F.S. National Comapny S meter
sparky
National radios.
price is $25.00 plus shipping.
<a href="http://s820.photobucket.com/albums/zz123/sparky12x/?
action=view¤t=DSCF0011.jpg" target="_blank"><img src="http://
i820.photobucket.com/albums/zz123/sparky12x/DSCF0011.jpg" border="0"
alt="National Meter 2"></a>
Kenneth Scharf
Or did National design it that way because they had a backwards meter
circuit that pulled full current with zero signal?
sparky
>
> Why is the meter 'zeroed' against the right peg, is it broken?
> Or did National design it that way because they had a backwards meter
> circuit that pulled full current with zero signal?
This is a backward meter by National. The meter deflects left when
current flows.
Kenneth Scharf
Guess one could design a proper solid state amplifier to make it work,
but you'd have to 'zero' the meter at full scale with no signal.
sparky
http://www.universal-radio.com/CATALOG/commrxvr/HRO60.html
it has a meter with the zero on the left.
Kenneth Scharf
radio with no signal.
Weird. I'm going to have to find the schematic to the HRO and figure it
out.
Kenneth Scharf
MRe
"sparky" <spar...@yahoo.com> schreef in bericht
news:dc091fd8-d03a-4786...@s31g2000yqs.googlegroups.com...
See this picture HR)-60
http://www.universal-radio.com/CATALOG/commrxvr/HRO60.html
The AR88 had also a meter with the zero left (when there was a
meter anyway, because many had no meter at all)
It measured the cathode current of one of the IF tubes. (Less
amplification/cathode current means more signal). That leads to
the
somewhat odd 'zero right' configuration
MRe PE1NQr
Kenneth Scharf
(http://www.portabletubes.co.uk/sitefiles/hro1259.djvu), it seems the s
meter is in series with the plate circuit of the last IF stage, so it
measures the plate current. At maximum signal the plate current of that
stage must be close to zero to send the meter to the 60 over nine position.
terryS
> "sparky" <sparky...@yahoo.com> schreef in berichtnews:dc091fd8-d03a-4786...@s31g2000yqs.googlegroups.com...
>
> - Show quoted text -
Not sure one can understand the dilemma!
Lets say the meter is typically in the plate circuit of one or several
RF or IF amplifying tubes.
When the set is active and with no signal, the meter deflects (from
right to left). That type of meter is often called a 'Right zero'
meter).
When a signal is received a negative AVC voltage is generated; applied
to the grid circuits of the amplifying tubes their plate current is
reduced. The stronger the signal the greater the AVC voltage and ergo
the greater the reduction in plate current.
Hence the meter swings towards the right (or zero) in proportion to
the strength of the received signal.
Kenneth Scharf
this kind of S meter circuit, fine. When I saw that S meter I thought
it would look 'cool' in a (solid state) QRP rig I was planning. But,
I'd have to come up with a 'bass-ackwards' meter circuit to make it
work. I suppose that the meter should end up in another HRO or similar
receiver that needs a replacement though.
Scott Dorsey
>this kind of S meter circuit, fine. When I saw that S meter I thought
>it would look 'cool' in a (solid state) QRP rig I was planning. But,
>I'd have to come up with a 'bass-ackwards' meter circuit to make it
>work. I suppose that the meter should end up in another HRO or similar
>receiver that needs a replacement though.
The reverse-movement meters are WAY more expensive and hard to find than
typical meters. If you want a cheap movement for a homebrew QRP rig,
check out Fair Radio... they always have something interesting and
inexpensive, often with a weird scale marked "roentgens" or something.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."