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 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, 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 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