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Friday, 28 June 2019

13GHz Sig Gen - you can't be serious?


You may recall back here when I became very inspired by a project by GM8BJF using some eBay sourced Chinese modules to create an ADF4351 based signal generator.

There's another variation on that theme that has been published in the May 2019 Scatterpoint. Scatterpoint is the journal of the UK Microwave group, membership is about 3 bob and a conker so you have no excuses for not joining.

This time it uses an ADF5355 to generate signals from 52MHz all the way up to 13.6GHz.

The 4.4GHz generator has proved extremely useful, this one is a must.

I've modified the design and the software a little so that the 100MHz clock is generated by am ADF4351, rather than an OCXO as per Brian's design.

Brian has made the software available here, and my modified version is here. The AD4351 is a version of the evaluation board from SV1AFN - and it gets its reference from my 10MHz shack frequency reference.

The software runs on a SAMD21 ARM Cortex M0 which runs at a 48 MHz clock rate. This is supported by the Arduino IDE but is not something I had used before.

Its still WIP, but the project is up and running OK.

How cool is this?

Here's Miss Maggie Cat and Miss Pepper Cat doing what they do best:

Saturday, 8 June 2019

More Sequencing Secrets


I've been making another sequencer with a bias-t included; it builds on the stuff I did back here. This time I ordered some kits from the very excellent W6PQL.

The basic schematic for the sequencer is this:

Here's the build:

You can see the sequencer, a FET switch (which is used to turn off the power to the Bias-T during TX) plus the bias-T itself.

The bias-T is the sequencer event 1, events 2, 3 and 4 are ground on TX and available on the back panel as RCA sockets.

I've added some LEDs to the front panel to show the events switching and also a control to adjust the delay timing of the sequencing. The case is recycled from an old project:

I plan to use this to control the Transverter(s) and other gubbins I mentioned related to EME last time at the bottom of the post.

Local conditions.

Sunday, 2 June 2019

IC-9100 or the new fangled IC-9700?


I've been using a Icom IC-9100 as by base station 2M/70cm and 23cm rig for a number of years. The radio cost a small fortune but now, due to the release of the IC-9700, is worth about 3 bob and a conker.

My friend at LAMCO has lent me a IC-9700 (their shop demo model) to play with so I thought I would document my findings.

The IC-9700 is a modern rig, a "twin" if you like to the IC-7300 - the later has proved an extremely low cost SDR radio which has sold extremely well.

So here are the things I see as an advantage over the IC-9100:
  • Modern SDR architecture on 2M and 70cm
  • Accurate power out setting (on the IC-9100 you turn the knob and put it about where you want it - the IC-9700 has a %age power setting display)
  • Accurate CW pitch setting - as with the power out on the IC-9100 you have to turn the knob until it sounds about right. or alternatively you can use a CAT command but that's a bit bonkers too.
  • lower noise floor on 23cm - listening to the Martelsham beacon on 23cm I am sure the noise floor is lower on the 9700 than the 9100 - I may have just made that up though as I cant have them both running at the same time.
  • The SWR meter on the 9100 is a load of Dingo's Kidneys on the VHF/UHF/SHF bands, it seems to work on the 9700.
  • Accurate ALC - the AC meter on the 9100 on 23cm is inaccurate but the 9700 seems to work OK.
  • Bandscope/Waterfall - hadn't been invented when the 9100 was made.
And here are the things I already dislike:
  • It drifts! When you TX and the PA fan kicks in the TCXO clearly drifts - that's bad, and I mean that's really bad. I have measured 5-6Hz drift on 23cm.
  • There is no RCA PTT or ALC jacks on the back for linear amplifier interfacing - you have to use the 8 pin din ACC socket - which in itself is OK but I want to connect my MicroKeyer to that socket so I can have multiple CAT ports and other gubbins. Seems quite an oversight.

So, in conclusion the lack of RCA jacks is annoying; but the drift is unforgivable. I will need to make an adapter so I can connect both the MicroKeyer and the linear to the same socket at the same time - some diodes might be needed as the MicroKeyer will use the PTT (ACC pin 3) as an INPUT to the rig and my amplifier wants to use it as an OUTPUT from the rig. According to the manual it's both.

Just for the record, I'm planning to have a bonkers bash at EME on 23cm; I will be using the transverter from here to go from 28MHz IF to 144MHz, then have a remote 23cm transverter.

The TS-890 can do this:

and I've even installed a garden based enclosure thingy to house the 23cm transverter and VLNA remotely:

As ever, I don't really know what I am doing so we will see.

Been a bit of tropo on 2M today:

Local conditions.