# Tag Info

16

My understanding is that in at least some telegraph systems, the principle of operation was as in this circuit (where the coils depicted are actually telegraph sounders): simulate this circuit – Schematic created using CircuitLab Thus, your key's shorting switch is, in radio terms, your transmit/receive switch: you close it in order to listen, and ...

15

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

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 ...

11

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 ...

10

A cross-meter is capable of showing you three measurements simultaneously: Output Power Reflected Power SWR From this image by Axel Schwenke on Wikipedia, you can see that the needle on the left indicates forward power, and the needle on the right indicates reflected power. The observed intersection of the two needles can be used to indicate the SWR of the ...

6

Assuming you are in the US (sorry if I'm wrong, but you didn't specify!), normal WiFi falls under Part 15 regulations which limit the radiated field strength, not the transmit power. This means that, assuming the transmitter is not underpowered, you cannot legally increase the range using directional antennas. Supposing you did so anyway, hooking up ...

6

A properly calibrated cross-needle power meter such as e.g. the MFJ-842 actually tells you something more than just the forward and reflected power, which as you point out can just as easily be indicated by two separate instruments. The intersection of the needles gives you a pretty good indication of the actual standing wave ratio or SWR because the SWR is ...

6

Land line telegraph keys are fitted with a circuit closer switch. Radio telegraph keys were not but many radio operators used land line keys because they were so readily available. This includes the rather ubiquitous J-38 about which more will be found below. The arcing that occurred at the key contacts of the early spark radios caused radio stations to ...

6

The answer to your question involves both technical and regulatory issues. Technical Considerations Radio signals can travel between two locations on earth either by line of sight or by propagation which involves bouncing signals off of the atmosphere or other objects. In general, line of sight is a reliable means of communications whereas the use of ...

6

In modern, medium- to high-end equipment, chances of dry solder joints are slim to none, especially in radio equipment, where your solder process needs to be especially safe against this kind of failure to not inadvertedly add parasitic capacitance. I'd agree, electrolyte capacitors are a prime aging suspect. They've gotten better, so in most cases, I ...

5

4W to 8W is a doubling of power, or a 3dB increase. That's 3dB you can add to your link budget. Provided of course that the limiting factor is the other station hearing you, not the other way around. Let's say with 4W you can be heard up to 10 miles away. In idealized conditions (no terrain in the way, no interference, etc) 8W increases your range to 14.1 ...

5

The exact answer is given by the Friis equation. If you double the power, your range will increase by 1.413 times whatever it was before doubling the power if you change nothing else. This assumes you do not violate line of sight rules and that there are no additional obstructions in the longer path. You could get this same effect by doubling the gain of ...

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

Out of left field - If function is the only cause and fashion isn't an issue, use a couple of black cotton socks. On my headphones the plastic outer pieces are removeable. I cut the ends off two socks, slid them over the phones and my wife sewed them in place. Comfortable, although the seams do show a little. I don't care! Cost nothing and works fine!

4

I've done some tests with what I have available (now including the CT-44 adapter). With the MH-37A4B Earpiece/Microphone connected, the internal microphone can still be used: whichever mic has its PTT switch pressed will provide transmit audio and the other will not. Furthermore, the external microphone is open-circuit when its PTT is not pressed. Therefore,...

4

Nearly any SSB HF rig will do. You need some way to get audio out of the receiver and into your computer, and out of your computer and into the transmitter. Most modern transceivers provide some kind of connection for this. In a pinch, you can use the headphone and microphone connections. It's also convenient (through not necessary) if Fldigi can key the ...

4

The switch on the side of the key is or rather was used when tuning up a transmitter. In the old days you had to increase drive and dip the grid of the final amplifier. So this is simply a switch so that the operator can key his transmitter and use both hands for the operation. Today you don't tune like that UNLESS you have a high power amplifier. But ...

4

You didn't mention which country you're in, but in the US, it is only legal to transmit on CB with a "type-accepted" radio. In other words, the manufacturer of the radio must apply to the FCC for permission to sell the model. It's not legal to build your own CB transmitter. Regarding using a single antenna for multiple bands, a transmitter typically ...

3

The correct answer to your question is, I believe, that you should expect an increase of between 20-40% in range, depending on the height of the repeater(s) you are trying to hit as well as your local propagation environment (e.g. urban, suburban, free space, etc.). I think it is a trickier question than it seems because it depends on how marginal you are ...

3

The connector is called an "HN" type connector. It has a 3/4-20 thread and it is usable up to 4 GHz. The Amphenol data on it is available here.

3

Of your quoted testimonials, the one I'd put the least credence in is the 10 miles at 4w and 16 miles at 8W, because I'm not sure what they mean by the "elevation difference" disclaimer; at these frequencies even a small difference in location, especially in elevation, can make much more difference than doubling wattage. The rest seem pretty much spot on. ...

3

Based on my somewhat short experience as a ham, these are some of the things I find very useful in my shack or would like to have: a comfy chair paper/writing instruments and/or computer for logging purposes a hook or clippy thing to hang your microphone from (if you're not using a desk or boom mic) shelves. you can never have enough shelves in the shack. a ...

3

The official ARISS web site documents the current equipment as follows (scroll down for the headline Radios, Modes and Antennas on the ISS): The ISS amateur radios are Ericsson MP-X handheld radios, a Kenwood TM D700 and a Kenwood D710. The crew is currently able to use these radios to operate on the 2 m and 70 cm bands. Voice, packet radio and SSTV ...

3

According to Wikipedia and ISSFANCLUB, in 2011, they had a Kenwood TM-D700 UHF/VHF rig, and also an Ericcson UHF/VHF rig. When the Kenwood had problems, they switched for a while to the Ericcson backup unit. http://en.wikipedia.org/wiki/Amateur_Radio_on_the_International_Space_Station http://issfanclub.com/node/35931

3

Reading about SDR I think I can have one single antenna and use the computer magic to allow me to work with all frequencies that antennae receives, am I mistaken? Well, I always explain it that way: An SDR is like a soundcard on speed. Usually, with a mixer. So, what the SDR does (in Receive direction) is take a spectrum of bandwidth $B$ (for example, 10 ...

3

Don't forget about CHU (and here is the official site) which is the Canadian equivalent to WWV. It's at lower power and it's not as well-located geographically (it's located near Ottawa), but it's receivable in most of the eastern US and increasingly less well as you head west. Here in VE5-land (Saskatchewan) I certainly receive it sometimes, but I also ...

3

Audiophiles like to replace those plastic and foam earpads with a velour product such as this: If red doesn't suit you, there are other choices. There are several vendors for this type of product, with Brainwavz Audio as one example.

3

You say you are "not supposed to build with a kit". Who has set this limitation? This is beginning to sound like a homework assignment. Are you actually expected to design and build a radio receiver and transmitter without looking at other people's prior work? And on top of this, you say in another question that you do not have an amateur radio licence, ...

3

There are standard connectors for microphones, speakers, and headsets, but unfortunately the pinout diagram (schematic) changes very frequently. There is no guarantee that a headset with a 3.5mm TRRS plug that works with one radio will work with a radio from a different manufacturer, or even a different model radio of the same manufacturer. G4WPW's site ...

2

Trouble shooting equipment such as an antenna analyzer and VOM, replacement parts (PL-259's, etc), a soldering iron. Provisions for expansion as needed (another operator at your station during a disaster, etc.) Your initial list is a great start but it assumes nothing is going to go wrong.

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