Category Archives: Homebrew

Low cost frequency standard

I have been looking for a low cost frequency standard for a while to replace one I once had about 10 years ago. The only way to do it then was to build a GPS locked oscillator. I chose the extreme overkill route and locked a doubtful rubidium standard to GPS. It worked for a while and then the rubidium kit stopped working.

The next solution was to lock a temperature-controlled 10Mhz crystal oscillator. It worked well enough as along as it was left on all the time. Recently I have been looking for a cheaper and less complex way of providing a 10Mhz standard signal for test equipment and radios.

Things have moved on and the GPS modules that used to be relatively cheaply available on ebay are no longer there. Ditto oven-controlled oscillators. Then I found the ideal solution on the QRP Labs web site; a “ProgRock – triple GPS-disciplined programmable crystal” which is basically a Si5351A chip programmed for a single frequency. It can be GPS locked via a 1PPs signal from a GPS receiver, the “QLG1 GPS Receiver kit.” An order was placed.

The kits arrived, and I spent a few hours yesterday building them. As usual with QRP Labs kits they all worked first time. The first check was my £17 ebay counter, a Racal-Dana 9918. It was 5.2Hz low at 10Mhz! I could try adjusting the internal 10Mhz oscillator but it might take a while to get it to read 10,000,000!

The better option is to complete the project by building a small distribution amplifier which will give 3, 10Mhz sine wave outputs from the ProgRock and use one of them as an external timebase for the counter.

The PrgRock with scope probe attached

GPS board with patch antenna.

The kits, parts for the distribution amp and a case will cost around £35 in total. That is probably about one tenth the cost of the previous project!

Is this all overkill? Well yes and no. Modern transceivers are accurate but when you build your own you never know. Also, the move to VHF, UHF and microwave for satellites means I want to be sure that the frequencies are correct. This crucial when multiplying up free running crystal oscillators as any error will also be multiplied.

The usual disclaimer, I have no connection with QRP Labs other than being a satisfied customer. This review/article was not solicited by them and they had no knowledge I was doing it.

 

Why home construction?

I am often asked why I bother with home construction. Why make stuff when it is so easy to go out and buy it? The questioners sometimes go as far as asking why I waste my time.

There are lots of reasons; it is something I have always done, it saves a lot of money, you know your gear well so can repair it and most of all I learn something, sometimes the hard way!

All of that is summed up in this quote I found today:

“The excitement of learning separates youth from old age. As long as you are learning you’re not old” Rosalyn Sussman

First test of the remote ATU. The control box is the next job.

I am now eight months in to my aim to build a totally homebrew station. I am at the point of having some working transceivers, power supplies, an antenna analyser and a long wire antenna. The remote tuner is almost done but is proving troublesome. By the end of the year it will all be sorted!

The SDRPlay RSP1A-a momentary lapse

At the RSGB Convention last week I broke my pledge to have a 100% homebrew station. There was a demonstration of an SDRPlay RSP1A right next to the Martin Lynch stand with a small pile of boxes on sale! Not only is it a wide band receiver there is also spectrum analyser software available and all this for just less than £90.

The justification was simple; I build transmitters and need to be able to check the harmonics and other spurious signals to conform to licence regulations. It does not have to be an absolute measurement just the level of the spurious emissions compared to the carrier. And spectrum analysers are expensive.

Then there is the imminent launch of Es’hail, so I need a 10Ghz receiver to listen to it. The conscience clincher was a demo by the microwave group of a modern satellite TV LNA connected to an SDR receiver. Simple. Another reason to get the RSP1A.

And then there is 630m. You get the message, justification for the temptation and I must confess I had a moment of weakness and succumbed. I am trying to atone by finishing the remote tuner.

Not had much time to play but what I have seen is impressive. SDR receivers are incredible, amazing etc. This morning I listened at the top end of 80m for the transatlantic DX spot, 3.798Mhz and was astonished to hear AA8KB at 5-7 on the meter. This is on an untuned inverted L sloper with the high end at about 10m and low end at 6m.

This is a short recording of AA8KB holding the recorder close the the PC speaker.

I can only confess to this lapse and argue that this was a one-off purchase of an extremely useful piece of kit!

The usual disclaimer, no connection with the company and these are my own views.

Update a half hour later. Just gone back to the SDRPlay and found the RF gain was almost turned to minimum.

Practical Wireless February 1960 – pure nostalgia

At the Newark Hamfest last month there were old copies of Practical Wireless magazine going for £4 each. Having been a reader of the mag since about that time I could not resist.

It is more often the adverts that get me. I remember spending hours drooling over all the ex WWII radio equipment and wishing I had the money to buy some. It did happen a few years later when I was allowed a sol trip to London for the first time. It was a steam train of course.

I was looking for London Central radio Stores in Lisle Street, Soho and did what all kids were told to do and asked a policeman for directions. He looked down on me very suspiciously and asked “now what do you want to go there for lad”. I explained it was for the radio shops and he looked even more suspicious but eventually told me which way to go. I found the shop which obviously had other tenants upstairs who were eager to divert me but the radios were far more interesting!

Here are some adverts and nice little VFO project. I like the sub heading “frequency stability is always a valuable feature”.

PW-1960-002
Orientation: 1
« of 5 »

There are many more copies available online at this site but you do not get the smell of old magazines.

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 6.25W 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!