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Constructing a Half-Wave Dipole Antenna for Baofeng UV-82 Radio: Materials, Assembly & Tuning

mat134679 17346 11
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  • #1 17653385
    mat134679
    Level 2  
    Posts: 3
    Board Language: polish
    Hello, I'm a beginner ham (you can call it that)
    I have a baofeng uv-82 radio and I would like to build a half-wave dipole for it, but I don't know how to go about it :-)
    1. I don't know what materials to use for construction
    2. In general, I do not know how to build a dipole (how to connect everything together so that it works as it should)
    3. How to choose arm lengths for the right frequency
    I am interested in listening on frequencies 136-174 (mainly around 148)
    Please help.
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    #3 17655603
    Sumar
    Level 16  
    Posts: 252
    Help: 11
    Rate: 18
    Board Language: polish
    Take this as a basis:
    Two copper pipes of 50 cm each, connected by an antenna cable soldered to the ends of the pipes.
    That is, simply two copper pipes, 50 cm long (75/148=50 formula) with a soldered antenna cable, running parallel to the pipes for a minimum length of 50 cm. And how you put it together mechanically to make it durable - let it remain your invention.
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  • #4 17655805
    mat134679
    Level 2  
    Posts: 3
    Board Language: polish
    Thanks guys for your help. One more thing, what formula should I use to calculate the length of the tubes because on the forum I met with 3 formulas and each has a different value.
  • #5 17656322
    ElekTrick
    Level 20  
    Posts: 317
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    Board Language: polish
    mat134679 wrote:
    what formula should I use to calculate the length of the tubes because on the forum I met with 3 formulas and each has a different value.
    But what can be miscalculated here? Like a half-wave dipole, it's half a wave. The wavelength is 300/f[MHz]. And the dipole is made of 2 tubes, so each tube is 1/4 wave. And it needs to be shortened by about 5%.
  • #6 17656513
    mat134679
    Level 2  
    Posts: 3
    Board Language: polish
    ElekTrick wrote:
    mat134679 wrote:
    what formula should I use to calculate the length of the tubes because on the forum I met with 3 formulas and each has a different value.
    But what can be miscalculated here? Like a half-wave dipole, it's half a wave. The wavelength is 300/f[MHz]. And the dipole is made of 2 tubes, so each tube is 1/4 wave. And it needs to be shortened by about 5%.


    I mean that, like a colleague above, he gave me a link to the formula and there are two formulas for calculating the length of the antenna arms
    AND
    There is a pattern for this:

    L = 143/f

    f= the frequency at which you want to make the dipole.

    Then you divide the result by 2 and you get the length of one arm.

    So, at 172MHz it will be like this:

    L = 143 / 172
    L ~ 0.83
    0.83 / 2 = 41.5 cm - one shoulder

    II
    The basic formula for calculating a 1/2 wave dipole (2x ¼ wave) is:
    300 / f / 4 * k = radiator length in meters
    Where :
    300 - "speed" of light propagation (electromagnetic wave)
    f - is the frequency given in MHz
    4 - is ¼ wave
    k - shortening factor (different for each type of antenna)

    And so - for the PSP frequency in the country (average around 149MHz) [and not 172MHz], it is:
    300 / 149 / 4 * 0.96 = 0.483 m (48.3 cm) one leg of the dipole times 2 .

    And there the gentlemen argued which is good and I do not know how to calculate the length of the antennas for my frequency
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    #7 17656575
    Sumar
    Level 16  
    Posts: 252
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    Only II and for that we remove unnecessary additional division 300/4 and immediately accept

    L = 75 / f * k

    75 / 148 * 0.96
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    #8 17656742
    _jta_
    Electronics specialist  
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    What is the impedance of the antenna input of this radio? Because if 300 ohms, it is appropriate to use a loop dipole.
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    #9 17656760
    c2h5oh
    Moderator  
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    Board Language: polish
    _jta_ wrote:
    What is the impedance of the antenna input of this radio? Because if 300 ohms, it is appropriate to use a loop dipole.

    mat134679 wrote:
    ...I have a baofeng uv-82 radio...

    Parameters of baofeng UV-82 available on Google without any problem.
    Typically these radios have an input impedance of 50Ω.
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    #10 17656876
    Radiokiller
    Level 30  
    Posts: 1299
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    Don't be surprised, Buddy, if your Baofeng refuses to work with an antenna other than your own.
    My UV 82 can "clog up" even with a 0 dB antenna.
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    #11 17656980
    _jta_
    Electronics specialist  
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    I typed into Google "Antennas and antenna installations" - in the first place I got Janusz Bator's book for PLN 4.40 - in this book (not necessarily from Allegro, maybe it is in the library) there is a lot of information about antenna construction and their parameters. As far as I remember, an elementary half-wave dipole is about 150Ω and does not fit into the 50Ω input. But I may be remembering wrong because Ham radio course otherwise - see Antenna types and below Parameters and characteristics of the antennas.
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Topic summary

✨ The discussion revolves around constructing a half-wave dipole antenna for the Baofeng UV-82 radio. Key points include the materials needed, such as two copper pipes approximately 50 cm long, and the assembly process, which involves soldering an antenna cable parallel to the pipes. Various formulas for calculating the arm lengths based on desired frequencies (136-174 MHz, particularly around 148 MHz) are provided, including L = 143/f and L = 75/f * k, where k is a shortening factor. The input impedance of the Baofeng UV-82 is noted to be 50Ω, which is relevant for antenna compatibility. Users also discuss potential issues with the radio's performance with non-standard antennas and recommend resources for further reading on antenna construction.
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FAQ

TL;DR: For a UV‑82 half‑wave dipole, shorten each 1/4‑wave element by about 5%; “Like a half‑wave dipole, it's half a wave.” Use λ=300/f to size elements near 148 MHz. [Elektroda, ElekTrick, post #17656322]

Why it matters: This helps Baofeng UV‑82 owners quickly build, size, and tune a simple VHF dipole for 136–174 MHz listening without guesswork.

Quick Facts

What parts do I need to build a half‑wave dipole for my Baofeng UV‑82?

Use two copper pipes about 50 cm each as elements. Solder a coax feedline at the center, one conductor to each pipe. Route the coax parallel to the elements for at least 50 cm. Build the mechanical support as you prefer for durability. [Elektroda, Sumar, post #17655603]

How do I calculate each dipole arm for 148 MHz?

Use L = 75/f·k per leg, where f is MHz and k is the shortening factor. With k ≈ 0.96 at 148 MHz, each leg is about 0.486 m (48.6 cm). Cut slightly long if you plan to fine‑tune later. [Elektroda, Sumar, post #17656575]

Which length formula should I trust for a half‑wave dipole?

Trust the physics: λ = 300/f. A half‑wave dipole uses two 1/4‑wave legs; then apply a small shortening factor. “The wavelength is 300/f [MHz].” Differences between formulas come from whether that shortening factor is included. [Elektroda, ElekTrick, post #17656322]

Do I need to shorten the calculated length? By how much?

Yes. Start with the 1/4‑wave length and shorten about 5% to account for end effects and element diameter. Trim equally from both legs. Make small adjustments and re‑check performance after each cut. [Elektroda, ElekTrick, post #17656322]

How do I connect the coax to the dipole elements?

Solder the coax center conductor to one pipe and the shield to the other at the feedpoint. Then route the coax down, parallel to the elements, for at least 50 cm. This follow‑the‑diagram approach works for a sturdy, simple build. [Elektroda, Sumar, post #17655603]

How do I build and mount it in three steps?

  1. Cut two copper pipes to about 50 cm for a 148 MHz baseline.
  2. Solder coax at the center (one conductor to each pipe) and run it parallel ≥50 cm.
  3. Secure the assembly mechanically per your design and test reception. [Elektroda, Sumar, post #17655603]

Will a half‑wave dipole match the UV‑82 antenna input?

The UV‑82 expects a 50 Ω feed. Build with a 50 Ω mindset, and use a center‑fed dipole with a 50 Ω coax. For receive, minor mismatch is usually acceptable. Keep leads short and connections solid for best results. [Elektroda, c2h5oh, post #17656760]

Can one dipole cover 136–174 MHz effectively?

A single dipole is resonant around one frequency. Performance falls away as you move far from resonance. For wide coverage, pick a center frequency you care about most, or use alternative broadband or multi‑antenna solutions. [Antenna types]

My UV‑82 overloads or desenses with an external antenna. What’s going on?

Some units can “clog up” when connected to efficient external antennas near strong signals. This is a receiver front‑end limitation. Try a smaller or lower‑gain antenna, or increase physical separation from interference sources. [Elektroda, Radiokiller, post #17656876]

Is there a more portable VHF antenna than a rigid dipole?

Yes. The half‑wave “Flower Pot” uses coax as the radiator and a simple choke, making a flexible, portable vertical. It’s popular for hand‑helds and easy to stash or mount. Follow the referenced build guide for dimensions. [Elektroda, Radiokiller, post #17657984]

Should I use a 300 Ω loop dipole for this radio?

No. The UV‑82 uses a 50 Ω antenna input, so a 300 Ω loop is not appropriate. Use a center‑fed dipole or another 50 Ω‑friendly design instead. This avoids unnecessary matching hardware for casual receiving. [Elektroda, c2h5oh, post #17656760]

Is a 1/4‑wave whip a simpler option for city listening?

Yes. A simple 1/4‑wave whip is quick to make and can work well in urban areas. It’s compact and forgiving. If you want fast results and portability, consider starting there before building a full dipole. [Elektroda, rnb_bolii, post #17653450]

How should I orient the dipole for VHF FM and public‑service bands?

Use vertical polarization for typical VHF FM services. Mount the dipole elements vertically to match the polarization of most repeaters and services in this band. Keep nearby metal away to avoid detuning. [Antenna types]

Where can I read more about dipoles and matching basics?

See the recommended “Antennas and antenna installations” book by Janusz Bator, and the linked ham‑radio course pages. They cover antenna types, parameters, and matching concepts useful for beginners. Check your local library or the provided links. [Elektroda, jta, post #17656980]
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