30 March 2017

Challenges of the HB100 10 GHz module

As listed in the previous post, the HB100 10 GHz sensor module poses some challenges when repurposed as an RTX. Let's list them, and possible workarounds.

1) The RF power is in the order of 10 mW (10-12 dBm).
On 10 GHz it is easy to assemble and use a high gain antenna. Some people report that an IKEA lamp has the perfect shape. Just remember that higher gain means narrower beamwidth.

2) Frequency stability was not a design goal for the original destination of use.
Frequency instability can be tamed with proper thermal insulation of the module. The more the merrier. In any case all narrow band modes are out of question. WFM is the way to go.

3) Receiver is direct conversion.
This one, combined with #2, is a bit harder to tackle. You can't do CW or SSB. You can't do FSK. The solution proposed by a U.S. HAM is to work full-duplex. Transmitters are on different frequencies. The received signal is then at an Intermediate Frequency equal to TXQRG difference. If the difference is about 88-108 MHz, you know which WideFM receiver can be used! Actually an RTLSDR dongle receiver allows more frequency agility and flexibility, thus allowing to operate I.F. outside the crowded FMBC band.

There are other reports that HB100 is sensitive to microphonics (mechanical vibrations are picked up and turned into electrical/RF signals). Not hard to keep under control, either.

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