Sunday, 30 August 2015

AD9850 DDS module and controller working

After successfully getting the DDS controller PIC and its 2 line LCD up and running yesterday, today I rejigged the breadboard to fit the AD9850 DDS module on. The PIC talks to this via an SPI serial bus, and the module gives two square wave and two sine wave outputs at the programmed frequency.


At first, it seemed that it would only give the right frequency above 14MHz! Anything below becoming progressively more inaccurate, until around 5MHz where it was all over the place!


After a nice hot bath, and a bit of a think, I went back and gave the frequency counter a bit of a kick! I realised it was the counter that was playing up, not the DDS module! A bit of fiddling with the input ports, the range switch and the trigger level and I proved the output of the DDS on all the controllers 'standard' frequencies, which are all within the amateur bands, this including 500kHz and 137kHz!
I just need to add the encoder now and some real buttons!

Saturday, 29 August 2015

DDS controller LCD working

After a bit of faffing about, I managed to find a datasheet for the 16x2 LCD I currently have. From this ive been able to completely rewire the ribbon cable connecting to it. But the trouble didnt end there!

At first, thinking I had it properly wired to the PIC, my PSU went into short circuit protection! Oops, clearly something isnt right. It turns out that every connection number has the same function on this LCD as on a standard module - except pins 1 and 2, GND and Vss on a standard, are reversed on this one!

That sorted out, it still wouldnt work, and the PIC began to get hot! Oh dear. So, I pulled the whole lot of connections off, and refitted them again one by one, to ensure whichever incorrect pin I had didnt happen again. My reward for doing so was a working LCD! Next step then is to find an encoder (or wait for the one coming from the Far East) and get the control inputs working. Once happy with the inputs and the display, i'll add the expensive part - the DDS module itself!

Ive also today ordered some 16LF84A's for some older PIC projects, and some 12F683's to experiment with. The 12F683 is an 8-pin 8-bit MCU, but is non the less a remarkably versatile and powerful little device! With on board A/D, some amazing low power options, a huge array of timing and clock options, and PWM capabilities.

Friday, 28 August 2015

Clocking on

A few spare moments today allowed me to breadboard the PIC LCD clock.  Although I didnt include the setting buttons, instead using a flying ground lead to pull down the appropriate pins. The first PIC programmed on my PICkit2 worked just fine.


Even this circuit is overkill on a PIC! Theres a 4MHz crystal there, plus 2x 22pF caps - the PIC 16F628A can do all that internally!

So now I have a known working programmer, I can check out the rest of my LCD modules, and ive moved onto breadboarding the AD9850 DDS module controller. I'll test the LCD drive and memory store/recall routines first, then add the encoder, and finally the DDS module itself.

Im looking into maybe buying a Clansman PRC-320 HF manpack of my own, and one of the things I would be doing to it is adding an external VFO and frequency display system!

A big problem I have though is that out of my selection of LCD modules, I have only one 16 x 2, and no 4 line modules. The controller project specifies a 4 line module, but will work with a 2 line unit. The trouble is, my 2 line x 16 character module has a non-standard pin-out, and I cant get it to work with the DDS controller code.  Ive tried the DDS code against one of my 16x1 single line displays, and it does display the frequency (or rather, what the chip thinks the frequency might be, with neither DDS module nor encoder attached!). So, ive ordered a few various LCDs and an encoder from China.

PICkilled?

Oh dear! After successfully reading the data fill of a previously used PIC 16F628 last night, the programmer then refused to see the chip! Nothing I did could get the PICkit2 to detect the IC again.

This morning, I found out another device, this time a 16F628A, and successfully wrote and verified a fill to it. The original chip still refuses to be detected. Possibly I killed it faffing about last night trying to find the correct location for it on the ZIF socket, and exposing various pins to the programming HV. I cant rule out an iffy programmer at this stage though.

Next step then is to test the newly programmed chip. The code ive used is for an LCD clock. I'll be using one of the LCD modules I got from Finningley rally, to which ive just added a row of SIL pins. No easy feat, as the damn holes wouldnt clear of old solder. Hopefully, this will prove both the programmer and the LCD!

Thursday, 27 August 2015

Can you PIC it? Yes you can!

After the disaster that was my previous K150 PIC programmer, I opted to order a clone of the Microchip PICkit 2 ICP device, and a ZIF adapter for it.To test this out now its arrived, I found out a previously programmed PIC chip, which I know contains code for a CTCSS generator.


A few little teething troubles to start with. First, the actual style of USB connector on the PICkit2 fooled me, and I tried them all before finding the right one! But I was rewarded by the PC finding the driver, and by the devices power light coming on. So far, so froody. Next, I had to find software that would interface with it. None of the programming packages I had installed would see it, which was worrying. A perusal of the unmarked CD that came with it led me, via a swim through a sea of Mandarin, to a copy of the PICkit2 software. With this installed, it sees the device! Yay! It tests the device ok - another Yay! So I attached the ZIF adapter and installed the chip - another yay? nay!

It took me quite a while, and a lot of head scratching, to fathom out exactly where in the ZIF socket the chip was supposed to sit. In the end, it turns out its one place left from the far right hand side! And theres three jumpers to set correctly as well. With this worked out, I told the programming software that it was a 16F628A chip and hit read... the programmer tells me "No 16F628A detected - Found a 16F628 Instead", but it still makes me go and change the selection myself!

But, that done, and it read the chip, and verified it. So im pleased that its working at this stage. Next step is to find a simple bit of code, say an LCD message display, blow the chip with it, and test it on the breadboard. Once im happy its all working, I can start doing some of those PIC related jobs ive had hanging about.

Another correction to a previous disaster, the demolition of my antenna coil, has had me order a nice shiny new coil all the way from Canada. Im hoping that this 21uH coil will let me build a 20m Bugcatcher mobile antenna, and then allow me to find tapping points to match 17m, 15m, 12m and 10m, oh and perhaps 6m too. It has two sides with alternate indented turns, which will make tapping easier, so long as the ideal tap points are on those sides!


But this might have to wait a bit. Ive yet to test the satellite beam on air, and this is the priority as far as antennas goes.


Monday, 17 August 2015

High Pass Filter Blues

Ive just found a moment to throw the newly built diplexer onto the spectrum analyser to see how it actually performs. Heres where the advantages of having the matching tracking generator show themselves!

The 2m Low Pass section performs just as would be expected, cutting off at about 230MHz.

Sadly, the 70cm High Pass Filter section cuts off at 138MHz! Hmmm, I think that might be a tad too low! I'll have to have a play with it tomorrow and see what needs to be adjusted to get the cut-off to match that of the Low Pass section. Having only three components - two ceramic 4p7 caps and a air core coil, it cant be that hard to adjust!

Sunday, 16 August 2015

Antenna Gains and Losses, And Finningley ARS Rally

Today, at 06:00, I loaded my car with a fine selection of vintage and surplus components and modules (or junk, as Julie describes it) and headed off to Sandtoft for the FARS Rally. Turnout today was good, a few more traders than last year it seems, and more visitors. And, unlike last year, the sun shone all day!

Sadly, neither of my two assistants could make it. This meant that apart from before the door was open to the punters at 10:00, and after everyone had gone and most of us were packed up (around 14:00), I couldnt leave my pitch, and therefore had very limited spending opportunity! In the end, not counting the cost of a cheeseburger (no hot drinks as i'd taken a flask of coffee!) I only spent a fiver! That got me a vintage roll of solder (but nice and hefty, for a quid!), three antenna whips, two 16x2 LCD modules (the 'valuable' parts, according to the organizing genius Kev) and a small plastic box with three BNC connectors - more of that later!

I wont talk profit on here, but suffice to say I made enough to cover costs, and to consider purchasing now a dew heater for my camera lens!

But the rally hasn't been the only thing going on. Bob M1BBV asked me if I would make him an antenna for 6m FM for SOTA use, in exchange for some camping equipment. A bit of a think and I settled on an end fed half wave design. Using one of my 5m telescopic fishing pole blanks, and some RG-58, I knocked this up in a couple of hours. A piece of PVC pipe with 13t of coax on forms the balun, which is slipped over the pole, and the end of the antenna has a string which is tied to the poles end piece eyelet. This means it stays vertical when extended


A bit of steady trimming and the match was brought to close to 1:1 at the FM calling channel.



 Of course, such an antenna for 6m is pretty long! It doesnt all fit in the photo above! But at least this antenna project was a success. My attempts to build a 20m and up mobile antenna of the 'Bug Catcher' design, unfortunately ran foul of my personal muppetry, when I attempted to remove excess enamel using a wire brush wheel


and thats the end of that coil! On a plus note, i've got the balun for my Cobweb housed into a nice IP rated box. Some silicone is still needed, but theres no rush


So, what about that box from the rally? Well, when opened up, I found this


So out that bit of coax came! In its place, went a VHF Low Pass Filter, and a UHF High Pass Filter, collectively, known as a Diplexor. Although not intended to handle more than a few watts, this means that I could use my tape measure satellite antenna with a dual band radio


With the glues now set, it was today time to work out how to attach the two parts of the tape measure antenna. Really, this is three antennas in one - a VHF/UHF satellite dual band antenna, a 2m SOTA beam, and a 2m ARDF antenna. This means that the UHF section should be a snug fit, but easily removable when just the 2m antenna is needed. The solution to the problem of mounting the UHF antenna onto the VHF boom was solved with another bit of the smaller tube, some more glue, and two holes


Each boom end has a hole drilled of 12mm diameter. An inch length of the thin tube inserted into the UHF boom hole, and secured with glue. The hole in the VHF boom carefully sized to be a snug but not tight fit for this, turning it into a locating lug. A reusable cable tie attached to the UHF boom at the point between the two coax baluns allows the two booms to be secured together.
And the final photo shows my assistant Sam holding the completed antenna


Next step then is to test it in combination, and then have a go at working through SO-50!

Thursday, 13 August 2015

Astrophotography during the Perseids

OK, so not quite amateur radio or electronics, or is it?

Last night myself and Sam stayed up late and camped out to watch the Perseids meteor shower. The best of which seemed to come just minutes after we started observing at about 22:00 and in fact before the sky was fully dark. We saw some excellent meteors, including one that Sam sadly missed that left a very long lingering smoke trail.

At about 23:00 I started the SLR taking 30sec 18mm f/3.5 ISO1600 exposures, with a 15sec delay between each. Out of around 90 shots, three show definite Perseid meteors. One of them actually might show two - but something knocked the camera during exposure! It also has three satellites in that shot!

The picture above is the clearest Perseid captured. Sadly my skies are not as dark as i'd like them, and at 30sec the light pollution from sodium vapour street lamps is making itself known. This frame is centered roughly on the constellation of Cygnus, which nicely exposes the galactic plane.


Now, have a look at the photo above, another meteor? No, this one appeared in three consecutive shots - its a satellite! If you look very closely at the lower right, you'll see another traveling bottom right to top left of frame. This could be the tenuous link to amateur radio - which satellite is it? Is it an OSCAR? Maybe later I will check the photos metadata for the time, and see what satellites might have been visible


And this one, is that a satellite? It looks more like a meteor! But its neither! This also appeared in consecutive shots - its a tumbling spent rocket body! One thing I forgot to account for though was dew formation, so ive rather a lot of shots that are unusable because the lens fogged up!

So many people never look up more than a few feet over their own heads! And yet there is all this to see, if you just take the time.

So, in just a couple of hours skywatching we saw meteors, satellites, rocket bodies, stars and constellations, and a wonderful view back into the heart of our own galaxy. Add that to a good karate session, a beautiful sunset, and seeing a bloke riding a penny farthing - a great evening.

Wednesday, 12 August 2015

2nd Finningley Radio Rally this Sunday 16th

This coming sunday, is the 2nd Finningley ARC Radio Rally, held at their clubhouse close to Sandtoft Aerodrome. All being well, I should be there, to try and sell of a bit of surplus junk, and maybe get hold of a few new goodies myself. Bob M1BBV might be assisting me.

If your in the area, why not visit? Its a new rally, but geared towards the constructor, with plenty of components and junk to be had!

Of course, you may wonder what else there is to see? Well, Sandtoft is home to the Trollybus museum  http://www.sandtoft.org.uk/

16 August Finningley ARS Summer Rally *** New date - was 19 July ***The Hurst Radio Communications Centre Belton Road. Sandtoft Doncaster DN8 5SX.Easily accessible from the M180 Jct1/2.Open 10:00. Entry £3.00. Trade. Parking. B&B. Talkin S21. RSGB bookstall.Contact: Kevin, G3AAF 07831-614640.
www.finningleyradiorally.co.uk

Tuesday, 11 August 2015

Frog FAB!


Quite some time ago, I dismantled for parts a defunct 10W CML analogue UHF TV transposer. One of the things I kept from it were the thin anodized aluminium sheet covers on the individual modules.

Tonight, I decided on a bit of sheet metal fabrication! Ive measured and marked up one of these sheets, and using my mini-bender, formed it into a U-shaped box half, the first stage in making a cabinet for the Frog Sounds QRP transceiver I built a few weeks back


This sheet is only about 1/64 of an inch thick, and bends easily and accurately, although it is a bit flexible which makes filing the saw cut edges smooth a bit time consuming.

I'll find out some standoff posts to mount the PCB on, and then once I have the lengths of those, will mark and drill the holes for the connectors, controls and LED. The box will be a bit wide, but I really couldnt be bothered to do the necessary measuring, marking, cutting and filing needed to make a narrower box. Its as wide as the CML modules were!

I will also cut and fabricate another U-shaped half to be the lid. This I might have overlap the bottom section by a quarter of an inch or so. Ive yet to decide how to fix them together. I could use four long standoffs (or chains of standoffs) as pillars, or I could see if I am skilled enough to bend a pair of lugs inwards into which I can secure four M3 sized nut-serts.