Wednesday, 12 December 2018

Easy Rotator Control 4 and the Yaesu G450C Rotator.

For ages now I've been reaching across the bench keeping my finger pressed on the rotator controller switch when changing beam heading and I've finally got fed up with the agro of doing this when a PC based solution is available in the form of the Easy Rotator Controller (ERC) from schmidt-alba.

The ERC is small PCB consisting of relays and a ATmega micro controller to monitor the rotator feedback voltage and operate the relays taking on the role of the existing CW and CCW switches.

The controller is available in a number of configurations, I choose to purchase the Version 4 USB controller as most PC's today do not come with a built in serial port.

The controller is available as either a kit or prebuilt.   I  decided to get the kit form, as any respecting amateur would, for £79.47 including postage and packing which is a £20 pound saving on the prebuilt unit.

The kit comes in four packages consisting of a high quality USB cable, software CD, component bag and another bag with the PCB, DC power connector and some cable to wire the ERC up to your existing controller.

Contents of ERC kit package.

The component bag consists of all the components to be soldered onto the supplied PCB.

The supplied kit components.
PCB, DC power plug, cable and PCB standoffs.

The kit has very few parts as you would expect based around a ATMega 328P 8 Bit micro controller, a crystal for the processor clock some capacitors, a couple of diodes and chokes, a few resistors and a small 70cm x 60cm PCB plus the USB interface, relays and terminal blocks.

I started by first installing all the discrete components, IC holders and the USB interface board which took about half an hour to complete.

The completed board minus relays and terminals.

Once the above was completed I installed the rest of the components.

The completed board ready for the IC's to be fitted.

Once the board is completed you apply 12V DC to the unit and test that you get 12V and 5V at the test points located on the DC port side of the board assuming these pan out you insert the ICs and then start modifying the original rotator controller to take the ERC board.

With the easy bit completed the next job is to disassemble the Yaesu controller and do some metalworking.

Taking the Yaesu controller unit apart isn't a five minute job what you need to do is unplug the power cable from the front power switch and then pop out the cable clamp and remove the lead from the case, you next need to desolder the fuse holder from the transformer and remove holder from the chassis again this isn't easy as everything is covered in blue thread lock, next up remove the control cable 6 pin molex socket.    With all the cables removed you now need to remove screws holding the top instrumentation tray to the front and back panels, this is done to allow access to the nuts and bolts holding the mains transformer to the bottom of the chassis which again has blue lock thread, Yaesu really don't want this unit to fall apart. ;-)   With all the above removed you can now get on with marking the holes from the DC PWR and USB ports.

There's a handy sticky label template that comes with the ERC controller which is perfect for marking the hole placements.

The rear of the controller box with the holes cut for the DC power
and USB connector.

Now you can see from the above picture the holes didn't quite align horizontally and this was down to me being a wally and instead of adding a couple of millimetres to the template I did the opposite and removed a couple of millimetres instead, so had I carried out that operation successfully everything would have aligned.   I still ended up with yet another problem shown below.

ERC fitted within the original rotator controller.

If you look at where the PCB stand offs are in relationship to the case fixing holes in the chassis even though there is enough height clearance so that the screws do not foul on the underside of the PCB what I hadn't taken into account was the fact the case wraps around the chassis when screwed together, this meant I needed to mount the PCB using only the two PCB mounts towards the middle of the chassis.   Now this is in fact fine the board isn't being put under any stress though these mistakes are annoying no one will be able to see them.

The original rotator gubbins replaced and the ERC cables attached.

I then replaced the front panel, power supply and original controller board with this done I could strip some insulation off halfway along both the brown and white wires this is so the ERC can be placed in parallel to the rotator and Yaesu controller to measure the feedback voltage which keeps track of the beam heading.

The control button side of the controller. 

Now the tricky part is to connect the blue and black wires from the ERC controller on the original controller heading controls these switches already have a couple of quite thick gauge wires attached to them and attaching the new wires along with the originals is a bit of a pig but if you start with the switch nearest to the mains transformer it's not too bad.

With the ERC controller connected you can refit the outer case and reconnect the unit the rotator and plug the controller back into the mains and station DC power supply you can then move on to calibrating the unit.

On the software CD you'll find two pieces of software one to calibrate the unit and another to control the unit with.  

The calibration is a little bit more involved for the Yaesu G450C rotator in that you need to do an extended calibration.   This involves calibrating at more headings than would be normal.   The general gist of the procedure is to start the calibration software as shown below.

Calibration Software
Once you have set the controllers com port, which you find in the Windows device manager, you'll be able to read the ERC memory.   Next you need to set the rotator fully counter clockwise, using the Yaesu controller, once set to 0 degrees you can perform an extended calibration by using the "Extended 1" function which measures the rotator feedback voltage at 30 degrees intervals once each interval has been measured the software will tell you to advance to the next calibration point.  

A point to be aware of is make sure when you are setting the Yaesu controller that you look straight on to the Yaesu controller heading indicator otherwise you can calibrate to the wrong heading.  

Once the calibration has been completed close the calibration software and start the rotator control software shown below.

The control software supplied with the kit.
Once the rotator control software has started remember to set the com port and wait few moments for the software to connect.   Now click on a point on the compass and the rotator should start to turn to the position you selected and check the Yaesu controller agrees with the software, try this a few times to confirm the calibration if the calibration is off you'll need to repeat the calibration again.

Though the supplied software is ok it's very basic and in fact I replaced with PstRotator from YO3DMU it's an excellent piece of software and though you need to pay 20 Euro's for the licence it's a bargain and I wouldn't use anything else.  The software can set with presets for quick heading changes, you can open a map and click at any point and the beam moves to that head, the other nice feature if you live near the coast is have the beams turn into the wind when the wind speed exceeds a threshold of you choice.


This is one of those projects that starts off as a 'nice to have' which turns into 'how did I ever manage without it' I'm sure no one would regret adding the ERC to their rotator controller.

Wednesday, 3 October 2018

2m Antenna Update

After spending next to four weeks off the air due to the new antenna system suddenly going high VSWR 6:1 the guys, Dave and Fred, finally managed to get the system down for us to check where the fault lay typically when I test the VSWR before taking it down the fault had cleared on its own.

Originally the system gave a VSWR of 1.1:1 until it rained when it went high, now since that point it hasn't rained so I can only assume during the intervening period whatever had got damp had since dried out.

All the connectors looked dry with no indication of water ingress seen, the coupler was also bone dry.   The powabeams use an ABS moulding to fix the driven elements to the beam and this is glued shut during manufacture so it's impossible to open without destroying the moulding in the process.

We put more rubber sealant on around the Powabeam ABS moulding, the end caps on the coupler and around the N-Type sockets on the coupler as well I also wrapped self amalgamating tape around the ends and over the centre hole that gives access to the middle socket.

We then put the system back together with all joint resealed with amalgamating tape it now looks like it should take being dipped into the sea before it leaks but only time will tell.

The only modification we made was to make the quarter wave chokes as depicted on the Powabeam website originally we put the loop over the back of the beam which certainly worked however both Dave and I have Powabeams and switched the recommended way of creating the choke which we both agree seems to give a better response.

I used the system again in this weeks 2m UKAC and it worked flawlessly so fingers crossed it'll carry on working.

Again a big thanks to Dave M1DNJ and Fred for doing all the manual labour.

Tuesday, 18 September 2018

DCI-145-2H 2m Filter.

I recently swapped an unwanted Daiwa VSWR meter for a DCI-145-2H 4 pole bandpass filter for 2 metres.   I don't really need it however I have on the odd occasion thought it might help with some strong out of band signals that occasionally pop up so swapping an unwanted piece of equipment for a piece that might be useful I thought was a good deal.

DCI quote the following specification.

Centre Frequency : 145MHz
Band Width : 2MHz
SWR : < 1.3:1
Return Loss : >18dB

DCI measure the filter response at the following intervals.

135 MHz : -72.650 dB
140 MHz : -46.450 dB
145 MHz : -0.755   dB
150 MHz : -42.981 dB
155 MHz : -65.548 dB

Out of pure interest I thought I see what I measured the above as using the DG8SAQ VNWA.

Filter response etc measured with the VNWA.
As you can see the filter specifications for SWR, RL as described the only difference is with the filter skirt readings being slightly off but in quite good agreement with DCI which I'll assume used a slightly better VNA than the one I have. ;-)

Saturday, 8 September 2018

New 2m Antenna Is Finally Installed.

With the help of my nephew Fred and Dave M1DNJ I've finally got the two new Powabeam 9 ele CQM's installed, see my previous post for specifications.

Fred got the job of taking down the original system which consisted of a single 9 ele LFA from InnoAntenna this antenna has worked faultlessly and in fact I only switched to the CQM design due to weight, I don't have a tilt over mast so the stub needs to be lifted into place with the top beam as well as the coupler and 70cm beam by hand not a easy task while standing on a ladder, the LFA even survived being dropped into a hedge from 8m with the rotator and mast attached when the guys from MM0CUG took the antenna down before fitting it to the new mast.

The original 2m LFA with a 70cm 12 ele above.
The first thing to do was remove the original antennas Fred duly got on the steps and disconnected the antenna tails and loosened the rotator stub clamps.

Fred disconnecting feeder and loosening clamps
With antenna removed Fred G-Clamped the new rotator cage to the garden bench and fitted the rotator and thrust bearing which we both proceeded to align. 

Rotator, Thrust Bearing Fitted and Aligned. 
With the rotator and bearing completed Fred got on with the task of fitting all 18 parasitic elements as well as the driven elements to the booms ready for installation.

Fred with set square fitting the parasitics.

Dave M1DNJ and Fred along with Amber then got on with fitting the rotator cage including stub mast, top beam, power coupler and 70cm to the mast thank the gods Fred has good arm strength and a taste of heights.

Stub with top beam, 70cm beam and cage fitted.
Next up was fitting the bottom beam to the mast. 

Bottom beam being attached to stub.
And finally connecting up the bottom beam to the coupler and jobs a good un. 

Coupler connections all done.
And lastly fixing the cables to the mast.

All most done.
Hurrah the finished system finally raised.

The new system raised.
The system gives an VSWR of 1.1:1 @ 144.300MHz with a resistance of 45ohms and reactance of 2 ohms.  

I must give thanks to Dave M1DNJ, Fred and Amber putting up with me trying to run them over with the wheelchair while I fretted over various bits and pieces.   I've been told I'm quite OCD about my antennas. ;-))

UPDATE : 6th September 2018 --   Well the first hard rain since putting the antenna up and the SWR has shot up to 6:1 oh bother this means sadly I'll be off 2m for awhile until I can get the antennas down and workout where the water has got, I suspect the Powabeam driven element ABS moulded fixing block which I had heard can give issues I thought I had sealed it up with extra sealant but obviously not!

Friday, 10 August 2018

Kuhne Electronics IC7300 IF Transverter Mod Board - Update

I recently fitted the Kuhne IF transverter modification board and found I had some issues with it.

When I first fitted the board I had a strange pulse appear on receive when using the transverter I original put this down to having to much signal going from the transverter to the rig and so switched on the rigs attenuator to resolve the issue.   Now I didn't do this in a very scientific manner I just put the attenuation in on gut feeling.

Next I noticed when using my Wavenode power meter when I de-keyed the transmitter I had a 1.3W RF spike out of the transverter which resulted in a 200W spike from the linear.   After pulling the system apart in an effort to resolve the issue I discovered the cause was the Kuhne modification.

As I found the issue with the Wavenode was caused by the interface board I had another look at the RF pulse I was seeing without the rigs attenuator turned on.   I tuned in the GB3VHF beacon which appeared as S9 on the S meter while using the transverter with the combiner and then switch back to IF interface where GB3VHF stayed at S9 without the rigs attenuator turn on however the pulse was present again so I again switched the attenuator back on resulting in the beacon losing an S point but the pulse had disappeared.

I did a quick search on the internet and found on the IC7300 io.groups reflector a PDF documenting a modification to do with instabilities found with the IC7300 power amplifier when the Kuhne board was disengaged and carried out the modifications which made no difference to my problems which in all honestly wasn't surprising.

I've now decided to remove the modification and go back to the combiner and attenuator method of driving the transverter which was far more stable and had no issues.

Another observation is the fact I kept seeing some IM products in the adjacent 3kHz from where I was operating from which I just couldn't get rid of it wasn't bad about -25dB in relation to output and wasn't always present but with the modification removed it vanished completely to the point where any IM product is now at least -35db at worst.

Wednesday, 18 July 2018

2m Antenna Upgrade.

I current have a single 9 Ele LFA from G0KSC and though I have no complaints regarding the antenna I'm now at a stage where the only place I can make a sensible improvement in my 2m setup is to replace the antenna.  

I would have liked, probably like most amateurs, to have more the space to put in an array of four 9 element antennas however this isn't practical on my property.  

Now I would like to give EME ago at some point but I don't have elevation available so this put me in a quandary how to improve the system why still allowing myself a little bit of freedom to still carry out a few EME and Meteor Scatter communications when conditions allowed but also give me a better score in the RSGB 2m UKAC as well as general tropo, E's etc QSO's.

I had a chat with few local amateurs I discovered one of them M1DNJ has a similar setup to myself but has a better antenna and mast setup after numerous discussions with David I decided I go with a 9 Element G4CQM design made by Powabeam antennas a CQM9C4 as the performance looked to be about the same as the LFA but with the bonus it's lighter in weight so would make lifting on the mast much easier to accomplish as I don't have a tilt over.   I decided to go with a of two stacked Yagi's.

Richard at Powabeam has published the specifications for a single Yagi as well as a quad array but I couldn't find the specifications for a stack of two so decided to run the simulations myself.  I'm not going to go through all the figures and configuration that can be deduced from the Powabeam website and the images below.

4nec2 - 3D - 2 x CQM9C4

Total Field - 2 Stacked CQM9C4
Horizontal Plane - 2 Stacked CQM9C4

Verical Plane - 2 Stacked CQM9C4

TANT - CQM9C4 - 2 x Stacked Array.

Tuesday, 17 July 2018

2m quarter wave coupler

I'm just about to update the 2m antenna system moving from a single 9 element LFA by G0KSC to two 9 element CQM9C4 Powabeams stacked.   To stack the two yagi's you need a coupler to join to the them together.

A quick search on the net I came across two ways of doing this one based on using coax and the other using aluminium box section with a 15mm copper pipe forming a square piece of coax.

You can buy a ready made coupler but I so happened to have a piece of aluminium box section of the correct length as well as a piece of 15mm copper pipe and three N-Type laying around so I though I'd see if I could save myself £70 and build one myself.  

The way to work the dimensions you use a piece of software called appcad this will allow you to calculate the length of the inner copper pipe which turns out to be 520mm for my size of aluminium box I followed the design for the two port coupler from DG7YBN's website.

What I found was the length isn't particularly critical but the distance between the copper tube running thought the box section is my ali box has an inner dimension of 24mm and as mentioned before the copper pipe is 15mm which requires a spacing of 4.5mm to obtain this I wound insulation tape around a screwdriver until it conformed to the 4.5mm and then used this to centralise the tube in the section.  

An afternoon with the hacksaw and drill press I had the basic coupler built and I ten minutes with a 100W soldering iron had the copper tube soldered to the N-Type sockets.

I tested the coupler on the VNA and got a return loss of around 25dB and a VSWR of 1.1:1 which is near enough so I'm a happy bunny.

I'm still awaiting the materials to build the powabeam yagi's but I'll post again with the build and how they went together.

2m Quarter Wave Coupler Results @ 144.3MHz

Sunday, 8 July 2018

Vine 6M4DX

A few weeks ago a message came up on my radio club message board offering a Vine 6M4DX 4 element 6m beam for sale, now I've not worked much on 6m and in truth I don't tend to working on anything other than 2m and 70cm but the antenna was cheap £40 pounds so I emailed the seller Colin and bought the beam.  

Now I wasn't holding out for much as it's a secondhand beam but upon picking the beam up I was pleasantly surprised as the beam came in the original box and been taken down and packed away with the bits marked and fitting placed into plastic bags, happy days.

I thought that the beam was missing any instructions and I was unsure of how to fit the hairpin match so emailed the manufacturer which I discovered had ceased trading in 2016 but there website is still present with an email so I emailed them not expecting a response.    To my utter surprise Ron at the aforementioned company emailed me back with 12 hours with all the specs and fitting instructions  which I thought was amazing and I only wish some companies that are trading could match this defunct companies customer support. 

The Vine 6M4DX has the following radiation pattern. 

6M4DX Radiation Pattern
I also managed to pick up for free an older rotator and controller so this would get me QRV 6m for next to nothing from a friend of mine so even more happy days.

Here's my nephew Fred and my mate Mal G1NOX
baking in the sun putting the beam together. 
It took Fred and Mal about 4 hours to construct the beam and get it up on the chimney.

The completed beam up on the chimney stack

When I tested the VSWR the beam gave less than 1.5:1 across the whole 6m band which is fine for my purposes.  

Now typically once the beam was up the rotator controller died within 5 minutes, oh bother so I need to fix that before I can the beam a full work out.  But all in all a great bit of kit for peanuts and gets me active on 6m.

Iceni 70cm Transverter from G4DDK - Part 4

I finally got around to finishing the Iceni transverter as depicted below.

Finished Iceni Transverter
The unit is configured to give 17dBm for 0dBm of drive which is then reduced a bit more so that the 70cm PA gives 30dBm which is great for the BNOS 432-1-50 PA I have.

All in all a great project which I'm extremely happy with.

Sunday, 10 June 2018

Iceni 70cm Transverter from G4DDK - Part 3

I've finally started on finishing the Iceni transverter I've used the same case layout as the Anglian.

Front Panel

PA Heatsink

Rear Panel

Internal Layout
I've a bit more room inside the Iceni as I've used a Tohtsu CX-120A relay in place of the old Pye relay I had available for the Anglian which is a pity as the Pye was a nicer relay and had better isolation in comparison.  

Next up on the list is to start wiring it all up but least the hard bit is now done as I hate enclosure fabrication. 

I fitted a Kuhne QH30A heater to the Iceni' crystal so it'll need to be realigned but I'll wait until I've made up the LO inject cable and socket as the extra capacitance knock the frequency off by about a 100Hz.

Saturday, 2 June 2018

A blast from the past my RSGB membership certificate.

I was tidying up the shack today and came across my original RSGB membership certificate dated the 1st of July 1983 a couple of days after my 12th birthday.

At the time I was very happy to receive my RS number 84784.

If my memory is correct I had to get a recommendation from a current member to join and amateur who lived across the road from me at the time filled the form out for me.

Amazingly it only took another 33 years to obtain my foundation licence and 34 years to gain the full licence, oh well better late than never. ;-)

My RSGB membership certificate issued when I twelve.

Thursday, 24 May 2018

Anglian 3L 2m Transverter from G4DDK - Part 3

Finally ready to try driving the Anglian from the rig I needed to connect it up.   Originally I was going to use the Kuhne transverter interface for the IC7300 but after some consideration decided to actually use a combiner along with a 20dB 30W attenuator though there is obviously a loss incurred in the RX path switching between the Anglian and Iceni will however be easier.

I bought the attenuator from eBay from for the bargain price of £25 these things are now cheap as chips from China and when I tested the unit with a VNA gave 20dB of attenuation at 50ohms from 1MHz to 600MHz which is as far as I bothered but the device will apparently work up to 3GHz but I couldn't vouch for that.

The combiner is a Merrimac 2 way 0 deg inductive unit from which cost just over £40 pounds which is cheaper than the mini-circuits equivalent unit and more than up to the job.

Merrimac combiner with 20dB 30W attenuator
With my Yaesu FT991 set to give 40dBm of drive which  will provide 20dBm to the Anglian once passed through the attenuator I measured and output as 39dBm so some additional attenuation is required between the Anglian and the PA.

With an extra 16dB of attenuation placed between the Anglian and the PA I measured just under 37dBm out which is good enough to drive my little Microset SR100 amplifier.   

I couldn't measure the 2nd and 3rd harmonic product with my equipment but I did a quick check with my SDR and I couldn't see anything on the SDR# waterfall.

Anglian 3L 2m Transverter from G4DDK - Part 2

Well blow me I went to align the TX chain on the Anglian and low and behold no output, this turned out to be IC7 being grounded once this was resolved the TX chain worked as expected giving out 20dBm for 0dBm of drive.

I've had all manner of issues with this Anglian 99% caused by the builder.   I've come to the conclusion that solder paste though easy to use can cause issues if a little too much is used.   I never had this issue with the Iceni however did spend more time cleaning the board and that seems to have paid dividends with the Iceni, so mental note to self don't skimp on making sure any solder paste residue is removed.

I also had a replacement QH40A heater from Kuhne arrive which I duly fitted and low and behold the exact same issue in that as the heater heats up the frequency slowly drifts up to the correct frequency and then suddenly drop by around 500Hz and then slow drifts back up again before repeating.   I may ask Sam if he has another crystal I could buy just to experiment with however as I have a GPSDO there is no real need, even without the heater after a 10 minute warm up period the unit only drifts by a few cycles.

Sam also does an 8W Class AB amplifier which has good linearity when limited to 5W PEP for the Anglian which is simple to build.  The unit draws around 1.5A with a supply voltage of 12.8V.

Sadly I omitted to take any photographs of the PA but you can almost see the unit in the pictures of the completed transverter below.

The last thing to do is plug it all in and test the output from the PA doesn't exceed 5W PEP.

Front Panel
Rear Panel
The inside.

Thursday, 17 May 2018

Anglian 3L 2m Transverter from G4DDK - Part 1

With the success of building the Iceni transverter from G4DDK I decided I'd also purchase and build Sam's Anglian 3L 2m transverter as well which I'd heard glowing reviews for.

The Anglian 3L is of a similar design as the Iceni using much of the same circuitry and form factor.

Here's a list of specifications from Sam's website.

Parameter Performance
RX noise figure 1.6-1.8dB
RX gain 25-26dB
RX IIP3 Better than 0dBm
TX gain 20dB (35dB with optional TX IF stage)
28MHz Drive required for +20dBm 144MHz output 0dBm (-15dBm with IF amplifier)
Power output (Saturated/P1dB) +22/+20dBm
Harmonic output (2nd/3rd/higher) at saturation/td> -40dBc/-50dBc/<-60dBc
Image frequency output suppression <70dBc
LO suppression <70dBc
Transmit sideband noise Better than -140dBc/Hz at 20kHz offset

The kit went together fairly easily but you must double check both the parts list and circuit diagram as well as the assembly documents to get it right.

The Anglian 3L uses the same PCB as the original Anglian 3 with either some components changed, added or even removed so you can't just follow the silkscreen print on the board.

I found a few omissions and errors with the documents but Sam is always willing to aid assistance and be told of mistakes so he can fix them and in fact has a searchable PDF if you ask him.

The completed module can be seen below, sadly I omitted to take any photographs during the build.

Anglian 3L after much fault finding.

On first power up I found there was nearly 750mA of current draw instead on the 250mA the build document said there would be.  I removed both TR4 and TR5 from the unit so that both the receive and transmit chains would be isolated from the rest of the circuit and plugged the unit back in and measured a current draw of 70mA with a 12V supply which is in agreement with what Sam said the unit would draw.

Next I replaced TR4 and again measured the current draw which has now returned to the 750mA I originally measured which indicated the error was in the receive chain so I removed TR4 again and then replaced TR5 and measured the current draw again which was now 80mA proving the error was in fact in the receive chain, I then refitted TR4 again.

Knowing the problem was in the receive chain I slowly isolated each part of the circuit until I ended up with only the PSA4-5043 MMIC IC3 left in the circuit, sadly removing it without a reflow hot air gun is a pain in the backside and in fact I ended up destroying it so it was back to Sam to ask for a replacement which he kindly sent out.   I couldn't see any shorted tracks under the microscope and I can only assume that I had a short on the underneath of the IC3 which I couldn't see, anyway with the replacement fitted the unit now had a current draw of 260mA hooray!

With the unit now seeming to be working the next thing to do was to set the oscillator to 116MHz with an output of around 20dBm, well blow me there was no output from the oscillator a quick check with the voltmeter showed there was no voltage on the collector of TR2.  After a bit of head scratching I realised R13 was missing from the board,  the silkscreen was marked L8 and not R13 so it got omitted during the initial construction, I said double check the circuit against the silkscreen as there is a few of these changes that are easy to miss if you're not careful.

I could not get the oscillator on frequency it was also over 200Hz off and had a very sharp adjustment so I ended up removing L27 to give a little leeway in the adjustment and managed to get the oscillator bang on frequency.

On a side note I had a Kuhne QH40A heater attached to the crystal.  The heater keeps a constant temperature of 40C, though the crystal is cut for a temperature inflexion point of 25C, now this worked great with the Iceni but caused horrendous drift on the Anglian and the only reason I can think of the heater was actually heating above 40C so I've removed it for the time being.

Sam recommends the QH40A with both the Iceni and Anglian and it worked really well with the Iceni but if you suffer frequency drift with the QH40A fitted don't assume it's the Anglian drifting but irregularities with the heater instead.  I did have a word with Kuhne regards reducing the voltage the heater to see if that would lower the temperature but they say it won't make a difference so I need to order another.

Next thing to do is align the receiver this involves adjusting L14, 15, 16 and 20 using the coilcraft trimming tool included with the kit.   Now the build document said to set a receiver to 29MHz and connect the Anglian then try and equalise the noise across 28 - 30 MHz by adjust the L14 - 16.   I found to my horror that I appeared to have no receive output from the receiver, bangs head on wall, bother!

To workout where the fault  I injected a 144MHz signal into the Anglian's RF_RX port and with an oscilloscope 1x probe connected an RTL2823U dongle and SDR# set to 144MHz traced the signal through to the mixer I then switched the SDR# frequency to 29MHz and traced though to the LPF where I discovered yet another short this time on C24 I removed and refitted it which resolved the problem.

Even though the receive chain was now fully operational I still couldn't hear an difference in noise level when adjusting the inductors and in the end came to the conclusion that either my hearing is a little dodgy, the fact I couldn't turn the AGC off on the Yaesu FT991 receiver I have or even both.

To get over this problem I again connected a signal generator to the RF_RX port injected a 144MHz into the Anglian I then adjusted the coils for maximum signal which I then repeated at 143 and 145MHz until I had a equalised the read signals across the band.   The assembly document said the inductors would probably be a few turns below the top of the can but you can see in the picture below mine didn't end up like that at all.

The three inductors in line are for the RX alignment.
I maybe able to redo the alignment once I have the Icom 7300 out of the box but until then I'll leave the adjustment as is.

Just to be certain everything up to this point appeared to be working I connected an antenna to the Anglian and tuned in the GB3VHF beacon on 144.4285MHz and ran WSJT up to make sure the continuous tone the beacon transmits between the JT65B and Morse sequences fell on the 1.5kHz mark on water fall and I was pleasantly surprised to see it was with a few cycles of where it should have been, though bear in mind I did use a GPSDO due there being no heater currently fitted so it should have been pretty much spot on.

The next thing to do is to the align the transmit chain and write part two. ;-)

Tuesday, 15 May 2018

Cheap Chinese 70cm 100W Linear Amplifier - Part 3

I've had quite a bit on lately finishing the Iceni and Anglian transverters by G4DDK but I managed to find some time to do a bit more to the 70cm PA.

Using the same setup as the last time I tested the harmonic output I got the following results.

2nd Harmonic was at -38dBc originally measured at -40dBc

and the

3rd Harmonic was at -68dBc originally measured at -53dBc

So not the big improvement I was hoping for and in fact 2dB worse for the second harmonic.

I tried running the unit with a lower drive giving an output of 50W and in fact the 2nd harmonic got worse as well as at various other lower drive levels.

I've yet to decide how to rectify that small problem I could use a small mini-kits LPF from Australia or the cheap way a 1/4 wave stub notch filter cut for the 2nd harmonic.

The other thing I've discovered is to not pick the PA up after running a CW test as the heatsink gets mighty hot. ;-)

Monday, 7 May 2018

M0CVO HFC-3015V Vertical Short Antenna for 40m - 10m Update

I finally got the HFC-3015V installed today, apparently the hottest day this year so far,  I tried installing the antenna without placing any wood within the PVC pipe where it bolts to the mast and found it to be impossible to fix securely without it crushing the tube so it definitely requires the extra wood inside.

The installation instructions say to fit with a counterpoise if going to used on 17, 20 and 40m bands however doesn't give any recommendations on length or amount of counterpoises required.   I ended up fitting two, approximately 4 metres long.

The antenna is fitted with an LDG RT-100 ATU on a short 0.5m RG58 patch lead and feed back to the shack with some Ecoflex 10 I had spare.

I've not had a good chance to try the antenna out yet but checked to see how it would match, on 20m it gave an VSWR of 1.6:1 which wasn't too awful however on 40m I got a VSWR of 1:1 which was quite impressive now this doesn't of course mean it's going to radiate well but least it's matching on the two bands I use the most.  

More to come once I've used the beast for awhile.

Saturday, 28 April 2018

M0CVO HFC-3015V Vertical Short Antenna for 40m - 10m

Recently I had a new mast fitted for my 2m and 70cm antenna's and in the process lost the centre support for my HF doublet and needed something to replace it that wasn't too intrusive.  

I was toying with another centre feed antenna of some kind however I have a particularly small garden with no trees or other readily available supports for antenna's and no easy to access to the ground due to the garden being covered in decking I decided a vertical that didn't need a ground spike was probably the way to go.   Being disabled I also wanted something I didn't have to make myself, sadly I'm past that point in life.

I found the HFC-3015V via Google it's a 1.7m tall, designed for flat dwellers and people with small gardens and according to the website will tune with the internal ATU fitted in most modern rigs on the 30 15, 12 and 10m bands as well as 40, 20 and 17m with an external ATU and some counterpoises and handles up to 300W, I never use more than a 100W on HF so more than adequate.

The antenna is made from 40mm PVC-U, polypropylene, waste pipe by the looks of it and has a wall thickness of 2.5mm.  

A fairly thick piece of wire spirals up the pipe from the balun, could be an unun,  to about half way along and then wound into a coil of approximately 30 turns and then again spiralled to the last loading coil which is about 90 turns.

Now you're meant to fix this to a mast using standard mast clamps as depicted below.

Style of clamp supplied with the Antenna.

However I'll use two slightly different clamps which I feel will hold the antenna far more securely, depicted below.

New style clamp.
I'm also going to slide a piece of wood dowel inside the pipe so that the clamps can be tightened without fear of deforming the PVC.

I plan to fix the antenna to the chimney stack using a standard lashing kit, which is already present, on a section of 48mm scaffold pole which is again already fitted.

The website says the antenna is IP56 rated and may only need some self amalgamating tape on the SO-239 feed point.   You can see in the picture below the balun, though it looks to be well made I still think I'll put some more sealant around the box seal as well as rubber coat the antenna and counterpoise connections as living by the sea tends to destroy all type of metal fixing very quickly.  I would have liked having a look inside however the screws felt extremely tight remove.

HFC_3015V Balun
I'll use an LDG RT-100 remote ATU with the unit and fix that to the same supporting mast as the antenna.    I'll also fix three or four 1.5m counterpoises to aid with matching on 40, 20 and 17m.

I'm still not convinced that the antenna will work that well, the M0CVO website doesn't hold any more details other than what bands it'll work on,  but we'll have to wait and see but for 70 GBP I thought it was worth a punt.  

I did think about modelling the antenna in mmana-gal but shock a little at the prospect of adding all the wires for the spirals and loading coils.

Anyway as is always the way with these things as soon as the antenna arrived the MetOffice forecast rain for two weeks, typical!  Once erected and on air I'll let you know how I get on and whether or not I thought it was worth the asking price.  

Tuesday, 27 March 2018

New Antenna Mast from MM0CUG

My original antenna mast consisted of a 21 foot scaffold pole attached the side of the bungalow via T&K brackets however over winter I noticed that this was causing some damage to the brickwork and so I decided to replace it with a free standing mast from MM0CUG in Aberdeen.

The new mast is 8.5 metres tall however 1 metre is buried in a large block of concrete so 7.5 metres in total and is approximately 1 metre taller than the original scaffold pole.   It's a telescope design raised and lowered by a heavy duty winch triggered by a remote control, so no going outside in bad weather to raise and lower it.

The winch is powered by a battery which is a kept topped up using a 2.5W solar panel.

The guys from MM0CUG kindly took down the scaffold pole for me and moved my antenna to the new mast all within a day.   I still need to do a little tidying up regards cable routing etc ... but overall a stress free project.

Below is a few pictures taken on the day again from the luxury of my living room.

The initial hole cut in the decking
Digging a hole
Mast stub concreted and mast inserted
Getting ready to attach the rotator and antenna's
The new mast in the lowered position.

The mast extended.