Sunday, December 30, 2007

GI7B Six Meter Amplifier Project - Update 8

First RF test and found the tune variable capacitor totally meshed out, then I removed few plates and measured the capacitance is in between 4.5 to 10 pF. The tank coil also cut one Turn, now is 3 turns. The load capacitor is half-meshed, just fine.
After that, test Starting with 5 W of drive from a TS-600, gave 85W on the output first time, which equal to about 12.3 db gain.
Increasing the drive up to 10W brought 150W output, equal to 12.07 db gain.
I stopped at this point because the 150W dummy load already very hot, will test later with a high power one.
I also installed the top cover with ventilation holes.

Friday, December 28, 2007

GI7B Six Meter Amplifier Project - Update 7

Last evening round up all connections and perform initial test at the input SWR. At firs, the SWR is quite high with 1:3 , modified the coil to 4 turn 13 mm dia. with good result at 1:1.2.

After that, connect plate voltage and measured the plate idle current at 80mA, which indicated it is correct.

Now the amplifier is ready to go for load test.

Thursday, December 27, 2007

GI7B Six Meter Amplifier Project - Update 6

Logan (VR2XRW) gave me a 10mm ferrite rod for the filament choke, it is in place all together with the input tune, consists of two Arco variable capacitors and 15mm dia. coil.

The GI7B tubes are in place. They were supplied with the filament votlage for few hours.

Monday, December 24, 2007

Front Panel

Plate Voltage and Amperes meter installed on front panel, it fit well and look good.

The meter at right hand side showing 2050 V DC, scale need to calibrate later.

GI7B Six Meter Amplifier Project - Update 5

The high voltage supply was wired up.
AC 220V input to primary winding (240V) and secondary measured at 800V tapping is 730V. After rectifier and voltage doublers, measured at 2050V DC. It meets with the plate voltage of the GI7B.
The soft key and bias board PCB is mounted at the bottom, nearby the T/R relay.

Saturday, December 22, 2007

Plate Choke

The plate choke is made from 50-turns, 22swg(purchased from UK), close wound on a 80mm length of 20mm PTFE rod(purchased from Apliu Street)

It is tapped hole in one end for support.

Friday, December 21, 2007

GI7B Six Meter Amplifier Project - Update 4

Last evening I have completed the high voltage board as well as placing the high voltage transformer into the chassis. The high volatge PORCELAIN insulator and safety resistor (47 ohm 50W) are also in place.

Thursday, December 20, 2007

GI7B Six Meter Amplifier Project - Update 3

In the past couple of day, the six meter amplifier project moving very slow.

1) I have made the PCB Board Fabrication for High Voltage and Soft Start. This weekend, will go for the Software Key and Bias PCB.
2) I also drill two big holes for the front panel meter High Voltage and Plate Current meter. Although it is a tough work, which took me an hour to complete, it looks very nice.
3) I cut 80mm Telfon Rod of 20mm Diameter for the plate choke. SWG 22 wire expect arrive from UK within this week.
4) I bought one 12V 10A contact rating Omron relay from Apliu Street, which is for the T/R switching.

From the photo, you can see the soft start PCB mounted on the bottom of the chassis.

Sunday, December 9, 2007

GI7B Six Meter Amplifier Project - Update 2

If is quite difficult to get small diameter of copper tubing. It needs to buy at least a roll of several meter of quantity. So I give up this kind of material. Looking around and thinking of using surplus short length of hard line cable, center conductor is 5mm diameter. Wound 4 turn, inner diameter 40mm.
Doorknob capacitor is 1000pf 15KV purchased from Mainland China.

GI7B Six Meter Amplifier Project - Update 1

Yesterday went to Canton road to cut the aluminum sheets for the front panel and partition for the chassis. Six pieces cost of $215. I also locate one winding transformer company and ask for the quote for a 1000VA transformer at a reasonable cost. Size is approx. 6”x6”x6” and delivery time is one week. I told the shop will prepare the specification and order next week. What a surprise that they have transformer oil (for my HN-31 Heathkit dummy load) in stock, which is very rare and difficult to find here.

The major component is ready and has tried to place them on the chassis and it looks fine.

Friday, December 7, 2007

Amplifier Chassis

Yesterday purchased 20 ft - 1 inch aluminum angle, which cut into small section for building the chassis of the GI7B amplifier. It cost $95 dollars including the entire cutting fee. The chassis’s dimension will be at (360mm D x 350mm W x 200mm H). When have time this weekend, I will go to Canton Road to source aluminum plate for internal partition, front and rear panel.

Tuesday, December 4, 2007

GI7B Socket Arrived

The beautiful pair of GI7B socket arrived.

Monday, December 3, 2007

Dinner gathering on 1 Dec

Wyn, VR2AX offer me a pair of old GE 3-500z tubes. By this occasion, I arranged a dinner gathering together with Steve, VR2XMQ and Martin, VR2/AA1ON. My XYL and Queanne (Martin’s colleague) also with us. We all have a very enjoyable time.

On Sunday afternoon, I tested the tubes with the following result:

1) Standby current (60mA for two) 25mA + 35mA. My old pair of Eimac took 110mA on both

2) Output power

80M = 850W
40M = 850W
20M = close to 900W
15M = 850W
10M = 650W

One is growing red.

Thank you Wyn for this nice gift to me.

Saturday, December 1, 2007

ZL7/SP5EAQ - 40M QSO confirmed

I am very happy to confirm the QSO with ZL7/SP5EAQ on 40M. My antenna is a trap shorten dipole ( GM4JMU design ) with 100W from FT-2000.

GI7B Six Meter Amplifier Project

In year 2000, three of us ( VR2XMQ, VR2IL and me ) purchase a very nice Russian Tube (GI7B) from Dr. Alex UR4LL for the intention of building amplifier for six meters. We never start the project ...
Until early this year, VR2IL sold his tube to me. With the pair of tube, I start to plan the project, including:

1) collect of parts
  • For the reason that commercial tube socket is not available and searching around the net and find it is available from W4ZT
  • Power transformer, still searching around if it is available to wind in local market. Otherwise, may need to find in Mainland.

2) Circuit - I refer to use YU1Aw design.

I will update any more status of this project in future.