Glenn W9IQ
  • Member for 4 years, 9 months
  • Last seen more than a month ago
How does the signal know where the cable ends and the antenna starts?
27 votes

An excellent question! Without diving too deep into the theory, let's start with a few basic terms. The "signal" that an antenna is receiving or transmitting is called an electromagnetic wave. This ...

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How does an SWR meter really work?
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22 votes

Dispelling the Myth To begin with, the typical HF SWR meter does not have the ability to separately sample the forward and reverse power, voltage, or current. Any description of the device or its ...

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Can I build a radio telescope out of a parabolic TV satellite dish?
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16 votes

The primary factor to consider is the directivity of the parabolic antenna. It is given as: $$d=\frac{(\pi D)^2}{\lambda^2} \tag 1$$ where D is the diameter of the dish and $\lambda$ is the ...

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How do PTT buttons work?
14 votes

The basic PTT (push to talk) button on the HT is a simple switch that is normally open and when it is pressed, the switch is closed (conducting). Internally to the radio, this applies power to the PA (...

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Is this a broadcasting antenna?
13 votes

It appears to be a "vertical" CB ground plane antenna that had been mounted or stored in a horizontal orientation. It is not suitable for effective TV or FM reception. It is also noteworthy that one ...

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What is an antenna tuner? Why bother with resonant antennas in the first place?
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12 votes

And if it is possible to use a tuner to make a transmitter feed power into a coat hanger then why do we worry about making resonant antennas in the first place? In a word - efficiency. Consider that ...

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Why can't I hear myself from a second radio when bouncing off a repeater?
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12 votes

You are experiencing what is commonly called desense (short for desensitization). The strong signal of your transmitter overloads your receiver making it unable to demodulate the much weaker, on-...

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Why do we have to hand wind toroids?
12 votes

I suspect the primary reason that the kit supplier does not ship the kit with prewound toroids is that there is insufficient volume to make it economical to have them commercially wound. A second ...

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Antenna Efficiency
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12 votes

In theory, if you had lossless conductors in the antenna and a lossless matching network, your shortened, 1 foot dipole would have a gain of only ~0.7 dB less on 160 meters than the gain of a full ...

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What happens to your callsign if you migrate?
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11 votes

I have done exactly that. I had a US amateur extra class license when I moved to Germany. As a legal resident of Germany, I applied for and received a reciprocal (no test required) German license ...

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Is it legal to transmit scrambled or encrypted voice via SSB on ham bands?
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11 votes

In the US, the FCC prohibits this type of operation if the purpose is to obscure the meaning of your transmission. 97.113 Prohibited Transmissions (4) ... messages encoded for the purpose of ...

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Do FCC regulations limit digital data rate?
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11 votes

The Current FCC Regulations (as of July 2018) Parts 97.305(c) and 97.307(f) regulate digital modes primarily by symbol rate. The table in 97.305(c) maps bands/frequencies to specific symbol rate ...

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Is using /AE compulsory?
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11 votes

The key wording is in 97.9(b) as referenced in 97.119: ...is authorized to exercise the rights and privileges of the higher operator class... and 97.119 says: "When the control operator is a ...

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Attic Dipole - Impact of Ethernet over CAT5/6
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11 votes

Having Ethernet and your antenna co-located is not an ideal situation. But then most amateur antenna situations involve compromises. The general idea of the following recommendations is to take as ...

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Ham operators often tell me that comparing gain to an isotropic radiator isn't much use because it's only a theoretical antenna, is this true?
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9 votes

Ham operators often tell me that comparing gain to an isotropic radiator isn't much use because it's only a theoretical antenna, is this true? No, that is not true. I generally find that hams that ...

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From where do repeaters get their power supply?
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9 votes

You are correct that most repeaters that are on buildings or typical towers get their energy from the commercial grid. The repeaters that I own are all commercially powered. Repeaters that are ...

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Antenna polarization when dealing with satellite communications
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9 votes

Satellite engineers tend to use circular polarization for two reasons: When a linearly polarized signal travels through the atmosphere there are anomalies, such as Faraday rotation, that alter the ...

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USA/callsigns: Why is California region 6? And the midwest in regions 7-9?
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9 votes

The origins of the amateur radio call sign districts can be traced to 1912 when the Department of Commerce, Bureau of Navigation created nine radio inspection districts to enforce the 1912 Act to ...

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How can Ground Penetrating Radar work?
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9 votes

There is a special adaptation of the Friis equation, called the Radar Equation, that describes the range of a radar system. Here is a basic version that calculates the maximum range of a radar system: ...

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Efficiency of short dipole receiving antenna
8 votes

The efficiency of any antenna has a direct impact on the gain of the antenna. The gain of the antenna equally effects transmit and receive - a characteristic known as reciprocity. The highest gain ...

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Soldering PL-259.. with a torch?
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8 votes

Our friends in the UK and other parts of the world are now wondering how you could even begin to solder a PL259 connector with a torch (aka flashlight)! But in their vernacular, you of course are ...

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Why do the metres seem to be increasing with frequency?
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8 votes

It is simply an error or typo on that website. Take a look at the companion color chart on that page that is provided by the ARRL. It shows that frequency range as 160 meters. The formula for ...

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Share wide band antenna with multiple transceivers
8 votes

The basic concept is to use RF bandpass filters for each frequency range. This is frequently done by hams for VHF and UHF applications. The common term for a grouping of these filters is diplexer, ...

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What is the advantage of making an antenna resonant?
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8 votes

Resonance or non-resonance does not have a direct effect on the efficiency or gain of the antenna. A resonant antenna is one that has only resistance without any reactance (capacitive or inductance) ...

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How can I get rid of RFI coming from my house solar panel inverter?
8 votes

The inverter in your solar panel system utilizes a high frequency switcher to regulate the voltage and convert it to AC for feeding back into the mains. Some solar panels also use an "optimizer&...

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FCC callsign with incorrect group letter
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8 votes

When the FCC issues your first call sign to you, they do not look backwards through their list of assigned call to see if there are any unused calls that they can reassign. Instead, they use a ...

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Will stainless steel bolts work with my copper antenna?
8 votes

Stainless steel fasteners, lead and tin are compatible with copper. Lead tin solder, however, has poor mechanical strength as you have apparently discovered. Solder can be used to improve conductivity ...

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Cell Tower distance measurement
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8 votes

One approach would be to capture the GSM Cell ID. This uniquely identifies a particular GSM site. You can then lookup this ID in a database such as one offered by Cobain to determine the tower ...

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Series resonant circuit, how to calculate voltage across the capacitor?
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8 votes

I encourage students to draw a simple schematic when it comes to word problems such as these. Here is an ideal series resonant circuit: simulate this circuit – Schematic created using ...

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Can jamming a channel with white noise be detected?
8 votes

The station would not really transmit static but rather white (or perhaps pink) noise. This would sound like static but as the observer tunes across the transmitter's frequency, the static would ...

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