Category Archives: IC-705

QRPp on an IC-705

I have been wanting to work QRPp for while after reading about contacts CW ops were making on 80mW. The idea was to make a simple crystal controlled transmitter and use the 705 as the receiver. Than I read about the MFJ-813  which is advertised as a 5W QRP watt meter. Yesterday one arrived and has just been tested.

The 813 is reasonably accurate for such a low-cost meter. Starting with the 705 I set the power to 5W the meter showed 5W. Then I turned down the power to 5% and the 813 meter reading was remarkably close to 500mW. Turning down to 1% output on the 705 the meter read 100mW.

Next are some on air tests with 100mW – 1W power levels.

 

 

 

Auto antenna tuner kit

There are many different versions of an automatic antenna tuner on ebay and other sites. Some come with a case while others are supplied as a PCB and a bag of parts. There are few instructions around but there are circuits diagrams, or schematics, on some sites.

The board as received

The insulated rear panel

I ordered what I thought was a complete PCB with case but what arrived was a populated board without a case. I complained that it was different to the photo for the item and accepted a partial refund which amounted  nearly what I paid. I then ordered the case for under £13 post-paid.

The board came with SMA sockets already attached which meant it would not fit in the case, so they were removed. Assembly was a bit fiddley, but all seemed to go well. The first power up showed the screen was working. Next came an RF test which did not work. Some quick tests showed that the rear panel had no earth connections to the PL259 sockets!

I decided to make a new panel from aluminium. After reassembling the case and testing with a TX connected to my long wire antenna  everything worked as it should.

I now have an fully automatic ATU that senses when there is a band change and retunes.

The new aluminium panel ready for testing

IC-705 and a new portable antenna

Although I still make stuff it is getting harder especially with small components. Last year I was told that I have rare form of cataracts. That makes working on circuits boards difficult. When the current pandemic is over maybe they will be able to replace to duff components and restore the circuit to its original condition.

This is all leading up the to be the excuse for buying an IC-705! It’s an exceptional radio with amazing performance which is hard to believe for an old timer brought up on HF receivers that occupied a full 19 inch rack.

 

Above left – Marconi HR11 telegraphy receivers with the boss pretending to tune one and above right, Plessey PVR800s telephony receivers. The first transistorised professional RX for the HF point-to-point service. Pics from around 1968 at PO radio station Bearley.

The IC-705 which I can hold in one hand!

So now the work is on perfecting the HF /P antenna. I have gone back to an end fed half wave made from a homebrew system that breaks down into 1m long sections. The aim is to cover 40m-10m with different lengths of wire wound on a reel, after removing the washing line. See Steve Nichols, G0KYA,  post on his blog here.

I also have a couple of light weight fibreglass poles and a drive over support just to make everything more flexible. That will allow me to operate from the car/micro camper.