Search This Blog

Monday, 18 June 2018

Splashing Complete


Following my recent post back here about my bonkers SPE 1.3K-FA Amplifier, I thought I should post an update now it's back from its short vacation in Italy.

It has been back to the factory for three issues:

  • Front Panel missalignment
  • Very noisy fans
  • Attenuator fittment

So, I am please to report all three issues are sorted on the amplifier and the drive levels, whilst still somewhat bonkers, are very much more reasonable and within the range that I can actually control from the radio.

Luckily, my main radio (The TS-990) is extremely well thought out, and within the menu system you can set the granularity of the power out adjustment:

So  I can now set the output level exactly as I require on each band.

Here's a quick video of the amplifier now its back:

You can see the automatic band switching working - I have this working on both the Kenwood and my IC-7610 radios - you can also see that 5W drive now gives me 250W and 8W gives me full UK legal limit.

I haven't yet played with the in-line attenuator I made back here, but will do soon.

I've actually used the output from my MicroHam DigiKeyers to drive the CAT control from the rigs, so I can also keep the CAT line into the computer for logging and other control purposes.

All good.

Sunday, 17 June 2018

It's a Kind of Magic.....


6M AKA "The Magic Band" sometimes simply amazes me.

Today I have worked Cuba, Puerto Rico, Dominican Republic and Haiti.

Here's my all time 6M QSO log as a map:

Amazing, isn't it?

Sunday, 10 June 2018

TS-990 on 144MHz


Following some discussions at Ham Radio 2018, Friedrichshafen, I've done another example video of the TS-990 with a G4DDK transverter:

There's a document I've compiled on the transverter setup here.

Here's one of the halls full of goodies that I don't need from the rally - it really was very good:

and some of the test gear on offer:

And here is my very lovely Luna cat enjoying a snooze in the shack:

and finally, Miss Florrie Cat:

Good, egh?

Thursday, 7 June 2018

Taming the Amplifer


Following my recent purchase of an SPE Expert Amplifier I described here, I've been pondering how to keep the amplifier under control. It is currently back at the manufacturer for three issues:
  1. Extremely noisy fans;
  2. Bent front panel;
  3. Attenuation fitting.
I attended Ham Radio 2018 at Friedrichshafen this year and spoke to the owner (Dr. Gianfranco Scasciafratti I0ZY) of SPE while I was there. I tried to explain my concerns about such low drive level requirements and the reliance on ALC and associated risk of failure; the conversation concerned me because he didn't seem to want to listen to a word I said.

SPE have sent a video of my amp under test:

So hopefully it's on its way back to me now.

I've designed a thingamabob to put in-line with the amplifier as recommended by I0ZY to provide attenuation to the input drive level. Gianfranco suggested that the attenuation could be permanently in-line as on receive it "didn't matter". However, I'm not happy with that so I have come up with the following to switch the attenuation in line during TX and remove it during RX:

In reality the build looks like this:

There are quite a few bits in there, there are two coax relays (50 GBP), the connectors and the resistors in the Pi Attenuator (50 GBP) plus the case and other assorted bits and bobs (75 GBP) - so a total of 175 GBP just to tame the amplifier. Of course, I will need two of these if I want to use the amp as designed with two radios. I find it odd that they would recommend such a solution - why not just put sufficient attenuation in the amp to start with?

The gubbins has a good flat response from 0 to 50Mhz and also give us about 6.16dB of attenuation.

Throughout the build construction Florrie Cat has been assisting:

and somehow, you just know it's not going to end well:

Odd situation, don't you think?

Monday, 4 June 2018

Over the pond on 6M


After many years of trying, FT8 has given me my first QSO over the pond:

I'm rather delighted - it's quite an opening going on:

Good, egh?

Friday, 25 May 2018

Tuning an ICOM


I've been fiddling lately with external ATUs and most recently the linear I mentioned last time.

More and more I keep wanting an easy way to generate a tune carrier from the IC-7610. Now, when Kenwood designed the TS-990 (the best radio in the world) they got everything right. There is a tune function you can allocate to one of the user programmable buttons, and also you can set the tune power by band - what could be simpler?

Well, with the latest and greatest Icom radio, you have to stick the radio in FM or AM or RTTY, press the Transmit button after adjusting the power to the required level and sticking a chicken down your trousers and facing north. The last bit isn't actually necessary, I was just checking you were paying attention.

So here we have the answer to the problem:

The switch in the middle of the schematic selects the internal or external ATU and the outside switch (in my case a push button) enables the carrier:

The whole thing connects to the external tuner connector on the back of the majority of Icom radios, which I've made a plug for by butchering an old PC PSU connector:

Easy, don't you think?

Thursday, 24 May 2018

Splashing Out Somewhat


I decided to get myself a new toy. The idea is that this replaces the linear amp, the antenna switching, the radio switching on HF plus the ATU - all in one box. Also it doesn't need to "warm up" or tuning on each band.

So I brought it home, somewhat excited:

Now, I first tried it with my TS-990 as the exciter. The manual doesn't actually tell me anything about required drive levels, but anything from the TS-990 generates "INPUT OVERLOAD" error - even only with 5W output. So more consultation of the manual and it seems they are keen on you using ALC connections to control the exciter drive levels, so I hook up the ALC line and then this is what happens:

Now that's really quite strange.

Next I try the IC-7610, connect up the ALC and PTT lines and it seems to work OK, however, I have very little control over the RF out - in fact I cant get the amplifier to deliver less than just over 500W output even on the lowest power output setting. That's not very clever - I want to be able to control the RF and gain of the amplifier.

So, some email back and forth to the manufacturer and it seems there are two versions of this amp. One for the US market which includes an attenuator in the drive line so that 25-30W of RF is required for full output, and an EU version without the attenuator.

SPE sent me this table which shows the input RF needed for full output by band and power setting (you can have the amp on Low, Med, High):

So at this point I fell off my chair! This amp eneds only 2W of drive on the low bands for maximum output. The only way that low level of drive is possible with most modern transcievers is by using the ALC all the time to restrict the output of the rig - which is exactly how this amp is "designed" to operate. I think the issue with the TS-990 is that despite ramping the ALC voltage to the most -ve it can, the output is still too high to drive the linear.

Either way, there is no way you can set the controls to deliver, say, 200W output. You can have maximum bananas (which seems to be 500W, 1Kw and 1.3Kw) depending on the Low, Med or High selection of the amp power switch.

The manufacturer recommends you run your rig at FULL RF output and rely 100% on the ALC circuitry to protect the MOSFET in the linear from being fried. I personally don't like this theory at all.

Needless to say the amplifier has been returned today for modification to the USA version so I have some hope of controlling the RF output.

Here you see the drive level of 3W:

which produces 508W out in the "low" power setting:

Bonkers, don't you think?

Monday, 21 May 2018



I'm forever adding bits to projects after they are complete. The recent PTT Switching box I made back here is no exception.

Since the original design I've added/changed a few things:

  1. I've significantly sped up the sequencer;
  2. I've added automatic relay switching for the DRV and RX antenna connections to the TS-990. This means that the transverter RF connections are automatically selected when the band select switch is on 2M or 4M. There's even a delay to the relay activation so that passing the switch through that position doesn't falsely change things over;
  3. I've included all the external switching into the schematic as best I can

So there are 4 external PTT connections - these are the triggers to the sequencer and are selected as Radio 1 - Radio 4.

Associated with each Radio PTT input is an ALC output back to the radio so that the selected radio does not generate any RF until the sequencing is complete.

There are PTT outputs to the 3 amplifiers; HF, 2M and 4/6M - these are only keyed when the band switch is in the appropriate place.

There are PTT outputs to both by transverters. Ditto for the amplifiers, these are only keyed when the Band Select is in the appropriate place.

The full schematic is:

and also in a higher res PDF here.

This is our very beautiful Bonnie Dog; in our local dialect her facial expression is translated as "thank God it's spring".

Local conditions.

Thursday, 17 May 2018

DB0XY on 432.475


Some interesting propagation on 70cm this AM:

Fun, egh?

Friday, 11 May 2018

PTT Revisited


This all started when my 2M masthead preamp from here failed. This can only be because there has been some RF into the device, as everything else int he preamp looks fine.

So, how can this have happened?

On 2M, the preamp is powered via the coax and all this is taken care of by my Beko Amplifier.

So to add some more "belt and braces" protection to this I decided to re-visit the PTT switching arrangement I created way back here. Now I've learnt a lot since then and have built a few sequencers now, so the ideal solution seems to be to keep the same switching concept, scrap all the relays and use a sequencer. I also decided to add an ALC output to each radio so I can keep RF at bay from source until the very last sequence event has occurred.

Here's the design I came up with:

I've uploaded a PDF of the schematic here.

This copies a number of previous sequencer ideas but now also adds a ALC -ve voltage output that I can switch to the appropriate radio with a front panel selection.

U1D is configured as an oscillator which is then -ve rectified by D6 and D7 and then switched on and off by the sequencer using U3.

Here's the finished build just about to go into test:

You can see that I have also used some co-ax relays (the latching type) and the drivers we finalised here to switch the DRV and RX Ant connections between my 2M and 4M transverters. The box also has a radio select switch (1-4) and also a second selector for HF, 6M, 4M and 2M.

The second switch operates the HF linear only in the HF setting, the 6/4M linear only in the 6M setting, the 6/4M linear and the 4M transverter in the 4M setting and finally the 2M linear and the 2M transverter in the 2M setting.

I just need some feet and some knobs!

**UPDATE** Some more info on this project here.

Saturday, 5 May 2018

3cm Learning


Ween up a big hill today to play on 3cm:

Pretty nice day in my bit of England:

Here's a video of the Finningley beacon as RX today:

Here's what I learned today:

  1. The beam heading on the dish is extremely sharp;
  2. I need a more accurate way to determine beam headings;
  3. I need a way to turn the mast whilst also tuning round on the radio;
  4. The fitting of the mast into the base is a bit loose; the pole isn't completely vertical
All in all, 3/10 could do better. But I have made QSOs now on 10GHz and that feels like a great achievement.


Here's Miss Pepper, assisting as per usual:

Sunday, 29 April 2018

RIP Chopsey

My beautiful Chopsey cat died this morning.

He was our git bastard cat from hell and we loved him dearly.

Friday, 27 April 2018

Completing 23cm


You may recall last time, I was changing my portable setup for 23cm. Well, on my travels I found a Kuhne Electronic PA for 23cm and have installed it in the waterproof enclosure with the rest of the gubbins:

I have a 14dB attenuator between the transverter TX output and the PA input. Thats a bit bigger than I need, but I don't have anything else suitable at the moment. The G4BAO amplifier that I now have here (thanks John) is going to get utilised as a DATV amp (I think).

I've been fiddling with a cheap Chinese board with a variable attenuator on-board. You can control this using the DIP switches on board or by software. I've written a very simple bit of Arduino code and interfaced an Arduino Nano to the board using serial comms:

This allows me to step through from 0-30dB attenuation in 0.5dB steps. Really quite neat for just under £12 GBP delivered from the far east! I may decide to use this to get the transverter to PA attenuation exactly on the money - let's see.

I'd like to introduce you to the best and most useful screwdriver in my possession:

This belonged to my Father who sadly passed away just over 31 years ago:

I'm often heard muttering to myself "now where's Dad's screwdriver". If it's of interest Dad, I still use it regularly!

Local conditions.

Friday, 6 April 2018

23cm Portable


Following my changes to the 3cm and 13cm setup to become more portable, I decided it was only fitting to re-make the 23cm setup I made back here. I'll reuse the PA and the transverter.

The first stage in this project will be to create a new sequencer, much like the 13cm version, so we can switch the transverter, a VLNA and a co-ax relay.

Here's the design:

and in reality, this looks like this once built on stripboard:

I've already got a G4DDK VLNA for 23cm assembled here, and coax relays aplenty. John, G4BAO is just tweeking my 23cm 60W PA and once I have all the bits, we can mount them in another waterproof enclosure the same as the 3cm and 13cm setups.

As part of the sequencer design, I finalised my latching relay driver circuit and have finished up with this, included in the sequencer diagram above:

So this is what I have so far:

You can see the SG Labs transverter, the sequencer from above, the VLNA and the TX/RX switching - just the PA to be added.

I've tested one of my attenuators to get an exact value at 1296.2 MHz using zero span on my Spectrum Analyser Tracking Generator as a signal generator and concluded a value of 29 dB (its rated as 30dB).

So then I used this in line to my XL Microwave power meter to measure the output:

And in CW with key down on the FT-817 and 5W output, that reads 6.1dBm so we then add the 29 dB for the atenuator and I get 35.1 dBm which is about 3.25 Watts out of the transverter. It's only supposed to output a nominal 2W and 2.5W max - so I'm not too sure whats going on here.

I've set up the transverter to work with full bananas out from the FT-817 whilst on DC power, and the LEDs that indicate input power levels and output SWR are both shining green:

Here's a crazy cat of mine en route to a portable operation:


Tuesday, 3 April 2018

Finishing 3cm


Following my musings back here, I've finished the portable 3cm thingamabob:

I've moved the sequencer to be on top of the transverter box and added some surplus heatsyncs to the PA module.

I've even made a metal sheet and drilled it so it all fits on the arm of the dish.

I've also been up to Alport Heights today to test the portable 13cm setup:

Here's a clip of the reception of GB3ZME from the top of the hill:


Good, egh?

Sunday, 1 April 2018

13cm Sked


Just running a quick test before heading for the hills tomorrow for 13cm sked with @G4ASR.


Thursday, 22 March 2018

13cm Complete


I've received the PA for the 13cm masthead project and added it to the box with a heatsync and suitable input attenuation:

I haven't stuck it down in the photo hence its a bit wonky.

The documentation with the PA suggests that about 5.1V on the monitor pin is close to PA saturation so I have adjusted my input attenuator to give just over 5V from the PA monitor port with CW key down.

With the output connected via these two attenuators:

to my XL Microwave power meter I am reading -2 dbM so that's about 38 dBm or 6.3 watts - it should be closer to 10 Watts.

To check the value of the attenuator at 2320 MHz, I used the spectrum analyser and tracking generator I made back here in zero span at 2320 MHz, and compared the signal with and without the attenuators, I measure a signal of +10.4 dBm without the attenuator and -29.2 dBm with. So that makes the attenuator 39.7 dB - so pretty much on the money.

Local conditions.


I kept finding my TX/RX switching was going into some kind of oscillation on RX. The unit would rapidly switch between TX and RX until I pulled the power. Oddly (and still somewhat a mystery) this only happened when the +ve voltage to the VLNA was connected to the sequencer. No VLNA power, all fine, attach VLNA power, TX/RX oscillation.

There is a VOX feature in the transverter that switches to TRX on detection of RF on the input; changing that to have a long detection time (a jumper on the transverter board) has cured the problem.

I have no idea either.

As SG labs don't seem to link the transverter datasheet on their site anymore, it's included here for reference.