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Physical fundamentals of the radar principle

The basic principle of operation of primary radar is simple to understand. However, the theory can be quite complex. An understanding of the theory is essential in order to be able to specify and operate primary radar systems correctly. The implementation and operation of primary radars systems involve a wide range of disciplines such as building works, heavy mechanical and electrical engineering, high power microwave engineering, and advanced high speed signal and data processing techniques. Some laws of nature have a greater importance here.
Radar measurement of range, or distance, is made possible because of the properties of radiated electromagnetic energy.
Reflection of electromagnetic waves
The electromagnetic waves are reflected if they meet an electrically leading surface. If these reflected waves are received again at the place of their origin, then that means an obstacle is in the propagation direction.

Electromagnetic energy travels through air at a constant speed, at approximately the speed of light,
300,000 kilometers per second or
186,000 statute miles per second or
162,000 nautical miles per second.
This constant speed allows the determination of the distance between the reflecting objects (airplanes, ships or cars) and the radar site by measuring the running time of the transmitted pulses.

This energy normally travels through space in a straight line, and will vary only slightly because of atmospheric and weather conditions. By using of special radar antennas this energy can be focused into a desired direction. Thus the direction (in azimuth and elevation) of the reflecting objects can be measured.

These principles can basically be implemented in a radar system, and allow the determination of the distance, the direction and the height of the reflecting object.
(The effects atmosphere and weather have on the transmitted energy will be discussed later; however, for this discussion on determining range and direction, these effects will be temporarily ignored.)
Why Radar?

Radar has many advantages compared to an attempt of visual observation:
Radar is able to operate day or night, in lightness or darkness over a long range;
Radar is able to operate in all weathers, in fog and rain, it can even penetrate walls or layers of snow;
Radar has very broad coverage; it is possible to observe the whole hemisphere;
Radar detects and tracks moving objects, a high resolution imaging is possible, that results in an object recognition;
Radar can operate unmanned, 24 hours a day, 7 days a week.

Radar Historical Overview

 Neither a single nation nor a single person can say that the discovery and development of radar technology was his (or its) own invention. One must see the knowledge about “Radar” than an accumulation of many developments and improvements, in which any scientists from several nations took part in parallel. In the past, there are nevertheless some milestones, with the discovery of important basic knowledge and important inventions:

1865 The Scottish physicist James Clerk Maxwell presents his “Theory of the Electromagnetic Field” (description of the electromagnetic waves and their propagation) He demonstrated that electric and magnetic fields travel through space in the form of waves, and at the constant speed of light.

1886 The German physicist Heinrich Rudolf Hertz discovered electromagnetic waves, thus demonstrating the Maxwell theory.

1897 The Italian inventor Guglielmo Marconi achieved the first long distance transmission of electromagnetic waves. In his first experiments he used a wire to a wooden pole. In Italian a tent pole is known as l’antenna centrale, and the pole with a wire alongside it used as an aerial was simply called l’antenna. Today Marconi is known as pioneer of radio communication.

1900 Nicola Tesla suggested that the reflection of electromagnetic waves could be used for detecting of moving metallic objects.

1904 The German engineer Christian Hülsmeyer invents the “telemobiloscope” for a traffic monitoring on the water in poor visibility. This is the first practical radar test. Hülsmeyer apply his invention for a patent in Germany, France and the United Kingdom.

1921 The invention of the Magnetron as an efficient transmitting tube by the US-american physicist Albert Wallace Hull.

1922 The American electrical engineers Albert H. Taylor and Leo C. Young of the Naval Research Laboratory (USA) locate a wooden ship for the first time.

1930 Lawrence A. Hyland (also of the Naval Research Laboratory), locates an aircraft for the first time.

1931 In Britain the first known proposal for a radar system came from William A. S. Butement and P. E. Pollard in January 1931. They equipped a ship with radar. As antennae were used parabolic dishes with horn radiator. Although their equipment produced short-range results the work was abandoned for lack of government support.

1933 On the basis of the in 1931 from himself invented sonar, Rudolph Kühnhold presented a so called “Funkmessgerät”. It worked on a wavelength of 48 cm and the transmitter had a power of about 40 Watts. From these tests, the Freya-radar was developed, which was produced in series beginning in 1938.

1935 Robert Watson-Watt (later: Sir Robert) suggested that radio waves might be used to detect aircraft at a distance and outlined a means of doing so. Intensive research began and by 1939 Britain possessed a defensive chain of highly secret Radio Direction Finding (RDF) stations.

1936 The development of the Klystron by the technicians George F. Metcalf and William C. Hahn, both General Electric. This will be an important component in radar units as an amplifier or an oscillator tube.

1939 Two engineers from the university in Birmingham, John Turton Randall und Henry Albert Howard Boot built a small but powerful radar using a Multicavity-Magnetron. The B–17 airplanes were fitted with this radar. Now they could find and thus combat the German submarines in the night and in fog.

1940 Different radar equipments are developed in the USA, Russia, Germany, France and Japan.

Driven by general war events and the development of the Air Force to major branch of service, the radar technology undergoes a strong development boost during the World War II, and radar sets were used during the “Cold War” in large numbers along the inner German border.

How to decode the position of the aircraft from an Odd and an Even CPR ADS-B Frame?

Say you receive the following two frames:


Bytes 2 to 4 give ICAO address 75804B which is
CEB [5J] Cebu Pacific Air
Registration RP-C3191
Airbus A319

The first 5 bits contain the Downlink Format (DF).
First byte 8D is 10001-101 so DF=17 and CA=5
DF 17 means we have an extended 112 bit squitter. Not all extended squitters have the position. We need to check the Type Code (TC).

Byte 5 is the first byte of the extended squitter as such, which is an extra 56 bits compared to a short squitter.
This makes up to the last 3 bytes not included. These last 3 bytes are an error check.
The Type Code is contained in the first 5 bits which is in Byte 5 of the whole frame: 58hex is 01011-000bin
Both TC are 01011bin which is 11dec.
This TC is Airborne Position with Barometric Altitude as follows:
Airborne position with Horizontal protection limit: (HPL) 25 m ≤ HPL < 185.2 m (0.1 NM)
95% Containment radius, μ and v, on horizontal and vertical position error: 10 m ≤ μ < 92.6 m (0.05 NM)
Navigational uncertainty category: 7

This is still not sufficient, as to start decoding positions we need an ODD and an EVEN frame.
These frames contain the position in CPR (Compact Position Reporting) format.
Whether a frame is odd or even is indicated in bit 22 of the extended squitter.
As we need more binary data lets change the extended squitters into binary.

The first frame:
[TC-] [-Altitude-] T F [—-Latitude—] [—Longitutde–]
01011 000 000011111111 0 0 10110011110111111 01001101110100110

The second frame:
[TC-] [-Altitude-] T F [—-Latitude—] [—Longitutde–]
01011 000 000011111111 0 1 10101100101000001 11110101101111010

In the first byte:
First 5 bits are the TC which is 11.
A TC 11 decodes to the following fields:

Bits 6 and 7 are the Surveillance Status.
Bit 8 indicates the antennas used.
Bits 9 (MSB) to 20 (LSB) contain the altitude.
Bit 21 contains the T (Time) bit. T in this case is 0 which means we are not synchronized to UTC.
Bit 22 contains the F flag which indicates which CPR format is used (odd or even).
Bits 23 (MSB) to 39 (LSB) contain the encoded latitude.
Bits 40 (MSB) to 56 (LSB) contain the encoded longitude.

So our first frame has F flag = 0 so is even and the second frame has F flag = 1 so odd.
So we finaly know that we can use our information to find the position of this aircraft.

CPR uses several functions which are good to know before we start:

Nb is the number of bits for encoding. Airborne positions use Nb = 17 as we can confirm from above. Note Nb = 19 for surface positions.

CPR decodes positions to Zones Nz. The number of possible zones for airborne positions is Nz = 15 giving an unambiguous airborne range for decoding of 360 NM.

The floor notation floor(x) denotes which is the greatest integer k such that k

Modulus MOD(x,y) is always positive. In VB6 I have written it as follows:
Function modulo(val, modval As Double) As Double
modulo = val Mod modval
If val < 0 Then modulo = modulo + modval
End Function

The NL(x) is a big one but only returns a number between 1 and 59. In my VB6 progam I use a lookup table as described in the PDF document 1090-WP-9-14.

So our starting point is:

Lat(0) = 10110011110111111 or 92095 dec
Lat(1) = 10101100101000001 or 88385 dec
Lon(0) = 01001101110100110 or 39846 dec
Lon(1) = 11110101101111010 or 125818 dec

1. Compute the latitude index j:
Under VB6 that is done as follows:
j = Int(((59 * Lat(0) – 60 * Lat(1)) / 131072) + 0.5)
j = 1

2. Compute the values of Rlat(0) and Rlat(1):
rlat(0) = AirDlat0 * (modulo(j, 60) + Lat(0) / 131072)
rlat(1) = AirDlat1 * (modulo(j, 59) + Lat(1) / 131072)
Const AirDlat0 As Double = 6
Const AirDlat1 As Double = 360 / 59
This gives
rlat(0) = 10.2157745361328
rlat(1) = 10.2162144547802
Note: Southern hemisphere values are 270° to 360°. Subtract 360°.

3.NL for Rlat(0) and Rlat(1) , NL(0) and NL(1) are both equal to 59. Do not proceed from here if NL(0) not equal to NL(1).
NL(0) = 59
NL(1) = 59
Both NL are equal so rlat(0) and rlat(1) are our latitudes.

4. i being the frame to decode, the last frame is odd, i = 1, compute n(i) which is the greater of 1 and NL(i) – i
ni = 58

5. Next Dlon(i) = 360 / n(i)
dlon(1) = 6.20689655172414

6.Find M, the longitude index. You need to know that in this case T = 1 (odd).
M = Int((((Lon(0) * (nl(T) – 1)) – (Lon(1) * nl(T))) / 131072) + 0.5)
M = -39

7. Compute the global longitude, Lon
Lon = dlon(T) * (modulo(M, ni) + Lon(T) / 131072)
Lon = 123.889128586342

So there you have it!

On the second frame our aircraft was at

Lon = 123.889128586342
Lat = 10.2162144547802

Also on 2nd frame for example: Altitude is 2175 feet but that is a different story …

Communications: FCC Changes in FRS/GMRS

FRS Changes

The FCC recently changed a number of important rules when dealing with FRS and GMRS radios.  The basics are that each license class can both use channels 1 through 22 but GMRS licensee’s have access to more power (5 Watts) and FRS radios are below 2 Watts.  This is good news for volunteer groups needing to coordinate with unlicensed team members.  Combination FRS/GMRS radios were only legally usable on channels 1-14 for unlicensed persons.  The FCC ruling makes manufacturers designate FRS radios differently from GMRS radios based on broadcast power.  Existing radios are grandfathered in.  The great part is that you don’t have to limit your team to channels 1-14, all channels are available and GMRS licensed persons can run a radio dispatch using a more powerful radio and coordinate with unlicensed persons.  The license is also cheaper that it was and lasts 10 years instead of 5 years.  You may see more digital radios and features enter the market as Bluetooth and WiFi are now allowed to be used along side FRS frequencies.

This means some new features potentially to look for when shopping for FRS radios in the future would be:

  • GPS location broadcasting (like the Garmin Rino series)
  • Short text message transmission
  • Blue tooth hands free features
  • Wifi features

Dual mode FRS/GMRS radios until this point caused many people to unwittingly violate the law by using frequencies they were not licensed to use.  This also causes problems when training people because the radios don’t stop you from using a licensed channel.  The power increase (2W) is extremely useful as half a watt has very little range.

Things that have not changed:

  • FCC Part 95 frequencies still require a type accepted radio


Innexpensive radios


Inexpensive Chinese radios have flooded the market and we are seeing more and more volunteers using them.  But here is the rub, most sellers don’t understand what they are selling and don’t warn the customer.  So here are a few tips to help guide your volunteers and to develop your communications plan.

Key issue: Radio FCC type acceptance

Business band

Some Baofeng or PoFung radios (not all) are FCC type accepted for Business band.  This means if you have a commercial business band license then you can use these radios.

GMRS radio type acceptance

Even with a GMRS radio license (which covers you and your immediate family) you are still required to use FCC type accepted radios.  Baofeng radios are not type accepted for FRS or GMRS.

Why does type acceptance matter for Business band, FRS and GMRS

FRS and GMRS are narrow-band FM radio with power restrictions and antenna design restrictions.
A Baofeng radio can in theory transmit using narrow-band and low power making it possible to use a Baofeng on those frequencies (possible although illegal).  The catch is that when programming you need to make sure the radio is set to low power and to use narrow band.  Most people with these radios don’t understand this and cause interference on adjacent channels.

Ham radio

If you are a Licensed Ham radio operator, you can use almost any radio regardless of type acceptance because your license only covers you, the control operator.  This is because an amateur radio operator is expected to develop new technologies in addition to participating in emergency response, international relations …etc.

Common Inexpensive radio models

Dual band models
  • UV5R (and variants)
  • BF-F8,GT-3 (and variants)
  • UV82
70CM only (usually 1-3 watts)
  • GT-1 (and variants)
  • BF-888
  • ATR-22 (Amcrest)

Re-branded by : Retevis, Pofung, Baofeng …

Key features

  • Dual receive (…kind of)
  • Dual band (a vast majority use 2m and 70cm)
  • GT and newer variants have up to 8 watts, otherwise 4 watts or lower.
  • Dirt cheap (less than 50$us)
  • Dirt cheap accessories
  • Buy in bulk (package deals with accessories for ~35$ per unit)

Key problems

  • High out-of-the-box failure rate
  • Flimsy connectors on earlier models
  • accessories are usually by not always cross-compatible
  • Squelch and filter interference issues on earlier models
  • No memory storage from key pad (programming cable only)
  • Limited VFO operation on some models.
  • Not all models are FCC type accepted so they are only usable for ham radio.


So Quantity over quality, I own one of these radios to hand to hams who forgot to bring their radios to events or deployments.  If they break I tend not to worry very much.  If you have to traipse though hell and you depend on your radio to work while wading through the bayou, the baofeng or anything else listed here isn’t the radio for you.  Spend some extra money on something that is reliable and rated to resist the elements.  Also, if you intend to use this radio something it is not certified to do, then please be doubly sure to use the right settings (ex. low power and narrow band).


FCC considers reform of Part 95 rules for personal radio services

In June 2010, the FCC proposed sweeping changes to personal radio services, including the GMRS. WT Docket No. 10-119 included proposals such as lowering power limits of GMRS radios to 2 watts, changing the allowance for GMRS repeaters and, most notably, eliminating the license requirement for GMRS and license by rule. Now, after 7 long years, the FCC has finally moved to consider a ruling on these proposed changes, and more. The ruling didn’t limit these changes to the GMRS, but affected FRS, CB, MURS, and other personal radio services. In effect, the FCC isn’t merely wanting to change Part 95 rules, they are planning to reform them.

This Report and Order is a major re-write of the Part 95 Rules. It was apparently reorganized to make it more consistent and easier to read, and eliminating “Q&A” style structuring of some rules in the document. According to the FCC, the rules are being overhauled “to modernize them, remove outdated requirements, and reorganize them to make it easier to find information.” In re-writing the rules, the commission hopes to make them “consistent, clear and concise”.

Whether or not the FCC actually achieves this objective remains to be seen. The new Part 95 is still a long read, and at 114 pages, the full Report and Order, which includes the new Part 95 rules, is even longer. However, the changes are significant. For users of FRS, GMRS, and CB radios, here is a summary of key changes to those services.

Family Radio Service (FRS)
FRS would now have 22 channels. All 22 channels that today’s combination FRS/GMRS radios use will become part of FRS. All FRS channels are also allotted to the GMRS channels on a shared basis.

FRS would now have higher wattage. Previously, FRS was limited to one-half of one watt. The new rules allow FRS radios to transmit at up to 2 watts of power. According to the FCC’s new rules, “Each FRS transmitter type must be designed such that the effective radiated power (ERP) on channels 8 through 14 does not exceed 0.5 Watts and the ERP on channels 1 through 7 and 15 through 22 does not exceed 2.0 Watts.”

FRS radios may transmit digital data Previously, FRS transmissions were limited to voice conversations. Now, these units may also transmit and receive digital data as well. This includes location information or brief text messages to and from other FRS or GMRS stations. The FCC states ” Digital data transmissions must be initiated by a manual action of the operator, except that a FRS unit receiving an interrogation request may automatically respond with its location.”

FRS will be allowed to be combined with Part 15 devices. This would permit combination with technologies such as Wi-Fi and Bluetooth.

FRS license by rule is still the rule, but different. Many current combination FRS/GMRS handheld two way radios will be reclassified as FRS and not require an individual license to operate on any of 22 the channels. In effect, if the currently classified FRS/GMRS radio transmits below 2 watts, it’s officially an FRS radio and doesn’t require a license to operate. Both individuals and businesses now seem to explicitly authorized for use on the FRS.

General Mobile Radio Service (GMRS)
GMRS would have 30 channels. The GMRS is allotted 30 total channels consisting of 16 main channels and 14 interstitial channels. The GMRS operators may use their GMRS station for two-way plain language voice communications with other GMRS stations and with FRS units for personal or business activities.

GMRS can still be used with repeaters. The rules allow for use of GMRS with repeaters on specified channels. GMRS repeater, base and fixed stations may be operated by remote control.

GMRS radios may transmit digital data. As with FRS, digital location information, requests for location information, and brief text messages to another specific unit is now allowed to be transmitted over GMRS. Previously this was allowed to Garmin through a special waiver.

GMRS still requires a license but for a longer term. Previously, a GMRS license was valid for 5 years. Licenses are now valid for 10 years. As for current FRS/GMRS radios, If it transmits above 2 watts, it’s a GMRS radio and needs a license. Current repeater capable FRS/GMRS radios will be classified as GMRS and require a license. A license is still issued for use by individuals and their immediate families. Immediate family members are the licensee’s spouse, children, grandchildren, stepchildren, parents, grandparents, stepparents, brothers, sisters, aunts, uncles, nieces, nephews and in-laws. Non-individuals are grandfathered in.

Citizen’s Band Radio Service (CBRS)
“Citizens Band Radio Service” would be officially named “CB Radio Service”. Cordless microphones are allowed on CB. The restriction of long-range communications for CB has been eliminated, however the power limit was not increased. The CB serial number no longer required to be engraved into the transmitter chassis. Manufacturers are no longer required to include the FCC rules with CB radios.

Other notable changes affecting all of these services

  • Voice obscuring features would be prohibited across the entire PRS.
  • Continued use of existing radios that include scrambling features are not prohibited.
  • 18 months after adoption, no person shall be permitted to manufacture, import, sell, or offer for sale any equipment that incorporates voice scrambling or obscuring for any of the PRS regardless of previous certification.
  • Radios combining multiple services will no longer be approved. This includes FRS and GMRS (although GMRS is compatible with FRS).

Note: The reform is under tentative consideration by the FCC at its open meeting scheduled for May 18, 2017. From the FCC: “The issues… and the Commission’s ultimate resolution of those issues remain under consideration and subject to change. This document does not constitute any official action by the Commission.”

FCC Personal Radio Service Revisions Will Affect GMRS, FRS, CB, Other Part 95 Devices

In a lengthy Report and Order (R&O) in a proceeding (WT Docket No. 10-119) dating back 7 years, the FCC has announced rule changes affecting the General Mobile Radio Service (GMRS), the Family Radio Service (FRS), the Citizens Band Radio Service (CBRS or “CB”), as well as other applications that fall under the FCC’s Part 95 Personal Radio Services (PRS) rules and regulations. Part 95 devices typically are low-power units that communicate over shared spectrum and, with some exceptions, do not require an individual user license from the FCC. As the R&O explains, common examples of PRS devices include “walkie-talkies;” radio-control cars, boats, and planes; hearing assistance devices; CB radios; medical implant devices; and Personal Locator Beacons.

“This draft Report and Order completes a thorough review of the PRS rules in order to modernize them, remove outdated requirements, and reorganize them to make it easier to find information,” the FCC said in a summary attached to the R&O. “As a result of this effort, the rules will become consistent, clear, and concise.”

GMRS and FRS devices are used for personal communication over several miles; compact FRS handhelds, often sold in pairs, are widely available. While GMRS and FRS share spectrum, GMRS provides for greater communications range and requires an FCC license; FRS does not.

“The rules will increase the number of communications channels for both GMRS and FRS, expand digital capabilities to GMRS (currently allowed for FRS), and increase the power/range for certain FRS channels to meet consumer demands for longer range communications (while maintaining higher power capabilities for licensed GMRS),” the FCC explained.

The amended rules eventually will eliminate combination FRS/GMRS radios for the most part, but allow up to 2 W PEP output for FRS transceivers. “[M]any current users of GMRS/FRS combination radios do not obtain licenses to operate over the GMRS frequencies in those radios,” the FCC said. “Much of this problem likely arises as a result of the mass consumer marketing of combination devices for sale to the public in large quantities to users who do not know about or do not understand the licensing requirements attached to such radios and obligations associated with operating in the GMRS.”

The FCC said it no longer will certify FRS devices that incorporate GMRS capabilities or capabilities of other services. Existing GMRS/FRS combination radios that operate at power levels of less than 2 W ERP will be reclassified as FRS devices; existing GMRS/FRS radios that operate above that power level will be reclassified as GMRS devices, requiring an individual license. Radios that can transmit on GMRS repeater input channels will continue to be licensed individually and not by rule.

“We believe the 2 W limit for FRS is appropriate, because many of the existing combination GMRS/FRS radios already operate under that level with no significant complaints about interference or other problems, and it provides a reasonable balance between the desire for increased range over the prior FRS power levels and battery life,” the FCC said.

The FCC said changes to the decades-old Citizens Band (CB) rules will remove outdated requirements, including certain labeling requirements. DXing on Citizens Band will become legal too. Once the new rules are effective, CBers will be allowed to contact stations outside of the FCC-imposed — but widely disregarded — 155.3-mile distance limit. The revised CB rules further clarify how hands-free devices can be used with CB radios and will allow the use of wireless microphones with CB radios. “We find the record persuasive regarding the consumer demand for this feature, and it will promote safety on the highways by reducing driver distraction for those using CB [radios],” the FCC said. The FCC left in place the current power limits for the CB Radio Service.

The rule changes will phase out the use of voice-scrambling or “obscuring” features in all Part 95 devices, and it will ultimately prohibit manufacture, importation, or sale of any devices incorporating such features, “regardless of whether the Commission has previously certified that radio.”

Overall, the FCC said, its action “achieves a thorough review of Part 95 rules and creates a new rule structure where common administrative rules are consolidated to reduce duplication, and individual subparts are structured with a common numbering scheme.” The FCC said the changes remove “outdated and unnecessary rules, while clarifying others.”

Most of the new Part 95 rules will become effective 30 days after their publication in The Federal Register.

Amateur Radio Q-Codes

The Q-Code is a standardised collection of three-letter message encoding, also known as a Brevity Code, (Brevity Codes are used in amateur radio, maritime, aviation and military communications. The codes are designed to convey complex information with a few words or codes, all of which start with the letter “Q”), initially developed for commercial radiotelegraph communication, and later adopted by other radio services, especially amateur radio. Although QCodes were created when radio used Morse Code exclusively, they continued to be employed after the introduction of voice transmissions. To avoid confusion, transmitter call signs are restricted; while an embedded three-letter Q sequence may occur (for instance when requested by an amateur radio station dedicated to low-power operation), no country is ever issued an ITU prefix starting with “Q”, (The International Telecommunication Union [ITU] allocates call sign prefixes for radio and television stations of all types). The codes in the range QAA–QNZ are reserved for aeronautical use; QOA–QQZ for maritime use and QRA–QUZ for all services.

Early Developments

The original Q-Codes were created, about 1909, by the British government as a “list of abbreviations… prepared for the use of British ships and coast stations licensed by the Postmaster General. The Q-Codes facilitated communication between maritime radio operators speaking different languages, so they were soon adopted internationally. A total of forty-five Q-Codes appeared in the “List of Abbreviations to be used in Radio Communications”, which was included in the Service Regulations affixed to the Third International Radiotelegraph Convention in London (The Convention was signed on July 5, 1912, and became effective July 1, 1913.)

Later Usage

Over the years, modifications were made to the original Q-Codes to reflect changes in radio practice. Over a hundred Q-Codes were listed in the Post Office Handbook for Radio Operators in the 1970s and cover subjects such as meteorology, radio direction finding, radio procedures, search and rescue, and so on.

Some Q-Codes are also used in aviation and some in maritime. (A subset of Q-Codes is used by the Miami-Dade County, Florida local government for law enforcement and fire rescue communications, one of the few instances where Q-codes are used in ground voice communication.) Many military and other organizations that use Morse Code have adopted additional codes, including the Z-Code used by most European and NATO countries. Used in their formal “question/answer” sense, the meaning of a Q-code varies depending on whether or not the individual Q-code is sent as a question or an answer. For example, the message “QRP?” means “Shall I decrease transmitter power?”, and a reply of “QRP” means “Yes, decrease your transmitter power”. This structured use of Q-codes is fairly rare and now mainly limited to amateur radio and military Morse Code (CW) traffic networks.

Breakdown by Service •

QAA to QNZ – Assigned by the International Civil Aviation Organization (ICAO). •
QOA to QQZ – Reserved for the Maritime Services.
QRA to QUZ – Assigned by the International Telecommunications Union (ITU). •
QVA–QZZ – Are not allocated.

Amateur Radio

Selected Q-Codes were soon adopted by Amateur Radio Operators. In December, 1915, the American Radio Relay League (ARRL) began publication of a magazine titled “OST”, named after the Q-Code for “General call to all stations”. In Amateur Radio, the Q-Codes were originally used in Morse Code transmissions to shorten lengthy phrases and were followed by a Morse Code question mark (··–··) if the phrase was a question.

Q-Codes are commonly used in voice communications as shorthand nouns, verbs, and adjectives making up phrases. For example, an Amateur Radio Operator will complain about QRM (manmade interference), or tell another operator that there is “QSB on the signal”; “to QSY” is to change your operating frequency.

They can still be heard on HF communications but are not normally used on UHF and VHF communications. The reason is quite simple. Many radio amateurs have become certified purely to be volunteer communicators for their local emergency programs and consequently are not very familiar with the Q-Codes. Recently Q-Codes have again been used more for Morse Code communications than for voice communications.


Australia LTE frequency bands

Frequency bands and channel bandwidths

From Tables 5.5-1 “E-UTRA Operating Bands” and 5.6.1-1 “E-UTRA Channel Bandwidth” of 3GPP TS 36.101, the following table lists the specified frequency bands of LTE and the channel bandwidths each listed band supports:



Common name Included in
(subset of)
Uplink (UL)
BS receive
UE transmit (MHz)
Downlink (DL)
BS transmit
UE receive (MHz)
1 FDD 2100 IMT 65 1920 – 1980 2110 – 2170 190 5, 10, 15, 20
3 FDD 1800 DCS 1710 – 1785 1805 – 1880 95 1.4, 3, 5, 10, 15, 20
5 FDD 850 CLR 26 824 – 849 869 – 894 45 1.4, 3, 5, 10
7 FDD 2600 IMT-E 2500 – 2570 2620 – 2690 120 5, 10, 15, 20
28 FDD 700 APT 703 – 748 758 – 803 55 3, 5, 10, 15, 20\

ETSI TS 136.101 V13.3.0 (2016-05) – LTE; Evolved Universal Terrestrial Radio Access (E-UTRA); User Equipment (UE) radio transmission and reception (3GPP TS 36.101 version 13.3.0 Release 13)

ETSI TS 136 101 V14.3.0 (2017-04) – LTE; Evolved Universal Terrestrial Radio Access (E-UTRA); User Equipment (UE) radio transmission and reception (3GPP TS 36.101 version 14.3.0 Release 14)

Orange Pi PC 2 H5 Quad-core 64bit

The marketplace has been flooded with Raspberry Pi for a while now, most are massively expensive and the “$35” Raspberry Pi, well actually it’s about $50 landed in Australia.. For a true $35AU single board computer you should check out the Orange Pi range of single board computers.  These little baby’s give the Raspberry Pi a run for it’s money and are well worth a look. This article, I’ll focus on the orange Pi PC 2.. It’s an open-source single-board computer.  It can run Android 4.4, Ubuntu, Debian, Raspberry Pi Images.

If your interested in playing with (or you have a serious project), they are available on BANGGOOD. At the time of writing they are $33.52AU delivered.

For this price point it has everything including 40 Pins Header,compatible with Raspberry Pi B+. Three USB2 ports, a 100/1G Ethernet port, although good luck actually getting giggle bit performance.

A H5 High Performance Quad-core 64-bit Cortex-A53, with an Integrated multimedia acceleration engine, Hardware Java acceleration, Integrated hardware floating-point co-processor and has 1GB DDR3 SDRAM.

The GPU is a High Performance Hexa-core Mali450, providing full scene over-sampled 4X anti-aliasing engine with no additional bandwidth usage, It supports the industry standard OpenGL ES 2.0/1.1/1.0, OpenVG 1.1, EGL, pumping out 40 GFlops, with a pixel fill rate greater than 2.7GPixel/s.

The board supports a TF cards upto 64Gbytes and has onboard NOR flash of 2MB.

It can run Android 4.2, Android4.4, Ubuntu, Debian, Fedora, Raspbian, ArchLinux,openSUSE, OpenWrt, and other OS systems. Checkout the Orange Pi website for further information about this

A CSI input connector Camera, supporting an 8-bit YUV422 CMOS sensor interface,with CCIR656 protocol for NTSC and PAL. Supports the SM pixel camera sensor .Video capture is possible up to 1080p@30fps.

Video Outputs include the standard HDMI with HDCP, CEC, and integrated CVBS. Unlike most simultaneous output of HDMI and CVBS is supported.


Unlike the Pi, the Orange PI has DC input for can power and a power switch. Unfortunatly the USB OTG port doesn’t supply power.

As already mentioned, they are available on BANGGOOD. At the time of writing they are $33.52AU delivered.

Orange Pi™ is a trademark of the Shenzhen Xunlong Software CO., Limited