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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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 ...
Kevin Reid AG6YO's user avatar
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15 votes
3 answers
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 ...
Mike Waters's user avatar
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10 votes
5 answers
2k 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? ...
Mike Waters's user avatar
  • 7,958
10 votes
4 answers
11k 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 ...
hotpaw2's user avatar
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7 votes
2 answers
955 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 ...
progrmr's user avatar
  • 342
7 votes
1 answer
403 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 ...
hotpaw2's user avatar
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6 votes
4 answers
1k 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 ...
Ben Short's user avatar
  • 163
6 votes
3 answers
3k 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 ...
hotpaw2's user avatar
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6 votes
2 answers
1k views

Can an oscilloscope be used as an RF voltmeter?

I just recently acquired a slightly functional Icom IC-735 HF radio, and am trying to resurrect it. The service manual outlines procedures that specify the use of an RF Voltmeter, which I do not own. ...
user avatar
6 votes
1 answer
374 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 ...
Moses Browne Mwakyanjala's user avatar
5 votes
3 answers
5k 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 ...
Adam Davis's user avatar
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5 votes
2 answers
261 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 ...
Paul's user avatar
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5 votes
1 answer
764 views

Using a Return Loss Bridge and Nano VNA to measure amplifier characteristics

One of the difficulties of measuring active devices like LNA and IF amplifiers with the Nano VNA is the care needed to avoid over-driving the amplifier input and, more importantly perhaps, to avoid ...
Buck8pe's user avatar
  • 989
4 votes
2 answers
794 views

VNA basics, antenna coax cable

Recently purchased my first VNA (Nano VNA) and I'm trying to learn the basics. I have a 150MHz 1/4 wave whip antenna that I need to install on a large metal object so I was hoping to use a VNA to help ...
P_J's user avatar
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4 votes
3 answers
155 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 ...
Synaps3's user avatar
  • 425
4 votes
1 answer
154 views

How do businesses develop and test amateur radio products in the US if you cannot be paid for amateur radio use?

Certainly there are companies in the US (like Kenwood) that develop HAM products that transmit. For development and QA they would likely need to test the product outside of a Faraday cage. How can ...
KJ7LNW's user avatar
  • 723
4 votes
2 answers
474 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 ...
Kenn Sebesta's user avatar
4 votes
2 answers
501 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 ...
hotpaw2's user avatar
  • 13.3k
3 votes
2 answers
149 views

What safety procedures should be followed when developing and testing a high power amp?

I'm designing a 300W power amplifier using the MRF300AN from NXP targeting a center frequency of 146 MHz. Obviously I need to keep my fingers out of it and test into a dummy load, but generally ...
KJ7LNW's user avatar
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3 votes
1 answer
153 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 ...
pgibbons's user avatar
  • 444
3 votes
2 answers
269 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 "...
user103218's user avatar
3 votes
1 answer
130 views

Why is my experiment to produce 3rd order harmonics by saturating a receiver not working

I've been trying to devise an experiment to produce a third order harmonic in radio receiver that's been saturated, but I'm not seeing the expected results. My understanding of the theory is that when ...
Frank's user avatar
  • 339
3 votes
3 answers
306 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 ...
hotpaw2's user avatar
  • 13.3k
3 votes
1 answer
177 views

Testing old coax cable

I have a situation similar to this: Testing for 'Bad' Coax . In addition to checking for DC continuity or shorts, here was my test method: My 50Ω dummy load (Elecraft DL1) has a diode and ...
Duston's user avatar
  • 939
3 votes
1 answer
165 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 ...
Aleksander Alekseev - R2AUK's user avatar
3 votes
1 answer
170 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 ...
hotpaw2's user avatar
  • 13.3k
3 votes
1 answer
244 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 ...
Kevin Reid AG6YO's user avatar
  • 24.5k
2 votes
2 answers
402 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 radios back-to-back without going over the air?
Dave M's user avatar
  • 125
2 votes
2 answers
223 views

What simple methods are available to test a homebrew SSB transceiver on transmit?

Overview Before putting my recently completed homebrew single conversion 20m mono-bander on the air, I borrowed another radio to listen to the transmission and make sure everything was OK. It turns ...
Buck8pe's user avatar
  • 989
2 votes
1 answer
382 views

What is a "feed-through load" and how does it work?

While browsing some miscellaneous RF test equipment supplies I stumbled across a two-port component sold as a "feed-thru load". Take for example the Pasternak PE6026 (datasheet), which looks ...
natevw - AF7TB's user avatar
2 votes
2 answers
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. ...
Adam Davis's user avatar
  • 12.1k
1 vote
2 answers
499 views

Is there a proper way to connect multiple radios via coaxial cable so they can be tested without going over the air?

Let me state up front that I am not an RF engineer, but I do have a EE background. I'm working with a group that has a collection of radios, VHF and UHF (military) that is licensed to use a VHF and ...
AnAnonymousParty's user avatar
1 vote
2 answers
179 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 ...
hotpaw2's user avatar
  • 13.3k
1 vote
1 answer
57 views

How to test real-world performance of a wifi and LTE IoT device

We're developing a product that communicates over wifi and LTE. I'm putting together a test plan for determining that these work, but also what sort of conditions we can expect them to work in. The ...
askvictor's user avatar
  • 191
1 vote
1 answer
470 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. ...
Loren Tedford KC9ZHV's user avatar
0 votes
2 answers
110 views

universal 433 MHz test lamp (receiver)

I was wondering whether quick testing of various commercial ISM band transmitters for operation can be accomplished with some sort of off the shelf universal receiver which only turns on a led upon ...
kellogs's user avatar
  • 203
0 votes
1 answer
303 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 ...
AndreaF's user avatar
  • 103
0 votes
1 answer
68 views

How do you protect your radio when testing custom RF circuits at ~100W?

We are designing a UHF/VHF diplexer for a satcom project and targeting support for 100W. Our radio can transmit near 100W but of course we want to protect it in case there is a failure of some kind. ...
KJ7LNW's user avatar
  • 723
0 votes
1 answer
68 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 ...
Matthew Wang's user avatar