KB6NU's Ham Radio Blog

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Ham radios $64,000 question

Posted: 03 Feb 2016 06:40 AM PST
http://feedproxy.google.com/~r/kb6nu...m_medium=email


In this mornings e-mail, someone innocently asked:

I have a quick question for you. My boyfriend will be getting his Ham Radio
license soon and I want to surprise him and buy him a good beginner ham
radio for his birthday. But, I have no idea whats good, what to look for,
etc

Would you be able to point me in the right direction?

Thanks for you time,

Sarah

I replied:

Hi, Sarah:
This is, of course, ham radios $64,000 question, and Im afraid that theres
not really a quick answer.
A lot of it depends on what your boyfriend wants to do in amateur radio.
There are so many different things that you can do, and there isnt a single
radio that does it all, and if there was one, you probably couldnt afford
it.
You might take a look at the article Choosing a Ham Radio. It provides some
guidance on what to think about before you buy a radio and then what to
look for. Unfortunately, its written for those who already have a license
and are somewhat familiar with the terminology already.
Most hams start out with a radio that lets them talk to other hams on the
144 MHz (2m) or 440 MHz (70 cm) amateur radio bands. For that, I have two
suggestions:

Baofeng UV-5RA. This radio costs less than $30, although you will probably
also want to buy a replacement antennaÂ*for it. This is not the most rugged
radio on the market, but it does work, and will get your boyfriend started.
Some guys have reported problems with the radio, but Ive had one for more
than two years, and mine is still working fine.
If you have a little more to spend, you might consider the Yaesu FT-60R. It
costs $165, but its a more rugged radio from a good manufacturer.

I hope that helps a little.
73! Â* ham radio lingo for best regards
Dan KB6NU

Now, its your turn. What would you recommend Sarah buy? Im sending her the
link to this blog post, so that she can read what you recommend, too.



The post Ham radios $64,000 question appeared first on KB6NUs Ham Radio
Blog.


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2016 Extra Class study guide - E7B - Amplifiers

Posted: 02 Feb 2016 05:14 PM PST
http://feedproxy.google.com/~r/kb6nu...m_medium=email


There are three fewer questions in this section. The question on klystrons,
for example, was removed. Some of the other questions were changedDan
E7B Amplifiers class of operation; vacuum tube and solid-state circuits;
distortion and intermodulation; spurious and parasitic suppression;
microwave amplifiers; switching-type amplifiers

There are several classifications of amplifiers, based on their mode of
operation. In a class A amplifier, the transistor is always conducting
current. That means that the bias of a Class A common emitter amplifier
would normally be set approximately half-way between saturation and cutoff
on the load line. (E7B04)

In a class B amplifier, there are normally two transistors operating in a
“push-pull� configuration. One transistor turns on during the positive half
of a cycle, while the other turns on during the negative half. Push-pull
amplifiers reduce or eliminate even-order harmonics. (E7B06)

A Class AB amplifier operates over more than 180 degrees but less than 360
degrees of a signal cycle. (E7B01) Class B and Class AB amplifiers are more
efficient than Class A amplifiers.

A Class D amplifier is a type of amplifier that uses switching technology
to achieve high efficiency. (E7B02) The output of a class D amplifier
circuit includes a low-pass filter to remove switching signal components.
(E7B03)

Amplifiers are used in many different applications, but one application
that is especially important, at least as far as signal quality goes, is RF
power amplification. RF power amplifiers may emit harmonics or spurious
signals, that may cause harmful interference.

One thing that can be done to prevent unwanted oscillations in an RF power
amplifier is to install parasitic suppressors and/or neutralize the stage.
(E7B05) An RF power amplifier be neutralized by feeding a 180-degree
out-of-phase portion of the output back to the input. (E7B08) Another thing
one can do to reduce unwanted emissions is to use a push-pull amplifier.

In order to preserve signal integrity, amplifiers used as the final
amplifier in an amateur radio transceiver, or as an external amplifer, are
Class A or Class AB linear amplifiers. The use of non-linear Class C
amplifiers is not a good choice. The reason for this is that signal
distortion and excessive bandwidth is a likely result when a Class C
amplifier is used to amplify a single-sideband phone signal. (E7B07)

Although transistorized linear amplifiers are becoming more common, many
high-power amplifiers still use vacuum tubes. These amplifiers require that
the operator tune the output circuit. The tuning capacitor is adjusted for
minimum plate current, while the loading capacitor is adjusted for maximum
permissible plate current is how the loading and tuning capacitors are to
be adjusted when tuning a vacuum tube RF power amplifier that employs a
pi-network output circuit. (E7B09)



The type of circuit shown in Figure E7-1 is a common emitter amplifier.
(E7B12) In Figure E7-1, the purpose of R1 and R2 is to provide fixed bias.
(E7B10) In Figure E7-1, the purpose of R3 is to provide self bias. (E7B11)



In Figure E7-2, the purpose of R is to provide emitter load. (E7B13) In
Figure E7-2, the purpose of C2 is to provide output coupling. (E7B14)

Thermal runaway is one problem that can occur if a transistor amplifier is
not designed correctly. What happens is that when the ambient temperature
increases, the leakage current of the transistor increases, causing an
increase in the collector-to-emitter current. This increases the power
dissipation, further increasing the junction temperature, which increases
yet again the leakage current. One way to prevent thermal runaway in a
bipolar transistor amplifier is to use a resistor in series with the
emitter. (E7B15)

RF power amplifers often generate unwanted signals via a process called
intermodulation. Strong signals external to the transmitter combine with
the signal being generated, causing sometimes unexpected and unwanted
emissions. The effect of intermodulation products in a linear power
amplifier is the transmission of spurious signals. (E7B16) Odd-order,
rather than even-order, intermodulation distortion products are of concern
in linear power amplifiers because they are relatively close in frequency
to the desired signal. (E7B17)

One type of amplifer that is often used as a power amplifier is the
grounded-grid amplifier. Grounded-grid amplifiers are relatively easy to
build, and they are very stable in operation. One characteristic of a
grounded-grid amplifier is low input impedance. (E7B18)

The post 2016 Extra Class study guide E7B Amplifiers appeared first on
KB6NUs Ham Radio Blog.


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Amateur radio videos: NPOTA, reuse an LCD display

Posted: 02 Feb 2016 01:09 PM PST
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Mike Wendland,Â*of the “PCMikeâ€� tech segment on NBC-TV and the
roadtreking.com website and podcast, sets upÂ*a radio station on the North
Country Scenic Trail in Michigans Upper Peninsula as part of the ARRL and
National Park Service National Parks on the Air event.



Having a second monitor for your PC is really helpful sometimes. In this
video the author turns the LCD Screen of a broken laptop into a nice
looking second monitor for your PC, gaming console or Raspberry Pi.

The post Amateur radio videos: NPOTA, reuse an LCD display appeared first
on KB6NUs Ham Radio Blog.