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2
votes
1answer
3k views

What is the theoretical performance of a 2m 1/4 wave ground plane antenna when used at 70cm?

If I have a 2-meter 1/4 wave ground plane antenna with 1/4 wave radials bent down at approximately 45 degrees, what kind of performance in terms of SWR and gain pattern can I expect when using it on ...
1
vote
1answer
202 views

SDR software support for National Instruments USB-4431 ADC?

I have an opportunity to purchase one or more of these 24 bit, 4 channel, 102ksps USB ADCs, but before I do I want to understand how difficult they would be to use with existing SDR software. Are ...
6
votes
6answers
6k views

Why is antenna aperture a function of wavelength?

Wikipedia says: It can be shown that the aperture of a lossless isotropic antenna, which by definition has unity gain, is: $$ A_{\mathit{eff}} = \frac {\lambda^2}{4 \pi}$$ We also see this emerge as ...
4
votes
1answer
1k views

How would this RF field strength meter be calibrated?

I'm interested in an RF field strength meter that doesn't have to be lab quality, but still gives enough information about the RF field to know if an area exposed to RF is above the safety limits ...
14
votes
2answers
3k views

If I install a G5RV in my attic how could I be certain there are not harmful levels of RF in the shack, or my kids bedroom?

I assume that anyone who has a G5RV or G5RV junior in their attic has done so with ceramic spacers, and has zigzag or dog-leg installations, or otherwise has contorted the antenna to fit up there. My ...
3
votes
1answer
96 views

Transmitting Offset for sats

I found some pages on info for satellites, and I got different results. Some said to shift the transmit frequency as well as the receive, some said to keep the transmit the same, but shift the receive ...
8
votes
3answers
664 views

How would I calculate antenna gain?

The concept of antenna gain is pretty important for calculation of link budget and is something I've had contact with. I know that it tells me how focused the waves emitted by the antenna are and I ...
8
votes
1answer
2k views

Is the bandwidth of an LCR resonant circuit independent of the capacitance?

Is the bandwidth of an LCR resonant circuit independent of the capacitance, if the inductance and its series resistance are kept the same, and the Q is high? This question and the calculation ...
9
votes
1answer
2k views

How does SDR demodulation differ between wideband and narrowband FM?

What is the difference between software demodulation of an IQ signal between wideband FM and narrowband FM? Both seem to look at the 2nd difference in unwrapped phase angles of IQ samples.
7
votes
1answer
270 views

Regenerative receiver interference?

Can a regenerative shortwave receiver (especially an old vintage unshielded tube or transistor model) connected to a wire antenna generate HF interference? If so, what are some ways to prevent one ...
9
votes
3answers
11k views

Calculating Doppler Shift for satellites

If I know how fast a satellite is moving through space, how can I calculate the doppler shift for the pass?
10
votes
3answers
386 views

Do I need to actually lock up my station?

Per §97.103, one is responsible for the proper operation of one's station, which of course includes that no unlicensed person uses it to transmit. I have heard suggestions (no link handy, sorry) of ...
10
votes
2answers
832 views

What is meant by “poles” when discussing filters?

I was looking over the product page for the K3 (dreaming I know) and noticed that they offer a variety of crystal filters. Some are 5-pole and some are 8-pole, other than price, what is the ...
8
votes
2answers
409 views

Is steel or aluminum structurally a better material for catenaries?

I understand that steel is not a good material for antenna wire, but let's consider that I'm using the wire for purely structural support, or I am cladding it with copper to address the RF ...
10
votes
2answers
722 views

Scoring quality of Morse Code “fist”?

When learning, teaching oneself, or training a class in Morse Code sending using a hand key, how can acceptable quality be scored (other than the letters being correct terms of dot-dash sequence)? ...
6
votes
1answer
552 views

Can tropospheric scatter effect be used by 802.11 links?

What are the lowest EIRP and antenna gain requirements that make possible use of troposcatter at the distances of 100 to 150 kilometers assuming conventional WiFi (6 Mbit/s data rate with OFDM/BPSK ...
8
votes
3answers
158 views

Does LOTW have an interface document?

I want to be able to sign my own LOTW entries, without using the provided library (My application is pure Java). Is there a document that explains in enough detail how to do this, assuming of course ...
10
votes
1answer
1k views

What Part 97 rule allows unattended, automated transmissions, such as APRS weather stations and beacons?

What rule allows Amateur Operators to establish and operate remote, automated stations like APRS weather stations or beacons? Are there different rules specifically for beacons, or do they all fall ...
10
votes
3answers
983 views

What is the difference between FCC station and operator licenses?

I an studying for my technician class examination, and I came across this question: What may result when correspondence from the FCC is returned as undeliverable because the grantee failed to ...
4
votes
1answer
347 views

What is the average fade margin required for proper operation at 2.4 GHz?

I have two radios. Sensitivity is -84 dBm and transmitting EIRP is +30 dBm. How much distance should I expect? I want it to be somewhere near about 2-3 km. Is it possible?
2
votes
1answer
252 views

Maximum Input Wattage of MFJ-1717PL Antenna

I was wondering if anybody knew the maximum input wattage of the MFJ-1717PL Antenna. I was going to use this with the Yaesu FT-1900R mobile radio mounted in a Pelican case.
1
vote
2answers
124 views

ID station when testing an oscillator or transmitter into a dummy load?

Should one always identify ones station (say via CW keying) when building/testing an HF oscillator and/or anything that could amplify that oscillator, when powering the circuit on a breadboard and ...
4
votes
2answers
219 views

Which frequencies in a band should I use for antenna and radio testing?

Are there any frequencies (HF, 2m and 440) that are more suitable than others (assuming all are within those licensed to the operator) for testing new radios and/or antennas? I assume that one should ...
1
vote
2answers
587 views

What is the essential gear to have in a VHF/UHF FM base station? [closed]

I'm trying to assemble a VHF/UHF FM base-station at home. Assuming I have the following pieces of equipment: VHF/UHF FM transceiver power supply - 30 amps, no meters antenna that's resonant on 2m and ...
20
votes
10answers
93k views

What antenna on a BaoFeng UV-5R Pro will give me better reception? [closed]

I am happy with my BaoFeng UV-5R Pro but the local UHV VHF repeater and simplex reception is terrible, even for contacts less than 50 kilometers. I assume that it's because the rubber-ducky antenna on ...
11
votes
3answers
5k views

How is “clarifier” control helpful?

My radio-club recently got a Yaesu FT-225RD transceiver and I'm trying to digest its manual (available for download here). This is the first ham radio that I'm learning how to use, so I could be ...
10
votes
1answer
790 views

What does a lightning bolt symbol next to an antenna connector mean?

On the back of my Yaesu FT-897, next to each of the antenna connectors, there are lightning-bolt-ish symbols. What do these mean, and is there something I ought to be doing because of that? I have ...
8
votes
5answers
17k views

How far can a 2.4 GHz, 1 watt signal go in a rural area?

What's the approximate range achievable by a 2.4 GHz signal of 1 watt in semi-urban areas? I can see 2 km from our rooftop. Will a 2.4 GHz signal go that far, i.e. if I send WiFi signals from our ...
3
votes
1answer
893 views

How do I select a programmed memory scan on the Yaesu FT-897D?

The Yaesu FT-897D has a so-called “Programmable Memory Scan (PMS)” feature, which allows limiting scanning to a user-defined band by creating special paired memory entries which set the upper and ...
10
votes
2answers
264 views

What is the most common amateur identification practice for mobile US amateurs operating in Canada?

When a US Amateur operates in Canada, IT and Canadian regs permit some lattitude on their identification. I have read that some will prefix a "VE3" plus their own home callsign (Ontario, meaning I am ...
6
votes
2answers
2k views

Configuring an SDR for CW?

So I'm developing my own SDR software from scratch (I like to "own" the code). The channel between the RF-to-USB hardware and the software is 192kHz sample-rate IQ audio samples. The degrees of ...
8
votes
2answers
1k views

How to keep a disconnected coaxial connector weatherproof?

The advice I have seen on lightning safety is that if you don't have high-quality lightning protection (and associated grounding) installed on your feed line, it is advisable to, during a storm and ...
9
votes
3answers
162 views

How does contesting benefit Amateur Radio and its community?

Some use contesting for personal accomplishment, some out of pure enjoyment, others to gather awards, and some to hone their ability to work their craft. For instance, you may learn or improve your ...
5
votes
1answer
129 views

Is a gradual power-up recommended for non tube based radios?

It used to be that if you wanted to power up an old tube radio, you'd use a variac and gradually bring up the line voltage to avoid damage to the radio. Is this needed or suggested for transformer ...
9
votes
3answers
6k views

What is dBm and why is it used rather than watts?

Reading through an RF power amplifier datasheet, I found the sheet only referenced dBm output power, rather than watts. What is dBm? How do I convert it to watts? Why, or when, would you use dBm to ...
3
votes
2answers
405 views

How can I know over what distance or at what speed I can communicate? [closed]

Given some description of some parameters like: transmitter power frequency antenna location time of day how can I know over what distance communication is possible? Can I know the limits to these ...
34
votes
4answers
35k views

What's the difference between national calling frequency and national simplex calling frequency in the 2m and 70cm band plans published by ARRL?

On the 2 meter and 70 centimeter band plans published by the ARRL, what is the difference in intended use between the calling frequencies (144.200, 432.10 MHz) and the simplex calling frequencies (146....
2
votes
1answer
839 views

Two transmitters on same frequency

What are the repercussions of using 2 transmitters on same frequency? Tx are ~50 feet apart and the freq is 447.800 mhz.
3
votes
6answers
3k views

Smallest HF antenna for DX?

There seem to be reports of people trying to see how far an HF DX contact can be made using the tiniest transmit power (mW or even sub-mW QRP). But many of these contacts seem to be accomplished ...
1
vote
1answer
135 views

Easiest Matching Technique

What is the easiest way to match a 50 ohm coax with a 75 ohm antenna? I have a Yagi-Udi built with a 2 meter dipole, a reflector, and 3 directors.
2
votes
1answer
1k views

Kenwood TM241A making weird transmissions

I just got a used Kenwood tm241a. It was working fine on my friends antenna until I took it home and hooked it up to a used Larsen nla-mm antenna I bought at a ham-fest. It seemed to work fine on ...
6
votes
2answers
3k views

Preventing CW key clicks

What are "key clicks"? How much does the rise time or bandwidth of a CW signal need to be limited to prevent other QSOs on adjacent frequencies from being annoyed by "key clicks"? Is there a legal ...
2
votes
1answer
376 views

Where to find All Space Station Frequencies?

I am trying to make a list of all ISS downlink/uplink frequencies including ham bands and non-ham bands for a net I just started up, the Amateur Satellite net. Where can I find all of this? I can ...
1
vote
1answer
2k views

Patch Bowtie Antenna Design

I would appreciate it if someone could help me in designing a patch bowtie antenna. I would like to know the frequency and the bandwidth in terms of the length, angle and the length and width of the ...
9
votes
4answers
7k views

Operating proceedures: testing an HT against a repeater?

Assuming proper licensing for the frequency, what is the proper operating procedure to test whether an HT works and is within range of a (documented as open, 2M or 440) club repeater? Should one wait ...
9
votes
3answers
8k views

Bandwidth of a CW signal?

What is the RF bandwidth of a typical CW signal? How is the signal bandwidth affected by WPM and/or transmitter rise-time? What is the narrowest bandwidth that can still be copied by a human? Or ...
17
votes
3answers
10k views

What is the peak voltage at the tips of a dipole antenna?

What is the peak voltage present at the very end tips of half-wave dipole antenna in free space, and how might this peak voltage relate to transmitter type, transmitter power, RF frequency vs. antenna ...
9
votes
1answer
344 views

Why do SDR control apps have two frequency settings?

Why do many SDR control apps have two frequency settings, even when the app is designed or set up only for listening to or decoding one signal? Should the two SDR frequency controls be set ...
4
votes
2answers
2k views

Can an HF antenna be put inside a tree?

There are some trees around with branchy tops that seem wider than half of 10M, maybe even half of 20M, and above the nearby rooftops. Can a wire dipole or a vertical be mounted inside a tree? If so,...
3
votes
1answer
156 views

How to tell other party of scheduled QSO that frequency is in use?

It may happen that, at the start of a scheduled CW rag chew, the frequency is in use, but only one side can hear that it is in use. A cannot hear the existing QSO. B can hear the existing QSO. A ...

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