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.
Tag: microwaves
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.
Several 10GHz beacons on WebSDRs
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.
Hailstorm in 12GHz
Yesterday, there was a big hailstorm in my town. During the storm, I rushed to the radio shack to see if this produced any effects in my Ku-band satellite receiver. This is a 95cm dish pointing to the 26ºE geostationary orbital position, and it will be used to receive Es’hail-2 in the future. In the image below, you can see that the difference is huge.
In the waterfall, you can see several beacons from broadcast satellites. It is clear that during the hailstorm the noise floor was much higher. In fact, 2.5dB higher. This is probably caused by scattering of DVB-S signals from satellites in other orbital positions, scattering of thermal ground noise, or a combination of both. Also, although it is not easy to see in the waterfall, the beacons of the satellites where weaker during the hailstorm. For instance, the beacon of BADR-5 was 0.9dB weaker, due to the increased attenuation caused by hail.
These differences may not seem large, but in fact they are. I have a cheap DVB-S2 decoder connected to the system. It usually receives fine several channels from the BADR satellites (on some other channels, the signal is not good enough, apparently). However, during the hailstorm, this receiver couldn’t even get a lock on the DVB signal.
Receiving Ku-band geostationary satellite beacons
After sorting out some problems with several connectors which caused huge phase noise in the external 27MHz reference, I have my 10GHz receiver up and running as it should. This station will be used to receive Es’hail-2 in the future. The station is composed of a 95cm offset dish, an Avenger PLL321S-2 Ku-band LNBF modified to use an external 27MHz reference, an OCXO/Si5351A kit used as the 27MHz reference, an RTL-SDR, and a cheap DVB-S2 receiver as a power supply (this allows me to change polarizations and LO frequency easily).
The dish is pointing to the 26ºE or 25.5ºE orbital position, where Es’hail-2 will be. Actually, I have pointed the dish to peak the beacon from BADR-5 the best I can. To test the performance of the station, I have tried to receive the beacons from several Ku-band satellites. Here are the results.
Scanning Ku band satellites with the FUNCube Dongle
I’ve recently installed my satellite dish and modified LNBF in my garden. This equipment will be used to receive Es’hail 2, the first geostationary satellite carrying an amateur radio transponder. Here I’ll look at the hardware I’m using, how I did the alignment to the 25.5ºE geostationary orbital position where Es’hail 2 will be located, and how to have some fun scanning the direct broadcast satellites in the Ku band with a FUNCube Dongle Pro+.
Building the GALI-39 amplifier kit from Minikits
The GALI-39 is a DC-7GHz MMIC amplifier from Minicircuits. This device has a gain around 20dB and a NF of about 2.4dB. The nice thing about MMICs is that their input and output impedances are matched to 50Ω, so it’s quite easy to work with them. Minicircuits makes many MMIC amplifiers suiting different needs, but unfortunately their products are not so easy to get in small quantities.
Minikits.com.au is an Australian store that sells Minicircuits parts in small quantities as well as many interesting RF kits. I needed some RF amplifier having a known NF to do some signal level calibrations, so I ended up ordering the GALI-39 amplifier kit from Minikits. This kit includes just the GALI-39, a PCB and the handful of SMD components you need to bias the amplifier. At 22AUD, the price of the kit is about right and buying the kit instead of just the GALI-39 saves me to do the shopping for the assorted SMD components and using the PCB instead of botching some circuit is always nice, because the PCB uses microstrip transmission line (but the substrate is regular FR-4). Here I have a look at what is included in the kit (I’ve been unable to find a complete list on Minikit’s web).
An idea for a low cost stable 10GHz receiver
The satellite Es’Hail-2 is expected to be launched by the end of 2016. This will be the first geostationary satellite carrying an amateur radio transponder. As the launch date comes nearer, it becomes interesting to find a low cost solution to receive its 10GHz downlink.
Several amateurs have been experimenting with low cost LNBFs designed to receive satellite TV. These operate in the Ku band and usually cover the frequencies 10.7GHz-12.75GHz. However, many of these LNBFs have also good performance in the X band, and particularly in the amateur 10GHz band (10GHz-10.5GHz). In fact, the ASTRA-type LNBFs have a local oscillator which can be setted to either 9.75GHz or 10.6GHz. The 9.75GHz local oscillator mixes 10.386GHz (the narrowband terrestrial subband) to 618MHz, which is a frequency covered by most SDRs and conventional scanners. The satellite subband, which is 10.45GHz-10.5GHz gets mixed down to 700MHz-750MHz, a frequency which is also easy to deal with.
Building the G0MRF comb generator
A comb generator is essentially an RF oscillator whose output is amplified in a non-linear fashion, so that plenty of harmonics are produced. This is an easy way of producing microwave signals. The G0MRF comb generator was originally designed as a 2.4GHz signal source, to help in the alignment of receivers for the amateur radio satellite S-band. It has a 96.013MHz crystal oscillator, so its 25th harmonic falls at 2400.325MHz, right in the satellite allocation of the 13cm amateur band. Its harmonics are usable up to at least 10GHz, so this can be an useful tool when working with microwave equipment.
In fact, several other harmonics fall on the amateur bands: The 13th harmonic is 1248.169MHz. This is inside the 23cm amateur band, but quite far from the narrow-band segment, which is at 1296MHz. The 24th harmonic is 2304.312MHz. This falls inside the 13cm band. Indeed, 2302MHz is used for EME in some parts of the world. The 36th harmonic is 3456.468MHz, in the 9cm band, but far from the narrow-band segment. The 59th harmonic is 5664.767MHz, in the 6cm band. This is in the satellite uplink segment and quite near the first narrow-band segment, which is at 5668MHz. The 60th harmonic is 5760.780MHz, right in the second narrow-band segment of the 6cm band. The 105th-109th harmonics all fall in the 3cm band. In particular, the 108th harmonic is 10369.404MHz, which is in the narrow-band segment of the 3cm band.
This is a nice kit which is quite easy to build. Most of the components are through-hole, and it can be put together fairly quickly. I built my kit during the Christmas holidays, but I’ve had the PCB lying around until I installed it in a project box yesterday. Here I describe the kit briefly and show the extruded aluminium case I’ve used.