Questions tagged [testing]

Techniques for testing the functionality of radios and other equipment. Do not use this tag for license examinations; use [license] instead.

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19
votes
2answers
9k views

How to detect common-mode currents or “RF in the shack”?

Let's say we already know that if your antenna is not suitably constructed or connected then you can get current on the shield of your coaxial feed line which will flow through the shielding/grounding ...
14
votes
3answers
2k views

WWV, WWVH, and WWVL may be shut down. Are there any alternatives?

The US government is proposing to shut down the NIST standard time and frequency stations WWV, WWVH, and WWVB in Colorado and Hawaii. If that actually happens, are there any free or inexpensive ...
10
votes
5answers
843 views

How did hams manage to tune their antennas before VSWR meters?

In the early 20th century --back when the hobby was still new-- before VSWR meters and antenna analyzers were invented, how did radio operators know whether they were tuned for maximum power out? ...
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 ...
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 ...
6
votes
2answers
136 views

What does an antenna analyzer tell me about these coaxial cables?

Note: more measurements added after graphs below I recently acquired a RigExpert antenna analyzer and I am trying to learn how to use it to test cables. I took two cables to start with to try and ...
6
votes
1answer
194 views

SNR measurement for a BPSK/QPSK signal

I have created a software (gnuradio) that performs modulation/demodulation and supports a number of modulation schemes and error correcting codes. I'm in the process of evaluating the BER vs SNR for ...
5
votes
3answers
3k views

Are there any good, consistently receivable signals in the US for HF receiver testing?

Having built my first HF receiver, I'd like to know if I'll need to search around for transmissions that happen to be occurring, or if there are reasonably strong signals I can count on being present ...
5
votes
4answers
513 views

Testing for 'Bad' Coax

I have a lot of 'donated' coax that has been given to me with unknown provenance. I'm wondering what things I can do that can determine whether I keep it or send to the tip? Some of the things I have ...
5
votes
3answers
1k views

Cause of harmonic spurs?

Harmonic spurs (harmonics of the transmitter frequency, as seen by a wide-band receiver or SDR) in the RF spectrum might be caused by an imperfectly sinusoidal or badly filtered transmitter carrier ...
5
votes
2answers
219 views

Can I have a signal generator on while it's not connected?

The unit in question is an Elecraft XG3 test signal generator. It puts out anywhere from -107 dBm to 0 dBm. Is it safe to have these signal generators on and transmitting while not connected to ...
4
votes
3answers
108 views

How can I get a license to build broadcast transmitters?

I am in the United States. The title pretty much says it all. I am really into to building transmitters. It's even more fun for me than using them. I really have a lot of skills and would like to ...
4
votes
2answers
216 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 ...
3
votes
1answer
60 views

Is this “floating” output single-ended or differential and against GND or VCC?

I'm looking at a simple FM transmitter output (see picture). It is from the collector of a transistor and it goes through a DC blocking capacitor before the antenna would be connected. The entire ...
3
votes
2answers
163 views

Supershield or Superscreen coax: Does it exist? What is its common name?

I'm sure this seems like a Google question, but I've BTDT and come up empty. The problem I'm trying to solve is to obtain cables that are as "leak proof" as possible. Tried Pasternak "...
3
votes
3answers
106 views

Antenna testing, minimizing feed-line radiation?

Assume that one does not have access to a multi-million-dollar RF anechoic chamber. When testing an amateur radio HF or VHF antenna, how would one absolutely minimize the amount of any RF radiation ...
3
votes
1answer
85 views

How to fix SignaLink non-linearity problem?

I decided to check the linearity of my Yaesu FT-891 signal using an RF sampler and an oscilloscope. To generate two-tone (1550 Hz, 2150 Hz) signal I used Audacity. To connect the transceiver to the PC ...
3
votes
1answer
118 views

RF fading channel model?

What statistical or other descriptions exist regarding modeling of an HF-band RF fading channel? This is allow making (as in code my own software) lots of simulated test input signals for an SDR ...
3
votes
1answer
195 views

Would a switched RF attenuator be (a)symmetric?

I picked up this 0-80 dB switched RF attenuator at a flea market, with no part number or other useful markings other than the knob settings. I've tested it and confirmed that it works, but there's one ...
2
votes
2answers
62 views

Building a low-power simple RF frequency (433MHz or 900MHz (but not both)) detector effective at 5m with a 10mW signal

I am looking for a simple schematic for building an effective RF detector which can trigger a GPIO. The goal is to (passively?) detect a 10 mW RF signal (10% duty cycle) and have that raise voltage on ...
2
votes
2answers
2k views

Simplest, smallest antenna for tuning WWV, WWVH?

I'd like to perform some simple receiver testing and calibration (mostly for frequency variance, not signal strength) and have been told WWV/WWVH transmissions can be found throughout most of the US. ...
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 ...
1
vote
1answer
126 views

Retuning 2m Duplexers (Q2330E) with Spectrum Analyzer and Tracking Generator

Yesterday I was trying to tune up the duplexers one can at a time as listed in this Sinclair Youtube Video. After tuning them my receive is awful and my transmit is somewhat not what it used to be. ...
0
votes
2answers
114 views

Testing Radios Back-to-Back without Going Over-the-Air

Is there a device, something like a dummy load, that will allow one to test two radio's back-to-back without going over the air?
0
votes
1answer
102 views

How can I determine the possible damages of transmission with detached antenna in portable ham radios?

Premise: I had a Baofeng GT-3 TP Mark III 8W stored and never used, this morning my nephew has found It and He tried to "play with It" transmitting at maximum power(8 Watt) despite antenna wasn't ...
0
votes
1answer
58 views

Can you measure how much radials you are lacking for HF vertical?

I have tried mount ham sticks on SUV and a convertible use trunk lid mount, especially on 40m on the convertible I notice the SWR changes from opening the door and close the door. Now I am quite ...