[Heath] Fw: SB-102 S-Meter operation

[Glen Zook]

Methinks a typo!  The cathode resistors in the SB-102 are 10-ohms and not 20-ohms.


As for the "S" meter reading:  You need to check the sensitivity of the receiver portion and the "S" meter reading using a signal generator with an accurate attenuator.  A signal level of 50-microvolts is the EIA standard for S-9.  Many of the Japanese units have "S" meters that are definitely not calibrated to the standard and also are no where being accurate in the "dB over" range.


The Japanese manufacturers got into a "war" a number of years back with each claiming that their receivers were more sensitive than the other manufacturers.  What they actually did was to reduce the signal strength needed for S-9 and eliminate a true dB over reading.  As such, those units read considerably higher for the same signal level than those S"S meters calibrated by the ol EIA standard.


All my "S" meters are calibrated for S-9 = 50-microvolts and I have an above average antenna array.  Often, signals do not even reach S-9 and it takes a local to achieve a 20 dB over reading.  An operator, who lives 5-blocks from me and who runs a Heath SB-200 amplifier, often doesn't even make it to a 40 dB over level.  But, way too many operators these days are used to getting a minimum of S-9 and often "20 dB over" to even as much as "60 dB" over and are insulted if you give then less than an S-9 reading.  Therefore, I generally resort to the system that we used when the majority of receivers did not have an "S" meter.  If the station is in the clear and strng enough to easily copy, there are an S-9.

 Glen, K9STH absite: http://k9sth.net

      From: Joseph Smalley via Heath <heath at puck.nether.net>
 To: "heath at puck.nether.net" <heath at puck.nether.net> 
 Sent: Monday, March 27, 2017 12:54 PM
 Subject: [Heath] Fw: SB-102 S-Meter operation
   


     On Sunday, March 26, 2017 10:54 PM, Joseph Smalley <mymodecw-hamitup at yahoo.com> wrote:
 

 
 Hello to the group.  I still use my SB-102 that I built in 1972,  I have two issues I want to fix.
Number ONE is the poor operation of the S-meter very rarely does the S-meter give a good reading
even on real strong signals.  A fellow ham close by gets a pinned needle on my TS-530sp on the
Sb-102 it will be S9. Most stations I work have a loud signal but low reading on the S-meter. Never S9

 I have put new 6AU6 I.F. amplifier tubes in the radio no help.  Replaced the Product detector/AVC tube, no help
Any ideas will be appreciated.
Number TWO sometimes the resting (idling) plate current will increase above the set value of 50 MA, this happens
when I get long winded CW only here. 

I recently repaired a SB-100 for a friend that had an excessive plate current reading which turned out to be
the cathode resistors on the final amplifiers.This is not what I am experiencing.  The reading was  3 ohms for the 

six 20 OHM resistors in parallel, when I replaced the resistors  the reading went to 1.6 OHMS which I measured
on another properly working SB-102.
Any info will be appreciated.
73 Joe WA3CKA 

   
 Hello to the group.  I still use my SB-102 that I built in 1972,  I have two issues I want to fix.
Number ONE is the poor operation of the S-meter very rarely does the S-meter give a good reading
even on real strong signals.  A fellow ham close by gets a pinned needle on my TS-530sp on the
Sb-102 it will be S9. Most stations I work have a loud signal but low reading on the S-meter. Never S9

 I have put new 6AU6 I.F. amplifier tubes in the radio no help.  Replaced the Product detector/AVC tube, no help
Any ideas will be appreciated.
Number TWO sometimes the resting (idling) plate current will increase above the set value of 50 MA, this happens
when I get long winded CW only here. 

I recently repaired a SB-100 for a friend that had an excessive plate current reading which turned out to be
the cathode resistors on the final amplifiers.This is not what I am experiencing.  The reading was  3 ohms for the 

six 20 OHM resistors in parallel, when I replaced the resistors  the reading went to 1.6 OHMS which I measured
on another properly working SB-102.
Any info will be appreciated.

   
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://puck.nether.net/pipermail/heath/attachments/20170327/ce3e4419/attachment-0001.html>