Icom appears to delight in charging outrageous prices for all transceiver accessories, so many Hams improvise instead. A few circuits have been published for CI-V interfaces, most of which use the MAX232 IC. Here is a very simple CI-V interface, originally described by OK2WY . I’ve made small changes to the modem control signals connections. Although the circuit doesn’t conform exactly to the RS-232 specification, it does work well and has the advantage of being easily constructed inside a 9 pin D-type shell. Please note that the resistor value 4K7 means 4700 ohms. The transistor types are not critical, I just happen to have plenty of 2N2222As.
Continue readingGAP Titan DX Maintenance
I’ve installed the GAP Titan DX some years ago. Due to maintenance works on my roof, I had to put the antenna down for some weeks.
This week I’ve been able to restore the antenna on the roof. The Gap Titan DX is a vertical dipole with no traps, and with vertical elements making this antenna resonating on from 12 to 30 meters. 80 meters provided from a top capacitor, while 10 and 40 meters depends on the tuning of a cross shaped counterpoise at the base of the antenna.
I’ve already written several times about this antenna and how to tune it on several bands providing also a quick antenna reference you can seen here behind.
According to some OM there is a relation between the 20 meter stub and the 40 meter copper wire length.
Well, today after having restored back the antenna on the roof, I’ve not been able to obtain an acceptable SWR on the 40 meters.
With acceptable I mean SWR < 2.0 on the band. According to GAP this antenna shoud be able to perform well with acceptable SWR on all bands, but in the 10 years I’ve on the top of my head, it never performed on the 30 meters. SWR on 10 MHz has been always > 3.5.
Continue readingWonder Whip Antenna
The Wonder Whip?
A £10 QRP Portable Multiband Antenna for HF, VHF and UHF
A variation on the “Miracle Whip” and “Wander Wand”.
The Wonder Whip
Florence RadioFest 2019
on Saturday 25 May 2019 i will take part to the upcoming Florence RadioFest as organizer.
The Florence RadioFest is a local amateur radio HamFest managed by the members of the ARI Section of Florence.
We expect to have over 50 private amateur radio oeprators and more than 10 amateur radio business companies represented.
Quarter Wave Vertical Antennas
and how they operate
One of the most useful antennas in the repertoire is the
Marconi or quarter wave grounded vertical antenna. Its invention made
it possible to halve the length of antennas, simplifying communications,
especially at HF and below. This antenna is still used widely today,
especially in marine, land mobile and long distance communications. It
can offer excellent performance when installed well. There are, however,
a number of selection criteria to take into account before you buy…
Long Waves, Short Antennas
designing for MF and LF communications
When radio began, it started with low frequency communications, which it was thought was the answer to long distance communications. Since then we have seen the development of sky wave communications on HF frequencies, followed by the proliferation of communications system using the VHF and UHF direct wave and microwave. It may be thought by some that low and medium frequency communications are somewhat outmoded, but in reality they are still very much in evidence today…
Feeder Radiation
Striking a Balance
When you connect centre fed antennas, like dipoles, Vs, triangles, yagis, rhombics, loops and so on, to coaxial cable, unless care is taken, it is not difficult to end up with feeder radiation. Not only can the loss in power be quite significant, but the radiation characteristics of the antenna system will also be seriously compromised.
Continue readingFolding the Dipole Antenna
Invented by Heinrich Hertz in around 1886, the half wave dipole is still one of the most simple and practical of antennas and still very much in use today. It consists of a half wavelength long centre fed conductor. Since these early days, improvements have been made to the initial design by adding a second, and often a third conductor, joined at the two ends to form a loop. This antenna, known as the Folded Dipole, can provide improved performance over the single wire antenna when well designed, constructed and installed…
Continue readingUsing Solar Power and 12 Volt Batteries
The Sun Can Power Your Ham Station and a Whole Lot More!
Solar power or specifically, solar photovoltaic (PV) panels, have become increasingly available as a power source. Solar PV is ideal for powering Amateur radio equipment because PV panels are almost always designed to charge 12 volt battery systems. Coincidently, most Amateur radio equipment is designed to operate from 12 volt power supplies.
Continue readingMagnetic Longwire Baluns
Do these things do exactly what they say they do – or are they total hogwash?
Have you seen the ads? This device will match your long wire to your receivers 50 ohm input? Firstly a long wire on HF would be on 28 MHz longer than 120 foot and on the lower bands it just an end fed “EF”
We can also get rid of the “magnetic” and give the balun its true name of voltage balun. My interest in the MLB was started after a friend went out and paid ?30 for one and started to tell me how this little device will produce a 50 ohm match at all frequencies. Any aerial will have differing values of impeadence depending on what band it is used, a 66 foot wire on 80m is about 30 ohms and on 40m the impeadence is about 1000 ohms.
For any sort of balun to be able to match different impeadences to 50 ohms you need to be able to vary one or more of its components. And when you can do this, the balun will match most things to 50 ohms, but you would call this type of balun an ATU. An ATU is a variable balun.
But theory is one thing and practice is another. So mainly for some thing to do I decided to make some MLB’s and see what mystical properties they have. The first balun was made “by the book” using the correct wire SWG and ferrite ring with a type 63 core for 1 to 30 MHz. I used a friend’s MFJ analyser for the tests and a 35 foot wire aerial.
The balun did improve the match to the receiver. Only near the resonant frequency of the aerial was any match close to 50 ohms or a VSWR of 1 to 1, as you would expect. On all other frequencies the match varied from 3 to 1, to 5 to 1 VSWR. Without the balun the match was horrible!
In the real world this means I had some thing like a increase of signal from 1 to 4 “S points” on the receiver from 1 MHz to 30 MHz.
The “VMR version” MLB was made from scrap. 3 core 2 amp lighting flex and an old ferrite rod. The results are just the same as the posh version!
You need about one yard of 3 core, 2 amp flex and a ferrite rod with a length of about 6 inches or longer.
Using 3 core flex it is easy to wire because it is colour coded. Tape one end of the flex to the rod leaving 6 inches for the connections, then wind on as many turns as possible (mine has 10 turns) and again fix the wire with tape etc at the other end. Now you can just twist the wire connections together or better solder them. Connect it up as shown. Blue right hand side to Green left-hand side. Brown right to Blue left. Inner of COAX, to Brown/Blue. Braid to single Green. Aerial to single Brown. Then just bung it into a box.
So is a MLB worth having? They do produce a “better” match to the receiver but you could get an ATU kit for about the same price, which will always produce the right match. If you buy surplus VC’s you can make an ATU for under ?10. Find a couple of broken tranny radios and you can make one for free.
The main advantage of the MLB is you can use COAX to the feed point of the aerial out side and get a reduction in noise pick up from TV’s etc in your home. I would not spend money on one, but a home made MLB in a box is worth having. Because it is a pain to keep peaking the ATU as you tune up the SW bands and anything that helps to give a better match is better than having nothing at all.