19052019 – VK3/VS-011

VK3/VS-011 Mt Abrupt in VKFF-0213 In – Grampians National Park

DownSerraRange

Serra Range to the north. The seasonal burns are in full flight thus making the area smoky. In the valleys so wont be an issue accessing the summits.

SideView

Mt Abrupt is on the southern end of Serra range in the Grampians National Park. There is a defined track for access from the front. It not as bad as it looks. 6.6Km return along a busy track. Head out of Dunkeld down Victoria Valley road turning right into Grampians Road. There’s space for cars to park on Grampians Road, roughly 5km from the park sign. The track starts on the left side of road and is marked by a sign and steps. The track starts off easy and after crossing the washouts heads up to the ridge line. Straight forward walk but still raises a sweat.

You can access Signal Peak from this track. There is a marker now where to turn (54HXD1977439156) Whilst there no track to Signal Peak its a case of stay left of the ridge line and there may be tape markers left from the The Serra Terror held on June long weekend to confirm your insanity. Anyway I have been on Signal Peak previously and not interested in it so continued to Mt Abrupt.   

There were two goals for this activation, first being the short but solid walk up and second to test a doublet. 

HF Doublet

DoubletOnAbrupt

Obviously not a new design of mine. First saw a doublet in action with Tony VK3CAT.  There was some debate as to the use of coax and a bolt to stabilise the feeder but it proved to be a effective antenna combined with the KX tuner securing contacts from 80 down. From my version I now believe the bolt and coax was acting as a choke stabilising the performance of the antenna.

I decided to stick to the 88f length radiator. Its is proving to be a reasonable compromise on summits tight for space.

So this is a 26.8m (88 foot) radiator with 7m feeders ‘all band’ antenna. Ive had poor signal reports from the 26.8m end fed which has been attributed to coax losses. The end fed has a coax run to get the feed point some height. Reducing the length of the coax lead from 9 to 2m lead to RF issues and poor tuning (lack of counterpoise) so now has a 5m run. The end fed is maintaining contacts on 80 and 40 but according to the licence I have to experiment so hence the doublet. The idea of the doublet is the reduction of feeder losses and the vertical run brings the length of the antenna to ~40m. The run to the KX is heat-shrunk twisted pair with a 1:! current choke. The spreaders are dripper line with zip ties as seen on Warren VK3BYDs version. Simple cheap and worked a treat.

There is conflicting dialog on the web as to the role of the feeder in these antenna. The total length being the single length of feeder plus total length of the radiator (26.8 + 7 = 34.8m) implying  the feeder plays a minor role in radiating or length of the entire  feeder and radiator (26.8 + 14 = 40.8m).  I’ll let those smarter than me to debate this but given int is a non-resonate antenna I like the idea of 40m of wire in a compact deployment following the view of ‘as much wire in the air as you can get’. 

DoubletOnWinders

This unit tuned up on 80m find using the tuner in the KX and worked a treat.

Rolled out fine with double winders. This summit was selected given the space available the ends ended up draped on the top of the bushes when the tying failed with no noticeable impact to performance. Maybe we are getting a bit precious as to deployment given the height ?

SOTALog

anyway the results are in with three P2P and solid signal reports I’m a fan of such an antenna. 

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