Glenn W9IQ
  • Member for 4 years, 8 months
  • Last seen more than a week ago
4 answers
2 votes
9k views
If i connect two antennas to one radio using a t connector will it work?
8 votes

Assuming that both antennas are 50 Ω resistive, they will combine in parallel for a 25 Ω load impedance when transmitting. This will cause the transmitter to see a 2:1 SWR. This is a 0.333 voltage ...

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6 answers
9 votes
13k views
Aluminum vs copper antenna element lengths
8 votes

Besides mechanical differences, the primary difference between aluminum and copper in antenna construction is RF resistance. Copper will have slightly less RF resistance for the same surface area. ...

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1 answers
1 votes
56 views
Sending a downloaded file on digital: third party communication?
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7 votes

From a Part 97 perspective, the definition of third party communications is: Third party communications. A message from the control operator (first party) of an amateur station to another amateur ...

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3 answers
6 votes
2k views
Coax or bifilar windings for a choke?
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7 votes

In most multi-band balun applications, there is rarely a need to maintain a perfect 50 ohm impedance within the balun. The feedpoint or input impedance is varying widely so another impedance bump in ...

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1 answers
5 votes
1k views
How to find something disrupting car key fobs across a parking lot?
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7 votes

There was a similar problem in the US a few years ago and it turned out to be a new shop sign that had a defective ballast that emitted a wide RF spectrum. Most key fob systems operate at ...

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1 answers
1 votes
101 views
Frequency mixing products
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7 votes

When two sinusoidal signals are multiplied through a non-linear mixer circuit, it results in the sum and difference of the mixed frequencies: $$f_s=f_1+f_2 \tag 1$$ $$f_d=f_1-f_2 \tag 2$$ Of course, ...

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2 answers
7 votes
306 views
Water cooling a GS-35B in lieu of air cooling?
7 votes

The GS-35A tube is the liquid cooled version of the same tube. Some hams have fabricated their own version of a liquid cooling jacket to replace the fins on the GS-35B: The designer of this jacket ...

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2 answers
5 votes
972 views
Is there a best ratio of L to C in a resonant circuit?
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7 votes

There is no hard and fast rule. Consider that in some LC circuit applications, a lower Q may be desirable in order to achieve a wider bandwidth. In other cases, a very high Q may be desirable for ...

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5 answers
10 votes
1k views
Are there formulae to calculate capacitance and inductance of an antenna?
7 votes

A couple of minor comments on terminology. It isn't so much the "internal" impedance of the antenna but it is typically the "feed point" impedance that is of concern. This is the impedance seen where ...

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2 answers
2 votes
1k views
Fast TCP/IP radio modem on UHF band
7 votes

As you might suspect, the data rate impacts the required RF bandwidth. Besides the data rate, the modulation method, encoding, packet overhead, duplexing, and other factors ultimately determine the ...

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2 answers
5 votes
798 views
What are the implications of pulling LMR400 through EMT conduit with several 90 degree conduit body fittings
7 votes

I am sure you will get many good suggestions for your situation. The higher quality coax cables do have a specification for their minimum bend radius during install. For LMR-400 it is 1 inch (25.4 ...

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1 answers
5 votes
210 views
What is this connector?
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7 votes

It looks like a female TNC connector.

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2 answers
5 votes
2k views
How can I calculate the 1/4-wave monopole impedance dependence on groundplane angle?
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7 votes

Once a ground plane antenna is 0.5 wavelengths or so above ground, there is no significant effect from the ground on the impedance of the antenna so it can be ignored. A close approximation of the ...

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3 answers
6 votes
966 views
Can an antenna be too powerful for certain receivers?
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7 votes

Would the portable ~$40 Tecsun get damaged somehow by a 100-foot antenna because it's designed to work with shorter, portable antennas?  Unless you are within a kilometer or two of a very high power ...

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2 answers
8 votes
12k views
calculating all specifics for a 5/8 antenna
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7 votes

I congratulate you on your interest in working out the design issues from the ground up. Understanding the theoretical and comparing this to the field results is the beginning of a life long enjoyment ...

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1 answers
6 votes
320 views
Why is the neper a useful unit for transmission line calculations?
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7 votes

A neper, just like a decibel, is a logarithmic expression of ratios. The decibel uses the base-10, or decadic, logarithm while the neper uses the natural, or Euler constant, logarithm. The decibel is ...

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1 answers
3 votes
2k views
Is Part 90 certification something an amateur radio operator should look for in a radio meant for amateur use?
7 votes

Part 90 certification is required for radios used in the USA in the land mobile services - often called commercial radio. No such certification is required for the amateur radio service. The closest ...

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1 answers
11 votes
191 views
Is there a special name (and if so what is it) for this flush-style SMA variant?
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7 votes

It is known as an SF style SMA connector. It is also commonly known as a Motorola SMA connector since they seem to be one of the few large scale users of this style connector You can find some ...

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3 answers
2 votes
2k views
How do I set up my radio for an antenna tuner?
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7 votes

Your TS430S has a solid state final and no internal antenna tuner. As such it is designed to work into a 50 ohm load at all times. This means you can disregard this note in your antenna tuner manual. ...

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5 answers
16 votes
10k views
If I receive an SOS signal, what is the proper response?
6 votes

Since this is all for a bit of fun, you could respond with the typical Morse Code response to indicate that the last transmission was successfully received: R: •-• Some operators stylize this as ...

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3 answers
5 votes
470 views
Is compression "encryption" under FCC regs?
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6 votes

For governments around the world to continue to trust that amateur radio has no nefarious purpose, it is essential that everyone that wishes to, can "listen in" to any amateur radio communications. ...

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1 answers
4 votes
292 views
What are Radio-location Services in the 1.9-2.0 MHz range?
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6 votes

I wish you well with the general test! The radiolocation services in question are defined in CFR 47 §2.106: NG92 The band 1900-2000 kHz is also allocated on a primary basis to the maritime ...

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3 answers
8 votes
1k views
Estimating the efficiency of a shortened (loaded) antenna
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6 votes

I applaud you for diving into this topic. The notion of trap efficiency has been driven largely by antenna marketing FUD (Fear, Uncertainty, and Doubt) with implicative phrases such as "no lossy traps"...

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2 answers
5 votes
1k views
Yagi vs Parabolic Dish for 2.4GHz Campus Wifi from 1,800ft away?
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6 votes

You can make a first order approximation by using typical WiFi ranges in combination with two free space path loss calculations. 802.11b/g has a typical indoor range of 150 feet. By calculating the ...

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3 answers
5 votes
577 views
How can I determine/measure power rating of a DIY air capacitor?
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6 votes

Congratulations on your home brew project! It is great to see experimentation of this type. The two primary parameters for a capacitor are working voltage and ESR (effective series resistance), with ...

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2 answers
3 votes
200 views
Impedance matching: Why do components behave totally differently from theory?
6 votes

Firstly, at 900+ MHz, shorting out components to take antenna impedance measurements is not a good practice as the lead length can be a substantial portion of a wavelength. Stray inductance and ...

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3 answers
2 votes
285 views
Radio Range vs. Frequency
6 votes

This is an interesting question and while we may not be able to get to an exact answer, we can certainly explore the issues to consider. First we start by calculating a primitive link budget. The ...

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3 answers
3 votes
228 views
Non-life-threatening emergency in the US?
6 votes

Because the situation does not rise to the level of "imminent threat to life or property" you would not be permitted to "use any means neccessary" to carry out your communications. As a result, you ...

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1 answers
4 votes
191 views
Suspected Damage in Coax Cable
Accepted answer
6 votes

It appears to be typical moisture ingress. The joint between the coax and the connector is not inherently waterproof. A damaged jacket can also be the source of moisture ingress. Normally the ...

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2 answers
5 votes
795 views
What should I put in a "Go box", "Go bag", or "go kit" for emergency communications?
6 votes

If I wanted to build a mostly-portable-but-still-comprehensive kit to use in emergencies, either my own, or simulated ones through ARES or RACES, what should I put in the kit? If you are active in ...

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