A disk-what? Ah, a Discone!

Well,

Today has been a day of antenna fiddling. The first thing I did was put up a Discone antenna on the front of the house:

This is supposed to be a general coverage receive antenna from 25MHz to over 1.3GHz plus it is resonant for transmit on the Amateur 6M, 2M, 70cm and 23cm bands.

Here's what it looks like connected to the return loss bridge and Spectrum Analyser:

The markers at the bottom of the image above show the resonant points we are interested in and it does indeed seem to be a reasonable match to 50R at those frequencies (as is a 50R resistor, of course). How good an antenna it is remains to be seen. I am hoping this will hear more of LEO satellites than the collinear I have.

We have had some more really bad weather over the last few days and very much by luck I found a broken jubilee clip (Read hose clamp) in the garden yesterday. Looking up I could see it was off the 4M and 6M beam antenna I installed back here:

http://g0mgx.blogspot.co.uk/2013/05/thatll-never-work-will-it.html

So I have had the antennas down again today, it's surprising how big my "mini beam" is when it's on the ground:

You can see that I have to remove the outer parts of the one element to get it past the fence next to the raised border in the garden! But I have replaced the clip and also altered the resonant point of the 4M section to be exactly at the Meteor Scatter frequency of 70.110MHz.

After adjustment the "dip" is now ~70.12MHz with a return loss of > 32dB ; the SWR at 70.11 (my target) is 1.05:1 and across the band is no more than 1.7:1.

and at 50.23MHz the SWR is a respectable 1.2:1:

Looks pretty damn fine to me!

Cat's been next to useless:

Fun, egh?

Honestly? It's a mess!

Well,

I've been boxing the components for the 70MHz linear amplifier that I have been making:

http://g0mgx.blogspot.co.uk/2013/12/testing-times-for-my-linear-project.html

today. The control software is still very much under development, but in my usual build a bit, test a bit fashion, I need everything to be wired to the Arduino processor board now so I can make progress.

All in all, here's the list of separate bits I've ended up with:

• Linear brick and heatsync
• 48V SMPS Power Supply
• 9-0-9 transformer for DC supplies
• Fan for cooling
• Veroboard containing the ancillary electronics for the Arduino relay and fan control plus the DC regulators for the +24, +12 and +9 rails
• Low pass output filter
• Arduino
• LCD display
• Directional coupler for output forward and reflected power reading
• **huge** coax relay for the output switching
• input attenuator
• small coax relay for input switching
• Current shunt

So all together there is a lot more than I bargained for!

Here's what it looks like today:

and I have to confess that this is one big mess that I hadn't set out to make. It should work OK, but the "junk box" style of part sourcing has resulted in some really bigger than needed bits....

Florrie cat's not been helping much today:

 

Progress, though, egh?

Now that the smoke has settled

Well,

You may remember the mishap I had with my FT-847 back here:

http://g0mgx.blogspot.co.uk/2013/11/my-ft847s-got-no-nose.html

It's been repaired, and as predicted I had melted some of the components in the 4/6M low pass filter. I had also burned some of the PCB tracks - I got lucky really as the PA itself survived.

To further my adventures on 4M Meteor Scatter I think I need to find a better way of generating some high power RF without running the 847 at maximum bananas. Hence a new linear project has been born.

I've scribbled down my thoughts over the design, I want to include some software based control and alarms so I can watch out for:

• To much drive
• High SWR
• PSU problems
• Over temperature

It would also be good to include a software based power measurement and SWR reading on the output.

Here's the rough starter design:

I've stuck the appropriate numbers into Elsie and have the Low Pass Filter design also:

I've ordered a 300W 50-75 MHz RF module (no PSU, heatsink or cooling) so I'll start to think about the software for the linear controller over the next week or so - it will be Arduino based for sure.

There was a lovely UK morning captured on Antenna Cam here today:

Good, egh?

Antenna Complete!

Well,

Perhaps you remember the antenna I started to put together last weekend and then realised that the bits for the 6M sections were the wrong size? It was back here:

http://g0mgx.blogspot.co.uk/2013/05/thatll-never-work-will-it.html

The correct parts arrived today to complete the antenna, so the tower has been down again. I've just flicked through the archive from "Antenna Cam" and here's me up the ladder fiddling with the top bracket prior to dropping the tower down:

If you look closely in the above image you can see me fiddling, but you can also see that the closest element on the HF beam is a bit "out of bonk". Here's the antennas back up again and I've fitted the parts to the 4/6M beam and also straightened out the HF element:

And finally here's an image of the antennas back up with the weather a little clearer and them pointing back to the SE:

The 6M part of the top beam is no longer resonant at 55MHz, but seems to be a good match on the 50MHz amateur band!

It's perhaps just a little too short but it's more than acceptable for my requirements; the resonant point on 4M or 70MHz hasn't moved.

Good, egh?

That'll Never Work - Will it?

Well,

The VHF antennas here have always been somewhat of a compromise. Recently I moved my 4M or 70MHz antenna from the side of the house and put it on top of the HF antenna on the main mast. I also took down and filed (in the hedge) a 6M or 50MHz antenna. I saw this a while ago and wondered... could this really work:

InnovAntennas 4 & 4 ele

So, you guessed it, I bought one.

Here's the antenna as it starts to go together:

As you can see, there are 4 elements for 6M and 4 elements for 4M on the same boom. The thing that I didn't (and still don't) understand is how the thing works electrically as the 4M elements are all parasitic (there's no wires connected to them from the RF supply). The antenna has a direct coax connection without any kind of connector:

There's plenty of self amalgamating tape under the white PVC tape you can see, the connections themselves were then coated with Copper grease. The antenna also needs a coax wound balun - this is preventing me from feeding the antenna directly with Westflex 103 - it's just too thick to wind tight enough. I've had to connect a length of RG213 to the antenna, use that for the balun then have a join to the 103 close to the boom.

I then brought the tower down and changed the antenna on the top for this one:

While the antenna was in this position I attached the analyser thingamabob; the 70MHz resonance looked really good, but the 50MHz resonant point was more like 55MHz.... hmm I thought, perhaps I should raise the antenna and see.... no change at all.

I scratched my head for a while and re-checked all the dimensions - they seemed correct to me, here's the diagram I was following:

Suddenly I realised that the element centres that are labeled as 1800mm on the diagram are only 1500mm on the antenna! A quick email to InnovAntennas confirmed that I had indeed got the wrong parts.

The antennas are back in the air:

But the 6M or 50MHz elements on the top antenna are currently exactly 300mm too short.

Useless, hugh?

Is this what I was waiting for?

Well,

I'm still in A71 land, but I have been checking my WSPR beacon that I left running on 4M from time to time. I mentioned about it here:

http://g0mgx.blogspot.co.uk/2013/05/movements-are-afoot-its-all-go-you-know.html

But here's what I found this time:

So my 20 watts on 4M has made it all the way to PA0O - clearly there has been some propagation while I am away (typical).

Good, egh?

Movements are afoot.... It's all go you know...

Well,

Been fiddling with antennas a bit whilst home this time, I've moved the 4M antenna from the side of the house and put it on top of the HF antenna on the main tower.

Here's a picture from "Antenna Cam" at dawn this morning:

and here's one from just a bit later on:

You should be able to see that the 4M beam is now sat happily on the top of the tower. Inspired by the site of Brian, G0MJI:

http://www.qsl.net/g0mji/

I've set up a WSPR beacon on 4M.... time will tell but it sounds like a lonely kind of activity to me....

I've also been fiddling with Ham Radio Deluxe (HRD), my internet router, the FT-5000 and various other bits and bobs to try and see if I can control (and operate) the Yaesu FT-5000 radio remotely (read from A71 land).

So, HRD runs on the shack PC, this communicates with the radio over the conventional Yaesu CAT interface. As is well documented the modern radios allow control of just about everything via this interface.

Now, you then set HRD running in remote mode and then run the client application on the remote PC (in my case this is a laptop). With a bit of fiddling and a port open on the router I can now control the FT-5000 remotely, this is what HRD looks like on the client PC:

So this will be something interesting I can fiddle with next time I am away from home. I've also set up a remote desktop access to my shack PC so in theory, I should be able to connect and run RTTY via logger as if I was sat here.... shouldn't I?

You might remember an episode of "extreme soldering" from quite a while ago:

http://g0mgx.blogspot.co.uk/2011/10/its-done-well-extreme-soldering-is.html

Well, I've been fiddling with this SDR again, It's really quite good fun, here's a screen grab from the Software, my waterfall is a little too intense, but you get the idea:

Fun, egh?

Mixing Better than Before (70MHz)

Well, following on from my efforts at a 70MHz "transmit converter" here:

http://g0mgx.blogspot.co.uk/2012/06/even-more-4m-or-70mhz.html

I've made some of the changes I said I would do. The main two things I have done are re-tune the local oscillator for the 60MHz harmonic rather than the 80MHz harmonic that I was using previously and also re-made the board thinking about layout and symmetry where required:

So now I have a 60MHz oscillator mixed with my 10MHz frequency reference I made here:

http://g0mgx.blogspot.co.uk/2011/07/ocxo-oh-you-mean-ocxo.html

to make 60 + 10 = 70MHz signal. As you can see from the output on the spectrum analyser, the signal is now really much cleaner than before, even the 60MHz oscillator is at least 45dB down. I always like to remember here that 6dB is half voltage, so 45dB down from the 70MHz signal is a really good result.

So what I need to do now is swap the 10MHz frequency reference for the DDS from here:

http://g0mgx.blogspot.co.uk/2012/06/its-been-ages.html

and check that the bandpass filter at the output from here is wide enough for the parts of the 4M or 70MHz band that I am interested in.

The theory here is that a 10.0 to 10.5 MHz input signal should give me a 70.0 to 70.5 MHz output signal - if (and it's quite a big if) the bandpass filter will let that range of frequencies through.

Once thats all sorted I need to think about an RF amplifier for the output and an attenuator for the 10MHz input which eventually will come from one of my HF radios. The RF amplifier will be designed around an MRF151 power FET (because I have some), so that's something to start the next round of fiddling with, I also have a neat 48V switched mode PSU that should do nicely, now maybe I can make something for 6M also....
I even managed to be here and work someone on 4M the other day using the modified FT-847; it was SP6GWB, Stainslaw. He's got a really neat site here:

www.sp6gwb.pl

but thanks for the QSO! My first on 4M....

More madness to follow I'm sure, but it's good though, egh?

Even More 4M or 70MHz

I've been fiddling in the shack today with an oscilator I started back here:

http://g0mgx.blogspot.co.uk/2012/06/4m-70mhz-and-counting.html

It's basically an 20MHz crystal oscilator that's multiplied up to 80MHz. I've then fed that into a mixer just like the one used in the BITX here:

http://g0mgx.blogspot.co.uk/2010/12/bitxing.html

And mixed it with the 10MHz reference oscilator I made here:

http://g0mgx.blogspot.co.uk/2011/07/ocxo-oh-you-mean-ocxo.html

The idea being that 80MHz - 10MHz = 70MHz.

There are a couple of amplifier stages in there followed by a (my attempt at) band pass fiter. The iportant thing with mixers is that you get the sum, the difference and all sorts of other harmonic products out, so you have to really filter out the one you want else you just get a real mess!

It all looks rather badly built and like this:

But the output on the spectrum analyser looks like this:

So you can see that the 70MHz signal is the main "feature" in the ouput (It's 10MHz per cm from left to right where the far LHS peak is 0MHz and it's also 10db per cm vertically).

I think I will re-make this with consideration for all the bits and where they need to be; then I'll think about seeing if this will make a transmit converter for 4M.

Good fun, egh?

FT-847 PA Mod - there's a better way!

Well,

Following the mod of the PA filter in my FT-847 here:

http://g0mgx.blogspot.co.uk/2012/06/ft-847-that-i-have-here-includes-70mhz.html

I've been thinking some more about this; given that the PA is capable of delivering 100W on 6M or 50MHz, it wasn't clear to me why I Was struggling to get more than about 60W out on 4M or 70MHz. There had to be some very large inefficiencies in there; then I discovered this link:

http://www.70mhz.org/847filters2.pdf

And all became very clear, very quickly! I don't know what package Marc used, but he has done a fine job. Once again the FT-847 came apart and I kept removing bits until I had discovered the PA board:

Now, to make the mod described by PA1O, Marc, I need to lift the PA board out. This was a bit scary as I had to remove all the screws holding the MOSFETs onto the heatsync and then very gently flip the board over. Once upside down, I could clearly see the two caps described in the article:

Then with rather a lot of brute force and ignorance I managed to get the one cap removed; it's been stuck down rather firmly so it kind of came off in bits with no hope of ever putting it back again!

So, after carefully putting it all back together (including a dab or two of heatsync compound), the radio is back together. I've removed the ferrite I added when I did the previous mod:

http://g0mgx.blogspot.co.uk/2012/06/ft-847-that-i-have-here-includes-70mhz.html

And I now have a full 85 - 90 Watts out on 70MHz with about 16A current draw and still have 100W output n 50MHz with a reduced current draw of 17A (it was about 21A); so I think we can conclude that efficiency is improved.

I can't see any negative side effects of this modification to the PA, the output seems stable on all bands but I'll be sure to let you know if I find out differently.

I'm going to look at the output spectra a some point in the near future to make sure the signal is nice and clean and all harmonics are suitable suppressed.

Cat's not impressed:

Good though, egh?

FT-847 Pre-Amp Installation

So, now that I have built and done the basic DC test on the new FT-847 pre-amp last time:

http://g0mgx.blogspot.co.uk/2012/06/ft-847-4m-70mhz-pre-amp-mod.html

It's time to install the board in the Radio. This looks to be a fairly straightforward operation, replacing one board for another.

Here is the old "daughter" board inside the radio just prior to removal:

And this is the gap - this picture was taken to ensure I could remember where the old board wired into the main board - re-fitting being the reverse of removal!

So here is the new daughter board which includes the 70MHz pre-amp just being tacked into place:

And here with the wiring complete:

All I need to do now is find a suitable signal and peak the variable inductor for maximum smoke; that should be a doddle. I can hear the relays operating as the tuning range enters and leaves the operating frequencies, so something is working as planned.

Not bad, egh?

FT-847 4M (70MHz) Pre-Amp Mod

As I mentioned in my last post here:

http://g0mgx.blogspot.co.uk/2012/06/4m-70mhz-and-counting.html

I had bought a mod for the FT-847 to improve the reception on 4M (70MHz). The kit is made by G4FUF and is really quite a neat package which you start with the surface mount components:

Once all the SMD parts are on the board there are a number of inductors:

followed by a pair of relays and an rf connection or two:

So next is to perform a basic DC test and then install inside the FT-847...

Watch this space!

4m (70MHz) and Counting....

Following on from the mods I undertook on my FT-847 here:
http://g0mgx.blogspot.co.uk/2012/06/ft-847-that-i-have-here-includes-70mhz.html

I've bought and put up a 4M beam. I've not got it so it can be rotated, nor is it very high off the ground, but it's pointing to the SE and ready for those Es!

So, the house looks like this from the side:

So here you can see a 6M, 2M and now a 4M beam, a vertical for 2M, 70cm and 6M plus the centre of the Windom. The main HF antenna is on the back of the house.

My next project will be a 4M pre-amp for the FT-847 which I have already bought as a kit:

This kit is from Keith, G4FUF, he seems to be the font of all knowledge on the FT-847 and converting it for 4M. I'll post more about this when I make the kit and install it in the radio.

I've also started to think about WSPR on 4M and have just built a 60MHz local oscillator which I could use to mix with a 10MHz signal to get onto 70MHz. All just thoughts at the moment:

Cats not been helping much, as usual:

All good fun though, egh?

FT-847 on 4M or 70MHz

The FT-847 that I have here includes the 70MHz band when you sequence through using the band up and down button; it also excludes the more recently allocated 7.1MHz to 7.2MHz at the top end of 40M. The latter doesn't bother me too much.

The RF out on 70MHz is a mere 10W, and I have recently been reading about a mod to increase this safely.

The details of the mod have been published by G4FUF here:

http://www.70mhz.org/847mods.htm

The first step is to remove the outer casing by taking off the carry handle and other associated screws, then we need to confirm a number of jumper settings and then measure some test points:

this is to confirm that the on-board configuration is as it needs to be. The test points are in this area of the upper board:

Then the lower board needs to be moved out of the way, this is a simple task by removing 4 gold screws and flipping the board towards the front of the radio:

This provides access to the PA, but first the shield has to be removed:

 Then, finally, we have access to the PA:

Then a piece of ferrite needs introducing into the centre of L5006; this will bring the resonance down to below the 70MHz band.

****** IMPORTANT ******

It is essential that the correct type of core is used otherwise excessive heating may occur; you cant just use any piece of ferrite! The core needs to have a relatively low mu and should be a VHF/UHF type. The core from a TOKO S18, MC120 or MC122 are usable and are currently available from JabDog:
www.jabdog.com


****** EVEN MORE IMPORTANT *******

There's a better way:

http://g0mgx.blogspot.co.uk/2012/06/ft-847-pa-mod-theres-better-way.html

*************************


You can see the modified component right in the centre of the photo here:

Once this is complete, it will have initially made no difference at all!
We also need to remove the ALC mod that is still restricting the output on 70MHz, this is completed by snipping the green wire in the image below (this is the top board in the radio):

Now I have the desired 65W (ish) out on 70MHz. I've ordered a pre-amp kit to improve the radio on RX, I'll post more when it arrives.

Good though, egh?