Everyone is suffering from high noise levels on the HF bands and at time the bands are unusable because of the high noise levels. Due to the design of modern transceiver’s and all the aerials in your garden are designed for receive and transmit, you switch between aerials for the best receive signal and use that one.
I presume that everyone knows that vertical aerials suffer from high noise levels followed by dipoles and the quietest aerial for noise levels, is the loop aerial and people tend to think of the magnetic loop. But wait the magnetic loop aerial has low efficiency!!!!! So What!!!!! That’s only on transmit it is a very efficient high Q receive aerial.
There is a lot of information available about aerials on the internet so instead of repeating what others have published I shall put links to already published articles.
RST & Signal Strength
Before carrying on about aerials and noise just a slight deviation to the RST report and the Signal Strength meter.
The “Signal Strength” meters or receivers or transceivers are only accurate if they have been calibrated at regular periods with a standard meter. (I worked on instrumentation at Ruston Research.) Personally I take the reading on my transceiver with a pinch of salt and do not rely on it.
Moving on to Readability, Signal Strength and Tone, which I also take with a pinch of salt. A station gives you an RST of 599 then asks you to repeat something; it can’t be you that’s bad as he has given you a 599 so it must be him who is the bad operator as he could have added QRN, QRM and QSB.
Noise and Signal Strength, this is the bothersome bit if the noise level is the same as the signal strength of the station you are working. You don’t need a meter to tell you, just use your ears.
This is where we start to think, how could we reduce the noise level and make the signal more prominent. If you can reduce the noise level by 2S points and even if the signal is reduced by 1S point, the signal now becomes more readable. How about having a low noise receive only aerial and switch between this and your main aerial when operating.
RF Sensing
I can hear the groans thinking about physically switching between transmit and receive aerials when conducting a QSO but Wait!!!!! Transceivers have a switching circuit involved in transmitting and receiving perhaps this circuit could be implemented in switching my aerials. Preamps have an RF sensing circuit, perhaps I could I build an RF sensing circuit to switch the aerials. (Perhaps someone could comment article on RF sensing circuits or know of a good circuit that would be of interest to everyone.)
Recieve Aerials
This link takes you to an article from “Technical Topics” column of the June 1986 edition of “RadCom” http://www.qrss.thersgb.net/G8CQX-Loop-antenna.html which is about a low noise active receiving loop aerial. This loop has been updated by Des (M0AYF) and can be found at http://www.qrss.thersgb.net/active-loop-receiving-antenna.html.
A good article on a magnetic receive only loop by Simone IW5EDI can be found at http://www.iw5edi.com/ham-radio/29/a-small-wire-loop-antenna-for-160-to-10-meters
