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

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 carpark we were the last car there:-
 
 
 

Tuesday, August 26, 2014

August 50MHz UKAC

As GW5NF was having trouble with his TS2000 FMing on 2m and 6m(as reported by TF3ML/P!)  Meg offered to loan him her Elecraft K3 while it was in for repair.   Looking at the calendar a 6m UKAC was impending so we decided to take it and install it that day and see how it worked under the GW0FRE call. It took just a few minutes to install the K3 along with the matching KPA500 and interface it to his computer. We had a listen on 6m and heard a few signals so tried calling them Worked were IK5ACO(JN52),  ISOCDR(JN40) and ISOBSR/P (JM49) Next we hooked up the Microwave modules 70MHz transverter for a listen and heard CS5BALG/B (IM67) and CT1HZE (IM57) calling CQ on SSB who came back first call with our 7W! After a meal break,  6m produced EA5GLN (IM98)and EA7/G4GCP (IM76) then it was time for the contest.
Deciding to live dangerously we installed the N1MM software 20 minutes before the contest began!  The contest started with stations in Scandinavia. The best was OH2TP(KP20) at 1920km, but it was nice to work SM4IVE other than via the moon. Conditions then died. The contest ended with a burst of Italian stations giving the best DX,  IW8PQU (JM88) at 2078km. 60 stations were worked. The complete spread geographically is as follows: 
 
 
 
 
Looking at the UK stations worked it is noticeable the lack of Northern Stations, due to the large mountain less than a mile north of the QTH blocking takeoff that way:-
 
 

Saturday, August 9, 2014

KX3-2M KX3 144MHz Internal Transverter

The KX3-2m module is lower left
I ordered this during Dayton and it arrived this week after 3 months. It took about 20 minutes to fit into the KX3. Measurements showed 2.5W output off 13.8V and the W5HN/B beacon was audible on a whip attached to the SMA antenna connector, so sensitivity seems ok.

I originally also ordered a 4m transverter module, but after seeing warnings about the limited number of times the two RF cables interconnecting the modules to the KX3 could be plugged/unplugged, I gave up on the idea and reverted to the external 70MHz DEMI Transverter
 
 
Closeup of KX3-2m module