Sunday, November 9, 2014

Time to buy a Generator

Having now put the power provision requirements in order inside the car, there are occasions when more power is required and a generator is needed. I started looking at what was available at around the 1kW level. In the USA I had a Honda EX1000 1kW for 15 years which worked well and provided ample power, but looking at the UK prices a cheaper solution was needed! I noticed while researching that nowdays there were "generators" and "inverter generators" which were new to me so I sought the advice of the local "portable operation with a generator" owner, Roger G4BVY. After much discussion I decided that the main advantage of the inverter generator is that the volts and frequency are not so controlled by the motor speed and are therefore better for "delicate electronic equipment" and they are lighter.
With this in mind I started looking online at the "normal" Clarke G1200 generator and an Inverter Clarke IG1000. The most noticeable difference was the weight, The G1200 was 25kg the IG1000 was 15kg. It was time to physically look at them. Roger had recently received a postcard with VAT free Granger purchases at the local machinemart in Worcester; time for us to visit.  There was indeed a noticeable difference in weight, the IG1000 could be easily moved with one hand, the G1200 took effort. The IG1000 was well enclosed; ideal for wet Welsh mountains. The decision was made to buy the IG1000, even though it was slightly dearer,  during the voucher validity window the following Sunday. I was at this point cautioned by others about the amount of RF noise the Inverter can produce, but I went ahead.  The shop was visited and the boxed generator easily fitted in the back of the Jazz with the back seats up.

The following day a visit was made to the Rogers to christen the generator. Following the instructions, (most noticeably waiting 5 minutes for the new oil and petrol to get everywhere it should),  the generator started. With no load it produced 230V. At this point the calibrated dummy load was found  (a 600/1200W switchable fan heater). Applying the load caused the motor to "think" briefly but the voltage only dropped 1V. We  decided it was time to look at the waveform so an oscilloscope was extracted from the shack. There was NO difference in waveform between 0W and 600W. It wasn't a pure sine wave but it was very stable

Next test was RF noise The Elecraft KX3 was moved all around the generator (which had been given an antenna...the mains extension lead) but no noise could be found through 6m.
The following day, while setting up for the 2m UKAC I ran my 2m setup from the generator. Elecraft K3 + 500W I0JXX LDMOS module based PA ran off a 48V switcher power supply, It produced the usual 400W without tripping the generator. The AC voltage still only dropped 1V.
I am most impressed with its performance.

Friday, November 7, 2014

Regulated 13.8V mobile Power supply

Having minimized the cable voltage drop in the car portable wiring system I noticed I was only getting 60W out of the K3  unless the engine was running when I got the full 100W.  This was due to the drop in the supply voltage from 13.8V to 12V. What was needed was a box that maintained a constant 13.8V irrespective of the volts being supplied by the car.

I vaguely remembered that N2CEI had battery conditioning modules in his rover setup.
The large box at the rear of the trailer contained 2 car batteries and 2 voltage condition which maintained 13.8V. So I asked him who made them. He pointed me to his supplier TG Electronics . They did the The New N8XJK Boost Regulator:-
Voltage: Input: 9 to 15 Volts DC.
Output voltage: up to 15 Volts DC at 30A.
Dimensions: 7" wide x 3.5" deep x 2.25" high 
 I also found MFJ did a similar unit "MFJ-4416B Battery Voltage Booster 12V" for $160, however having had reliability issues with MFJ equipment I decided to go with the TG Electronics unit. I ordered the optional 30A thermal trip to save having to replace fuses. It took a week to arrive.

The unit has a UHF socket which can be used to RF trigger the unit and place it in circuit when in transmit mode. Note this only works on HF/6m. 
Performance was most impressive. When providing 20A at 13.8V from an 11.1V Input there was only 5mV RMS ripple on the output and the K3 produced 100W. I also had a listen on the KX3 while on transmit and no noise could be heard from 160m through 6m.
Another neat feature is that I could set the unit to put itself into bypass mode and sound an alarm when the input voltage dropped to 11.0V.  

Power Cabling in the car for portable operation

I have been looking at providing 12V power for portable operation. Until now I have been running the K3 and transverter by using Jump leads from the Car Battery. This has caused intermittent contact issues and large Voltage drops in the past, so a better solution was needed.
In my connector collection I discovered some 120A red and black power pole connectors. I put these on the end of a pair of Halford jump leads after removing the crocodile clips.

A pair of connectors was attached to the battery using "switch leads" with 8mm eyelets from ebay. For the other end of the cable I made a breakout box. I got a large plastic box from Maplin and mounted a pair of 120A connectors on one end and five regular powerpole power connector pairs on the other end.

The connections between the connectors at both ends were made through a 30A thermal switch

To allow connection to a car without the prewired connector I attached the crocodile clips to a pair of connectors to allow connection to the battery by this method

Saturday, September 27, 2014

RSGB National Hamfest 2014

In my early days of Amateur radio I used to visit THE national radio Rally at the Granby Halls in Leicester in November. This finished many years ago and it has now morphed into the RSGB National Hamfest that is hold at the Newark & Notts Showground in October. Viewers of the BBC Programme "Bargain hunt" will have seen it many times as it often has antique fairs used in the series.
It is held over two days, Friday and Saturday so I decided to go on the Friday. It is a 120 mile trip from Malvern which took 2.5 hours, arriving 15 minutes before the official opening time of the indoor exhibits but the flea market was fully in motion, and it was sunny. I made a few  purchases from the Fleamarket. A Wouxun KG-UVD1P 144/70MHz FM Transceiver , (now I can speak to WA5VJB when he comes to England) a 13.5V 22A PSU which cost £1 and a bag of fifty 10uF 25V tantulum Capacitors for 50pence . Most Interesting was meeting G4AEH who was assisting a seller and catching up on old times, mentioned in my blog entry "blast from the past
I then went indoors. There were RSGB stalls and the RSGB bookshop, so I used my £5 off voucher to buy the EI5GQ "Building a Transceiver" book (which was technically interesting but included some "non sentences" making comprehension hard!).  I had a "long" lunch with G4HUP and caught up with G3XTT, G4BAO, G7OCD, G4KUX, G4FSG and G3CWI.  I picked up the pre-ordered 4+4 ele 6/4m antenna from Innovantennas and just about fitted it into the Car. There were a few interesting items, if one looked close enough. One was a Telford Communications TC10 receiver that was used as a 28-30MHz tunable IF for 2m/4m when combined with the matching G8AEV converters and a Hughes 1077TWT (which I used for the 24GHz USA record QSO) which had a beaten up PSU . Both were resisted, I did go to buy a moonraker tripod based mast, but they sold out at the reduced price very quickly and no more would be available until Saturday; too late for me. I did buy a "drive on" base for my portable mast and a couple of pieces of ex-military RG213 for the new antenna. The rally ended at 4pm, sharp. The return took almost 3 hours due to the dense Friday afternoon traffic. Overall an Interesting day out

Tuesday, September 23, 2014

Interfacing multiple 9 pin RS232 connectors to the Acer V5 Laptop

Having got the Audio interfacing to the V5 sorted it was time to look at the serial data. The V5 has no RS232 connectors and only 2 USB ports.  Normally I have one serial connection to the radio (9 pin), one to the GPS (9 pin for timing) but now I needed an extra one for the winkey usb (true USB) having recently discovered mine in a drawer. I could have used  a USB hub but past experience has found them unreliable in RF environments. Searching my goodies box I found my Edgeport /4 USB serial converter  (bought off Ebayusa for $10) that I used to use on my old Win XP contest computer. This box has one USB connector and four 9 pin serial sockets.  I could connect the Radio and the GPS to the Edgeport box and the Winkey USB directly to the computer, leaving 2 spare com ports.
Configuration software and drivers were available for Windows 7. Comports can be allocated as desired,  I used COM3, COM4, COM5 and COM6. WINKEY USB has COM2

Wednesday, September 17, 2014

Interfacing the Elecraft K3 to an Acer V5 Laptop

Having upgraded my Acer Aspire one netbook to an Acer V5 laptop which has a faster processor and larger screen, I was surprised to see it had a single connector for Audio Input/output and was therefore incompatible with all the Interface cables I had made for the K3/IC706/FT817. As a quick fix I plugged in my USB soundcard into the V5 which did have separate audio in and out  while I made some cables
I had a suspicion the TRRS connector on the Acer was wired like the one on the Nexus 7 as I discovered when building the PSK Interface . I searched the Acer manual but that was unhelpful. I called Acer helpline but even their Tier 2 technical support had not a clue, so I assumed it was the same
I found a mono 3.5mm lead for the K3 Line In connection, a stereo 3.5mm lead for the Line Out and a 4 pole TRRS plug.  I wired up the connector to feed audio into the K3 and that worked fine. Feeding audio out of the K3 into the computer was a failure. It was unsuccessful and it was impossible to disable the Laptops Internal Microphone.  Measuring the open circuit voltage on the Mic Pin showed 2.8V, obviously intended for an Electret Microphone. When the K3 was attached this voltage dropped to 0.8V, the Line input obviously had a DC path. Searching the internet I found a few articles on using a resistor of a few hundred ohms on the mic input to control Play, forward and stop of a media player on a Nexus 7. I wondered if a load resistor must be used to emulate the current drawn by an Electret Microphone to disable the Internal Microphone. Electrets are typically 1600 ohm, so I put a resistor across the mic input and used a 10uF capacitor to stop the K3 DC loading the port. The final circuit is as follows:-
This worked fine, but now it needed Tidying up. By using a 1600 ohm 0805 size resistor and an 0805 size 10uF ceramic capacitor the components could be fitted inside the plug shells.
NOTE: No PTT signal was needed via this interface as the K3 transmit was controlled by CAT signals

Sunday, September 14, 2014

Arduino Uno and GPRS shield

While looking at the design of the OZ7IGY beacon I noted they were using a GPRS shield  to remotely manage the beacon via cellular I could see all sorts of applications for the system. I looked at the module they were using and decided it was too expensive to play with and looked for cheaper alternatives.  I came across the EEGTECH WGW-06633 which was only $33 but did have audio in and out so I ordered one.
A few weeks ago I came to the conclusion that there was no point in doing RSGB 50MHz and above contests without having access to ON4KST. After consulting with G4BVY I bought a Huawei E5330 cellular to WIFI converter and got the cheapest cellular plan I could find from giffgaff which would give me 250MB of data and 200 minutes of phone for 7.50 a month. They also supplied the sim. O2 were the carrier, which was unfortunate as they have awful coverage around here, but it was worth a try.

The internet revealed a very useful tutorial at This has examples for making voice calls, sending sms, receiving sms and reading html files all of which worked fine.
The ultimate test that I achieved was to have my shack PC monitor 10m wsjt JT65B signals and upload the decodes to my web site. The arduino and shield recovered these spots from the website and sent an sms  of them to my phone. I can see some useful variations of these scheme being deployed on a long term basis