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 http://rudius.net/oz2m/ngnb/management.htm. 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 http://www.seeedstudio.com/wiki/GPRS_Shield_V1.0 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  

Saturday, September 13, 2014

50MHz RF survey of the Malvern Hills

After operation from Black Hill last weekend I decided to see how it compared with the other hills in the Malvern Hill Range. On Summer Saturdays there is a Bus from Worcester to Ledbury that stops at British Camp which avoids the need of doing a round trip along the hills) to get to a car parked at British Camp. The bus stops next weekend so this was the weekend to try it. It was also good exercise being about 8km walk in total and rising to 1400'

As there was no contest this weekend comparison would have to be by looking at 6m and 2m beacons. Again using the KX3, but this time with the 6m extension on the whip antenna. The following is a summary of the 6m results

Black Hill GB3BUX 529 , GB3BAA 539, GB3MCB 549, GB3RAL 529
Pinnacle Hill GB3BUX 549 , GB3BAA 549, GB3MCB 559, GB3RAL 539
Jubilee Hill GB3BUX 519 , GB3BAA 539, GB3RAL 529
Worcester Beacon GB3BUX 519 , GB3BAA 539, GB3RAL 519
North Hill. GB3BUX 549 , GB3BAA 539, GB3RAL 519

GB3VHF on 2m  being to the East of all of the hills did not vary in signal strength. GB3BAA and GB3RAL similarly  are to the East and were little affected by location. I was a little surprised that RAL was consistently weaker than BAA. GB3MCB is South West and on any hill North of Pinnacle hill is blocked by the other hills hence its no show.
 
Pinnacle Hill looking South from Perseverance hill
 
Worcester Beacon looking North from Perseverance hill
 

Sunday, September 7, 2014

144MHz Portable Backpacking Activity


Looking East from Black Hill
 
 
Having worked a few stations early on in the 144MHz September contest from the house on the dual band collinear,  I wondered how much louder they would be from the top of the hill. As the contest continued until 3pm clock time on Sunday and there was a backpackers contest 1200 to 1600 there should be a few signals to work.  I packed up the FT817, the KX3 with the internal 2M module, a 7AH battery and the whip off my FT817 (the only 2m portable antenna I have) in my rucksack and headed up the hill.

A few signals were heard on the east coast so these were used to compare the receivers of the FT817 and the KX3. The KX3 won by a mile, so the FT817, despite its slightly higher power was packed away. I discovered I had left the KX3 lead for the battery so it had to be used all the time on the internal cells.

The biggest challenge was how to hold the KX3 in one hand, use the microphone in the other AND put entries in the log, something I will need to work on

To avoid confusion with G4FRE used from home I used G0FRE/P, which did confuse one stations lookup database! A total of 22 stations were worked the best DX being F6KCZ/P at 324km. One ON and two PA were heard but too weak to work.
 

 
After the contest finished I walked along to the Malvern Hills Hotel for an Ice cream from the stall opposite the Malvern Hills Hotel and the British Camp Car Park

I need to consider investing in a small, transportable beam like an HB9CV for such outings. I already have one for 4m and 6m in the loft but I only have a dual band collinear for 144/432!

Sunday, August 31, 2014

Telford Rally Weekend

This weekend was the annual Telford Radio Rally that is held at the The Enginuity museum at the Ironbridge Gorge. This area also has a lot of interesting museums so it was decided to make a weekend of it. We drove up Saturday morning, following the Tom Tom route that was an alternate to the motorways which visited lots of back roads and no towns! First we went to the Coalport China museum, then the Tar tunnel and finally the Jackfield Tile museum before retiring.
Sunday morning we followed the very noticeable Fluorescent road signs to the rally and parked in the adjacent AGA works (of stove fame)  to the Enginuity complex.
 
M0FRE at the entrance to the Rally
 
 
There were a selection of stands outside in the courtyard and more in an inside hall. I bought a 12v 7AH SLAB to power the KX3, guy rope, an EF183 (for my PW 6AF11 RX) and an 8W 6cm amplifier (from the G3OHM club stand). I did resist the British Tube tester for 250 pounds! I spoke with Gordon, G8PNN who I had not seen since staying overnight at his place on the way back from the GB2YS/GB2ZR expedition in Aug 1986...he still remembered the car I had!
 
After the rally we walked uphill to the Darby House museum which were also very interesting. On the way back to the car we noticed the date the Rally building was built, you never see such age at USA hamfests! 
 
 
When we got back to the Rally car park we were the last car there:-