VK5JST Antenna Analyser
Having puddled around for ages with antennas wondering how to design and adjust them, I’d decided I needed some instrumentation.
There have been a series of articles recently in Break-In (the http://www.nzart.org.nz) and also one from Australia about antenna analysers. Having digested the maths (which is really cunning), I now understood enough to design one myself, but that was patently silly as it’s be yet another case of wheel- reinvention, so I got out the plastic and ordered the antenna analyser designed by VK5JST and now supplied by the South Coast Amateur Radio Club
http://www.scarc.org.au/projects.html.
It’s a complete kit including case for AU$140 (about US$120) and while I have a well stocked junkbox, there always seems to be one or two bits that are missing …
This is just a placeholder page – I’ll add some photos later, but here are some of the links that I want to remember:
####How is it?####
It works well (once I’d figured out that the PN2222 transistors – just to be perverse – had pinouts opposite to both the datasheet and component overlay).
I’ve installed the VK3DPM software upgrade so now it measures C & L as well as R/Z/SWR – very pleased :-)
The opposite pin-out transistors were a bit hard to find. I knew the amplifier Q11-Q12 was the problem as when I disconnected them the voltage driving them was very flat with frequency whereas when Q11-Q12 were connected the output fell off badly with increasing frequency. The puzzling bit was that the components were all correct and so were the DC voltages (more or less).
I’m really grateful to VK3PE on EHam.com for mentioning his problem with the PN2222.
Now I’m just tweaking the accuracy …
####Related Links####
VK5JST’s own page on the analyser
http://www.users.on.net/~endsodds/analsr.htm
The reviews on EHam.com – these are what convinced me to buy it, together with the fact that the project is based on the PicAxe microcontroller which is programmed in Basic so there are lots of user contributed software updates.
**Mods to increase frequency range and accuracy:**
http://members.optusnet.com.au/dpmilne/Amateur_files/AntennaAnalyser/HW_Mods/VK3XPW/VK3XPW.htm
A Russian page (no idea what it’s about but there’s lots of words and following discussion – included for completeness):
http://www.cqham.ru/aa_VK5JST.htm
Hi, what were the symptoms of your analyser not working with the pn2222 problem? I found lots of confusion with mine, and its still not working. All my voltages and cro tests are correct, but my lcd characters remain as black squares.
Any tips appreciated thanks,
Adrian
Hi Adrian
The LCD characters being black square won’t be the PN2222 being in backwards – my display was blank until I remembered the CONTRAST control and then all was revealed.
The symptoms of the PN2222 being in the wrong way around was really low output from the amplifier and a really fast drop off in output with frequency. The documentation states that the -3db point of the power amp is 70MHz so there shouldn’t be a roll-off happening at 14MHz which mine had.
Cheers Giovanni
Hi I’m just started to built the analyser, I was wondering how to change the basic prog to put my callsign or and name on the lcr at say boot up time ?
I see there is a ZL that has modded it again is this worthwhile?
Dave GM3WIL
Hi Dave
I found I preferred the variant of the software that included the LC functions on power-up to the ZL2TTM version which worked well but the display is a little harder to read and the angular info didn’t seem (to me) to help much.
Regarding displaying your call – should be hard – just another print statement (from memory there’s room for the code).
It’s much easier if you build the programming cable (not difficult – two resistors onto the PCs serial port pin). The resistors are already installed so you only have to add a 3.5mm stereo socket to the analyser and then wire up a 3.5mm stereo plug to a DB9 socket (analyser to PC) cable. Not hard, but be careful to wire it the socket the same way as described in the Revolution Education PicAxe manual. The way they’re arranged the pins seems unnatural (ground isn’t the sleeve of the 3.5mm plug) but it what get’s connected to what was you plug it in doesn’t do any damage (anyway that’s my take on way the plug wiring is “odd”).
There’s a very clear diagram of how to wire the programming cable on page 31 of the PicAxe manual at http://www.rev-ed.co.uk/docs/picaxe_manual1.pdf
I was fairly paranoid about checking the connections from the DB9 to the socket and then to the PicAxe as while the Analyser PC board has the programming resistors installed and three pins for a cable, the actual connections aren’t detailed in the documentation.
Just be careful – the flexibility to be able to reprogram the analyser by just plugging in a programming cable is well worth an hour of paranoid checking. Then you can try all three versions of the software in a few minutes without even opening the analyser …
Cheers
Giovanni – ZL2BOI
Well, just Had a look at the Q12 Q11 transistors and the PN2222 transistors I have are PNP? yet on the circuit the are shown as NPN?
very confused!
Can I programme the PIC with the unit patially assenbled ,Ie No other chips in and not aligned? I have tried this and found my serial port is regognised but the programmer is not and is all greyed out That is with 12v applied to the board,
Is the Prog I use one called Progedit The one with the little PC Icon?
I can’t see on that one how to sellect the 28X1
Dave
Just checked again they are NPN sorry connections are fine, that’s them in
I just discoved that I could use a computor sound cable for a CD player fits perfectlty on to the PCB serial interface
Thanks for the tip about CD sound cables – I have several and they’re easy to get – visit your local PC Store.
About programming with the unit only partially built – personally I wouldn’t. Get it going as supplied, otherwise if it doesn’t go you don’t know whether the programming didn’t go well or what.
You can find the 28X1 on the View Menu/Options/Mode Tab.
Ok Giovanni, I also want to use a bigger LCD screen as my arms are not long enough these days to see small sceens, I’ve loaded the sofware ,but I don’t know if it is OK it reports back that about half the memory is used.
I used the send option on the programme to put the prog in
Dave
Dave – It also reported half the memory empty (left) when I upload new versions so it all sounds good.
Does the display show anything sensible?
I hadn’t realised before I assembled it that the little row of wires from the LCD to the main board is a tight fit. I was going to put sockets and use ribbon cable but the 1cm long (or thereabouts) row of wires provide quite firm support for the display.
Giovanni, I haven’t got my LCD yet and I’m short of transistors the PN3563 and the monolithic decoupling capacitors I also need the little wheel for the variable capacitor ,don’t know where I’ll get one.
I’m really keen to try it all out I’ve even tried to put my Callsign in it might even work.
I will just need to wait.I’m not kit building, it is all from scratch.
I have used ribbon cable on the PCB side and that should allow mw to move it to where It looks best
I have other projects like the ARDF 80 Metre Transmitter qrp 4 watt TX
This is the second one I’ve made I need to built a small ATU inside it
I thought a loading coil and a Parrallel 300 pF capacitor to ground so It will tune a 4 metre length of wire
73 Dave
Hi , I’ve got all the components now , i’ve opted for a bigger LCD screen .I did find a source of the tuning wheel. an asprin pill container top ,cut down ,works well.
got some help with the software statments, it now boots up Dave GM3WIL, it is all starting to work now …really chuffed .
Dave
I’ve just finished the Aerial analyser and I can tell you it works, very well .although I do miss the analogue meters of a MFJ .
It is a lot cheaper and works just as well if not better than the MFJ259 .I used a larger LCD module as my arms are not long enougjh these days to focus,