See Day 1 notes for the first half of this piece!
Convention's over! I left Milton Keynes at roughly 1630 after a full day of lectures and after a stopoff in Glasgow made it home at 3am. Total round trip of 1003 miles! That's a long way to go for some radio chat.
Day 2 was again insteresting, enthusing and inspiring - here's a compressed colletion of the notes I took.
Session 1: Try Moving Up to 1.3GHz
Given by: John Worsnop, G4BAO
Unfortunately, becuase I'm a tool, I was 15 minutes late for this so missed the intro. It's okay, I arrived when the good stuff started!
Propagation Modes of 1.3GHz
- Tropospheric enhancements and ducting
- Well known and documented on other bands
- Better at the coast. It's documented that sea ducts work well, due to both flat land path between station and a long region of temperature inversion
- Has been seen to run up to 2500Km
- Aircraft Scatter
- The classic UHF+ trick - bounce your signal off the underside of a plane to get better DX
- Tropospheric Scatter
- This is always available, and is regularly used to make contacts of 500Km+
- Caused by either refraction or just random scatter of the wave as it passes through the turbulent troposphere.
- Earth-Moon-Earth (EME)
- This used to be considered very difficult, but thanks in part to improving digital modes and high EIRP, it's becoming more achievable.
Due to the short wavelength (23cm), antennas can have a higher gain within the same footprint as their cousins on the lower bands. They can also be more easily stashed and hidden in plain sight!
- A yagi with 3m boom length can have roughly 20dBi gain. At 2m, this would be roughly 13dBi. That's a big ERP increase for an identical input power!
- A 28 element yagi is 1.6m long and has roughly 17dBi gain.
- They'll be easy and compact to vertically and horizontally stack for array gains.
- a 1.2m diameter dish can exhibit 23dBi gain. That's not too shabby!
Coax is pretty lossy at these frequencies…
- RG213 loses 3dB/10m.
- FSJ 4-50 loses 1.35dB/10m
- Ultraflex13 loses 1.2dB/10m
Using a masthead preamplifier can mitigate these losses.
At this point, the lecture became about antenna engineering and got quite technical. It was a joy to follow along with. The main takeaway was that reducing the antenna system ‘noise factor’ will make performance significantly better.
This can be calculated by applying the Friis Formulas for noise to your antenna system.
The main takeaway of this is that the overall noie figure for the system is introduced in the first stage - be it lossy coax or a poor quality amplifier. Having good hardware and good coax up the tower is super important here.
Using the VK3UM RX Performance calculator can help you model this system with different component values. (I can't find the specific software at the moment, I'll prod about and see if I can locate it)
As antenna inclination drops, the background noise will increase by about 10dB. This is due to the different sky temperatures -
- Vertical 10K
- Horizontal 294K
Keep this in mind for terrestrial communications.
The noise floor here is lower than other bands due to less commercial equipment, but as with everything it's slowly raising.
Ease of entry
- 10-10W will do local, LOS contacts, if used with a small yagi
- 50-100W will be a good entry point for aircraft/tropo scatter
- 100-400W will make aircraft/tropo scatter much easier to get great results.
My takeaway was:
The true reward of 1.3GHz will come from careful loss management and good system design. I'm definitely keen to try 1.3GHz some time soon!
Session 2: Where Shall I put my HF antenna to work DX and Contests?
Given by David Aslin, G3WGN
I didn't take any notes during this one, but it was enjoyable to see all the considerations that go into both home and antenna location for serious DXers.
The overall takeaway was that the take off angle (TOA) of your antenna is super important - by using tools like heywhatsthat you can get an insight into what directions you can have low take off angles. These guys are optimising for 1-2 extra degrees lower, and designing antennas based around the point on the radiation pattern where they radiate the most.
Chasing big DX, especially in the sunspot minimum, sounds like an intimidating, challenging and all-consuming task!
Session 3: Simple 5.6GHz equipment & operating /P in the SHF UK Activity Contests
Given by Dave Yorke, G4JLG and Mark Bryant M0UFC
The main points of this talk were:
- 5.6GHz WBFM on a shoestring
- Portable microwave operation in SHF AC
- G6GVI's 2.3 GHz SDR TX/RX
G4BAO has an article in a recent Radcom covering this called “GHz Bands on a Shoestring”… I see a pattern already.
The guys are using an “Active Robots Airwave FM Video Sender” to modulate voice to GM audio. A 0.5W output unit is around £30.
There are separate antennas and modules for RX and TX.
To make the module work they're using an audio amplifier on input for voice clarification, filtering and preparation. Thermal dissipation must also be considered, and a stable 5V supply is also important.
This is the module they're using. There was a quick mention of filtering the sidebands that contain video, I'll need to investigate that.
it's being fed directly into a patch or dish antenna and squirted line of site across Manchester. Very cool little find, I'm very taken with this.
Portable microwave setups
I don't know what any of these are, but I'm recording them so I can grow into the knowledge and find out later.
- 3cm - Gunn Diode WBFM TX, RX via a converted set top box
- 9cm - They're using Converted AS4000 units
- 13cm - G8LMW 400mW TXVR
- DB6NT TXVR for 9cm and 13cm also.
- MMIC RF Amplifier
I didn't take many notes duing the SDR section - I'm somewhat SDR'd out!
Session 4: Professor Cathryn Mitchell, M0IBG
This was a great talk about Solar Storm events and space weather, which I know relatively little about.
It also contained the word “Magnetopause”, which Ana and I giggled at childishly.
In 1859, there was a huge solar storm, or series of storms, known as the “Carrington Event”. Aurora were seen a extrememly low latitudes, and there were lots of induced currents in telegraph lines, amongst other things.
It's reckoned that when the solar wind & earth's geomagnetic field coupled, it was sufficiently close that charged particles weren't funneled to the polar regions by fieldlines, but just attracted towards the earth.
It's been observed that solar cycle activity isn't coupled to solar storm events - That is to say, the incoming solar minimum doesn't mean the chance of a major storm event drops.
- NASA Stereo A/B Satellites saw one in 2012
Things that will cause damage from solar activity are:
- EM Radiation//X-rays
- Particle Radiation
- Magnetic Fields
Things that the above will make happen…
- Radio Frequency Interference
- Electronic Malfunction
- Radiation Exposure
- Induced Currents in long metal structures - wires, rails, etc
- Ionospheric Disturbance
- GPS Disturbance
- Navigation/Timing/Communication issues
- Propagation issues
- GPS Disturbance
There was a list of major national infrastructure that will be affected by the above (telecoms, rail, shipping, aviation, the financial industry to name a few) but I'll leave it up to your imagination to work out more!
For the national grid, it was noted that transformer burnout through induced currents in cabling could disable the grid for a significant period of time. If enough are damaged to use more than available spares, time to replace jumps from days to months. I'm sure every industry/public service will be facing similar issues
- EGNOS/WOS are the aviation ionospheric monitoring services in place
swpc is the live prediction centre of solar weather from noaa.
If shit's going to hit the fan, this will give you an hour to say goodbye to your iPhone.
Session 5: The Story of SDR and FlexRadio
Given by Gerald Youngblood, K5SDR
This was a pretty good way to finish the event - Gerald is a great speaker and salesman and hearing the story, and secrets, of his company and product so well presented was really enjoyable.
The FlexRadio 6000 Series are pretty incredible devices, and FlexRadio are developing really interesting things to augment them.
They're essentially direct sampling TX/RX SDR units, acting as a flexible radio server. The model you get will define the number of bells and/or whistles you get, but multiple band RX/TX, multiple operators and more are already in place.
They've also opened an API for the devices, so you can write your own applications to use on the network.
If you catch me, ask me and I'll gush for a while about it, but the chances are that if you know me you already know alllllll about how much SDR can offer!
Super cool. Very impressed - I'll be watching Flex in the future, and keeping an eye on their commercial products for work.
Session 6: Raffle
We didn't win anything, it was a FIX!
Yeah. The RSGB Convention exceeded my expectations greatly. It's got me excited about radios again, hopefully I can leak this over to my local club and friends. It turns out amateur radio isn't just about junk sales and HF contacts - there's people doing interesting and innovative things, and the barrier to entry on the higher bands is much lower than I previously thought.
Many of the conversations that were had during the weekend with people of all ages centered on the fact that there is always something new to discover and enthuse about in amateur radio. That has very much been my experience, and i've always enjoyed it because of that. When I've been on the air for 50 years like some of these guys have been, I hope that's still true!