SOTA activations for me have involved lugging a 40L backpack crammed with gear plus carrying a 10m squid pole. Recently I have become interested in trying to reduce the size and weight of equipment taken to a summit as well as reducing the time between arrival and getting on air. I had built a new 20m ground plane antenna and obtained a 5.4m squid pole and was itching to try these out on a summit. In the SOTAwatch alerts list there were some simultaneous activations coming up around lunchtime so it was time to throw my hat into the ring.
I was staying nearby to Mt Elliot which is a short distance northeast of Gosford on the NSW Central Coast. At the end of 2013 I had activated this summit, a one pointer, and scored loads of summit-to-summit contacts. When I left for the summit, one of the activators I hoped to work, Russ VK2BJP was already on the air. Being familiar with Mt Elliot made for a quick setup time. Still, I had to pack, drive to the summit, do the walk out and back into the activation zone along the Graves Walk and get set up. There was no time to waste!
Antennas: 20m ground plane and Diamond RHM8B base & whip
For this activation, I took the small backpack with just the radio, antennas and notebook. I wanted to try the Elecraft KX3’s internal NiMH batteries to see how they would hold up in a typical activation. The 2.2kg SLA battery was being left behind. The antennas I took along were:
- Quarter wave ground plane for 20m – 5.1m radiator and 4×5.1m radials
- Diamond RHM8B loaded vertical with telescopic whip
Operation would mainly be on 20m and 40m. For 20m I had the ground plane. For 40m I could use the loaded vertical as a compromise antenna, or extend it by using the radiator from the 20m ground plane.
It was a race against time to catch Russ on VK3/VE-149 so I quickly set up the loaded vertical. His spot had gone out at 0207z and I made my first contact with him at 0241z. It would have been faster if I’d had the SOTA bag already packed! I was rewarded with a 5×6 signal report – not too shabby over a 500km path on 40m using a 1.78m long ‘Cute’ antenna!
“Small backpack” SOTA station on Mt Elliot
I had time to set up a better radiator before the next potential summit-to-summit contact. The 5.1m radiator for 20m was launched up the 5.4m squid pole. It was a bit long as the radio was sitting on a bench about 1.2m off the ground. I let the extra wire just droop down and lie on the bench. Pretty soon after I got it tuned up, Phil VK2JDL came up on Knights Hill VK2/IL-007 150km away and gave me S4. He was received at an S point weaker than Russ which I put down to the lower angle of radiation characteristic of verticals.
Matt VK2DAG came up and spotted me and then I was off with some contacts into VK3 on 40m. There were no pileups – it was a weekday, but the gear seemed to be going the distance. Only 5W output instead of the 10W or 12W that I’m used to when using an external battery. To conserve the internal batteries I had switched off the LCD backlight and the RF preamp when not actually giving signal reports. This reduces current consumption from 205mA to 171mA when receiving. On transmit I ran it at the maximum power for the supply voltage (5W) and even had a small amount of speech compression for that extra punch – as per usual.
20m ground plane
It was time to try out the 20m ground plane for the first time. The Diamond loaded vertical was unscrewed from the radio and the 5.1m radiator plugged in directly. With the KX3’s internal ATU bypassed, the antenna matched at the top end of the 20m band. The droopy wire had been wrapped around the squid pole. A good contact was made with Nev VK5WG and then a spot for David VK3IL on Mt Hotham came up. It was for 40m so I tried to match the 20m ground plane using the KX3’s internal matcher, but there was no match. The contact was made after putting the loaded vertical back inline and I received an S3 report over the 550km path on 40m.
Back to 20m again and after spotting on a different frequency there were 3 more contacts including Mike VK6MB and John VK6NU. On SOTAwatch I had read that Mike wasn’t able to reach Phil VK2JDL. Maybe my ground plane was the secret weapon!
All possible contacts had been made on 20m so I decided to try 30m. The setup was changed over to the same as for 40m but with less loading. I used 41mm of the RHM8B loading coil instead of 92mm and got a good match. When setting up on a new frequency I bypass the KX3’s matcher and normally achieve less than 2:1 VSWR just by adjusting the length of the coil. After re-enabling the matcher a 1:1 VSWR is usually achieved. This applies on both 40m and 30m.
Operating on 30m with RHM8B and 5.1m wire
On 30m I made contact with Ron VK3AFW in Melbourne with good reports. Not many chasers but I was happy that the vertical was working well on this band too.
Another S2S – “just”
Phil VK2JDL had put up an alert for a second activation so I decided to wait it out. I had run out of chasers but my batteries were still going. I listened around the bands mainly on 40m. I experimented with loading up the antenna on 80m but the radio promptly shut down due to low voltage. I knew there wasn’t too much juice left. Reducing the power to 1W I was able to try again but could not achieve a match, probably due to insufficient inductance. It would probably work with a quarter wave radiator for 40m.
At 45 mins past Phil’s alerted time and with low batteries I decided to start packing up. I didn’t get very far before Phil’s call came through on 7090 kHz from Mt Kembla 130km away. What a relief – Phil had made it and I still had enough battery to make contact. My power was down to 1W and the radio shut down twice during the contact due to low voltage. Still managed a 5×4 report though and bagged a couple more summit-to-summit points making 22 for the day. Happy!
- KX3 can operate for over 3 hours using internal NiMH batteries
- Diamond RHM8B gives respectable performance on 40m using a ground plane
- 20m ground plane antenna is a great performer for working VK6
- Elevating the 20m ground plane radials shifts the min VSWR freq up to 15.5 MHz (why?)
- KX3 ATU wont match a 20m ground plane on 40m
- “Light” activations can be very successful!
Date:07/Jul/2014 Summit:VK2/HU-093 (Mt Elliot) Call Used:VK2IO/P Points: 1 Bonus: 0
||R56 S55 7090 Russ VK3/VE-149
||R54 S54 7095 Phil VK2/IL-007 Knights Hill
||R59+30 S59+5 7100 Matt
||R56 S59 7100 Robbie
||R51 S53 7100 Amanda
||R56 S58 14290 Nev
||R53 S56 7095 David VK3/VE-006 Mt Hotham
||R31 S53 14289 Mike
||R59+10 S59+5 14289 Harry in Wyoming
||R55 S55 14289 John
||R55 S56 10125 Ron
||R54 S55 7090 Phil VK2/IL-015 (1W – low battery)
Thanks to all the activators and chasers!
During the activation, Harry VK2GE popped up for a contact. He is a local not used to hearing such strong signals on 20m. I dropped down to 1W and was still over S9. It turns out that he resides very close to where I was staying and he invited me over. After finishing the activation I popped in for an eyeball contact. He showed me his setup with a 20m inverted Vee on an 8m squid pole. I gave him some information about SOTA – I’m sure it was his first SOTA contact. Where he lives is about 100m from the “quiet RF spot” I often drive to in order to work those weaker SOTA stations – what a coincidence! Anyway, watch out for Harry on 20m – a new potential chaser.