What are IQ signals?

The terms IQ are increasingly commonplace in amateur radio literature.  Open any copy of Radcom or read anything about Software Defined Radio (SDR) and you will see the terms IQ.  But what are they?

Since transitioning from a cherished black-box radio last Autumn to SDR I’ve been meaning to understand the mysteries of IQ.  Fundamentally, its really very simple.  But I’ve read several descriptions on the Internet which, quite frankly, are just confusing – too many words all trying to convey something that is much easier done visually.

Tonight, I discovered the video below.  It is an excellent description of, not only, IQ but of modulation and especially BPSK, 4PSK and 16PSK.  I highly recommend taking a few minutes and watching even if you are not interested in SDR and IQ.

Andrew
G0RVM

The new FT-891

FT-891_yaesu_dayton_ag1A little news hot off the Dayton press…  Yaesu have a new mobile HF & 6m, 100w transceiver.

Looks a little like the latest series of Icom radio’s with its black on white display.  Its also similar to the FT-857 with function buttons surrounding the its display.  The head is detachable and it claims to have a 32-bit IF DSP capability.

FT-891_yaesu_dayton_2016-ag1

With the IC-7000 now firmly retired and the IC-7100 head more suited to desktop operation than mobile, I just wonder if Yaesu have seen a gap in the market….  What will Icom do next?

But why omit V/UHF?  Seems a little odd.  Of course this could be the first of several re-designs and there may be other models yet to be released.

Perhaps it will be launched into Europe at Friedrichshafen.

Andrew
G0RVM

Field weekend

Derek, Mark, Andy and Rob fitting the hexbeam to the towerFriday 29th April saw the start of the TSGARC big Field Weekend. OK, not quite the same as its BBC Radio 1 namesake but just as much fun 🙂  Setup took place on the Friday and was finished by late afternoon – much quicker and more smoothly than last year.  The event ran over the following Saturday, Sunday and everything was dismantled and removed by mid-Monday afternoon.

So a big thanks to those that came and who helped setup and/or remove everything.  An event like this was only possible thanks to some accommodating friends of John, M6EQQ who allowed us to use their field.  As a thank you the club bought them a bouquet of flowers and some beer.  I will let you work out who received what!  Like preceding days, the Monday was a relaxed start and the dismantle job only started late morning.  Unfortunately, as some people know only too well it started raining just after lunch which incentivised speedy work.  But some of us got a little damp – Rex 😉

FT-897, TSGARC field weekend 2016Over the whole weekend there where two radio tents, the first used the FT-897 loaned to the club by Derek.  This allowed HF and VHF (6m) operation using a G3TXQ Hexbeam from MW0JZE (top image).  VHF (2m) operation was possible using a 9-element Yagi from Tonna.  The FT-897 PA provided 100w on HF and 50w on 2m.  The highlight of the first day was a solid 17m contact into Japan by Derek using SSB.  But there where also lots of other contacts across the European and American continents.  The hexbeam was observed to have useful directivity mounted at 12m atop the trailer tower.

John, M0HFH working Morse code on 14MHzThe second tent used a home-brew HF (20m) Bobtail – orientated to provide East/West lobes – and a 3-element Yagi for 2m, both courtesy of John M0HFH.    This tent used the clubs FT-450 both for SSB and CW plus an FT-857 and FT-817 provided by John and Rex.  The tent also showed rebellious tendencies, opting at times, to use some rather exotic batteries which no-one wanted to be anywhere near!!  Thanks John!

There, was of course, another tent, a very important tent and one where people congregated.  The ‘brew tent’ was where we had the stove, tea, coffee and what seemed like an endless supply of bacon – thanks Jane – plus copious amounts of biscuits 🙂  The weather was mostly dry but a little on the chilly side so this was indeed a popular tent.

In total we had two big (6m x 4m) tents, the rebellious tent (2.5m sq) plus a small day tent to keep the generator dry.  These provided ample space and shelter for the weekend.  The final accommodation to mention was the chemical toilet, arguably the most important item to making the field weekend possible.

TSGARC Members at work!Everyone who went had a good time and all the equipment worked well.  Simultaneous operation of two HF stations was not really possible, or expected, due to the proximity of the antenna’s so perhaps a project for next time is to make band-pass filters.  It was a surprise to find  that even HF low power transmissions broke through on the other tents VHF (2m) activity.

With only two radio’s in operation at any time it was common to find people in the ‘Brew tent’ or contributing to activities in the field.  In the above image John, M0HFH is being helped to connect an ATU to the feed point of the HF (20m) Bobtail.

Mark helping John fit an aluminium section to the top of a fibreglass mast.There was also some genuine help.  Many hands made light work of jobs including raising the tents and preparing the operating positions.  Unpacking, assembling and raising the hex beam was made easy with great support.  Thanks also to Ron, who stuck it out in the rain on Monday to methodically dismantle the hextbeam such that it can be easily reassembled next time.

Personally, I’m already looking forward to another event next year.  But we may move the date back to the late May Bank holiday weekend as the weather should be a little warmer 🙂

Andrew
G0RVM

Programme update

Until recently our Programme has contained On-air nights. Before our radio room came into operation last year these where necessary as all activities shared the same room. However, now that we have a separate radio room we no longer need to reserve specific nights for operation of the radio’s as this is now possible on any evening by club members. As a result the committee has agreed to remove On-air nights from our event programme.

Members are encouraged to get our club on-air each Wednesday evening and/or on other days if they so wish.

If members would like to see new events in our programme, could they please communicate with a committee member to progress their suggestion.

Andrew
G0RVM

Strange problems….

So, for a couple of months I’ve had a growing suspicion that I’m not receiving as well as I am transmitting.  I first noticed the problem when observing the strength of signals from GB3VHF which after one winter storm seemed much weaker than it had been.  However, there seemed to be no impact upon transmit as SWR remained negligible and stations some distance away where still receiving me well even when my transmitter was generating about 0.5W PEP!

Since first noticed I’ve worked many stations and the signal reports always seem to identify that I’m not receiving as well as the remote station.  Establishing this pattern has taken some time.  It should be said at this point that its the same antenna and feeder used for both transmit and receive.

Its been a wet Winter and not really suitable for removing weather proofing from exterior connections and outdoors work.  But now Spring has arrived things are finally starting to get dryer and warmer.  Alongside this I’ve taken down the mast and antenna for work to support an new PRO.SIS.TEL 641D rotator.  This has enabled a detailed inspection and test of feeder and antenna.

Before starting any work I thought about and identified the following possible causes:

  1. failure of the receiver, possibly signal amplifer
  2. damaged feeder, possibly a connector problem or water ingress
  3. damaged feeder at the antenna feed-point. possibly also water ingress.

Problem (a) seemed possible but without a second receiver its very hard to be sure.  But its a quality Transverter (Kuhne TR144H) and I’d be surprised if that had partially failed – remember signals are only 2 – 3 S points down on what I think they should be.

So, (b) or (c) seemed much more likely.

So with the mast down and everything removed back to a dry, warm environment I removed weather seals – no sign of water or even the slightest amount of moisture ingress.  The coax was tested with a DC Ohm meter – no shorts or higher than expected resistances; with an antenna analyser and dummy load – again this looked perfect.

InnovAntenna feed-pointSo attention shifted to the antenna feed-point, pictured before it went outside for the winter and before the connections where weather sealed. Note: Grey plastic tape overlays amalgamating tape.  Again, there was no signs of moisture ingress into the coax, but there where signs of galvanic corrosion between the aluminium driven element and the stainless steel (A2 grade) machine screws to which the feeder connected.  Actually, to be more precise between the aluminium driven element and the flat washers on each machine screw.  It was clear that the liquid rubber sealant which I’d applied had not sufficiently covered these connections and thus water had been in contact between the different metals acting as an electrolyte.

To be clear, the machine screws where not showing any significant signs of corrosion, just the washers.  So the feed-point was thoroughly cleaned and reassembled without using the washers then liberally coated in liquid rubber to seal against contact with water.

Now, at this point I don’t know if this was the problem, but it does make some sense.  Any transmit signal would be of a much higher voltage/current than a received signal so would probably cross a mildly corroded junction with marginal attenuation.  But marginal attenuation of a much weaker signal would be more noticeable.  That’s my reasoning anyway.

The acid test will be when I erect the mast and antenna again in a few weeks and see if received signals such as GB3VHF have returned to their earlier strength.  When doing this I will also use new feeder, so if signals are stronger I’m never going to be absolutely sure the problem was galvanic corrosion.  Of course the problem may still be present and it could be another cause such as the receiver!

For information, the antenna is an 8-element LFA Yagi from InnovAntennas.

Andrew
G0RVM

Rotor interface

PST-641 / Fireco InterfaceLast year I purchased a pneumatic 11m mast that can support a head load of 35kg.  Currently I use an SPID RAU rotator from AlfaRadio mounted at the top of the mast to rotate antenna’s.  At 6kg the rotor is reasonably light but for a while I’ve felt it would be better placed at the base as this removes 6kg from the top of the mast.

This little project will need modifications to the masts support/tilt-over base, a new rotor – as the SPID won’t take the vertical load – and an interface between the rotor and mast.

PST-641 / Fireco InterfaceThe project has taken the first step.  After drafting an engineering drawing of the rotor/mast interface a local engineering company made one for me.  For reference the rotor is a Prosistel PST-641D and the mast is a Total Mast Solutions / Fireco 115mm (base tube) pneumatic mast.

I’ll post again next month when I hope to receive the new PST-641D rotor and progress the next stage in the project.

Andrew
G0RVM

Radio restoration

Vintage radio restorationA big thank you to Mike M1DPB for a fascinating talk about restoring vintage radio’s last night.

For those that could not attend, Mike brought along a couple of radio’s, pictured below, and presented the restoration steps he had taken plus described many of the pit-falls to watch-out for when reapplying power after many years.

There is something about the smell of old radio’s, its unique. It cannot be described; yet we can all identify it and it triggers memories from years ago 🙂

Vidor vintage radio'sVidor vintage radio's
The slideware from the presentation will soon be appearing in the Lecture notes section of the website.  The slides detail many of the steps which Mike discussed in his talk.

Andrew
G0RVM

Vintage radio’s

A few weeks ago I was handed two images by Stan (G3RYM).  They show some vintage radios being displayed at a TSGARC meeting.  The gentleman in the purple top is Mike M1DPB.

If you can provide any further information such as photograph date or location that would be great.  It would also be really helpful if anyone can identify the radio’s.  Either let me know directly or by replying to this post.
Radio'sRadio1

Andrew
G0RVM