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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.

Tuesday, 28 May 2019

Es on 4 - really?


I've always found the 4M band quite a challenge, but also very interesting. I don't really know how well the 'parasitically' fed antenna works I built here, but I certainly put out some RF.

The linear works on 4M, but is rather pants - very inefficient - not much RF out for an awful lot of current consumption.

There's been some sporadic E on 4M yesterday:

and today:

Yesterdays hop over to LZ2WO in Bulgaria is a reasonable distance at 2149.15 km (1343.220 miles), at a bearing of 109.3 degrees.

Good, egh?

Saturday, 20 April 2019

A Portsdown Conundrum


As part of my Es'hail-2 experiments, I am now preparing a DATV TX system for the satellite. I've ordered a Spectrian linear amplifier which seems to be the way to go, it looks like this but isnt here yet:

But in the mean time, I have been playing with an eBay sourced "wi-fi booster":

I have modified this to be permanently in TX by shorting pins of the op-amp as per many published explanations:

and simply connected this between the 23cm output port on the Portsdown and the Wi-Fi antenna that came with the amplifier.

Firstly, to test all is well with the setup, I have set the Portsdown to:

  • Frequency 146.5MHz
  • Modulation: DVB-S
  • Encoder: MPEG-2
  • Output to: Lime Mini
  • Source: TestCard
  • SR 1000
  • FEC 7/8
  • Lime Gain 88
This feeds from the 2M output port of the Portsdown to the linear I made back here and then to the 2M beam on the mast.

I have connected a "white stick" antenna thats on the house somewhere to the input of the MiniTiouner from here and these are the results:


Now, I change the Portsdown TX frequency to be 2407.75 MHz, change the antenna on the MiniTiouner to be a 2.4GHz patch on the bench:

and this is the result:

With a suitable piece of wire shoved into the front input socket on the spectrum analyser I can see the 2.4GHz signal I am transmitting:

So I am really not sure why I can't decode the TV signal on the MiniTiouner - any ideas anyone?

** UPDATE **

So, thanks to the BATC forum and mainly G8GKQ, we concluded this was a phase noise issue.

I did some experiments starting at 23cm (1296 MHz) and slowly increased the TX frequency until it failed; I found this to be at 2150 MHz. It turns out the problem is ripple in the PSU for the MiniTiouner - so this is an RX issue not a TX issue as I suspected.

The MiniTiouner includes a buck converter to take the DC input and drop it down to 4V to feed the on-board regulators. I was feeding this with either 12V or 18V and also routing this input voltage up the coax to the LNB. It seems that the higher the voltage, the more the ripple.

I've modified my MiniTiouner now to run the internal RX electronics from the USB power (I have it connected to a USB 3.0 PCI card with an internal PSU connection)  and only now use the external switchable 12/18V for the LNB power.

Not sure I fully understand the reason for the problem, but it is now fixed.

Local conditions.

Saturday, 6 April 2019

70cm DATV - Portsdown again!


You may remember a while ago I built a Portsdown 2019, well today I've been thinking about how to get that on the air on 70cm (437MHz).

John, G4BAO does a nice driver amp kit for this frequency, and I have built one here today:

I've built and tested it as per his instructions, and then built a fairly simple circuit to switch the bias line which needs +12V on PTT. The schematic below is built on the veroboard you can see in the image above and takes a ground on TX line from the Portsdown and uses that to switch the VCC to the amp, turn on an LED and also provide a ground on TX line out (to go to the PA perhaps).

I've done some very initial tests and the spectrum analyser image below is created with a 30dB attenuator in line:

Without the driver amp in line, the output was measured at -29dBm (so about +1dBm without the attenuator) and then -6.59dBm with the driver amp in line. I make that a gain of about 23dB which seems bang on the money.

The driver amp is now completed in the box you see atop the Portsdown.

Good, egh?

Monday, 1 April 2019

Digital TV - really? QO-100 again!


Over the weekend I have been playing with the software KG-STV.

This is a kind of digital TV; its slow scan TV that's digitised on TX.

It took me a while to get the software to key the radio - eventually I figured out it doesnt seem to work if the selected COM port is > 9. Hey ho, as my PC Is COM port city, I had to shuffle some stuff about.

Here's two instances of the software running at the same time; the top one is my TX signal going up on 13cm and the bottom is my RX of the signal on 3cm.

And here is the same image as received by CT1BYM, Miguel:

and here some more images Migual has been kind enough to share. This is his RX setup:

How cool is that?

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Friday, 22 March 2019

SSTV - though a Satellite?


Been playing some more with my Es'Hail-2 setup.

I noticed yesterday some SSTV signals on the band from Mauritius; I've not used SSTV before so I installed MMSSTV and have since had some QSOs.

I've annotated some images and created some templates in the software to enable reports and the like to be exchanged:

It's really quite fun!

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Sunday, 17 March 2019

ADSB Receiver - Really?


For some time I've run an ADSB receiver here called PiAware - It's by flightaware, runs on a Raspberry Pi and uses an RTL dongle and a short bit of wire wedged in the shack window as an antenna - not the best.

Today I've been making a better antenna, a masthead amplifier and checking for improved reception. I recorded my musings as a video:

Fun, egh?

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Sunday, 10 March 2019

es'hail-2 dish feed


Very much inspired by the fun back here, I figured it would be great to try and make a better single feed for the dish for both bands.

This seemed to be just the ticket.

Not this needs to be plumbing, not electronics!

I paid a visit to fellow ham and insane constructor Ian, G4EVK; who has some amazing model making equipment and a good plumbers blowtorch!

Here's some photos of the build:

I'm waiting for a "rocket" LNB that I hope will fit on the end of the waveguide (read 22mm pipe) using a compression fitting, I have also used the trick from here to check the 2.4GHz return loss - after a little bit of bending it's now looking spot on.

Yesterday I very nearly mowed the lawns, today we woke up to this:

Let it snow.....

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** UPDATE **

I have used the lens from a "rocket" LNB on the front of the feed and removed the feedhorn from an Octagon LNB (with a hacksaw) and connected it all together with a 22mm compression pipe connector and some waterproofing with some silicone. I have also modified the LNB to take an external 25MHz signal (as above):

I've used the same trick I used back here to measure the return loss on 2.4 GHz and its around 20dB; I have also lashed up the receiver on the 10GHz downlink and that is working just fine.

Now, how on earth can I weather proof this?

Miss Maggie and Miss Pepper Cat seem to be economising by using the same bed? Bonkers.

Local conditions....

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Sunday, 24 February 2019

Portsdown - again?


I've been building myself another Portsdown DATV transmitter.

This is the Portsdown 2019 - instead of the Filter Modulator board in the last version, this uses a LimeSDR Mini.

I'm rather pleased with this new build, it's a lot neater than the 2018 version I made:

You can see the LimeSDR in the picture above, its in a 3D printed case - that's now got a 20mm square fan fitted.

The front panel is a lot better than the last build, if I had got the holes for the LEDs upright it would have been even better.

I wanted this second Portsdown so I can take it portable without destroying the shack to remove the 2018 version.

I'm rather pleased with this.