Linked Questions

4
votes
3answers
130 views

When a dipole antenna is fed via coax, what powers the ground-side of the dipole?

I've been trying to understand how dipole antennas work, and I believe I understand the basics when they're fed via a balanced feed line. In fact, every dipole physics YouTube video and web page I can ...
0
votes
3answers
82 views

Is there an instance where you can directly feed a half wave dipole with coaxial cable without having to worry about balanced to unbalance?

Like the question says, can you feed a dipole with coax with no ill effects? Nothing else in the system, just the antenna and the cable.
29
votes
6answers
34k views

Can I reduce RFI/noise at the antenna?

Recently, the power was out in my neighborhood for an extended period of time. I fired up my HF rig using battery power and was amazed at the lack of noise across the HF bands. When the power grid ...
3
votes
1answer
2k views

3 Band (80-40-20 Meter) Fan Dipole Tuning Question

I built a fan dipole according to the basic instructions in the SRI publication describing the theory and basic design. My questions is about next steps in tuning for the various bands. I am ...
1
vote
2answers
168 views

Loop Antenna Construction

I have a loop antenna. When I connect the probe from my oscilloscope, does the probe also act as an antenna? If so, how should I fix that? I read about feeding technique, but I still do not ...
3
votes
1answer
155 views

What is the optimum length for a random longwire on 10m?

I have all the space in the world and wish to errect a single random longwire to use on the 10 meter band only. I understand that once such a wire is very long, losses associated with the wire itself (...
3
votes
2answers
45 views

Should the earth rod be incorporated in the total length of an RF grounding system?

I have installed a grounding system just outside my radio shack and was careful to avoid a quarter wavelength or multiples thereof (for single band use), or anything in total length that is close to ...
1
vote
1answer
65 views

What lengths of coaxial feed lines should you avoid?

Are there lengths of feed line to avoid or ones that may cause problems with an antenna system? For single band use. Appendix: The run of coaxial will be for the 10 metre band. I would imagine this ...
3
votes
1answer
90 views

Is this “floating” output single-ended or differential and against GND or VCC?

I'm looking at a simple FM transmitter output (see picture). It is from the collector of a transistor and it goes through a DC blocking capacitor before the antenna would be connected. The entire ...
4
votes
5answers
6k views

Grounding a dipole

How do you properly ground a dipole (RX only for VHF scanning) to protect it against ESD/lightning? In my set up i'm putting a dipole on my roof. I've connected the two dipole elements together with ...
12
votes
2answers
4k views

Is there an optimum Antenna Feedline Length for mobile installations?

I bought a ham radio antenna mounting kit for my car that includes ~16' of coax. One end has a trunk lip NMO antenna mount, the other end has a re-solderable PL-259. I asked the sales person if it is ...
0
votes
1answer
143 views

Pondering variations on the vertical bazooka antenna

I've seen these antennas built out of coax that are called a bazooka vertical. It's a kind of 1/4 wave vertical, or perhaps a 1/2 wave dipole. Constructing such an antenna is to roll back the outer ...
9
votes
6answers
33k views

Is there a simple, DIY, antenna suitable for HF receive only?

So the antenna I'm thinking about doing might be* way too large for my property. Is there another simple, cheap, DIY antenna I could try on my receiver? I know I'm going to want to hook it up and ...
20
votes
5answers
10k views

How can I protect equipment against a lightning strike?

A lot of aerials (almost by design) would be rather good attractors of lightning. What steps do I need to take in the field to keep my gear safe against a lightning strike? I'm presuming the obvious ...
0
votes
1answer
198 views

Is shortening a half wave dipole to make it resonant by removing the inductive reactance a good idea?

A dipole which is exactly one half wave length allows reflections within the antenna to be in phase with the applied signal. To me it seems that this situation gives an antenna which will produce the ...
4
votes
2answers
559 views

Does a dipole require a 1.5:1 balun?

Dipoles ideally have 72 ohms impedance. I know most of the time this isn't what one gets and it can vary a lot. But let's assume we can build this perfect dipole that exhibits this impedance. Why do ...
0
votes
3answers
329 views

To folded dipole, or not to folded dipole?

I currently operate a 20M half-wave dipole with a balun. It's a little lower than ideal, but it gets me on the air. I've read about folded dipoles. But I've found contradicting information about them....
7
votes
7answers
8k views

What is the attraction of vertical antennas for HF?

I understand that MW broadcast stations use vertical antennas because that polarization works much better for groundwave propagation. But in amateur radio, I would assume the focus for communications ...
2
votes
2answers
119 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 ...
3
votes
1answer
115 views

Do these magnetic field measurements of end-fed and center-fed half-wave dipoles corroborate measurements made by antenna experimenters?

Using a sensor and procedure discussed in my article, I made the following plot comparing the magnetic field strength along a 30m-band half-wave dipole fed at center and one end. Key points include: ...
9
votes
2answers
9k views

Grounding VHF base station antenna

I'd like to install an outdoor dual band VHF/UHF base station antenna, a simple pole antenna like the Comet GP-1. I live in an area where lightning is rare, but not unheard of. Should I drive ground ...
1
vote
4answers
2k views

Is the ground on the back of the Icom IC-7300 an electrical or RF ground?

On the back of the Icom IC-7300 there's a ground connector: The manual goes on to say this: Is this an electrical or RF ground?
24
votes
3answers
38k views

Why are some 1:1 current baluns twice as complicated as others?

I would like to add a balun/choke to my dipole for the reasons outlined in Using a balun with a resonant dipole. In the spirit of continued kit and/or DIY building for my ham shack, I set out to ...
4
votes
2answers
7k views

Coaxial Folded Dipole Antenna Matching Impedance

In http://www.nsw.wicen.org.au/technical/projects/coaxial-folded-dipole-antenna, the guy is using a 50 ohm coax cable to build a folded dipole antenna and claims that this will enable use at 50 ohm (I ...
1
vote
3answers
2k views

How to attach a magnetic loop antenna to the 50Ω coax of an RTL SDR?

I'm planning to make a magnetic loop antenna mainly for receiving LW, MW, and SW radio broadcasting bands, as well as perhaps the 2.2km band and 630m band. (Not all of them with the same antenna, I'mm ...
10
votes
5answers
5k views

Grounding a second-story shack with an outdoor antenna

My shack is on a second story, really far away from the house ground. To run a ground from my equipment to the outside/ground is a run of at least 60-75 feet. The antenna is at least 100 feet away as ...
5
votes
3answers
1k views

Is this the Correct Ferrite Core to Reduce RFI as a Common Mode Choke?

I have a Flex 3000 connected via RG-11 coax to a inverted V fan dipole tuned for 40m and 20m on my roof. I have an "ugly" balun up on the mast by the antenna. I further have the feed-line going into a ...
5
votes
2answers
735 views

RF Antenna - V pole - Should one leg go to ground and the other to signal?

I'm attempting to follow this white paper in order to build an antenna. This is my first antenna and as such I have a rather simple question. DIY 137 MHz APT Weather satellite antenna by Adam-9A4QV ...
3
votes
1answer
760 views

Benefit to remote antenna tuner for end-fed non-resonant antenna?

Does addition of a remote feed-point antenna tuner affect the use of the coax braid as a radiator? If it no longer "radiates" in such a setup, what does? Is a shack or remote tuner better for ...
5
votes
5answers
664 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 ...

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