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Messages - daedalus

1
A while back I was trying to imagine what I would do in the aftermath of a SHTF once I had established a degree of security.

Knowing what is going on and who else is out there would (for me ) be of high importance.

I realised that being able to scan big chunks of frequency across all bands would be desirable, also to be able to do this quietly. This led me to think a panadaptor waterfall would fit nicely (if the power consumption can be managed) and to be able to scan from ELF all the way up to the satellite GHz.

The only solution I found for this was SDR (Software Defined Radio) , the traditional "super heterodyne" receivers would only do sections of the spectrum and the waterfall bandwidth was not great (for this purpose)

What amazed me further was that the radio hardware was only $30 ! I have only just started exploring the area of SDR for disaster prepping but I see a lot of potential , I'm possibly late to the game but hopefully there is enough time left for me to get a working SDR setup.

Would be very interested to hear what Radio Preppers think about SDR, we have a dedicated section now
2
Antennas / Re: Magnetic antenna query
November 16, 2019, 12:10:16 am
I'm finding that as I dig into the fundamental antenna theory that it is very subjective, it seems that most of our modern antenna knowledge is empirical driven, the physics is not consistent.

This just spurs me on to dig deeper and hopefully at some point I will emerge with a clearer understanding.
3
Quote from: gil on November 11, 2019, 04:58:52 pmHi, sure, if you will be the moderator...

Gil.

This could be interesting ! Yes, I'm happy to be moderator and have the time to do this
4
General Discussion / Suggestion for new Forum topic - SDR
November 10, 2019, 10:55:14 am
Has a dedicated forum topic of SDR been discussed ? From a prepping perspective its got many aspects and seeing as it is most likely the future of transceivers it could be interesting to look at it separately.
5
General Discussion / SDR vs superhet : after disaster
November 10, 2019, 12:41:48 am
It definitely looks like the future of transceivers is SDR, this got me thinking: if there is a disaster with long term effects then the key aspects of transmission equipment will likely be :

1) reliability
2) repairability
3) durability
4) replacement parts
5) low power consumption
6) adaptability
7) portability

I would say 1-4 favours the superhet and 5-7 favours the SDR, although with 5) power consumption the laptop/tablet power consumption may need to be taken into account

So this probably means one of each , say an FT-817ND and one of the new SDR that is self contained (QSX, IC-705 TX-500)

That got me thinking, how best to use two transceivers (i.e. a superhet and an SDR) and I began to wonder, would it be possible to reconfigure the SDR to act as a power amplifier for the FT-817 ? or even to act as a digital modes device for the FT-817

6
Antennas / Re: Magnetic antenna query
November 07, 2019, 11:52:59 am
I posted the same query on an antenna forum and received this answer, now I just have to research to understand it ! It has also thrown a spanner in the works on my homegrown antenna theory (different thread):

"Far from sources, magnetic and electric fields are almost interchangeable: EM waves are made up of E- and H-, but if you know E you also know H. This situation does not apply near EM sources (such as antennas that radiate) or reflectors (such as conductors).

A small loop (by small we always mean the diameter of the loop relative to the wavelength of interest, so a 1 meter loop is very small at 10 kHz but very large for 10GHz) produces only magnetic fields. A small loop is basically an inductor; it has low impedance so charges cannot be separated. Magnetic fields flow around current; a loop is current and hence is circulated by magnetic field. The loop does not allow for charge separation (because it a short circuit); so very little electric fields are produced.

Contrast that with a short dipole antenna. Very little current flows, so very little magnetic fields are produced. The voltage across the dipole though can be large, since it is not shorted out. This means there is charge separation - which is what produces electric fields.

So there aren't magnetic and electric waves, but fields, that certain structures are much more sensitive too."
7
Antennas / Re: antenna theory - fundamentals
November 07, 2019, 06:56:50 am
I will do a youtube video and share the link, it's easier for me to use a whiteboard or pad and sketch it out dynamically. The challenge I am facing is how to show simultaneously time and distance so that it doesn't become a mess of squiggles !

There is one thing holding me back at the moment, how to estimate the electric field lines for a flowing current, there are plenty of static +/- charge diagrams and quite a few which show the "kink" in the field when the charge is accelerating but nothing about an electric field line for a sea of electrons flowing , any thoughts from anyone
8
I really like the sound of the QSX, just what I was envisaging. Would still require something external for JS8call but love that it does a lot of other digital modes.

Thanks for the steer to OH8STN, amazing info on the site

I will research the ability to transmit on any frequency and see what the possibility is
9
Tapatalk isn't finding radiopreppers , is the forum listed differently on Tapatalk ?
10
Antennas / Magnetic antenna query
November 06, 2019, 11:38:52 pm
How does a magnetic loop "know" it is to pick up magnetic waves and not electric , probably something very simple and if so apologise for asking !
11
Antennas / antenna theory - fundamentals
November 06, 2019, 11:37:18 pm
After watching the excellent videos on end fed half way antennas on the RadioPreppers youtube channel, I realised I did not have an instinctive i.e. fundamental understanding of how an antenna radiates. After much research, especially in the physics forums, I started to build up a new analogy that I haven't explicitly seen before, its sort of drawn from lots of sources of information.

It is very rudimentary at the moment , I'm starting with visualising a DC pulse along on open wire (the most basic of basics) and aim to build up from there.

The questions I have are :

1) Is this something that might be of interest on this forum
2) Are there any other people who might be interested in collaborating, I really could do with someone to bounce my thoughts off, either on the forum or offline
12
General Discussion / Re: https for the login ?
November 06, 2019, 06:08:05 am
Perhaps have a look at https://letsencrypt.org/ , its free and good
13
Classifieds / swap : Ft-857 & E92D for SDR
November 06, 2019, 12:02:33 am
I am looking to move to an SDR transceiver and would like to offer my Yaesu Ft-857D (BNIB) and also Icom E92D as possible swap equipment, any country considered because I travel a lot , can use cash to balance !
14
General Discussion / Re: radio preppers blog
November 05, 2019, 06:48:28 am
I thought that was the case ! weed out the non determined at the beginning. On plus side I can now spell Guglielmo although not entirely sure how useful that will be for prepping !

I did mention in a separate post that the captcha doesn't work very well with the visually impaired , I like the questions though
15
General Discussion / Re: Death By Microprocessor
November 05, 2019, 06:45:11 am
I completely agree with you that being able to transmit and receive morse coed by ear is going to be an essential skill that should be developed now whilst there is time.

The problem, I see with manual CW is that it requires the operator to be at the station for some time and this may be risky, it is probably safer to have the message sent and received automatically. For this reason I think we will see automated CW or more likely auto digital modes

I also think that the most likely outcome of a disaster that results in loss of internet will be am RF based internet replacement and its anybody's guess what format will emerge as dominant, Simplicity and reliability and low power will guide the choice but I also think encryption (have posted separately about that) will become critical