All Questions

1
vote
1answer
14 views

How to use 70 cm WiMo phasing harness for a COTS crossed yagi antenna?

In order to generate circular polarization in a crossed-yagi, a 90° phase delay is required between the horizontal and the vertical antenna. In practice, this is achieved either by making a mechanical ...
3
votes
1answer
38 views

Air Coil AM & Shortwave Crystal Radio Using 1/4" Copper Tubing

Looking to build a crystal radio, need help with the coil. I'm looking to get something to work with 1/4" thin wall copper tubing. Already have some nice diodes and whatever capacitors/resistors I ...
2
votes
2answers
318 views

Antenna polarization when dealing with satellite communications

It's easy to understand, conceptually anyway, the difference between a horizontally polarized antenna and a vertically polarized one, when referenced to ground. However, when they are pointed nearly ...
3
votes
1answer
50 views

Why were “PARIS” and “CODEX” considered “typical words”?

In the context of wondering how to convert characters per minute to words per minute, it was pointed out that CODEX and PARIS are used as typical words for measuring speed of CW operators. As the ...
4
votes
1answer
59 views

If someone transmits on 151.88 MHz and I listen on 151.18 MHz, how likely would I hear their transmission?

I have a cheap baofeng uv-5r, and I sometimes hear an intermittent transmission which pulses past the squelch threshold with periods of dead space between, roughly 0.75 seconds or less. My job uses a ...
7
votes
3answers
78 views

Can I use a helical ground plane radial in the same way that a loading coil works?

I'm working out the science behind mounting an antenna on a vehicle, and I came across the concept of ground planes. This answer says that longer is better but don't worry about it too much, but this ...
5
votes
1answer
67 views

How to determine number of turns for a 1:1 balun?

I would like to make a 1:1 balun with М1000НМ ferrite core (magnetic permeability - 1000) and 1 mm thick copper wire using triple bifilar winding. Unfortunately I didn't manage to find a clear ...
2
votes
4answers
81 views

Does a 1/2 wavelength end-fed antenna need a good RF ground?

I was searching for DIY end-fed antenna. Some of the articles I found say that for a 1/2 wavelength end-fed I need a "small to no counterpoise" (with a lambda*0.05 m counterpoise), but some other ...
0
votes
1answer
25 views

Do I need an 9:1 UNUN for a half-wave end fed?

I was using a 10-ish meter wire as my HF rx antenna. That's all I can install in my QTH. However I realised that my ~10 m wire can be turned into an end fed dipole for 20 meter band. But there is a ...
1
vote
1answer
31 views

Using LMR400 and RG8x in the same feedline

I am putting a run together from my shack to a new 2 meter antenna I've built. I'm blessed to have many trees on my property and I'll be placing the new antenna about 90 ft from the ground by hanging ...
2
votes
1answer
29 views

Triband vertical antenna 6/2/70

I wish to fit this on the house gable end, however the location has a metal phone line bracket that will be just bellow the antenna radials. Will this cause any detrimental effects?
2
votes
1answer
45 views

Are there hand held radios for both Amateur and CB?

Are there combo handheld radios for CB and amateur radio? If so, is it practical?
2
votes
1answer
75 views

Help understanding this tweet about receiving images from satellite behind the Moon

This GBTimes article A tiny Chinese satellite is orbiting the Moon and allowing radio amateurs to download images links to this tweet which shows a high gain UHF? antenna pointed at the Moon, and that'...
3
votes
1answer
74 views

Antenna for receiving 868MHz rocket telemetry: QFH(QHA), Helical, or?

I'm building a radio communication system for an amateur rocket project. We've decided to use LoRa 868MHz system. My question is, which antenna for the ground station will be the best choice? We're ...
2
votes
2answers
154 views

Why does a Class-C non-linear power amp distort SSB but does not distort AM?

Can someone tell me why exactly a transistor non-linear power amplifier will amplify an AM signal without noticeable distortion, but will distort an SSB signal, giving the familiar scratchy sound ...
1
vote
1answer
59 views

Digital Modes Transmission Traffic Comparisons

I am looking for data that compares the number of transmissions per month or year among the various digital modes such as DMR, D-star and Fusion. I want to see how popular these technologies have ...
1
vote
1answer
44 views

How to measure the power emitted from an HF antenna in near-field WPT?

I'd like to estimate the power density from a 13.56 MHz power source in a near-field WPT (wireless power transfer) scenario. Using a spectrum analyzer with a receiving antenna will give the E-field ...
0
votes
1answer
92 views

Is it legal to transmit scrambled or encrypted voice via SSB on ham bands?

And also, can anyone tell me how? Using Arduino or any other way ...
3
votes
2answers
66 views

Mobile 2m / 70cm dual band with aviation frequency TX capability

Forgive what may be a basic inquiry from a new enthusiast. I am new to amateur radio, just barely passed Technician and General tests. I am also a pilot and have an RR class licence. I believe that I ...
2
votes
2answers
114 views

Can anyone tell me how to make a 35 m long wire antenna work on 80, 40, 20, 15 and 10 metres?

I have one straight horizontal wire antenna 35 meters (114.83 feet) long. I want to make it work the best on average for the 80, 40, 20 ,15 and 10 meter amateur bands. Can anyone tell me the best ...
2
votes
1answer
127 views

Yagi-Uda antenna - energy flow density calculation

This task is our milestone, even the lecturer doesn't know how to do it, I will be grateful for even the smallest clue, thank you in advance. There are given two, identical, parallel, short dipoles ...
1
vote
1answer
47 views

Effect of small amount of metal on twin-lead

I have a G5RV Jr. antenna on a fiberglass mast at 10m height. The only metal on the mast is a 1/8" thick steel guy ring with stainless steel snap links, plus a few small metal screws. Hanging freely,...
0
votes
1answer
54 views

How to characterize and select UHF linearly loaded antennas?

Q1.1: Why can a helix calculator not be used for linearly loaded antennas? Those online calculators suggested that the turn pitch/wavelength should be around 0.25. However, a typical linearly loaded ...
1
vote
1answer
63 views

What are the differences of ham radio procedures compared to military or public safety procedures?

After reading the commentary in this question and its answer, it's apparent that ham procedures/norms/protocols/etiquette are substantially different than military and public safety radio procedures. ...
2
votes
3answers
51 views

What is “Busy Channel Lockout”? Why do I want to control this feature?

I was reading up on a radio review, and it mentioned something I was not familiar with, "Busy Channel Lockout". Unfamiliar with the term, I did an Internet Search, but didn't get back much, and for ...
5
votes
3answers
112 views

How can I determine/measure power rating of a DIY air capacitor?

I've build an air capacitor like the one described in this article, although I used 1 mm thick single side copper boards (FR4) instead of solid copper sheets. I would like to use such capacitors in my ...
9
votes
3answers
129 views

Why does ARRL license examination procedure preclude students from discovering what questions they got wrong on licensing tests

I got my Extra-class ticket some time ago. I was able to discover what my score was (the number of questions I got wrong). However, my examiner was not able to tell me specifically which questions I ...
4
votes
1answer
122 views

Why are the lower HF frequencies not working during winter day time?

Currently my location is Nepal. We use the ICOM f-7000 radios without the antenna tuner. We use the frequencies round about 5-9 MHz, for communication over distances between 150 and 400 km. During ...
0
votes
1answer
27 views

Indoor RX VHF dipole and preamplifier box

I am currently looking for a good solution to create a simple VHF dipole connected to a RF preamplifier / band pass filter. The intended use is 88-108 FM RX. I see basically two solutions for a rigid ...
3
votes
3answers
86 views

How thick should counterpoise wires be?

I would like to use a shortened whip antenna with a coil in it's base, e.g. OPEK HVT-400B. My transceiver maximum power is 100 W (and antenna's - 120 W). To make the antenna work I need counterpoise ...
6
votes
2answers
442 views

Feed-through Capacitors

I'm in the "information gathering" phase of a RF Power Meter project and the design I fancy (W7ZOI Power Meter) calls for a feed-through capacitor at the output port. I understand that a feed-through ...
8
votes
2answers
92 views

What is the purpose of the German CW exam if it is not required to use CW?

To receive the amateur radio license Klasse A (HAREC) in Germany it is since 2005 not required anymore to pass a CW exam, due to a corresponding change in the Radio Regulations. However, the exam is ...
1
vote
3answers
94 views

Can I use two yagi aerials back-to-back for a bi-directional system?

I need to create a setup where I have three radio transceivers (869.4MHz) setup in a straight line. I need to be able to communicate, in both directions, from the centre pole to the outside two poles,...
3
votes
3answers
98 views

What equipment do I need to receive radio and connect to PC for listening

A great many moons ago, I spent a 24 hour period with a HAM radio connected to a PC, and listening to transmissions from a massive number of sources. Some of the transmissions included Morse, RTTY, ...
4
votes
3answers
97 views

Testing for 'Bad' Coax

I have a lot of 'donated' coax that has been given to me with unknown provenance. I'm wondering what things I can do that can determine whether I keep it or send to the tip? Some of the things I have ...
5
votes
2answers
94 views

Is there a best ratio of L to C in a resonant circuit?

When designing a resonant circuit, for example as a local oscillator, the product of $L$ and $C$ determine the resonant frequency according to $$f_{res} = \frac{1}{2\pi \sqrt{L C}}.$$ This means that ...
4
votes
2answers
114 views

Why are hand-wound coils so common if commercial inductors are available? [duplicate]

In most schematics of ham radio receivers and transmitters the inductor is mostly given specifically as the number of turns around some certain toroidal ferrite ring (for example). This corresponds to ...
2
votes
2answers
86 views

My radio in the garage is temporarily shutting down the wifi when I key up

I have a Yaesu FT-101EE, D-104 Mike, MFJ-929 Antenna Tuner, 80-10 OCF Dipole Antenna. When ever I key up for more than a few seconds, the wifi network goes down for a couple of minutes disconnecting ...
3
votes
2answers
198 views

What are these large antenna structures (used for)?

Flying around the area, I noticed this from the air - I have tried doing some searching but have been unable to find the name of the design or its specific use; What is this massive antenna, and what ...
1
vote
1answer
66 views

Why does signal power drop every night?

I have been monitoring power of a P25 control channel (at about 850MHz). For awhile, 24 hours a day. I graphed the power over a couple of weeks and it is almost sinusoidal, decreasing significantly ...
5
votes
2answers
91 views

Do I need a separate SWR meter if the transceiver has one built-in?

I'm going to buy Yaesu FT-891 as my first transceiver. I know that I can measure SWR with it if I use FM mode and minimum power, which is 5W for this transceiver. However, I don't know whether it's ...
1
vote
1answer
75 views

High Noise Floor on 40/80m at Night

I've notice a couple of times over the past couple of weeks that the noise floor, particularly on 40 and 80, is exceptionally high as the grayline passes me into night. I'm looking at the general band ...
7
votes
2answers
98 views

How to derive antenna gain from radiation pattern

I need to calculate the antenna gain in both dimensions: azimuth and elevation. The datasheet of the antennas I am using has two different radiation patterns, one for the elevation and one for the ...
7
votes
2answers
202 views

Why say “break” and “over” on walkie-talkies instead of an automatic chirp?

My understanding of why movie characters say "break" and "over" during radio conversations is based on this answer, which says that people using half-duplex devices often will want to let others on ...
5
votes
2answers
546 views

RF Antenna - V pole - Should one leg go to ground and the other to signal?

I'm attempting to follow this white paper in order to build an antenna. This is my first antenna and as such I have a rather simple question. DIY 137 MHz APT Weather satellite antenna by Adam-9A4QV ...
2
votes
2answers
99 views

Fan dipole radiation pattern

I'm looking at dual band (2 m & 70 cm) antenna designs for my next project. A very interesting one to me is the Mighty Woof, which is essentially a fan dipole made of copper pipe. Would the ...
0
votes
2answers
56 views

Reset the sps on symbol sync block GNU Radio

I'm using symbol sync block (symbol_sync_ff) on my project and i use many different sps values that i need reset on runtime. I'm trying to reset sending clock_est tag. Is this the right way to reset ...
5
votes
1answer
517 views

Do short waves pass through or reflect off concrete buildings?

I live in Moscow, Russia and use DIY indoor magnetic loop antennas to listen amateur radio. Recently I received quite strong signals from Italy (20m, IV3UTV) and Slovenia (40m, S51CK), both operators ...
2
votes
2answers
85 views

Will wrapping an antenna around my house next to metal affect it?

My unit is 25' by 25' each side and the front is 22' across. The overhang is about one foot with aluminum and vinyl underneath. If I wrap an OCF dipole (fed with 4:1 balun) around this overhang in ...
3
votes
1answer
364 views

How do PTT buttons work?

I'm really new to this, and I was wondering how the whole PTT system works? I have a headset with microphone, and a Baofeng UV-82 radio. I know the radio has its own PTT button, but is there any kind ...

15 30 50 per page