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.

 

 

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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