As I have stated previously I purchased a 1296MHz transverter from SG-Lab in Bulgaria. Anyway, upon applying power to it and testing the transmit (with an IF of 145MHz at 2.5W from my FT-817) I noted that it was not working as described. Upon opening up the top of the case I noted that one of the components was raised and obviously burnt. I contacted Hristiyan, LZ5HP, at SG-Lab and sent photos of the faulty component in situ. He immediately identified it as a short in the choke having caused the problem and I returned the unit to him. Two weeks later it was back with me in full working order with a replaced choke. This time when I applied power and some IF it worked as it should.
I also mentioned that I would look at constructing a DL6WU Yagi but, unfortunately, work has got in the way and I just haven’t had the time. I looked online for suppliers and, after much deliberation, decided to purchase one from Dual Antennas in Serbia (www.antennas-amplifiers.com). This was down to both price and quality. Although there are manufacturers both in England and in Germany, Dual seemed to offer the best deal. For a 13 element Yagi it cost me 59€ plus shipping. there was the other issue that when it arrived in the UK it was held by customs for a week whilst they added import charges and VAT but that only came to £19.15.
The 23cm Yagi from Dual.
So now I am fully operational on all bands from 80m – 23cm (except 4m currently). I have not yet had a QSO on 23cm although I have put out a few CQ calls, so maybe next Thursday evening during the UKAC contest.
The 23cm Yagi up at CVO Towers
The transverter visible in operating position below the X1M HF QRP set with the FT-817 providing the IF to the left.
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 http://sg-lab.com/amateur.html 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.
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 (www.kanga-products.co.uk) 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.
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.
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.
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 http://hamsoft.ca/ 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.
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.
fig2. Image received at M0CVO from SP5SMY.
Something new arrived in the postbag the other day – an Alinco DJ-G7 three band handheld transceiver. Operating on 2m (145MHz), 70cm (433MHz) and 23cm (1296MHz) plus a wide RX scanner from 0.53MHz – 1299.995MHz although it is bblocked on the cellular/mobile phone frequencies for obvious privacy reasons.
Anyway, I unboxed it, fitted the battery (Li-Ion) the hand strap and belt clip and turned it on to see what it could do. Obviously, the battery wasn’t fully charged so any transmitting would have to wait but, on tuning through I did manage to pick up some nearby PMR stations which seemed promising. It also came with a nice desktop charger which I made use of and was surprised at just how fast it charged the battery. The manual states that using the supplied charger the battery can be charged from flat in 3 hours, I made the initial charge in about one.
Personally I live in a very bad place for VHF amateur radio, let alone UHF so I was pleasantly surprised when I sat the DJ-G7 on the coffee table the next morning, scanned through 2m and voices suddenly erupted from the speaker. It was G4VUA (Alan) from the next village running a local(ish) net. I picked up the set and called in and, lo and behold, he replied to me. Not bad from a little handy sitting in the living room. All things considered though he does have an advantage of height above me.
Anyway, how clean is the signal? I tuned it to 1.2965Ghz and with only the supplied rubber antenna fitted, checked the output against my spectrum analyser. The results were spot on – a lovely clean signal with no harmonics detected. Well done Alinco – this one looks like a winner.
Moving on to other matters, conditions both on HF and VHF have improved of late. There have been numerous sunspots appearing and this has led to some late summer sporadic e propagation on both the higher HF bands (15, 12 and 10m) and the VHF bands of 6, 4 and 2m. I suppose this was ideal for this weekend which was the Worked All Europe DX Contest. However, myself, I made a few CW contacts with EO25UA, EO25UD, ZS9AZ and EM25HQ to name a few. I also collected a few contacts on JT65.
Also, a friend of mine – Stefan, DO2JAX, has been operating from a holiday location as OZ/DO2JAX. After a week I managed to work him yesterday on 14.317.5MHz. H ewill be active from this location until the 19th August so, if you hear him, give him a call. He is only operating SSB but can be found on all bands at different times.
Till next time.
73 DE M0CVO
Due to one thing and another it seems that I have not had a lot of time on my hands to do much radio activity for a while. The sun was spotless for some time during the month of July and conditions on HF literally bottomed out. Luckily this all seemed to change in time for the IOTA Contest on during the weekend of 30 – 31st July. Suddenly there were spots on the sun a decent MFI and all bands opened – right up to 2m. There were intercontinental contacts to be had throughout the HF bands up to and including 10m (28MHz) and quite a few 6m hops although these were probably more down to sporadic e’s rather than multi-hop F2 Layer propagation.
Anyway, during the month I have been experimenting with antennas for 23cm (1297MHz) and 13cm (2321MHz). I have looked at various designs from the double quad antenna, More details of which can be found HERE to the slot antenna, which can be read about Here and the IFA Patch Antenna, which you can read more about HERE. I finally settled on a version of the IFA antenna as this was easy to etch onto a piece of single sided PCB with an FR-4 backing.
Using MiniVNA Tiny to determine properties of 23cm IFA Antenna.
Once I was happy with it I 3D printed a case for the antenna to fit into and checked that the VSWR readings remained below 1.5.
IFA Antenna in 3D printed case.
I also looked at the Vivaldi antenna details of which can be found HERE which would make an interesting broadband antenna that could be used to feed a dish, but decided against it at present.
On Friday 26th July I was lucky to receive notification that I had won a pair of RF Solutions LoRa modules in an online competition. I promptly received these on the Saturday and set about trying to work out what to use them for. They are effectively a voltage controlled pair of transmitters/receivers and can be encoded to work as remote controls, provide remote networking, remote switching or act as remote sensors. The range is up to 16km using spread spectrum technology at 868.5MHz.
The RF Solutions Ltd Gamma LoRa pair
I am currently experimenting with them as a remote wireless sound activated switching system. More details on this at a later date.
Sound Activated wireless switch..
I read with interest a letter in the latest issue of Radcom entitled “HF Conditions – If only!”. In it the writer laments over the lack of DX opportunities available on a daily basis as compared to how it was when he was an SWL 40 – 50 years ago. I could also speak of similar things. When I got my 1st licence in the late ’90s (VHF only B licence), we were at the peak of Solar Cycle 23 and 144MHz was like 20m is nowadays and there was always DX to work. When I took the 12wpm CW test and got my current HF licence in 2000 we were still being blessed with excellent HF conditions and I managed to work amazing DX suing just a base loaded magnetic mount antenna for 15m sat on top of the ATU inside the shack – at night too! The peak of solar cycle 24 was nothing to write home about though and the peak has now passed.
The above two graphs represent Solar Cycle 23 and Solar Cycle 24 for comparison. It can be seen that at the peak of cycle 23 (2000) we had a daily sunspot count of approximately 120 whereas at the peak of cycle 24 (2014) the daily sunspot count was closer to 80. The lower number of sunspots results in more coronal holes in the sun which lead to masses of plasma being ejected towards the earth, resulting in more geomagnetic storms (aurora). This in turn gives rise to some enhancements in VHF (50MHz, 70MHz) but poor conditions on HF.
Looking back further to Cycle 22, it can be seen that the peak was even higher with a daily sunspot count above 150. If this trend continues could it be possible that we are heading for another Maunder’s Minimum where there will be no peak for the complete cycle? Will this mean a total flattening of the HF conditions? It certainly would spell bad times ahead for the higher HF bands above 18MHz. Fingers crossed it won’t come to that and our local star will become a little more active at it’s next cycle peak in 2020/21.