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Questions tagged [antenna-system]

The system composed of an antenna and a feed line, and possibly also an RF ground connection, antenna tuner, balun, phasing device, et cetera.

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31 views

ISOTRON 80m 75m Antenna Position

I know, a dipole is the way to go, but cannot fit one, only a 'birdhouse' antenna like the 75m 80m Isotron antenna. Is it better to put at 15 feet Above Ground Level outside, or 20 feet AGL ...
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2answers
56 views

Using two VHF antennas vs one because of a large obstruction

We have a VHF Omni directional antenna, 2.5 W and 119 MHZ (approximate) mounted on top of a commercial hanger. Access to the antenna is out of the question because of the lack of fall protection. ...
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5answers
116 views

How to match low impedance of NVIS Dipole?

I want to match a 50-ohm coax feed wire to a 40-meter NVIS half-wave dipole. NVIS antenna examples I've found are usually based on a regular dipole (72 ohms in free air). However the impedance drops ...
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1answer
79 views

Counterpoise wire voltages?

One practice which seems common when operating temporary or portable QRP, SOTA, etc., is to throw a counterpoise wire out on the park lawn or shrubbery, mountaintop or hillside or parking lot ground, ...
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2answers
53 views

Grounding of a portable setup

I am occasionally using an extremely simple shortwave portable setup consisting of a battery, the transceiver, a short coax feedline and a vertical half-wavelength vertical antenna with a transforming ...
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3answers
75 views

How does the Maximum Power Transfer Theorem relate to RF power amplifiers?

The Maximum Power Transfer Theorem says that maximum power transfer occurs when the source impedance equals the load impedance, when the power transferred to the load is 50%, the other 50% being ...
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1answer
152 views

How does a higher antenna reduce rain static on a lower antenna?

I have operated at several stations - including my own - where a 40m beam is stacked above a tribander. During a rain storm, there is so much QRN on the 40m beam that the band is unusable, but the ...
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0answers
36 views

How to simulate two antennas in 4nec2

I need to simulate 2 helix antennae placed side by side, and see the resultant radiation pattern. But after adding the second antenna with a separate and when I try to simulate 4nec2, only simulated ...
4
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1answer
41 views

Antenna system components in the rain

An antenna system often consists of more than the feedline and radiating wires: such as fixed or tapped loading coils, LC traps, baluns, toroids, air variable capacitors, roller inductors, feed horns, ...
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1answer
74 views

Is this antenna “system” really work? [closed]

I posted yesterday asking how can I have signal inside my house which my house is obstructed by a hill from direct signal from the cellular's operator' Base Transceiver System (BTS). The schema of the ...
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2answers
112 views

Understanding RG6-75 ohm Cable Impedance

Here is my measurement to a piece of RG6 cable. It is around 30cm cable. On the shield is written COAXIAL CABLE 5C-2V 75 ohm. From my measurement I got data as below: From that table, we can see that ...
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4answers
160 views

What is the maximum and minimum of antenna gap of dipole antenna?

Consider the picture below is design of half wave length (λ) dipole antenna. I read some explanations saying that it is the best design to get the optimum transmit power. Half wave length (λ) is from ...
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1answer
65 views

What happens when you directly couple the transmitter antenna to the receiver antenna?

I was wondering what happens when you directly electrically couple the transmitter antenna to the receiver antenna? Particularly I’d like to know what happens for FM radio broadcast. Since I don’t ...
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3answers
137 views

Why have knife switch storm grounds for antennas vanished?

Long ago, it was fairly standard to provide lightning protection for outdoor radio antennas by installing a large double-throw knife switch -- antenna leads to the center, radio on one side, ground on ...
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3answers
731 views

VHF 50 Ω Antenna Over 75 Ω TV Coax

I have a 50 Ω VHF airband antenna which I’m planning to install in my loft, for use with a RaspberryPi-based RTLSDR scanner/receiver. I already have a UK-standard UHF/Freeview antenna using standard ...
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3answers
131 views

Using 75 Ω instead of 50 Ω coax feed

Can I replace my old 50 Ω coax with RG6? It's cheaper and less loss at VHF/UHF. I would match by L/2 multiples of coax to repeat input and output impedance or L/C matching networks at each end. Is ...
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3answers
185 views

Passively reducing ground loss?

Would a disconnected wire or conductive mat below a low height antenna reduce ground losses? A tuned length of wire under a wire antenna might be suitable for NVIS gain. But would a bunch of space ...
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6answers
319 views

Is it practical to use a slug-tuned variable inductor in an antenna matcher (aka “antenna tuner”)?

I will soon need an antenna impedance match (aka "antenna tuner"), because I'll initially only have a single antenna for my HF rig (needs to cover 80m, 40m, 20m, 15m, and 10m). Obviously, in order to ...
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1answer
180 views

Is it safe to run two barefoot rigs on one antenna with an AB switch?

I have a Daiwa CS-201A two position switch. The single side is connected to by quarter wave vertical (40m). The A and B sides are connected to an IC-7300 and TS-830S. The switch is claimed to have ...
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2answers
272 views

Bow Tie antennas impedance

I see on the internet that a radio amateur made bowtie antennas for transmitting and receiving on the 2 meter and 10 meter bands. They produced very good SWR bandwidth when fed with 50-$\Omega$ coax. ...
6
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1answer
125 views

Why does adding 50-ohm BNC Ethernet terminator(s) in parallel to my 4-element yagi improve my radio's reception? (70cm)

I have this radio, with a rubber duck antenna, and a repeater twenty miles away to my north-northwest. If I set my radio on the top of a cabinet in my bathroom, I receive the repeater fine. I can't ...
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2answers
129 views

What additional information do I get from an RF ammeter, as compared to a regular SWR/wattmeter?

I've grown up using SWR/power meters. They're "simple" devices: They show forward and reverse power, and show the standing wave ratio. They, however, do not show antenna efficiency. New hams are ...
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2answers
257 views

Share wide band antenna with multiple transceivers

I'm trying to incorporate several transceivers on my board design; I need WiFi (2.4 GHz) SatCom (~1.6 GHz) RF (~900 MHz) and GNSS (~1.5 GHz). I need to combine them into one antenna. I found a wide ...
5
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1answer
68 views

How to model passive elements when simulating an antenna?

So I started writing an antenna simulator program to design antennas for my needs. To calculate the electric field vector at every point, I split the active element of the antenna into a large number ...
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3answers
177 views

Output power curve of an antenna

My approach is that a radio wave is made from zillion of accelerated electrons which emit zillions of photons. Since the current flows in a open circuit, the antenna generator works against something ...
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4answers
4k views

How does the signal know where the cable ends and the antenna starts?

I know very little about antennas. I know, that for a certain frequency the antenna needs a certain lengths for good sending/receiving conditions. Often the antenna is at the end of a cable. Why doesn'...
5
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1answer
306 views

Are Elevated Radials Necessary for Elevated, 5/8-wave “Ground-Plane” Antennas?

Currents at the base of an elevated, 5/8-wave, vertical ground-plane (GP) transmit antenna are lower than when that vertical conductor is 1/4-wavelength. Does this mean that the performance of the ...
2
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1answer
114 views

Stacking DB8 “bedsprings”

I'm trying to receive a UHF TV signal 86 miles away. Considering the height of the transmitting antenna and the height of the receiving antenna, I should be able to just make line-of-sight between ...
2
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2answers
359 views

G5RV Jr. fed with ladder line and coax

I am a new ham and I was just given a G5RV Jr. I have about 20 feet of coax plus about 60 feet of 450 ohm ladder line I can feed it with. Can I extend the G5RV Jr. feed line with the ladder line I ...
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5answers
535 views

How did hams manage to tune their antennas before VSWR meters?

In the early 20th century --back when the hobby was still new-- before VSWR meters and antenna analyzers were invented, how did radio operators know whether they were tuned for maximum power out? ...
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1answer
104 views

How is RF Power at Receive Antenna Output Terminals Calculated?

Is the Friis equation sufficient to make this calculation? Must other considerations also be evaluated?
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2answers
114 views

True near field distance for a short monopole antenna?

Antenna properties: Height x Diameter = 3.3 inches x 1.4 inches Test Frequency: 900 MHz (Wavelength = 33 cm or 13 inches) I see some conflicting formulas to calculate the near field distance for ...
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5answers
280 views

Signal path to maximize RFI rejection in an urban environment

Urban ham here (Cambridge, MA - FN42ki - KC1JZE) looking for tips to make this hobby possible in the city. I rarely can hear both sides of HF phone transmissions, and have yet to make contacts despite ...
6
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1answer
170 views

Two antennas on different sides of a building

I live in the 4th floor of a building with one side facing south and the other north. I am able to use my 2M mobile base transceiver with a mobile magnet mount antenna placed just outside the window. ...
3
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1answer
144 views

How high an SWR can the USRP 2901 (B210) handle?

I connected a USRP 2901 (B210) to an amplifier I designed. The USRP seems to shutdown every time I try to transmit. I guess I messed up with the input impedance matching on the amplifier. Is it the ...
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3answers
167 views

Radio stops receiving as soon as the antenna is threaded all the way

Is it normal for the antenna conector of the radio to have 18ohm resistence between the inner socket(signal) and the thread (ground)? When I connect the antenna works fine if only the inner plug ...
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1answer
97 views

Electrical Earth

I have moved to a new flat which is on the 4 floor, luckily the landlord has let me put an OCF dipole outside with coax feeding through an existing hole in the window frame. I'm looking for some ...
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4answers
2k views

Why do we distinguish between balanced and unbalanced?

I hear all the time, "you need a balun between your balanced dipole and unbalanced coax to stop the common-mode current" when it seems the proper advice is "you need something to stop common-mode ...
5
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3answers
631 views

Lightning strikes nearby and coaxial cable

A direct hit on my home by lightning is very, very unlikely. However, many lightning strikes that hit Earth nearby are by far the main hazard for ham radio gear (in my opinion, after 60 years in the ...
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3answers
379 views

Attic Dipole - Impact of Ethernet over CAT5/6

I've been thinking about putting 20m and 10m dipoles up in my attic (HOA), but I also intend to soon put some Ethernet cable to a WAP (with PoE) through the attic. I was intending to feed this with ...
9
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1answer
181 views

Does Coax Limit the Maximum SWR a Transmitter 'Sees'?

A recent discussion about SWR led to the assertion that a length of coax cable will ultimately limit the SWR to which the transmitter will be exposed. By experimenting with an SWR calculation tool ...
5
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4answers
376 views

TV strong station has no signal when coax is connected

Right, not directly ham radio related, but this puzzles my ham brain. I have several TVs connected to a distribution amp connected to an outside antenna. All but one work fine, and the one won't ...
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2answers
252 views

Using one of two antenna tuners connected in series

I have: A Kenwood TS-590SG. 2 antennas up, a tri-band beam and a fan dipole. I run both antennas to a MFJ-998 auto tuner. I also have a MFJ versa tuner IV. The auto tuner works good for 80-10 meters ...
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2answers
515 views

Do the radials of a quarter or 5/8 wavelength antennas connect to the braid of the coaxial cable?

I'm studying for my foundation license (in the UK) and I have these diagrams: Do the radials in a quarter or 5/8 wavelength antennas connect to the braid/shield of the coaxial cable? If so, how does ...
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1answer
161 views

Two devices + one antenna

What I have: GSM 900 repeater 900 - 2400 MHz MIMO antenna 2xSMA MIMO 4G Router works with 1800 MHz LTE Is it a good idea to connect GSM repeater via SMA splitter to one of the antenna cables? Will ...
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2answers
52 views

Determing short or open location in antenna system

I have a G5RV antenna. It used to work fine. I had it disconnected for several months. Now I can't get it to load. I think there may be a short or open in the coax. Is there a way to determine how ...
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6answers
852 views

Use a TV coax and balun for a poor-man's OCFD?

Can I use TV coax and a cheap TV balun to build a poor-man's OCFD? Marginal performance is acceptable if it saves money. If I could listen to 10% of transmitters within a 100 mile radius that would be ...
9
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5answers
2k views

What is an antenna tuner? Why bother with resonant antennas in the first place?

There are a lot of antenna tuners on the market that have various capabilities in terms of how they can allow random radiators to work with our transceivers. What exactly do they do? My ...
2
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2answers
542 views

Grounding Help - Where To Route My Wires

Here is my situation. My antenna mast is on the opposite side of the house from my ham shack, same with the power service entrance. I have installed ground rods roughly every 16 feet with #6 wire ...
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2answers
684 views

G5RV Jr and Ladder Line feed Lying Flat on the Roof?f

a semi-old, mildly grumpy, damn lazy new General Class Op, back after nearly 40 years since last license. Live in an old 2 story Mediterranean Sunset District Avenues home with a flat, beam-bitumen-...