Antennas for Summits

An adequate antenna is a requirement for a successful activation. In this month’s column we’ll look at some popular options for SOTA antennas.


  • Lightweight - You’ll have to carry it to the summit.
  • Rapid deploy - You’ll not have time to wait for concrete to cure!
  • Adequate signal - You need to reach 4+ chasers.

Down in the flatlands, you want a really good antenna and you can afford to put a lot of effort into achieving optimum signal. When you’re on a mountain, there’s a different set of trade-offs. There may be a limited weather window or darkness may be closing in and a rapid deploy can make the difference between a successful activation and a scrub.


If you set off with a 5 watt HT and a rubber duck, you’ll need chasers nearby. Most of the time, you’ll need something better.

You don’t need a 7-element Yagi-Uda atop a 30’ mast for a SOTA activation, although that is certainly an option if you have one and can carry it. A quarter-wave whip will make some contacts. It can be improved with the addition of a “tiger tail.” A tiger tail is just a 1/4 length of light, insulated wire with a ring terminal on the end. You put it over the antenna connector on your HT, screw on the antenna, and you convert your 1/4 wave antenna into a vertical dipole. I work contacts at 100+ miles with 5 watts using one of these. A roll-up slim jim is another popular option.

Line of sight is much, much better from the top of a summit than around town. A rubber duck will work just fine to reach metro Atlanta from Stone Mountain or Kennesaw Mountain. With a quarter wave vertical dipole, you can reach Atlanta from many summits in north Georgia. (Be sure to line up some local chasers in advance, and don’t forget that only simplex contacts count.)


Due to the light weight, most SOTA activators use wire antennas. You can hang your wire vertically from a tree, string your wire horizontally through branches you can reach, or use a lightweight mast. Many activators tie a string to a found rock, throw it over a branch, and hoist up a wire. I’ve got a terrible throwing arm and I like a consistent deploy process, so I carry a carbon fiber mast.

The classic dipole gets good results, and some activators swear by it. This antenna is particularly popular with activators who do not carry an antenna tuner, due to the ability to rig it for low SWR. The most common configuration is an inverted V. If you suspend the center from a mast, you’ll need to carry a mast stiff enough to support it, and that’s generally somewhat heavy. If there are trees on the summit, you can suspend the center and the ends from the trees, but setting up three support points takes longer than I generally like. If the center is up high, you’ll also need to carry a long feed line, which increases your pack weight.

An end-fed is generally the most popular antenna for most activators due to the ease with which it can be deployed. If your radio has an ATU, you can throw one end of a 35.5’ wire over a tree, attach the other end directly to your radio, string a similar length counterpoise through the bushes, and you’re on the air in minutes.

My personal favorite is to zip tie 32’ of wire to a 35’ carbon fiber fishing pole, and to lean the pole against a suitable tree branch. If it’s windy, you’ll need to guy it or to tie it off to the tree. On a treeless summit, three aluminum stakes and three lengths of string will guy it with a few minutes of effort. If you run it through a ‘matchbox’, it’s an end-fed half-wave for 20 meters. (I routinely work the UK and Spain with this.) To switch to 40 meters, run 32’ of wire through the bushes and attach it to the ground terminal on your radio and you have a dipole (or you can think of it as a single-radial vertical, if you prefer).


  • Start with what you have. If you can get it to the summit, it is good enough to get started. You’ve got elevation working in your favor, and many summits are free of RFI. RF in the shack is not something you have to worry about. (There’s no shack and you’re running low power.) Keep in mind that you only need it to stay up for about an hour; this is not a 20-year antenna!

See you on the summits!

73 DE K4KPK / Kevin

Where can I find out more?

  • A popular EFHW:
  • EFHW Central:
  • K4KPK’s site:
  • Email me (K4KPK). My email address is available via


K4KPK, Kevin Kleinfelter is Georgia’s first SOTA Mountain Goat. He has completed more than 150 activations.

This story is Copyright 2015 Kevin P. Kleinfelter. A non-exclusive right to redistribute in electronic or printed form is granted to amateur radio clubs operating in the metro Atlanta area. All other rights reserved.

Winter Activations

A colleague recently asked, “As winter sets in, I guess you’ll be putting your activating on hold until spring, huh? No chance! We’ll take a look at the virtues of cold-weather activations.


  1. I’m discussing southeastern winter weather – not winter at 14,000 feet!
  2. You are responsible for ensuring that you don’t freeze to death - not me.


In winter months, some SOTA regions offer a 3-point bonus on 8 and 10 point summits. The rationalle is to provide extra incentive when ice and cold temperature set in. In the southeast:

  • Tennessee (W4T) give a winter bonus from December 1 - March 31.
  • Georgia (W4G) gives a winter bonus from December 1 - March 15.
  • Virginia (W4) offers a winter bonus from December 1 - March 15.
  • North and South Carolina (W4C) offer no winter bonus.
  • Alabama (W4A) offers no winter bonus.

Why the differences? SOTA associations are local within guidelines set by the SOTA Management Team. The volunteer who authored the association reference manual for W4C chose “not applicable” for the weather bonus, so there is none; the author of the W4G manual felt that a winter bonus was desirable. W4A doesn’t have summits above 2500 feet.

Chasers are assumed to have heat in the shack, so there’s no bonus for chasers.


Many summits require off-trail travel in order to reach them. Bushwhacking is easier when trees are bare and ground vegetation has died back. There’s less brush to push through, you can see where you’re going, and you can see the sun (which is helpful in maintaining your course). As a result, there are many summits which are easier from mid-November through March.


You may have to contend with ice and snow. While ice and snow make for a treacherous drive, winter views can be breathtaking. There is a particular peace that sets in when snow is falling and yours are the only footprints. Some activators like “postman’s spikes” to provide better traction on an icy trail. Trekking poles help to some extent. Fortunately, in the south we seldom have enough snow to warrant snowshoes.

Warm clothing is essential, particularly when the wind is blowing (and the wind is almost always blowing “up top.”) Keep in mind that you’ll work up a sweat when hiking, and then you’ll be sitting on a mountaintop. You’ll need to add layers when you stop climbing. Consider carrying a closed-cell pad to sit on – sitting on a cold rock will suck the heat right out of you.

Do take care when driving up a frozen road that you’ll be able to get out when it thaws. Activators have been known to get stuck when the road melts!

Wrap Up

Don’t forget that daylight ends earlier in the winter. You don’t want to get stuck on Mt. Nowhere after dark.

Check Forest Service Motor Vehicle Use Maps to be sure that the road to the trailhead is open. Many USFS roads are closed in January and February; some are closed even longer.

See you on the summits!

73 DE K4KPK / Kevin

Where can I find out more?

  • Official site:
  • Mailing list:
  • K4KPK’s site:
  • Email me (K4KPK). My email address is available via


K4KPK, Kevin Kleinfelter is Georgia’s first SOTA Mountain Goat. He has completed more than 165 activations.

This story is Copyright 2015 Kevin P. Kleinfelter. A non-exclusive right to redistribute in electronic or printed form is granted to amateur radio clubs operating in the metro Atlanta area. All other rights reserved.

Portable Power

A power source is a requirement for any successful activation. In this month’s column we’ll look at some popular options for powering SOTA activations. Although the occasional activator will use a kilowatt amp, this article will focus on power for QRP portable rigs.

Step Away From the Car Sir

SOTA rules state:

  • Operations must not be in, or in the close vicinity of, a motor vehicle.
  • All equipment must be operated from a portable power source (batteries, solar cells, etc).

Consequently, most activators carry some kind of battery.

For some activators, a walk across a parking lot is an expedition. Others sniff with disdain at anything less than 5 miles with 2000’ of elevation gain. If you’re lugging your gear across a parking lot, you could haul your car battery across the lot in your grandchild’s wagon; if you’re trekking up Denali, grams count!

The Heavy End

Many hams have a SLAB (Sealed Lead Acid Battery) for field day. This is the technology used in your car battery. You can use your car battery, but it is big and heavy and you need to be sure not to discharge it so far that you can’t start your car.

Gel cells are a common alternative to SLAB. For activator use, they are similar to SLAB, except they need not be kept “sunny side up.” They may require special chargers. The removal of the right-side-up requirement is helpful, but they are heavy enough that you won’t often carry one on the trail.

  • Down-side: High weight-to-power ratio.
  • Up-side: Simple technology; inexpensive.

Low-tech, Middle-weight

Disposable alkaline batteries are a popular choice. If you put enough of them in series and/or parallel, and you can meet meet most any power requirement. Some portable rigs include a battery holder for AA cells.

  • Down-side: Expensive over time; disposal of used cells.
  • Up-side: You can buy them anywhere; low-tech; reliable.

Disposable lithium cells are a similar alternative. They’re a little lighter, more expensive, and have slightly different discharge characteristics. Since they retain their charge for up to a decade, they make a good backup power source. I often carry a set of 8 AA lithium cells as a “plan-B” power source.

For my first two years as an activator, I used rechargeable NiMh (Nickel-metal Hydride) cells. These have a similar form factor to disposable alkaline cells. They are rechargeable 100s of times and do not exhibit the ‘memory effect’ of NiCad. They must be charged in a NiMh-compatible charger. Some varieties won’t hold a charge for more than a week or two, but there are long-life varieties that will hold a charge for a year or so.

  • Down-side: Slightly lower voltage than alkalines.
  • Up-side: Simple charging protocol; inexpensive.

I use a KX3. It is designed to operate at 5 watts with 8 internal NiMh cells, but it will operate at 12 watts if I feed it 14-15 volts. This requires 11 NiMh cells, so I made an custom external battery holder.

High-tech, Lightweight

The cool kids are all using rechargeable lithium batteries. These pack a tremendous amount of power into a small, lightweight package. These are very popular with gram counters. Some of these are physically about the size of an AA cell, but since they are 3 volts, please don’t put them into a device designed for AA batteries!

There are several variants of lithium batteries, with unique characteristics. Collectively, they are known as “lithium ion.” The most popular varieties are Li-Po (lithium polymer) and LiFePO4 (lithium iron phosphate). (LiFePO4 are also referred to as ‘LiFePo’ or ‘LFP.’) They require special chargers – each variety requires a different charging protocol. Don’t mix and match!

Up-side (all varieties):

  • Low weight-to-power ratio.
  • Low volume-to-power ratio.
  • Ability to deliver high current.

Down-side (Li-Po):

  • Power-to-cost ratio is expensive.
  • Easy to ruin with over-charge or over-discharge.
  • Short-circuit may lead to fire.
  • Crush/penetration hazard.
  • Concern over excessive fire risk.

Down-side (LiFePO4):

  • Power-to-cost ratio is expensive.
  • Easy to ruin with over-charge or over-discharge.
  • Short-circuit can lead to fire.

Li-Po and LiFePO4 are popular with RC helicopter pilots, due to their light weight and ability to deliver an ‘insanely high’ current. If you short them, expect a fire. With a low internal resistance, they’ll dump all that power into the short in very short order.

The chemistry of LiFePO4 make them substantially less likely to combust than Li-Po. If you short them, the high heat from all that power is still a risk, but these are much safer than Li-Po.

Note that the cells in a lithim ion battery pack should be managed individually. Each cell will have slightly different capacity. Over-discharging any cell may ruin the battery. Over-changing any cell may ruin the battery or create a fire hazard. You will need a battery pack and a charger that support ‘balanced’ charging. This will allow the charger to charge each cell individually, rather than charging the battery as a whole.

Low-tech, Extremely Lightweight

If you want to go really lightweight, consider operating at lower power. Less power intrinsically means less weight. Consider the Mountain Topper (a.k.a MTR, a.k.a. AT-Sprint) radios designed by Steve Weber (KD1JV). These are sometimes sold assembled by LNR, occasionally offered in kit form via a Yahoo mailing list, and turn up on eBay from time to time.

These will operate for many, many QSOs on a standard 9-volt battery. A single alkaline 9-volt battery is reportedly good for more than an hour of activating.


  • Must learn CW.
  • About 3 watts maximum output.


  • Lightest option.
  • Simple, low-tech reliability.


  • Start with what you have. If you can get it to the summit, it is good enough to get started.
  • If you’ve got nothing suitable, AA NiMh cells are a good start. It is robust technology. You can combine cells with a power wand or mix real cells with dummy cells in a commercial battery holder to provide the desired power.
  • To get maximum power for minimum weight, use LiFePO4.
  • If you want absolute minimum weight, get one of KD1JV’s radios and use a 9-volt disposable lithium battery.

See you on the summits!

73 DE K4KPK / Kevin

Where can I find out more?

  • Wikipedia on balanced charging:
  • WB4SON blog on LiFePO4:
  • Official site:
  • Mailing list:
  • K4KPK’s site:
  • Email me (K4KPK). My email address is available via


K4KPK, Kevin Kleinfelter is Georgia’s first SOTA Mountain Goat. He has completed more than 150 activations.

This story is Copyright 2015 Kevin P. Kleinfelter. A non-exclusive right to redistribute in electronic or printed form is granted to amateur radio clubs operating in the metro Atlanta area. All other rights reserved.

Finding Your Way to Nowhere

[This month’s topic is about a subject that could get you hurt. Make sure you understand the risks. Do not rely on this content to keep you safe.]

Initial Planning

After you’ve visited a few summits, you may get a hankering to visit a summit that is… out of the way. Perhaps it is on a remote trail. It might require bushwhacking. This month’s topic is how to get to the middle of nowhere.

After you’ve visited, you’ll have a good idea of where your summit is located. You just need to figure out how to get there. (If you’re lucky, there will be a trail marked on SOTAmaps.)

When planning a hike to a summit, the first thing I do is to Google the name of the summit and the words trail, trailhead, or hike. If someone has written up a guide, this search will usually find it.

Topographic Maps

The next resource to check is a USGS topo. Visit and select “Map Locator & Downloader.” You can use this to download topographic maps (often called “quads” or “quadrangles”). These maps show mountains, streams, dirt roads, trails, and other geographic features. You may have learned to read these as a Scout. You can download PDF files with the exact map you would see on a paper map. These are big files; they will take time to download and your PC display them sloooowly. If you prefer, you can purchase paper maps from the same site.

There will be many editions of a map on the USGS site. I usually download the 2 or 3 most recent, look to see which is intelligible, and discard the rest. The newest edition often adds aerial imagery, which makes them tough to read.

Take a quad with a grain of salt. Just because it shows a road/trail is there, it doesn’t mean the route is passable. If you see a candidate route, use Google Earth to see if you can find evidence that the road/trail is still there. When you travel, the reality on the ground supersedes the reality on the map!

National Geographic Trails Illustrated maps are an excellent resource, if there is a map for your destination. These are much like a quadrangle, except they often contain more relevant detail.

Reaching the Trailhead

Once you’ve found a trail, you’ll need to navigate the drive to your trailhead. Google Maps has worked well for me for 90% of my back-country trailheads. Occasionally, it thinks that a power line right-of-way is a road, so watch out for unnaturally straight lines on the route. Occasionally, it will route you via a closed Forest Service road. You can check for gates on the relevant [Forest Service Motor Vehicle Use Map] (

A Word About GPS

When you head out into wilderness, you may elect to carry a GPS. Don’t take a GPS designed for use in a car! You don’t want a street GPS; you want a topographic GPS. I recommend using a dedicated GPS and not a smart phone app. The dedicated GPS will show your position more accurately and its batteries will last much longer. (I’ve found multiple people on the trail who were using an app who were not clear on their location.) I recommend a rainproof GPS. I have one with a tiny little screen, and I’ve never really needed a bigger display. You will want a GPS with a moving map display, and not just a latitude/longitude display.

Do not rely on your GPS to get you back to the car. Pay attention to your route. Have a plan for how to find your car if the GPS fails. Risks include electronic device failure, a geomagnetic storm, dead batteries. (I once dropped my GPS as I was crawling through rhododendron.)


If you bushwhack, navigating to a summit is easier than navigating back to the trail. If you’re on the right mountain, heading up will eventually reach the summit. When you come down, there are an infinite number of destinations you reach by heading down.

I avoid bushwhacking unless the sun is shining; I prefer to bushwhack in the winter. It is easy to travel in a straight line when you can see your shadow. If your GPS conks out, you should know the general direction to head in order to find the trail. When planning your trip, plan a fail-safe route back to the trail that has you hitting a long stretch of the trail perpendicularly. You want to know that even if you’re off course by 30 degrees, you’ve got a big target to hit.


I won’t get into general wilderness safety. For that, is a good place to start.

Some really nice summits are off the beaten track. They just require a little more planning. To get you started, guides for several southeastern summits can be found at SOTA Trip Library.

See you on the summits!

73 DE K4KPK / Kevin

Where can I find out more?

  • Official site:
  • Mailing list:
  • K4KPK’s site:
  • Email me (K4KPK). My email address is available via


K4KPK, Kevin Kleinfelter is Georgia’s first SOTA Mountain Goat. His first QSO was on a SOTA activation. He has completed more than 150 activations.

This story is Copyright 2015 Kevin P. Kleinfelter. A non-exclusive right to redistribute in electronic or printed form is granted to amateur radio clubs operating in the metro Atlanta area. All other rights reserved.

Where Can I Buy a KD1JV Mountain Topper?

  1. Check eBay. One turns up every few months. Sometimes assembled; sometimes an unassembled kit.
  2. Monitor the AT_Sprint Yahoo mailing list. One turns up every few months. Sometimes assembled; sometimes an unassembled kit.
  3. sells assembled MTR for about $250.

SOTA Web Resources

You can’t “do SOTA” without using the web. There is one essential site, several which are almost indispensable, and some that are somewhat useful. You may find it helpful to open a web browser and visit the referenced sites as you read this article.

SOTAData - Essential - You can’t get by without SOTAData. This is where you record your QSOs. Some of the key activities on the main menu include:

  • Logon/Logoff - You’ll need to visit the “Register” sub-menu to sign up for an account. There’s no cost to register and they don’t spam you. Registering is not a commitment to activate or chase!
  • View Results - You can view metrics about SOTA such as the count of registered summits (73,548), rankings of activators and chasers, and there’s a special sub-menu for viewing your own results including your activations, unique summits, summit-to-summit (S2S) contacts, awards, etc. After each activation I check the “Activator Roll of Honor”… and confirm that I still haven’t earned enough points to move up in the national ranking. :-(
  • Summits - If you’re an activator, you’ll research a summit here before you head out on an expedition. This is where you find the list of official summits, how many points each summit is worth, who has activated it. (Tip: If lots of people have activated it, it is an easy summit.) Once you locate a summit, the “Extra Info” link will take you to a page where prior activators write-up how to get to the summit and what to expect when you arrive. One of the first places to visit when planning an expedition.
  • Submit Log - This is where you record your QSOs. There’s a sub-menu for entering QSOs one at a time. You’ll probably use this for your first few activations/chases. You’ll want to quickly move up to uploading CSV files. The CSV format is unique to SOTA, but several logging apps now support SOTA format.

SOTAWatch - Very Helpful is where activators post alerts to tell you when/where they plan to activate. Once a chaser hears an activator, he will typically spot the activation here too. Self-spotting is considered acceptable for SOTA.

If you have an iPhone, SOTA Goat uses SOTAWatch data to bleat a notice whenever a new spot is posted. There are also apps for Android, Windows, and OS X that perform similarly. The data from SOTAWatch is also posted to Twitter.

SOTA Goat and its ilk are particularly helpful if you’re interested in S2S contacts. If you’re on a hill with cell coverage, you can get notified when other activators are on the air, giving you the info you need to call them.

SOTAWatch Chaser/Logger - Interesting for Chasers spotfilter shows recent spots. What makes it interesting is that if you are a busy chaser, you can select spots and then download them into your log book.

SOTAMaps - Very Helpful shows the location of summits on a map. This helps you visualize just how far you’re going to have to drive. Here’s a helpful URL which plots 700+ summits within driving distance from Atlanta. The left panel is color coded to show you which summits have/haven’t been activated.

North American SOTA Mailing List - Helpful hosts the official mailing list for the North American SOTA community. (Yahoo login required.) This is where you can ask other activators and chasers for how-to information. There are some clever antena and balun designs posted here on occasion.

Like many Yahoo groups, a popular pastime is complaining about Yahoo. If you visit the site once, you can sign-up to have postings delivered to your email and you’ll never have to look at Yahoo again.

My SOTA Site - Somewhat Helpful may also be of interest. It has how-to information, an archive of newsletter articles, and a library of trip plans for southeastern summits.


See you on the summits! 73 DE K4KPK / Kevin


K4KPK, Kevin Kleinfelter is Georgia’s first SOTA Mountain Goat. He has completed more than 150 activations.

This story is Copyright 2015 Kevin P. Kleinfelter. A non-exclusive right to redistribute in electronic or printed form is granted to amateur radio clubs operating in the metro Atlanta area. All other rights reserved.

Learning Links

Here are some sites I find helpful for learning ham radio and electronics:

  • All About Circuits textbooks
  • LCWO - morse code
    • Browser based: Random character groups for extended duration, sends-a-word/enter-that-word, sends-a-callsign/enter-that-sign
  • AA9PW - morse code
    • Browser based: Random character groups, call signs, RSS headlines, QSO. Many RSS feeds now fail to load.
  • AA9PW - Ham Morse
    • iPhone/iPad: Similar to his web site in features and in issues. Many RSS feeds now fail to load.
  • ZL1AN Teach
    • Windows: 950 supplied texts can be played at any speed
  • G4FON
    • Windows: Does random words. (You have to set the “Characters” control to 40 in order to see the “Words” button.)

Note: For the CW trainers, I don’t list the basic capabilities used to train you in the initial character set. I’ve passed that point, so I’m focusing on the drills that will take me from basic competency to faster send/receive of real-world content.

Sisyphus the Activator

Sisyphus the Activator

Sisyphus Image

Activation Points Once Per Year

A SOTA activator can get points for activating a given summit once each calendar year. For example, if you ride the tram to the top of Stone Mountain and you make 4+ QSOs from the summit in 2015, you collect two points. If you activate Stone Mountain again in 2015, you get zero additional points. When 2016 arrives, you become eligible for 2 more points.

A Peculiar Activator

So why does one ham activate San Bruno Mountain and Mt. Davidson again and again? As of mid-2015, he’s activated San Bruno Mountain alone more than a dozen times this year!

  • Maybe he lives there? Unlikely. It’s a typical radio/TV tower summit.

  • Maybe he really likes San Bruno Mountain? Possibly, but he does something unusual from that summit… he makes summit-to-summit contacts.

K6EL is the leading summit-to-summit activator in the United States, with more than twice as many “S2S” contacts as his nearest competitor. (The superlative metric about K6EL is that he has the lowest points per climb of any activator in the world!)

A key appeal of these summits is that they are convenient to his home and they have strong cell signal. Cell signal is important, because it allows him to use SOTAwatch to identify other activations in progress. With this information, he’s able to call the other activator and make the contact.

Your Advantages

There are a number of hills near Atlanta with similar advantages, including Stone Mountain, Kennesaw Mountain, and Pine Mountain. For Stone Mountain, you could carry a folding chair and your cooler!

Unless you’ve got a truly outstanding antenna at home, you’ll find that you get better signal reports operating QRP from the top of a summit than QRO at home. You’ll certainly get more pile-ups from a SOTA summit than your Atlanta-area shack. (Activators can get points for the same summit once per UTC day, so they’ll call you each time.) QRM is low from most summits. (Get away from the building on top of Stone Mountain, to minimize QRM there.) If you’re a VHF operator, line of sight is great on a summit.


Summit-to-summit contacts are often regarded as particularly challenging. You’ll have two QRP rigs and two portable antennas on the QSO, and you’ll be competing against QRO chasers with beams. A little patience is all that’s needed! A SOTA pile-up typically lasts only 5 minutes or so. Once the fuss has died down, you’ll be heard. When you send your call sign, be sure to state, “Summit-to-summit.” Other stations typically yield when they hear this. (And you’ll compete surprisingly well, given your elevation.)

Facts Supporting the Extra Class License Exam

I’m studying for the Amateur Extra Class license exam. I want to pass, but I’m not seeking a perfect score. (Perfection is not an effective use of my time.) I’m willing to memorize facts but not answers. The difference is that a fact is something useful after the exam.

However, I will memorize an occasional answer or write-off a question if the amount of learning is enormous just to answer a few questions.

These are just the things I have to learn. I’m not capturing things I already know, such as Ohms law. (the “Read Questions” link) is very helpful. Many of the questions have explanations associated with the answers.

  • Reminder: micro and mega both deal with a million (106). Pico is million million (1012).
  • Circulator - a three- or four-port device, in which an RF signal entering any port is transmitted to the next port in rotation (only).
  • Receiver performance measures
    • MDS = Minimum Discernable Signal
    • Dynamic range = space between weakest signal radio can receive and strongest it can handle w/o excess distortion.
    • Desense (a.k.a. blocking) = close frequency at strong level drives RF amp to compression (non-linear behavior).
      • Narrowing receiver bandwidth reduces this because “close” means within the receiver passband.
    • Cross-modulation = modulation of a close frequency superimposes on desired frequency.
    • Phase noise in the local oscillator of a receiver can mix with nearby frequencies to interfere with the tuned frequency. (It creates a signal that mixes with the nearby frequency.)
    • Blocking Dynamic Range = dB between noise floor and incoming signal level which will cause 1 dB of gain compression. In effect, it is the signal strength range the receiver can handle.
  • Intermodulation
    • Intermodulation products are the emissions at frequencies generated by the combination of two or more frequencies in a non-linear device, such as the output stage of a transmitter, or the input stage of a receiver (or corroded connections). E.g. (f1 - 2*f2). Mixing often occurs in a non-linear RF amp.
    • A circulator reduces intermod by preventing signals received in the transmitting antenna going back into the transmitter amplifier and mixing.
  • 3rd order intercept
    • a 3rd order intercept of x db means that a pair of signals will theoretically generate a third-order intermodulation product with the same level as the input signals
    • 3rd order intermod products created within a receiver are of interest because the 3rd order product of two signals in the band of interest is also likely to be within the band
  • Resonance
    • At resonance, the L and C components of an RLC circuit go to zero, leaving only R.
    • In series, when L and C cancel, you have lower total RLC impedance, so more current flows. (This is like removing 2 of 3 resistors that are in a series. R goes down.)
    • In parallel, when L and C cancel, you have higher impedance between the two rails, so less current flows. (This is like removing 2 of 3 resistors that are in parallel. R goes up.)
    • L and/or C shift the phase between voltage and current in opposite directions. Ergo, at resonance, there is no shift because AC circuits that are resistive have no phase shift.
    • F = .159 / sqrt(LC)
      • Note: This is true when the units on L and C are similar. (e.g. Farads and henries, or micro-farads and micro-henries.) On the exam, they mix micro-henries with pico-farads, so you use: F = 1000 * .159 / sqrt(LC).
        • i.e. On the exam, calculate F = .159 / sqrt(LC) without regard for units, and then multiply by 1,000
  • Time constant
    • One time constant = all but 37%.
      • e.g. Discharging to 37% in one time constant.
      • e.g. Charging to all but 37% (meaning charged to 63%) in one time constant.
    • Calculating a time constant: T = RC
      • On the test, if you forget, pick the answer that is closest to the microfarad value (for all calculate-the-TC questions)
  • Q
    • Half_Power_Bandwidth = Frequency / Q. [B = F/Q]
      • e.g. If Q = 10, and Frequency = 10 MHz, then Bandwidth = 1MHz.
      • e.g. If Q = 95, and Frequency = 1.8 MHz, then Bandwidth = 1.8 / 95 = 0.0189 MHz = 18.9 KHz.
  • Gates
    • The symbol for the AND gate is rounded.
    • The symbol for the OR gate looks like AND with a pointy rounded end.
    • A triangle is a no-op.
    • The symbol for Nxxx is a little circle at the tip of AND / OR / no-op
    • XOR (and XNOR) have a double line at the input side. e.g.
  • Phase-locked Loop = An electronic servo loop consisting of a phase detector, a low-pass filter, a voltage-controlled oscillator, and a stable reference oscillator.
  • If no antenna reference is specified for gain, assume a dipole. (Otherwise, EIRP = Effective Isotropic Radiated Power.)
  • ERP:
    • Add up the dB gain and loss for total dB. Call that TDB.
    • TPO = Transmitter Power Output
    • ERP = InverseLog(TDB/10) * TPO
    • On a TI-36X Pro Calculator, Double-tap [ex 10x] for InverseLog
      • Double-tap “ex 10x”
      • Open paren, TDB / 10, close paren
      • x TPO
    • e.g.
      • If watts is 50 and gain is - 4 dB - 2 dB -1 dB + 6 dB = -1 dB
      • press InverseLog (-1 / 10) * 50
      • press Enter
  • On XY RLC charts, Resistance is to the right; inductance is up; capacitance is down. Pure L or C is way up/down; mixed is near mid-line.
  • A sawtooth wave is made up of a sine wave plus all its harmonics. A square wave is made up of a sine wave plus its odd harmonics.
  • -174 dBm/Hz = The theoretical noise at the input of a perfect receiver
  • Matches:
    • A delta match feeds at two places, each side of center.
    • A gamma match feeds at the center and off one side (like my Arrow VHF Yagi).
    • A stub match runs feed line and radiator in parallel near the feed point
  • P-type uses holes; n-type uses electrons. P = positive, so it has holes (which are anti-electrons); N = Negative, so it has electrons (which are negative).
  • VCC is supplied to MMIC (monolithic microwave integrated circuit) via resistor or a choke on the amplifier output.
  • Spurious emissions must be down 43 dB
  • A hot-carrier (Schottkey) diode is often used as a VHF/UHF detector/mixer.
  • Digital protocols
    • JT65 is designed for moon-bounce
    • PSK31 is narrowest bandwidth. 31 baud and 31 Hz bandwidth. It uses variable-length characters.
    • MFSK16 is FSK with 16 tones; about 300 Hz bandwidth.
  • 120V RMS is 170V peak-to-peak. It is 120V * sqrt(2).
  • An op-amp has high input impedance and low output impedance. (This is what you want. Low-drain input, and low-resistance output.)
  • A marker generator can be used to calibrate a receiver. (Send at a known frequency and see what frequency the receiver thinks it is.)
  • a FET has gate, drain, and source
  • A point-contact diode is a “cat’s whisker” diode.
  • P= IIR
    • This can be derived from P=EI and E=IR
  • Deviation Ratio:
    • Modulation index = DeltaCarrier / Modulation
    • Deviation ratio = MaxDeltaCarrier / MaxModulation
    • Highest allowed modulation index for angle modulation = 1
  • Space stations, Satellites, and Moon:
    • HF - not allowed on 30m (because that’s CW-only)
    • VHF - only allowed on 2 meters
    • UHF - allowed on 70, 23, and 13 cm
    • Mode x/y - uplink before downlink. (Must get TO the satellite before the signal comes FROM the satellite.)
    • Moonbounce at 144.0 to 144.1 (First 100 KHz of 2 meter band). Also at 432.0 to 432.1 (100 KHz, but not at bottom of 70 cm.)
    • Meteor from 10 to 2 meter (28 to 148 MHz).
    • Aurora and mEteor strike happens at the E-layer
  • PSK31 - (Phase Shift Keying, 31-baud) has data rate close to typing speed, and has extremely narrow bandwidth
  • Spread spectrum is permitted above 222 MHz
  • Line-A takes a chunk out of the BOTTOM of the 70 cm band (400 MHz)
    • (“A” is the beginning of the alphabet; Line-A loses the beginning of the band; 400 MHz is the only band in the answers with multiple, close answers.)
  • dB = 10 Log (x/y)
    • Log is base 10
    • e.g. 400x increase in power = 10 Log (400/1) = 26 dB
  • A noise blanker briefly switches off the receiver when a broadband spike occurs. (Not “broadband white noise” and not a narrowband spike.)
  • X,Y graphing of RLC:
    • R is to the Right of the vertical axis.
    • L is up
    • C is down
    • Reactance of an inductor is 2pi * FL
    • Reactance of a capacitor is 1/(2pi * FC)
  • Impurity atom that adds holes to a semiconductor = “Acceptor impurity”. (Mnemonic Atom and Acceptor.)
  • Filter types:
    • Jones Filter - a type of crystal lattice filter