One of the things I really like doing is working HF from the Australian Bush. I've made a 20m/40m linked dipole which works really well. We managed QSOs with Fiji and New Zealand (as well as all over Oz) when we went to the High Country just before Christmas. However, sometimes you just don't have the time or convenient trees to sling up a dipole. I've used tapped whip antennas on the VKS-737 network with great success. In fact, I've got a Bushcomm antenna that I bought 2nd hand 20 years ago. It's covered literally thousands of kilometres mounted on my bullbar on rough Outback tracks. It's even crossed the Simpson Desert three times! It may look a bit battered and bruised now but it's built like a brick dunny and it still works a treat.
So I though't I'd buy a tapped whip that covers the Ham bands. The Bushcomm is a bit pricey at over $300. Then I found the Opek HTV-600 for about $100 on Ebay. It covered all bands from 80m-6m. What more could I need? A quick check on eHam revealed mixed reviews but it was only a hundred bucks - nothing ventured nothing gained. Well, the antenna arrived last week. The build quality is OK - not great. It's certainly a lot more flimsy than the old Bushcomm and I'm not sure whether it would survive many Outback roads. But then what do you expect at that price? The vendor did thoughtfully provide a much better quality jumper lead than the crappy plastic ones supplied by the manufacturer as well as some additional tuning tips.
Tuning this antenna is fiddly but if you get it right it does work. I mounted the antenna on my bullbar, which is very well grounded. After spending an hour or so with an antenna analyser on a 35 degree day I found that my actual antenna lengths were nowhere near those suggested by the manufacturer.
These are my results:
80 metre band - antenna length 1,800mm - 3.6MHz SWR 2.0
40 metre band - antenna length 1,398mm - 7.1MHz SWR 1.5
20 metre band - antenna length 1,540mm - 14.16MHz SWR 1.3
15 metre band - antenna length 1,406mm - 21.1MHz SWR 1.2
10 metre band - antenna length 1,338mm - 28.0MHz SWR 1.6
6 metre band - antenna length 1,338mm - 50.0MHz SWR 1.2
On the 40, 10 and 6 metre bands the lowest SWR was either at the very bottom of the band or below it. On 40 metres, the lowest SWR was at 6.8MHz. The remedy for this is to fit a hose clip just above the 40m tap. I found that one hose clip resulted in the lowest SWR being right on 7.0MHz so I added added another hose clip and adjusted the antenna length to get the lowest SWR to 7.1MHz - which is where I wanted it.
Whatever you do, DON'T CUT THE ANTENNA to get better results because you'll need the full length for 20 metres. You need to remember that this is very much compromise antenna.
On air results
I use a Yaesu FT-450-D on 100 watts for portable work. It's a very nice radio and an ideal first radio for new hams. I put out a CQ on 7.15MHz and was immediately answered by a VK4KX in Nambour near Brisbane. The signal report was 5 and 5. Melbourne to Brisbane is 1,455Kms or nearly 1,000 miles. That's the same distance as London to Rome. I reckon that if I was a UK ham and I made England to Italy on a $100 tapped whip antenna I'd be absolutely delighted.
This evening I had a long QSO with ZL3JAS in Christchurch, New Zealand on 20 metres, a distance of 2,340Kms. The signal report was 5 & 9 plus.
So far I'm very happy with this antenna!
Further reports on performance and stamina will follow.
So I though't I'd buy a tapped whip that covers the Ham bands. The Bushcomm is a bit pricey at over $300. Then I found the Opek HTV-600 for about $100 on Ebay. It covered all bands from 80m-6m. What more could I need? A quick check on eHam revealed mixed reviews but it was only a hundred bucks - nothing ventured nothing gained. Well, the antenna arrived last week. The build quality is OK - not great. It's certainly a lot more flimsy than the old Bushcomm and I'm not sure whether it would survive many Outback roads. But then what do you expect at that price? The vendor did thoughtfully provide a much better quality jumper lead than the crappy plastic ones supplied by the manufacturer as well as some additional tuning tips.
Tuning this antenna is fiddly but if you get it right it does work. I mounted the antenna on my bullbar, which is very well grounded. After spending an hour or so with an antenna analyser on a 35 degree day I found that my actual antenna lengths were nowhere near those suggested by the manufacturer.
These are my results:
80 metre band - antenna length 1,800mm - 3.6MHz SWR 2.0
40 metre band - antenna length 1,398mm - 7.1MHz SWR 1.5
20 metre band - antenna length 1,540mm - 14.16MHz SWR 1.3
15 metre band - antenna length 1,406mm - 21.1MHz SWR 1.2
10 metre band - antenna length 1,338mm - 28.0MHz SWR 1.6
6 metre band - antenna length 1,338mm - 50.0MHz SWR 1.2
On the 40, 10 and 6 metre bands the lowest SWR was either at the very bottom of the band or below it. On 40 metres, the lowest SWR was at 6.8MHz. The remedy for this is to fit a hose clip just above the 40m tap. I found that one hose clip resulted in the lowest SWR being right on 7.0MHz so I added added another hose clip and adjusted the antenna length to get the lowest SWR to 7.1MHz - which is where I wanted it.
Whatever you do, DON'T CUT THE ANTENNA to get better results because you'll need the full length for 20 metres. You need to remember that this is very much compromise antenna.
On air results
I use a Yaesu FT-450-D on 100 watts for portable work. It's a very nice radio and an ideal first radio for new hams. I put out a CQ on 7.15MHz and was immediately answered by a VK4KX in Nambour near Brisbane. The signal report was 5 and 5. Melbourne to Brisbane is 1,455Kms or nearly 1,000 miles. That's the same distance as London to Rome. I reckon that if I was a UK ham and I made England to Italy on a $100 tapped whip antenna I'd be absolutely delighted.
This evening I had a long QSO with ZL3JAS in Christchurch, New Zealand on 20 metres, a distance of 2,340Kms. The signal report was 5 & 9 plus.
So far I'm very happy with this antenna!
Further reports on performance and stamina will follow.