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G8MNY > TECH 19.02.19 12:12l 116 Lines 5690 Bytes #999 (0) @ WW
BID : 59659_GB7CIP
Read: GUEST
Subj: QRO v QRP
Path: IW8PGT<IR2UBX<F1OYP<ON0AR<GB7CIP
Sent: 190219/1008Z @:GB7CIP.#32.GBR.EURO #:59659 [Caterham Surrey GBR]
From: G8MNY@GB7CIP.#32.GBR.EURO
To : TECH@WW
By G8MNY (Updated Apr 14)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
For years I have run as much QRO as I could muster. The main reason of course
is to be heard as far as possible & increase the chance of working that Dx, or
even having a contact at all. Also having a very small footprint with QRP can
mean your constantly fighting to keep your frequency on a busy band.
SIMPLE MODEL
Here is a simplistic statistical view of what power does in terms of range,
area covered, & hence the chance of a QSO, (based on +6dB = to double the range
& 4x the area of RF).
Power 1.5W 6W 25W 100W 400W 1500W
.Ä~~~~Ä. /
.' '. |
_--_ / \ Ż
-- / \ Ž Ż Ž
o () ( ) ( ) ( ) ³
-- \ / Ž Ż Ž
~--~ \ / Ż
'. .' |
~ś.,,.ś~ \
Range 1 2x= 2 2x= 4 2x= 8 2x= 16 2x= 32
Area 1 4x= 4 4x= 16 4x= 64 4x= 256 4x= 1028
S meter(3dB/Div) S1 S3 S5 S7 S9 S9+6dB
QSO Chance:1.5W 100% 400% 1600% 6400% 24000% 102000%
Chance:400W 0.4% 1.6% 6.4% 25% 100% 400%
CHANCE
Now chance is strange thing & much Dx is worked with QRP, often due to the
extensive endeavour of keen QRP operators.
With HF of course there is multiple hops & this model will show step skip
effects too (rings of skip "NO GO" & "GO" etc). Noise QRN @ Rx end & QRM from
other station or modern electronics QRM, all impinge greatly on the contact
chance.
At VHF the curvature of the earth can be a limiting factor.
BEAMS
By increasing the ERP with a beam, the range is increased, but not generally
the footprint area. That depends on stack/bayed configuration. (less lost into
space etc.) The actual chance of a contact therefore is often not increased,
but the amount of Dx is!
QRO HOGGS
Of course it is worth saying, if all were to run QRO, the bands will be jammed
with signals, Lots of Rx overload effects (& NB in) & some Tx splatter. So the
number of total QSO might well decrease! To avoid Tx splatter linears should be
properly 2 tone tested. Due to the underun exciter PA used when driving a high
power PA, with a good PA with some reserve, the result can actually be a
cleaner signal than the exciter at full power!
QRO ALIGATORS
Not being able to Rx weak signals well, while running QRO, greatly cuts down
the contact chance, to just those also running QRO !! So a QRO station should
endeavour to have a better than average Rx set up.
NOISE FLOOR
Here I use a 2nd Noise cancelling aerial with JPS ANC-4 to give 2-3 S points
improvement, as well as Noise Eliminating BHI DSP LS for typically a further
12dB noise reduction.
ASYMMETRIC QSOs
Often an asymmetric QRO to QRP contact is possible, where a dual QRP QSO would
be unlikely due to both weak signals with QRN & QRM at each station!
A good one way path makes all the difference & corrections needed in the weak
direction get through much quicker.
See my Tech bul "Stacking, Baying or Boxing Ant","BHI Noise Eliminating DSP LS"
SB ATV @ WW
Radar Clipper for 23cms
By G8MNY (CQTV 1994, New to packet Feb 06)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
This circuit was developed to limit the large negative pulses from radar QRM on
23cms ATV that are recovered video from a NE564 demodulator (or symular). These
pulses had been effecting the video amp DC levels, resulting in short periods
of no sync. The use of negative clipper after the de-emphasis network was not
used as that would allow the radar pulses to damage the video syncs, by
integrating them with the syncs before the clipper.
Using a complementry circuit (Inverted e.g. a T1=PNP, diode reversed, & the
330ź & 220k to the other power rails) will give a peak white clipper circuit.
ŚÄÄÄÄÄÄÄĀÄÄÄÄÄÄÄĀÄÄÄÄÄÄÄÄÄÄÄÄÄĀÄÄÄÄÄÄĀÄÄ+11V Reg
2k2 ³ 22k ³ ³
ĆÄ´ĆĀ´ĆÄ´ ³ 10n SYNC ³_ ³
Centre_ ³ u1Įu1 ³ ĆÄ´Ćæ CLIP ³/| ³
Freq |\ ŚÄÄÄÄĮÄÄÄÄÄÄÄĮÄÄÄÄÄÄÄĮÄæ Į LEVEL 220k ³
1-10pŚ´ĆÄÄ´13 2 1 10 ³ RV1 / ³ ³
ĄÄÄÄÄ´12 NE564 FM DEMOD ³14 ³ ³/
IF>Ä´ĆÄÄĀÄÄ´6 7 3 11 8 4 5 ĆÄÄÄ1kÄÄĀÄÄÄ)ÄÄÄÄ´T1
38MHz 1n 1k ĄÄÄĀÄÄÄÄĀÄÄĀÄÄĀÄÄĀÄÄÄĀÄŁ _³_ ³ ³\e____\ Video De-emphisis
ĄÄÄÄÄÄÅÄ1kÄĮ´Ć´ ³ ³4n7³ D1/_\ ³ R1 ³ / & Sound
n47=== 1n³ ³ === ³ +ĆÄÄÄĮÄ10kÄÄ´
³ ³ ³ ³ === ===C1 330
2 470 ³ ³ ³68p ³10u ³
ÄÄÄÄÄÄÄÄÄÄÄÄĮÄÄÄÄÄÄÄĮÄÄĮÄÄĮÄÄÄĮÄÄÄÄÄÄÄÄÄĮÄÄÄÄÄÄÄÄÄÄĮÄÄÄ
Clipping in the buffer before de-emphasis was more effective. The effect of
loosing the sound subcarrier during radar clipping was un-noticeable.
The circuit takes the average buffered DC video level with R1 & C1. RV1 is used
to just get D1 to clip the high impedance base signal, when a white picture is
present by adjusting VR1.
Why don't U send an interesting bul?
73 de John G8MNY @ GB7CIP
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