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Re: 123MHz on FT-847


I Have calibrated my FT-847 S-meter at 144.1 MHz and it is non-linear!  I
get about 5 dB from S-0 to S-1 and less in other ranges.  For practical
discussions I have averaged it over S-0 to S-6 and come up with
4-dB/s-unit.  It would not surprise me find the FT-817 s-meter quite
different.  I do not rely heavily on it since it is simple lcd bar
meter...the FT-847 s-meter is more finely graduated. I get an est 18-20 dB
dynamic range on AO-40 which fits AO40_rcv2.0; I see a half s-unit noise
floor from the satellite that drops when pointed off the bird (low
squints).  My dish is 85cm offset fed with helix (25 dBic) and 0.6 dBNF
with 40 dB gain in the preamp.


At 07:18 AM 3/16/2003 -0600, Jon Ogden wrote:
>on 3/16/03 4:06 AM, Edward R. Cole at al7eb@ptialaska.net wrote:
>> Interesting comparison.  I haven't listened using my FT-817 so do not know
>> how it compares with my FT-847 at 123 MHz, but with the int. preamp off my
>> FT-847 noise floor is about s=0.5 when fed by my MKU-232A2 preamp into a
>> stock Drake-2880 (2401/123).  max beacon runs s=5.5.  I see no problem at
>> 123 with my FT-847.  Perhaps yours is in need of alignment?
>Hi Ed,
>I'm beginning to wonder if there isn't a problem with my 847.  But then
>let's run some numbers real quick.  There is where I'm having difficulty.
>If I turn my preamp off on my 847, I get very similar results to you.  So
>maybe I'm not too far off.  Admitedly, I'm going to have to make some
>assumptions here so this is not necessarily accurate:
>Let's assume on the FT-847 and on the FT-817 that each S unit is only 2 dB.
>If your range is 0.5 to 5.5, then you have a 10 dB total dynamic range on
>your 847.  This is similar to what I see.  On the other hand, what I see on
>the 817 is a range of 0 to 8.  This would equate to a 16 dB dynamic range.
>The only conclusions that I can think of that would say that the 2 radios
>still perform equally are:
>1.) There is a drastic difference between the two S-meters on each radio
>2.) The S-meters are not anywhere near linear and actually do not represent
>a constant "dB" change.
>I'll admit each of these is very possible.  I've been wanting to calibrate
>my S-meters on each rig so perhaps this is a good excuse to do so.  I know
>my conclusions here are unscientific at best.  And it seems to me that the
>way signals sound on the 847 just is not all that good.  But perhaps my
>hearing is biased because of the results I visually see on the meters....
>Jon Ogden
>NA9D (ex: KE9NA)
>Citizen of the People's Democratic Republik of Illinois
>Life Member: ARRL, NRA
>Member:  AMSAT, DXCC
>http://www.qsl.net/na9d   <- Updated on 1/22/03!!!
>"A life lived in fear is a life half lived."

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