This video covers the equipment and steps to use the HRI and PDN modes in the DIRECT and ACCESS POINT types of operation.
IMPORTANT: Effective and safe station grounding is a complex and often controversial subject. This video is not intended to be a how-to guide for safe and/or effective grounding. It is recommended that you seek qualified advice and instruction for your specific station and environment
Mike Aimone, WA8AHZ introduces the topic of Electrical Safety, Grounding and Bonding that every amateur radio hobbyist should be aware of.
TelescopeMan does a show and tell on his amateur radio station grounding system. Ideally the ground rod would also be connected to the main electrical ground, but in this case the electric ground is on the opposite side of the house and also blocked by a concrete patio sidewalk and driveway. If you can also ground the rod to the main electrical ground this is best practice. However the system shown would bleed-off static charges that accumulate on outside wires and antennas during wind, snow, and rain events. Additionally the long wire ground acts as a counterpoise for the 127ft end fed antenna, along with the 50ft of coax running from the antenna box to the line isolator shown in the video. I still disconnect my equipment coax and unplug from the wall when a lightning storm is imminent. Since installing this grounding system RFI has been eliminated from inside the shack.
Ask Dave Episode looks at the amateur radio high frequency (HF) bands and describes each. This helps hams new to HF to understand what bands will work best for them.
If you are considering trying out one of the digital voice modes but don't know where to start, WATCH THIS VIDEO before you buy one. We're going to discuss DMR, D-Star and (C4FM) Fusion modes. Which one is best, and which one is best for you. I'm going to dispel the age old myth of sound quality between the three, look at the radio designs, talk about price. This is what you need to know getting started on your journey into digital voice radio.
You may have heard the term spread spectrum (try saying it three times really fast), or frequency hopping, but perhaps you do not have a solid grasp of what’s going on with these emission types. Let’s take a closer look while addressing some of the various question item concepts in the Extra Class pool about this mode.
The general concept of spread spectrum is to spread the RF signal across a broad range of the frequency domain. As an example comparison, a typical SSB signal is “spread” across a relatively narrow 3 kHz of bandwidth, while an amateur mesh network using spread spectrum in the 2.4 GHz band may spread its signal across more than 80 MHz of bandwidth. (A 27,000 to 1 ratio!) Generally with spread spectrum, the carrier frequency of the transmitted signal will continuously change over time, dragging the signal bandwidth with it all across the breadth of the amateur band from moment to moment.
Why bother? What’s the advantage of spread spectrum?
Because of the unique methods used to spread the signal across broad bandwidth, such as frequency hopping that will be described below, spread spectrum is resistant to interference, both intentional or unintentional. Signals not using the spread spectrum algorithm for carrier frequency changes across the broad bandwidth are suppressed in the receiver. A spread spectrum signal can effectively overlay in a band with other signals, expanding the utility of the band. Because many spread spectrum techniques employ code division multiplexing, some privacy of communications can be had through pseudo-random sequencing, but the transmissions must not be used to obscure the meaning of communications. Further, due to the wide bandwidth used by spread spectrum signals, transmissions are permitted only on amateur frequencies above 222 MHz, and the transmitting station must be in an FCC regulated area or other country that permits spread spectrum emissions.
Frequency Hopping: There are multiple methods of spreading signals, but our question relates to just the method of frequency hopping. The carrier frequency of a frequency hopping spread spectrum system changes rapidly (hops) from one frequency value to another over time. The specific frequency change sequences are determined by a pseudo-random code used by both the transmitting and receiving stations in coordination with one another. That is, each station uses the same code sequence to shift their tuning among the carrier frequency hops in perfect union. You may think of this coded sequence as identifying numerous individual channels across the breadth of an amateur band, and the carrier frequency randomly bouncing from channel to channel over time in quick hops. The dwell time on any single channel is usually on the order of 100 ms, or about one-tenth second. While the instantaneous power of the spread spectrum signal may be relatively high, the average power over time on any singular frequency in the amateur band will be very low.
Other methods of spread spectrum sweep the carrier frequency up or down the amateur band with specified timing and shift the phase of the carrier, and yet others use a repeating sequence rather than a continuing pseudo-randomized algorithm. A pulsed RF carrier can also be used to affect time multiplexed signals, often combined with frequency hopping in a hybrid technique of spread spectrum. You may wish to research Direct Sequencing, Time Hopping, and Pulsed FM Chirp spread spectrum systems.
Wifi Protocols: Many Part 15 computer devices utilize frequency hopping spread spectrum. Bluetooth devices utilize frequency hopping, and many computer network wifi standards implement some type of spread spectrum technique. For instance, the 802.11b wifi protocol takes advantage of spread spectrum, although later versions such as 802.11n use modern multiplexing schemes rather than true spread spectrum techniques.
The unique characteristic of an NVIS antenna is embodied in the full name: Near Vertical Incidence Skywave (NVIS) antenna. An NVIS antenna will direct the strongest portion of its radiated signals in a “near vertical” or upward direction. As a result, the signal’s angle of incidence with the ionosphere is a steep one, hence “near vertical incidence.”
In contrast, other typical antennas for DX or long distance contacts tend to be arranged so that the greatest portion of the radiated signal is directed low to the ground, heading toward the horizon. The low angles of propagation of the DX antenna provide the greatest skip distances. The angle of incidence with the ionosphere is shallow, and signals are refracted back toward the earth in similarly shallow angles, resulting in great skip distances. However, stations in the skip zone – the area “under the skip” of this propagation technique – usually cannot be contacted.
The NVIS antenna is not intended for long distance communications. The near vertical signals of the NVIS antenna are refracted back toward the earth in similarly steep angles, resulting in shorter skip distances. This is the advantage of the NVIS antenna, and it reveals the correct response option for this question – the high vertical angle radiation provides communications within a radius of a few hundred kilometers. An NVIS antenna can reach stations that would be in the skip zone of distantly propagating antennas.
The 40-meter, 60-meter, and 80-meter bands tend to work best for NVIS propagation, even during the daytime. These lower HF frequencies are very effectively refracted by the ionosphere, providing the short skip with the small angles involved. Higher HF will usually not be refracted sufficiently to affect good NVIS propagation.
But you may question the daytime performance due to that pesky D-layer of the ionosphere that is known for its daytime absorption of low frequency HF in these bands! In typical daytime operation the 40-meter and lower bands are considered poor skip bands because the D-layer attenuates these signals severely, and only once the D-layer dissipates at night do these bands open for long distance propagation. However, with the steep propagation angles with NVIS, the transit distance through the D-layer is minimized, and the attenuation is much less than with low-angle propagation. As a result, NVIS communications tend to work even in daylight hours on these low bands, given sufficient activation of the higher ionosphere layers.
An NVIS antenna is a horizontally polarized antenna, such as a horizontal wire dipole, positioned above the ground less than ¼ wavelength high. Heights of 1/8 to ¼ wave tend to provide good performance, although some operators prefer heights as low as 1/10 wavelength. For the 40-meter band that is only 4 meters above the ground, or roughly 13 feet.
The bandwidth of CW signals is narrow, usually close to 150 Hz and dependent largely upon the rise and fall time of your transmitter’s keying. In spite of this narrow bandwidth, it is important to avoid consuming more of the band than necessary to be courteous to others seeking to use the band. Cutting right to the chase, zero beat means perfectly matching your CW transmit frequency to that of the desired received signal, thereby minimizing the bandwidth consumed by the two –way QSO.
Most modern radios provide a CW sidetone generator. This is an audible tone of the signal you transmit. Hearing your own dits and dahs makes sending consistently timed, accurate code easier. Good amateur practice calls for you to tune the receiver so that the received tone of the other station perfectly matches your own sidetone. In this way the frequency on which you and your contact are transmitting in alternation is exactly the same. If you are slightly off-frequency relative to your contact the total consumed bandwidth of the QSO will be wider than necessary, reducing the availability of band for other stations to use.
Some modern transceivers provide automated zero beat functions to help precisely align tuning. This can be very helpful in the case where the transmitted tone from the contact station is a higher or lower frequency than your own preferred CW sidetone frequency. A commonly used frequency for transmitted CW tone is 800 Hz, and this is usually the sidetone used to achieve zero beat. This may not be your preferred listening for decoding tone, however!
Many operators prefer to use the receiver incremental tuning (RIT) or receiver clarifier function to tune the receiver slightly higher or lower than the zero beat frequency, thereby changing the demodulated tone of the received station to a more preferred listening tone without altering the transmit frequency. If you prefer to alter the zero beat tone of your contact, use the RIT / clarifier function so that both your station and the contact station can accurately maintain the zero beat transmit frequency, keeping the consumed bandwidth to a minimum.
SSB Receive Filter
A radio receiver is really quite a marvelous device, and we operators ask quite a lot of our receivers. Our environment is awash in radio frequency emissions, some being noise and some intentional transmissions carrying information by various modulation methods such as FM, AM, SSB, CW, or others. The task we expect from our receivers is to be able to cut through the RF cacophony and detect just the singular signal that we desire to hear. It is pretty much analogous to finding the proverbial needle in the haystack.
The ability of a receiver to discriminate between multiple signals is its selectivity. That is, a receiver selects one signal in the band among other signals of frequencies immediately adjacent in the band. The receiver filter bandwidth is a primary factor in determining the receiver selectivity. The receive filter bandwidth determines the range of frequencies that will be allowed to pass on through the demodulation sequence and ultimately drive an audio signal to be heard.
Let’s review a couple of basic concepts about RF signals and then we’ll dive into the heart of this question. First, any RF signal uses a range of frequencies, usually a contiguous range. For instance, the single sideband signal typically uses about 3000 Hz (3 kHz) of frequency range, or bandwidth. With a SSB phone transmission, the 3 kHz of RF bandwidth carries the information of voice audio signals to be received and transformed back into sound by a receiver
The carrier frequency, that value that shows up on your receiver display when you tune, is just a sort of reference point that tells the receiver where to find this 3 kHz band of signals that you wish to demodulate into audio. With SSB, no signal is actually transmitted exactly on the carrier frequency value, but the receiver knows to look across a band 3 kHz higher (upper sideband) or lower (lower sideband) in frequency than the tuned carrier value to find the RF band to receive.
Imagine how the receive spectrum would appear if another SSB signal began to partially interpose itself in the selected receive band. In this image, the signal band represented in blue overlaps with the higher frequency end of the signal band that you actually wish to receive (represented in black). This situation will cause interference in your receive audio, as the lower frequencies of the interfering signal (blue) will be demodulated by the receiver along with the desired band’s higher end frequencies (black). The result is that your receive audio will contain noise that, at least in part, masks the desired audio signal you wish to hear.
Now enters the concept of selectivity and the mighty receive filter bandwidth to save the day! You can select a filter that is somewhat narrower in bandwidth than the desired signal bandwidth and position it to cut out that higher end interference from the blue signal. The red dashed line illustrates the “passed band” by the receive filter, and note how it will attenuate the power of the interfering blue signals. That pesky interfering noise in your audio fades into near nothing!
“But,” you now ask, “aren’t my desired signal frequencies also being attenuated by this filter?” Yes, necessarily in this scenario the higher end of the desired receive signal is also attenuated, but plenty of bandwidth is still available to produce an intelligible audio signal. The quality of the audio may be slightly reduced, but the even more quality-killing noise has been eliminated, allowing you to understand the now-slightly-narrower desired signal’s audio.
So, if you have a SSB receiver with multiple receive bandwidth choices, you have an advantage by selecting a bandwidth that matches the bandwidth of the mode (SSB in this case) and that optimizes the ratio of desired signal to undesired noise or interference. With SSB you will maintain a clearly intelligible audio signal with about 2400 Hz, or 2.4 kHz, of bandwidth. This is a good bandwidth match for SSB reception that will help filter out immediately adjacent or slightly interfering signals on the band.
ARDF - Amateur Radio Direction Finding - is the European style on-foot version of Fox Hunting. This program, from the ARVN vault, is the 2006 USA ARDF Championship that qualified hams for the world ARDF event that year. Don't worry about "2006," this isn't all about results. It's about the people, the techniques and the equipment involved in this fascinating aspect of ham radio.
Everyone wants to know how their signal sounds on the air and often the best way to find out is a signal report from other ham radio operators. The standard signal reporting method for amateur radio is the RST (Readability-Signal Strength-Tone) system
The best signal report for CW operation is RST 599. On phone, we drop the reading for Tone and just give RS reports, so a perfect signal on phone is RS 59 or just “five nine.” On the HF bands, you’ll typically hear something like this: “your signal report is five nine in central Kansas.” If you are good copy, you will usually get a “Five” for Readability. The Signal Strength usually reflects what the operator is seeing on the S-Meter of his receiver. Of course, with both CW and SSB, the S-Meter will be bouncing around a bit, so some interpretation is required. More importantly, there is considerable variation in S-Meter calibration, so signal reports can vary from radio to radio. (S9 is commonly defined as 50 µV at the receiver input, with each S unit representing a 6 dB change in signal strength.) A 55 or 57 report indicates that the signal is very readable but the signal strength is not as strong as a 59 signal.
Most S Meters show an extended scale above S9 that is listed in terms of decibels. The scale may be marked with +10 dB, +20 dB, etc. indicating that the signal strength is that much stronger than S9. You’ll hear radio amateurs say something like “you are 5 9 plus 20 dB.” Or they may just say “you are 20 dB over.”
It is common for DX and contest stations to give out “rubber stamp” signal reports. Basically, they are trying to work as many stations as fast as possible and don’t want to be bothered with accurate signal reports, so everyone gets a 59 or 599 report. CW operators may extend this further by substituting the letter N for 9, sending the report 5NN. (In Morse Code, N is a much shorter character than 9.) In fact, there is a collection of “cut numbers” that CW contesters often use to shorten things up: 0 is replaced by T, 5 is replaced by E, etc. An RST 599 report might be sent as ENN.
On VHF FM, signal reports are often given in terms of FM quieting. A strong FM signal is said to “quiet the receiver” since there is virtually no noise present in the received audio. As the signal strength is decreased, noise starts to appear on the received signal. At some signal level, the noise increases dramatically and the signal becomes unreadable. This dramatic increase is called the threshold effect, meaning that FM signals do not gradually fade out, they suddenly crash into the noise. The key idea here is that you want your signal to be strong enough to be above this noise threshold. In terms of a signal report, a strong signal may result in a “full quieting” report. If the signal is less than full quieting, you may hear a report like “90 percent quieting” or “you have about 10% noise”, which both describe the amount of noise present in the signal. If the signal is really noisy, the report might be “50% quieting.”
You will also hear the classic Five Nine signal report on FM, which is basically saying “excellent signal.” While S Meters are often inconsistent on CW/SSB transceivers, they are almost universally poor on FM rigs. Most FM radios just give you an unlabeled bar graph that is only a relative indicator of signal strength. Usually, these are not labeled in terms of S units, so don’t try to interpret them as such. If all of the bars are lit up on your meter, then you might give a report of “your signal is full scale.”
For FM repeater operation, keep in mind that the signal you are receiving is coming from the repeater and not from the other station. So if the other radio ham is fiddling around with his antenna and asking for signal reports, the repeater signal strength is going to remain the same. You may notice that the other station’s signal into the repeater gets more or less noisy, so giving a report on how well he is hitting the repeater is helpful. “Joe, you are full quieting into the repeater.” This is another reason why FM signal reports tend to be in terms of receiver quieting…in linked systems, the signal strength at the transceiver is less important.
One final note is that sometimes the operator on the other end is looking for a more critical evaluation of his signal quality. If he says something about “checking out this new microphone” or “have been working on solving an audio problem”, that may be the clue to spend a little extra time really listening to the signal and providing more comments on how it sounds. For most of us, we don’t actually get to hear our own signal on the air, so it’s very helpful to get quality feedback from other radio amateurs.