Mt Taylor VK1/AC-037 using a Telescopic HF Antenna for the FT-817 – Diamond RHM8B
Tonight I activated Mt Taylor VK1/AC-037 with the intention of working 2m and 70cm. I didn’t have plans to operate on HF but did have a portable telescopic center loaded antenna in the SOTA bag. The antenna is not a cheap Chinese Miracle antenna and believe it or not the antenna works without a proper counterpoise. Oh bugger the purists will not be happy with me, yep I can hear you say ‘sure it does’? I didn’t say it was 100% efficient, I said it works with the FT-817, not much of a ground and 5 watts output. Read on…
During the 2m activation Andrew VK1DA popped up for a visit. Excellent timing on Andrew’s behalf I had my dogs with me and they are a handful. Andrew took the dog leads while I extracted the HF antenna from the SOTA bag. If you didn’t realise we had 3 VK1 Andrews on 2 summits. 🙂
The antenna is a Diamond RHM8B and mounts on the FT-817 front BNC connector. To tune the antenna you extend the telescopic whip and move the loading coil up or down on the linear scale. You extend the coil-sleeve for 40m and collapse it for 6m. On 20m the coil-sleeve is extended to about 120 mm, I didn’t record the exact length, it was getting dark. By the way, you need to change the menu antenna setting on the FT-817 to the front BNC. 🙂
Where did I first hear about the Diamond antenna? A few months ago I was on the NSW south coast and chased Glenn VK3YY who was using what he called a ‘cute’ vertical antenna. (check Glenn’s blog for ‘cute’ antenna) I was using a half wave dipole and very surprised by the quality of Glenn’s signal given the size of the antenna. At the time I thought this antenna would be perfect for a quick SOTA activation or could be useful in an emergency, say injured in the bush and the gear is within reach.
Look it’s not designed to compete with a half wave dipole or a 3 element yagi, but it is portable and lightweight ideal for a quick easy activation after a long walk to a distant summit.
Some pictures showing the antenna and the mounting arrangement on the FT-817 at Mt Taylor VK1/AC-037 and details of the activation. Photos courtesy of Andrew VK1DA.
How does the Diamond antenna perform? Looking at it you wouldn’t expect it to do much other than warm the ground and clouds. The antenna mounts directly on the front panel BNC connector and didn’t need a counterpoise or ground wire to achieve a low SWR. Yes I may have achieved a better outcome if I had used a ground, put it simply I didn’t have a ground wire in the SOTA bag. In my case the FT-817 was sitting in the vertical position purchased against a rock with the rear aluminum heat sink sitting on a rock. Not much of a ground you say, yes I agree.
Does it work, yes it does. Would it work better with a counterpoise, most likely. Here are the results of the HF activation.
On 40m 7.090 MHz I worked: Marc VK3OHM S58 R55, Matt VK2DAG S59 R54, James VK1DR 59, Paul VK5PAS S58 R54, Peter VK3PF S58 R44, Gerard VK2IO S58 R54, Ben VK3FTRV S58 R46, Andrew VK2FAJG S58 R31 and Matt VK1MA S59 R45. I was very surprised with the contact to Paul in S.A. pretty dam good I think for 1.5 metre vertical antenna.
On 20m 14.285 MHz I worked Andrew VK1MBE 59 S2S and a nice surprise Tony VK3CAT S59 R58. A couple of times Mike VK6MB broke through the noise but not long enough to make a contact. Again it’s not a 1/2 wave dipole but you would have to agree it is an interesting antenna with a few surprises.
Oh I should also mention I started the activation on 2m and worked the local VK1 SOTA crew, Andrew VK1MBE S2S, Mark VK1MDC, Ian VK1DI, Al VK1RX and James VK1DR.
Final note, I will experiment at home using a 4 element ground.