1
$\begingroup$

Can we expect a Loop Antenna such as a Chameleon F-Loop Antenna transmit and receive from the USA's midwest to Australia on HF using an average 100 watt SSB transmitter and an average receiver?

If so, on what bands might this be possible?

$\endgroup$
  • 3
    $\begingroup$ This question cannot be answered without more detail: you need to specify the performance characteristics (power, sensitivity) of the transmitter and receiver, what band you would be using, and what probability or time window of success is acceptable. (Once you have this information, a link budget calculation and possibly ionospheric simulation tools can get you a fairly solid answer.) $\endgroup$ – Kevin Reid AG6YO Jan 23 '18 at 23:21
  • 1
    $\begingroup$ I have a good answer for this which now I can't post. I do not think power and sensitivity of the transmitter / /receiver are relevant. 100w to 1w could work fine with typical transceivers. However, the title (10 miles) does disagree with the body of the question.) $\endgroup$ – user10489 Jan 23 '18 at 23:32
  • 2
    $\begingroup$ The title disagrees with the body of the question, and there is simply not enough information in the question to allow a good quality answer without many assumptions. $\endgroup$ – Scott Earle Jan 24 '18 at 2:30
  • 2
    $\begingroup$ The question should probably read 10k miles. $\endgroup$ – Glenn W9IQ Jan 24 '18 at 16:46
2
$\begingroup$

Very unlikely. 100W SSB over 9,000 miles is already a challenging path, but these antennas are very inefficient which will make it nearly impossible. Let's simulate with VOACAP.

enter image description here

This is 100 W SSB, with 0 dBi antennas at each end, and a quiet noise floor. If the receiver is near a city, man-made noise will make the situation much worse.

Your best chance is on 20 meters, at 2100 UTC, where the circuit reliability is 23%.

0dBi is a very generous estimate of that antenna's gain. Unfortunately VOACAP doesn't offer a worse antenna to simulate.

However, turning the power down to 10 W is a 10 dB reduction. If we are considering each end of the link to have one of these loop antennas, that makes this case equivalent to a -5 dBi antenna.

enter image description here

Now at best, circuit reliability is 8%.

I think -5 dBi is too optimistic for this antenna. Turning down the power to 1 W is equivalent to a -10 dBi antenna on each end:

enter image description here

Now your best shot is down to 2%.

Of course, these are simulations for today. We're currently at a low spot in the solar cycle, but in a few years conditions will be better. Not better enough to enable reliable communication over this path all the time, but perhaps enough to make it worthwhile to try. You can play with the simulator parameters for all kinds of scenarios.

If you did want to communicate over this path, with these antennas, a more sensitive mode will make it feasible. CW or PSK31 would be better, JT9 would be better still. With JT9 and a little luck, you could probably make a contact.

$\endgroup$
  • $\begingroup$ "a more sensitive mode will make it feasible." Absolutely! $\endgroup$ – Mike Waters Jan 24 '18 at 20:24
2
$\begingroup$

The short answer is rarely, if at all on SSB.

STLs are notoriously lossy, since their radiation resistance is in the milliohm range. The best ones are made from large copper tubing, vacuum variable capacitors, and heavy copper straps connecting the two to minimize the I²R losses. And those losses need to be MUCH less than the radiation resistance.

This type of STL has neither. It's so lossy, that exceeding its rated power limit can heat it up to the point where it is either damaged or destroyed. I'm not saying it's worthless, but I believe that your money would be better spent on a better antenna for the purpose you mention. A tribander is your friend. :-)

Owen Duffy has some information on that antenna:

... Chameleon’s published VSWR curve reconciles reasonably with the realistic NEC-4.2 model and analysis of it suggests radiation efficiency on 20m is around 4%. ...

(He has much more information on his site about how lossy STLs are.)

You would have a far better chance using a dipole or vertical than any STL. Even then, it would have to be 20 meters or above. And during this low part of the sunspot cycle, those bands are rarely open.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.