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Nicolas Medalla

Half Wave Dipole Antenna

1/2 Wavelength Dipole Antenna Calculator

Speed of Light = 299,792,458 m/s = 300 = s

Frequency = Operating Frequency in MHz = fo

Velocity Factor (see text*) = constant for 50 ohms cable = 0.95

Results is in meter…..

Meter -> Inch = 1 meter = 39.3701 inches


λ =  s / fo

Vertical Monopole Element = (λ*0.5)*vf

Actual wavelength approximate rounding off to = 81.3990 or 81.4 inches

Substitute from the formula for 145.000 MHz

λ = s / fo (meters)
λ = 299,792,458 /145,000,000 = 2.0675 meters

λ =  = 2.0675 meters

Converting to inches by multiplying wavelength results to 39.3701

λ = 2.0675 x 39.3701 = 81.3990 inches


λ = 81.4 inches = L

vf = 0.95

Solving for one-half wavelength:

Radiating Element = (λ*0.5)*vf  = E

= (81.4 x 0.5) x 0.95 = 38.6645 inches                      

Divided by 2 elements for upper and lower elements

= 38.6645/2 = 19.3 inches

Gap between Radiating Element = λ / 200 = 0.407 inch = G

L = 81.4“

E = 19.3”

G = 0.407”

Note: important
Adjust To the lowest Standing Wave Ratio (SWR)

  • Add 5% to radiating element ->  = 20.265 inches
  • Check SWR, using SWR/Power Meter, tune to Operating Frequency (e.g. 145.00MHz)
  • Connect cable. Antenna -> SWR/Power Meter -> Radio
  • Set to SWR / Power to test
  • Hence: if SWR = 1-1.2, Power = Radio Power Output Set, if you set your radio power to 5 watts it should be 5 watts meter reading in the SWR/Power meter.
  • If the measurements of the cut elements are correct for the Operating Frequency, fixed and finalized antenna, else if the results reading is/are not meet the ideal reading, cut both elements.


  • Operating Frequency = 145.000 MHz
  • If the SWR is high and Power is low
  • Adjust radio frequency to either higher or lower frequency to read to the lowest SWR, take note the Frequency with the lowest SWR
  • Now, example the frequency with the lowest SWR is 146.000 MHz
  • New formula New Frequency divided by old Frequency multiple by original radiating element results.

                              = (146 / 145) x 20.265

= 20.125 inches

BY: Nicolas C. Medalla, DW7NCM

HRC – Tribu Amihan

Download: PDF File

Radio Etiquette

Get familiar with the etiquette of two-way radio communication. Learn walkie talkie lingo. To make radio communication go more smoothly, over the years certain rules, or etiquette, have been established. Below we have outlined the basic etiquette a radio user should understand. It will help improve your overall experience when using your radio!

Basic Radio Etiquette Rules

  • The international radio language is English, except in cases where you are licensed to speak in some other language.
  • When using a two-way radio you cannot speak and listen at the same time, as you can with a phone.
  • Don’t interrupt if you hear other people talking.  Wait until their conversation is finished unless it is an emergency. If it is an emergency, inform the other parties that you have an urgent emergency message (see “Emergency Calls” below).
  • Do not respond if you aren’t sure the call is for you.  Wait until you hear your call sign to respond.
  • Never transmit sensitive, confidential, financial or military information.  Unless you are certain your conversations are secured with the proper level of encryption for the level of sensitivity, assume your conversations can be heard by others.
  • Perform radio checks to ensure your radio is in good working condition.
    • Ensure the battery is charged and the power is on.
    • Keep the volume high enough to be able to hear calls.
    • Regularly make radio checks to make sure everything is working and that you are still in range to receive signals.
  • Memorize call signs and locations of persons and radio stations you communicate with regularly.
    • In radio communication, you are not called by your name. Everybody has their own unique call sign. 
  • Think before you speak.
    • Decide what you are going say and to whom it is meant for.
    • Make your conversations as concise, precise, and clear as possible.
    • Avoid long and complicated sentences. If your message is long, divide it into separate shorter messages.
    • Do not use abbreviations unless they are well understood by your group.

4 Golden Rules of Radio Communication

1. Clarity: Your voice should be clear. Speak a little slower than normal. Speak in a normal tone, do not shout.
2.  Simplicity

Keep your message simple enough for intended listeners to understand.
3. Brevity: Be precise and to the point.
4. Security: Do not transmit confidential information unless you know the proper security technology is in place. Remember, frequencies are shared, you do not have exclusive use of the frequency.

Speaking the Language

General Terms Meaning
Radio/Signal Check What is my signal strength?  Can you hear me?
Go Ahead  You are ready to receive the transmission.
Stand-by You acknowledge the other party, but I am unable to respond immediately.
Roger or QSL Message received and understood.
Negative Same as “No”.
Affirmative   Same as “Yes”.  Avoid “yup” or “nope” as they are difficult to hear.
Say Again Re-transmit your message
Over Your message is finished.
Out All conversation is finished, the channel is clear for others to use.
Break, Break, Break You are interrupting in the middle of communication because you have an emergency.
Read you loud & clear   Response to “Radio Check”. Means your transmission signal is good. Also, use “Read you 5-by-5“.
Come in You are asking the other party to acknowledge they hear you.
Copy You understand what was said.
Wilco Means “I will comply”.
Repeat Used before you repeat something. ex: “I require 9-5, repeat 9-5, gallons of diesel fuel. Over”
Marine & Aviation  
Sécurité Safety call. Alert to some safety warning. Repeat 3 times. Has priority over routine calls.
Pan-Pan Urgent call. Help needed.  Repeat 3 times. Has priority over safety calls.
MayDay Distress call. Repeat 3 times, and again following each transmission. Has priority over all other calls.
  See our section  Using VHF Marine Radios  for more information.
Q-Codes (ICAO) See our  Q-Code Aviation Guide  for a list of all Q-codes used in aviation.
CB & Ham Radio  
10-Codes See 10-Code Communication Guide  for a list of all 10-codes.
Q-Codes See Q-Code Communication Guide  for a list of all Q-codes.

These terms can be combined such as “Roger Wilco” means “I understand and will comply”, or “Over and Out” means “I’ve finished talking and I’m signing off”.

Making a Call

Follow these easy steps to make a call.

  1. First, listen to ensure the channel is clear for you.
  2. Press the PTT (Push-To-Talk) button.
  3. After 2 seconds:
    • Say “recipient’s call sign”  twice
    • Followed by   “THIS IS”   and “your call sign“.
  4. Once the person replies, convey your message.

Here’s a typical radio conversation:

            You: “4 Foxtrot 7 Mike Hotel Zulu(4F7MHZ), 4 Foxtrot 7 Mike Hotel Zulu(4F7MHZ), This is Delta Whiskey 7 November Charlie Mike(DW7NCM), Come in, Over”   (4F7MHZ is their call sign, DW7NCM is your call sign)
  Recipient ” Delta Whiskey 7 November Charlie Mike, This is 4 Foxtrot 7 Mike Hotel Zulu, Go Ahead, Over”
  You: Say your message and then say:  “Over”
  Recipient: “Roger Wilco, Over”
  You: “This is Delta Whiskey 7 November Charlie Mike, Over and Out”

Did you notice how at the beginning and end of the transmission you pronounce your call sign?  Because there can sometimes be many people listening on the frequency, pronouncing your call sign, and the call sign of the party you are calling, lets everyone know who the transmission is for. Communicating this way might feel a little odd at first, but you’ll soon get used to it. With practice, it will start to feel natural.

Emergency Calls

   If you have an emergency message and need to interrupt others’ conversations:

  • Wait and listen until you hear “Over”.
  • Press PTT and say “BREAK, BREAK, BREAK, your call sign, I have an emergency message for (recipient’s call sign), Do you copy, Over”.

Memorize the Phonetic Alphabet

  • It is almost certain you will have to use it in your conversations.
  • You will often be required to spell a certain word or name in your radio conversations to make sure you are understood.
  • Using the phonetic equivalents instead of letters will make sure letters such as ‘F’ are not misinterpreted as ‘S’, ‘T’ as ‘C, or ‘M’ as ‘N’.

Following is a list showing the international phonetics used for the alphabet:

             – ALPHA H – HOTEL O – OSCAR V – VICTOR

Download links:

Jpeg file: Radio Etiquette

PDF file: Radio Etiquette

Reference: https://quality2wayradios.com/

HRC 5th Year Anniversary

Glance and glimpse of the event…

It’s been a year since I become member of HRC, and I would say that it gives more meaning to my life as a volunteer, to feel high when there are in need for emergency or in any other volunteer works to be done.

Hope for the years to come that HRC will be a stronger and better one with purpose, even though the ups and downs we experienced, old and new members will be as one for the betterment of the group to help others in needs especially in times of disaster.

“Volunteer for me is very difficult meaning to fathom it’s an infinite as long as I live.”

Mabuhay ang HRC!!!