| |
VK3XX > MORSE 17.06.06 10:03l 80 Lines 4293 Bytes #999 (0) @ WW
BID : 531475VK3XX
Read: GUEST DF1GG
Subj: Re: KB2VXA> small survey
Path: DB0FHN<DB0MRW<DK0WUE<I0TVL<IK6IHL<IS0GRB<IW8PGT<VK4TRS<VK3FBD
Sent: 060617/0729Z @:VK3FBD.#MEL.VIC.AUS.OC #:11211 [Lilydale] FBB7.00g
From: VK3XX@VK3FBD.#MEL.VIC.AUS.OC
To : MORSE@WW
Hi Warren and readers
Hello stranger! Long time no see!
You made your point OK. Yes, if you cant hear you cant copy CW. As for
your claim about being able to copy PSK31 when you cant hear it then fine.
Presumably you can at least see it. I dont even listen to it on HF in an
SSB bandwidth because there are so many stronger stations even audible
that a weak PSK signal cannot be individually detected at all. BTW how
many stations have you heard and worked there on PSK31 on 2 metres??? And
at what distances.
Seeing that the only comparison that I could realistically make on 2
metres was with one person over a specific and difficult path I could
hardly go searching for a weaker PSK signal that I couldnt hear yet
didplayed on the screen and printed OK without being audible. It would be
a miracle particularly as I have never yet heard any other CW or PSK
signal on 2 metres in 30years. I havent even worked an SSB signal never
mind heard one for ages at this QTH mainly because I cant pick my times
coincident with activity nets and certainly there are none on cw or PSK. I
dont hear any local PSK or CW activity in this centre of activity ie
Melbourne for all its 3 million population with perhaps a dozen amateurs
using other than FM voice on some repeaters. The next centre of activity
which I have worked on SSB is Adelaide which is about 800km away probably
with a similar level of activity, helped along by a troposheric opening
and Sydney at about 950km and again a similar level of VHF activity and
only heard on aircraft enhancement.
My test was made with one station which I knew and which given slightly
more than adequate conditions we could try the readability of those three
modes for the same power, very moderate antennas and in locations subject
to suburban noise floors which will lift the meter off its stop without a
low noise pre amp. The RX does have a GASFET front end. The noise floor
with a preamp is about S4 with that !!! No the preamp is not at the
antenna feed point. I am sure that the overall noise figure is no better
than 3 to 4DB due to feeder loss so I make no attempt to try to be a VHF
DXer.
I merely reported upon a specific series of about three tests which were
possible under condtions where we made managed to make any vhf contact at
all. It wasnt a thesis on propagation or Mr Sannon's theories. We may have
plenty of space here as do you in the US but with only about 13000
amateurs, many not even active, and most located in the state capitals,
which are all a hell of a long way apart VHF wise. For every one active on
VHF on any mode there might be 100 plus on HF ad less than half those
would be classed as serious DXers. Those that are are on remote farms as
for many years even in country towns the restrictions on other than modest
antennas are difficult to overcome in any area zoned for domestic housing.
Even on HF PSK31 the signal has to be about S7 here to get a print which
approaches 100 % . Even CW in 500Hz bandwidth can be undetectable or
certainly unreadable at times in the sort of noise floor which I have to
contend with. It wasnt much better 30 years ago when this was a semirural
fruit growing area.
While I concede the point which you made we have to live within the
practicalities of our environment, which is becoming more difficult year
by year. Unless you live in the wilds of New Jersey away from residential
zones, I find it hard to believe that you can have a noise floor even on 2
metres which is much less than -125dbm. I still maintain that a CW signal
is easier, in a 500Hz bandwidth, to copy than a PSK signal in a 32 Hz
bandwidth is to print 100% when SSB is barely readable at all. BTW all
being produced by the same transmitter peak power output which would be
disadvantageous to SSB in 2500 Hz bandwidth.
I rest my case, a practical result rather than one that is theoretically
achievable and that is what I set to set-out in support of Morse and the
human ear combination. And of more value to an average amateur station in
a typical local environment. I concede, but do not apologise for my
evaluation!!!
73 - GORDON, VK3XX @ VK3FBD.#MEL.VIC.AUS.OC
Message timed: 17:09 AEST on 17 Jun 2006
Message sent using WinPack V6.80 (Registered)
Read previous mail | Read next mail
| |
