Hamcom 2014

June brings the annual Hamcom hamfest to Dallas, which, as always clashed with the ARRL June VHF contest.

As in the last four years I volunteered to help man the Elecraft Booth, this year with Eric WA6HHQ and wife Lerma. Their plane got diverted from DFW to AUS as DFW closed for an hour due to bad weather so we didn't start setting up till 5pm Wednesday. 

The trade show exhibitors this year started earlier at 0800 and officially closed at 1800, making a long day. The new item this year was the PX3 Panadaptor for the KX3.

 The K3/0 mini was also in evidence, this time using the software from remotehams.com, to control a K3/KAT500/KPA500 in California. It was great fun on the Saturday afternoon listening to the 6m activity in California during the VHF contest.

 The outside flea market was not too exciting. The most interesting item was a Layafette tube tester without model number which I bought for $15, I was told that Lafayette often rebadged other companies products.

 I also got some tube bases, some tubes for my BBC studio-E receiver and a multiband whip for the 2m module

I did get to meet John Langridge. KB5NJD who also operates on LF as WG2XIQ and compare notes from WH2XES. Unfortunately I could not get to his talk on reusing "normal" HF antennas on 477kHz.

UPDATE: The Lafayette tube tester is a Accurate Instruments model 157 in disguise

DrugStore Tube tester...every shack should have one!

To help me restore the Country Belle radio I wanted to test the tubes.  I mentioned this to Roger at the NTMS Tuesday BBQ meeting. At the next meeting he appeared with a loaner tube tester in the back of his truck. This was a "Seco Electronic Tube Analyser"  It was the type often seen in your local USA drugstore in the tube era so you could test the iffy tubes in your radio receiver and they would sell you a replacement. This one had been previously built into a panel but was now mounted on a undersized box.

It has a meter, switch,  variable load resistor and 92 sockets. It came with a manual of what settings to use for each tube.

All the tubes in the country Belle radio passed with flying colours. along with some other 1930 era tubes I had acquired for future projects.

I had been looking for a 6AF11 audion multistage tube for a while. WA5VJB found me one in the Dayton Hamvention fleamarket. The manual had 3 settings for the tube so decided to test it. Two settings produced good pass results of 120 but the third only produced 20, a big fail. Pity! I then remembered that Roger had mentioned the tube tester can be used as a reconditioner by leaving the tube in its test configuration overnight. Worth a try. The next morning the reading was 100, so I let it be for the rest of the day which restored it to a 120 reading. What a great tool, even if it is so large! I will be looking for a transportable tester.  

Restoration Project: Country Belle 1958 Radio



Having built a couple of one Tube receivers, a local amateur decided it was time for me to move on to a restoration project. As a challenge he presented me a while ago with his spare Country Belle Radio #556  made by Guild in 1958 (the metal chassis is stamped 6 jun 1958). This radio was made to look like the old style wall Telephone, but had a 5 tube medium wave receiver Inside. Taking the earpiece of its rest turns the radio on. The Winding crank is the tuning knob, very neat. It had some hardware missing (a bell, the tuning crank and the earpiece rest) but was electrically complete.

The Tubes lineup is the classic "all American Five".  Converter: 12BE6, IF amplifier: 12BA6, Detector: first audio amplifier: 12AV6, Audio power output: 50C5, Rectifier: 35W4. The subtlety of this lineup is that the filament Voltage/Current all add up so you just connect them all in series across the 110V AC (or DC) supply. The 35W4 even has a tap on the filament to drive a dial light (#47)

As the radio is transformerless,  for safety I borrowed an Isolation transformer from WA5VJB. When power was applied, all the heaters lit up, there was some noise but no stations could be tuned in. Tracing the circuitry I found that the grid Transformer of the 12BA6 was open circuit. The Inductor was taken apart and the wire mended. Now when powered up stations were loud and clear. I peaked up the 455kHz IF Transformers, noting that each transformer had an upper AND a lower tuning core. Note that the radio has an internal ferrite rod antenna, making the receiver directive. The short piece of wire(by medium wave standards) doesnt do much to increase sensitivity

Next task was the Hardware. Luckily a friend of a friend had a #556 carcass in their barn which I was given. The wood work was bad but it had all the missing hardware.

The next decision was what do about the woodwork. Sand it down and repaint or leave it in its current patina state. In the end I decided to sand down all the wood parts (after stripping the fittings) but this also removed the Decals. I then sprayed it with Pecan wood stain/Varnish (3 coats). The Brass fittings were cleaned with Brasso (which I discovered is sold in the USA) then varnished. It was recommended to spray the other black metal fittings with Black Lacquer, but using it can be challenging. I went to the local O'Reilly's autoparts store to get some but after explaining what I wanted it for to the Old Guy, he said not to use it but to use Black "Dupli-color Vinyl and Fabric Coating" as It would flake less. This has really worked well

I found a source of replacement decals at radiodaze.com These were water based transfers (like I used many years ago for Airfix model aeroplanes) which were a little tricky to apply, but I managed it. When dry the cabinet was sprayed with Varnish

When completely reassembled,  the radio worked fine and looked very nice, even though I say it myself!





The restored external view



The restored internal Electronics



NavSpark Arduino compatable GPS receiver

Before Christmas I saw a posting for NavSpark on the crowd funding site indiegogo.com.  From the web page https://www.indiegogo.com/projects/navspark-arduino-compatible-with-gps-gnss-receiver  "NavSpark is a small, powerful, breadboard-friendly, 32bit development board that is Arduino compatible, with a world class GPS receiver as on-board peripheral, and under $15".  At that price I ordered one, especially as it came with a dual band patch antenna for $19.

 

It arrived last week, the board looking like an Arduino micro with the dual band active antenna.  Heeding the warning that the U-FL connector can only be used a dozen or so times, I mounted the Board and antenna in a plastic box.

 

 

The Arduino IDE, viewing software programming guide and documentation are all at http://navspark.mybigcommerce.com/resources/    The USB chip is by Prologix, the unit appearing as a serial port (defaults to 115200Baud). After installing the drivers and software and putting the receiver out on my south facing balcony, it found GPS and GLONASS satelites

 

 

The map shows the correct relative position of the satellites, but the map is based on Taiwan (where the units are made) and isn't currently changeable. Not surprising the locked satellites are all to the South with the system on a south facing balcony.

 

Sam Wetterlin Reflection Bridge

Having bought a cheap ($20) Chinese reflection bridge off the internet (NOT ebay) which had appalling directivity (10dB), I decided it was time to build my own to be used with my HPSDR VNA.

A survey of the internet and some recommendations pointed me at the designs by Sam Wetterlin. There were two possible designs, I chose the three bead balun version (mainly on size grounds) This used a Minicircuits transformer and a ferrite bead Balun. I bought some "TC1-1-13" off ebay but these had a pinout different from the Minicircuits catalogue and didn't work well. N1JEZ provided a couple of the genuine articles from his collection which worked perfectly The rest of the parts were bought from Mouser and I designed the two tiny PCB with 0805 components and had them made by ExpressPCB 

Assembly took five minutes. The two PCB are separated by a brass strip which supports the balun.  I had some Glass fibre tape which I used to stop the Balun moving around on the support. I soldered an smt resistor to the PCB as the reference load to save using a 4th SMA for an "external load.

Complete Reflection Bridge

Closer view of the input circuit. The TC1-1-13 is the small square on the right

Directivity was very good, exceeding 30dB from 0.47MHz to 1GHz, more than adequate for my present needs

TF3LJ Power and SWR meter

Last year I built the TF3LJ Power meter and subsequently gathered the parts to build his Power and SWR meter.  It was time to finish the project.

 

The first consideration was the directional coupler. I remembered I had built one for the ill fated W7IEV project so this was unpacked. The basic unit is rated at 100W and has -40dB coupling for both forward and reverse signals. I found the fixed 20dB BNC attenuators bought for the W7IEV project so that would give -60dB for both forward and reverse signals.

 

I also found the two AD8307 detector boards from the W7IEV project so all I needed was to mount the Teensy 2++ arduino style module on a carrier board and was ready to go.

 

I mounted the modules and an LCD in a 8"x6" x 3"  Box. Probably would have gone in a smaller one but it was available. The software was installed from Lofturs Site and all worked smoothly.

 

The software does have the ability to produce an alarm signal when a preset SWR is exceeded. This could be used to Inhibit an amplifier. It is the phono connector on the back panel below.

 

Front Panel View (KX3 into two 50 ohm dummy loads)

 

Inside view. Teensy is on the left then 2 detector modules

 

N7ART Audrey II 432MHz Amplifier 240V Conversion

A week ago I was taking stock of my 432MHz amplifier collection. The one I had used the most was the N7ART Audrey II 2x3CX800A7 amplifier I bought 20 years ago. Steve made a wonderful job of building the amplifiers as the pictures below show. Unfortunately the PA was wired for 110V so couldn't be used in the UK. The 2600V PSU was not an issue as it was wired for 240V. It was time to investigate what would be needed for conversion.

Luckily I still had the original Documents in which Steve gives the part numbers for the 240V components used in his 240V version. The relay supply transformer in the amplifier (Triad FD-4-12) was already dual voltage primary so did not need changing. The heater transformer was a Stancor P8857 which being 115V only primary would need changing to a Triad FD-7-16 which would also mean changing the resistor in series with its primary from 20ohm 20W to 150 ohm 20W. The blower was a Dayton 4C446 115V 50/60Hz which would need changing to a Dayton 2C915 230V 50/60Hz. The search was on

The Dayton 2C915 is no longer made but I found an equivalent on ebay for $68. Mouser had the FD-7-16, but on 4 week delivery but someone had one on ebay at $10 shipped, so both were bought along with a 150 ohm 30W resistor from the local emporium

This weekend the components were installed. The blower had a different shaped outlet flange so some chassis filing was needed but fitted otherwise. The new transformer had different fixing centres which needed to be drilled along with the mounting holes for the new resistor.

Top View of amplifier after modification

Bottom View of amplifier after modification

  The amplifier is now ready to go on UK mains!

An evening on 474kHz at WH2XES

Tonight I went and visited W5LUA to Christen his new experimental licence WH2XES on 475kHz.

 

In preparation I had built a modified Ultimate 3 Transmitter by Hans Summers http://www.hanssummers.com/ultimate3.html  When originally built with the 2N7000 the output spectrum was nasty, especially LF of the output signal so I looked at alternates. I ended up using the filtered sine wave output from the DDS (the original used the square wave output) to drive an ERA2 and a 2N5109 PA from kitsandparts to a lowpass filter. This produced 200mW into 50 ohms.

 

 

Ultimate 3 New output Stages

 

I also built the GW3UEP 100W IRF540 amplifier:-

100WAmp with Arduino Protection circuitry

 and a matching 100W Low Pass Filter to a design by WA1ZMS

 

 

We started the evening with the 200mW on WSPR into AL's 80m dipole with inner and outer strapped together and tuned against ground with an LC network resulting in a 2.8:1 SWR

 

We immediately got reports from the local

 

01:04   WH2XES   0.475722   -12   0   EM13   0.2   WG2XIQ   EM12mp   93km  

01:08   WH2XES   0.475723   -12   0   EM13   0.2   WG2XIQ  

01:12   WH2XES   0.475722   -11   0   EM13   0.2   WG2XIQ  

01:16   WH2XES   0.475722   -12   0   EM13   0.2   WG2XIQ  

01:20   WH2XES   0.475722   -12   0   EM13   0.002   WG2XIQ  

01:24   WH2XES   0.475722   -12   0   EM13   0.002   WG2XIQ  

 

(we adjusted the power to transmit EIRP at 0120)

Enthused we hooked up the PA which started taking a lot of current but was producing lots of output

 

01:32   WH2XES   0.475722   +10   0   EM13   0.002   WG2XIQ   EM12mp   93   175  

01:32   WH2XES   0.475728   -22   0   EM13   0.002   KF5JIA   EM15qe   194   11  

01:32   WH2XES   0.475729   -7   0   EM13   0.002   WG2XXM   EM15lj   213   0

 

(we forgot to adjust the power setting on WSPR) The signal at WG2XIQ increased 22dB and we were heard in OK. Unfortunately on the next transmit period the supply current limited with no output. We hooked up the exciter to the antenna while we investigated

 

  01:48   WH2XES   0.475722   -19   0   EM13   0.002   WG2XIQ

 

The received signal level had dropped 7dB. We noticed the SWR in the shack was now 8.8:1. We let it run while we braved the chiggers in the field to look at the matching unit

      

  01:52   WH2XES   0.475722   -19   0   EM13   0.002   WG2XIQ    

  01:56   WH2XES   0.475722   -20   0   EM13   0.002   WG2XIQ    

  02:00   WH2XES   0.475722   -19   0   EM13   0.002   WG2XIQ    

  02:04   WH2XES   0.475722   -19   0   EM13   0.002   WG2XIQ    

  02:08   WH2XES   0.475722   -20   0   EM13   0.002   WG2XIQ

 

Opening the box we were met with a nasty smell. There were scorch marks on the box and the red enameled wire on the 180uH toroid was now a brown scorched wire

 

 

 

 

Some more work needs to be done on the matching unit! Needless to say the $1.25 IRF540 needed replacing, but they are in stock at the local emporium 

 

 

Auto External Reference switching for the ANAN-10 HPSDR

Over the period I have owned the Anan-10 SDR Transceiver the only issue for me has been that to use an external 10MHz reference it has to be taken apart and links changed, which runs the risk of damaging the tiny RF cables. Last August G8ONH/G7OCD mentioned on the OpenHPSDR reflector they were working on a small PCB to be mounted in the ANAN-10 that would automatically switch the ANAN-10 to use the external reference when one is plugged in. This week I managed to obtain a board from G7OCD and set about installing it.

The board is very small:-

PCB size compared to a quarter

ANAN-10 Innards before Installation

All I had to do was plug the 4 headers into PCB and solder the pins to the PCB:-



PCB after Installation

 The 2 holes on the PCB are to allow a jumper to be fitted to ground the SMA connector "outer". A header wasn't supplied so I fitted a right angle 2 pin male connector to the PCB and used one of the now "spare" jumpers  on it

Jumper block added

Including assembling/disassembling the ANAN-10 and putting the board in place it took only 15 minutes to complete. 

My Rubidium drives a DEMI 10-4 four way 10MHz splitter. Attenuating the output with 50Ohm attenuators the minimum level to achieve "autoswitch" was -3dBm which is just fine for my setup

Note that when using the board NOTHING needs to be done to the PowerSDR settings to accommodate the board.

MTR3 kit

Steve KD1JV is a prolific producer of compact rigs for mountain topping. A few years ago I bought and built an ATS3 and an ATS4 5 band rigs which were great fun, Unfortunately I sold them to finance the KX3.

My ATS4B

I really miss them, so was excited when Steve announced that he was going to do another run of 150 Triband MTR (mountain top radios, AKA MTR3). The sale was the usual "first come first served" after the web page was launched, but I was lucky enough to get one of the kits. When the kit arrived it sure was small, it makes the KX3 look enormous!:-

Shortly after it arrived Steve announced he was sending all buyers an updated cpu chip to fix a bug, so I waited for that to arrive before starting construction to avoid having to desolder the original chip. I decided to build it for 40/30/20m. Building it took around 3 hours, including alignment. It was christened with a couple of QSOs on 20m using the Alexloop antenna Comparing the two,  I prefer the ATS due to its lcd frequency display avoiding the need to memorise the scrolling digits on the lcd display, but the MTR3 is much smaller!