Monday 15 December 2014

LED lighting Interference...solved, thanks to G4BVY

A couple of years ago I was convinced that swapping out the apartment lamp lighting for LED lights would save money so I bought a load of GU10 6W LEDS from Homebase and Installed them. Disaster! When any lights were turned on the noise floor on 10m and above shot up by a considerable amount. Classic FM disappeared on 100MHz. Classic FM on DAB disappeared.

Recently this situation has resulted to running some Tuesday night UKAC events by the light of a (non LED) bedside lamp, with all other lights off!

I was told LED lights had got better in the intervening years, interferencewise, so I bought some more  LED samples from Tesco, B&Q and recent samples from Homebase to see if they had. The Tesco ones were the best of the collection, but still produced a noise floor increase.

It was at this point that Roger G4BVY posted to the MHRAC reflector that he had bought some Phillips 4.5W LED in twin packs for 9.99 from Wickes from which he could detect no interference and they were quite bright. Off to Wickes in Worcester to buy a couple:-

The GOOD LED Lights

Installed them in the stairs lights listened on 144MHz turned the lights on...Nothing!  The noise floor did not increase at all!

I was intrigued how much the noise floor increased on 2m for each type, so I needed a calibrated receiver. The easiest option was to use the SDRIQ in continuum mode with my Nacton transverter for 144MHz. The increase in noise floor could be easily seen in dB.

The effect of turning on the Homebase lamp on the 2m noise floor

The overall results were Interesting:-

Homebase  6W (2012)             24dB
TCP 5W (Homebase)              26dB
TCP 4W  (B&Q)                     18dB
Tesco 5W                                 8dB
Phillips 4.5W                           0dB

The Phillips was by far the best. Interestingly Homebase don't actually sell their own brand any more, they only sell TCP so I got one of their 5W ones. haven't improved their version, It was returned as "unfit for purpose"! I was so impressed by the Phillips I went back to Wickes to get replacements for all the other Homebase lights.  Before fitting the new ones I decided to see how the Homebase LED interference varied with frequency. This time I used the SDRIQ with external Nacton transverters for 6, 4 and 2m. The noise floor increase was as follows:-

7MHz                0dB
14MHz              5dB
28MHz              7dB
50MHz              16dB
70MHz               18dB
144MHz             24dB

As a check, I also measured the results using my ANAN-10 as the receiver. The results were within +-1dB

The remainder of the Phillips LED were fitted. For the record the twin packs have the UPC 8718291789994. I looked on all the frequencies I had (even 136kHz) but couldn't find a noise floor increase. Good news all around; lower noise, decreased power consumption and Meg says that, unlike the previous LEDS the increased brightness will even support her sewing! Thanks Roger.

Thursday 4 December 2014

Seperate Receive and transmit paths for the Elecraft K3 Internal K144XV Transverter

When using the Internal K144XV  2m transverter in my Elecraft K3, it has a single BNC connector on the back panel for receive and transmit signals. Having obtained an HA8ET 2m mast head preamp I needed to separate the two signal paths to avoid putting RF up the back of the preamp.

Elecraft in the past have said it is possible to connect a separate RX antenna to transverter but nothing has ever been documented! The only clues have been the comment  in the K144XV manual about not removing links P2 and P3 inside the transverter. Time to investigate!

I took the cover off the K3 and the K144XV transverter and found that if the link between pins 1 and 2 of P3 was removed the receiver went deaf.  Pin 3 was ground.  I connected a coax cable with centre conductor to pin 2 and the braid to pin 3 the GB3VHF beacon could be heard on my collinear. The radio still produced the normal 9W out of the BNC connector on the back panel.
I did not want to solder to the header so I found a 3 pin female header (previously used for arduino shields) and soldered a piece of RG174 with a BNC socket on the other end, which hung out of the back of the lid panel. I did look at tidying up the cabling by using the AUX RX BNC connector but this would mean taking the K3 apart and removing the sub receiver every time I wanted to change between internal and external 2m antenna switching.
For reference P2 link allows the Receive IF output to be diverted from going to the KXV3A module. P8 link enables the DC voltage on transmit on the centre pin of the Transmit port.

I have written up the "Seperate  Receive and transmit paths for the Elecraft K3  Internal K144XV Transverter" modifications with pictures at

Saturday 22 November 2014

Exercising my 2300MHz NOV

After seeing the announcement that the 2300MHz NOV were finally available I decided it was time to get one. After reporting some disparities between the RSGB website and the application form (eg the website said "main address only"; the form allowed a list of portable locations) I managed to get an NOV. The issues have been corrected

 For EME operation from the USA one needed to cover 2300, 2304 and 2320MHz so a Transverter for 2300MHz was already available as written up at My PA using the driver stage from the Spectrian Amplifier produced 10W, I didn't have enough drive to get the full 30W.

On Thursday evening I tried a sked with G4BAO at 170km. I used my only  13cm antenna, a 25 element (the one with the horn feed) taped to a cardboard box pointing out of the bedroom window.

It was suggested to try ISCAT-A digital mode.

213800   1 -12 23.2  -65   0 *  G4FRE G4BAO                   12 10 10  4.5
213900   1 -11  2.0  -65   0 *  G4FRE G4BAO                   12 10 10  2.2
214000   3  -9 16.5  -65   0 *  G4FRE G4BAO                   12 10 10  4.5
214100   1 -10  2.0  -65   0 *  G4FRE G4BAO                   12 10 10  2.2
214200   4 -10 12.0  -65   0 *  G4FRE G4BAO R-15 R-15         22 10 10  8.9
214300   3 -10  3.1  -65   0 *  G4FRE G4BAO R-15 R-15         22  9 10  4.5
214500   6 -10 19.8  -65   0 *  RRRR RRRR G4BAO               16  3 10 17.8

It took a while to complete the QSO, aircraft reflections were non existant but we completed for my first trop QSO on 2300.2MHz. A quick try was made with G4DDK at 246km but no two way QSO

On Friday morning I tried again with G4DDK. His signals were weaker by some 5dB than the previous evening but were there most of the time. It took a long time to get a signal report exchange on ISCAT-A. 

105100   1 -15  6.5 -118   0 *  G4FRE G4DDK                   12 10 10  8.9
105200   3  -9  3.1 -118   0 *  G4FRE G4DDK                   12 10 10  4.5
105300   3 -11  5.4 -108   0 *  G4FRE G4DDK                   12 10 10  8.9
105400   2 -13 12.0 -108   0 *  G4FRE G4DDK                   12 10 10  8.9
105500   1 -12 21.0 -129   0 *  G4FRE G4DDK                   12 10 10  4.5
105600   2 -12 10.9 -129   0 *  G4FRE G4DDK                   12 10 10  8.9
105700   2 -14 19.8 -129   0 *  G4FRE G4DDK                   12 10 10 17.8
105800   4 -10 23.2 -129   0 *  G4FRE G4DDK                   12  9 10  8.9
105900   1 -11 14.3 -140   0 *  G4FRE G4DDK                   12 10 10  4.5
110000   2 -13  9.8 -140   0 *  G4FRE G4DDK -17               16 10 10  8.9
110100   2 -13  5.4 -140   0 *  G4FRE G4DDK -17               16  5 10  8.9

Signals were not "bursty" as would be produced by aircraft, so we switched to JT65c, which is good for weak, continuous signals. The QSO completed quickly:-

110400  8  -10 -1.7 -137  6 *      G4FRE G4DDK JO02          1  10
110600  5   -9 -1.7 -143  7 #      G4FRE G4DDK JO02    OOO   1  10
110800  7  -16 -1.7 -143 11 *      R-17                      1   0
111000 10  -23      -142  2   RRR ?                               
111200 10  -22      -145  4   73  ? 

The lesson learnt is that the digital mode used needs to be carefully chosen based on the received signal characteristics

Sunday 9 November 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 Clarke 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 on Sunday afternoon 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 350W without tripping the generator. The AC voltage still only dropped 1V.
I am most impressed with its performance.

Friday 7 November 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 conditioners 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, forget UHF/Microwaves!. 
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 what were called on ebay as  "switch leads" with 8mm eyelets. 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 27 September 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 23 September 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 my WinkeyUSB in a drawer along with the V3 chip which I installed. 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 17 September 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 about the question, 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 was put onto Transmit by CAT signals

Monday 15 September 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  

Saturday 13 September 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 7 September 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 31 August 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 at that time!

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:-

Tuesday 26 August 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 9 August 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 a 3 month wait. 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 cancelled the order and reverted to the external 70MHz DEMI Transverter
Closeup of KX3-2m module

Friday 18 July 2014

432MHz Solidstate Amplifier Completed

Over 3 years ago I bought a W6PQL 432MHz amplifier module  with the matching LPF/Directional coupler. Before I moved out of the McKinney house I quickly mountedthe modules on a heatsink inside an aliminium chassis to protect it in storage. Over the last few weeks I have finished the metal bashing thanks to WA5YWC and built a PIC controller and LCD display.  The biggest issue was testing it as I no longer had a 432MHz transmitter in the USA. W5LUA kindly offered to let me use the facilities in his shack which included drive source, Power meter and dummy load.
The first thing we learnt was that the RF got everywhere inside the chassis. Initially there was no screening around the PIC board which caused measurement issues. After a trip to the local hobby store for some .015" ali sheet and the donation of many 1nF bolt in feedthroughs by W5LUA that issue went away. It was necessary to put a screening can over the directional coupler (W6PQL only suggests it for his 1kW amplifier) as the calibration of the bargraph meter changed dramatically when the cover was put on the box
When completed the amplifier gave 420W for 6W drive when running 17A at 48.0V. Looking at the W6PQL figures I could hit the amplifier harder to get the full 500W but this way I have a safety margin. All harmonics were over 65dB down on the fundamental power.

Monday 7 July 2014

Fujitsu 251-9735-010 6GHz amplifier fixed

I was given a Fujitsu 251-9735-010 6cm 5W amplifier by WA5VJB about 12 years ago for my Transverter but never got round to trying it out, this weekend was an opportunity. I borrowed a 5760MHz California Microwave brick which gives 16dBm at 5760.000MHz from W5LUA to save needing to retune my DB6NT 5616MHz LO. This needed a -19V supply, provided from my 57A 28V PA supply (yes overkill!) According to Kent's notes the PA needed 4A at 12V and 200mA at -12V for the bias for which two other additional PSUS were found (a variable one and the 13.8V rig supply). Applying the -ve bias the power supply immediately current limited, but the resistance to ground from the bias supply lead was 12kohms. Time to take the lid off. LOTS of screws later the lid was off. The -ve bias supply feeds a 7905 regulator. As a quick test (to avoid more screws) the regulator was cut out and the -5V applied to the regulator output pin. With the 12V supplied 5W was seen. The control board was removed and a new regulator fitted. It still produced 5W. 
The opportunity was taken to measure some voltages and currents. Full output was produced until the positive supply dropped below 12.00V. Full output was produced until the negative bias dropped below -6V, The measured currents were 12V at 3.9A and -12V at 50mA. It was noted that the detected output was a negative voltage. Not good for Microchip PICs! The detector diode was reversed and resistors adjusted so that the detected output was +10V at full output. 

Thursday 19 June 2014

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, 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

Friday 6 June 2014

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 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

Wednesday 4 June 2014

NavSpark Arduino compatable GPS receiver

Before Christmas I saw a posting for NavSpark on the crowd funding site  From the web page  "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    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

Sunday 1 June 2014

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

Monday 26 May 2014

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!

Tuesday 20 May 2014

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  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