tomnexus
  • Member for 7 years, 1 month
  • Last seen this week
  • Vancouver, BC, Canada
Does iron ore in the ground affect my signal?
3 votes

Probably not much effect from iron in the ground. HF communications are very sensitive to the ionosphere and other natural effects. Predictions are difficult, and only give a probability, never a ...

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Copper Wire connecting log periodic elements to boom
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3 votes

The wire is probably tinned copper, not aluminium, but the material is not critical to the function of the antenna. You could replace it with any other wire of similar thickness, but keep the length ...

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Choosing capacitor for high-pass filter with cutoff of about 160 MHz
3 votes

Mini-circuits is the place for filters and other RF gadgetry. See http://www.minicircuits.com/products/filters_coax_high.shtml for their high pasd catalogue. For example, the BHP-250+ BNC ...

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Best mobile antenna for the mountains
3 votes

If very high angle coverage is important to you, go for a 1/4 wave monopole antenna, mounted in the middle of the roof. A magnetic mount should be fine. A 5/8 wave vertical antenna has more gain than ...

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How is impedance matching related to balance and common-mode currents?
Accepted answer
3 votes

The two are separate figures, so one does not imply the other. A good match doesn't imply no common mode currents, and no common-mode current does not imply a good match. They are somewhat connected -...

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GS cards in NEC decks
2 votes

You're right the documents are a bit thin here. Going through the source code would be one way. I tried this out quickly in NEC, as it helpfully prints out the whole geometry in the OUT file. The ...

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Reduction in transceiver power output into high SWR
2 votes

My Icom T81 handheld has a detailed circuit diagram and description in the service manual which can be found online (well done Icom!). It shows how the handheld will fold back power when the SWR is ...

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How should I think about "extra" impedances inserted within/across a transmission line?
2 votes

To solve the first circuit: Divide the transmission line into two lines, one on the left, one on the right. Zoom in to the centre portion. When you are in a small ($\ll\lambda$) region, the normal ...

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Ferrite unun transformer to match antenna resistance loads of <50Ω?
Accepted answer
2 votes

The gold standard books on baluns are by Jerry Sevick. They all seem to be out of print and expensive on ebay, but you may find one, or someone willing to summarise the relevant pages of their copy. ...

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Why so high values of noise température of a spectrum analyser?
2 votes

A noise figure of 22 dB is pretty normal for a spectrum analyser. Expressed as a noise temperature it looks like a large number, but there are many equations which yield unexpected and large numbers. ...

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Is a resonant antenna inherently more efficient because it couples to free space more efficiently?
2 votes

Not really answering the question but requesting more clarity in terms. From the IEEE definition of standard terms for antennas: I redraw the diagram of power flow in an antenna, (ignoring the ...

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1:4 Guanella unun current balun
2 votes

The voltage doubles because the two coaxial cables are connected in parallel on the input side, but in series on the right hand side. In the diagram, there shouldn't be a little i in the middle of the ...

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What happens to the signal level if the antenna has high SWR?
2 votes

I think you've answered your own question. In case a, with an antenna with 2:1 SWR and an otherwise lossless system, 11% of the power will be reflected and re-radiated by the antenna, so 89% makes it ...

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Do VNA (nano) suffer the same effect of coax length to swr, as swr meters do?
2 votes

The NanoVNA, and any VNA, when calibrated with open, short and load standards, can correctly measure through an arbitrary two port network, like a lossy, imperfect cable. Any combination of ...

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Total radiation pattern in antenna arrays
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2 votes

The first is still correct, and can be evaluated at any position. The second is true only at broadside, when $\theta=0$. In your attempts, do you find that $\vec{E}_{total}$ is the same in all ...

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How much of the 136 - 174 mhz spectrum is actually in use?
2 votes

In my experience the parts allocated to PMR are extremely busy, it's the most popular band for walkie talkies and car radios, best compromise between antenna length (60 MHz is quite bulky) and path ...

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Repeater design using round robin transmitters to increase duty cycle?
2 votes

It is likely that you can operate the TK-890H at 100% duty with better cooling. This would be a lot less work than the scheme you propose. The Kenwood TK-890H has no fan - a good thing for mobile use, ...

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The HPBW of a helical antenna
2 votes

Kraus says $${52}\over{{C\over\lambda} \sqrt{n{S\over\lambda}}} $$ Which is your second equation. Be aware that this only holds for a narrow range of diameters and spacings: $0.8<{C\over{\lambda}} &...

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What are the properties of the radiation of a magnetron?
2 votes

I once wondered if a microwave oven magnetron might make a good transmitter, for CW for EME. I took a spectrum analyser and antenna to the kitchen and microwaved a glass of water, and I saw... The ...

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Glass Block Pass Through
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2 votes

You could use a short jumper of a thin cable, pushed through a hole drilled in the grout between the blocks, or next to them in the plaster. A 141-size cable is 3.6 mm in diameter, and the base model ...

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Working satellite on 2 meters, at what arc distance to sun (center) will noise floor be problematic to a disruption of a communication path?
Accepted answer
2 votes

It depends on the gain of your receive antenna, your system noise temperature, and how much link margin you had in the first place. The moonbounce (EME) community use Sun Noise as a measure of their ...

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Modelling a folded dipole
2 votes

Good simulation work - your results look pretty realistic. A note about patterns - when you talk about Azimuth and Elevation patterns, with the antenna lying on its side, it's not completely clear ...

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Why do watches with GPS receivers have an "airplane mode"?
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2 votes

Some years ago when electronics on planes were still a big deal, I remember GPS receivers, portable CD players and radio receivers being singled out as Not Allowed. This could be because radio ...

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Is there a suitable alternative to using a metal pole to mount a vertical yagi apart from wood and fiber glass?
Accepted answer
2 votes

You could use a metal pole broken up with a few insulators. One at the boom itself, and one near the ends of the elements, perhaps one more 2.5 m below the antenna, or at the base of the pole. Don't ...

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resonance vs resonator in antenna
2 votes

The word Resonator is used to mean the loading coil in a short vertical whip antenna, that makes it resonate at the frequency of interest. The Hustler brand, for example, calls its coils resonators. ...

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Feeding a folded dipole
2 votes

Running the coax through the folded dipole is one good way of feeding it. Advantages over the more traditional 1/2 wave coax balun: No balun required - unbalanced coax all the way to the feedpoint, ...

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Passively reducing ground loss?
2 votes

Random long wires - probably will help. Especially if they're aligned with the dipole above them. Space blankets might not have a thick enough metal layer to be effective at HF, (though I know ...

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How to splice RG-174 coax?
2 votes

At HF there are almost no limits on how bad your splice can be, as long as: there's no short circuit braid is connected to braid and inner to inner You could even use a "chocolate block" connector :)...

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Determining whether signal meets the 12 dB SINAD voltage
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2 votes

The specification means $0.15\ \mu\text{V}$ at the input terminals of the receiver, so this voltage across a $50\ \Omega$ load. Power in a resistor can be calculated with $P={V^2}/{R}$ so $0.15\text{ ...

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Cell tower identifier antenna isolator cannon
2 votes

What you are describing is a directional antenna for your phone. You can do this by placing the phone Inside the antenna, or by connecting the antenna to the phone. The pipe you describe is actually ...

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