RSGB 5G Network Talk

After last nights excellent and informative talk by Gary on Network systems in which a 5G was mentioned, there is a talk at the RSGB meeting in Redland on Monday 28th November by Prof Andrew Nix (University of Bristol) on the 5g network being tested in Bristol.The Network uses Rediffusion infrastructure in the form of underground cabling bought by Bristol University for experimental purposes many decades ago.

Please see the Link to the event below

rsgb-november-2016

Networking Talk

Well Wedensday 23rd November was a suprising talk by Garry (G7NVZ) on Networking  because it should have happened next Wedensday 30th November.

Thanks Peter (M6KVA) for pointing it out. Shame he left it until after the talk to let me  know 😉

So next week will be a programme planning / discussion night.

Returning to Amateur Radio

Just wanted to post this piece regarding how heartened I was to see so many old Amateurs returning to the hobby. In the past 3 weeks I guess I must have seen at least two or three per week (two today Weds 23rd) coming back to the hooby having posted on the Amateur Radio FB page.

Don’t let anyone tell you that Amateur Radio is dying. Its definately not and I have a feeling that this may be the start of a resurgance of interest. Goes hand in hand with Andrews post on the Introduction to Amateur Radio.

Way to go!

Mark 2E0RKM

 

The HF antenna…

So, most members should be aware by now that the old 40m dipole has been removed and replaced with a new 40m dipole!  The feedpoint 1:1 balun was also changed for good measure and sealed thoroughly for the winter.

But this is not the end of the work on the HF antenna, that was just task 1 😉  Task 2 consists of two activities and is planned for Spring 2017 once it dries and warms a little 🙂

Activity 1 will add elements for 30m and 20m expanding the 40m dipole into three parallel dipoles. This will result in a tri-band antenna that is resonant on 40m, 30m and 20m giving us a very useful antenna.

Activity 2 will replace the coaxial feeder between the radio room and the antenna feedpoint.

TSGARC parallel dipoleToday we have approximately 2.3dB of loss at 7.1MHz between the radio room and the antenna feedpoint.  Assuming the coax is in the very best condition (which its not) and it’s RG-58C (Its an RG58 of some sort) this equates to about 54m of coax.  That’s a 40% power loss on Tx and Rx.  Replacing this with RG-213 reduces the loss to 0.9dB or a 19% power loss.  An improvement of 1.4dB or 20% doesn’t sound much and its not but consider the situation at 14MHz.  With RG-58C there is 3.2dB / 53% loss but using RG213 the loss is 1.3dB or 26%.

Frequency RG-58C RG-213/U Ultraflex-10
7.1MHz 2.2dB 0.9dB 0.5dB
10MHz 2.7dB 1.1dB 0.6dB
14.2MHz 3.2dB 1.3dB 0.8dB

Coax loss per 54m 

To put this differently.  The transmitter places 100W max into the feeder at 7MHz, 10MHz and 14MHz.  With RG-58 the antenna receives: 60W, 54W & 47W respectively.  Replacing with RG-213 results in: 81W, 77W & 74W.  Using a better coax and one that does not cost  much more than RG-213 the situation can be improved further.  The overall difference of using something like Ultraflex-10 over RG-58 is definitely worth having and that is why activity 2 is so important.

The completed parallel dipole antenna will remain in its current location supported by the trees at either end.  But supporting the end of the antenna elements will require two attachment points instead of the one we have today.  Investigation has showed this is not a significant obstacle.

Thanks to Peter, G3LDO for the above diagram taken from his excellent book Backyard Antennas.

Antenna Maintanance

Yesterday myself, Andrew, Graham, Rex, John and John spent the day at the Chantry renovating the club’s antenna systems.

Our plan for the day was to inspect the existing antenna systems, replace a section of coax between the attic and balun and to install and tune the new 40m dipole.

Condition of existing antenna systems

Existing 40m dipole balun

Existing 40m dipole balun

The overall condition of the existing HF antenna was good, but clearly the self-amalgamating tape has suffered from UV degradation. This doesn’t appear to be a major problem however the antenna has only been up roughly 4 years, so the problem would get worse over time.

A photo of the existing co-linear VHF antenna

Existing VHF Co-linear

While on the roof we also inspected the existing VHF antenna. It is clear that it is not ideally placed, being blocked by the chimney stack as well as the Chantry’s satellite dish.

Replacing the coaxial cable

One of the jobs for the day was to replace the RG-58 coax run between the attic space and the existing balun with some superior Westflex 103. In order to do this, Andrew and myself had to climb into the attic in order to cut the existing cable and solder new UHF connectors onto it. This allowed us to replace the cable between the attic and the antenna. On completion we measured the loss through the cable using a 50Ω dummy load and power meter.

new cable run

New Westflex 103 cable run

We measured the loss at just under 3dB at 7mHz. We measured 60W at the end of the cable with a 100W input. Currently we plan to improve this loss further by replacing the rest of the cable to the shack

Andrew holding a dummy load and power meter

Andrew getting ready to test the loss through the new cable

Installing and tuning the new 40m dipole

With the new coax installed, we now set to work installing the new antenna. Before we could putt the new dipole in place we had to let down the existing antenna. As the two ends were attached to trees, I volunteered to put my tree-climbing skills to use and lower the existing elements

Rex at the foot of a ladder

Rex giving us a hand getting up the trees

With the antenna on the ground we attached the new dipole and hoisted it into the air. Following some tests with Andrew’s MFJ antenna analyser we deduced that the elements were too long. Following several rounds of tuning we reached a state where everyone was happy with the performance of the antenna.

New 40m dipole balun

New balun installed

We sealed the connections with self amalgamating tape and headed to the shack to have a listen to the band.

40m dipole

 

Performance

Frequency (mHz) Resistance (Ω) Reactance (Ω) SWR
7.0 60 8 1.2
7.1 78 0
7.2 112 0 1.5

We also tested the SWR in the shack and measured an SWR of 1.4 at 7.2mHz. A quick sweep of the band picked up some loud and clear Morse, although this may be due to a contest that was running at the time.

Conclusion

We hope that the new 40m dipole continues to deliver excellent results. There are still improvements that need to be made to the club’s antenna systems, including:

  • Adding the two other elements (30m and 20m) to the fan dipole array
  • Replacing the coax run between the attic and the shack with lower loss cable
  • Deciding on an effective way to relocate and improve the VHF antenna system.

I’d like to thank Andrew G0RVM, Graham, Rex G4RAE, John M3EQQ and John M0HFH for giving up their time yesterday to help the club. I had a great day and learned a lot throughout the process.

Peter Barnes
2E0UAR

Advanced Course Jan 17

Well its now official…sent off this morning and I am registered on the Advanced course in Jan with Steve Hartley in Bath. Work now begins although I have been reading the RSGB book now for a couple of months – take it everywhere..works for me. Strangely liking the Maths.

Mark 2E0RKM

 

JOTA 2016

CW Practice

John M0HFH showing Scout members how to use the CW Trainer.

This year we setup various elements of amateur radio at 1st Olveston Scout Group HQ. The station consisted of HF, VHF, UHF, CW, SDR & Flight Radar. The callsign used for this event was GB1OSG.

CW Live

John M0HFH setting up for the Scouts to do CW Live.

Friday was setup time, this went well with most things initially setup in a few hours. The TSGARC Friday net allowed us to test the VHF Station this was found to be deaf towards Yate so Saturday morning the antenna system was moved. Saturday  15th the final tweaks were made to the station then it was a case of waiting for the Scout Group members to arrive. During the quiet times members who attended got on with other projects including make a fan dipole for the club.

Saturday evening after Scouts and visitors had left for the evening John (M3EQQ), John (M0HFH) and Garry (G7NVZ) went searching for some DX on 20m and 40m. We heard a special event station with a call sign of DG500BIER which we tried unsuccessfully to get back to.

WIFI Down

WIFI Down!

The weather overnight deteriorated which caused some adverse affects on the WIFI setup. The antenna was on a tripod which got blown down. Soon had the link back.

Over the weekend as well as UK stations we got to Germany, Russia, The Netherlands and Switzerland.

Some members of the club who are also members of Woodhouse Park Scout Radio Club (GX0WOI) and they also ran a successful event. At times we were able to provide mutual assistance by providing a good working link to each other, this was mainly used to provide the Scouts the opportunity to try CW over the radio. I believe Rex (G4RAE) was able to read all that was sent to him.

Cable management.

Garry (G7NVZ) doing cable management.

Sunday was busier than Saturday for Scouts. The same thing were on offer for Scouts to see and try.

As is usual when it came time to finish it took less time to pack up than setup.

Thanks to all members who came and helped and supported this event.

 

 

JOTA 2016 Announcement

This weekend the club is excited to be hosting another Jamboree On The Air (JOTA) event. We will be based at the 1st Olveston Scout hall from Friday through to Sunday. We plan to set up stations covering VHF, HF, SDR, Morse, 3D Printing and more. Over the weekend we are expecting to receive visits from groups of scouts so that we can share our knowledge and experience with them.

We will be operating under the special even callsign GB1OSG for the weekend.

We hope to see plenty of scouts and a club members over the weekend, and i’m sure as usual a lot of experiments (successful or otherwise) will take place during our free time!

JOTA Logo

Peter
2E0UAR

RSGB Convention 2016 update

Camb-hams FlossieMyself G0RVM and Peter 2E0UAR attended the RSGB Convention in Milton Keynes this year.  We left Bristol around 15:30hrs but got stuck in jam after jam.  Towards the end of the journey ‘here comes another set of blue lights’ was becoming a bit of a joke!  Fortunately we did arrive before the buffet dinner finished.  It was a close thing tho as there where only a few slices of pudding pie left 😉

This was my first Convention and I must congratulate the RSGB for such a great event.  The accommodation was good, the food and conference facilities excellent.  It was educational to hear talks on a variety of subjects from speakers deeply knowledgeable in their subject.  Access was free to those under 21yrs too – a great way of incentivising attendance by younger radio amateurs.  Thank you RSGB.

In addition to the rooms hosting five parallel lecture streams there was a room with stands by Icom, Kenwood, the RSGB and of course, Martin Lynch who were the prime sponsor.    Outside this room was a rather large trailer tower with HF antennas providing live signals for the exhibitors.

Kenwood TS-990Proudly parked outside the front of the conference centre was Flossie, the mobile radio van of Camb-hams.  Protruding through its roof was a Clark pneumatic mast with rotary HF dipole.  The van looked excellent and a great way to get a portable setup to a distant location, setup and on-air with minimum fuss.  As I have a pneumatic mast also it was good to swap experiences, finding we shared some of the challenges associated to these masts.

Some of my favourite talks over the weekend were:

    • The new world of amateur satellites, Graham Shirville, G3VZV
    • The Story of SDR and FlexRadio, Gerald Youngblood, K5SDR
    • The VP8SGI & VP8STI DXpeditions, Mike McGirr K9AJ
    • Space Weather, Prof. Cathryn Mitchell, M0IBG.

I was really looking forward to “Best practice for VHF UHF DX” by Ian White GM3SEK but unfortunately Ian had to cancel.  Maybe next year.

Camb-hams FlossieFrom the first talk identified above I learnt that we as radio amateurs are soon to have a ‘bend-pipe’ transponder in geostationary Earth orbit.  Wow that is an amazing feat and I can’t wait till its operational.  Amazing.  The talk by Prof. Cathryn Mitchell was excellent being delivered superbly and hugely informative.  It was interesting to hear how in 2015 space weather was identified in the UK National Risk Register with an impact of the same scoring as emerging infectious diseases, inland flooding, effusive volcanic eruptions, major industrial accidents etc.  In fact, in 2015 the likelihood of a major space weather event occurring in the next five years was in the second from highest category.

I can thoroughly recommend attending the Convention and I know I will be booking my 2017 ticket as soon as they become available next year.

Andrew
G0RVM