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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1answer
3k views

Can I convert a telescoping antenna radio to work with an FM Dipole?

I have an older FM Radio with a telescoping antenna. Is it possible to convert that to work with an FM dipole antenna to get better reception? Such as this one. Preferably without any soldering. (I'...
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3answers
186 views

Shallow underwater wireless sensor network

I need to make shallow (max 2m) underwater wireless sensor network. Data payload is about 10kB/s. I know that VLF band (~3-30kHz) could be the best solution for that, but because of time-to-market I ...
4
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2answers
470 views

How should I mount a mobile antenna on a vehicle with a non-conductive body?

I would like to mount a self tuning antenna, ATAS-120, matched with the FT-857D transceiver. I would like to make this pair function on an ARGO 8x8 amphibious vehicle with a polyethylene body. There ...
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0answers
55 views

Interpreting the Friis transmission equation [duplicate]

In the Friis transmission equation, can you please explain the significance of the factor $$\left(\frac{\lambda}{4\pi R}\right)$$ and what it helps us achieve? Specifically in terms of path loss.
3
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1answer
2k views

How to build the smallest directional antenna (ISM band)?

What kinds of configurations should I try when trying to make the physically smallest 2.4 GHz (ISM band) antenna that is significantly directional front-to-back. "Smallest" meaning in in cm maximum ...
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1answer
175 views

How does a multi-element vertical work?

For example, Diamond makes the X700HNA which is stated as a 4x5/8 vertical on 2m. Does this just mean that it is 20/8 wavelength long vertical? Or is there some magic to phasing the 5/8 segments? I'...
2
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1answer
140 views

Ferrite Rod Price Differences

We are trying to make a VLF geophysics device for our graduate project and we need two ferrite rod antennas (desired length is 6"). Searching on the internet, we have found two ferrite rod suppliers. ...
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0answers
82 views

Best frequency for very local dense building chat [closed]

Let's say everyone has general liscense classes and can erect antennas to whatever can fit on the human body. What would be the best frequency to talk locally in an area with lots of buildings and man ...
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3answers
485 views

Copper Wire connecting log periodic elements to boom

Should I or should I not replace an aluminum wire (defective) with a copper wire on a Hy-Gain LP-1010 log periodic ham radio antenna which is made entirely of aluminum with stainless fasteners? There ...
3
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2answers
562 views

70cm antenna for an apartment

I have a blind friend who can't put anything outside, and is restricted to antennas near the window in his apartment. Luckily he lives closer to the top, which helps with range a little bit. He has a ...
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1answer
1k views

Counterpoise from artificial ground vs base of antenna

I have an MFJ-934 tuner/artificial ground for my MFJ-1699 multi-band vertical (stuck on a balcony, so limited HF antenna options), and I'm wondering if there's any downside to the counterpoise ...
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1answer
4k views

How to design a rubber ducky antenna

I am attempting to design an antenna for a 162.4 MHz omni receive only application and am confident it is going to be difficult if not impossible. I have very tight specs on space(6" diameter by 3" ...
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1answer
1k views

How much loss for 1 to 1.5 inch Coil (rubber ducky) Antenna at 70cm band?

1What is the likely antenna loss for this (coil hidden inside rubber ducky) 1 to 1.5 inches coil antenna, when placed vertically over 4 to 6 inches each side square ground plane as compare with a ...
8
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1answer
528 views

Why must twin-lead conductor spacing be small to avoid radiation?

A transmission line does not radiate when the spacing between the two wires is very small when compared to the wavelength, but the transmission line begins to radiate when the spacing between the ...
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2answers
2k views

Adequate lightning protection for sloped dipole or G5RV?

Has anyone had experience, or knows from first principles, whether installing a G5RV or dipole BELOW a "lightning-rod" in such a manner would serve as a means of discouraging direct lightning strikes ...
4
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2answers
2k views

Does antenna width/shape affect resonant frequency like length does?

I was wondering if I made an antenna from a Rohn 25G tower, would it have the same resonant frequency as a pole of the same height (assuming guys are insulated)? Also with the Rohn antenna, the waves ...
5
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2answers
144 views

How is RF a radio receives just not a mishmash of eletromagnetic energy?

So at any given time, electromagnetic waves of many different frequencies are flooding the space around me. I have a little 2 meter radio. Are not all these electromagnetic waves exciting the ...
8
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3answers
741 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?
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2answers
1k views

Best mobile antenna for the mountains

For two meters, a 5/8th wave antenna has the best omni gain. But I think the lobe is very low takeoff and not good for mountain work. What is best for the mountains on a mobile? Yes, I know not ...
4
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2answers
365 views

Resistive impedance with frequency

Full disclosure, I'm a little dyslexic. Concepts that are easy to most people usually seem ambiguous to me. I also have a had time expressing myself through writ so please forgive me if this seems ...
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2answers
721 views

Multi-part question. correct length of rg-8x coax to connect 2 meter HT to 50 ohm yagi

What it the optimal number of wave lengths of RG-8X coax to connect my Icom IC V80 HT to a 50 ohm Jetstream JTBM270 Yagi (3 elements 2m/5 elements 70cm)? Odd or even number thereof? Will running the ...
8
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3answers
6k views

Why is the electric field orthogonal to the magnetic field from an antenna?

I've read in several places that the electric field is 90 degrees orthogonal to the magnetic field, and both are orthogonal to the direction of the wave from a transmitting antenna. What causes this? ...
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4answers
2k views

Can my small ham radio antenna interfere with WiFi in my RV park?

We live full time in our RV. We are at an RV park for the winter. They just knocked on my door and asked what kind of antenna I have on top of my RV. I told them it's a small ham radio antenna that I ...
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2answers
157 views

Reciprocity and SWR [duplicate]

If someone has a high SWR, obviously their signal will not make it out as far due to reflections. However, they will still be able to hear relatively well. I have noticed for receive, a high SWR may ...
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1answer
138 views

Magnum 257 & Firestik 3' Tuning

Trying to tune a Firestik antenna connected to Magnum 257 on my '98 Jeep Wrangler. Having trouble with SWR reading as it is reading too high (~4) after I set needle on FWD and then switch back to REF. ...
7
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2answers
318 views

Center frequency spike on software radio for mismatched/disconnected antenna

A while ago I was using a software radio receiver to perform some antenna analysis. I left the spectrum display on while disconnecting the cable and noticed that when the cable was disconnected I ...
5
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1answer
2k views

maximum acheivable range on CB radio by ground wave? [duplicate]

I have 10 watt CB radio system & 0.64 lambda monopole antenna , I think it has a 5 dBi gain . what is the maximum acheivable range by ground wave in an urban area ? If I want to increase my ...
2
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2answers
978 views

High data rate on HF & MF bands

Is it possible to transfer data at a high rate, like 1-2 Mbps, on 0.5 - 30 MHz? From Shannon's Theorem, with a bandwidth of just 300 kHz it is possible to reach 1.5 Mbps. I want to use these bands ...
5
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2answers
4k views

What are some good options for covert dual band vehicle antennas?

Would like to have a 50W mobile in my SUV, but I'm not allowed to have a big whip on the outside. What 2m/70cm dual band antennas are available that don't say, "Ham Radio Operator"? Are there three ...
2
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1answer
113 views

How can I render my 2.4GHz antenna directional?

With barely no knowledge in this field, I would like to render my antenna used with Bluetooth BLE devices more directional. I tried to shield the antenna with different kind of metals with no luck. ...
3
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1answer
600 views

Idea for better reception in crowded city

I am living in crowed area of a city. It is impossible for me to set up an antenna outside the apartment. I receive signal inside the room. I have a funcube dongle pro+ and some RTLSDR, the picture ...
2
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3answers
1k views

How to shorten the length 50 ohm characteritic impedance antenna cable

I have two 50 ohm characteristic impedance cables of which I need to shorten their length to compact my design. (put everything in to a box) The cables I need to shorten are the GPS & GSM antenna ...
6
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3answers
758 views

2.4 GHz Antenna for RC copter

What is the best omni-directional antenna design for any RC flying objects? Many times I've lost signal and my copter falls due to lost signal. (Using default antenna). Since the receiver and ...
4
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2answers
211 views

Antenna Design for specific directions

I am designing an antenna for a device and was hoping to gain some insight in the correct design direction for the antenna. The Idea: A receiver & antenna that fits in a 6" diameter by 3" deep ...
5
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1answer
257 views

What is a general procedure for aligning directional antennas?

I want to establish a microwave link (1.2GHz) between two stations using antennas with a directional radiation pattern. The stations have a clear line of sight to each other. Each antenna is attached ...
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8answers
608 views

Explain how an antenna works to an 18 year old

It's either math or magic. It seems like the only thing that will explain operation are complex formulas. If a child were to ask "how does an antenna work" what should one say, it magically changes ...
10
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1answer
222 views

What is body blocking, and does it work with a stock HT on a foxhunt?

I've heard that you might not need a special directional antenna to participate in a foxhunt, that some people are able to use their body to help determine the direction of a signal. How does this ...
1
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1answer
484 views

In which direction should single wire antenna in underground parking be pointed?

In our collective building lot we have an underground parking, in which a company recently changed a functional garage door system, since then the reception is a lot worse than before. (Like it doesn'...
4
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2answers
3k views

Can I ignore the radial elements of a 2m/70cm antenna if it's on a metal roof?

I'm looking for a dual band base station antenna, and find that many of them have short radials around the base. Due to the specifics of my installation, I need to remove them. However, it is being ...
0
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1answer
98 views

If the desired frequency is known, can an antenna tuner tune its 'x' different dimensions sequentially for maximum gain?

Assume I have rotators that are able to move an antenna in different dimensions. For example, on the x, y, and z axis. I want to automatically move the antenna to its optimal physical orientation, ...
3
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2answers
615 views

Why isn't the mast an antenna?

A lot of "big antenna" pictures show these very tall masts being used to hold up a variety of other HF antennas. The mast itself is almost always conductive, though, and I'm wondering why they aren't ...
15
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4answers
3k 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 ...
4
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1answer
336 views

What is the average fade margin required for proper operation at 2.4 GHz?

I have two radios. Sensitivity is -84 dBm and transmitting EIRP is +30 dBm. How much distance should I expect? I want it to be somewhere near about 2-3 km. Is it possible?
2
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1answer
1k views

What are the effects on an ATAS-120A screwdriver antenna with a limited ground plane?

I'm going to be installing an ATAS-120A screwdriver antenna at the corner of a metal roof building, without radials going out over 270 degrees of the plane it's on. Will this significantly change the ...
13
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4answers
3k views

Handheld Dipoles

A problem with handheld devices is poor grounding. I read from someone else's question that dipoles don't need a ground. Why don't they make little handhelds with two antennas instead of one, or a ...
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2answers
3k views

How does a Dual Band Handheld Antenna work?

Looking to get a (highly recommended) NAGOYA NA-771 37cm "Dual band (2M/70cm) handheld antenna" for my Baofeng UV-5R. If my math is correct - this is about a half-wavelength antenna for 70cm, but ...
2
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1answer
447 views

Will these wires affect antenna performance negitavely?

We moved into a new house, and I noticed these wires sticking up for some sort of tent thing for shade. •I tested the wires to the 3rd prong in the outlet, and it showed a DC dead short to ground. •...
3
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1answer
717 views

Closest antenna to an isotropic? [closed]

What is the closest antenna ever made to an isotropic antenna? That is, has the same gain in every direction in free space?
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2answers
129 views

Capacitance methods (antenna extensions, whole body as antenna) for receiving better

I have seen that there are times where reception isn't very good on a radio, but as soon as the hand is approached as much as possible to the antenna (with or without direct contact to the actual ...
2
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2answers
244 views

Can I use two antennas and coax to couple RF into my aluminum sided house?

I have an aluminum sided house, and when I'm using my HT I typically need to be near a window for it to work well. Would I gain much if I put an antenna on the roof, an antenna in the middle of my ...

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