Monday, December 15, 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. 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 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, December 4, 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. 

Saturday, November 22, 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, 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