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2
votes
4answers
246 views

Does a resonant antenna work better than a non-resonant antenna?

Some books on antenna fundamentals i've read recently say that, for a half wave resonant dipole when transmitting for example, the traveling wave of movement of charges reflected back from the ends of ...
1
vote
3answers
84 views

Practicality of SDR-based TX/RX

When it's not possible to be at the same location as a TX/RX appliance, some form of remote control is needed. There's basically two ways to TX/RX: classical radio appliance, with or without digital ...
0
votes
4answers
209 views

For a half wave dipole antenna, what's the value of the reactances that cancel out when the antenna is resonant?

According to a few descriptions of antenna fundamentals i've read recently including that in Wikipedia and the ARRL handbook, when a half wave dipole is resonant, the inductive and capacitive ...
0
votes
3answers
74 views

What is minimum resolution for 2 frequencies to interfere each other

I started working with HF frequency. Right now, I am working with 7 MHz frequency. I have been provided a range of 7-7.5 MHz. I have to divide that range into 132 distinct frequencies to assign each ...
1
vote
1answer
37 views

Why does the APRS specification suggest to use 7-bit ASCII for user-defined data formats?

The APRS specification document says the following: Although there is no restriction on the nature of user-defined data, it is highly recommended that it is represented in printable 7-bit ASCII ...
4
votes
3answers
254 views

Common-mode current and choke placement

Why are chokes usually placed at the feedpoint, can't common-mode currents occur below the choke as well? I understand it's placed at the feedpoint to keep everything balanced by eliminating common-...
0
votes
2answers
41 views

How Duty cycle affects transmission rate in RF module?

I planning to use RF module for communication of high precision GNSS module. So I am doing detail study on RF module. In one of the datasheets of RF module (part no: RFD868ux) mentioned that 'Duty ...
1
vote
2answers
38 views

RF PCB Design Difference Between Controlled Impedance Track and Impedance Matching Circuit

Im new on RF circuit designing. Im designing an circuit with GSM and GPS capabilities. I know when using high frequency signals the RF traces must be impedance matched. Now what I understand is, I can ...
5
votes
2answers
635 views

How to calculate power transmitted by monopoles?

I only studied monopole in sending mode or receiving mode alone but never in both modes together, I have this question which says: Two vertical λ/4 monopoles are parallel to each other with 20 ...
2
votes
0answers
51 views

Buzzing FM interference

What kind of interference or other receiver issues can cause a constant buzzing noise (picket fence lines in the audio spectrum) in the demodulated audio of a received NFM VHF signal? With AM, it ...
3
votes
1answer
139 views

Is it legal for an unlicensed person to transmit as long as they are under the direct supervision of a licensed amateur?

Based on another question here, I think it is legal, but I would like it directly from the people who know. Thank you for your time.
3
votes
1answer
41 views

Can I have the Hytera PD785G turned on in the charger?

I have a Hytera PD785G. Typically, I charge it overnight, then take it out and use it. Since this is currently my only radio station, I'd like to misuse it as a stationary device. Most of the time, ...
0
votes
4answers
198 views

Send on-off radio signal 5,000km

I remember long range radio stations which still worked 30yrs ago. I could listen to the whole Europe. I also think I saw movies where radio enthusiasts could talk all over the world.. I never looked ...
7
votes
2answers
201 views

Importance of Ferrite Size in Coax Choke Balun

The question is quite simple: When making a coax choke balun, does the size of the ferrite matter, and if so, why? I have seen design notes that say to use a single FT240-43 toroid for powers up to ...
4
votes
1answer
172 views

Change of Address and Callsign Zone

I'm about to permanently move to another US state, which is in another callsign zone. Will I be forced to get a new callsign in the new zone? Also, when I started, when one was traveling in another ...
3
votes
1answer
64 views

impedance matching with window twinlead

Question from new ham here, regarding ways of matching impedances between a feedline and an antenna. Is it possible to fashion a broadband HF impedance matcher from a length of windowed twinlead, in ...
2
votes
2answers
195 views

What is the current state of the art in CW filters?

In the 1970s I made a CW “filter” based on a phase locked loop that detected a specific audio frequency, and this drove an NE555 oscillator: the result seemed at first like a “zero bandwidth” CW ...
3
votes
1answer
81 views

How does this 3 dB splitter/combiner work?

I'm having difficulties to understand how does this circuit work: Apparently T1 is a regular 50 Ohm to 22.2 Ohm autotransformer. Turns ratio 2:3 gives a 0.66**2 impedance converation. Since the load ...
0
votes
2answers
58 views

Built-in ATU vs Remote?

I have two antennas in my station: a 10-15-20M yagi, and a loaded 40M vertical. With the ATU built into my Kenwood TS-450S I can operate 80, 60 a and 30M with the 40M vertical too. Though, in 80M I ...
4
votes
1answer
43 views

Easy Digi hum with isolated ground

I am creating an Echolink simplex link using a Raspberry Pi 3 B+, a Pluggable USB sound adapter, and an "Easy Digi" sound card interface which has 2 - 600ohm isolation transformers for audio in/out as ...
-1
votes
1answer
40 views

remote push to talk or process background sound out

how to set up remote push to talk I work in an extremely really noisy area headset connected to some radio but others can do remote push to talk and hear me answer I need my hand for working what ...
1
vote
4answers
144 views

Can't identify old Chinese(?) and American radio/telephone

I have searched image banks and Googled period radios, but I can not identify these old units. I picked them up overseas in SE Asia and I got them as projects to teach myself enough to challenge the ...
2
votes
1answer
100 views

Should I not have “painted” my YAGI?

I have a 5 ele YAGI which, once we can go multi-op portable again in the UK, I shall be taking to the hills with me. The idea being to make it quick and simple to get the dimensions and element ...
4
votes
2answers
785 views

Beginner listening to a repeater - only hearing one station

This morning I tuned in to a repeater about 12km from me (in the UK). I could hear activity, but from only one station. I could tell that there were other stations using that repeater from the ...
0
votes
4answers
98 views

Variable polarization Yagi using two antennas on the same boom, joined together with variable feedpoint phase?

I have been trying for ages to find a way to mount a 10 m vertical Yagi properly, so that the mounting pole doesn't stuff up the impedance and radiation pattern, and have had no luck so far. Apart ...
1
vote
2answers
53 views

What is the formula for coupling between non-parallel wires?

I want to solve the equations for wire antennas where the wires are not all parallel. The classic method for parallel wires is to compute the magnetic potential at points on one wire due to current ...
0
votes
1answer
46 views

How do I trigger hotkeys on AnyTone 878UV?

I've read the manual twice, and watched programming guide videos on youtube, but while I can program hotkey 1-6 just fine, I can't find how to actually trigger them. I found how to trigger the "Fun ...
2
votes
0answers
63 views

Vertical antenna near power and cable lines

I have a 40M vertical on top of my roof. When I transmit at 100W, my internet drops. My neighbor's internet too (different cable company). At 50W it seems to be OK. As an expermient, I used a smaller ...
6
votes
4answers
327 views

Any reason not to choose a discone antenna over a Wide/ MultiBand mobile antenna for TX/RX operations

We are setting up a all-band radio in an emergency com center that's intended most for amateur band use, but since its' for emergency use will also be used in the public safety bands; (150-170)MHz, (...
0
votes
1answer
38 views

On a horizontally setup 20m delta loop I am looking to determine the calculations for the proper length of a feed wire

Base of loop will be about 6 feet above ground. RG-8 or 213 will be used for the feed wire. Ugly balun as well.
2
votes
1answer
60 views

Contesting dialog

I have noticed that participants in an HF exchange will often give number and a letter followed by a state, e.g. 1E Wisconsin. What does this mean?
2
votes
1answer
67 views

How Much Does the Radiation Pattern of an “EFHW” Antenna System Vary Across its Bands?

This NEC4.2 analysis shows one example of such variation.
1
vote
1answer
101 views

When are licenses required for 900 MHz operation in the US? When are they not required?

Forgive me if this is not the proper forum, but I am an electrical engineer and a total radio novice. I am designing a product that may contain off-the-shelf industrial radios that act as repeater ...
0
votes
2answers
75 views

Antenna Basics - Open/Short Circuit & Half-Duplex/Full-Duplex

I am beginner in the Antenna theory and I have a few basic questions. Please help me to clarify my understandings related to the basics which I have read. And this question has 3 basic questions. ...
2
votes
2answers
85 views

Modelling a “fan dipole” or “fan inverted vee” using EZNEC - unexpected result

I plan to put up a "fan inverted vee" but for various reasons I will not be able to take it down, adjust wire lengths, put it up, test, etc: I will basically have to cut the wires, put it up and leave ...
1
vote
2answers
35 views

How to connect IC-271 DC power connector to 12 V battery

What I am trying to do Radio is an IC-271, ~ 20 years old. I want to run it with a 12 V lead acid battery. I need to connect the battery to the radio. The radio's DC power connector is a 6-pin molex(?...
1
vote
5answers
267 views

Significance of 1/4 wavelength with respect to antennas

I am a fresher in the radio design field. My question is, 'What is so significant about 1/4 wavelength with respect to antennas.' From the information I have gathered from various sources, it is my ...
1
vote
3answers
120 views

Need antenna for mobile mag-mount LPFM broadcast 88.3 MHz

I am doing some temporary FM broadcasting for car events such as COVID-safe car parades and drive-in movies. The terrain is horrible, urban areas with lots of buildings. The cars snake around a city, ...
4
votes
1answer
168 views

Using a trap out of its resonance frequency?

I have a vertical antenna, about 7M total length, with a loading coil at 6M height. This is just because aluminium tubing is sold in 6 meter lengths. The loading coil is used to make it resonate at 7....
2
votes
1answer
70 views

Can these in-band spurs from rpitx be eliminated somehow?

I'm putting together a 2m NBFM transmitter/receiver combo using rpitx and rtl-sdr. During testing my low-pass filter I discovered that rpitx is generating spurious signals within and around the band (...
1
vote
4answers
132 views

Determining one exact antenna length for a whole band (e.g. FM/AM broadcast, Bluetooth and others)

How does a single FM antenna length work in the entire FM frequency band range, when there are theories which state that the antenna size should always be close to wavelength/4 for proper reception &...
0
votes
1answer
71 views

Yaesu FT-817 Won't transmit Dig, SSB or CW

I have a problem with my Yaesu FT-817 it Won't transmit Dig, SSB or CW, But it does transmit AM, FM and Pkt on all bands. Does anyone know what the problem might be. The Radio receives fine on all ...
0
votes
3answers
132 views

Virtual Testing | How would it be done

How would testing be done on Zoom? Or would testing be pushed off until after COVID-19?
2
votes
2answers
81 views

Is a balun really necessary for a small loop antenna?

I am in the process of designing a small receiving loop antenna for the lower HF bands. By small I mean a circumference of less than $0.2\lambda$. Thus, a uniform current distribution can rightly be ...
3
votes
1answer
109 views

Grounding for lightning safety - upper floor (UHF/microwave antennas)

I have some UHF, microwave antennas and an antenna rotator on a roof mounted mast. The "radio room" is in the second floor just below the antennas. Also the service entrance for building electricity ...
3
votes
1answer
38 views

Bias Tee for HF: noise and losses?

I have a homebrew remote antenna switch. It uses relays and it has a nRF24L01-based wireless link to the band selector (Arduino, taps into CAT and switches antennas accordingly). I would like to ...
5
votes
1answer
142 views

Can half of a directional antenna (Yagi-Uda, HB9CV) be replaced by a ground plane?

Consider a center-fed dipole antenna. It‘s well understood how the bottom element can be replaced by a ground plane (in practice, generally a few rods but in principle a conducting plate would work as ...
3
votes
2answers
42 views

Problem of two SAW fitler?

When I series two SAW filter, why the attenuation less than sum both of them in stop band region. Each of them (in stop band) have 60dB attenuation but when series them, the attenuation is equal to ...
1
vote
1answer
61 views

how does this collinear antenna work?

I was looking for a cheap and easy to build 2M/70cm vertical. I found this: http://vk2zoi.com/articles/dual-band-high-gain-flower-pot/ Here are the plans to build it: But I don't really understand ...
3
votes
1answer
41 views

How do I get my Windows 10 PC to consistently recognize my RigExpert AA-35 ZOOM?

I have connected my brand new RigExpert AA-35 to my Windows 10 PC via the provided USB cable, but the AA-35 does not show up in Device Manager. There is no COM port assigned to it, nor does it show ...

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