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27 views

ALIEXPRESS Products - Fake or genuine? [closed]

Good day, For those who purchased radios from ALIEXPRESS, do the vendors sell fakes or genuine products? I'm buying a Yaesu FT-8900R which lists for approximately $100 less. If you do not recommend ...
0
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1answer
25 views

How do I connect a homebrew antenna using RX-8 to a Yaesu FT-70DR (SMA)?

I made an 2m / 70cm tape measure antenna using RG-8 coax. That part was quite a bit of fun and went fine. But when I tried to connect the coax to my Yaesu FT-70DR, the copper core of the RG-8 was too ...
2
votes
1answer
64 views

rtlsdr - hearing an FM broadcast on different frequencies

There is an FM station in my city which transmits at 105 MHz. Today I discovered that I can also hear it quite well if I set the LO to 32.6 MHz and then shift the signal a bit. I'm using an rtlsdr ...
-5
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4answers
148 views

Exactly what is the cause for the zero reactance seen in the impedance at the center feed point of a resonant half wave dipole?

Lots of explanations i've read on the internet written by ham radio operators and in some text books state that a half wave dipole is resonant when the inductive and capacitive reactances cancel out. ...
1
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0answers
42 views

Capture Uplink GSM packets using 820T2 and SDR

I am an extreme beginner with SDR. I am trying to use the 820T2 & SDR device to capture uplink gsm packets sent by my phone to the nearest Base Station. I have an Rx Monitor App installed on my ...
0
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0answers
49 views

Long wire antenna end fed random length folded back on incline

Trying to lengthen my 10mtr. end fed to 39 metres in length. To do this I need the first leg (10mtr.) to run at a lower height approx (5mtr)turning back on a dog leg, and the final 29 meters then ...
4
votes
1answer
53 views

Calculating satellite passes without an internet tracker?

Situation: You want to know when a satellite will pass in order to receive an image transmission or to work an amateur satellite. However, you cannot access internet for whatever reason, and ...
0
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0answers
26 views

What is the best handheld? [closed]

I am relatively new to HAM Radio so I’m still learning. I bought a Boafeng and of course feel like I need an upgrade. What would be the best choice?
0
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1answer
61 views

How did SMA connector size become standard?

I'm working on a project in microfluidics and it has become apparent that a significant challenge to overcome is a lack of consensus in connector design. I have been thinking about my time working ...
2
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3answers
142 views

Transmitting Video Underwater

My brother and I are considering designing and building a remotely controlled submarine. As far as experience, I have some knowledge on RC systems, and I am almost done with my General license. My ...
3
votes
3answers
125 views

Use (TV?) Log-Periodic antenna for VHF

I found this old log periodic antenna that I assume was from a TV. Could I, or how would I, use this on the amateur radio bands? My main focus would be VHF, with UHF being secondary and HF would also ...
0
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2answers
56 views

How can you receive ISS broadcast using a Baofeng?

I have a Baofeng UV-5R with stock and a Nagoya 701 (maybe fake?) antennas and wonder how I can receive voice from ISS astronauts? Do they have a schedule for going on air? I live in Romania so ...
1
vote
1answer
40 views

Adapt old AvermediaTV DVB-T tuner as SDR

I want to adapt the DVB-T AverMedia TV Pilot" tuner as a software defined radio, but it is not built on a RTL chip, so the question arises, is there some kind of driver to use my tuner as a radio?...
3
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2answers
63 views

horizontal EFHW antenna attached to gutter

I'm brainstorming methods of mounting an EFHW. Unfortunately, I have no trees, so I'm considering a horizontal gutter mount which would afford me about 70 feet. Is this workable or should I consider a ...
1
vote
1answer
46 views

Crystal Oscillator Output Impedance and Output Voltage

I am working on a project designing a 40 MHz radio transmitter, but I need some clarifications. I need to know how to calculate its output impedance. I know how to calculate common collector's output ...
0
votes
1answer
26 views

DMR code plug for Anytone d878uv

Just moved from SoCal and there were sites out there for exchanging code plugs for the Anytone 878uv. I was wondering if there are similar sites for the northeast of the US. I would love to get a ...
1
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0answers
38 views

Repeater transmit voice message/warning on input frequency?

I'm in the process of planning a UHF CB radio repeater. And I've heard there are ones around that transmit a voice message/warning on their input frequency (as well as standard output channel ident) ...
0
votes
1answer
44 views

Kenwood TH-F7E power supply troubleshooting

I have a Kenwood TH-F7E handheld transceiver, bought second-hand a bit less than a year ago. Until about 3 weeks ago, it worked perfectly, then I put it in a drawer and didn't touch it until yesterday,...
2
votes
2answers
82 views

Magnetic loop antenna: Which side of conductor is the current due to skin effect?

Contemplating a big magnetic loop antenna. Would a wide copper strip be better than a tube with the same conducting surface? Where will all the current be due to the skin effect? Would a flat ring be ...
0
votes
1answer
59 views

Problem with Baofeng BF-888 radios

I have 2 Baofeng bt-888 radios coming out of the box. The problem is that the radios still growl on all channels and the light stays green. Le Griche stops when we send a communication or when we ...
2
votes
1answer
143 views

Simple AM Radio Troubleshooting

I just got all the parts to make a simple AM transmitter from Scitoys. I followed the instructions from different websites and they still don't work. I don't know why it's not working. On my ...
1
vote
2answers
92 views

Adding and subtracting dB/dBm/dBi values

I've got a question and any clarification on that would be greatly appreciated. For calculating the pathloss in wireless communication we usually use the following formula: PL = pathloss (in dB) + ...
0
votes
0answers
38 views

How to decide between Dipole and Monopole antenna for Cubesat Uplink (433 MHz)? [duplicate]

We are currently deciding between a dipole and a monopole for uplink (435MHz) , while the monopole is easier to feed, we are unsure of how effectively we'll be able to implement the ground plane, ...
0
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2answers
105 views

How should I go about finding the transmitter or antenna of a radio signal?

This site gets many questions about people trying to track down RFI, or interesting signals picked up on radios. Often the exact location of the transmitter or the antenna would be a valuable clue to ...
2
votes
1answer
115 views

Unknown signal on 446MHz LSB (possible RFI?)

I am attempting to hunt down many sources of RFI in and near the UHF amateur bands at my home, but I stumbled across a very specific one that I have definitely never heard before. This one sounds less ...
0
votes
1answer
60 views

Sunspot numbers? forecast? broadcast on CW/HF

I have vague memories from the early 1990:s of some sort of service that broadcast something related to sunspot numbers, in CW, probably shortwave. I think the world "BOULDER" was in there ...
1
vote
1answer
90 views

How does a Baofeng radio know an incoming transmission is from a repeater?

Baofeng radio's have two menu options for squelch tail elimination (STE). Item 35 is for general simplex STE, and item 36 is for repeater STE. My question is how would the radio know if a transmission ...
0
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1answer
45 views

Dual Rubber Ducky antennas

Can I use 2 identical rubber ducky antennas with a splitter on my CB HT radio to improve range?
0
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2answers
51 views

Is there an instance where you can directly feed a half wave dipole with coaxial cable without having to worry about balanced to unbalance?

Like the question says, can you feed a dipole with coax with no ill effects? Nothing else in the system, just the antenna and the cable.
0
votes
1answer
33 views

FT8 in slow motion?

Do FT8 operators typically respond to very late replies for an entire QSO? (for instance, transmitting in the 3rd slot or 5th slot after a CQ, to maintain even/odd alternation, instead of the time ...
2
votes
3answers
103 views

How do 'plumber's delight' type Yagi antennas have a bandwidth?

For Yagi antennas where the driven element is electrically connected to the boom like the parasitic elements, how can this function without diminished performance outside of the design frequency? In ...
2
votes
2answers
71 views

Ham radio Internet gateway

How does a ham Internet gateway work? Is it possible for someone to use that to listen for my transmissions (over the Internet without needing a ham radio)? Wouldn't the Internet gateway need to be ...
0
votes
4answers
109 views

Ham radio repeater

I am wondering if using a VHF/UHF ham radio for emergency (I get injured, become ill, run out of water/food, etc.) communication while hiking the Continental Divide Trail would be possible. I see that ...
1
vote
1answer
64 views

Can sound generated by interference of cell phone signals contain any useful data?

When a cellphone is near an electronic device with speakers and someone's calling, we may hear a sound like this due to interference: Cell Phone Interference Sound Can we obtain any useful information ...
1
vote
0answers
26 views

Labview Spectral Monitoring (USRP) - Bandwidth expansion and frequency change

I connected USRP (together with antenna) to my computer to receive some signals. For this purpose, I used the built-in module "Spectral Monitoring (Interactive)". Unfortunately I noticed ...
1
vote
0answers
29 views

J Pole, what is the best way to deal with Common Mode Current? [duplicate]

I am planning on utilising a ferrite choke on a J Pole antenna for CMC. Placement directly on the feedpoint poses possible mechanical restraints. Is it okay to place it a quarter wave down the coaxial ...
1
vote
1answer
44 views

What lengths of coaxial feed lines should you avoid?

Are there lengths of feed line to avoid or ones that may cause problems with an antenna system? For single band use. Appendix: The run of coaxial will be for the 10 metre band. I would imagine this ...
1
vote
1answer
56 views

What is the optimum length for a random longwire?

I have all the space in the world and wish to errect a single random longwire to use on the one band only. I understand that once such a wire is very long, losses associated with the wire itself (a ...
3
votes
2answers
39 views

Should the earth rod be incorporated in the total length of an RF grounding system?

I have installed a grounding system just outside my radio shack and was careful to avoid a quarter wavelength or multiples thereof (for single band use), or anything in total length that is close to ...
0
votes
1answer
30 views

How lossy are gamma matches?

What are the real losses associated with a typical gamma match at a set frequency? Furthermore, are there good designs or dimensions to minimise these losses?
0
votes
1answer
29 views

Obtaining S parameters using S11 measurements?

Is it possible to obtain the S-parameters of a circuit with only S11 measurements (S11 measurement with a VNA)? My gut tells me that it should be possible by connecting open, short and characteristic ...
0
votes
3answers
77 views

How does a smartphone FM antenna work?

My understanding is the earbuds that connect to the aux port act as the antenna. It's a long wire. The problem is that the same wire is being used to power your earbuds so you can hear the radio ...
2
votes
1answer
54 views

Antenna Mast near EFHW Inverted L

I have an EFHW 40-10 in inverted L configuration on a fiberglass mast. I'd like to put an aluminum push-up mast nearby for a 6 meter antenna. How close can I get to the EFHW with the push-up mast? ...
2
votes
2answers
51 views

Why do repeater duplexers have notch cavities between transmitter and antenna?

Why are notch filters used on the transmit side of a repeater duplexer? The primary purpose of a duplexer is to keep the transmitter output out of the receiver input, since they both operate at the ...
5
votes
5answers
124 views

How can a tuner pick up a specific frequency?

The point I'm confused about is the antenna. Depending on the environment, there are tons of different frequencies passing through you (FM, AM, 4G, SAT, etc). The electrons in the wire will move as ...
2
votes
1answer
38 views

Hypothetical question: Repeater with power amplifier

This is my first time ever asking a question on stack exchange or any stack site, so please be gentle if I missed something here. I am currently working on building a UHF (GMRS) repeater, and while ...
2
votes
2answers
50 views

What are the biggest amateur radio contests (“radiosport”)?

What are currently the (5 or 10) biggest amateur radio contests in terms of Worldwide participation (total number of stations or operators on the air during the contest)? Are they the ones with "...
1
vote
2answers
76 views

Increasing communication range by boosting output and input power

ORIGINAL QUESTION I am trying to increase the range of communication between two SDRs to simulate near space communication. The output power of TX is 10dBm but I would need 37dBm for near space ...
3
votes
1answer
65 views

Is this “floating” output single-ended or differential and against GND or VCC?

I'm looking at a simple FM transmitter output (see picture). It is from the collector of a transistor and it goes through a DC blocking capacitor before the antenna would be connected. The entire ...
0
votes
1answer
31 views

Hatch Mount Antenna Selection - Dual Band 2m/70cm

I just bought a Diamond CP-5NMO hatch/lip mount and intend to put it on the hatchback lip of our 2018 Subaru Forester and, if it will fit, another one on our 2019 Kia Niro EV. I understand that hatch ...

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