiving anybody long range, whereas my handheld does.

    Extra info:

    My Mounted UHF radio is: GME TX3520

    Antenna: GME AE4702 6.6DBI UHF

    Handheld radio: Wouxun KG-UV8D

  18. Measuring effectiveness of vehicle bonding

    Is there any objective way to measure the effectiveness of your bonding in a mobile HF setup? Or determining when you have "adequate" bonding? I have a hard time with just throwing straps on blindly and hoping they help

  19. Type of Ground Wire for an AM Crystal Radio - I'm using a longwire antenna

    I have way too many choices for ground wire. I am using a crystal radio so I need the BEST not just what will 'get by'. I've seen solid copper 10gauge, aluminum wire etc. I've also seen wide flat Braided tin coated copper braids. This looks like it has more 'surface area'?

    My scientist side says we should use the braid from my radio, through the window and down to the Ground rod. (more surface area) Is that a safe bet? And I'm going to use a 'regular' cheapie wire to run under the horizontal long wire tied to ground as a counterpoise.

    Appreciate any information.

  20. Looking for specifications for Wilson Electronics WAU 420 amplifier

    Hey there helpful people I'm trying to track down some specifications on a Wilson Electronics WAU 420. I have no idea on its exact age but guessing its from the late 90's. It's likely UHF band and probably 12v DC. The other end is just the Wilson Electronics Logo.

    WAU 420 Amateur Amplifier

    Ideally I'd like to get these numbers before I try to operate it. I'll be posting a different question to try and run down the power connector part number so this will just be the specs unless someone turns up a manual.

    • Input frequency range:
    • Input power min/max:
    • Output Power min/max:
    • Expected Duty Cycle:
    • Current draw min/max:

    I've tried searching online and because of the model number I get more drug related hits than I can filter out.

    Wilson Electronics no longer does anything but Cell Boosters(amps). Wilson support suggested contacting RoadPro (I have) which purchased the Wilson Antenna brand, but they are mostly CB/antenna/headset focused. (RP Support asked if I had the box).

  21. What happens if I “open” a folded dipole so that the two wires are not connected anymore?

    A folded half wave dipole consists of two wires in parallel with only one of the wires driven, but the ends of the two wires electrically connected. As I understand it (and I may well be wrong there) the folded dipole still behaves similarly to a regular half wave dipole because effectively an almost identical current gets induced in the parallel wire without the feed point. However because only one wire is directly fed, meaning the feed point sees only half the current, impedance is quadrupled (half the current at the same power means quadrupled impedance).

    If that’s “all”, I wonder whether it matters if the wires are actually connected. If I remove the connection between the two, having essentially a normal dipole with a parallel parasitic dipole next to it, will the antenna exhibit similar characteristics as a folded dipole?

    Or did I misunderstand completely?

  22. For an HF antenna I am using a mesh dipole (10sq meters) with surprising good results on 7MHz how does it work?

    enter image description hereI try to use attic antennas I experimented an antenna made of 10sqM of chicken grid with excellent results how to calculate the aperture of such an antenna the first resonance is 3.6 MHz and the use of twin lead allows for a resonance on 7MHz the ratio of power output to rf measured by the rf meter before the antenna is close to 0.9.

    I tried many configurations different areas of grid and length of cable. I was using a Rig Expert antenna analyser, the results seem better than my usual dipole and many ssb qsos were made, barefoot, up to the other side pf the ocean. However as says N6BT when the conditions are good you can make a dxcc with a light bulb, which is why I try to understand a bit more. I could not model this antenna with the usual antenna softwares and I suspect something about antenna aperture and capacitive antenna.

  23. Centre pole construction for 20 metre half wave dipole

    I am about to embark on the construction of an inverted V half wave dipole. It will possibly be multi-band but, for the moment, I want to build it for 20M. Because of the shape of my property, I would like the centre pole to be as high as possible to give me the correct angle for the inverted V. I thought that I might be able to make this from sections of aluminium tubing. I even sourced a company that would supply these but I have carelessly lost the page and can't seem to get it again.

    So, basically, can anybody tell me the best material to use for the centre pole and possibly how I might source it. I would also be grateful for any suggestion as to the type of wire to use for the actual antenna.


  24. Is it possible to use LimeSDR/HackRF with DireWolf?

    I was wondering if one could use DireWolf with the LimeSDR/LimeSDR Mini/HackRF. The bandwidth would be much more acceptable than even the highest rate sound cards, which rarely reach even 192 khz.

    Can this be done?

  25. Where can I find a service manual for the TECSUN PL-660 to replace the failed circuit board flex cable myself?

    Diagnosed three nonfunctional TECSUN PL-660 radios (one from eBay Anon-CO, and two from Amazon) where can I find a service manual to replace the failed circuit board flex cable board assembly part? Demonstration video of failed circuit board flex cable board assembly part = youtu.be/4XbAnSX2FHk

  26. Implementing a BPSK and 4-FSK transmitters in GnuRadio (GRC) with USRP?

    Currently trying to transmit a BPSK and a 4-FSK(MFSK) signal via GRC using USRP, I have two attempts at it but don't seem to be going anywhere. Still fairly new to GRC. For the BPSK, how will this signal appear on the spectrum analyzer? I have seen general images of the signal shape online but pretty sure what I see is not it. Will I be able to hear the BPSK signal, if so what will it sound like?BPSK Flowgraph

    As for the 4-FSK, I seem to have something but the spikes I generate are at different amplitudes in comparison with a FSK signal I had generated a while ago that had the spikes at the same/similar amplitudes.4FSK Flowgraph

    I can share my flowgraphs if it helps. Also it would be great if anyone had known working flowgraphs for these concepts to share for comparison or even be able to edit some features of mine. As for the details I care about, I really need to be able to specify the excursion/deviation between the spikes.

  27. FT-450D not transmitting with microphone

    I've been using FT8 on my Yaesu FT-450D for quite some time. I decided to try to talk on phone frequencies and discovered neither one of my mics will transmit. My mics are the original hand mic and a Heil headset. I've tried all bands and cannot transmit on any of them. I had successfully talked on the radio but not now. The only change I have made was to change from a switching power supply to a linear power supply. The radio will not transmit on either supply. It only transmits in digital modes. Does anyone have any ideas?

  28. How to send DMR SMS using MMDVM modem or hackrf?

    I have a baofeng DMR radio with SMS feature, and since there is not much DMR radio owners in my area I want to do something myself.

    The easiest thing I can do I thought is to send myself some SMS as I did with a POCSAG pager using my hackrf one.

    But I haven't found any software to do that. All I found is MMDVM-SDR program on github which acts as a MMDVM modem utilizing a fake serial port. It allows to get commands from the MMDVM-Host and modulate them as IQ WAV file.

    There is one problem: that MMDVM modem protocol has no commands to send DMR SMS. It only accepts "DMR DATA packet" at different rates. I tried to google for "DMR AIR interface" but it also has no mentions of SMS.

    By that time I learned that DMR SMS is a non-standartized thing which leaves me with this questions (one is part of the another):

    • What format all those TYT and Baofeng radios is using, where I can get it's datasheet.
    • How to make a DMR SMS packet for my radio and send it to a MMDVM modem emulator or directly to the SDR using some other modem software?

    PS: I tried to record my radio's signal with SDR and play it back. With voice it works, I can hear myself, but with SMS it doesn't work for some reason: my radio just ignores them (maybe that is because it's number in both from and to fields?)

  29. Audio frequency used for Morse code in licensing exams?

    Back when Morse code proficiency was required for certain radio licenses, what audio frequency was used by the exam tapes, equipment or examiner that generated the Morse code audio? Was there a legal or recommended testing standard for this audio tone frequency?

  30. How can I protect equipment against a lightning strike?

    A lot of aerials (almost by design) would be rather good attractors of lightning. What steps do I need to take in the field to keep my gear safe against a lightning strike?

    I'm presuming the obvious already here (such as not operating in a storm), but are there any additional steps I should take?

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