We seek to understand and document all radio transmissions, legal and otherwise, as part of the radio listening hobby. We do not encourage any radio operations contrary to regulations. Always consult with the appropriate authorities if you have questions concerning what is permissable in your locale.


Offline ChrisSmolinski

  • Administrator
  • Marconi Class DXer
  • *****
  • Posts: 24582
  • Westminster, MD USA
    • View Profile
    • Black Cat Systems

In the FlexRadio Community a poster complained that his Flex-6700 reported S-2/3 noise most of the time.

He wanted his radio to “Whisper Sweet Nothings” report S-0 if disconnected from an antenna – basically setting aside the noise the sensitive Flex-6700 was actually hearing.

He never disclosed if his feedline and antenna switches were still in line, if they were grounded when antennas were deselected, or whatever other RF his radio was experiencing.

He also didn’t tell the community if he had his Flex-6700 narrowed down to a specific frequency, opened wide in a wide band receiver configuration, or how his radio was configured.

“He” is actually several posters who have some been part of this discussion before, some new to FlexRadio, and all who hadn’t looked for older threads on the issue.

Full article: https://k9zw.wordpress.com/2019/08/12/s-meters-comfortable-lies-or-accuracy-the-whisper-of-sweet-nothings
Chris Smolinski
Westminster, MD
eQSLs appreciated! csmolinski@blackcatsystems.com
netSDR / AFE822x / AirSpy HF+ / KiwiSDR / 670 ft horizontal loop / 500 ft northeast beverage / 58 ft T2FD / 120 ft T2FD/ 300 ft south beverage / 43m / 20m / 10m  dipoles / Crossed Parallel Loop / Discone in a tree

Offline Josh

  • DX Legend
  • ******
  • Posts: 3815
    • View Profile
I try to have the hf rigs set to register s0 on a quiet band. That almost always means no preamp in operation. Most recent rigs, sdr and otherwise, can hear down to at least -125dBm in a ssb bandwidth sans preamp, -125dBm is about the point where qrm and qrn are nominal in a semi-urban environment.

If you like to see agc action on band noise, you're reducing dynamic range when all you really needed to do was to turn up the volume rather than activate the preamp.

The real test is if you disconnect and reconnect the antenna and it makes a difference in noise output. If it does, that's all you need as far as sensitivity.
We do not encourage any radio operations contrary to regulations.

Offline skeezix

  • Global Moderator
  • DX Legend
  • *****
  • Posts: 3809
  • Minneapolis, MN
  • What does 'RNO stand for?
    • View Profile
The S-Meters on my National tube radios are liars. They don't even hide it, they flaunt it. Taunting those that watch.

The NC-183D is the biggest liar of all, but with its push-pull 6V6 output tubes producing their siren song, I am lulled into aural bliss and adjust the RF gain to where I think the meter should be.

Minneapolis, MN

Offline BoomboxDX

  • Hero Member
  • *****
  • Posts: 663
    • View Profile
I have never had use for them. A lot of reporting is subjective, be it the signal reports hams use (perennially "you're 5 and 9") or the SINPO / SIO reporting standards, which are more based on how loud the signal was, and what quality it was, as well as the propagation.

The only time I really used S-meters were when I was into CBing, where S-meters seemed to be more or less standard across the board -- at least when compared to SW and MW radios and comm rigs.
An AM radio Boombox DXer.
+ GE SRIII, PR-D5 & TRF on MW.
The usual Realistic culprits on SW (and a Panasonic).

Offline Josh

  • DX Legend
  • ******
  • Posts: 3815
    • View Profile
Most HAM rigs of recent make (last 30 years) have a fairly linear smeter and are decent enough measurement tools for relative readings. My current crop of HAM rigs have smeters that can be used to indicate dBm as their response is characterised. Some sdrs also have more or less calibrated smeters, the RSP series is almost a lab instrument in that case.
We do not encourage any radio operations contrary to regulations.

Offline ThElectriCat

  • Full Member
  • ***
  • Posts: 104
  • Hillsboro OR
    • View Profile
probably going to get yelled at for mentioning my favorite receivers, but...
Watkins Johnson receivers, have s meters that are somewhere in between log and linear scale, and are extremely useful for setting the RF gain manually, but I am pretty sure thats what they are for. I can't really find a better way to use them. some of the clearest signals I can hear barely deflect them, and some of the worst do.
In another life, I could have been a telephone engineer.