PJ4MM on 40MHz Again Today.

 Another good day for the 40MHz band.

One more time PJ4MM was coming through with up to 0dB S/N. 

It will be interesting to see how the 8m band monitoring will turn out this spring.

Monitor on 8m (40.680MHz)?

 I made my first test, listening on 40MHz. There is some experimental work going on on  40.680MHz with weak signal modes.

A local station with indoor antenna reported decoding PJ4MM, so I started testing

So I had my IC-703 connected to the 10m half wave antenna, and set the frequency. Pulse noise up to around S7. The noise blanker (NB) of the 703 seemed to make little difference. I tried to get the NB setting, and set it to the highest level. That reduced the noise, even if it is still not good. No S-meter reading.

Then PJ4MM came up on screen, starting with a S/N of -20dB, and for about 20minutes of the signal was there. Best S/N has been -7dB until now.

Not a bad beginning, given the severe pulse noise. DX heard on 8m.

Right now I am not going noise hunting, it is still winter time, and I have a cold, or the flu. In the spring I may try, and along with that, maybe try to make some phasing out of that noise. After all, it's only a single "channel" I need to cover. 

10GHz Transverter, Continued.

 In the autumn/fall last year I was out making a receive test of a 10GHz transverter briefly described a few days ago in the previous post. 

When I should have had a signal from the OZ7IGY beacon about 25km away, there was ... nothing.

I started the fault finding with a measurement of the LO module, and it did look pretty good. So Now the down converter should be tested.

I located a signal generator (low cost Chinese circuit with the ADF 5351 synthesizer. As the signal generator has a fixed output, I made a small loop for 10GHz, soldered to a low cost (chassis) SMA connector. Measure on the spectrum analyzer (with built-in frequency counter the signal generator seemed to stay within a few 100 Hz, with a fixed offset of about 10kHz. Good enough for a first test.

Power up the transverter with 12.5V, the IF connected to a Malahit DSP2 SDR set to 144MHz, and let the system warm up a bit. The 12.5V was about what the battery delivered at the test. 
It sounded absolutely dirty, with some irregular jumps in frequency.

Where was the instability? I tried connecting the FT-290 and it was the same. Apparently I could eliminat the possibilty of the Malahit going faulty. Now remains the LO of the transverter or the signal generator.

Next test was, let us see what happens if the supply voltage is increased.

Bingo. at 13.5V the LO apparently jumped to the correct frequency (well, about 3kHz low) and stayed there, the tone sounds good, all the dirt gone from the audio, and the sensitivity looked much better. You may laugh, I don't mind, because I foind the fault.

Connecting back to the Malahit SDR, and it looked good.

The Chinese signal generator, though has a rather noise output. Good enough to test the system, but the phase noise is atrocious, only about 10-20dB below the carrier. I heard that a ham not too far away has made some modifications, and I will look into that.

So what to do when I do go out into the field? I need 13.5V and the battery delivers only 12.5V. Too low for a good function.

I think I will try first with a different battery and a DC/DC converter. I know that the DC needs extra filtering, but it should be usable for the first field tests. Next step: check the TX function.

Fault Finding in an Old 10GHz Transverter.

In the autumn I made a first test of a home-made 10GHz transverter I got my hands on, and started testing.

The initial test was a simple connection to an older FT-290 transceiver, and going out to spme place a bit higher than where my house is located.

I was listening for the beacon OZ7IGY at a distance of about 25km. Nothing in the garden. If I placed an satellite TV LNB about 4m above ground I could hear the beacon, very weak, because it is behind some hills about 30m higher than where I am.

I tried to go to a place somewhat higher with the FT-290/transverter setup on a tripod, and tested. Absolutely nothing heard. tuning about 30kHz to either side of the beacon frequency.

So now I got started fault finding.

The first suspicion after talking to a local ham was the 2556MHz local oscillator module. Testing on a spectrum analyzer showed a nice signal with an offset of less than 600Hz. Not bad, this would give an offset of less than 3kHz. The output (to the Qualcomm up/down conversion module) is close to 5dBm, so that looks quite good. I can safely say that the LO module works nicely.

Now more tests are necessary.

 I do need a small 10GHz signal source, and I have thought of using one of the following:

- a low power (0.5W) 70cm FM transceiver with an attenuator and a single diode as multiplier

- a synthesizer PCB with a AD 4350 or 4351 chip, just using the 3rd harmonic. 

At least I can test those with the spectrum analyzer, so I know if there is a strong enough 10GHz signal.

I think the simplest of the two is the attenuator/diode multiplier, so I think I should start there.

A Bit of New Stuff, Arrived From China in December and January.

 I have ordered a few things from Ali Express recently, Some of this arrived in December last year, and this year until now.

Some of it still needs to be tested, but here are a few things that may be of interest.

Some time ago I got a collection of used 18650 Lithium Ion cells, so now I got myself a capacity tester. This needs to be tested.

I am slowly starting doing some experiments on the microwave bands, so I got myself a log-periodic antenna covering 800MHz - 6GHz, covering the amateur bands 1296, 2400,3400 and 5760MHz. Intended use is mainly for antenna testing, but it can also be used to feed a parabolic dish.

I am beginning to dismantle some older electronic equipment for (some) parts, so I got myself a desolder station.

A couple of LNAs claimed to cover 10MHz to 6GHz. Should be tested.

A Malahit SDR receiver, self contained with LCD screen and built-in speaker. A quick test shows an OK receiver. Nothing spectacular, officially covering 10kHz - 380MHz and 404 - 2000MHz, with spectrum display (max. 192kHz wide) Nice little receiver, can be useful for many tests, especially with portable equipment, but also converters and transverters (receive part only).

There is more, but those are the more interesting things for me.

Monitoring on 10m. Updated.

I got  a bit of space on the lab desk by now. Still much more tidying needed.

For now, part of my monitoring system for 10m consists of a half wave antenna, connected to my modified IC-703 with a loop-back for the receiver signal.

The receive signal is running through a power splitter, so part og the signal goes back to the receiver section of the '703 and two outputs go to other receivers. Two is not quite enough, as I want to monitor several frequencies around the 10m band. Some amplified power splitter is needed.

The frequencies I want to monitor on 10m are, at least:

- 28.200 (International Beacon Project) (with audio)

- 28.074 (FT8 frequency)

- 29.600 (FM calling frequency)

- 27.555 (Used by CBers as a calling frequency. Excellent propagation indicator for 10m)

- 28.126??? (WSPR and QRSS frequencies)

I have a couple of "transistor radio" portable receivers with a jack connector as external antenna connectors, so I made two cables with F-connector to jack plug. They should be used for the 27.555 receiver (up and running), and FT8 monitor receiver. I still need to set up a computer with sound card input for that purpose. 

I have a monitor system like that running on 50MHz, and I would like to continue using that. Possibly a Raspberry Pi set-up.

Last year was a bit low on radio activities. I should have had a better antenna system up, but other, more urgent activities came in the way. The solar power system also needs an update. This should be a busy year. 4m and 6m antennas have priority, as the bands are good due to high solar activity. Some activity on microwave bands should be made, too, and I should finally get up a rotator, so I can rotate a small VHF/UHF/SHF antenna system. We shall see how much gets done this year.

Update:

It looks like the Sangean receiver is not suitable for FT8. (noisy local oscillator?), or not sufficiently sensitive so I will have to use another radio for that purpose, or build one myself. Still looking around.