We’re rewarding the question askers & reputations are being recalculated! Read more.

# Tag Info

## Hot answers tagged testing

16

Mostly, they used RF Ammeters in series with the antenna. The first ones were hot-wire ammeters which were completely mechanical devices. One end of a thin nichrome wire (or other wire of sufficiently high resistance) inside the meter was coupled directly to the pointer shaft (often wrapped around it); the other end was anchored to the meter case. As the ...

12

GPS-based frequency standards @larsks answer rightly pointed at devices that use GPS to generate the 1-second pulsing. That's the correct way to go. Curiously, these modules only address the once-per-second accuracy issue, not the frequency standard issue, which GPS is indeed commonly used to solve: You'll find a lot of modules on the market that will ...

11

In No WWVB? No problem!, KB6NU points at two projects that show you how to build your own low-powered WWVB-replacement to keep your clocks in sync: μWWVB: A Tiny WWVB Station. This project uses an attiny44 microcontroller and a USGlobalSat EM-506 GPS module to simulate WWVB. One Component Radio Clock Time Transmitter: This project uses an attiny45 ...

10

I'm still a beginner in this area, so take this answer with a gran of salt. I've had a chance to see a ham test repeaters few days ago, so I'll describe what he did: First and the most obvious, make sure that the transmit and receive frequencies are correctly set on the radio. Go to frequency of interest and listen for a while. If there is a conversation ...

8

One way to tell is by its effects. Do you hear a garbled version of yourself in nearby speakers when you transmit SSB? Do GFCI outlets pop even though no one is being electrocuted? Does handling the transmission line give you RF burns when transmitting, or change what you hear when receiving? If you had these problems and now you don't, you must have been ...

7

WWV and WWVH broadcast time and frequency reference information continuously, using AM on 2.5, 5, 10, 15 and 20 MHz, so you should be able to pick up all of them using your receiver, given an adequate antenna. At my location (San Francisco Bay Area) with lousy equipment, these signals are only slightly stronger than shortwave broadcast stations, but more ...

6

You've nailed this! So, I'm sometimes involved in these kinds of investigations. It all gets easier when you have control over the transmitter – when some spurs disappear as soon as you turn it off, but others remain, you've ruled out the transmitter as the source of these. Then, digital receivers typically, as you notice, have different sources of spurs. ...

4

Part 15 sets limits on unlicensed RF emissions. The limits vary by frequency, the type of device, the nature of the emissions, and so on. It's a pretty huge document and you need a lawyer and an EMC engineer to approach it. However, you can get the intent of it from this blurb that is printed on just about every piece of consumer electronics sold in the US: ...

4

It's not necessary to turn it off while it is not connected. Zero dBm is a power level of only 1 milliwatt, and no device will be damaged by that power level. If it were, the manual would have said so.

3

You're on the right track with the first items in your list. Assuming that you have a wattmeter and a dummy load that both match the impedance of the coax, it's a simple matter to measure the loss. Measure the power with the wattmeter at the source, and then measure it again at the load. The difference between the two wattmeter readings is your loss. N_{...

3

Don't forget about CHU (and here is the official site) which is the Canadian equivalent to WWV. It's at lower power and it's not as well-located geographically (it's located near Ottawa), but it's receivable in most of the eastern US and increasingly less well as you head west. Here in VE5-land (Saskatchewan) I certainly receive it sometimes, but I also ...

3

If you use a dummy load on the transmitter, it is likely that there will be enough power and enough leakage from either the load or the transmitter itself to be easily received. This is quite likely for the power levels and shielding quality in amateur equipment (homebrew or commercial). If you had a non-leaky or very low-power transmitter (e.g. the various ...

3

Depending on what you're testing, The safest bet is through a SWR meter into a 50 OHM dummy load, or an attenuator into a spectrum analyzer.

3

Depends on your receiver sensitivity and antenna location. I've seen some many-decades-old portable shortwave radios pick up at least one WWV frequency using their simple built-in half-meter to meter long metal whip antenna.

3

Either of those choices are good, as long as you identify your transmission. Many repeaters transmit a courtesy tone after repeating their input in order to signal end of transmission. For those repeaters, you can TX your call sign and then listen for the courtesy tone on the repeater output. This will let you know if you're hitting the repeater, but not ...

3

No license is required to build broadcast transmitters in the United States. To get approval to sell your transmitters in the US, you would most likely need FCC authorization. The process to get that authorization is covered by 47 CFR part 2, and is summarized on this FCC web page. I'll summarize further: Determine FCC Rules that Apply. Determine if ...

3

If your nephew damaged the Baofeng GT-3TP Mark III, the damage is likely to the transmitting circuits of the radio, and not to the receive side. I don't have that model of Baofeng, but I do have a different model, which is notorious for having difficult-to-adjust squelch. On several channels I can't get the squelch to stop the radio from playing static. ...

2

Both of your procedures are workable, but be sure to "IDENTIFY" with your call sign when testing or talking to someone (see part 97). A couple of thing's to keep in mind. 1. Just because you can hear the repeater doe's not mean that it can hear you, an HT's antenna is not an ideal antenna for transmitting (some are not much more than an "AIR COOLED DUMMY ...

2

Another great way to listen for signals, especially stronger ones, other than WWV and WWVH, is to find some active AM broadcast stations within the 1.8 to 30MHz range. Head over to this site http://www.short-wave.info/, and use the top most form, selecting any station, and preferred language, make sure NOW is checked, and hit GO! YOu can pretty much tune ...

2

You can always download the EchoLink software and see if your repeater is listed, then find someone who will listen for you while you're mobile. It's available for cellphones but I'm not sure how well it works on data rather then wifi since I don't tend to use it when I'm mobile with a HT anyway. If you use the same repeater on a regular basis, it might be ...

2

From http://urgentcomm.com/mag/radio_demystifying_rf_attenuators: ...[A]ttenuators are symmetrical, provided the input and output impedances are the same. In applications where attenuators are used as impedance-matching devices, they are not symmetrical. A typical attenuator circuit will be a purely resistive network - for example, this pi-network ...

2

From Elecraft support: "You do not have to connect a load to the XG3. A signal generator is different from a transmitter."

2

A cursory physical inspection and an SWR sweep are usually sufficient. Blatant physical damage, like internal shorts or breaks in continuity, will be found by the SWR sweep. So in your physical inspection you're looking for things which might not impact the SWR, like outer insulation that's cut or damaged which may eventually lead to water ingress. You ...

2

Here's a paper from the IEEE antennas and propagation society, describing a channel model and the experimental verification thereof. Noise will be another whole subject on its own, but the IEEE APS will be a good place to start. Experimental Confirmation of an HF Channel Model The abstract describes the model quite well. Unfortunately to read the whole ...

2

As implied in other comments and answers, this sounds like it would be legal to do (we’re all assuming you’re in the USA, given the fcc tag), since all you are doing is building equipment. However, if you want to sell the equipment once you have built it, that is going to be more difficult. I would ask you the question - why broadcast equipment ...

2

The proper mix of ferrite for your frequency of interest in a properly-designed common-mode current choke is your friend. Look no further than Jim Brown's latest PDF on this subject at k9yc.com There is no better source of information anywhere else. RFI, Ferrites, and Common Mode Chokes For Hams Most recent update April 2019. This tutorial is ...

1

In addition to the above tests, and if: the coax is of some reputable brand and has type markings on the jacket, you have access to a LCR meter, the cables are of sufficient length, you might want to check the capacitance and compare to the capacitance in the datasheet. This is usually marked as F per meter/100 meter/feet/... Calculate the expected ...

1

I have been a ham for 58 years. I used an incandescent light bulb for transmit and a fluorescent tube for antenna tuning. Later, I could afford a field strength meter. I have also used Lecher wires for UHF. Technical details? Go with the glow.

1

Harmonic spurs as detected in a receiver could be generated in the transmitter, the receiver, or the transmission lines or antennas in between. Usually of course the antennas and transmission lines aren't the problem, which leaves the transmitter and receiver as potential culprits. The most accurate way to test a transmitter is to connect it to a ...

1

I believe you have described the situation very well. It is caused by the generation of impure signals, usually in the transmitter. Other causes could include using a transmitting antenna that resonates at or near a harmonic, such as using 40 meters on a dipole and finding harmonics around the 15 meter band. It is rare for harmonics to be caused by the ...

Only top voted, non community-wiki answers of a minimum length are eligible