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.

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9
votes
2answers
3k views

How much RF energy do trees and branches absorb?

For the 20m - 10m and 6m bands, will having my dipoles below the tops of trees (I live in redwood forests) drastically affect the RF power out or radiation patterns of my dipoles if I can still get ...
2
votes
2answers
344 views

Horizontal dipole for a 80 foot span?

I have the K1JEK Cobra UltraLite and it works exceptionally well. However that was when I had a larger yard. Moved to a house with a smaller lot and now can't use the JEK Cobra (max span between trees ...
8
votes
1answer
644 views

Do I need a SWR meter for a basic 2 meter antenna?

I have a 5 watt 2 meter handheld transceiver and want to build a helmet with an antenna, microphone (with VOX enabled) and earpiece for the radio. For the antenna part, I just want to do something ...
20
votes
2answers
3k views

How do Handheld antennas work without ground?

Dipoles have the 2 wires going to each leg of the antenna completing the circuit. Big AM towers use the second wire as a ground plane But how to handheld rigs transmit and recieve with just one wire ...
9
votes
1answer
133 views

Antenna modeling on non-uniform terrain

I'm interested in modeling the radiation pattern of wire antennas for hf before I invest the resources necessary to erect the antenna. I'm familiar with tools such as 4nec2, but from what I can tell ...
8
votes
3answers
2k views

Will anodizing or powder coating or wetcoating (painting) antenna elements affect performance?

I want to put up a small tower and beam on my roof, but I don’t want the aluminum to “stick out” and want it to be unnoticeable as possible. I would think black anodizing would be the best solution ...
8
votes
4answers
2k views

Has a vehicle magnetic antenna mount ever caused a road accident?

Some people believe that mag mount magnets lose their effectiveness over time, eventually causing a dangerous situation as the antenna could rip loose from the vehicle and become a projectile or ...
6
votes
2answers
226 views

75 watts and a mag mount antenna

I am planning to get a Yaesu FT2900R 2 meter rig for my 2001 Honda Accord. With my 5w FT60, I wasn't able to reach repeaters that were any more than 10 miles distant (I live among mountains.) How ...
8
votes
4answers
10k views

How to improve VHF/UHF Baofeng UV-82 HT reception in vehicle

I have a Baofeng UV-82 dual-band (2m/70cm) HT with an SMA male connector for the stock "rubber-ducky" antenna. I would like to use it in my vehicle. I would like a high-quality magnetic mount dual-...
5
votes
1answer
918 views

How to calculate power loss between radio and antenna

I have a 5W HT that only kicks out about 1W by the time it hits my antenna (which I understand is the norm). How do I go about calculating power loss in various equipment?
8
votes
3answers
879 views

What is the proper way to ground your station's antenna?

I don't understand how you would go about giving an RF ground to your antenna. Would it not become an additional radial and affect the signal? What is the proper way to ground your station's antenna?...
6
votes
2answers
920 views

Does a tube based HF transmitter need an antenna tuner?

With the adjustments on a transmitter such as a Yaesu FT-101E, is there any purpose for an antenna tuner, or can you accomplish the same thing by adjusting the loading and other controls?
23
votes
4answers
8k views

What is the relationship between SWR and receive performance?

If an antenna analyzer shows 1:1, does that mean it's an ideal receiver as well? And what about the converse, will a well performing receive antenna show a 1:1 SWR? I've wondered this for a while, ...
2
votes
2answers
126 views

What simple method will measure decoupling betwen two antennas?

I have 2 antennas which are quite close to each other. I would like to have at least a rough idea of the decoupling between those 2 antennas. I do not own a network analyzer. I was thinking of using ...
8
votes
3answers
665 views

What gain do I need to talk to SO-50 with my HT?

My HT has 5 W of power, a sensitivity of about 0.2 µV, and I would like to talk to the SO-50 with it. How much gain do I need in my antenna to make this work?
10
votes
1answer
877 views

Can I have multiple inverted-vee antenna fed by a single coax?

A friend who recently received his call is planning to setup an inverted-vee for 40/20m bands. Our take is the signal will take the path of least impedance into the correct length antenna wire. ...
12
votes
6answers
20k views

Calculating Antenna Length on the FCC Exam vs. in Reality

I have seen the following formulas for calculating half and quarter wavelength antennas: Formula for $\frac{1}{2}$-wavelength antenna (in free space): \begin{equation} \mathrm{Length~(feet)} = \frac{...
6
votes
1answer
7k views

How to find the front-to-back ratio given an antenna radiation pattern diagram?

I know that the front-to-back ratio is 18dB in the below antenna radiation pattern diagram, but I don't know how to read the diagram to obtain this result. How does one read and understand such ...
8
votes
2answers
5k views

Phasing harness for antenna array

I understand that certain antenna designs (particularly phased arrays) require feeding each radiating element with a certain number of degrees of phase separation in order to achieve a desired ...
7
votes
2answers
1k views

Practical 80m vertical wire antennas without radials?

We'd like to install an antenna for 80m at our club/contest station. Our club, OH2K, is housed at a school, and we can't fill the roof with a radial mesh. The roof is not metallic itself, either. We ...
2
votes
1answer
107 views

Interference generated by antenna placement?

I'm thinking about putting up a 80m dipole in the back yard, the only place I have to put this (can't do inverted V since I don't have a high enough location) is close to a overhead telephone wire. ...
10
votes
3answers
562 views

How to Evaluate Antenna Data

I found some data on antennas that had been tested for a specific radio. I'm trying to decipher what this data means and how one would go about gathering it. Are there any good resource for learning ...
17
votes
8answers
24k views

Should I chose a vertical or a horizontal HF antenna?

If I only have the budget for one HF antenna, should I chose a vertical or a horizontal antenna?
5
votes
1answer
323 views

How do I determine antenna spacing?

How do I determine antenna spacing so that I don't end up overdriving the front end of a receiver when transmitting?
13
votes
3answers
33k views

Good wire for wire antenna?

What properties should I look for in a good wire for building a wire antenna? Could anyone recommend something specific for me?
5
votes
2answers
116 views

Abilities to limit antenna use?

What kinds of abilities does a Home Owners' Association (HOA) in the United States have to limit the use of antennas placed on a roof to an owner of a home in the area?
2
votes
5answers
483 views

Metal for antenna construction?

What do I need to consider when choosing metal for an antenna? How do I determine what thickness to use?
3
votes
2answers
8k views

Antennas I can effectively use in an apartment? [closed]

What are some antenna designs that balance manageable size/shape with effectiveness for use in an apartment?
8
votes
2answers
783 views

Vertical antenna on HF?

What are some of the advantages and disadvantages of using a vertical antenna on high frequency? Are there any better antenna types that I should use?
2
votes
1answer
754 views

What antenna to use for medium frequencies in an apartment building?

I'm living at the 6th's and top floor of an apartment building. I have a balcony with a metal balustrade. Above the balcony there is a metal roof rail. I need an antenna which won't be noticed by the ...
18
votes
1answer
3k views

How does moving a feedpoint off-center in a dipole affect the resonant frequency and resistive load?

Specifically, I understand that OCF dipoles change the SWR, but does it do this via reactance or resistance, or both?
7
votes
1answer
3k views

How big can an antenna be before I need planning permission in the UK?

Presumably setting up a 1m high antenna in a back garden isn't going to be an issue, but setting up an 80m high antenna would likely cause complaints! How high an antenna can I legally construct in ...
18
votes
3answers
7k views

Why do I need to tune an antenna?

I've heard that when an antenna is set up, it needs to be tuned to reduce reflective power back into the radio. Is this always necessary, and if so how would I go about tuning it?
26
votes
11answers
26k views

What's a cost-effective way to boost the range of my cheap 2m/70cm handheld?

I'm a very casual/beginner level ham and as such have mostly avoided committing too much in the way of financial resources - I have a UV-5R for a personal radio, anything else I do I've used others' ...
15
votes
4answers
2k views

Are there federal laws (US) protecting antenna installation?

Are there any federal laws or FCC guidelines that allow ham radio operators to install antennas? I live in an apartment building in a large city that bans outdoor antennas. I recall reading that the ...
8
votes
2answers
992 views

What are some drawbacks to delta loop antennas?

They seem to be broadbanded, small, and ground-independent relative to other cheap wire antennas, so what's the catch?