Gordon,
Good to see you are making positive progress.
Re:- the before & after figures
I don't know the Icom 718, as a background just in case someone else
tries to repeat your tests. It's normally quoted as 6dB per S point.
Pretty much all radios will be different. Its a repeatable test to
the same reference value on the meter on the same radio but not
necessary beyond that, the meter reading may be non-linear etc.
Alison suggested the stepped attenuator approach to bring the
fundamental down to the same indicated level on the meter as the
harmonic, the amount of added additional attenuation indicates the
harmonic reduction.
The measurement accuracy is then transferred to that of the
attenuator,? and is more easily characterised.
It is also transferable to other peoples measurements regardless of
method, by radio or a spectrum analyser etc.
Can Alison comment?
Alan
On 29/08/2018 03:24, Gordon Gibby
wrote:
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Able to charge that battery significantly and proceed with tests.
All of these have a homebrew 50 dB tap on a Heathkit Cantenna, and
then a 20dB attenuator at the input of the ICOM 718.? ?Previous
measurements have suggested that between S7 and S9,? ?an S unit is
approximately 12 DB.
Presented witll be the BEFORE/AFTER? ?S unit measurements where
before is the relatively STOCK uBitx and the AFTER is is with my
external daughterboard, with basically unshielded wiring.
All measurements are for CW (because this is where the unit had
the most problems)
Power is estimated from a Micronta cheap SWR/power bridge built
for CB'ers many many years ago.??
FREQ? ? ? PWR? ? ? ?FUNDAMENTAL? ? ? ?2ndHArmonic? ? 3rdHarmonic?
?4thHarmonic? ? 5thHarmonic? ? ?6thHarmonic? ? ?7thHarmonic
3.505? ? 5 W/5+W? S9+30/S9+30? ? ? ? ? ?S7.5 / S7? ? ? ? ? ?S8.5
/? S6? ? ? ? S0 /? ?S0? ? ? ? ? ?S8 /? S1? ? ? ? ? ? S0 / S0? ? ?
? ? ? ? S8.5 / S8? ??
(so on 80 meters, the 3rd and 5th harmonics were greatly
attenuated, and the 7th lost maybe 6 db)
7.005? ?2.5/3.5W? ?S9+30/S9+30? ? ? ? ? ?S0/ S0? ? ? ? ? ? ? ?S8.5
/ S7? ? ? ? ?S5.5*/S0? ? ? ?*=wavering
(so on 40 meters, harmonics went? down by huge amounts
9.995? ?1.5/1.5 W? S9+30 /S9+30? ? ? ? ? S0 /S0? ? ? ? ? ? ? ?S9 /
S5 or less
(so on 30 meters, the 3rd harmonic was basically demolished)??
In previous testing on 14 MHz, I cant go any farther than the 2nd
harmonic and it was S0 (no reading) so not much for me to work on
profitably there...and that is the filter that I damaged.
This looks overall, like a huge success.? ?The only oddity is the
7th harmonic of the 80 meter signal (why??)? ?but even it may be
down 42 db.? ?On these bands, my crude testing indicates that even
CW now either passes with flying colors or is very very close to
it.? ?If I shield or even twist a ground around the INPUT (red in
the photographs) wire it may get better.
Cheers,
Gordon Gibby
Alan de G1FXB