# All Questions

3,079 questions
Filter by
Sorted by
Tagged with
43 views

### Kenwood TH-D72A and AO-91/92

I got a Kenwood HT and using it with the Elk Antenna On the radio, there is Tone and I set it to 67 Hz. I wasn’t able to break thru to the satellite and had it in Full Duplex mode. I can hear ...
116 views

### For a resonant 1/2 wave dipole, does the reflections being in phase with the applied signal cause the zero reactance seen in the feedpoint impedance?

For a resonant 1/2 wave dipole when used for transmitting, does the fact that the reflected waves on the antenna are in phase with the applied signal result in zero reactance at the feed point, or ...
113 views

### Musty smell in old equipment

I recently came into possession of number of old ham radio and a variety of old test equipment. Items from to 1960s to the 1980s. Several of the items have a strong musty smell. What can I do to ...
105 views

### Using shortwave communication, how difficult is it to transmit messages from the UK to the US?

Is it possible to transmit a short message across the Atlantic ocean from the UK to the US via shortwave? From what I understand, long-distance shortwave communication has lower bandwidth than other ...
59 views

### Is shortening a half wave dipole to make it resonant by removing the inductive reactance a good idea?

A dipole which is exactly one half wave length allows reflections within the antenna to be in phase with the applied signal. To me it seems that this situation gives an antenna which will produce the ...
102 views

### For an antenna when used for transmittiing, what is the optimum radiation resistance?

For a 100 % efficient antenna, the real part of the impedance is equal to the radiation resistance. If the antenna were a dead short with zero impedance then the radiation resistance would be zero. ...
58 views

### Most accurate way to measure signal power with (cheap) Spectrum Analyzer

I am using an USRP X310 which is unfortunately not calibrated and the specs given are only very vague. Hence I would want characterize the device with first-order measurements. Unfortunately I only ...
68 views

### What does “HF-QUARTZ 4.19 MHz” on a ~1980s wall clock mean?

I have a wall clock from the 1980s or early 1990s. Probably 1980s. It has a black box behind/"inside" it which powers the whole thing. It's made by Quartz. On the black box, it says "HF-QUARTZ 4.19 ...
33 views

### How to calculate combined power of two amplifiers

If I have 1 amplifier running at 95%, and another identical one running at 60%, how may I calculate the output power of the combiner? I believe this combiner is a "Magic T", but if there is a ...
64 views

### How to fix SignaLink non-linearity problem?

I decided to check the linearity of my Yaesu FT-891 signal using an RF sampler and an oscilloscope. To generate two-tone (1550 Hz, 2150 Hz) signal I used Audacity. To connect the transceiver to the PC ...
72 views

### fldigi will only start the second/third time

Starting sometimes after 2nd sometimes after 3th times. Just now PC fresh booted, then console and fldigi started. and 2. start hangs after the two messages "Silicon_Labs_CP2105_Dual_...." start ...
29 views

### In which cases do SAW filters improve performance?

I am looking for ways to improve reception between two of my devices. The communicate on the 868 MHz ISM band with a 2-GFSK modulation. The problem is that one of them is heavily shielded by metal (...
51 views

### What causes differences in properties of ferrite cores from same material?

Why are the shapes of the impedance curves different for cores made of the same ferrite material? The impedance (Z) of an inductor wound on a ferrimagnetic core is: Z=j\omega L_s + R_s = j\omega ...
97 views

### Modelling a folded dipole

I am looking at using NEC to model a $0.5\lambda$ rectangular folded dipole, for closely spaced larger sides (choosing a separation of $0.01\lambda$). In Antenna Theory, Analysis and Design by ...
108 views

### What exactly makes an antenna resonant?

When an antenna is resonant, the impedance seen at the feed point is purely resistive and has no reactance. What are the physical properties of an antenna that actually make it resonant and how do ...
36 views

### Which specification is exceeded for a transistor output stage in a transmitter when there is a high SWR? [duplicate]

For a transmitter which has an output stage which uses one final output power transistor, when the SWR is high, it's common knowledge it seems that the output transistor can get hot and fail due to ...
25 views

### Power supply for shortwave portables

I have the Tecsun PL-310ET and PL-660 SW portables which are spec’d for 5V and 6V power sources respectively. Would it damage them if I tried to power them with a 9V Bioenno battery (actual steady ...
111 views

### Supershield or Superscreen coax: Does it exist? What is it's common name?

I'm sure this seems like a google question, but I've BTDT and come up empty The problem I'm trying to solve is to obtain cables that are as "leak proof" as possible. Tried Pasternak "100% shield" ...
104 views

### What is a good step resolution in tuning and transmitting?

When constructing a new radio, what should your step resolution be and what is considered too much in resolution in frequency tuning and transmitting? I'm talking about capacitor type tunning. ...
83 views

### How can a half wave dipole which has an impedance of 73 + j43 ohms ever be resonant?

Is it true that for a half wave dipole, cancelling out reactance using for example a gamma match does not make the antenna resonant at all, but rather just cancels out the reactance of what is ...
79 views

### Can I use a “bunny ears” TV antenna for RTL-SDR?

I'm trying to get into SDR and was planning on buying an RTL-SDR. For an antenna, I was thinking of using an old set of bunny ears I have lying around. However, I first want to make sure that they'll ...
55 views

### To obtain operating privileges after the 2 year grace

I have been under medically supervised treatment for the past few years. I have been on heavy meds. I presently am showing signs of improvement from cognitive issues which were troubling me. I ...
57 views

### What is the delay through a 1:4 Guanella balun?

I need to estimate the signal delay through the 1:4 Guanella balun shown here: Is the delay simply the delay through the winding on CORE1 or CORE2? For example, assume each winding comprises 0.1-m ...
168 views

### Why do watches with GPS receivers have an “airplane mode”?

I noticed that watches with GPS signal receivers made by Seiko and Citizen have an airplane mode. If it's a GPS receiver, it shouldn't cause interference, right?
42 views

### Can I use a directional coupler to block reflected AC current from a mismatched antenna?

Is there any kind of directional coupler device such as you find in a SWR meter that only allows traveling AC waves of one direction to pass which i could use to block the reflected wave from my badly ...
25 views

### Can received and transmitted signals on the same antenna combine to produce standing waves?

Standing waves are seen on a transmission line when for example there is a change in impedance and a transmitted wave is reflected back from one end and then the incident wave and reflected wave ...
82 views

### If i transmit on the same frequency using two separate transmitters joined together will they both add up in a reciever to produce a stronger signal? [duplicate]

If i were to use a passive transmit coupler to connect two transmitters of equal power output to the same antenna, and connect one microphone to both transmitters, and then transmit on both at the ...
123 views

### Is it true that standing waves on a transmission line don't cause failure of transmitting devices?

Actual standing waves have nothing to do with causing the output device in a transmitter to fail, in fact it's the reverse or reflected current which helped to create the standing waves which is ...
2k views

### Why do amateur radio operators call an RF choke a balun?

When using a balanced antenna such as a half wave dipole, with an unbalanced feed line such as coax, an RF choke can be used to block RF current emitted by the transmitter from splitting up at the ...
62 views

### Repeater identification ending (CW)

I am just starting to learn CW, and for practice I have been recording and transcribing repeater identifications that I hear. This is what I heard today: DE W9KIC/R BBG What is the meaning of "BBG"?
114 views

### What is this military radio?

Please help me identify this piece of equipment. It looks military spec, but don't know anything about it. I want to look up some history about what it was used for. Here are more photos.
44 views

### 40 meter band Dipole antenna designed is not receiving any signal at 2 km distance

I am using a Pixie transceiver, giving 1 W power and 7 MHz frequency. A 40-meter band dipole antenna, providing 5 dBi gain at high angles, has been designed and connected at the output of the circuit ...
63 views

### Does an antenna work the same for pure sine waves as compared to other waveforms?

Antenna theory it seems is always described assuming that the transmitted or received signal being talked about is a pure sine wave usually at the resonant frequency. Standing waves for example are ...
93 views

### GMRS not transmitting within a half mile

I recently got my GMRS license from the FCC, and I wanted to try out a couple radios for hiking and emergency communication. I have two tenway UV-5R pro radios (these do have an FCC ID) that are set ...
69 views

### Can any one explain E,H plane definitions?

I read in some text books that E-plane is formed by taking constant azimuth angle and scanning elevation angle from -90:90. H-plane is formed by taking a plane perpendicular to E-plane. What is ...
52 views

I'm trying to understand way which Frequency Mod block works in gnuradio. According to my intuition there should be at least two inputs: signal to encode base frequency / carrier signal Instead ...
36 views

### Required receiver for HX-1 (144.390 MHz) & NEO-6M GPS Module?

Context I'm launching a series of weather balloons as a capstone graduation project. Right now I am in the process of building the payload. I have been going over the different components of the ...
140 views

### DIY SA612 + RTL-SDR HF receiver: good on laptop, but huge wideband noise on Raspberry Pi

I recently built a SA612 mixer for HF reception. I used an USB-frequency oscilator to shift the incoming frequency up by 28.8 MHz. I used a random wire antenna outside my balcony and connected it to ...
44 views

### Shifting frequency outside of the band

In theory when i need to shift some frequency i just multiply that signal by some sin or cos wave with the right frequency and than apply LPF or HPF. But when there is a wideband complex signal with ...
67 views

### Can I build a guanella balun using single strand wire instead of coax?

I am trying to homebrew a cobweb antenna and need some help understanding the guanella balun used as described here: http://www.karinya.net/g3txq/cobweb/ This author used RG316 coax around the ...
79 views

### Is the voltage at the centre of a dipole zero only at it's resonant frequency?

For transmit, the voltage at the center of a dipole not cut in the center and fed with coax and a gamma match is zero in the center at the resonant frequency. This is why apparently a 'plumbers ...
36 views

### What is the effect of coil Q on a shortened dipole?

I made a small yagi, with the driven element being a coil loaded dipole. What is the effect of coil Q in this situation? The coils I built are 18 turns of 1.2mm enameled wire wound tightly with a ...
49 views

### Is there any 2.4 GHz tuner ICs for SDR receivers?

I have a hackrf one sdr, which i use to transmit test signals. I am using ISM bands, so I can omit transmitting my callsign, checking correct sub band (FM, digital) etc. And one of most interesting ...
25 views

### Find blocks function on Gnuradio does not work

I am trying to use Gnuradio to build QPSK transmission with satellites simulation for educational purposes. Unfortunately, I am unable to add new blocks after "find blocks" (blue magnifier icon) ...
83 views

### What causes the light and dark bands (of background noise) in an HF waterfall display?

While monitoring the 40-meter band (among others) throughout a typical day/night as propagation changes I have noticed there are often bands of very low noise (black area) and others with much higher ...
21 views

### How are Amateur Radio Callsigns created? [duplicate]

When I took the Amateur Radio Technician Exam, I was given a callsign upon passing the test. How does the FCC create that callsign? Is it completely random or do the letters and numbers have meaning?
138 views

In amature radio, users can use what is called a phone patch to enable them to use a phone to establish connection to another party or user. Phones are usually two wire and dont lend themselves to ...
138 views

### Does the FCC care about electrical arcs?

There are a lot of videos on YouTube from people who have built high voltage sources and are sending electric arcs from one place to another. Although they have no intention to emit radio waves, they ...
56 views

### Ideal Doublet Size 160-10 Meters

Is there considered an ideal / optimum length for a doublet for use on 160-10 meters when fed with open-wire feedline and a balanced tuner in the shack?
53 views

### What is the most common CW audio filter center frequency?

For older receivers with a fixed (crystal?) audio filter for CW, what is the usual center frequency of the audio bandpass of the filter? Or cut-off frequency for low-pass CW filters? For newer ...

15 30 50 per page