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1500 questions
6
votes
1 answer
Pre-transmission burst sent by fldigi
Every time I click on a PSK macro, before transmitting the message, fldigi outputs a burst of something for about a second. This is visible but not readable on my waterfall display. It wastes time and I want to get rid of it.
Andrew Rose
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6
votes
2 answers
How does rpitx generate arbitrary SSB data with a clock peripheral?
While it wasn't the first to do so, the rpitx software seems to be the most active and mature implementation of what its own comments call "a code fragment by PE1NNZ". The trick is explained in Guido's original Direct SSB Generation by frequency…
natevw - AF7TB
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6
votes
4 answers
Which is better in my situation: Balanced dipole, or as much wire as possible in the air?
I'm finally getting to the point of hopefully putting up a HF antenna. The idea is to start with a simple, straight wire dipole using trees as support points. (No traps or coils.)
However, with the layout of my property and the location of the trees…
user
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6
votes
1 answer
How to ground with little surface area?
Let's say I have a very small device, like an RC airplane, which transmits information as well as receiving commands for control. The body is made out of non-conductive foam, therefore not much ground is available. How can quality transmissions be…
Skyler 440
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6
votes
1 answer
In amateur radio conversation, what does "hihi" mean?
A common phrase/word I've seen used in text and I've heard on air in conversation is "hihi" or "hi-hi". What does this mean and in what contexts is it appropriate to use?
user2943160
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6
votes
4 answers
How to build a remote control unit that works on amateur radio frequencies?
The only remote control units I have used before was those little cheap 27Mhz puny range cheap units. I would like to build some sort of RC unit, which has a range up to 1km line of sight.
I have a general license. How can I get started with remote…
Skyler 440
- 7,600
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6
votes
3 answers
How should this SWR meter's directional coupler work?
I'm wrapping up a "home build" of the MFJ-941EK antenna tuner kit and having trouble getting the wattmeter calibrated. I can't use C4 to get the reflected power reading calibrated down to 0 as is supposed to happen. So now I need to figure out what…
natevw - AF7TB
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6
votes
2 answers
How to measure a balun for effectiveness?
It seems there are almost as many "balun" designs as there are web pages about "baluns". There's lots of accusations pointed in all directions ("design Z isn't a balun OR a choke", "design Y is overkill", "design X could lead to spurious…
natevw - AF7TB
- 7,411
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6
votes
1 answer
Pseudorange in VHF band navigation and precision phase tracking
I am thinking on what is the practical limit of precision for VHF positioning system (like currently obsolete and gone "Transit" system).
It is well known how GPS receivers calculates pseudorange to each satellite to calculate the position of the…
BarsMonster - R2AYN
- 396
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6
votes
7 answers
Are there any commonly used digital modes that work with an FM transceiver?
Like many new hams, I have just one radio: an inexpensive 2m/70cm FM transceiver. It doesn't do SSB and it doesn't have a digital input. If I wire up a connection between the radio and my computer's sound card, are there any digital modes that I…
mrog
- 1,023
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6
votes
5 answers
Shortwave Antenna Listening with Portable Receiver Like TECSUN PL-660?
I have a Tecsun PL-660 (link is to the manual) has the usual AM/FM radio telescoping internal antenna, and a 1/8th-inch jack for an external shortwave antenna. There appears to be no facility for attaching to station ground, unless one of the…
Warren VE3WPX
- 895
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6
votes
2 answers
Antenna length in relation to lambda length
I'm pretty new with antenna stuff. I'm not sure how to understand antenna length in relation to lambda with dipole antennas.
If a simple dipole antenna is lambda/4, has it a total length of lambda/2 (every pole lambda/4 long) or a total length of…
leAthlon
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6
votes
3 answers
How can I construct a practical loop antenna for 2m band?
How can I construct a practical loop antenna for 2m band to use in a fox hunt? Is it even possible to construct a hand-held antenna for the 2m and 70 cm bands? I tried to calculate the dimensions using a few online tools and formula, and the…
KF5RRR
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6
votes
1 answer
What kind of modulation is this?
I was able to demodulate a signal I've received in gnuradio. Here you can see my flowgraph:
But now I would like to be able to send data as well. But how should I modulate my data? As you can see I've demodulated with Quadrature Demod -> Hilbert ->…
Thanathan
- 161
- 3
6
votes
1 answer
What happens to the "Yo-Yo Tenna" when you coil up its ends for use on higher frequencies?
I have gathered what is basically a Yo-Yo Tenna using some Camco laundry reels and a spool of cheap speaker wire split in half (pretty much exact duplicate of this build as it turns out). I've got a bit of equipment to measure the amount of noise…
natevw - AF7TB
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