Posts

Just a brief update following activities at The Bluff today. Colin VK5DK, Owen VK5HOS and myself (VK5BE) attended.
Owen VK5HOS has a brilliant plan on how to repair the big hole in the floor of the hut. He will manage this issue through to its completion, hopefully by the end of next week.
The pole mounted temporary VHF array has been removed from the site and returned to my QTH until required for the Heywood project.
In its place, a RFI YB9 yagi (450-470MHz) has been installed on the vacated pole, horizontally polarised, and facing the Clubrooms in preparation for linking the Heywood repeater to The Bluff. The yagi SWR was measured at 1.13 to 1 at 449.875MHz.  We figured this was acceptable.
Initial tests show excellent solid signals are being received in Mount Gambier.
Tomorrow we plan plan to erect another yagi at the Clubrooms to link the 2 sites.

Today, Sunday February 21^st, the VK3RSW repeater was placed on test at the SERG Clubrooms in Mount Gambier.

Currently as a stand alone device, and not linked to the 2m network, it is being tested into a single antenna at the top of the Club tower via its cavity filters.

Any member who can trigger this repeater is welcome to use it to test its performance and reliability.

The repeater transmits on 146.875MHz, and receives on 146.275MHz. The CTCSS tone is not enabled.

If the tests prove successful, it may then be linked to our existing 2m network to further evaluate its performance. In the short term, give it a workout. Reports from mobiles and an idea of its range would be appreciated.

Peter VK5BE

Summary of work completed at Bluff today as reported by Norbert VK5MQ:

• Tested LDF4-50 feeder to new dipole antenna. Results were 20.8W into feeder at hut, 17.4W out at top of tower (into RF termination). Same result when connected to new dipole. So re-purposed feeder is OK. !?!
  
• Tested VSWR at top of feeder into new dipole antenna, 1:1.5  . Had a long think and suspected 70MHz dipoles that were at roughly the same level and about a wavelength away. Ideally all dipole arrays/antennas should be vertically spaced to achieve adequate isolation and minimize interaction. OK, then swung the new dipole away from the 70MHz array, about 30 degrees to the west and VSWR came down to 1:1.25  . So that proved to me there was some reflection/interaction with the 70MHz dipoles. Now the new dipole points directly at the Mt Burr summit, so they still are basically oriented to the north.
  
• Found that the phasing harness had one connector incorrectly assembled, with the N type centre pin protruding about 3-5mm proud of the connector. Repaired and tested harness at ground level with two RF terminations and again into one termination and one VHF dipole, VSWR 1:1.3
• Installed second VHF dipole (resolved assembly issue) and phasing harness, VSWR at hut 1:1.03  !! Happy with that.
• Replaced Naracoorte link feeder with known, good LDF4-50 heliax and routed onto cable clips and cable trays into hut. VSWR 1:1.5  and this is what I expected after appraising the condition of the link yagi. I think it’s near the end of life and should been replaced whenever it next totally fails.
• Replaced Mt Benson link feeder with known, good LDF4-50 heliax and routed onto cable clips and cable trays to hut. This work was requested by GE to tidy up coax cables on the tower. VSWR 1:1.03
• Tom VK5EE alerted up the reptile hazards on site at this time of year.
• Signal tests/S meter readings at VK5MQ QTH shows that there is more signal radiated than before these changes.
  

Huge thanks to Tom 5EE and Dylan from GE for massive effort today.

Volunteer needed to fix the hole in the corner of the shack at The Bluff. Will be an entry point for nasties. Minor wood working skills required. Have we got a volunteer?

Norbert went to the site this morning and turned the power down from 45W to 30W. This did not affect the received signal as we hoped.

For readers’ information, when a repeater is running from a single antenna the job of the cavities is to keep transmitter signal and noise out of the receiver. Too much power and the receiver is desensitised and does not perform properly.

We know that the cavities are working, we can feed signal into the receiver cavities from a signal generator and the receiver performs as it should. Norbert connected the new antenna system direct to the receiver cavities and it was very difficult to get a signal through. Remember system covers both the antenna and the coax.

This means there is a problem with the antenna system. As the antenna is new and the SWR is very low this means it is not likely to be the antenna (although possible). This leaves the coax. If coax is very lossy e.g. due to water ingress, then it will show a low SWR even though little TX power or received signal will get through. So our current theory is that we have faulty coax.

The coax is repurposed from an unused piece on the tower. It is certainly very old. So Norbert has taken home a piece of available LDF450 from the hut. He will put connectors on it and see if it has a low loss. If so it becomes a possible length for the antenna.

What next: Norbert plans a visit at the date/time he can get Dylan to help, perhaps about 2 weeks away (tentative 26/2/21) and weather permitting. He will climb the tower and with a power meter at the top he will check how much power is getting to the antenna. If it is very little he and Dylan will install replacement coax. While there he’ll check the SWR of the folded dipole as well. The tower does not have a ladder so climbing and staying in one spot can be very painful for the feet, legs and arms. This is not a simple thing we are asking of the antenna team.

In the meantime the transmitter is connected to the new antenna and the receiver is connected to the temporary antenna 12m up the tower. The transmitted signal will be weaker than we want and the receiver will not be as sensitive as we want, please be patient. The repeater team has made many visits to the site, we’re hanging in there. Hopefully you can too.

Still working on it.
Two working bees over the weekend 6/2 and 7/2. It has now been established that the cavities are on frequency, the antenna is fine with an excellent VSWR and the TX gets out.

The receiver is however very deaf and yet when a signal generator is fed through the cavities the receiver is very sensitive. When the transmitter is connected the receiver sensitivity drops badly. The TX checks out as clean on the spectrum analyser, it is not unstable or noisy.

We know that if separate antennas (the new one at the 70ft mark) is placed on the TX and the temporary antenna at about 40ft is placed on the receiver, both through individual sets of cavities then the system works although with some imbalance in performance. Conclusion, massive desense is causing the problem when the system is connected as it should.

Measurements confirm that the transmitter is putting out 45W. This is the most likely cause of the problem and desensitising the receiver. Normally 25W should be the setting for the TX. The control on the front of the TX is not working. Since leaving the site we have learned that there is an internal power control.

At this point, Norbert and Dylan are attending the site on Thursday or Friday to install the Mt Eckersley yagi. Norbert will adjust the internal control to 25W output and we’ll see if the system then works. This our best option for a solution as everything else checks out.

For the moment please be patient, your repeater team is doing its best.

Today 4/2/21 Norbert and Dylan from Gambier Electronics put the new antenna on the old “Hutchesson tower” now owned by Gambier Electronics. Quite an effort as the clouds threatened and the wind was building.

Tests so far are positive. Observations around the traps seem positive with signals better than they have been since we lost the position on the high tower.

At this point, the system is running on two antennas. The new antenna is on the transmitter while the receiver is on the temporary (faulty?) antenna on the tower. On Saturday 6/2/21 Col and John plan to visit the site to tune the gongs. Weather permitting we meet at 10:30AM. Observers welcome.

Unfortunately, the second dipole of the pair was delivered in a faulty state. This will need to be returned to the manufacturer. It’s likely that we might not bother about putting the second one up – it will be very handy in future if we have a need.

I’ve attached some photos from Norbert, I’d like to pretend that I took the photos but that lie would be a little too obvious. Top job Norbert and Dylan from GE.

Meeting with Portland Radio Group

Sunday 24^th Jan, I travelled to Portland to meet with the members of the Portland & South West Radio Group to let the members have some input to the proposed Heywood repeater site lease.

The meeting allowed the members to suggest numerous amendments to the draft document to be presented to the new owners of Mount Eckersley.

The lease agreement will be between the Mount Eckersley property owners, and the South East Radio Group, not the Portland club as originally planned.

Also, SERG will retain full ownership of the infrastructure, that includes the hut, tower, solar panels, and all the 2m repeater & link equipment in the hut.

The Portland club will provide the maintenance & tech support.

Another topic discussed was the storage container that SERG purchased to house the repeater, but has since been discarded following the acquisition of the concrete comms hut. The storage container will now be offered for sale to recoup the expenses incurred with its purchase.

PS Peter has spoken to the owners of the site and things are looking positive, still a few hurdles. We hope the revised lease agreement will be signed in a week or two and we’ll look to Portland Club to do some site works in preparation for the hut transfer.

Peter VK5BE

Today (Saturday 16/1/21), with the easing of COVID-19 cross border travel restrictions, I was able to travel to Heywood for a meeting with the Portland club President, Peter VK3HEW, and Secretary David VK3DJC at Mount Eckersley, to meet with the new property owners, Casey and Bonnie Taylor.

A very friendly and accommodating meeting followed, with all the terms and conditions for site access verbally agreed to. A formal lease document is now being drafted for all parties to sign off in a week or two. Site preparation will commence as soon as the lease document is signed.

Following the meeting, we all adjourned to the summit of Mount Eckersley, where the precise location of the repeater compound was pegged out. An area of 17m x 6m adjacent to the geo-survey trig marker (the highest point of the hill) was agreed to, which will soon be fenced off to keep the cattle away from our proposed facility.

The new land owners were very supportive of our project and are keen to have it fully operational as soon as possible.

Peter VK5BE

Following a visit by Norbert VK5MQ and checking his RTL-SDR dongle out I thought it might be fun to experiment with receiving the NOAA weather satellites. There are three of them circling the globe, NOAAs 15,18 and 19. They operate in the 137MHz area so can be heard on most 2M antennas.

Although I have tracking antennas, the satellites can be heard very easily. They’ve been up there for years and are quite big e.g. NOAA18 weighs 2.3 tonne was launched in 2005 and is in an orbit about 850km up. All these satellites are in polar orbit which means their path is north/south (mornings) or south/north (afternoons). Being nearly sun synchronous they appear more or less at the same time each day.

To receive the satellites you need a receiver that has a reasonably wide bandwidth, about 35kHz does the trick nicely so a software defined radio is probably best as you can adjust the bandwidth easily. I use a RTL-SDR.com Blog V3 dongle bought from South Eastern Communications in Frankston. I paid $44 which included the adaptor.

There are plenty of sites that show you how to get this going with SDR Sharp a software program that does the decoding to audio.

Use Orbitron (or one of a number of web based programs) to calculate when the satellites are going to be in view at your QTH. Orbitron is free and works well.

Once you have Sharp SDR working you have the audio available for decoding with WXtoIMG software. Download the Beta version of WXtoIMG from here:
https://wxtoimgrestored.xyz/downloads/
I use Windows 10.

You’ll need to enter your details in the setup of WXtoIMG. Your Lat/Long is important for the program.

Because WXtoIMG must access the sound coming out of SDRsharp program you need to install a virtual cable (not a real cable) program so it listens inside the computer. I got mine from:
https://vb-audio.com/Cable/
Download and install VBCABLE_Driver_Pack43.zip

Last job, go into your sound settings (right click on the speaker icon in the bottom right hand corner) and set your incoming and outgoing audio to the Output choose Cable input and Input device choose Cable output.

That’s it. All things being equal you should be able to receive pictures. By the way WXtoIMG does not start drawing the picture until the satellite is in view and then it starts automatically. It stops when it decides that the pass is over which is why your computer clock should be accurate.

Have a go, it’s fun and later you can use SDR Sharp and your dongle to decode weather satellites or the balloons from AREG.

John VK5DJ