Some weeks ago I went to a small ham gathering at the site of a local repeater.
I had a talk with local hams about uplink equipment to the QO100 satellite. Many people are planning getting active on the satellite, so equipment for the 2400MHz band is in higher demand.
I had been planning to use some cheap Chinese modules for the local oscillator, but one suggested to find some better modules with Franco, alias RF-Microwaves.
Looking at the site I found that they have a lot of interesting stuff, especially in their surplus dept. Here are a few examples:
- A local oscillator module running at 2009MHz with the standard 8MHz crystal
- Some LNB modules without feed horn, but with input connectors
- PCBs with 4 HEMT FETs, where the PCB is arranged, so that it is possible to cut out two low noise amplifiers
- WLAN PCBs with several good components, including some 2.4GHz band pass filters
- 15GHz oscillator modules with several 10s of mW output.
I ordered a few of each, and some microwave absorbing foam. The service from Franco is excellent, I ordered one afternoon, and 2 days later, in the morning, the goods were delivered. The exception would if he is at a ham gathering, such as the Friedrichshafen Ham Meeting, probably the biggest in Europe.
Now for the goods, some of which are the last few left.
The 2GHz local oscillator module (about €20):
This is a complete module with casing and mounted with vibration absorption. Looks really good. On the website there is some modification information. The VCO can be used from about 1960 - 2040MHz, and the modification consists of making an external reference oscillator, replacing the internal 8MHz crystal oscillator. The external reference can be made with a well filtered DDS module.
For the IF of 432MHz the LO frequency should be 1968MHz, which is in the VCO range
As s second use of the LO module, it should be feasible to add a multiplier x5, for a local oscillator for a linear 10GHz transverter/converter.
A brief description of the LO module is on Franco's website.
LNB module (about €3):
This is a DRO controlled down converter module for satellite TV, with the mixer/oscillator in a single chip.
F6CXO has proposed the use of this module as a down converter for a (lower frequency) spectrum analyzer. The modification involves removing the 11/12GHz amplifiers and the filter. This cannot remove the image frequencies, so one needs to be aware of the frequencies that can be generated by the circuit you are testing. For amateur use, it does present a possibility to see what is going on in the 10GHz band, without having a more expensive spectrum analyzer. Mine covers up to 1.7GHz, so with a LO tuned to 11GHz the frequency range of 9.3 - 12.7GHz can be monitored.
Max RF input for the converter is about 0dBm (1mW). The RF input connector should be changed to a SMA, for the original ones it is probably very expensive or difficult to find a source for them.
The modification, if done carefully and with antistatic precautions, should provide you with 3 working GaasFETs, apart from the intended converter. I would probably make 2 converters, the second one using the lower LO frequency of about 9.7GHz, thus covering 8.0 - 12.7GHz with my analyzer.
A description of this modification is posted at Franco's website.
I would propose a few uses for the module, apart from sourcing components:
- Using the converter as it is, as a WBFM down converter to the 600 - 800MHz range.
- Adding a connector to the output of the 10/12GHz preamplifier (before or after the (modified) band pass filter, providing a simple 10GHz amplifier with a gain of 15 - 20dB, likely with 20-30mW output.
- It might be possible to add injection locking to one of the DROs, if so the converter could be used as a simple narrow band down converter for 10GHz.
- Using the LNB as it is, for rather unstable down converter for wideband FM.
- Using the casing (moulded aluminium?) as it is for other modules I should build
I am sure other uses, apart from being a source of components, will turn up ...
Not bad for a €3 module.
PCBs with 4 HEMT FET amplifiers:
There is a document on this PCB, too, on Franco's website.
Here are some uses the document suggests:
- A low noise 10GHz LNA from a cut-out piece of the PCB. Each PCB could provide two of those in a relatively easy way, also salvaging two HEMT FETs. Yes, the board has 4 amplifiers, it looks like it has come from a dual head LNB. A negative supply for the gate of the FETs is necessary to add to the simple amplifier.
- Using a piece of the 50ohm stripline as a piece of test equipment, e.g. a component tester or for a bias-tee. The PCB material is good for up to 20GHz.
- Making 1 12/24GHZ doubler.
- The FETs are useable on 24GHz with up to +13dBm output and a gain of about 7dB.
This looks like an excellent source for building microwave stuff.
Like with the "connector-LNB", you get a lot for €3.
The WLAN PCB looks like a good source of components for building some 2.4GHz transverters/converters.
I was buying them, mostly for the 2.4GHz filters, but there is a PLL IC, a prescaler, and other good components there.
The last one, the LO PCB:
This contains two LO chains for around 14/15GHz:
- A straightforward receiver LO, starting on around 2.5GHz, adding multipliers. A tripler for 7.5GHz and a doubler for 15GHz
- A TX LO which also includes a modulator, meaning that it looks useable as a (WB)FM modulated transmitter, with a suitable PLL oscillator modification of the 2.5GHz part.
The output transistors, (two) coupled with a hybrid, are supposed to be capable of delivering about 100mW on 14GHz. I am now wondering if the hybrid is broadbanded enough to cover 10GHz, but that is something that needs to be tested. Also the 14/15GHz filters should probably be bypassed and replaced with some 5 and 10GHz filtering. I am hoping to be able to use a modified version of this PCB as a 10GHz power amplifier with 100mW output, if the hybrids have sufficient bandwidth. It may, however be necessary to design a separate PCB or set of PCBs, using the output FETs. With that, I will have to ask someone with **much** more experience than I have. I know, my general knowledge will probably not be sufficient for such a design ... yet.
- Also, an excellent source of components, FETs, MMICs etc.
Oh, well, so many ideas to try out, and lots of other activities. It will take time, and learning some new skills, but, as a start, I have a few of those modules
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