Perseids Meteor Shower Peak Soon - Lets Try JT6M!

Something ive thought about doing but never tried before, is Meteor Scatter. This, just like EME and the various QRP HF modes, is something that with the advent of fast computers, and particularly with Joe Taylor K1JT writing amazing software and developing amazing weak signal modes, is now within the grasp of even the smallest station.

The Perseids meteor shower is due to peak over the next couple of days, with average ZHRs of about 20-30, but with the severe disadvantage for visual observing that theres a full moon, which will wash out all but the brightest bolides. But the full moon doesnt affect VHF!

So, whilst Whispy gently toasts its PA transistor running all night on 10m, Ive downloaded Joe Taylors WSJT software suite, and am listening on 6m for JT6M meteor pings

Although not shown in the screenshot, I have picked up a few pings, along with a horrid pulsing noise which seems to come from the computers mouse, and annoyingly covers around 40kHz of the 6m band, centered right on top of the MS window!

Another thing of course with meteor scatter, is that it will work in daylight, something that is very rare for visual observation of meteors!

I dont yet fully understand the system, or procedures, so will need to see a good few received pings first before I decide to try for a QSO.

10m Wispy Tx running overnight

The Wispy beacon Tx is set up to air via my ATU on the main station antenna, Toshiba laptop providing the audio drive WSPR signal at a 50% Tx cycle.

Its running from a 12v 7Ahr SLAB. As it uses pretty much the same current, and runs at the same temperature, regardless of whether its actually on Tx at the time or not, I am going to put it to 80% Tx overnight, and hope that at some point, perhaps morning grey-line, some propagation occurs that at least gets a spot to somewhere!

Wispy on test!

After finally discovering that I had simply not been driving her hard enough, I have the 10m Wispy beacon transmitter testing to air.

Several problems had to be solved to get this far. First, I found the laptops clock is woeful! I now have Dimension4 running on both the laptop and the desktop to keep the clocks happy. Since doing this, my own decoding of the beacon (via the main station) is almost solid. Second, the main antenna, during high winds this morning, failed. The wire snapped right at the feedpoint, necessitating some quick repair work to get the antenna back in service.

 

The picture shows my own decodes of the beacon. From this, and some other test information I now now that the Wispy Tx takes around 30mins to stabilize during warm-up, after which its drift rate is negligible, but the initial drift during warm-up is about 60Hz. I  also know that the Tx takes a tad below 160mA, even in standby. This is due to the amplifiers always being powered. I might, later, add a Tx relay so the amplifiers can be off and allowed to cool when not in use, but that will add the complication of needing either a PTT input or a tone detector circuit, like in the FT-857D Interface.

Prior to any of that, I'd like to play with the biasing and see if I can lower the quiescent current somewhat. I also want to play with the drive and the output filtering to further reduce the harmonics in the output. If I can reduce the spurii going into the amplifier, then I can ensure that as much of the power consumed as possible is being used to generate my wanted 28MHz DSB signal.

To this end, Ive added the little 28MHz bandpass filter to the output of the SBL-1 DBM on the 'TennaLady' mock up, as well as adding the necessary parts to convert the oscillator to 14MHz self-doubling to 28MHz. If I can kill the spurii prior to the amplification chain then so much the better.

Another little beastie im looking at is a 28MHz 1W Power Amplifier, using parallel small signal bipolar transistors. Roger G3XBM has used this approach in the Tx only version of Wispy, plus in his 'tenbox' AM set. With 4x 2N3904 NPN transistors, Roger gets 500mW DSB, 250mW SSB equivalent. So, Im going to try with 8x transistors! Hopefully giving me an equivalent of 500mW SSB.

The photo just shows two transistors fitted, which would give the same output as the single 2N3866 im currently using in Wispy.

Unfortunately, so far my Wispy beacon has not yet been spotted. Ive had her running most of the day, but the propagation on 10m at present is dire. I'll let her run over night, and into the morning. Depending on the wind, I might put the 10m J-pole up and run her to that tomorrow, see if having a resonant antenna and not having to go through an ATU and long feeders makes much difference. At 100mW I think every little helps. At some point however I want to work on the receive side, so if I make decent progress on TennaLady tomorrow, I might try her to air for a bit while I do the Rx chain on Wispy.

WSPR, Window, and Rain

It seems the window line section of my antenna isn't too keen on the endless rain we've had overnight. After I discovered that WSPR had crashed sometime in the small hours, probably when the antivirus decided to tell me it was due to expire, I restarted on 20m, but found not a single person was hearing me!

Playing with the ATU showed it was very difficult to get a decent match anywhere, suggesting the now soggy vegetation near the balun is probably drooping onto the window line section and detuning it. I have managed to get a usable match on 40m, so have popped up there at 2W. The system went straight into transmit with the results as below

 

Now into the receive cycle, lets see where I can get today 

UPDATE: The rain has stopped (mostly) so I managed to get out and take the shears to the mass of Ivy that has, seemingly in the last 12h, utterly overgrown my balun and lower section of window line feeder. With that cleared I can once again get a match on 10m, so have QSY'd up there to see what can be done.

WSPR - A fantastic mode, so long as someone uses it!

Yesterday, I set up the main station to beacon in WSPR mode on 10m. This was sometime just after lunch.

Around 21:30, I retasked the system to 40m. Not one, single, solitary spot on 10m! Neither hearing nor heard. It seems there were less than a bakers dozen of us on 10m on the entire planet! This is simply rediculous. There were nearly 200 stations on 20m, a band whos characteristics mean it really doesnt need any propagation investigations. This is just people who want to do something without actually having any real involvement in it.

On tasking the system to 40m, as soon as I came out of idle the system went into transmit, and was immediately received in Tasmania!

Today, shortly after 15:00, I started beaconing, 10% Tx/Rx cycle, at 2W on 6m, beaming SE. I dont hold out much hope, as theres fewer than ten stations around the world on 6m today! And, although I dont know whether to believe it or not, the WSPRnet site says most of them are running 0%, i.e. Receive only!

FT-857D Digital Interface Mk2 (Rebuild)

Yesterdays successful test of the digital interface for my FT-857D did unfortunately leave me with a rather convoluted collection of bits of circuits all cobbled together. Todays task then was to build the Mk2 interface - in other words, get it all on the one, neat and tidy board, ready to be boxed.

Last night I drew out the schematic, planned a Veroboard layout, and selected a suitable hunk of board. The only minor change was to include a level control potentiometer on the receive path. Not really needed for WSPR, but perhaps useful for other modes.

The picture above is how it all looked at close of play yesterday, not including the opto-isolator. The board to the lower right is the single transistor audio amplifier, that drives the audio detector and PTT switch (right hand side of main board). The modified el-cheapo Chinese USB soundcard hanging off the whole lot to the left.

This is the new board. As an odd off-cut the sizes actually turned out to be pretty good for the job, with the longer, lower section fitting the PTT system nicely. Here the audio isolation transformers, DC switch and opto-isolator are installed, along with the radio side ground connections. 

Further on, the Tx 10:1 audio divider, computer side grounds, and the audio rectifier diode doubler are installed. What can't be seen, is the continuous run of track breaks under the transformers and opto, forming a complete separation of the two signal sides.

And, finally, the completed board, in use. The USB sound card is affixed onto the board with hot melt glue. This is during final testing. Im pleased to say all the testing went well, with good receive spots from around Europe, and some decent DX 'heard by' spots into Isreal and the USA, all at about mid-day here in the UK on 20m.

The schematic is shown below. There is nothing new, or original in this design, and it borrows much from KK7UG's interface. The audio activated PTT circuit is a mish-mash of several designs found around and about the internet.

With a couple of simple mods for serial port controlled PTT etc, this could easily be made into a 'universal' digital modes interface.

The final two tasks are to replace the sound-cards USB plug with a wired USB connector, and to put the whole thing into a case.

Mobile WSPR - Finally!

Well this took some flippin' doing! The audio isolation needed to make an effective interface was really quite simple, the trouble came about when trying to use the radios own Digital VOX circuits to control the transmitter. It would work, so long as the audio input was high enough, but that level was always far greater than the power output I wanted, and always driving up into the ALC action region! No matter what settings I used, adjusting the soundcard level, the interface level, the VOX level, or the Digital Gain control on the rig, I could not get the 1-2W I wanted AND have VOX PTT!

So, I had to work on a hardware solution.  This seemed simple - both channels of the soundcard carry the same audio signal at around 4Vpk-pk, it should have been a simple job to rectify this and drive a switching transistor. Er, no. The output of the diode doubler used only generated 0.3V, no where near enough to switch the PTT transistor.

So, some head scratching, and internet searching later, I added a single transistor audio amp to the detector circuit. Yeah! It switches!

Only trouble was, I had to use the 5V supply from the USB soundcard to power the amp, so I now no longer had the isolation between the radio and the computer! The photo above shows the interface in this state of development! I now had to add yet another little bit of veroboard, this time with a 4N25 optoisolator and a resistor on it.

That done, I got out to the car, connected everything up - and it wouldn't Tx! Arrgh! I'd forgotten to put the ground connection from the opto to the rig on! Back to the workshop, telling Julie that 'This is definately the last trip!' and then back to the car, and finally, a working audio driven PTT line!

So, the time now being around 19:00, and with a fully recharged laptop battery ready to give me its whole whopping 20mins capacity, I set up the Tx level to about 3-4W, sync'd the clock with an internet time server, and started WSPR, with one Rx period followed immediately by a Tx period. First spot, both heard and heard by, was HS0ZKM Thailand!

So what remains now is to rebuild the interface with everything, including the USB soundcard and the opto-isolator, all on the one compact board!

Show Cards and Yaesu WSPR

After a slight delay of just about 11 months, I finally took delivery of the QSL cards for GB2LDS this week. They are all now written, along with a few remainders from the year before, and ready to be sent off to the bureau. Thats around 150 cards.

Ive taken the time to check QRZ.com for QSL status, so as not to waste a card on someone who doesnt want one anyway, or who only accepts them direct but who hasnt sent one direct to me. If you havent sent a direct card in 11 months then clearly your not going to send one!

With just a month to go before GB0SML, the final preparations are underway. The main antenna now has actual wire on it, and just needs a trial on site to trim the elements. The digimode interface for the FT-857D is made and due to be tested today, im just waiting for the laptop to charge up!


Well, after giving the lappy a brief session on the charger, it lasted long enough for me to establish a working receive path. With the car parked on the drive, and just the mobile 20m whip, good Rx spots were straight away coming in!

 

Now to get Tx working! This is less straightforward, as it requires some fiddling of levels and power settings. With the Tx PWR setting turned right down to 5W, and the DIG VOX setting right up to 100 (not greatest but will do for now!) ive managed to get the radio to trigger to Tx from the WSPR software. Using FM mode and a dummy load and power meter, Ive set it first to ensure the meter was calibrated at 5W, and then set the audio drive level to give 1W output.

This is all with the DIG GAIN level set to 50, and without reference to the ALC meter! I will probably let a bit more drive into the radio, and adjust the DIG GAIN to set the actual modulation level. However, for now, flat battery stops play! The lappy is back on charge.

Cheap Chinese WiFi Yagis - Avoid!

Well, Ive generally found the cheap Chinese imports to be alright, but it seems I lucked out on the WiFi Yagis.

 

I ran a test, comparing these to a standard 'whip' wifi antenna, and these are actually worse! The more I look at it, the more I realise I should have known from the start!

The main problem I think is that the driven element is so far out of the plane of the antenna.The boom is also far too wide, and the elements far too thick.

 

 I will see about a mod to put the driven element correctly in the plane. I have two of these and if I dont get them to work im effectively out of pocket by about a tenner (yes, I know its not much for two antennas, and in fairness, the U clamps they came with are probably worth a fiver themselves)

Its a shame, as the little cheapo wifi dongle I bought to improve the laptops connection works quite nicely! Its only about 10dB better than the laptops internal antenna, but since it has an antenna port, it means I can connect a directional antenna to it - If I can get a working one!

I have looked at various homebrew wifi yagis, and will probably make one now and see how it works.

 I finally have the spanner for the Larkspur mast! Thanks to Chris G6HTH.

Ive looked around online and made use of a yagi calculator to create a set of dimensions for a 15dBd gain 2.4GHz yagi, using simple materials that I have knocking about. It should take about 2h to knock one up.

Playing around with Jenny

Jenny, like many of us, takes a little bit of caressing to really get going, and Julie doesnt mind me playing around with her. Of course, Jenny, or 'Genny', is short for generator.

This is the machine I picked up at the rally. After Sam and I had enjoyed our morning of Canadian canoeing, and a fried chicken lunch, we headed to ASK to pick up some two stroke oil for her. She needed a while for the oil and fuel to work into her, but soon she was throbbing away. She does like a little squirt of carburettor cleaner/easy-start to help get her going, and she runs a bit lean, so likes just a touch of choke to keep her from 'hunting', but other than that she works quite well.

She's shown above feeding a small 7A 13.8v linear PSU (it does slightly over volts anyway). 
The blocking diode needed to allow parallel battery operation was lifted from an old PSU card, I think from a transposer. Its a dial diode, each leg rated 15A. It was one of a half dozen semiconductors all mounted on the same block of aluminium, so I also took that ali block to mount it on.

A pair of lengths of my heavy duty DC cable provide the connections to the diode. A layer of tape, and then liberal coatings of liquid insulation, sealed and insulated the +Ve rail.

A small piece of heatshrink tubing, pumped full of hot melt glue, seals the -Ve rail through connection. The whole assembly was then wrapped in 3M PVC electrical tape. The red smudge isnt, for once, my own blood (I managed to save cutting myself for later!) but is actually tamper evident varnish, used to seal the thread on the bolt.

By setting the PSU feeding into the diode such that the output voltage at the diodes cathode is 13.6V, this will allow the big 38Ahr SLAB to be charged and act as a reservoir for the peak current demanded by the radios. An added bonus of this scheme is that the generator can be stopped for refueling without having to stop radio operations.

Ive managed to get a bit further with the WiFi repeater, but need to do a proper air test soon. Still to do is making up the datamode lead for the Yaesu, the 6-pin miniDIN plug I have isnt wired properly. Being a sealed plug, its not easy to change, so ive ordered a plug. I can probably get away with the old plug as a test until the new one arrives.