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.
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.
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.
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.
I have being receiving several 10GHz on different WebSDRs with linrad to get a rough idea of the performance of the beacons and receivers, both in terms of frequency stability and phase noise. Here are the results.
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.
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.