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G8MNY > TECH 13.01.17 11:55l 81 Lines 3825 Bytes #999 (0) @ WW
BID : 31463_GB7CIP
Read: GUEST
Subj: QRO v QRP
Path: IW8PGT<IR2UBX<SR1BSZ<LU4ECL<GB7CIP
Sent: 170113/1052Z @:GB7CIP.#32.GBR.EURO #:31463 [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. /
.' '. |
_--_ / \ Ý
-- / \ Þ Ý Þ
o () ( ) ( ) ( ) ³
-- \ / Þ Ý Þ
~--~ \ / Ý
'. .' |
~ú.,,.ú~ \
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"
"AF 2 Tone Test Osc Design". "QRO Dummy Loads" & various PAs.
Why Don't U send an interesting bul?
73 de John G8MNY @ GB7CIP
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