Chinese receiver

This RX is called the K3.  This is not to be confused with the Elecraft K3. Certainly I was confused!  

It is available from AliExpress at about £60.  There seem to be a lot of these low cost Chinese receivers about.

Simple VHF receiver by Charles Kitchen

Charles Kitchen N1TEV is a well known designer in the USA and across the world. 

This is a circuit for a VHF receiver that can be adjusted to decode SSB, CW and NBFM in addition to AM.

See https://www.arrl.org/files/file/Technology/tis/info/pdf/9712039.pdf .

How? ATS-20+ RX

Just now I saw a Chinese RX on Amazon. 

At £44.99 I just cannot see how they do it.  

Simple regen RX

Many people like simple, but effective, receivers. This design is probably one of the simplest you could make. It works very well.  There are several examples of this, and others, on YouTube.

Ultra-simple RX

Some years ago, I wanted to see just how simple a receiver could be made with a decent performance. Later, this was converted into a full transceiver.  For so few parts, it is remarkable.

See https://sites.google.com/site/g3xbmqrp3/hf/regen

Regen 40m and 80m RX

A nice simple RX built by NG9D is demonstrated on YouTube.

A dead simple regen receiver

There are plenty of designs out there (try Googling "regen"). but I offer you this simple design with very few parts. It works. You may be surprised that something so simple can hear so much.

See https://sites.google.com/site/g3xbmqrp3/hf/regen .

DST100

In the years following WW2, there were plenty of surplus transceivers and receivers around, often in "as new" condition. Also, many built their first TV set using surplus radar gear.

My first real receiver was a DST100 bought from a local garage for £7. It was deaf, but attention by Roger G3CHN soon had it working well. It heard some impressive DX, but weighed a ton.

See https://sites.google.com/site/g3xbmqrp3/hf/dst100

DST 100 receiver

My very first communications receiver weighed a ton (it took 2 people to move it!) and was a DST100. I believe it was made by Murphy during WW2. This receiver, I have since learnt, was designed for intercept listening. It was built like a tank with a huge rotary turret tuning unit. The radio cost £7 from a local garage and it was overhauled (new valves?) by (the now late) G3CHN. It covered from around 50kHz to over 30MHz and heard some impressive DX. I was always puzzled why signals were so broad on the lowest range, not realising at the time that it covered 50 to about 150 kilohertz!  This was in 1962.

At that time there was little amateur band gear available (none from Japan) and lots of us used WW2 surplus gear which was available at low cost from many suppliers. Popular receivers were the AR88 and CR100. Transmitter-receivers included the WS19, WS38 and 52 sets.

Amateur radio in the 1950s and 1960s was quite different with lots of HF AM still and most people building their own transmitters. SSB was in its infancy. In many ways it was the high point of the hobby, although today we are blessed with low cost gear, free software,  more modes and more bands. The hobby means different things to different people. Long may it continue.

See https://sites.google.com/site/g3xbmqrp3/hf/dst100 .

VLF receivers

To detect VLF amateur signals it is pretty essential to use a good receiver (with frequency locking so extremely narrow bandwidths can be received for hours or days on end) and Spectrum Laboratory software. Spectrum Lab has options to lock to one of the powerful MSK signals near 20kHz and this transforms stability.

For reception of natural VLF emissions it is somewhat different as signals tend to be stronger and of much shorter duration. There are several VLF natural receivers on the net. See http://www.vlf.it/romero2/explorer-e202.html for a typical example.

100kHz - 1.7GHz SDR

This data was passed to me by Steve G1KQH (again). It looks like an SDR in a screened box with proper interfaces. It comes from Hong Kong. Price is £36.99. I have never played with SDS dongles.

See

http://www.ebay.co.uk/itm/100KHz-1-7GHz-full-band-UV-HF-RTL-SDR-USB-Tuner-Receiver-R820T-8232-Ham-Radio-/191241138400?pt=UK_Mobile_Phones_Communication_Ham_Radio_Receivers_Transceivers&hash=item2c86dc30e0

 

SAQ - historic 17.2kHz CW transmission this Sunday.

A reminder that the historic alternator TX on 17.2kHz VLF will be sending a message this Sunday twice. They usually QSL via the amateur QSL bureaus. See http://alexander.n.se/in-english/saq-transmission/ for more details of this and other transmissions.

Some years ago I copied the transmission, QSLed and am the proud owner of one of their QSL cards. It is not hard to copy in Europe unless you have local noise problems. A small tuned loop is all the antenna needed. There are even a software receiver available free on the net capable of receiving the transmissions with a suitable antenna connected to the PC. The SM6LKM software receiver is excellent and covers 0-22kHz. It makes a very useful VLF receiver. I describe it on my YouTube Channel G3XBM.  See https://www.youtube.com/watch?v=TDxRhQYg7lQ.

472kHz (quiet) RX preamp

When the grandchildren and family have all gone home next week, my first project will be to improve the RX antenna system for 472-479kHz receive. As mentioned before, I am suffering badly from SMPSU noise pick-up inside the house, so plan to install a magnetic loop and preamp somewhere towards the bottom of the garden in an attempt to minimise pick-up from my own home and from neighbours. With a loop there is also the ability to sharply tune the antenna and to null interference from the worse directions. The circuit I propose to use is a version of my 9kHz tuned preamp, which has been used to copy G, DL and OK amateur stations on 8.97kHz last year. The loop will simply be retuned to the new MF band.  Not sure whether series or parallel connection to the loop will be better as both should work depending on the FET stage configuration (common base or common source).

Proposed tuned preamp, but with values changed for 472-479kHz

Improved Software VLF Receiver

SWL Roland's enhanced SM6LKM software VLF receiver

An SWL called Roland from Germany has produced an enhanced version of SM6KLM's software VLF receiver, originally designed to allow reception of SAQ on 17.2kHz CW. The new version has:

•  44.1k/48k/88.2k/96k/176.4k/192k sample rate support
• More CW filters, SSB filter and AM filter added
• Spectrum display for audio frequency
• File-I/O for *.wav format (16bit)
• Left/Right channel select
• RMS signal level bar for audio level
• Muting (M) key
• Time+Date display, UTC or local time

This now makes the "enhanced" SM6KLM software receiver a superb tool for VLF use. Information and downloads are available at Roland's website https://sites.google.com/site/swljo30tb/

To use the receiver all that is needed is a VLF signal feeding into the mic input of the PC. Be sure you know what you are doing: the usual safe thing to do is to put a couple of back-to-back diodes across the DC isolated VLF input to prevent damage to the sound card. With an E-field probe antenna this receiver is capable of receiving many VLF transmitters from around the world. I shall be using it in future to monitor my 8.97kHz earth-mode CW beacon when out in the field testing.  

RX performance comparisons (and the KX3)

http://www.sherweng.com/table.html

Sherwood carry out comprehensive tests on various amateur products. See the full list in the link above to get an idea how good the Elecraft KX3 is. Sometimes ultimate performance is unimportant but it does indicate which products are the very good ones when it matters .

Simple VLF Receiver

SM6LKM's excellent PC based VLF receiver

In testing my Chirpy 10m transceiver, I used the simple PC based VLF receiver by SM6LKM as a bolt-on SDR. This little VLF receiver works very well as a stand-alone VLF receiver that tunes the 0-22kHz frequency range. Simply by sliding the cursor to any frequency it produces an audible signal just as you would get by tuning a conventional receiver.  Bandwidths are adjustable down to around 300Hz. For my video showing this in action listening to VLF signals (via my loop and small preamp) see http://www.youtube.com/watch?v=TDxRhQYg7lQ. With the SM6LKM VLF receiver you can clearly hear the Omega beacons around 11-14kHz, SAQ when transmitting on 17.2kHz, and various MSK military signals around 18-22kHz. It has also proved useful when carrying out earth-mode (through the ground) VLF communication tests.

Soundcard based VLF receiver

SM6LKM has a very neat sound card based VLF receiver ideal for listening to sub-9kHz ham signals and SAQ on 17.2kHz. On his website you can download the files and instructions.

USB powered direct conversion RX

G1INF has a neat idea on his blog for a simple direct conversion RX that is powered from the USB connection of a PC. His application was for LF reception but it would work equally well as the front end of a simple SDR for any HF band, replacing the loop with a bandpass filter. The audio output from the NE602 is connected to the PC's mic connector. Simples!

UK on-line VLF Receiver

There is an on-line VLF receiver on which you can hear natural emissions such as sferics, tweeks and whistlers located at Todmorden in the north of England. As well as a real-time audio stream, it has an interesting way of plotting received signals so you can see the direction of arrival of sferics.

Dutch online SDR now has 500kHz

The Twente University online SDR in The Netherlands has now got a 500kHz receiver. It works well and SM6BHZ's SSB beacon was coming through very well a few moments ago.