3 ms·

The post mentions that he tried that and was not able to receive anything using a dummy resistive load.

mikepurvis 7y ago
Oh boo, I skimmed over that. Thanks for the clarification.
myth2018 7y ago
Indeed. But he didn't mention how he connected the dummy load to the radio. Dummy loads have usually a standard antenna connector and are meant to be attached directly to the radio or through an non-irradiating cable. So, my guess is that, by using the dummy load, he disconnected the actual antenna: the "dipole" made by the wires between the radio and the dessert
- anilakar 7y ago
  The custard probably mostly acts as a resistive load and mechanical support. Actual radiation happens in the wires.
curiousfab 7y ago
A few centimetres of unshielded wires are typically enough to receive some of the strongest signals on the amateur radio bands. If you are using such a short and therefore highly inefficient antenna, both the noise and the desired signal decrease significantly, but the signal may still stay above the noise floor. The statement in the article that the antenna tuner doesn't do much on receive is not correct. On a related note, radio hams were previously successful in establishing transcontinental contacts in Morse code using all kind of unusual antennas, including bed springs :-)
- myth2018 7y ago
  > If you are using such a short and therefore highly inefficient antenna, both the noise and the desired signal decrease significantly, but the signal may still stay above the noise floor. That doesn't apply to FT8 and some other digital modes. It uses signal processing techniques to receive signals below the noise floor.
  - curiousfab 7y ago
    My wording ("above the noise floor") was not well chosen. What I mean is simply this: Your receiver will have a certain noise floor which you will see/receive even without an antenna connected to it (internally generated by imperfect components). If you connect an antenna, this antenna has a certain "antenna factor" which describes how much of the field strength of a signal "in the air" will be converted an electrical signal at your antenna terminal. For a very short antenna, this factor is small, for a "good" antenna this factor increases. Assuming both your "bad" and "good" antennas are still good enough to pick up background noise and desired signals above your receiver noise floor (which is usually the case, even if you put your finger into the antenna terminal!), all you get is a difference in absolute signal levels while the SNR (ratio between the desired signal and the noise) will not change. So this principle is universal, independently of the modulation scheme.

Oh boo, I skimmed over that. Thanks for the clarification.

myth2018 7y ago

Indeed. But he didn't mention how he connected the dummy load to the radio. Dummy loads have usually a standard antenna connector and are meant to be attached directly to the radio or through an non-irradiating cable. So, my guess is that, by using the dummy load, he disconnected the actual antenna: the "dipole" made by the wires between the radio and the dessert

anilakar 7y ago
The custard probably mostly acts as a resistive load and mechanical support. Actual radiation happens in the wires.

curiousfab 7y ago

A few centimetres of unshielded wires are typically enough to receive some of the strongest signals on the amateur radio bands. If you are using such a short and therefore highly inefficient antenna, both the noise and the desired signal decrease significantly, but the signal may still stay above the noise floor. The statement in the article that the antenna tuner doesn't do much on receive is not correct. On a related note, radio hams were previously successful in establishing transcontinental contacts in Morse code using all kind of unusual antennas, including bed springs :-)

myth2018 7y ago
> If you are using such a short and therefore highly inefficient antenna, both the noise and the desired signal decrease significantly, but the signal may still stay above the noise floor. That doesn't apply to FT8 and some other digital modes. It uses signal processing techniques to receive signals below the noise floor.
- curiousfab 7y ago
  My wording ("above the noise floor") was not well chosen. What I mean is simply this: Your receiver will have a certain noise floor which you will see/receive even without an antenna connected to it (internally generated by imperfect components). If you connect an antenna, this antenna has a certain "antenna factor" which describes how much of the field strength of a signal "in the air" will be converted an electrical signal at your antenna terminal. For a very short antenna, this factor is small, for a "good" antenna this factor increases. Assuming both your "bad" and "good" antennas are still good enough to pick up background noise and desired signals above your receiver noise floor (which is usually the case, even if you put your finger into the antenna terminal!), all you get is a difference in absolute signal levels while the SNR (ratio between the desired signal and the noise) will not change. So this principle is universal, independently of the modulation scheme.