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Repeater update 10-3-21

More work over the weekend. Saturday attendees at the Bluff were Peter VK5BE, Col VK5DK and John VK5DJ.

Three main tasks:
1) Remove the UHF antennas from the fence ready for the site inspection this week.
2) Install the Mt Eckersley/Mt Gambier Clubrooms linking yagi on the Gambier electronics tower.
3) Install an additional filter in the main receiver cavity line.

So what happened?
1) UHF repeater was turned off and the antenna laid on the ground neatly against the fence, Peter guiding the pole and Col and John bravely holding the end of a rope doing the lowering.

2) Peter brought along a long ladder and has installed the yagi pointing at Mt Eckersley about 7 metres above ground level. He and Col arranged the coax in a neat but temporary fashion. Rather than cut the long length of heliax, a temporary coax line was built out of three shorter pieces with two joiners. A compromise until we know if the yagi is high enough to get through to Mt Eckersley. Once this is confirmed we’ll make the coax one length. Tests show that the link is very strong into Mt Gambier and can be heard off the back of the beam in Millicent.

UHF link yagi pointing at Mt Eckersley

3) It was suspected that there were strong signals (or noise) overloading the 2M receiver. The cavity shown to people last Friday was retuned at Millicent to 146.3MHz and installed on site. Using a return loss device it was possible to show there was an additional 10dB of sensitivity gained by inserting the additional cavity.
As an aside some of the noise from nearby transmitters can still be heard on signals into The Bluff receiver but this can’t be filtered out for obvious reasons. The overload problem is fixed. Noise is just a feature of the site – there is so much RF on the hill.

Passband of cavity from 60MHz to 200MHz, note marker at 160.3MHz. The least loss is at 146.3MHz and is 0.4dB

Some measurements of the cavity performance at spot frequencies:
Commercial TX on site 70MHz -45dB
Commercial FM radio on site 96.1MHz -41dB
Repeater input 146.3MHz -0.39dB
Pagers 148MHz -18dB
Commercial services 160MHz -41dB

What does 45dB down look like? It might be easier to picture that as the power is down by 31,600 times. That is a great filter!
Even 18dB down is a reduction in power of 63 times.

Additional cavity in place to remove overload noise

On Sunday Peter and Col returned to the site as the link output had suddenly dropped off and signals became noisy into the link input of the Mount Repeater. Examination showed that the relay had failed in the link. These relays are 40 years old being ex-FM828. Fortunately there was an unused relay system in the link frame so Peter with judicious use of a soldering iron, various tools and great patience, was able to do a successful swap. Well done Peter. The link is now outputting 8W and all is good back to the Mount.

We hope to have the UHF antenna back up later in the week after the site inspection although a more permanent installation onto the tower is planned.

Testing Mt Eckersley repeater

VK3RSW on test – now linked into the SE 2m network

Today, Saturday February 27th, the Heywood repeater that was put on test recently at our Clubrooms, has now been linked into the South East 2m repeater network.

This repeater will allow members to access the SE network from the city of Mount Gambier, and its immediate surrounds.

This will be of a benefit to those Mount Gambier members who are currently experiencing difficulties in accessing The Bluff repeater due to an ongoing issue with its coverage.

The SERG repeater team have been working tirelessly to provide the best coverage possible during these uncertain times.

The repeater at the Clubrooms transmits on 146.875 MHz, and receives on 146.275 MHz. (No CTCSS tone is required)

It will be available for all Sunday broadcasts, and Friday night meetings and skeds whilst on test.

In order for this linking to occur, the IRLP/Echolink facility on our 70cm repeater will be unavailable until further notice. The 70cm repeater remains available, it’s just that we’ve temporarily made use of the UHF antenna at the clubrooms preventing this end of the link for IRLP/Echolink. Another antenna is being explored.

Peter VK5BE

For the SERG repeater team.

Update: The Bluff Thursday 25/2/21

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.

Temporary Mt Eckersley antenna pointing at Mt Gambier
Owen VK5HOS sizing up the hole in the corner of the hut

VK3RSW on test at SERG clubrooms

Today, Sunday February 21st, 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.

Working VK3RSW on test. Note the link transmitter is unplugged as no antenna connected.

Peter VK5BE

VK5RMG work on 16/2/21

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?

The antenna – two dipole array
The tree towers. ‘Our’ tower closest.
Our antenna just visible facing towards viewer, just below the dish and next to 70MHz array
One of our dipoles visible bottom left corner showing black insulation

Some Photo’s of the action at the Bluff this morning.

The Centre Tower is where our antennas used to be.
Highest marked antenna is the Receive unit which is believed to be faulty.
The lower marked antenna is the temporary transmit antenna.

“Old hut on the left. “New” hut on the right.
The cabinet in the “New” hut.
From left to right.
Site Superintendent. Tom, VK5EE
Norbert, VK5MQ
Dylan. Gambier Electronics.
A very big “Thank you” fellas.

Repeater update 11/2/21

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.

The Bluff 2M repeater

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.

New antenna at The Bluff

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.

View from the top. Our new dipole looking NW.
Looking down at Norbert’s foot and Dylan
Norbert’s test with the NanoVNA showing SWR<1.2:1

President’s visit to Portland

Meeting with Portland Radio Group

Sunday 24th 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