AB7CQ - General Subjects

New generation multiband multimode rigs typically cover VHF/UHF/HF, these type of rigs have independent mic gain and speech compression controls that the user can adjust independently, older transceivers like a typical mobile rig do not allow you to adjust mic gain or speech compression, it’s all preset in older VHF/UHF mobile rigs.

Quite often operators, especially new Hams will set the mic gain too high and drive up the speech compression, which either causes the audio to clip out of the pass band, or the audio generates mostly low tones with all bass and becomes un-understandable. This can also happen if a mic is too HOT, then one needs to back off the mic, or modify the mic. This problem can be accentuated when going through a repeater.

The use of speech processing (aka speech compression or clipping) has become the major bane of amateur radio, especially mobile operation. It allows every little nuance of engine noise, AC fans, the kids in the back seat, and that squeak in the left quarter panel to be plainly heard. It is important to remember, the average vehicle traveling at 60 mph, is at least 25 dB louder than the average living room, and some are over 40 dB louder.

Most amateurs do not know how to properly set their microphone and/or processing controls, resulting in some really lousy-sounding, on-air signals. They might sound passable when properly tuned in, but a few kHz away the distortion products (IMD Intermodular Distortion) can be clearly heard.

It should be noted at this point, that any form of speech processing does increase the average power level. This fact does cause the signal to appear louder on the receiving end. However, if used excessively, it also removes most of the nuances our brain uses to comprehend what's being said.

Almost without exception, all modern HF transceivers have some form of speech processing built-in (unfortunately!). Speech compression in its simplest form, is nothing more than an automatic level control. The softer nuances of speech are amplified more than the louder ones. In some cases, a different (narrower) bandpass filter is used and/or different DSP settings, and the dynamic nature of the ALC may be changed to minimize IMD. However, over zealous use (excessive gain and compression levels) will defeat any provision to prevent excessive IMD!

Speech processing, however it is done, not only increases the average output power, is also increases the average current draw! Depending on the configuration, it could in fact double! This can easily tax the heartiest of electrical systems, especially when running high power. As the voltage sags, the IMD goes up, and readability decreases even more.

Here is the very best advice you'll ever get with respect to using speech processing and/or excessive microphone gain in a mobile—don't use it!

The problem is that most new hams are excited with their new rig and their focus is on the new toy, they fail to take the time to understand how the transceiver really works and how these features affect the tranceivers overall peformance.

Unfortunately, a lot of this is overlooked in amateur radio classes. Misadjustment of these controls can cause all sorts of negative issues, one of which is generating spurious emissions on the bands, something extremely frowned on by hams, their signals spread over a wider specturm of frequency (called buck shotting), they can even be cited by the FCC for generating spurious transmissions and even fined (issued a forfeiture) for generating spurious emissions.

**********************************

Technical Article #2 - Transceiver Display Developing Lines Or Going Black

Boy have I heard of this problem before, so many complaints about radio transceiver displays going bad and it's going to cost $300 - $500 to repair or replace the display. The complainant always blames the manufacturer for the failure and threatens to never purchase another radio of that brand name again. 99% of the time it's the ham that screwd up. Time and time again they base the failures on the manfacturer's poor design of the equipment.

The world has changed, we used to have analog meters, dials, and knobs on rigs with etched or stamped numbers and letters on the dials and knobs, then came the world of solid state technology with digital LCD displays and digital meters. Those old analog meters, dials, and knobs were pretty much immume to high levels of RFI/EMI, they could care less about reflected RF, power amplfiers, or high VSWR, but LCD digital meters and displays, well, that's an entirely different scenerio.

LCD displays and digital meters don't like reflected RF, and they will be adversely affected by high levels of RFI/EMI. If you owned such a rig, you damn well better install the appropriate shielding, chokes on all those interconnecting cables, power lines, and you better make sure that your equipment isn't producing high levels of redlected RF, eventually, this stuff is going to takle it's toll on your rigs LCD displays, not to mention those expensive RF transistors or modules. In 35 years I never toasted a rig. Say what you will, but I always did what was necessary to keep the SWR levels down to no more than 1.3.1. On HF I used the appropriate tuners when and as necessary.

Another thing, don't leave that expensive solid state transceiver, VHF/UHF or HF rig cooking in your vehicle in temperatures reaching 140 degrees in the summer, the same is true for extremly cold temperatures in the winter months. I guaruntee you, that the majority of you will wind up with LCD failures. Take the rig out of your vehcile if it it going to be subjected to these temperature extremes, save yourself alot of heartache. In 35 years of ham radio, I only lost one rig with a failed LCD display, and that was my own fault, It had been installed in the vechile and stayed there for 8 years, being subjected to the extreme heat of Arizona, sure enough, the display turned to toast, the rest of the rig was still OK, I don't kmow why, but it was. Just about every electronic component had been cooking in there for 8 years, dried to the bone and componet values drastically changed.

The ham gear you use is not military spec, it's not designed for a Vientnam or a Desert Storm environment, or any other highly adverse environment.

********************************

Technical Artical #3 - Antenna P-Static - Precipitation Static and Duplex Radio...

Fiberglass antennas in general suffer from Corona Discharge and Precipitation Static. These phenomena can occur during wind and dusty periods, or when a charged cloud is near, and an aurora can form around the antenna, and if it’s raining at the time, the water droplets will discharge to the radome creating noise.

Dust can be charged and blown against an antenna, especially during windy periods causing static similar to precipitation static. As the static is builds up on the antenna, receiver desensitization will occur. Many times a limiter current meter can be used to observe these phenomena and you will note the current go up. This is common is hot desert climates where airborne dust driven by wind comes into contact with fiberglass antennas.

I have three Comet GP-15 fiberglass antennas; one is used for the 444.600 / 449.600 repeater. The receiver limiter metering point on the repeater receiver will read usually a couple of micro amps (uA) when receiving no signal on a typical day.... then as wind, dust, and clouds come together the limiter stage will go into hard limiting of up to approximately 40 micro amps (uA), especially when a storm cloud comes near.

Obviously a repeater user’s signal would have to be stronger than the noise for the squelch to open, and then the user will most certainly be very noisy even though he may normally be dead full quieting into the repeater.

You will hear the instant the static has dissipated, the user will suddenly become full quieting into the repeater, and then the sequence will start all over again gradually building up and then like a switch, go back to dead full quieting. The instant when the repeater quiets up is when lightning has struck, or when the static has dissipated.

The building up of static will sound like electrical interference. This problem happens with, or without the transmitter being on, but is sometimes worse with the transmitter on.

Static build up from rain, wind, and dust can cause a Corona to build up on a fiberglass antenna causing static and receiver desense to occur. These corona, precipitation, wind, and dust problems can be solved by using a static dissipation device. These devices continually bleed off the static charge.

A great many repeaters owners, myself included, will install these types of devices to continually bleed of static charge, the difference can be like day and night, from being a repeater with limited range to one whose ranges is remarkably extended and full quieting.

This problem is most severe when your antenna is the highest on a structure or tower (i.e. top mounted). Fiberglass antennas suffer more because these types of antennas are grounded.

It has been stated that after installing this type of device, lightning will typically NOT strike this type of antenna because of the lack of ability of the antenna to build a counter charge.

Most repeater owners no little or nothing about P-Static.

What’s most important, is the damage that can be done by P-Static to your radio gear, one day, without warning, you might suddenly notice that your radio is behaving oddly, and only to find that it has been damage more seriously by P-Static.

Remember, P-Static can build up on your antenna and feed line causing damage to your radio gear without the presence of lightning, in hot desert climates, on windy days, with airborne dust (sand and other debris), static can build up on the antenna and travel down the feed line and suddenly discharge into the radio if you haven’t installed the necessary static bleed-off discharge apparatus.

****************************************

Interference To Consumer Electronics - Excerpt From AB4D - Facts Not Fiction

While casually surfing the net, I occasionally run across incorrect information regarding Amateur Radio, especially in relation to interference complaints by consumers, who allege that a ham radio station is interfering with their home entertainment equipment.

These self-appointed experts about interference matters really say some incorrect things. Below are a few examples from a message board that I recently read titled Ham Radio Interference. That thread contains quite a bit of incorrect information...which I will debunk with fact.

"A few years ago the FCC started imposing new restrictions on hams including scanning their emissions for unintended directionality and the like. I believe every ham was required to scan the area for their particular modes of operation."

The FCC has never imposed broad restrictions on ham radio operators, beyond the rules and regulations published in Part 97. Unless there has been some level of enforcement action, operating restrictions are rarely imposed. The rules state, the FCC can impose quiet hours on hams (47 CFR 97.121). However, in my experience, I have never heard of anyone being restricted by the FCC for causing interference to their neighbor's TV set or Stereo. Long ago the FCC realized, 99.9% of interference to home entertainment equipment is usually caused by the poorly designed receiving equipment being sold in the U.S. from China and Southeast Asia. Even well known name brand products from companies based in Japan, many times do not have adequate shielding and filtering.

To maximize profits, manufacturers of home entertainment products take a chance to save a few dollars on each unit by not properly shielding and filtering that equipment. They count on the fact, that most of the equipment will never be co-located near an RF transmitter. Combining that equipment with the poor installation usually performed by most consumers, it's a recipe for interference. When consumers use cheap poorly shielded wires from the local big box stores or Wal-Mart, to interconnect that equipment, and then leave a rats nest of wire behind the TV or Stereo, they've also built themselves a great antenna to increase their vulnerability for interference.

Not withstanding that posters comments, the FCC does not randomly scan ham radio emissions for "unintended directionality". I don't even know what that term implies. The expectation from the FCC is we self-police our own. If a station is out of compliance, and is experiencing technical issues, that condition is usually immediately noticed by other hams. The offending station is usually informed there is an issue that requires their attention.

Another post in that thread reads...

"It is not legal for a ham operator to interfere with his neighbors' electronic devices. There are laws to protect the citizens from invasive radio frequencies."

There are no federal laws that "protect the citizen from invasive radio frequencies." There are no laws against something that does not exist. There is no such thing as an "invasive radio frequency." I believe the poster was trying to say "invasive radio frequency signals" a fact of life in our modern society. We are all subjected to it, and our bodies are invaded by it each day without our consent. Radio frequency energy is used by our cars, cell phones, broadcast radio and TV transmitters, radar systems for aircraft and weather, public service communications fire/police, home entertainment devices, even using an IPod/IPad or computer subjects us to small amounts of RF energy at various frequencies, it's everywhere.

There are some state and local nuisance laws in the U.S. that various localities try to enforce. However, those laws are only applicable to interference caused by non-licensed stations, such as CB radio operators using illegal non-type excepted equipment and high power external amplifiers. Since amateur radio is a licensed service regulated by the FCC, local and state law enforcement has no jurisdiction over the operation of a amateur radio station. The courts have repeatedly stated, the FCC has sole jurisdiction in the United States over all matters relating to any station licensed under the radio services regulated by the FCC.

In closing, one poster actually provided factual information....

"More than likely the fault is due to lack of/or inadequate filtering inside the TV or a break in the cable system. FCC Part 15 specifically states that the TV user must accept any unintentional interference from transmitters operating within specification. Check your user's manual."

That is a true statement. 47 CFR 15.5b, states that "Operation of an intentional, unintentional, or incidental radiator is subject to the conditions that no harmful interference is caused and that interference must be accepted that may be caused by the operation of an authorized radio station, by another intentional or unintentional radiator, by industrial, scientific and medical (ISM) equipment, or by an incidental radiator." In laymen terms, if you own and operate any device that is regulated under Part 15 of the Commission's rules (which most home electronic entertainment devices full under those rules), it must accept any interference that may be caused by the operation of an authorized radio station (i.e. a licensed amateur radio station; emphasis added), and may not cause interference to any licensed radio station.

When the marketplace became flooded in the 1980's with cheap electronics and home entertainment devices, the FCC revised Part 15 (54 FR 17714, Apr. 25, 1989, as amended at 75 FR 63031, Oct. 13, 2010), to state that Part 15 devices must accept interference from licensed stations FCC Part 15.

If you are a consumer, and are experiencing Radio Frequency Interference, do not jump to the conclusion that the source of the interference is from "that ham down the street." Interference that affects the operation of a device can come from many sources, sometimes even within your own home. Do not demand that he or she cease all operation. It is an unreasonable request, and can set a tone for non-cooperation. Unless the station is being operated not in accordance with good engineering and good amateur practice as determined by the FCC, amateur radio operators are under no obligation to help you solve the interference condition you are experiencing. Rather, if you suspect an amateur radio station is interfering with your equipment, politely tell him or her what you are experiencing and ask if they can help. Most amateur radio operators will be happy to help you track down the source of the interference, even if they are the source. Many times they can provide the technical assistance needed to help you correct the situation.

*******************************

Bob Krueger, AB7CQ

Web Administrator

146.920/146.320 PL 123.0

444.600 / 449.600 PL 100 Repeater

IRLP Node: 7515 PL 114.8

ab7cqradio@ebidpal.com