Posts Tagged ‘M0CVO’

Making Waves – The Shorty Forty

September 17, 2017 Leave a comment

I was taking part in a Twitter conversation today with someone building the helical antenna published in this month’s RadCom, the RSGB member’s magazine, and having issues with the matching of it.  He was trying it out due to lack of space and a poor earth (clay) at his QTH.

I set to thinking and remembered an antenna design that I used to hand out to Foundation and Intermediate Licence trainees when I was mentoring them through their studies and assessing their practical assignments.  This was the Shorty Forty antenna because we don’t all have the requisite 20.28m of free space to string a dipole across.  I shared the plans with him and later thought “Why not share them for everyone?” so here goes:

The Shorty 40 – Helical Whip for 7MHz

So you want to get onto 40m but don’t have room for a dipole (20.28m)? Then this could be just the answer if you have a little time on your hands and enjoy home construction.

The Shorty 40 is a helical whip for 40m wound on a 3m long, 32mm diameter piece of PVC tubing (the sort available in most DIY stores). You will need 21m of 1.2mm diameter enamelled copper wire, 80cm of 2mm diameter ECW and 10 or 15m of 1.5mm diameter insulated copper wire (the sort used for lighting circuits or earth wire). You will also need a SO239 connector and a piece of angled aluminium.

The picture says it all really but, just in case, begin by winding the 21m of copper wire along the length of the pipe, using tape or adhesive to secure it along the way. Cut the 80cm of 2mm ECW in half and push through the holes drilled in the top of the pipe. Solder together in the centre and solder the end of the coil here also. Drill a 16mm hole in the aluminium bracket for the SO239 socket and then attach it to the pipe using machine screws. Then solder the other end of the coil to the centre pin of the socket. Connect pipe to mast and connect two or three 5m radials to the solder lug on the aluminium bracket. Attach coax, raise mast and away you go.

Disclaimer  I cannot claim to be the first person to develop an antenna such as this but I have researched ideas on the internet and in books on the subject – from ARRL, PW Publishing and RSGB publishing – and changed them to suit modern metric measurements and make them easier to understand and build. 



Making Waves – Higher Bands, Transverters and Kanga.

January 12, 2017 Leave a comment

c1zrqflxeaaoreu The SG-Lab 23cm Transverter

So I finally bit the bullet and decided that it was time to extend my amateur radio boundaries beyond 433MHz.  I read various reviews and product descriptions and decided on purchasing a SG Lab 1296MHz transverter. I sent an e-mail to Hristiyan, LZ5HP in Sofia Bulgaria who constructs these units enquiring about pricing.  He promptly replied with a return e-mail and a PayPal invoice for 145€ (£132GBP).  I paid up (cheaper than expected) and within two days had tracking details and confirmation that it was on its way.  It actually arrived surprisingly quickly (about 1 week) using Bulgaria Post and then Royal Mail when it arrived on our shores.

The unit supplied is enclosed in a smart tin case and comes complete with an HB9CV “test” antenna printed on FR4 laminate. Both are shown in the picture above. There is also a DC plug (you need to supply the wire and solder this yourself) for the power.  You will also need a BNC to SMA pigtail lead to connect to whatever you choose to use as an IF.  I am making use of my mostly redundant FT-817 for this.  The IF is from 144 -148MHz.


For a test antenna, the supplied HB9CV demonstrates a rather good match as can be seen from the above Smith Chart produced by my MiniVNA Tiny.  With 3.2dBd gain it has quite promising performance as a suitable antenna for local ops too.  The instructions are available online at and these will be needed for setting up the unit.  Nothing too complex though but you will need to remove the top cover and possibly use some long nose needle pliers. for setting jumpers.


The picture above shows the transverter with the top cover off for the purpose of setting up using the jumpers.  Output power (up to 2W) can also be adjusted here using the trimmer visible on the left.

20170112_083932 Most functions can be monitored using the LEDs at the side.

After purchasing this then discovered that the completed units are stocked in the UK by Kanga Products ( so I could have obtained it possibly faster and cheaper but we live and learn.  I may look at the 13cm (2300MHz) transverter at a later date – also from SG Lab and I will look then to see if Kanga have it first.

Now I am going to build a DW6LP type Yagi Beam for 23cm so I can put the unit to full use.






Making Waves – Fundamentals of radio Antennas part 1

November 19, 2016 Leave a comment

The electrical and magnetic fields radiated from an antenna form the electromagnetic fields, and this field is responsible for the transmission and reception of electromagnetic energy through free space.  An antenna, however, is also part of the electrical circuit of a transmitter (or receiver); and, because of its distributed constants, it acts as a circuit containing inductance, capacitance and resistance.  Therefore, it can be expected to display definite voltage and current relationships in respect to a given input.  A current through it produces a magnetic field and a charge on it produces an electrostatic field.  Thes two fields together form the induction field.

Voltage and Electric Field

When a capacitor if connected across a source of voltage, such as a battery (fig.1), it is charged some amount, depending on the voltage and the value of capacitance.  Because of the emf (electromotive force) of the battery, negative charges flow to the lower plate, leaving the upper plate positively charged.  Accompanying the accumulation of charge is the building up of the electrical field.  The flux lines are directed from the positive to the negative charges and at right angles to the plates.

capacitor_1                                       Fig.1   Charges on the plates of a capacitor.

If the two plates of the capacitor are spread farther apart, the electric field must curve to meet the plates at right angles (Fig.2).  The straight lines in A become arcs at B, and approximate semi-circles in C, where the plates are in a straight line.  Instead of flat metal plates, as in the capacitor, the two elements can take the form of metal rods or wires.  In B the rods are approximately 30 degrees apart and the flux lines are projected radially from the positively charged wire to the negatively charged wire.  In C the rods are in a straight line and and the flux lines form a pattern similar to the lines of longitude around the earth.  To bring out the picture more clearly only the lines in one plane are given.


Fig.2 Electrical field between wires at various angles.

Assume that the sphere marked E in Fig.2C is a transmitter supplying RF energy.  The two wires then can serve as the antenna for the transmitter.  RF energy is radiated from the antenna and charges move back and forth along the wires, alternately compressing and expanding the flux lines of the electric field.  The reversals in polarity of the transmitter signal also reverse the direction of the electric field.

When a charge is put on the plates of a capacitor by means of a battery (DC), an electric field is set up between its plates.  The flow of charge from the source to the capacitor ceases when the capacitor is fully charged and the capacitor is said to be charged to a voltage equal and of opposite polarity to the source.  The charged capacitor can be used as a source of emf since it stores energy in the form of an electric field.  This is the same as saying that an electric field indicates voltage.  The presence of an electric field around an antenna also indicates voltage.  Since the polarity and the amount of charge depend on the nature of the transmitter output, the antenna voltage also depends on the energy source.  For example, if a battery constitutes the source, the antenna charges to a voltage equal and opposite to that of the battery.  If RF energy is supplied to a half wave antenna, the voltage across the antenna lags the current by 90 degrees.  The half wave antenna acts as if it was a capacitor and it can be described as being capacitive.

Current and Magnetic Field

A moving charge along a conductor constitutes a current and produces a magnetic field around the conductor.  therefore, the flow of charge along an antenna also will be accompanied by a magnetic field.  The intensity of this field is directly proportional to the flow of charge.  When the antenna is uncharged, the current flow is maximum, since there is no opposing electric field. Because of this current flow, a charge accumulates on the antenna, and an electric field builds up in increasing opposition to the emf of the source.  The current flow decreases and when the antenna is fully charged, the current no longer flows

The magnetic field in the space around a current-carrying device has a specific configuration, with the flux lines drawn to a definite rule.  Whereas in an electric field, the electric lines are drawn from a positive to negative charge, in the magnetic field the flux lines are drawn according to the left hand rule.  The direction of current flow is upwards along both halves of the antenna.  The lines of magnetic flux form concentric rings that are perpendicular to the direction of current flow.  If the thumb of the left hand is extended in the direction of current flow and the fingers clenched, then the rough circles formed by the fingers indicate the direction of the magnetic field.  this is the left hand rule, or convention, which id used to determine the direction of the magnetic field.

Combined Electric and Magnetic Fields

When RF energy from a transmitter is supplied to an antenna, the effects of charge, voltage and current, and the electric and magnetic fields are taking place simultaneously.  These affects (Fig.3) have definite time and space relationships to each other.  If a half wave antenna is used, the relations between charge and current flow can be predicted, because of the capacitive nature of the antenna.  The voltage will lag the current by 90 degrees, and the electric and magnetic fields will be 90 degrees out of phase.  With no electric field present (no charge), the current flow is unimpeded and the magnetic field is maximum.  As charge accumulates on the antenna, the electric field builds up in opposition to the current flow and the magnetic field decreases in intensity.  When the electric field reaches its maximum strength, the magnetic field ha decayed to zero.

A reversal of polarity of the source, reverses the direction of current flow as well as the polarity of the magnetic field, and the electrical field aids the flow of current by discharging.  The magnetic field builds up to a maximum , and the electric field disappears as the charge is dissipated.  The following half cycle is a repetition of the first half cycle but in the reverse direction.  This process continues as long as energy is supplied to the antenna.  The fluctuating electric and magnetic fields combine to form the induction field, in which the electric and magnetic flux maximum intensities occur at 90 degrees apart in  time, or in time quadrature.  Physically, they occur at right angles to each other, or in space quadrature.  To sum up, the electric and magnetic fields about the antenna are in space and time quadrature.


Fig.3 Electric and magnetic fields 90 degrees out of phase.

Part 2 will follow next week.

Making Waves -Slow Scan TV

October 28, 2016 Leave a comment

One of the good things about the amateur radio hobby is its diversity.  If you begin to become bored with one particular activity there are always plenty of other things to try.  And so I decided to try something completely new (for me anyway) – HF Slow Scan Television or SSTV for short.

I downloaded the mmsstv software from and read through the instructions on setting up.  All very simple really, much like setting up JT65, RTTY or any other soundcard based system/software.  It does come with a few standard templates so I used these for a while until I got my head round the file size and clipping tools to create my own.

sstvscreen fig 1. My transmitted SSTV CQ message and control panel.

I have now made several contacts around Europe and Russia and the variety of images received is quite amazing.  Contrary to popular belief, they are not pictures of nakedness – they are images of nature, wildlife or screen grabs from cartoons.

sp5smy  fig2. Image received at M0CVO from SP5SMY.


Repairs and operations…. M0CVO Radio Blog 24/01/2016

January 24, 2016 Leave a comment

This last week turned out to be an interesting one.  On the 18th (Monday) I was given an old defunct radio – an IC-245.  It is in fact a 2m multimode offering FM, USB and CW and was one of ICOM’s first CMOS controlled radios boasting two VFOs and PLL tuning.  It was also the US version giving me a full 4MHz from 144 – 148MHz.  It looked to be in reasonable condition for a 39 year old set (last made in 1976).  However, it didn’t work.  The screws holding the case together were missing and on opening up I noticed that some wires had been snipped – perhaps it had been an attempt at doing a mod to add LSB or similar that had gone wrong.  Anyway, I repaired the wires but still nothing.  I contacted ICOM UK Ltd and they sent me a new MOLEX type connector for the DC input – this was also missing which arrived the next day.  Tracing the line back from DC in I noted that a small diode was “fused” (well, burnt out).  I suppose the radio must have been connected up the wrong way round at some stage or fed with too high a voltage.  Anyway, I checked in my junk box and found a small signal diode to replace the one that was crisped and tried again.  Presto! we have power.  Unfortunately though, no audio.  Anyway, I plugged a headset in at the back and audio was produced here so the audio drivers were obviously functioning.  I checked the external speaker/headphone socket but this was functioning correctly and switching back on to internal when the headphones were removed so I then checked the internal speaker.  lo and behold one of the wires through the cone was broken.  Anyway, I replaced the speaker with another and audio was heard.  On TX a full 10W was transmitted and the TX audio could be heard in  a second radio so all fine.  So now I have both the FT-480R from Yaesu as a 2m multimode (30W) and an IC-245 from ICOM as a 2m Multimode (10W) but with the advantage of also covering the 146 – 148MHz portion of the band.

IMG_20160122_111129 Inside the IC-245 showing the FM board

IMG_20160122_111253 Inside the IC-245 underside showing the add on SSB board.

IMG_20160122_105740 replacement speaker IMG_20160121_140859Operational

So what else of my week? Well although I have been rather busy this week with work I have also found some time to get on the air and was lucky enough to find an opening on 15m yesterday that enabled me to get LZ1012SGM into the log and earn 10 points towards a diploma.  I also managed to get Z62FB (Kosovo), 3Z90LKK (Polish club celebrating 90 years and offering points towards diploma) and Z63MES (Kosovo).  This morning I noted that there was a CW contest so I gave away a few points to some Russian stations on 20m.

QRP 365 Update 51

December 20, 2015 Leave a comment

It’s Sunday December 20th 2015 and I have now completed week 51 of my QRP 365 Challenge.  For those who are new to this, this means that for the whole of the year, 2015, I shall use no more than 5W and just CW or Datamodes, no phone at all.  At least one QSO a day – hence 365.

So how did I do this week?

13/12/15: OF9X, 5W, CW on 10.124MHz, a distance of 1309mi (2112km) / 261.8mi (422.4km) per Watt.

14/12/15: T77C, 5W, CW on 14.023MHz, a distance of 858mi (1384km) / 171.6mi (276.8km) per Watt.

14/12/15: S51Z, 5W, CW on 14.023MHz, a distance of 854mi (1377km) / 170.8mi (275.4km) per Watt.

15/12/15: G3MCK, 5W, CW on 7.025MHz, a distance of 22mi (36km) / 4.4mi (7.2km) per Watt.

16/12/15: HB9DAX, 5W, CW, on 14.060MHz, a distance of 573mi (924km) / 114.6mi (184.8km) per Watt.

17/12/15: IZ6TGS, 5W, CW on 14.043MHz, a distance of 956mi (1542km) / 191.2mi (308.4km) per Watt.

18/12/15: F5URG, 5W, PSK31 on 14.07015MHz, a distance of 430mi (694km) / 86mi (138.8km) per Watt.

18/12/15: UE56N, 5W, CW on 7.018MHz, a distance of 1851mi (2985km) / 370.2mi (597km) per Watt.

19/12/15: DG2PHE, 5W, PSK31 on 14.07015MHz, a distance of 501mi (808km) / 100.2mi (161.6km) per Watt.

20/12/15: UA3IQC, 5W, JT65 on 14.076MHz, a distance of 1851mi (2985km) / 370.2mi (597km) per Watt.

As can be seen, the best distance worked this week was with 1851mi (2985km) and this was shared between two Russian stations – UE56N(40m) and UA3IQC on 20m.  However, the winner for the best QSO has to go to OF9X (Old Father 9 Xmas). After all, how often do you get to have a QSO with Santa using CW?

An interesting and enjoyable week using different modes – CW and PSK – to obtain several countries.  Only 2 weeks remaining now and then we will be into 2016 and I shall be drawing up conclusions of this year’s experiment.


Wishing all my readers a Merry Christmas 2015 and a Happy New Year 2016.

Until next update..

Next update will be on Sunday 27th December 2015.

QRP365 Update 50

December 13, 2015 Leave a comment

It’s Sunday December 13th 2015 and I have now completed week 50 of my QRP 365 Challenge.  For those who are new to this, this means that for the whole of the year, 2015, I shall use no more than 5W and just CW or Datamodes, no phone at all.  At least one QSO a day – hence 365.

So how did I do this week?

07/12/15: OK2RN, 5W, CW on 14.026MHz, a distance of 722mi (1164km) / 144.4mi (232.8km) per Watt.

08/12/15: IZ5OVP, 5W, CW on 14.025MHz, a distance of 953mi (1537km) / 190.6mi (307.4km) per Watt.

09/12/15: RU3ZL, 5W, CW on 14.015MHz, a distance of 1851mi (2985km) / 370.2mi (597km) per Watt.

10/12/15: 9A90IARU, 5W, CW on 14.024MHz, a distance of 911mi (1470km) / 182.2mi (294km) per Watt.

11/12/15: RA3ZF, 5W, JT65 on 14.076MHz, a distance of 1851mi (2985km) / 370.2mi (597km) per Watt.

12/12/15: OM7LW, 5W, CW on 14.033MHz, a distance of 922mi (1487km) / 184.4mi (297.4km) per Watt.

12/12/15: RU6AV, 5W, CW on 28.008MHz, a distance of 1528mi (2464km) / 305.6mi (492.8km) per Watt.

12/12/15: RY6Y, 5W, CW on 28.026MHz, a distance of 1851mi (2985km) / 370.2mi (597km) per Watt.

12/12/15: LZ4TX, 5W, CW on 28.023MHz, a distance of 1363mi (2199km) / 272.6mi (439.8km) per Watt.

12/12/15: RK3ER, 5W, CW on 28.023MHz, a distance of 1851mi (2985km) / 370.2mi (597km) per Watt.

12/12/15: RV3FF, 5W, CW on 28.029MHz, a distance of 1851mi (2985km) / 370.2mi (597km) per Watt.

12/12/15: ER4A, 5W, CW on 28.014MHz, a distance of 1339mi (2159km) / 267.8mi (431.8km) per Watt.

12/12/15: US8IM, 5W, CW on 28.023MHz, a distance of 1454mi (2345km) / 290.8mi (469km) per Watt.

13/12/15: US2MT, 5W, CW on 14.019MHz, a distance of 1454mi (2345km) / 290.8mi (469km) per Watt.

As can be seen, the best distance worked this week was with 1851mi (2985km) and this was shared between three Russian stations – RU3ZL (20m), RA3ZF (10m) and RY6Y (10m).

The seven QSOs that I managed on 10m yesterday were during the ARRL 10m Contest, which I believe is still running until 2359 today.  Although I am not actively taking part in this contest and will not be entering a score it was interesting to see how much activity there was on a band that is for all means rather dead most of the time currently.  Love them or hate them, at least the contests keep the bands alive.

An interesting and enjoyable week using different modes – CW and PSK – to obtain several countries.  Only 2 weeks remaining now and then we will be into 2016 and I shall be drawing up conclusions of this year’s experiment.


Circuits become so small – this is a silicon oscillator (UHF) on a chip. The penny is for size comparison.

Until next update..

Next update will be on Sunday 20th December 2015.