Can Solar activity effect a receiver’s selectivity or sensitivity?
Solar Activity
- Thread starter jmumford
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For a broad answer, if you are talking about the overall system, yes. What specifically are you observing on the receiver end or what specific nugget of information are you looking to get an answer for?
Receiver specifications, when isolated from the environment in a Faraday Cage test setup, can be quantified. However, what you hear coming out of the speaker in a typical scenario with an outside antenna can be different. “Funny things” can happen inside the receiver given a strong enough signal, whether it be manmade or Sun induced. The circuits responsible for receiver selectivity and sensitivity can be “overpowered” causing unwanted side-effects that manifest themselves in apparent receiver selectivity and sensitivity changes.
Did the receiver specs change? Not really as long as the circuits did not get “blown out” by the strong unwanted signals. But when overdriven into saturation and beyond, for example, circuits may not perform as designed resulting in apparent changes to receiver selectivity and sensitivity.
Hopefully, that made some sense and can be visualized. Circuits that are subjected to stimuli outside of their design parameters generally do not respond as designed. Simply put, envision plugging a 110 VAC device into a 220 VAC circuit. It probably will not perform twice as good. 😳
Receiver specifications, when isolated from the environment in a Faraday Cage test setup, can be quantified. However, what you hear coming out of the speaker in a typical scenario with an outside antenna can be different. “Funny things” can happen inside the receiver given a strong enough signal, whether it be manmade or Sun induced. The circuits responsible for receiver selectivity and sensitivity can be “overpowered” causing unwanted side-effects that manifest themselves in apparent receiver selectivity and sensitivity changes.
Did the receiver specs change? Not really as long as the circuits did not get “blown out” by the strong unwanted signals. But when overdriven into saturation and beyond, for example, circuits may not perform as designed resulting in apparent changes to receiver selectivity and sensitivity.
Hopefully, that made some sense and can be visualized. Circuits that are subjected to stimuli outside of their design parameters generally do not respond as designed. Simply put, envision plugging a 110 VAC device into a 220 VAC circuit. It probably will not perform twice as good. 😳
Just wondering about intermittent interference that seems to coincide with reported solar events.
What type of interference and what band(s) are you observing this on? Can you try to describe what it sounds like or post an audio clip? Is it on one frequency in a given band or multiple frequencies? Broadly speaking, solar activity can cause the noise floor (ie background noise level) to increase and decrease. As an example, I have noticed increased background noise during periods of poor propagation conditions on the HF bands (3 - 30MHz)
I listen to the railroads on VHF 160 to 162.
There is a type of propagation called Tropospheric Ducting, which can make it possible for you to hear VHF and UHF signals from hundreds of miles away. It's relatively common during the Spring and Summer months, and primarily affects frequencies above 90 MHz. Since you are listening to railroad on VHF-high, it's possible that signals from distant stations are interfering with the locals you are listening due to Tropospheric Ducting.
One somewhat reliable way to see if distant stations are coming in is to scan the weather band. If you hear weather stations for distant towns and states, there is a good chance there is Tropospheric Ducting going on.
Here is a good introductory thread on the topic:
New to tropospheric ducting
I just want a basic explanation of tropospheric ducting and how it works from my understanding if it is high from my location to another location I could pick up radio signals from there. Also is there like some forecast map of tropospheric ducting?
Thanks!There is a type of propagation called Tropospheric Ducting, which can make it possible for you to hear VHF and UHF signals from hundreds of miles away. It's relatively common during the Spring and Summer months, and primarily affects frequencies above 90 MHz. Since you are listening to railroad on VHF-high, it's possible that signals from distant stations are interfering with the locals you are listening due to Tropospheric Ducting.
One somewhat reliable way to see if distant stations are coming in is to scan the weather band. If you hear weather stations for distant towns and states, there is a good chance there is Tropospheric Ducting going on.
Here is a good introductory thread on the topic:
New to tropospheric ducting
I just want a basic explanation of tropospheric ducting and how it works from my understanding if it is high from my location to another location I could pick up radio signals from there. Also is there like some forecast map of tropospheric ducting?forums.radioreference.com
The past week or so has had plenty of geomagnetic disturbances that have affected VHF and above. During a geomagnetic storm, my VHF reception range shortens to about 25 miles and introduces a lot of noise on the marginal stations.
RFI-EMI-GUY
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Even the best receivers have limited rejection of out of band signals. I encountered a commercial low band repeater that was designed around a mobile radio receiver and transmitter. I discovered that the manufacturer never tested spurious responses below 30 to 50 MHz, thus it failed TIA-603. in the field, when used as a repeater, the noise in the 100 watt amplifier was sufficient in the 17MHz range to desensitize the receiver. This despite the duplexer. I think the designer either figured that in mobile service that the antenna would not be resonant enough to conduct spurious responses. never mind that there are shortwave broadcasts in that range.
A good preselected filter can improve most receivers effective sensitivity.
Interesting. I remember the 2m repeater of the now defunct local amateur radio club I belonged to used a Maxtrac/GM300 for a receiver. Those were rock solid, even in the RF dense environment of the NJ/NYC metro area.
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Motorola could be relied upon to follow TIA-603D, Midland, not so much.
