Category Archives: Homebrew

Next project-GPS locked 10Mhz source

Work is progressing well on the remote antenna tuner, more pics to follow soon. I am already thinking of the next project and decided I need an accurate 10Mhz frequency source for my counter and other stuff. In the past I have used a surplus rubidium standard and when that popped a GPS locked crystal oscillator.

That was over 10 years ago and things have changed. Used Racal Rubidium boxes are on ebay for between, £550 – £811. Bare bones Rubidium standards which need control circuits are priced at £157. These are often units removed from cell phone installations with an unknown lifespan remaining.

There are also lots of ready built Chinese boxes using 1PPS GPS sync for around £100 but in the spirit of making everything myself either from kits or self sourced components I decided to make my own.

QRP Labs have the QLG1 GPS Receiver kit and the ProgRock kit which makes a very cost effective combination. I have no connection with them except being a satisfied customer. Adding a box, power supply and other bits and pieces the estimated the overall cost will be below £40. The kits are ordered and I will share the build here soon.

See my build of a QRP Labs 20m QCX transceiver here

An Extron ADA4 300MX video distribution amplifier can make a cheap way of distributing the 10Mhz signal around the shack/workshop. See this page.

The radio shack, workshop man cave

This is where I spend a lot of time. It is part of an old converted barn that was a coaching stop between Manchester and Sheffield. It built into a bank with walls 2-3 feet thick which makes it very quiet and cool all year round.

Next project on the bench will be a remote antenna tuner using a couple of Arduinos with an RS485 link. See this F4GOH web page


The construction area. Note the solder fume extract pipe.


The fume extractor is an inline ventilation fan bought from a hydroponics shop. It has a variable speed control and works very well.


The SMD rework area. The heated tweezers will soon be joined by a hot air gun.

The mechanical workshop!

 

Pure 160m

I could not resist this! A RAT5 160m AM receiver in a Pure Evoke DAB radio case. It came into a repair cafe where I volunteer. It had been well and truly zapped when the PSU went faulty. I asked if I could have it for the bits. The case is a bit battered, but I am sure it will be fine.

The RX is built and working and there is lots of room for the TX, the FAT 5. Both come from
www.shortwaveradio.co.uk/projects.htm I have no connection other than buying the kits.

More to come.

Life is too short….

Last week I heard a QSO on 80M SSB where each op was using 400W and each gave the other 5-9+20db One op said ” I always use QRO, life is too short for QRP”. Reducing their power to ~6w would have resulted in report of 5-9+2db. Why waste so much power?

Interestingly I found this today on the North American QRP CW club web site; “According to Rich Arland, K7YHA (now K7SZ), in World Radio magazine (Feb. 1990, year 19, issue 89, pp. 46-47) the long-distance low power record is held by KL7YU and W7BVV using one micro-watt over a distance of 1,650 mile 10-meter path between Alaska and Oregon in 1970. This is the equivalent of 1.6 billion miles per watt.”

That is why I use CW with a 5W power output limit and often use much less. It takes more effort to work some stations and more skill and patience but the rewards are well worth it especially when using homebrew gear.

SW20

Topband 160m links and info

Here are some links to Topband, 160M, web sites in no particular order nor offering any sort of endorsement or recommendation. I am sure there are many more but for the newcomer they offer an insight into what the band is about.

I am about to order some relatively simple gear for 160M in the form of AM receiver and transmitter kits. More to follow.

The RAT5 RX and FAT5 TX kits
Simple but effective, AM,  RX and TX projects for 160m

160 Meter Radio Propagation Prediction Table
The table above represents a rough approximation of radio propagation conditions on 160 meters (affectionately known as Topband). It is to be used as a guide only and is not a definitive forecast. It is based upon selected high-latitude magnetic observatory data which is used to estimate the influence of the auroral oval on 160 meter path propagation (refer to the March and April 1998 issues of CQ Magazine for details: “160 Meters: An Enigma Shrouded in Mystery”, by Cary Oler and Ted Cohen).

The fabulous G4FPH topband WebSDR
Welcome to this WebSDR receiver (running PA3FWM dist11 software – big thanks to Pieter-Tjerk), located near Stafford in central England (IO92AS).

160mt
160 metres being a band like 6 metres offers challenges just above the AM broadcast band is not the easiest band to work DX, operating portable or mobile ETC.
Some AM portable radios can be adjusted to receive 160 metres by adjusting the local oscillator, Car radios can be also adjusted up but they can be very difficult and would suggest using an old unit with AM only.

160m am radio conversion
If you don’t have a general coverage receiver you can convert an ordinary am wireless. As most
broadcast sets cover up to about 1630khz it is possible in most cases to tweak them up to above 1.8mhz.

ONE SIXTY METER CROSSBAND RADIO
Stay tuned to this spot for the latest information on the regular one sixty meter crossband transmissions from vk3ase. Listen from 2230hrs Saturday evening till 0200hrs Sunday morning.  And Wednesday night/Thurs morning (Australian eastern time)on the one sixty, eighty and two meter bands for the largest  amount of bilge imaginable. The content of these missions range from discussions about radio, audio, computing and other related subjects through to social techno babble. Actually most of it is very silly and serves to modulate the carrier to comply with regulations. The program material is drawn from the extensive crossband archive going back 40 years and live missions.

Getting on 160 Meters on a Budget
There are very good reasons why you should not let this fascinating band “slip through your fingers“. The first is propagation. It typically is the last and least likely band to fail under adverse propagation conditions. It is primarily a night time band when it comes to DX due to D-Layer Absorption during the day. At that time, in particular the morning, and at night, it can provide NVIS (Near Vertical Incidence Skywave) mode propagation for local contacts. In times of local disaster when a repeater is down, this mode can get communications over mountains. 80, 60 and 40 meters can equally be used in NVIS mode propagation, depending of ionosphere conditions, but I’m only concentrating on getting you on 160.

160m-top-band-endfed-antenna-g3yeu-iss1-31.pdf
Links to a PDF file to download

Topband in Hawaii
The topband is rough in Hawaii with everyone else 2800 miles or more away. There can be significantly less thunder crashes much of the time versus the mainland. However we get fishing floats. These are believed to be illegal locator transmitters sending slow CW from top to bottom on the band. They are used by fishermen to relocate their drift nets in the Pacific ocean. They send a CW id and then some long dashes typically. The usual “Call Sign” uses three randomly letters, sometimes with a number mixed in.

Topband – 160 meters – Power Line Noise, de NØRQ
The 160 meter band, often affectionately called Topband by enthusiasts, is unique among all the amateur band allocations.  It is the lowest frequency range we can transmit on, and it presents technical challenges similar to the 80m band but in greater degree.  It is also called “the gentleman’s band”, because almost all the operators you’ll find there are good ones.  Technically, I believe that Topband is actually a MF (medium frequency) band, not HF, but those are artificial distinctions.

Top Band Magic: The Inverted L on 160M – brushbeater
JohnnyMac shows the radio world how it’s done. The ability to make and rig your own antennas is one of the cornerstones of communications preparedness- and his success demonstrates the praxis of what I teach. 160 is a big time challenge for a number of reasons- the antenna size being one- and his success at not only making solid regional QSOs but at QRP power levels on SSB no less demonstrates not only what’s possible  but how to do it on the cheap.

http://www.ok1cz.ddamtek.cz/160m_70s.html
160m is a special band. Like many fellow Topbanders I love it for its magic and challenge. I don’t feel like an old timer yet but I thought some of the memories would be of interest to those of my generation and possibly to the younger ones.

http://www.robkalmeijer.nl/techniek/electronica/radiotechniek/hambladen/pw/1991/08/page19/index.html
There’s been a lot of interest in 1.8MHz a.m. operation recently. To get you on Top Band’, the Rev. George Dobbs G3RJV and Ian Keyser G3ROO, have come up with the PW Chatterbox, a complete a.m. station.

160m – Topband – best for solar mimimum

I was digging around on the net today looking for simple deigns for Topband,  160M gear.  I found this article saying that it was best for solar minimum:  “The 160-Meter Band: An Enigma Shrouded in Mystery” which first published in CQ magazine in 1998. Here is some of what it says:

“Topband is one of the last frontiers for radio propagation enthusiasts.”

“The correlation between sunspot numbers and signal strength is only about 5% as strong as the correlation on higher frequencies.

”There are several important components that can improve your chances of successfully working DX on Topband. […] The trick here is to wait for sustained intervals of quiet conditions over the high latitude regions.”

It used to be the band for local rag chewing and I get the feeling it is either classed as just that or seen as the preserve of DX chasers with huge antennas farms. It can be both, but we can all have fun on Topband over the coming years without the constant depression of low or non-existent sunspots. I have a 38m long inverted L and had reasonable results on 160M a few years back so please do not dismiss the band without giving it a try.

It also appeals to me because it was my first intro to amateur radio. I used to look out of my bedroom window across the road to an aerial pole in the back garden of the next street. It belonged to G3LIO, Jim Gibbs. He was the first licensed amateur that I knew, and he and his father were very generous in helping me to start short wave listening back in the mid-1960s.

I have a few projects to complete to get back on the air but over the coming months I will make some Topband gear and give it a try. It will be low(ish) power AM to begin with. I also like the idea of working /P with long wire antennas supported by tall trees. It is time to modify the catapult launcher!

What is a redpitaya?

Doing a lot of home construction is helped by having a heap of test equipment. There are several ways of getting that; take a risk on eBay and buy old stuff, build your own or get a redpitaya.

It claims to be able to work as an oscilloscope, signal generator, spectrum analyser, Bode analyser, logic analyser basic, LCR meter and vector network analyser.

If it can do all then it is truly revolutionary, and I want one! It is not cheap but if you add up the costs of the single instruments it replaces then it is definitely NOT expensive.

Using SMD – part 1

Why do I like using SMD? Let me explain, I began making radios using valves, it was all there was at the time. When I started work in the industry the first training courses were on valves and how they worked. Then the transistor came, then integrated circuits followed by surface mount devices, SMD. I guess I have followed the technology.

It is easy to be overwhelmed by progress and stick with what you know but there are many advantages to using SMD:

  • individual components, resistors and capacitors, are very cheap
  • many older devices are no longer available as wire ended e.g. the SA612
  • PCBs are smaller due to high packing density
  • high frequency boards are easier and cheaper
SI5351 board

An SMD VFO module

Above is an SI5351 board (ready made apart from soldering the SMA connectors) it is just 30mm wide and can used with an Arduino to make VFO with 3 programmable sine wave outputs. Current cost is less than £5 on ebay plus the Arduino.

You might need some new tools like a magnifier, fine tipped soldering iron and good quality tweezers. There are more including heated tweezers and a hot air gun for component removal but they can wait for a while.

So, my advice is do not be put off and have a go. Find a simple kit to practice with and then progress to more complex circuits. It helps if you know something about how SMD components are sized. Srat with the larger sizes and work down.

1206 and 0805 are popular SMD sizes

This is another good one to print out.

Over the coming month I will add to this series of posts and share some of the projects I am working on which include: a remote tuner, vector network analyser (VNA), wide range VFO/signal generator, a switched attenuator.

The antenna

The antenna is back up after 6 years! Nothing fancy just an inverted L at about 11m (~35ft) and around 38M (125ft) long. Still need to put in a counterpoise in the lawn but the ground is rock hard after weeks of drought, so it will have to wait.

Also need a remote tuner and plan on making one based on an Arduino.
https://hamprojects.wordpress.com/2016/12/31/hf-automatic-tuner/

I have a nice waterproof box that housed a commercial tuner to house it and will probably make it solar powered to avoid have to DC up the coax. Hope to get the coax in this week, it is something like a 40M run of RG-213. So, work to do before winter!