8

Receivers and transmitters are still separated today, they are just in the same box. There is still a T/R switch too, integrated in the box. In many radios, it's a relay, same as they have been for decades. Relays are hard to beat for isolation and maximum power ratings. Their downside is relatively slow speed, which prevents really good QSK operation. They ...


4

All OK. Pitfall for 14 MHz RX and 9 MHz crystal filter is choice of oscillator frequency. 5 MHz is possible but a bad choice, because the harmonics of the oscillator give unwanted spurious reception. By the way: I did identical things. See pictures. In my opinion there is no preference for LSB or USB based on such passband characteristics.


4

I don't know what the specific devices you're referring to do, but a couple of things are all technically possible without great effort: the ADC that is used to calculate the waterfall in receive-only mode is still connected to the antenna, maybe with additional physical attenuation (which you could trivially reverse in digital domain by multiplication with ...


4

ALC, in general, stands as an abbreviation for Automatic Level Control, which is a class of circuits designed to back-feed information about the output signal to an amplifier. The goal is to change the parameters of the amplifier so that a clean output that remains within certain parameters is attained. In normal HF transceivers, such a circuit will most ...


3

Using an example from Crystal Ladder Filters for All, a crystal filter response might look like this: Indeed, this filter might "prefer" LSB, because that would place the carrier near the right side of the passband which has a steeper attenuation. That would mean you'd design your IF like this: When the IF is subsequently heterodyned down to ...


3

The radio has multiple antenna ports and full-duplex capability, and the operator has selected different antennas for transmit and receive. Or, The radio just displays the transmit spectrum on the waterfall, and it isn't coming from the antenna at all. I've used radios with both of those options, so they're both definite possibilities.


3

After a little bit of searching I discovered that this topology is called QER filter, where QER stands for Quasi-EquiRipple. This topology is attributed to Dr. Dave Gordon-Smith, G3UUR, who is also well-known for inventing a popular method (the G3UUR method) of measuring crystals. Apparently it was first described in The QRP Quarterly, Spring 2010 under the ...


2

As far as your question regards components: T/R switching is usually done with either relays, reed relays (often faster than other types of relays; also more quiet), or PIN diodes (even more quiet and faster). Where high voltages and/or currents are present (and fast switching is needed) vacuum relays are also used. Circuitry may involve circuits that ensure ...


2

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


2

As both previous answers mention, the T/R switch functionality is just something that moved into existing boxes, not something that disappeared. The only ways to make that functionalies disappear would be making the receive end tolerant of the transmit power and still a sensitive receiver (practically impossible at any significant power – the difference ...


2

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 power, the high SWR could damage the final amplifier in the radio.


2

Looks like it's just a fancy memory feature to let you quickly switch to a preset frequency and operating mode. https://www.k0pir.us/icom-band-stacking-register-and-memo-pad/ and https://www.manualslib.com/manual/965457/Icom-Ic-7600.html?page=38 . As the second URL mentions, it would be useful if you operate multiple modes in one band, so you can quickly ...


2

ALC limits the the input power to the power amplifier (PA). Overdriving the PA would be bad: it might overheat, or exceed the voltage or current ratings of the components, eventually, or sometimes immediately, damaging the PA. Or it might just cause a lot of distortion and spurious emissions. If the radio has adjustable output power, often this controls the ...


1

I recommend you go to the Eurocontrol website. Have a look for Asterix category 048. This is the definition for the Mode A Octal code for aircraft transponder, Mode C altitude, Mode S more data including callsign ICAO 24 bit identify code and lots more. There will lots of information about the radar calling and aircraft response exchanges as well. Former air ...


1

I havent looked into the mechanics too deep, but FlexRadio has a full-duplex feature for those models with 2 SCUs (spectral capture units) in the radio. Each SCU goes off to a different antenna, and as long as antenna separation and monitoring (or precalculating) dbm levels happens, it works well. I dont believe however you can do full duplex on the same ...


1

I had the same problem, and found that the noise was due to electric meter telemetry. Our neighborhood is awash in this. It is regular, and it disappears on its own in about the same time to give the power button a meaningless quick push! Rather than push the power button for momentary relief, I 'found' that switching the channel and returning it 'did the ...


1

FYI C4FM is not allowed below 29 Mhz. This is because it is a wide band modulation and uses more than the allowable bandwidth for HF band transmission. Straight FM is not allowed below 29 Mhz for the same reason.


1

You will need a VOX circuit, and optionally, a VOX program. As long as the radio you are connected to is type certified, it is perfectly legal to connect it to a PC for the purposes of transmitting voice. First off, you need some aux cables, and if you PC has a combined speaker and mic jack, you need a TRRS splitter. You also may need a 3.5 mm to 2.5 mm ...


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