HI all
Apologies but I
was "told" to go QRT by the real masters of the
station. Apparently my new QRO output on 137 was
dropping the cheap BT router (need a new metal cased
one with external antennae!) and they couldn't enjoy
their Netflix, youtube and such like, even though it
is I who pays the bills.
I write this as
I sit on a hard wooden chair in my shack as my
leather office chair has been annexed by a cat (1 of
8!)
As the XYL is
out tonight I will try again, subject to getting the
necessary permits signed in triplicate using my
blood!!!
Chris G3XIZ
spotted me twice at 6dB and 9dB at a range of 2km so
at least I know it's working, though 2km is hardly
Dx.
The next trick
is to determine the actual power output via antenna
current meter and see if I'm losing any en route as
the P4000 Hafler was running surprisingly cool on a
25% WSPR cycle, though it was out in the garage with
the door open and an ambient temp of 12c.
I'm going to
see if it works on 472khz, though John advised that
the P3000 (it's smaller sibling) wasn't a fan of
472, but worked fine on 137.
I'm looking out
for a 9505 but they are as rare as hen's teeth over
in the EU and not overly common seen in the
US
either.
I am also going
to re-try using the ELAD (via the 0dB broadband
output) and the 1watt amp again as last time I had
sound card woes.
~Such are the
perils of running with lash ups and not doing it
like a proper engineer! (I'm a Pharmacologist by
training)
73s all and
hopefully some of you will see me on the band over
the next few days.
With
best regards
Jim
Dr. Jim
Cowburn G7NKS IO92ub
Hi All,
I'm giving my new hafler audio
amp set up a try out on 137 WSPR.
IC706mk2G as an exciter (puts out
about 100uW on 137), feeding into 1.5W broadband amp
off ebay as per Dave Pick's article in Radcom. New
chokes fitted 600nH. This then feeds into the
unbalanced input of the the Hafler P4000.
The output is a 4:1 step up
txfrmr wound as per the plans on the W1VD
webpage. 2 lots of 16uF caps feeding into two 7
turn coils of coax wound on 77 material ferrite
toroids (I didn't have the cores to hand).
The coax cores then connect to a
balun assembly made using 77 material cores and this
goes to the antenna.
The whole assembly steps up the
impedance from the speaker terminals from 12ohm to
50ohm. The impedance was measured as 195ohm vs a
50ohm dummy load (4:1) and is broadband from 50khz
up to 1mhz. DC resistance is 2 ohm.
The amp is rated at 500W for
audio and de-rated by 3dB @ 137khz.
I'm currently WSPRing on 137.5.
Any spots most welcome
IO92ub Biggleswade
With best regards
Jim
Dr. Jim Cowburn G7NKS
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