Sunday, April 28, 2013

New coil for the antenna tuner

It was a "profitable" Saturday yesterday, build the new coil for the (re)new antenna tuner:

I had this form with some kind of steel wire wrapped around and since it was not solder-able I removed the old one and now placed normal 1.5mm2 section household wire. Unfortunately I had no more wire around so it was not till the end of the form, anyhow I suspect the inductance will be more than enough for the intended purpose. Don't "trust" the MFJ reading at the measure frequency frequency since there's lot of inter winding capacitance. My rough calculation for the coil will be around 50uH.

Here's the donator coil wire (the old one):

Had to strip the insulator which is always a pain...
...and still had time to make an oscillator just for fun...

And to place the AM demod part for the Speaky in a new board, pictures and schematic later on the blog.

Have a nice Sunday!

Thursday, April 18, 2013

Happy Birthday IARU


IARU Birthday: (18 April 1925)

Happy birthday!

Filter shape

Just the filter shape from an ongoing project...

Scale is not linear and I don't like the re-trace so probably will change schematics a little. Will post more when happy with design.

Monday, April 15, 2013

SAW generator

Not much RF here, except it's part of a project involving RF.

A simple SAWtooth wave generator:

Schematic is from VK2ZAY and the current source my contribution. Incidentally I didn't tested the original design so don't know which is better...probably not mine!

(VK2ZAY schematic edited by me)

Now the output of the schematic:

Wave form with an 10uF capacitor:
...there goes the linearity... oh well...

here with 4.7uF capacitor and final configuration for now:

DC out is 2 to 7V approx (Vcc 9V).

The last wave feeding the oscilloscope horizontal circuit

Here the assembly:

Alan has other designs using discrete components I might test.

Have a nice week!

Thursday, April 11, 2013

Speaky AM

Not rocket science here. Just "grabbed" the 8Mhz pre-filtered and buffered output add-on of the Speaky and made a simple 8Mhz AM "receiver" with an IF of 455Khz. Mixer VFO runs at 8.455 since at 7.545 would put if receiving on the 40m (7.090Mhz) band also.

It's just a simple tuned input for an NE602 mixed with 8.455Mhz going thru an 455Khz filter feeding the AM demodulator part of an TCA440, then audio goes to the famous LM386.
Since it's a ongoing experiment will not place schematic for now, but works nice on this simple setup....I can still copy clearly some SSB transmissions, so I'm sure there's little carrier suppression on some rigs...

The main PCB and the TCA440 part were a re-use of one of my VHF air band receivers...another project that had a short live before donating parts...

Have a nice week and weekend!

Monday, April 01, 2013

New bands

While some people over here were applying for access on the 5Mhz band, our telecoms regulator "ANACOM" on a bold move just gave us access to another 8 bands in the HF spectrum.

I think this is a shift from the classic deny first, allow latter paradigm that is so classic across all sectors of society.

The new bands in Portugal are as follow:

455 Khz
600 Khz
4 Mhz
8.865 Mhz
9 Mhz
10.7 Mhz
21.4 Mhz

All modes are allowed. This is of course on a non interference basis, hams are primary users.
Beacons are welcome using low bandwidth modes.

Frequency shift is allowed to a maximum of 15Khz deviation

Output power is not regulated yet but probably will be around a maximum of 17dbm to keep things even with the other allowed bands.

Let's hope this new bands get adopted all over the world!