S Meter Reading after Service

Joseph Rodick

Mike-VA3MW

Joseph Rodick

Burt Fisher

My S-meter does the same thing. Dummy load, S-7.

Mike-VA3MW

So, at 50 HZ bandwidth you see about S4?

Joseph Rodick

between 4-4.5 with the antenna connected or SHORTED.

Joseph Rodick

Just did a complete reset, at 50 HZ, the S meter is now reading 2.8-3 with or without the antenna connected or even with the antenna input shorted.  However SSB still at 5-6 and CW at 250 HZ 4-4.5.

Mike-VA3MW

Joseph Rodick

I have read and re-read all those posts.  However, with or without pre-amp on/off, bias on/off, the antenna connected or not connected or shorted.  I get the same readings that I have previously listed to you.   I also went over to a friends house that has an HP Spectrum Analyzer.  When you short or disconnect the antenna on the HP, the readings drop to zero or close to zero, THEY DON'T STAY THE SAME.  How can a Spectrum Analyzer such as FLex or HP read the given spectrum with a discounted or shorted input?  The answer I would give is that it can't.   So why is my FLex acting like this?

Lawrence Gray

Pat N6PAT

Joseph Rodick

Even with a Shorted HF input? P.S>  Where do you live?  Love to meet.

Joseph Rodick

I used to have a low S meter reading, then somewhere along the line, I have this.   I sent in my Flex for this issue and spent $79.95 for shipping and insurance and got it back with the same issue.

Bill -VA3WTB

Bill -VA3WTB

You must have a 6400 or 6600? It may be a good idea to contact support again and have them run a few test with you, Just don't leave it this way, contact them if you feel the Smeter is not working.

Michael N3LI

Lawrence Gray

I live in Falmouth, MA.  

Rick WN2C

Mark K1LSB

Joseph Rodick

Thank you for your input, but I am confused, with the antenna input either shorted or disconnected I get the same S meter reading.  With the bias, or pre-amp turned on/off, i still get the same S meter reading.  So is that a reflection of internal Flex 6400M noise rather than the band conditions?

Joseph Rodick

I am not a professional in the field, even though I taught electronics for Sears and STAC years ago.  However, How can any Flex owner give a signal report with these readings?  Right now I have my Flex on 40 meters with the antenna input shorted and I have an S meter reading of 5.5.  So do I give the short an S5 report?  I apologize if anyone thinks I am being facetious, but if I am looking at my S meter, that would be the report.

Paul_Mills

In my way of looking at this, it is not right. If was me I would submit a new support ticket, and insist on resolution. That being said, it is possible that the problem did not present itself while at Flex.

Joseph Rodick

I wrote a detailed report on this issue regarding the S meter and poor weak signal receiving.  I printed two copies that I put one in the box and one on the Flex.  The report from Flex is that they did a pin update.   I am frustrated that I received it back with the same issues.  Flex is saying that the S meter readings are normal.  So either I except this or decide to sell.   Thank you for your input and God Bless.

Bill -VA3WTB

There seems to be a little confusion. Of course you would not give someone your S meter reading that you have without an antenna.

The signal at the antenna port are directly digitally sampled, the samples are converted to v. = S meter reading.

It is important to understand, in a Flex things like AGC settings will not effect the S meter readings, all DSP settings are also byepassed because the signal sampleing is direct from the antenna port. In a conventional radio the S meter is in the AGC circuit, depending on how the AGC is set effects what the S meter says. If there is any AGC pumping, the S meter is all over the place. In a conventional radio the S meter is only ball park figure.

But when an antenna is connected to the Flex radio the bin sampling does not make the S meter hold at S4 or what ever you see without the antenna conected.
Some people thing that because the S meter says S5 without the antenna then when an antenna is connected the meter can't report anything less then S5.
It does not work that way. When an antenna is connected the receiver can hear to the noise floor and below. The meter will show all the way down to the noise floor what ever that is at the moment. If for example your noise floor is S3, then that will be shown on the S meter as well when no signal is present.

Ned K1NJ

   Please take this as a simple comment, not as an analysis.

If -internally- the external connector is not connected to the input circuitry
you will see the kind of behavior you describe.  That is, connecting,
disconnecting, even shorting the external connector will have no effect.
Switching selectivity settings will have a predictable effect however
since this is happening after the RF input stages.

I had a Flex 5000 that got its input board zapped by a nearby lightning
strike.  It did similar things.

    Hang in there,
                             Ned,  K1NJ

FISHULA X

I own a 6300. Get this. with no antenna connected, listening at 4 KHZ wide
 I get an S3. with RF gain off.  And with the RF gain on I get an S1 and a quarter..
 That's a head scratcher??? Anyone else?????? 

Joseph Rodick

KY6LA_Howard

Actually it makes perfect sense 

if it’s reading S5 then your radio is only capable of receiving -127dBm +5x6dBm = -97dBm at that frequency. 

Legacy S meters measure the AGC voltage not the signal received.  Basically a Fake News analog for some mythical reading. 

It’s almost the 2nd decade of the 21st century so I only give dBm reports 

Andy M5ZAP

Excellent descriptions by Bill and Howard. I think I’ve got my head around it now. But like others I have struggled. Are there any flex articles or other literature that make good holiday reading which cover this and other SDR theory in a way a non expert can understand.

Joseph Rodick

Burt Fisher

I put a dummy load on the input, S6. I put an antenna on the same frequency using a KX3, S2, with the dummy load S0 on the KX3.  It isn't noise, Flex uses their own way to set the S-meter no one else uses.