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Sunday, 23 October 2016

Microwaves - now that's really nuts!


Following the build of my amplifier for 23cm here. I've been involved in some on-air tests of the JT modes on 23cm.

Here's a screen shot of my signels on JT65C as received by Tony, G4NBS in JO02af (Cambridge).

You will see multiple signals at times and we are sure this is due to Aircraft Scatter - I was seeing very much the same kind of thing on RX also. Anyhow, I am pleased to have logged 23cm JT65C QSOs with G4BAO. G4DDK and G4NBS.

I've been back up to Alport Heights in Derbyshire today with my 10GHz equipment from back here.

And have been listening to GB3FNY on 10,368.752 MHz:

I can find no trace of GB3LEX on 10,386.955 and can only assume it's off air.

Bonkers, egh?

Saturday, 22 October 2016

Tripping over SWR


I've been thinking some more about the linear for 23cm I started back here, and more importantly how I can generate a high SWR trip signal for the control board.

I have one of these directional couplers:

It has a forward and reflected port at -30dB. Then I remembered I had one of these kits, which built looks like this:

This will turn the sampled RF into a -ve DC voltage for the SWR trip on the control board.

Now, fortunately or unfortunately we now need to do some maths to determine the attenuation needed. The RF detector board contains two samplers, I have configured one for the forward power and one for the reflected.

So, starting with the forward port:

Assuming a maximum output from the linear of 150W, we can convert that to dBW using:

So my 150W RF becomes 21.8 dBW. Therefore the maximum power at the forward port of the directional coupler is 21.8 - 30 = -8.24 dBW.

Given that the maximum input power to the detector part of the board needs to be 3mW or 0.003 W we can also calculate that 3mW = -19 dBW.

Therefore I need an attenuation of the difference which is roughly 16dB.

Then assuming a trip level of 1.8:1 (or about 10dB return loss) the reflected levels need to be 10dB down from the forward so an attenuator of 6dB is needed on the reflected port.

Using my signal generator at 1,000 MHz (1 GHz) and adjusting the output we find this is the response of the board:

So it all looks pretty good.

I now need to do some reading up on how I can drive the trip alarms on the control board, but this should do the trick nicely.

Here's the dogs doing what dogs do:

Local conditions.

Wednesday, 19 October 2016

Wow - It's working then?


A couple of updates for you.

Firstly I ordered a 13cm 44 ele antenna, which duly arrived:

I suspect this one is designed for beaming round corner:

Not very clever!

Secondly, I was looking at my 6M logs recently and decided to create a map of my 6M contacts:

I just need that elusive USA opening!

Here's the 23cm amplifier I mentioned back here. It's finished now - I tried it on the air last night in the UKAC and received some good reports:

It's even wired quite neatly inside:

Cabinet feet and everything:

I'm really quite pleased with this. Local conditions.

Friday, 14 October 2016

More 23cm Power Required!


The other night, there were a few of us trying out JT65C on 23cm. I could decode quite a few of the other stations but couldn't be heard. This is no surprise as I was using only 10W out of my IC-9100.

Quite a while ago I bought a 23cm PA module from PE1RKI - now this is a fairly serious bit of kit that I hadn't got round to doing anything with - until today.

I also bought a number of other items to go with the PA including a case, a switch mode PSU and a Ultimate Amplifier Control Board from W1PQL.

I built the control board and here it is just being attached to the rear panel of the amplifier case:

So the first thing in this kit board is a sequencer to handle all the different things we need to switch as part of going from TX ro RX and back again in a linear amp.

There's an ALC output -ve voltage to keep RF at nil from the driving radio, until such time as all the relays have gone clunk. Once that's happened the -ve voltage is removed and the RF allowed to flow.

Secondly there's a sequencer to drive the TX and RX co-ax relays plus turn on the main DC supply to the PA and it's bias. I have taken the advice from W1PQL and switched both the main DC supply and the bias off during RX. The main DC supply is switched by an external FET switch and the bias by an external relay as the current requirements of this amp are too high for the board to switch alone.

Here;s the SMPS I am using or the amp; it delivers 28V (it's a 24V unit with a pot adjustment) plus a separate 12V output. I can't remember the current rating but this amp needs 11 Amps at 28V so there should be more than enough here.

In the image below you can see the bulkhead N-Type connectors for the outside world, the control board, the external FET switch and the N-Type relay on the amp output. There's an SMA relay on the input which you can just see the side of on the far left of the picture. The second image shows the SMA relay much clearer.

Here's a close up of the innards of the amp itself:

Now, the control board would also control a fan based on a thermistor input - however I'm just wiring the fan on permanently in this build. It would also take a feed from a directional coupler and switch the amp off in the event of high SWR on the output - a most excellent idea - however, I don't have a directional coupler that will work at these frequencies so I guess we are going to risk it....

Chopsey AKA Bastard Cat from Hell hasn't helped much today:

Local conditions.

Tuesday, 4 October 2016

It's all getting out of hand!


A weekend at the National Hamfest plus a trip to LAM Communications has resulted in two new radios.... One is new and one is very second hand....

I've had to make another shelving unit to accomodate... that really is it now.... no more!

Local conditions.

Saturday, 24 September 2016

RTTY Everywhere!


It's the CQ WW RTTY test this weekend, because of travel tomorrow and other commitments - only a very quick play this year.

Here's the 15M log as a map:

With SFI:86, A:9, K:2, R:49 - the 15M band hasnt been in bad shape today at all.

Local conditions.

I'm off to the Kingdom of Saudi Arabia tomorrow - I think Maggie cat wants to come too!

Good, egh?

Friday, 23 September 2016

TXing WSPR with the Red Pitaya


You may recall some time ago that I had a fiddle with a Red Pitaya? This was back here in this post.

So further to the WSPR RX I was doing back then, I made a request via Mike Richards G4WNC (He writes the Data column in Practical Wireless) to add a PTT switch to the software. The TX signal was on the output connector and the RX input on the Input connector - I only have one antenna and I wanted to switch between the two.

Well, lo and indeed behold, the code for the Multiband WSPR transciever has been updated here.

I've downloaded the new software which includes an extra module called gpio-output which switches the DIO0_P pin (its pin 3 on the E1 connector) to 3.3V when the device is in TX.

Now, I noted a few things when I downloaded the new files and executed the make command:

  1. The Makefile downloaded ended up with a .1 extension and needed to be renamed.
  2. The new .sh files had the wrong permissions and needed to be chmod ed to be executable
other than that updating the software and re-building was easy. 
To accommodate this I have made a very simple PTT switch (please excuse my TinyCad capability):

which connects to the Red Pitaya Pin 3 and GND on the E1 connector and then feeds a PTT line (grounded during TX) to my TX/RX relay.

The only Relay I had was a latching type so I have made a board from W6PQL to drive the relay from a grounded line:

This board looked like this when I had it under test:

And this is what the latching signal looked like before I added some diodes on the relay coils:

Now, you may remember that I also purchased a board from SV1ASM to add some extra drive to the Red Pitaya output, here it is under test:

Now, this is supposed to give me about 14dB of gain, but my tests suggest it's a bit short. The Tracking Generator is at -20dB in the test below:

It may just be that I am not driving it hard enough in the test above, as I am getting more like 7dB gain. It seems to be good to about 100MHz though - I will look more at this later.

Before I hooked all this stuff up together, I did some tests on the Red Pitaya output lines. This 'scope screen grab is showing the TX output plus the IO line at 3v3 during TX:

And here we have the 'scope connections to the output connector and the E1 lines:

So, hooking all this lot together, we have a mess like this:

I need to make a low pass filter for the output; mine is currently configured to TX on 30M. Once I have the LP filter I will stick this on the air and see how far I can hear and be heard.

This project is now a good starting point for lots of other TX/RX type ideas on the board.... next though I think I am going to have a go at the Vector Network Analyser.

Here's Florrie the Ham cat being almost completely in the way throughout:

 Good egh?