Concurso Nacional V-UHF

Today I’ve hiked up with my father to Siete Picos, SOTA summit EA1/SG-005 (2138m), to participate in this month’s national V-UHF contest. We arrived and set up around 07:30UTC and worked until 11:30UTC, where activity became low, as most possible contacts were already done and people started to leave in order to prepare lunch. The equipment was a Yaesu FT-817ND and an Arrow yagi antenna (3 elements in 144MHz and 7 elements in 432MHz).

Below is the map of stations worked. My position is in red, stations worked both in 144MHz and 432MHz are in green and stations worked only in 144MHz are in blue. The black station is the odd one that I could only work in 432MHz. This can happen if you catch them first in 432MHz, then a big mess with several stations arises and you’re unable to tell them to change to 144MHz to make the contact and decide that you’ll catch them in 144MHz later, but you don’t manage to find them later.

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Improving phase noise performance of the DF9NP 27MHz PLL

In some of the latest posts, I’ve being talking about the phase noise performance of 10GHz receivers, and in particular, of 27MHz references for Ku-band LNBFs (1, 2, 3, 4). Indeed, this started when I checked the performance of my new 10MHz GPSDO and 27MHz PLL by DF9NP and I wasn’t too happy with the phase noise.

After working with Dieter DF9NP in investigating this problem and performing several tests, Dieter found that the problem was likely in the loop bandwidth of the 27MHz PLL. The loop filter bandwidth is 50Hz. He proposed the following component modifications to change the bandwidth to 300Hz.

Modification of the PLL loop (new values in red)
Modification of the PLL loop filter (new values in red)

After I performed the modifications, I was quite surprised and happy with the results. As always, I’ve used the beacon of BADR-5 at 11966.2MHz to test the phase noise performance. Linrad’s AFC is in use. The result is below. As you can see, it is as good as the best references that I had tested before.

10MHz GPSDO and modified 27MHz PLL
10MHz GPSDO and modified 27MHz PLL

For comparison, this was the performance before the modification. The difference is huge. Many thanks to Dieter for his effort and to Luis EA5DOM, who also participated in the discussion and gave some good advice.

10MHz GPSDO and 27MHz PLL
10MHz GPSDO and 27MHz PLL

Update on phase noise of 27MHz references

This is a follow up to a previous post where I investigated the phase noise of 27MHz references to be used for a 10GHz receiver. Dieter DF9NP has being kind enough to send me a 10MHz 0.25ppm TCXO to do some more tests.

I’ve connected the 10MHz TCXO to the DF9NP 27MHz PLL and used it to receive the beacon of BADR-5, as I did in the previous post. The phase noise of the 10MHz TCXO + 27MHz PLL can be seen in the following figure.

10MHz 0.25ppm TCXO and 27MHz PLL
10MHz 0.25ppm TCXO and 27MHz PLL

For comparison, see below the phase noise with the DF9NP 10MHz GPSDO and 27MHz PLL. There is not much difference between both. This seems to indicate that the culprit of the phase noise is the 27MHz PLL, as the 10MHz TCXO should be quite clean.

10MHz GPSDO and 27MHz PLL
10MHz GPSDO and 27MHz PLL

Phase noise of a Baofeng UV-5R 10GHz signal

Several of the Baofeng chinese handheld radios generate a weak 10GHz signal while in receive mode. Thus, they are a popular cheap and quick 10GHz signal source for tests. To generate a 10GHz signal, you have to tune the Baofeng to the 70cm band (for instance, 432MHz). The radio will generate a weak 24th harmonic while in receive mode. If you want a steady carrier, you have to set the squelch to zero. Otherwise you will just get beeps as the radio wakes up periodically to check for a signal. Lately, I’ve being investigating phase noise and reciprocal mixing of 10GHz receiver systems. A natural question is how good is the phase noise of a Baofeng used as a 10GHz signal source and whether it can be used to check if the phase noise performance of a receiver is acceptable. It turns out that it is not so noisy as one may first think.

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Ship reflection on ED5YAE 10GHz beacon

In my previous post, I mentioned the possibility of receiving 10GHz beacons reflecting off ships in the Mediterranean sea through the Paella Team WebSDR, in Alicante. Luis EA5DOM tells me that these reflections happen often. However, I didn’t get any in the time I was doing the recordings for the previous post.

After making much longer recordings, I have seen a couple of reflections. I would say that a dozen or so happen every day. However, they last for quite long. Here you can see a reflection lasting for almost 20 minutes. The Doppler shift ranges between -300Hz and -200Hz. At its strongest moment, the reflection is only 10dB weaker than the beacon.

ED5YAE: direct signal and reflection
ED5YAE: direct signal and reflection

Phase noise of 27MHz references for a Ku-band LNBF

Today, I’ve being measuring the phase noise of the different 27MHz references that I have for my Ku-band LNBF. The LNBF is an Avenger PLL321S-2. I’ve modified it, removing the 27MHz crystal and including a connector for an external 27MHz reference signal. In my lab, I have the following equipment to generate a 27MHz signal:

  • OCXO/Si5351A kit. This kit includes a 27MHz OCXO and a Si5351A frequency synthesizer. The Si5351A can act as a buffer and output the OCXO signal directly or generate a 27MHz clock.
  • A DF9NP 27MHz PLL and a DF9NP GPSDO. The GPSDO generates a 10MHz signal which is locked to GPS. The PLL generates a 27MHz from the 10MHz signal.

I’ve used linrad to receive the beacon of BADR-5 at 11966.2MHz using different references for the 27MHz signal. The AFC in linrad tries to compensate for any drift in the reference or the satellite beacon. By averaging, one can get good plots of the sideband noise of the beacon. This is far from a proper lab test, but it gives a good idea of the performance of the references.

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Concurso Atlántico V-UHF

Today, I’ve participated in this month’s national V-UHF from Cerro de San Pedro, SOTA summit EA4/MD-020 (1425m). I arrived the summit a bit before 10:00UTC and worked until the end of the contest (14:00UTC). The equipment was the usual: a Yaesu FT-817ND and an Arrow satellite yagi antenna (3 elements in 144MHz and 7 elements in 432MHz).

Find below the map of stations worked. My location is in red, stations worked both in 144MHz and 432MHz are in green and stations worked only in 144MHz are in blue.

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Using the CC1101 and Beaglebone black for IP traffic on 70cm

Lately, I have been experimenting with using a CC1101 chip together with a Beaglebone black single board ARM computer to transmit IP traffic over the 70cm Amateur band. There has been a similar project from OEVSV, but I’ve never seen this project reach a final form. Edouard F4EXB has some code that uses the Raspberry Pi instead. Presumably, this will suffer from problems when using the higher data rates supported by the CC1101, as his software is not real-time.

The goal of my project is to build an affordable 70cm IP transceiver with a power of a few Watts. This can be used in the Hamnet Amateur Radio IP network. The modulation should not use more than a couple of hundreds of kHz’s of spectrum, as it doesn’t seem very sensible to take up much more spectrum in the 70cm band. Although the usual maximum bandwidth in the 70cm band is 20kHz, the IARU R1 bandplan allows for wideband experiments around 434.000MHz. A data rate of 128kbps with MSK modulation seems about right, as it uses roughly 200kHz of spectrum. Further on-the-air tests will perhaps change these parameters a bit.

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KISS, HDLC, AX.25 and friends

A while ago, I uploaded my gr-kiss out-of-tree GNUradio module to Github. This is a set of blocks to handle KISS, HDLC and AX.25, which are the protocols used in amateur packet radio. There are several other OOT modules that do similar things, but I didn’t like the functionality of them very much. While programming this module, I’ve also noted that the documentation for these protocols is not so good sometimes. Here I’ll give a brief description of the protocols and explain how everything works together.

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