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13cm Equipment

What started me off was an old Minikits 2.4Ghz receive converter kit, half built and sitting neglected on a shelf.  I’d struggled to get the oscillator chain to work, but then with nothing more than a digital VOM I could hardly expect to.  Over a couple of VHF/UHF Field Days I’d slowly added additonal bands, starting with 6, 2m  and 70cm then adding 23cm with a DEMI 25W transverter and 40el loop yagi.  The thought of getting active on 13cm (most activity is centered on 2403Mhz here in VK) was appealing, I had the basics of a transverter, so with renewed enthusiasm I dived into a new project. It was indeed a learning experience.

I’ve since reallocated the JWM PLO to a new 9cm transverter I’m working on, in it’s place I’m using a PLO sourced off ebay.com via an Israeli manufacturer.  These were going at one stage for US$45, but can now only be ordered in minimum quantities of ten. They are a one time programmed module where you specify at order time the frequency required. Specs:

+8dBm out, -90dBc/Hz @ 10kHz

I found the onboard 10Mhz oscillator far too inaccurate (40kHz off with one unit) and requested they deliver this module without the ref oscillator, I then use an external ovenised 10Mhz reference for very good frequency accuracy and stability. It’s likely the phase noise may also improve but I’ve not measured that.

The transverter I’m currently using is based around the Minikits 2400Mhz transverter module, brass plate box in centre.  Above that is a DEMI LNA, beneath that a 2403Mhz interdigital filter based on the idea from Jim W6PQL using standard size diecast boxes. To the right is a 10W PA (finned heatsink) and bottom right the 1W driver, both stages were surplus Comwave MDS equipment. For the rats nest it is, it works quite well, and it proved to me that this microwave stuff was do-able.

The oscillator is missing for this photo, things are in constant change around my workshop.  I had used a JWM PLO (1152 PLO model, now obsolete) on 1129Mhz that fed the doubler (slim brass box left of the transverter module) to deliver 2258Mhz LO injection for a 145Mhz IF.

This transverter is all about to change, my intention is to use a building block approach with high quality mixers and filters to make it simpler and smaller in size and far more versatile.