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.
75
questions
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3answers
73 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 ...
4
votes
1answer
147 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 ...
3
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0answers
34 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
votes
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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vote
1answer
73 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 ...
0
votes
2answers
100 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 ...
2
votes
4answers
151 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 ...
1
vote
1answer
60 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 ...
3
votes
3answers
125 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 ...
2
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3answers
725 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 ...
1
vote
3answers
123 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 ...
7
votes
3answers
181 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 ...
6
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6answers
295 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 ...
5
votes
1answer
177 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 ...
2
votes
2answers
232 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
votes
1answer
120 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 ...
5
votes
2answers
120 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 ...
5
votes
2answers
254 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
votes
1answer
66 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 ...
-1
votes
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 ...
19
votes
5answers
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
votes
1answer
281 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
votes
1answer
113 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
votes
2answers
338 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 ...
9
votes
5answers
463 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
113 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 ...
5
votes
5answers
256 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
votes
1answer
161 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
votes
1answer
139 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 ...
4
votes
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 ...
3
votes
1answer
92 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 ...
6
votes
4answers
1k 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
votes
3answers
589 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 ...
7
votes
3answers
367 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
votes
1answer
177 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
votes
4answers
364 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 ...
2
votes
2answers
243 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 ...
0
votes
2answers
478 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 ...
1
vote
1answer
159 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 ...
0
votes
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 ...
7
votes
6answers
821 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
votes
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
votes
2answers
515 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 ...
0
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2answers
659 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-...
1
vote
1answer
271 views
Wide bandwidth HF power combiner schematic and formula
I want to build (not purchase) a wide bandwidth power combiner.
It should combine signals from 2 TFD antennas cut for 15 MHz lower frequency and used for receive only. Upper frequency is 30 MHz so ...
9
votes
3answers
550 views
Stealth HF station setup advice
I need some advice on setting up my first HF station in a somewhat restricted townhouse community. If I had a detached house with a backyard I’d probably already have everything setup. But with this ...
3
votes
3answers
652 views
What is the point of high gain antenna with respect to the maximum EIRP
OFCOM states that the maximum EIRP within the UK for 2.4 GHz is 100mW. Simply put, what is the point in being able to buy 2.4 GHz high gain antennas which can say do 24dBi, which already puts the ...
0
votes
1answer
203 views
guard planes in differential antenna PCB designs
The designs I have seen all seem to have this surrounding stitched-to-the-ground copper pour surrounding them. Why put it on a differential antenna PCB like below ? And why are those thin lower left ...
6
votes
4answers
1k views
What exactly is impedance?
I see "impedance" used everywhere.
Equipment has an input and output impedance.
Antennas and feedlines all have this 'impedance' thing.
For someone that understands DC electronics, Ohm's law and a ...
