13 votes
Accepted

How do I troubleshoot a Baofeng UV-5R that won't receive?

I did a bit more reading, and it seems that the new version of the firmware meant I needed to use a different chirp profile. The solution that worked for me was to find a factory image from a radio ...
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  • 351
12 votes
Accepted

Why do I only hear broadcasts from 150 kHz to 29.999 MHz?

It doesn't sound like you're doing anything wrong. Most likely, you are simply only hearing strong stations; broadcasters put much more power into their transmissions than amateurs are legally allowed ...
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  • 22.9k
6 votes

Repairing a Tecsun PL-660

I signed up here just to reply to this great (the only one I could find on the internet) question/experience that helped me with an identical problem. I was so close to giving up when I read this ...
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6 votes
Accepted

How to reduce VFO sensitivity to the hand capacitance?

As mentioned in the comment by henryflower, make sure that the shaft (and thus the frame) of the variable capacitor are grounded. You need to use rubber mounting grommets around the screws which bolt ...
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  • 3,393
5 votes
Accepted

Noise & shielding, SDR Dongle

While the other answer is quite detailed, this one is much shorter and specific: I purchased and installed an aluminum RF shield for the dongle. The noise floor is significantly lower as a result! ...
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  • 789
5 votes

Noise & shielding, SDR Dongle

“Sensitivity” isn't all that well-defined. Insofar as it is, you might as well just think in terms of noise, because there is always a noise floor and it's always what determines the weakest signal ...
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  • 22.9k
5 votes

Repairing a Tecsun PL-660

Tecsun is very similar to Baofeng in that anybody selling them expects a certain number of DOAs and other failures. They already know that QA on those rigs is directly reflected in the price. In the ...
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  • 2,021
5 votes

Faulty MFJ-259 - meter hits end stop on power up

No power light could just be a burned out bulb or dead LED (I have a 259B...don't recall if the power button ever lit up). If you don't have anything connected to the antenna connector, then it's ...
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  • 669
4 votes

What causes my direct conversion 80m receiver to receive AM broadcasts?

It might be harmonics of the oscillator, as you suppose, but it also might be that any mixer doesn't only produce the difference frequency of its two inputs ($|f_\text{RF}-f_\text{local oscillator}|$, ...
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4 votes

Squelch never seems to "open the gate" on Wouxun KG-UV9D

I'm not familiar with the exact behavior of that model of radio (and the manual was not very helpful), but a possible explanation in general is that you have CTCSS/DCS squelch enabled, and the ...
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  • 22.9k
4 votes

The amplifier does not work for hack rf one

HackRF has three amplifiers in the receive section. The first is a low noise amplifier (LNA) with fixed gain of 14 dB. The second is an Intermediate Frequency (IF) LNA with gain that varies from 0 to ...
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4 votes
Accepted

BF-F8HP radios do not receive on 2m unless menu is open

The most likely scenario is that all four radios have the same problem. It's possible that the problem is a manufacturing defect, but that's unlikely, especially if you got the radios from different ...
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  • 8,922
4 votes

How to reduce VFO sensitivity to the hand capacitance?

Circuit looks OK. Note that the highest impedance point in this circuit is near the box open end. RF voltage here is highest in this oscillator, and is susceptible to coupling out the top. A shield ...
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  • 536
3 votes

Reception for FM stations is offset, but AM stations aren't

While I wouldn't rule out old capacitors or whatnot, if it's anything like some of the radios I've played with through the years, the solution might be a simple mechanical one: can you open it up ...
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3 votes
Accepted

Connecting a Katsumi Elekey EK-150 to my transceiver

I took it apart and found a transistor that had been blown apart, pictured below (the black one with its metal innards showing), likely from a scenario described by @rclocher3. This is the NPN ...
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3 votes
Accepted

The amplifier does not work for hack rf one

There are three receive gain stages in the HackRF one. Two of them are on the MAX2837 chip (the ones controlled by "LNA gain" and "VGA gain"), and the third is the MGA81563 preamp, ...
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  • 8,833
3 votes

Why does my transmitter spam the SDR waterfall with this strange pattern?

This is not strange at all. But depends on the transmitter, transmit power level, receiver, and the how close the two antenna's are situated. Electronic circuits are linear only over a certain finite ...
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  • 12.4k
2 votes

Why do I only hear broadcasts from 150 kHz to 29.999 MHz?

If your antenna is hanging down the side of the building that may be your very problem! Most DXing on HF is done on horizontal antennas. If yours is vertical then you be getting only a sliver sized ...
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  • 21
2 votes

Baofeng UV82-HX charger problem

Try reducing the power and see if that helps. If it lets you transmit longer then the battery needs to be replaced. If it shuts off right away at low power then you may have a bad final or other ...
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2 votes

Signal generator giving DC output?

Multimeters are generally used to measure AC volts at line frequencies, i.e. 50/60 Hz, and yours is almost certainly not accurate at 1 GHz. Similarly your multimeter's DC volts setting is designed to ...
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  • 8,922
2 votes

Issue with Icom R-71A

I have just joined so have to answer instead of commenting (not enough reputation yet). I have one of these receivers and know a little about them (I have to say it performs excellently and is very ...
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  • 311
2 votes

Yaesu G-5400B rotator controller problem

I had the same issue. I adjust the Azimuth every day, then sometimes it fails between 15-20 degrees. Then I replaced the regulator with a new one. Now it is ok.
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2 votes
Accepted

Kenwood TH-D72 Freeze on Splash Screen

I assume you have extensively bench tested the kit and have not found any problems. Having several years of experience with high altitude radios in the Alps, I would suspect that you are getting ...
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  • 18.1k
2 votes

What causes my direct conversion 80m receiver to receive AM broadcasts?

Everything works very well, but on some frequencies I hear loud AM broadcast stations. I think this is caused by harmonics from the VFO, but I am not sure. What you're possibly hearing is ...
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2 votes
Accepted

Yaesu FT-991A: FM and C4FM modes don't work on HF bands

After reverting MARS/CAP mod everything works as expected. I don't know whether the problem was caused by the mod per se or maybe just one of FCC cables was a little bit misplaced when the mod was ...
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2 votes

Yaesu FT-817 Won't transmit Dig, SSB or CW

Menu option for ssb filter (38?) should be "off", if no filter.
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2 votes

Kenwood TS 520 S Meter accidentally run without an antenna connected

Unless you tried to transmit without an antenna, it should be fine. If the radio is in receive mode without an antenna, it won't hurt it. But if you transmit without an antenna, especially at high ...
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  • 4,203
2 votes

Connecting a Katsumi Elekey EK-150 to my transceiver

In the keyer, PNP transistor Q4 should be on when the keyer is supposed to be keyed. I assume that the transceiver's key jack goes to a CMOS high-impedance input and has a pull-up resistor, and that ...
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  • 8,922

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