Many thanks to SWLing Post contributor, Jack Dully, who writes:
I am just wondering what portable receivers are more susceptible to overloading with long dipoles, say 60-70 ft.
I regularly use such and I have never noticed anything unusual happening with a Sony ICF-7600GR, Grundig G3, or PL-880 to name a few. I just ordered a Tecsun 680. Perhaps many of the newer radios have better AGC thresholds or more robust front ends but I really don’t know for sure.
[Also] how exactly do you know if your receiver (portable OR not) is being overloaded by too big of an antenna (ie. dipole, inverted V and the like) and will it damage your receiver? Is there still a way of using a large antenna to capture more distant stations safely, especially with good quality portables?
Thank you for sharing this question, Jack, and my hope is that SWLing Post readers can chime in with details and advice in the comments section of this post.
These are deep topics, but I’ll try to answer a few of your questions…
First of all, you definitely can harm a portable radio by hooking it up to a large antenna. Many portables have no means of protecting themselves from ESD (Electrostatic Discharge). By hooking a portable up to a long wire antenna, you can expose it to ESD which will essentially deafen your radio until you’re able to repair it. Indeed, this reminds me of an article from our archives regarding a Tecsun PL-600 ESD repair. Some radios do have built-in ESD protection (like the PL-680), but I’m not entirely sure it would offer protection from a particularly strong ESD pulse.
Symptoms of overloading can vary. Sometimes overloading can sound like background splatter and even popping. Sometimes you’ll hear “images” of broadcasters across the bands; muffled audio of a blowtorch station. Another sign of overload is when your signal meter jumps at the same time your receiver goes deaf. It’s as if your radio is simply overwhelmed by strong signals and it can manifest itself in odd ways especially since the AGC usually falls apart.
Like you, I’ve found that my Sony ICF-7600GR seems to be able to handle large wire antennas with no discernible overload. Also, the Tecsun S-8800 (above) is well-equipped to handle larger external antennas and even sports a proper antenna port on the back. I know Sangean ATS-909X owners who only use their radio with an external wire antenna and have excellent results.
Some portable radios are very sensitive with the built-in whip antenna, but fall apart if attached to a long wire antenna.
In general, the cheaper the radio, the less likely it has a front end and filtering that can cope with overloading.
Please comment with your experience regarding overloading. Have you found some radio models better than others at coping with blowtorch stations, for example? What do you do to protect your receivers from electrostatic discharge when hooked up to large antennas? Please comment!