Contents :

A collection of thoughts, and my notes about experiments and ideas, technical or otherwise, connected to Amateur Radio, Satellite working and monitoring and other electronics.

Sunday, May 31, 2009

Back to some radio stuff

I have been away for about a week and I am back from the holidays. My spare FT-817is now here and will be set up for WSPR/QRSS and other experiments, while soldering.

I know there is some stuff waiting for me, eg. a "single frequency oscillator" SDR kit like the softrock design, that I will solder as soon as it is here.

I do have quite a bit to read in the next month, so the radio activity will be somewhat limited. I will have to solder a bit between th words ;)

Tuesday, May 19, 2009

FT-817 PA failure

Looks like the PA of my FT-817 gave up the ghost. Maximum 50 - 100mW out of the transceiver, whatever I do.

It looked for a day or two like my WSPR signals on 10MHz were soewhat down, and quite right, minimalist output there.

I have decided to leave it as is for now, a bit of output is still there, but a repair has to be done at a later stage.

Also, I decided to move the FT-817 *as it is now, on 10 meters, so listening and *really* WSPRing on 28.126120 MHz if anyone pops up there I will be leaving the reporter on and with an estimated output power of 50mW, running concurrently with SpectrumLab for QRSS on 28.125900 - 28.126000 MHz, running with a full wave 10m loop inside my balcony, tuneable from 10 - 20m with reasonable efficiency.

Sunday, May 17, 2009

First test 10 MHz RX

looks like the AF amplifier is fine now, using abt 3 mA at 12V, Xtal oscillator uses abt 5 mA at 5V. Quite a bit lower power than the FT-817.

Having only one power supply in the shack for experimantation, I need to find a 78(L)05 in my pile of components, so I can test the XO and mixer. I wonder if the output of the XO is sufficient to drive the relatively low impedance (abt 2kohm) of the mixer. but guess it will.

No more soldersmoke for today. maybe a bit of reading for now.

WSPRing away

As an intermediate solution I have set up my FT-817 for running WSPR on 10.140MHz - with 200mW out. The receiver does QRSS reception, too, but of course blacks out while WSPR is transmitted.

I made myself an interface similar to the VK2ZAY one, and it works nicely. The AF level out of the computer is a bit low for operation of the "VOX" circuit, and should be modified a bit, but otherwise it works fine.

Now, it is a bit of overkill to use the FT-817 for just 200Hz of the spectrum, after all it covers all bands from 160m to 70cm. So the 10MHz direct conversion receiver of the previous post is just the beginning, a "proof of the concept", used for WSPR transmission and reception and QRSS reception

The intention is to build, at a later stage, a full, but simple, "single frequency ssb direct conversion transceiver" and a dedicated 30m antenna tuned to 10.140 - probably a "magnetic loop".

For now I have a fairly large reading project, so the ful TRX will have to wait a bit.

10MHz qrss rx

I left the 10m TX for a while and got started building a simple 30m direct conversion QRSS reveiver.

Discussions with Joachim resulted in two receivers one already built by Joachim and the one I am building now, with a local oscillator at half the RX frequency and using a RA3AAE type mixer

For this RX I am generally following this concept found at PA2OHH, the difference is that I - like Joachim - use a canned oscillator at 5.0688 MHz

The Oscillator/mixer and the AF circuit is ready for an initial test (tomorrow), and the RF input circuit is yet missing.

Tuesday, May 12, 2009

QRSS transmitter under construction

In talks with Joachim, PA1GSJ we decided to build the simplest possible (construction wise) transmitter for 28MHz.

Using a "canned" - in my case IC-like housing - oscillator on 28.322 MHz and a 74HC(T)240 as the "power amplifier" it is possible to get an output of around 50 mW, sufficient for a QRSS MEPT.

Joachim already has his model working, and I am in the process of building mine. The oscillator is there (duh)and the "PA" is just about wired, now I need to make the keyer , will be using a PICAXE processor, and the output matching circuit/low pass filter.

Monday, May 11, 2009

PA9QV on Ham radio

This will deal with my Amateur (HAM) Radio activities, newly started with a bit of QRSS and WSPR activities, more later.