160m - 80m Experimental Loop

Yet another receive loop is born.

The construction is similar to the first 500 kHz loop, i.e. cardboard box loop, but made with Litz wire and with only 6 turns.

The calculation of resonance frequency found here indicates a frequency range covering the whole of the 160m and 80m band, and this looks like what I have.

The coupling is made with a further full loop, and it looks like that creates a too hard coupling to the antenna (not really unexpected), making the antenna rather broadband.

Later this week some experimentation on the coupling loop size is in the planning.

Non ? Active loop antennas

I found some Chinese "active loop antennas" on eBay the other day, the price
was reasonable at $25, so I decided that it was worth the risk trying it out.

Since it had the brand name "Degen" (type "31MS" - guess that would mean MW and SW) Joachim and I joked about it being a "degenerative" antenna.

I picked the antenna up at the post office today, and gave it a brief try, and it looks like it lives up to its name and that the joke was not really a joke at all.

The first thing that happened was that a suction cup for mounting the antenna on a window would not stick to any window at all, poor manufacture quality, even for a Chinese product. It did not bode well.

On MW the S/N is lower on the Degen than on the built-in ferrite antenna. on a part of shortwave it looks like it has some minor gain on frequencies in the 5 - 15 MHz range, but its effectiveness was not easily detectable.

I may have to try it during daytime, but I am not optimistic.

If you see it for sale, it does NOT have my recommendation. I may be able to use parts of it for experiments, but I doubt it will do much for me.

In any case I intend to take it apart and see how they managed to do so little.

Conclusion : Cheap antenna with cheap performance.

FAIL.

80m SDR, p2

More solder smoke released, only missing the ICs and the oscillator - I am going to leave out the oscillator and make a local oscillator input, making a switchable Local oscillator possible.

Now for some more reading.

Building SDR for 80m

Today I received the kit from the magazine "Funkamateur" with all necessary parts to build a "single frequency SDR", similar to the SoftRock, along with a few other components for my constructions.

Like for Joachim, one resistor had a 1000 times larger value than the one needed. No problem, since I had one of the correct value.

Some solder smoke generated, not quite finished yet, but it is time for some reading.

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 ;)

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.

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.