Antenna considerations

Right, if you’re going to do it properly you need to have a sensible antenna otherwise you’re wasting your time.

At present I’m playing with my 30 meter 1/4 wavelength counterpoise antenna, which was lashed up firstly for my WSPR receiver project and has worked well in that role and with my Ultimate3 QRSS beacon.

I need a multi waveband antenna to do the SoftRock justice, so I set about working out the pros and cons of planting a permanent, fit for purpose antenna on the house.

For a long time I’ve been keen to explore the idea of Stealth Antenna’s after getting hold of a copy of the RSGB book by the same name. For a residential property it certainly widens the mind to ways of erecting an antenna for radio work without attracting undue attention.

My brief is for a multiband, discrete or stealth antenna for QRP work, maximum 5W at present.

After lots of research I plumped for the idea of a long wire covering 40m to 10m. The reasoning for this was it’s cheap, something I could make myself and could conceal in a variety of locations either inside, outside or alongside the house.

I was just about to embark on the build when I realised how much it was going to cost me to source the necessary components and hardware to build the thing and realised I was being silly. The combined cost of the ferrite ring and waterproof enclosure for the 9:1 transformer alone was 2/3 the cost of a complete antenna system, built, tested and supplied.

Now as hardcore as I want to be, at some point common sense steps in!

My weapon of choice was a Model 728HFA limited space antenna from Alton Antenna Arrays.

I was fortunate enough to meet Mike Parkin (G0JMI) back in the summer when I had all of 3 weeks knowledge and was about to take my Foundation Licence exam. Mike gave a lecture on his Mini Beam antennas and he absolutely blew my mind. He made a potentially complicated topic so easy to understand it was captivating and I was able to hoover up a tiny fraction of his knowledge when I got chance to speak with him later.

Mike has made the 728HFA as a special with an extended length of feeder to allow me to test various cable routing options before finalising the fix.

At the moment all my options revolve around sighting the antenna to the rear aspect of the house / garden

Screenshot 2014-11-30 18.47.08

Option 1 – route the antenna beneath the fascia and guttering, feeding the co-ax into the shack/man cave with other pre-existing cable runs on the back wall of the house

Option 2 – run the antenna from the house to a purpose built mast at the end of the garden. The antenna will be parallel to and 2.5m above a boundary fence to adjacent scrub land

Option 3 – run the antenna from the house, immediately outside the window of the shack room/man cave diagonally across the garden to the antenna mast at the end of the garden

Option 4 – loft fit


Option 1

PRO’s – it’s a semi covert fit avoiding undue attention and the antenna is sheltered to a degree from the elements

CON’s – relatively long feeder run, potential building effect / ground effect from the building

Option 2

PRO’s – there will be less ground effect / building effect on the antenna as it will be suspended in free space, rather than against a brick structure as in 1)

CON’s – despite the similarity to a washing line (and there’s plenty of those around) it’s a more obvious placement, added cost of erecting an antenna mast, I have no control over the vegetation to the west of building and although recently cut back by the owners it has the potential to grow into and over my antenna causing it damage

Option 3

PRO’s – there will be less ground effect / building effect on the antenna as it will be suspended in free space, rather than against to a brick structure as in 1), the deployment is completely within my boundary and won’t be subject to extraneous vegetation action, shortest feeder run of the 3 options

CON’s –  like option 2 it’s more obvious, requires a mast, potentially impacts more on the regular use of the garden

Option 4

PRO’s – a true stealth fit, the antenna is inside the house and protected from the weather

CON’s – I don’t have an uninterrupted run within the loft space to accommodate the antenna without removing some brickwork, there’s already a whole host of electrical and data cables snacking their way around the loft space so the potential for interference is greater, I’d need to punch a hole through the ceiling to run the feeder to the radio as I don’t have any risers or the ability to lift floors to route the cable. Admittedly conduit could be fitted, but there’s the inherent grief and the need to decorate/patch afterwards.

So with that lot in mind we’ll be going with Option 1 in the first instance. The antenna should be here sometime next week and with decent weather should be fitted relatively quickly.


MFJ-971 portable ATU modification

Unlike the posts of the past few days, which have been sat as drafts for several weeks and I’ve just tidied up and pressed send, today’s offering is hot off the press.

Several months ago the guru suggested investing in a portable ATU capable of QRP work, specifically the MFJ-971.


After waiting patiently for a few weeks, one popped up on eBay and I managed to get it for less than 50% of a new one, so happy days.

Then he hit me with the “you’ll need to mod it” line. What? Why? How?

No worries, a very kind sole, also playing in the “share the knowledge game” had been there before and had posted all that needed to be known here.

For my work, all I need at the moment is the bypass switch.

So today, faced with the prospect of more episodes of The Blacklist (which is very good watching) I made the conscious effort to be both practical and creative and donned multiple layers and ventured out into the garage.

I’m not saying anything, but there’s more chance of seeing Monty and Mabel in our garden today than in a John Lewis store! It’s freezing.

Now, when this thing arrived it had obviously been loved and looked after by it’s previous owner. It arrived in it’s original packaging which is huge, wrapped in a protective film. And now I was about to set to work on it? It didn’t seem right.

When I sprung the case, the whole thing smelt of a solidly built item designed by people who care about all things radio and want it to last. It could probably withstand a nuclear war!

The fact the manual consists of 3 pages of letter sized paper typed on a typewriter in Courier font, single line spaced with no diagrams shows these are the kind of people who will shoot you without hesitation for blaspheming at anything radio related.

Forwards and onwards! My biggest worry was drilling the case as it’s a nice unit and a drill slip would have pained me for ever and a day. Thankfully that went without a hitch and the DPDT switch was installed.



With the unit in front of me, the blog notes from M0UKD made a lot more sense.  The one thing I was warned of, was the need for the biggest soldering iron tip available. Advice well worth every penny as the wires in this thing just suck the heat up. I tried to desolder the antenna capacitor and transmitter capacitor leads but gave up and gently trimmed them in the end. It’s worth cleaning up the attachment points as the flux or resin from the manufacturing process didn’t give the easiest surface to work with.

I soldered four 3″ fly leads to my switch and soldiered on. In about 15 minutes, all done. A quick whip round with the DVM to make sure everything was where it should be and we were finished.



And now, with the case back on its ready for action. As others have commented, it’s a shame the bypass switch isn’t there as a factory fit, but like most things in life, you can’t have everything.

Besides, there’s fun to be had taking things apart and making them do things they were’t designed to do!


Remote Control

The underlying theme of this project, as I’ve said before, is remote access or remote control of the radio.

One thing that was bugging me was the physical power supply to the SoftRock. Admittedly it’s only a 12v supply but I wanted a way of flicking the switch without having to physically visit the rig each time, which is what I’m currently having to do. Equally, I’ve seen enough devices that are left plugged in permanently go pop when their life sustaining voltage is removed. That can be an expensive one, trust me!

What we need is a way to remotely switch the radio PSU and anything else that needs it now or in the future.

Enter the Denkovi USB 4 Relay Board


Denkovi do a huge range of automation products for home and industry, their site’s worth a look at just for the potential! I plumped for a 4 relay USB variant due to

a/ cost – at $20 you can’t go wrong

b/ 4 relays – at this size the board is powered off of the USB cable which carries the signals to it, reducing the need for yet another 230v wall wart cluttering the place up

c/ size – it’s tiny!

d/ USB – I strongly considered IP control BUT the radio’s on only when the attached computer is on plus IP is a lot of money. Fun but expensive!


The nice people in Bulgaria had it with me within a couple of days and sent links for all the necessary software. Be warned, you get nothing with it so if you need PSUs, cables etc. you need to order at the time, but not a problem as this little thing needs no external power and I’ve got enough USB cables laying around to knit a festive jumper.

Anyway, when plugged into a Windows machine, Windows does it’s thing and installs all the necessary drivers. The device appears on a virtual serial Comm Port and is ready to go.

Denkovi do a whole host of control applications for various platforms and have made them openly available.

The windows front end provides a nice graphical package which allows you to toggle the relays on and off to your hearts content at all sorts of calendar and timer controlled flags. If you’re really, really bored you can use this to get the relays to click out your favourite TV theme tune . . . . apparently.

Screenshot 2014-11-26 14.14.31


It’s a great package to play with but I wanted a simple way of toggling the power on and off.

Denkovi provide a command line tool which is Java based that provides other options.

With the correct RTE or SDK installed for your OS version, it’s as simple as starting up a command prompt and issuing the command –

java -jar DenkoviRelayCommandLineTool.jar list

lists the attached devices and provides the device identifier to allow you to send commands to individual relays on that board

java -jar DenkoviRelayCommandLineTool.jar DAE0006K 4 2 1

equates to “4” relays, “2” relay #2, “1” on

java -jar DenkoviRelayCommandLineTool.jar DAE0006K 4 2 0

equates to “4” relays, “2” relay #2, “1” off

There are countless other permutations and combinations but that’s all we need here.


It gets better. By creating a shortcut in windows and pasting that command line into the shortcut you get an icon which when you double click, executes the command.

Create one for on and one for off and you’re done . . . . . nearly.

Screenshot 2014-11-26 10.14.31


If you right click on a shortcut  which runs a command line executable you get some extra tabs which control the shape, size, location and colour of the ensuing shell which pops up when the command runs.

If you change the background colour of the screen to green for the Radio ON shortcut and red for the Radio OFF shortcut, you get a nice coloured flag pop up as visual confirmation that the relay is in the state you want it to be.

Screenshot 2014-11-26 14.16.55


Note – if you run the Windows DRM package at any point it polls the board and resets all the relays when it connects. If you’ve got stuff switched on from command lines or shortcuts and then do that, everything will just die! Word of warning in case you’ve got something vital or valuable dangling on an electromagnetically controlled latch when this happens

SoftRock External LPF for 40m operation

Now as time marches on we’re getting closer and closer to the point at which I won’t be sitting here just listening to everyone else having all the fun!

Once the antenna conundrum is sorted, it’s only a cable connection away to transmitting, which is why a little advance planning is needed.

The SoftRock needs an external low pass filter for 40m operation and the components to build one are shipped with the kit, which is half the battle won.

The topic is discussed on the SoftRock group and there’s a page in the constructors notes which, after a bit of internet rummaging, I found.

To make life easy the key piece is reproduced here, so I don’t have to go looking for it again when I’ve got a hot soldering iron in one hand and capacitors in the other.


Screenshot 2014-11-26 13.37.30


My next quest was some sort of enclosure to put this tiny device into to keep it mechanically safe. God knows how I found this site but Yowzer!

Every conceivable question answered in one! All connections for the antenna and to the radio secured to an aluminium chassis and solidly built!

Is it silly to get emotional over an inanimate object? Don’t even answer that one!


The good people at Digikey stock these

Now this is the really impressive bit. From clicking “purchase” to the man from UPS delivering this to the door took less than 36 hours. This is for an item that was US stock!

Next trick is to lash the filter up and get it plumbed into the enclosure, but that’s for another day.


RemAud Server and elevated Tasks to overcome Microsoft UAC

After fine tuning VAC so the audio from the radio is available to Fldigi or whatever the chosen application is to decode digi-mode transmissions, there is still a need to be able to hear what is going on.

I’ve had the SoftRock tuned to middle eastern AM voice transmissions which is a good way of testing various functions of the rig. Equally, when trying to identify the transmission mode be it CW (morse), PSK, RTTY although you eventually learn the characteristic shapes of each within the sometimes very messy waterfall, each mode has a distinct audio tone and being able to hear it is a massive help.

Now remembering that all our audio is whizzing around on the virtual audio bus, you need a way to tap into it and turn it back into something you can hear through the speakers of whatever device you are accessing the radio from.

Enter RemAud

Screenshot 2014-11-26 13.12.11

Again, for a free piece of software it provides a fantastic feature which solves the problem nicely.

The server element is installed at the point of origin for the audio, in our case the Radio-Box where VAC has our audio.

The client element is installed on the device(s) you wish to access that audio on.

Tell the server what it’s audio input is, that being VAC, create a username and password and that’s it.

On the client side, give it the IP address of the RemAud server, put in your username and password and press go.

Now remember, any audio that’s being streamed isn’t going to be as true to the original source due to network latency and so forth, but once again, for free it does the job nicely.


After playing with things for a few days I had a few issues with RemAud server, which can become unstable if something crashes out in the background. The result is extremely choppy audio on the client end.

The only solution is a reboot of the server and client machines. Not ideal but it fixes the problem if experienced.

Having double checked everything by tuning to an AM voice broadcast signal I’m happy everything’s as good as it can be. When using a Cat-5 link to my laptop everything’s crystal clear. There is a degree of latency when using a WiFi connection but then it’s only a 2.4GHz 802.11g connection and there’s a hell of a lot of BT and Sky boxes in the neighbourhood banging out all sorts of signals all over the spectrum which are getting in the way.

The solution would be to shift to a 5GHz 802.11n wireless network. At the minute my laptop doesn’t have the necessary wireless card to support this standard and it can’t be retro fitted. New laptop time!

The Wireless Acces Point solution of choice would be the XClaim Xi-1 providing 300mbps for $89

As an interim measure I’ve dug out an old Edimax WAP and set it up with a dedicated SSID that is only used for remote radio access and have shifted the broadcast frequency as far away from anything else on the spectrum. Far from ideal but it’ll do for the minute.


Anyway, we digress! I’ve been having a problem with Microsoft wanting to take over the world and prevent applications running without UAC stepping in and wanting verification of the action.

You know exactly what I mean don’t you?


This was happening every time I was starting RemAud on the Radio-Box. Now fully understanding what UAC does, I know why it steps in BUT what I want to run on my machine is a trusted process and I want it to run without UAC stepping in every time and if possible from machine start up so that on remote access you don’t have to go looking to start it, it’s already there.

Strangely, this becomes a bigger issue over VNC because on occasions the screen formatting gets screwed up and you can’t select Yes or close the UAC dialogue box to try again.

I was hoping that you could create a “whitelist” for UAC but that’s not possible. Extensive use of Google came up with a range of solutions, very few that worked I must stress! I don’t want any 3rd party programs on the Radio-Box as “bloatware” is an issue for me. Call it OCD if you want, but I want neat and streamlined to ensure maximum bang for my (someone else’s!) buck!

I used option number 4 on the following post –

Other similar solutions are available –

I’ve placed my shortcut in the Windows 7 startup folder so when the Radio-Box boots RemAud is running instantly and in the background.

Accessing Radio-Box via VNC

The main drive has been to getting this radio rig to the point that it’s fully functional over a remote VNC link, rather than having to be bolted to one location to use.

One of the key features to get running properly was the VNC access and again, what was assumed to be straight forward, threw up a few challenges.

One thing I have learnt is that not all VNC packages are made equally! For a long time I’ve used and been more than happy with TightVNC. However, having thought that it would be the solution for remotely accessing SDRConsole on the radio server left me doubting.

It really struggled with screen resolutions and anything graphical. Bearing in mind the waterfall in SDRConsole is the the window to the radio world, not being able to view it in any form vaguely approaching real time meant other solutions had to be found.

Screenshot 2014-11-07 17.24.10

It worked fine with low refresh rate applications such as WSPR, where the redraw is after every 2 minutes, but throw a moving waterfall at it and things started to go very wrong.


After much experimentation Real VNC was found to be the best of the bunch

Screenshot 2014-11-13 12.29.16

Thanks to Andy (G7UHN) for the guidance in fine tuning the setup. I eventually shelled out for a licence which gave access to mirror driver features which greatly enhance the graphical effects and make the whole system workable. RealVNC just works out of the box and requires minimal setup.

Dare I say it’s much better than Tight VNC. It readily scales the remote display to the viewing window size, there is a much faster refresh/redraw of screen.

The main need is to be able to monitor the SDR waterfall to identify signals and potential QSO’s. To aid that I’ve set the native Radio-Box display to a minimalistic Windows XP option, which disables the Aero desktop within Windows 7. I’ve also gone for a blank background and set my Fonts to Clear Type and 125% scaling to aid readability over VNC. I’ve disabled as many visual enhancements and effects that I can find as well.

Virtual Audio connectivity

Unless the radio is used directly at the desk, with a set of speakers plugged into it, it’s not possible to hear any audio output. Equally to use the output in Fldigi to decode CW, PSK31 etc there needs to be a mechanism to pipe the audio between applications.

A virtual audio program pipes the output from SDRConsole, normally destined for your speakers, onto an audio bus which is then available to any application requiring an audio input. As many applications as are necessary can tap into this bus and multiple virtual cables can be created.

Sounds complicated? Trust me it isn’t when you’ve got the very simple setup and config screens in front of you.

Think of a virtual audio cable as any other lead that you plug things into or equally plug into things. The only difference is it isn’t physical.

Screenshot 2014-11-26 12.05.01   Screenshot 2014-11-26 12.05.31


As the screen shots show, once installed on a system, Windows displays the Virtual Cable as any other sound device plugged into the machine.

There are several virtual audio packages in existence which attempt, with varying degrees of success, to achieve this.


The most popular is Virtual Audio Cable (current version is 4.14)



A free alternative is VB-Audio Virtual Cable


Unfortunately as hard as I tried I just couldn’t get VB-Audio Virtual Cable to work, which is a shame as it looks good.


Virtual Audio Cable on the other hand worked instantly. To get the audio out of SDRConsole and into Fldigi it’s as simple as selecting the Audio setting within SDConsole

Audio -> playback -> Line 1 (VAC)

Fldigi is using the virtual audio as an input source and everything, just works.

VAC has its own control panel and I’ve left it purely as the default settings.


To get a feel of how it works and to satisfy my curiosity, following this section of the manual gave great proof of concept, especially when you run the Audio Repeater. There are two available to select from and I used the MME one.

Simple cable usage

To use a cable simplest possible way, first run VAC Control Panel application and make sure that there are 1-3 cables and they are configured with typical parameters:

  • Maximum instances – 20
  • Milliseconds per interrupt – 5..7
  • Sampling rate range – 22050..48000
  • Bits per sample range – 8..16
  • Number of channels range – 1..2
  • Stream format limiting – Cable range
  • Volume control – disabled
  • Channel mixing – enabled
  • PortCls usage – disabled

Don’t close VAC Control Panel, it will help you later.

Run any audio producing application (a player, a tone generator, an audio editor) that allows you to specify a playback/render device directly and choose Virtual Cable 1.

Start playback and make sure that the application really plays to Virtual Cable 1. You should hear nothing but VAC Control Panel must show 1 or 2 new playback streams for Virtual Cable 1 and cable signal level indicator should be shown. If you hear a played sound, it means the application directs it to your hardware audio device, not to Virtual Cable 1.

If a sound is really played to the Virtual Cable 1, run Audio Repeater (MME variant) application and choose Virtual Cable 1 as a recording (Wave In) device and your hardware audio device as a playback (Wave Out) device.

Activate audio transfer clicking Start button in Audio Repeater. Now you must hear a sound played by an application started first and the Control Panel application must show a new recording/capture stream. It means that audio data are transferred from a playing application to Virtual Cable 1 and then Audio Repeater transfers them further to a hardware audio device. You have created a full audio path containing Virtual Cable 1.