Thursday, 30 July 2015

Tape Measure Satellite Beam - UHF Build, Pt 1

After a lot of deliberation, and careful testing (ok, waving about) of 1/4wave lengths of tape, I came to the conclusion that the cheap 19mm width 3m long tape I had was just as good as the 22mm I was going to us, and so have saved the slightly wider tape (which is also 2m longer) to use for its originally intended purpose.

Each of the five elements of the UHF section of the satellite antenna is between 11 1/2 and 12 inches long. Above they are all cut to the nearest higher whole inch. Below, they are cut to exact length, again using steel rule and digital calipers, the corners trimmed diagonal to remove the sharp edges, and the driven element cut into two halves

Next I needed to find a plastic tube to cut the plugs from. What I found was a two part PVC elasticated pole from an old toy pop up tent! Another one of those things I kept because it looked useful! from this, four 1inch, and one 3inch, plugs were cut, again just like the VHF plugs, using a pipe cutter for nice neat edges

Two things I have yet to decide on are A- Do I make a seperate UHF boom, or drill the UHF holes onto the VHF boom already made? And B- How to attach the feeder to the UHF elements.
Question A will be answered by examining the spacings on the VHF boom and the balun positioning. This antenna doesnt have to stay as intended and be separable into two for VHF ARDF, as ive more than enough materials to build a second VHF beam just for Foxhunting. Question B will depend on what M3 bolts I have and how sturdy the 3inch plug is when inserted into the boom.

A more pressing task for tomorrow though is to test the match of the VHF antenna, and add and adjust the hairpin match section.

Wednesday, 29 July 2015

Tape Measure Satellite Beam - VHF Build

A couple of hours today, and I have the VHF section of the tape measure beam built. The hardest part is getting the holes marked and drilled accurately. There are three 3/4 inch holes to be drilled on each side, and these have to line up with each other on each side, and with each other on either side! This was done by first drilling a pilot hole all the way through, and then expanding it out with a tapered reamer bit.
The boom is 1 inch diameter, the holes are then plugged with 1inch long sections of 3/4 inch tube. These are cut using a pipe cutter, which leaves nice tidy edges.

With the tape element in place, the plug is pushed tightly home. By reaming the hole more on a particular side, the hole can be adjusted to get the elements in best alignment. Once complete, these will be made permanent using a PVC welding solvent glue.

 The picture above shows the director and reflector element installed, and the driven element 'mocked'up' using Jubilee clips. You can see that some alignment work is necessary, although it would probably work just as well without.

The next task was to attache the driven element sections. A circular wire brush and mandrel in the pillar drill made light work of removing the paint from the ends, and then three M3 fitting holes were drilled.

The 'plug' section here is 3 inches long. Carefully marked and drilled to correspond with the element that will be attached. The reverse side has 6.5mm holes that allow screwdriver access to the bolts. Each element is fitted with a pair of 'contact' bolts, with M3 solder tags on each. A third bolt secures the element near the end of the plug.

The antenna with all elements installed is shown below. At this stage some adjustment of the element lengths on either side was needed for the director and reflector, this being done by measuring both sides and pushing out the plug, adjusting the tape, and pushing the plug back in, until all was equal.

 In this final picture, both sides of the driven element are attached.

Since taking these pictures, ive attached the coax feed to the driven element, wound the 6 turn balun onto the shaft, and added the BNC connector. I have yet to put the antenna onto the antenna analyser and check the match, which is why I havent yet installed the hairpin matching section. I should get this done in the next few days. All being well, the VHF side will be complete soon, and I can work on the UHF section.

Monday, 27 July 2015

TASCOMM HF Activity?

Years ago, I would listen to RAF Flight Watch on 4742kHz, with the regular weather bulletins and airfield colour states, and the many ASCOT callsigns of transport flights. I'd also listen to the USAF, mostly on 11175kHz (Triple One Upper) with SAM & REACH callsigns, and the regular EAMs and SKYKING messages.

I dont listen to these much now, but when I do, it seems that although the USAF is still reasonably active on HF, I rarely hear anything at all from the UK TASCOMM HF system. Whats become of all that HF traffic? Can all those aircraft really have migrated to satcoms? Or am I just not listening for long enough?

Searching the web doesnt reveal anything, most web pages are older than 2007, before the change to the new system. Its like all enthusiast listening was just quietly abandoned in the early 2000s

Saturday, 25 July 2015

10GHz FM Revival?

Many, many years ago, I could often be seen out on the street with a tripod with a dish on it, looking like some crazed mad scientist come super spy. This was me testing the setup of a 10GHz WBFM system I had got from Eric G0PAQ. This was based on the old Gunnplexor x-band doppler radar modules, as used to open supermarket doors.

Gunn diode based FM systems have long been obsolete, most microwave enthusiasts now having moved onto BUC/LNB based SSB systems. But, FM was at least fun.

Gunn diode units are rare and expensive now. But why not still play with 10GHz FM? Especially when you can get these
for just a few quid each. These a dielectric resonance solid state doppler modules. At just over £3 a go, and needing just an FM IF strip and a modulator to impose the FM deviation by varying the supply voltage, simple FM 10GHz can be played with. The range might be very limited until it can be found how to put a better antenna on, but I might get a couple to play with.

Who knows, perhaps SOTA 10GHz WBFM might make a comeback!

Thursday, 23 July 2015

Dual Band Tape Measure Antenna for SO-50

Ive now received the tape measures, ordered from Amazon (these here - 7.5m-25mm-Measure)

The design ive decided to go with is one that can be found on the AMSAT website. Heres a link to it in a PDF format W6NBC 2m/70cm Beam.pdf Its not strictly a dual band beam - its two beams - a 3-el 2m and a 5-el 70cm, that clamp together in a crossed yagi pattern for satellite work. The 2m beam on its own can be used for ARDF.

The tape measures are 25mm wide, which means that a full size 145MHz director element is self supporting and does not collapse even when upside down, but still easily deforms if caught on foliage, or for stowing away. The tape itself cuts smoothly with a pair of aviation type tin shears.

Ive rounded off the ends, which is essential, as the corners when cut are razor sharp! Do this, AND cover them with insulating tape! That way, you wont hurt anyone, or yourself. Make sure you pick up all the offcuts - they are like needles! You will not be popular with the family if someone gets one in their foot!

The picture shows the 2m antenna elements cut and ready to assemble to the boom (which ive yet to form). A narrower tape will be used for the 70cm beam elements, which are so much shorter and so dont need to be as substantial.

The measurements, being American, are all in decimal inches. I found it easiest to measure the length to the next whole inch, then once cut, use a digital caliper to measure and trim the tenths.

Wednesday, 22 July 2015

Cheap as Chinese chips! Building the Paeansonic JC210SP

Items ive ordered from the Far East are slowly trickling through the postal system onto my doormat. The past couple of days have seen the arrival of several items of small electronics, including a batch of 0.1inch SIL header pins, and a set of ten 'perfboard' type prototype PCBs. Amongst these was also one of my 'frivilous' purchases - a violet (405nm) laser pen, with a 'star' grating. This produces various light patterns, but the grating can be unscrewed to give a single beam. Just a bit of fun.

Of more practical use was a batch of ten LM567 PLL tone decoder ICs that came yesterday. These can be put into use to detect tones, latch onto a particular tone for decoding, act as an FM detector, or work as an oscillator. Ive not used them before as they have always been just a bit pricey. Buying from the Far East, the costs a peanuts! However, there are fake semiconductors out there! So, each and every one was put into a simple dual frequency oscillator circuit to check it - and they all passed. One of these will now go onto become the detector part of a Morse Reader.

Ive also finally tested the Frog Sounds 40m CW QRP transceiver. All seems well. The receiver gives a Minimum Discernible Signal of -110dBm into a set of cheapo earphones, and the transmit side will run a tad under 2W when given 13.8v, and 1W on just 9v! Harmonic suppression isnt great, around 30dB down at 2nd Harmonic, but its adequate for a radio of this type.

So, onto the title subject! What the heck is a 'Paeansonic'??? Well, I spotted this little AM/FM portable radio kit on ebay, item number 231603813152
Clearly the name is supposed to sound like Panasonic. It intruiged me, so I thought i'd give one a go.

For a nats over £4, I wasnt expecting much. But when it came, I was quite surprised to find it looked like it might not be too bad. The circuit is based around two common radio ICs - the CD9088 FM radio subsystem, and the TA7642 AM TRF IC (the modern version of the old ZN414), along with a TDA2822 dual AF amplifier chip. Its a very simple circuit with minimal alignment, however more about that later!

The kit contained everything, including case, antenna, and even the wires to the loudspeaker! The one thing it does lack however, are English instructions! What you get is a single double sided sheet of Chinese idiograms, interspersed with the odd Latin character here and there. Luckily, the circuit diagram is clear, and there is a PCB layout diagram, which is actually backwards! There is a parts list as well, but quite a few parts are only listed in Chinese!

All that said, its really not that hard to build! The PCB is rather thin, so take care handling it. It does develop a bit of a curve during soldering, but its nothing to worry about. The first thing to do, is to solder on the CD9088 chip. Now, this is a surface mount device! But its quite a wide pin spaced package, so I managed it even with the big tip on my 25w Antex!

With that done, I followed normal build convention, starting with the resistors. These are all a bit longer than the space between the holes, so its best to fit them at a bit of a slant. My PCBs silk screen had the part value/marking on it rather than the component number. With all the resistors installed, I moved onto the ceramic capacitors. Theres a lot of these! Note that when fitting the resistors, theres a link, marked 'J' on the board, thats worth fitting at the same time! Just use a cut off leg from one of the other components.

With these fitted, your not far off done! I did the few electrolytics next, then the switch, volume pot, tuning capacitor and headphone jack. The two coils went on next, and finally the AM radio IC and the audio amp IC.

In the picture above, you can also see the LED fitted. This has to fit into a hole in the case, so I found it best to fit the PCB on the case mounting studs with the LED in place, let it slip to its place in the hole, and then solder it, ensuring its proper alignment.

At this time, I soldered the wires to the loudspeaker and installed that in the case front half. A few small chunks of hot melt glue were melted onto the rim to secure it. The red and black wires were soldered to the tabs on the battery contacts, and the contacts installed in the slots in the case. These were the only parts that needed any force - a firm push with the tip of a pair of long nosed pliers to push them into place.

Next, I assembled the AM ferrite loop antenna. This came as a rectangular ferrite rod, a round prewound coil, and a fixing clip. The rod pushed firmly into the clip, and with a gentle squeeze the coil slid securely onto the rod. The silk screen on the PCB shows the correct positioning of the coil on the rod (about 1/3rd of the way along) The clip then fits in a slot on the PCB. This was somewhat loose, so more hotmelt to secure it. There are PCB holes for the coil wires, but I routed them around the back of the PCB and soldered them directly to the pads.

The telescopic antenna fits into a slot in the rear case half, and secures with a small screw. There is no solder tag, so prior to fitting the antenna to the case, its best to solder the remaining yellow with onto the antenna base next to the screw hole. Give it some heat and it tins nicely, being plated brass. The wire and then the antenna threads through the hole and is screwed into place.

Pretty much all thats left now is mechanical, and alignment. There are essentially three alignment points, and this is where it gets tricky! AM is aligned by adjusting the tuning capacitor units trimmer capacitor nearest the edge of the PCB. FM however is more complicated. The other trimmer has some effect on the tuning, but the principle adjustment is L2, the 8.5T coil. This has its turns spread to shift the frequency. The trouble here is knowing how much! I found it best to temporarily fit the PCB and the tuning indicator, adjust the tuning to put the pointer where you know there will be a known station (I set mine to 90, knowing that BBC Radio 2 is on 89.3MHz) and then remove the board again without moving the tuning!!! Then, temporarily connect up a 3v supply, and splay L2 and adjust the trimmer to get your known station. Of course, to do that, you need to fit the tuning indicator! This is fun!

The tuning indicator is a plastic molded strip that fits into a recess on the top of the tuning knob, with the strip coming out a slot, coiling around, and going through a slot in the front case! Its pretty fiddly! The picture below shows how it fits. The self adhesive tuning scale needs to go on then, so you can find the appropriate position on the scale! Be aware that the tuning range on the scale starts at 76MHz!!! Our FM band doesnt begin until about 87MHz, so dont expect to hear much other than noise down the bottom end!.

It took me quite a while to get the coil and the trimmers all set up just right. I'd advise as well not having your mobile phone in your pocket whilst doing this, as the beeps and buzzes of GSM interference are pretty irritating. Once aligned, the PCB fits on three fixings, with a fourth screw hole between the tuning capacitor and the volume control, a 3mm self tapper fits there to secure the board. With all the wires connected and pushed out of the way under the board or wherever, the two halves of the case snap together, and secure with three long self tapping screws and another 3mm one in the battery compartment. I found that the hole for the headphone jack needed a bit of a ream out with a drill bit, but other than that the case went together nicely.

With the case screwed together, the final task is to fit the mode switch! This snap fits through a slot on the top onto the AM/FM switch, but be aware its a slightly odd shape and fits best just one way around!

The battery compartment lid is captive, so you cant lose it when fitting the batteries! Which is a nice touch. All in all, once complete, it works surprisingly well. FM is a bit fiddly to tune a station in due to the small dial but once done its nice and clear, and surprisingly loud! AM works pretty well too. The antenna folds nicely away when not needed.

For what it cost, its a fun little kit. Build time for me was about one and a half hours. And the result is a basic but functional AM/FM pocket portable, which is also rather cute!

Its an ideal kit for a 'guided' build by a beginner with assistance from a more experienced builder, although due to the SMD part and the tricky alignment maybe not for a beginner to tackle on their own. Im going to get another for Sam to build!

So to end this post, i'll also mention that ive finally had success in receiving the downlink on 70cm from Saudisat SO-50. I have the FT-857D set up in the car with split frequency memories for this. I copied a number of stations during a lunchtime pass on saturday, during my lunchbreak at work. Im now awaiting the arrival of a couple of tape measures, and will then start building a dual band crossed yagi tape measure antenna for working the FM satellites.

Thursday, 16 July 2015

Finishing a few off

Dissapointingly, no parcels arrived today from the Far East, so ive had no new bits to get excited over. I decided instead to finally get a couple of projects boxed up and completed.

First up was the little Chinese 40m Pixie. In the finest tradition of QRP minimalist radios, this got built into an Altoids tin

because of the clearances needed for the sockets, it wasnt possible to have the lid open as it originally did, so this has been removed and the 'hinges' flattened down, it now just clips on. There is space when open to slot a 9v PP3 battery in the tin to power the radio.

Next, was the 40m Sudden-2 kit from Kanga that I helped Sam build a couple of years ago! I had been looking for a suitable box for it. The case selected is a re-purposed Tvonics Freeview Set Top Box case.

The front has a sort of wave shape, but I think it looks quite groovey. I havent bothered to cover the back over, so theres still lots of cut-outs for SCART connectors etc, but some of the other holes have been pressed into service for the power and antenna connectors.

 The only problem was finding some knobs for it! I have a box full of knobs, but couldnt make up a matching set! Either they were of a type that will not secure to the shafts of the controls used in the kit, or they were missing their grub screws. Just where the heck have all my grub screws gone?
Coverage is about 7.05 - 7.15MHz. Sensitivity seems low, -75dBm ish for a decent sound, so will have to check that out. But, I think it looks alright

Other than that, the only other stuff done today has been more of the laser comms circuit mock up. The top section of the breadboard is the 555 timer sawtooth 40kHz generator. Below is where I have started to mock up the 741 op-amp based microphone amp.

The module beside them is a DDS module. When I finally work the pin-out out, this and an LCD module will be mocked up with a PIC chip to create a DDS VFO. I really should get that LCD sorted!

Wednesday, 15 July 2015

Old and New

Today has been a bit of old, and a bit of new, as far as radio work goes. I slept in very late, and eventually pottered into the workshop. First up, I decided to finally take a look inside this

 I salvaged a couple of these that were being junked, because the cases are nice aluminium extrusions, a new panel each end and they will make great project cases. Inside, theres a few nice bits, a bargraph LED block, some SIL resistor packs in sockets etc. Nice to see Zilog Z80 series chips again! The PCBs, once ive had any bits useful to me, will probably go in the 50p a go bucket at Finningley Rally.

Something else that ive been meaning to get around to doing is testing this MSF clock receiver

This was salvaged from the skip many months ago, probably years now, and its original case re-used as the housing of my Dekatron Spinner! I finally decided to actually power it up a few days ago and see if it worked, which it does! Next step then is to see if I can get it interfaced to something that can decode the time from it. It has only a +ve and -Ve connection - the signal pulses are output by pulling the supply line low. Im going to see about using a PIC to decode it, but Sam has also agreed that a Raspberry Pi might be the best way for him to learn programming, so ive given him a challenge to interface it to his Raspberry Pi (when I get him one)

 Also in the old list, Some time ago I got an old discone antenna from an ex-colleague. It had been up on a chimney for many years. The elements are bent, the feed open circuit, and very badly corroded and tarnished. Today I dismantled the feed section, and using a wire brush wheel on my drill press, removed the rust and corrosion.

 Now, with a new nut on the top, the feedpoint connections are all good again. I need to find a blind 'dome' nut and a suitable spring washer to suit, and I still have the 'cone' elements, which are aluminium tube, to straighten. My thought is to mount it on the workshop roof to give me a usable test antenna.

On the subject of antennas, I built the 4:1 balun today needed for the Cobweb antenna. This was a kit from Les at Amtools. I need to find a suitable box to mount it in now

The plastic case for the component tester also arrived today from China, so that is now built into its own box with three crocodile clip leads coming out of it. I managed somehow to mess up the measurements for the holes in the case for the LCD contrast adjust and the DC input, so these dont line up. I also couldnt find a button that would operate the power switch, so thats been removed and a SPST toggle switch mounted instead. At least now thats a nice convenient little test box, not an exposed PCB.

I also got around to testing my 80m ARDF beacon transmitter! The ATU is working correctly, but the NiCd battery pack went flat very quick, so I need to charge it up properly and redo the test.

The only other thing done today was to mock up on breadboard the 40kHz sawtooth generator circuit that will form part of the PWM modulator for the laser communications unit. This is only a simple 555 timer circuit and was very quick to get up and running, although my old oscilloscope took some time to become stable and not do silly things whilst displaying the waveform. I cant mock up any more of the circuit, as im still waiting on the comparitor ICs. 

My last chicken, Talullah, died a few days ago. She was very daft, more like a dog than a hen, and would follow me about. She was particularly fond of getting into the workshop and falling asleep on the bench

Tuesday, 14 July 2015

Hanging on the telephones

Actually, despite the title, the telephones in question here are somewhat before the era of Blondie!

The vintage high impedance headphones I purchased arrived today. They are in surprisingly good condition considering their age, and the repair mentioned in the sale listing is actually quite well done. Theres no fabric on the headband, but the fabric covered cord is in good nick. They are marked BTH BBC.

So far, I have tested these using a meter on the resistance ranges, the small current causing them to crackle - and I can hear that crackle in both 'receivers'. I cant read the resistance though, I suspect because my meter is rubbish! But, I can hear noises from them, which is what they are supposed to do.

Next trick is to get some audio into them, but I want to protect them from excessive DC (the winding wire is very thin!) so will rig up a small audio transformer to feed them.

Im hoping they will work nicely with the Pixie transceiver. I'll see about that tomorrow.

Sunday, 12 July 2015

Frog complete, ready to test

 Carrying on with the Chinese 'Frog Sounds' CW transceiver build. Finding a bit more spare time, the next stage was to fit the capacitors

With these installed, I moved onto the semiconductors, and the rest of the parts.

 At this stage it was all but complete. The only parts not installed being L4 and L5. Ive left a little clearance above the PCB for the crystals, which I would normally install flush to prevent microphony, but the solder pads on the component side of the board looked a bit wider than the insulation around the pins, so I didnt want to risk them shorting out.

L4 and L5 proved to be a little more problematic. The paperwork that came with the unit states that these are 1uH and 22uH, but neglects to say how many turns, and which is which core! Thanks to members of the G-QRP club, and in particular Andy Cutland, I found out they are 11t on the ferrite toroid for L4 and 16t on the T37-2 toroid for L5.

A word of warning for those of you building one of these and used to the easy life of the western coil winder - the wire supplied is NOT self fluxing! I had to scrape of the enamel which is a delicate job. But, the coils are now wound and installed. All that remains is to test the unit.

As usual, it seems, with these Chinese Kits, Ive a lot of 'spare' parts left over! Lots of extra resistors, ceramic capacitors, probably three extra lots of the electrolytics! Plus the odd diode and a 2N7000 MOSFET. I notice its never the NE602s the put extra of in!

 Back to the subject of LASERs! -

I have on order a pack of ten 1mW 650nm Red laser modules. Well, I now also have a project for them! Im going to knock up a simple voice transmission link with them. Using a 555 timer and some op-amps and comparitors, it seems i should be able to use PWM (Pulse Width Modulation) at 40kHz, to create an amplitude modulated laser voice link.

My green laser pen that fell to bits I dismantled. Unfortunately, although the big brass block acts as a heatsink, this makes it hard to solder a wire to, and in doing so I over heated the module. The laser chip is fine - but I melted the plastic lens in the laser diode housing! It still works, but the beam is a tad divergent now!

Thursday, 9 July 2015

Frivilous Purchases - Frikkin' LASERS!

I really shouldnt buy electronic items as a way to keep alert during night shifts!

A new 'violet' laser pointer, plus a pack of TEN 650nm laser diode modules...

I have NO need for them! But, ive been watching them for months and finally couldnt resist!

Less frivilous, ive also purchased, a pair of vintage high impedance headphones, for use with crystal sets and the little pixie type minimalist radios, and various items for finishing off other projects.

I dont intend to buy anything online tonight, as ive to go to finally collect a sextant in the morning. But I will be ordering out - probably a big filthy, dirty kebab!

Monday, 6 July 2015

Building the Frog Sounds v.3

 This little kit arrived a few days ago all the way from China. It is a 40m CW Transceiver, based around the NE602 plus a few other bits, and is supposedly capable to kicking out up to 3W.

All came reasonably well packed, although as usual the instructions are machine translated from the Chinese and next to useless! Most of it can be worked out easily enough, although two toroids that need to be wound have no turns information!

 Here it is next to my previous little Chinese transceiver kit, the Pixie. This one also has the odd quirk that the sockets all fit with a couple of degrees angle to them! Here its just mocked up -

All the resistors are 5-stripe types, which I hate trying to read, so ran the ohmeter over them all! They are as usual all vertical mounted. They are all fitted in this photo, and theres a lot extra left over! I suspect they are so cheap that so long as the minimum number are included they dont care how many more you get! All spares for me I suppose.

And, finally for today, with the lower profile sockets, IC sockets, and fixed inductors installed

There does seem to be some debate as to whether this is the same as a '49-er' kit, Ive no idea myself, never having built nor seen a '49-er' before!

Ive also just ordered a plastic case for the component tester I built some time ago - this is easier and probably cheaper than trying to fabricate one!

I also couldnt resist ordering a AM/FM broadcast portable radio kit! This is an old 1980's style analogue tuning radio which I fully expect to perform to its price! But hey, it'll be a bit of fun to build when it gets here.

I must get around to boxing up the Pixie and the SurfPI as well