# Tag Info

17

The "UHF" PL259/SO239 connector, which was originally designed at World War II times as a shielded banana plug is actually not a very good connector to be used on UHF frequencies, due to its non-continuous impedance and other properties. The common name is a bit misleading, since it's old - at the time of the design, UHF referred to frequencies above 30 MHz, ...

16

If you are interested in the electronics and technical aspects of transmission and reception, then yes, now is a fine time to get involved in building your own radios. If you are more interested in pursuing communicating with other users, though, your time and effort would be better spent using a good rig. Now is also a great time to get into Software ...

14

A waterfall display is a graphical representation of the signals across a frequency range, generally color-coded to indicate signal amplitude or strength, displayed over time. image source: ARRL and K2NCC Pictured in the image above is a number of signal traces. Since the above was taken across a frequency range where PSK31 is used, the signals are very ...

12

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 ...

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 ...

12

Your problem is that there's really but one globally usable unlicensed band, and that's the 2.4 GHz band. But that doesn't sound so bad. People think "high frequency = short reach", stemming from the well-known Free-Space Path loss formula $$P_r = P_t \cdot G_t G_r \left( \frac{c_0}{4 \pi fd} \right)^2\text,$$ where the received power $P_r$ falls with the ...

8

Why aren't there monolithic HF ICs. There are, in the shape of actual (broadcast) AM receiver ICs, which can most likely with minimal effort be also used to transmit. However, are there technical reasons we don't see monolithic HF ICs? Your market considerations are something I'd very much agree with. Why build a monolithic IC for something that is ...

8

Two Yagi antennas on the same antenna port could work for this application. Join the feed lines from the two antennas with a power divider for proper impedance matching. Make sure that they are mounted in-line with each other with the two driven elements some multiple of a whole wavelength apart. This ensures that the rearward radiation of one won't partly ...

8

The basic concept is to use RF bandpass filters for each frequency range. This is frequently done by hams for VHF and UHF applications. The common term for a grouping of these filters is diplexer, triplexer, or quadplexer as appropriate. Sometimes the term "duplexer" is used although this creates confusion with a different device that is typically much more ...

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 ...

7

Every linear amplifier designed to work with a transceiver has a bypass circuit which switches the antenna between the amplifier and transceiver. When transmitting, the transceiver connector is connected to the input of the amplifier, subsequently the output to the antenna. When receiving, the amplifier circuit is disconnected and the antenna is connected ...

7

A wideband antenna is not what you're looking for – you really don't care about anything between 900 and 1500 MHz, or between 1600 and 2400 MHz. Wideband antennas are inherently hard to make, and even harder, even impossible, to make uniformly good across their whole range. What you much likely will rather want is a multi-band antenna. For example, I'd ...

7

This is very likely to be be due to overload of the receiver. A quick, rough way to tell the difference: Tune your SDR receiver so the waterfall center frequency is not the same as the transmitter's frequency. Transmit. Check whether the spurs you see are symmetric about the transmitter's frequency or the receiver's frequency. This tells you which side ...

7

One of the fine folks from MMRCG identified this as model R-1484/PRR-15

6

There is no such thing as a minimum power level at which a conductor will start radiating. If it radiates at all, then the radiation will be proportional to the power applied. Therefore, the maximum usable power in this circumstance is the power at which such radiation will interfere with (or damage) the receiver, and in order to know it you must test ...

6

I used LiFePO4 (read: Lithium Iron Phosphate) for my dad's FT-891. The big advantages of LiFePo4 are: Very power dense, almost as much as Li-Ion, IIRC twice as much Wh/kg than Lead-acid Extremely safe: they don't short circuit themselves to flames, like Li-Ion does Flat voltage discharge characteristics: their nominal voltage is 3.2V and they stay at 3.2V ...

6

It might be a good idea to start by trying to make a block diagram of what you have inside of each of those controllers... Namely, the drone controller is most likely some sort of a system on a chip, which on its own chip, in addition to having a microcontroller also has the radio interface built in. Those are two separate things, but in one package. ...

6

A wire will pick up a GHz signal, as well as a ton of other RF signals, all mixed together. Some sort of filtering is required to separate out your desired radio signals. An Arduino has none of filtering required. Sampling a 2.4 GHz signal requires a sample rate above 5 billion samples per second. The A/D on an Arduino samples at a rate of about 9000 ...

5

Largely it has to do with filtering and bandwidth. An ADC requires an anti-aliasing filter to remove all input frequency components that are more than half the sample rate. Otherwise, these higher frequency components get aliased onto lower harmonics. As an example, if I have a 40 kHz ADC, it should be able to handle at its input anything from 0 to 20 kHz. ...

5

1) listen to FM radio, while scanning 2 meters and 70cm bands at background (as in hiking)? nope (and only 1 band scanning at a time) 2) set scan hi and low limit, via keypad and/or pc software, so that scan within ham band only (instead full transceiver freq range)? nope, but you can limit the ranges using chirp 3) scan 2m and 70cm 'simultaneously'. ...

5

See This Chart at BaofengTech.com. Really the UV-5RE is just a cosmetic variant of the UV-5R. As to your firmware version you should check out this page at Baofengtech.com. Sadly it is not very helpful with your firmware version: BFB297, BFB298 Unknown Changes But it is still a great reference.

5

This is a huge area and personal preference is going to drive the choices to a great degree. For a good answer some parameters need to be defined: Are you only going to operate the rig if you are in trouble? This defines the size/cost/weight of your choice. If you are going to also operate “normally”, the rig can take up more of your space/weight budget. ...

5

None of the major amateur radio manufacturers make a rig for the 3cm band (or most of the microwave bands for that matter). The common practice is for hams to buy or build a transverter which downconverts the received signal from 10GHz to (often) 146MHz and upconverts the transmitted signal from 146MHz to 10GHz. In essence, 146MHz becomes an Intermediate ...

5

At 8W, the power from the radio is 9.03dB. With the cable losses of the receiving station being 1.5dB (1.41W), and the antenna receiving 1.733e-8W, it appears the received signal will never make it to the receiving station's radio. This seems to be the crux of your misunderstanding. You can't convert watts into decibels, or decibels into watts. A ...

5

It depends mainly on the culture using the frequency, the frequency value itself and how important is each part of the frequency. In the lower frequency ranges, it's not uncommon to give the frequency in kilohertz. For example, the broadcast radio station I'm listening to right now is on frequency of 7375 kHz (or 7.375 MHz), that is to say the carrier is ...

5

The article does in illustrate things rather nicely. Let's look at the receive side first: Signal (@437 MHz)-->(x)--> filters --> IF (@x) ^ | Oscillator (@(437 MHz-x))-/ What happens is that your input RF signal at $f_\text{RF}$ is multiplied in a mixer with a tone of frequency \$f_\text{LO}=...

4

At least in Finland you are allowed to use the entire band from 10.0 GHz to 10.5 GHz with "secondary rights". Maximum TX powers are 30 W (basic class) and 150 W. The 3 cm band is also available at least in the USA: http://www.arrl.org/frequency-allocations

4

Lithium, NiMH, then Lead acid. Lithium batteries are expensive and potentially hazardous. Among these, Lithium Iron Phosphate, or LiFePO4, is supposedly less dangerous, but still needs a charge/discharge controller. You can find replacements for 12v batteries on eBay using LiFEPO4 and capable of high currents of transmitting but those are still several ...

4

I built a BitX 20a, which was fairly complex, but a really neat kit. If your soldering skills are ok, and you can wind small wire through tiny donut shaped cores, you will have a lot of fun. The SMK-2 40m kit might meet your needs (40 meter CW), but it's surface mount. Don't be afraid of that, with a good magnifying glass, and some inexpensive chinese made ...

4

The main differences with these units is FIRMWARE! The firmware can be checked by powering off the unit and holding the "3" key down as you power it on. This number however does not always reflect the true firmware version and I recommend using CHIRP and a programming cable to find the firmware listed on your exact radio. For reference I recommend you ...

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