Dick, PA0SE, has given a lecture on LF for our Amsterdam Division of our
national Dutch Ham Organisation VERON ( " Dutch RSGB " ).
He made me pretty enthusiastic and I decided to give it a try to become
QRV on 136 Khz.
My condo is 100' a.s.l. and I could try to drop a vertical wire of 100'
thru a ( straight ) pvc (rain) drain pipe.
Could this idea do an acceptable job ?
If so, how should I connect to earth ?
( If I learned my lesson well - from Dick - a good earth is at least as
important as a - relatively - good antenna ).
Any other antenna suggestion for my ( top floor ) condo at 100' a.s.l. ?
BTW : I am forbidden to span a longwire on top of the building :-(
My first step was to buy a ( professional, be it vintage, all solid
state ) LF receiver today.
And that's where my second question is about..
It is a Telefunken ELK 639 with LF as from 9.8 Khz until 570 Khz in 5
bands.
It has all options except the 100 Khz spectrum monitor ( but I could use
my separate 10 Hz BW spectrum analyzer; besides, Dick showed that that
on 136 Khz the computer waterfall programs are commonly used ).
I made some preliminary tests ( with a calibrated signal generator )
and I am delighted with the RX's performances.
It has a superb sensivity at very steep bandpass skirts.
With all mechanical filters cascaded on smallest BW's gives : 500 Hz
off tune is > -85dB ( which is considerably within specs cf the manual ).
I could hardly believe this result.
For that reason I reproduced the tests with another signal generator (
HP 3336B which is even a calibrated level generator ) and I get ~ the
same results.
During his lecture, Dick PA0SE, mentioned the nuisance of severe
interference of DCF?? ( and other stations ) and I guess that, for that
reason, steep filter skirts are foremost on 136 Khz.
However, is this result sufficient for escaping the commercial neigbour
stations interferences ( near our band edges ) Dick was talking about ?
I wonder if any list member uses or has been using this Telefunken ELK
639 as well.
I am eager to learn about the possible experiences on this one.
E.g. : is its stability sufficient for the very narrow QRSS QSO's ?
Should I ( try to ) lock the LO's to my frequency reference ?
If this does make sense, I could ( try to ) lock my Schomandl ( with
very low phase noise ) or HP 3336B to my e-11 HP frequency standard,
thus ensuring ( more than - sic - ) sufficient frequency stability ).
Any comment and/or suggestion on the use of the ELK 639 for 136 Khz is
most welcome.
Any other advices as well.
Thanks.
Peter, PE1E.
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