Questions tagged [antenna]
Questions about the design, selection, building, testing, mounting, or properties of antennas. See also specific tags: [antenna-theory], [antenna-construction], [dipole], etc.
17
questions with no upvoted or accepted answers
5
votes
0answers
170 views
Hardened UHF Antennas
Minuteman missile silos used an interesting hardened UHF antenna.
What kind of antenna is this? Does anyone have a drawing with a cross section?
Edit:
Jay Moore added a picture to a different type of ...
3
votes
0answers
52 views
Is this author correct about using a λ/2 of wire for a coil to get the proper delay on a λ/2 collinear antenna?
Is this author correct about using a λ/2 of wire for a coil to get the proper delay on a λ/2 collinear antenna?
Improving the Super-J
August 5, 2012 by John S. Huggins
I agree with him that there has ...
2
votes
1answer
111 views
EFHW: better to get far end really high, or middle somewhat high?
I built a 40m end fed halfwave antenna and unun, and the wire is about 66 ft long. I have some tall trees nearby I can hang it in, semi-permanently.
Which of the following would be better?
A) hanging ...
2
votes
0answers
41 views
How might various conductive mast mounting configurations affect an electrically isolated rhombic antenna?
Assuming a rhombic antenna is:
terminated for directionality
electrically isolated at its mount point
mounted to a metal mast partway up vs top of mast
horizontally oriented (elements parallel to ...
2
votes
0answers
60 views
Biconical antennas - bandwidth and installation
I am posting this question (and its related question) here because of the unique expertise that Ham Radio Operators have as it relates to antennas. I'm a newish Ham and really appreciate your help ...
2
votes
0answers
48 views
Printed Dipole Transmission Line Equivalent Model
let's consider a printed dipole on a substrate with a GND plane:
I've seen many times an equivalent model which uses transmission lines like this (reference):
This model is useful to understand the ...
2
votes
0answers
243 views
What is happening in a gutter "antenna"?
can you explain me what is happening with RF in a iron gutter?
I've tried to simulate with nec2, but I'm just a beginner and doesn't really know all the parameters to come close to reality. This is ...
1
vote
0answers
61 views
Narrow bandstop filter not requiring ground connection in SMD package
I’m designing an antenna that I’ll implement on a printed circuit board. The antenna will be working on both sides of 900 MHz, so it’s not exactly for ham use. I’m planning to use a bandstop filter in ...
1
vote
0answers
56 views
How to cut phasing/transformer coax in a right way?
I'm building RHCP crossed dipole for 137 MHz satellites reception (I'm using 137.5 as a central frequency). My calcs are:
frequency is 137.5 MHz
λ is 2.18 m
one dipole leg length equals to the λ/4 so ...
1
vote
0answers
91 views
How do I Construct a Simple FM Antenna?
I recently bought a cheap stereo amplifier with built in FM receiver from Amazon at the first link below. Testing it out today I found the FM reception to be sub-par. All of my local stations that I ...
1
vote
0answers
264 views
What will be antenna impedance of a dipole antenna when it is kept lambda/2 away from the transmitter
I understand that half-wave dipole antenna, which is in far-field, impedance is around 73 ohms. If I keep same antenna in near-fied at distnace lambda/2 from the 1.25 lambda length tranmiter?
0
votes
1answer
60 views
Can I use a car antenna intended for 2m/70cm on a 868mhz Lora device?
I have a Lora radio device that runs at 868mhz, it came with a tiny stubby antenna.
I want to use the device out and about so wanted to know if it will be OK connected to a magnetic/car antenna I got ...
0
votes
0answers
36 views
What is the signal of a receptor antenna irradiated with a plane wave?
Lets say there is a reception antenna connected to a detection system with a coax, and a transmitter sends a plane wave. What happens is that the antenna gets a certain power, following the [...
0
votes
0answers
32 views
For a 5'X9'balcony up 12-18 ft I need a good short antenna for 40m USB. Openings ~5x 8 ft to west 5'X4ft to south w/3' metal balustrades
Is there a 2-3 meter long loaded dipole for the USB 40m ham band that I can use on a 2nd floor balcony?
0
votes
0answers
38 views
Troubleshooting range on Lora Radio
I am using these Adafruit LoRa radio microcontrollers: M0 radio
paired with these parts to make up the antenna system:
antenna
connector
cable
And for some reason I am unable to get much further than ...
0
votes
0answers
29 views
Titan antenna VSWR and radio problem
I just installed a new Titan DX antenna and I am using psk31 with fldigi. When I transmit on 20m at 14072, the SWR is 1.65 and it shuts off my computer and the radio keeps transmitting.
However, on ...
0
votes
0answers
31 views
Magnetic and Electric Wall in HFSS
I'm new to RF engineering and I want to ask how to draw magnetic and electric wall in HFSS software? I know magnetic Wall means open circuit in circuit model and electric wall means short circuit, but ...
