Tuesday, 31 July 2007


Once again ive had the lid of the ATU. I did so a couple of days ago when my curiosity got the better of me and i decided to take a look inside, and im glad i did. The connection from the capacitors to the inductor was dry joint and loose, and the inductor itself was slightly deformed. I resoldered the joint and repositioned and straightened the inductor.

Today, whilst messing trying to calibrate the antenna, i decided to switch to the dummy load and check the rig in straight through 50 ohm unbalanced load. Hmmm, SWR 1.1:1? should be perfect? wait a minute! 30W? im running 10W?!

so, out came the bird meter and the 25W load. Ive only got a 25-1000MHz element for the bird, so set the alinco on 24.990 and low power - perfect 10W, so, the old MFJ is out of cal.

Ive now calibrated the low power (30W range) of the ATU both forward and reversed in bypass mode to the dummy load at 10W. Ive also calibrated the high power (300W) forward reading, this being done on 3.8MHz at 100W to aerial, as ive no suitable load for this power, and the antenna can tune a 1:1 SWR on 80m.

It just shows, its worth taking the time to check 2nd hand gear carefully! The antenna is still no better, but at least any readings i take from the MFJs SWR bridge are meaningfull now.

Antenna Work

The coax originally connecting the antenna (in its G5RV form) was removed long ago in favour of all balanced line. But, this unfortunatly puts the feeder/element combined lengths at a rather unfortunate multiple of 1/4wavelengths for my main bands, and so getting the thing to tune up well isnt easy, and on 40m the low SWR point is very sharp. Im going to add another 13ft of feed to hopefully bring the length away from the current wavelenth multiples that are creating the high impedance problems. The new feedline arrived today, and so hopefully i can get it patched in soon. Ive also constructed a coaxial balun that i will try in place of the ATUs internal toroid, which i dont have great faith in.

Sunday, 22 July 2007


ok, so the shack in the bedroom was to be moved, as can be seen it was pretty cramped
so the sunroom cupboards came out, and it moved in there, after re-using as much material as i could, the result is a custom shack, neatly built in one corner.
top shelf - RX-2cc weather satellite APT receiver; MVT-7100 scanner; 2m 30W linear; Ft-290mk1; vase of artificial flowers.

main shelf/desk - FRG-100; DX-70TH; ATU; phone. Logbook and a pair of coasters. Underneath - dustbin; boxfile of manuals; cables etc; 30A PSU (not visible cos on floor)