Hi Markus, Group.
Thank-you for your interest in this enigmatic hissing dragon problem.
The 630m class E TX worked well with the original AD8950 DDS, but
when excited with the AD9851 clocked with the nice stable DOCXO,
the hissing started. The hiss orginates with the drain choke
(a 9 cm square core from a colour television) and persists
even with a dummy load on the TX o/p. Putting 260pF across
the TTL divider seems to reduce the hissing. Perhaps the DDS
output has a spur? The DOXCO is fed to the dds via a shoddy npn
stage which may be yielding a diry signal.
In the mean time, a new VLF licence 10 mW 8.0-8.3 kHz arrived
today.
73
Joe VO1NA
On Thu, 4 Dec 2014, Markus Vester wrote:
Hi Joe, sounds like a fierce fire-spitting dragon... What is the nature of that
hiss, and can you identify which component is actually producing the acoustic
emissions? High voltage discharges at the antenna, instable current through a
magnetrostrictive choke or transformer, or a singing ceramic capacitor?
Best 73,
Markus
From: [email protected]
Sent: Thursday, December 04, 2014 12:08 AM
To: [email protected]
Subject: Re: LF: VO1NA on 477kHz last night
Hello Roelof, Andy and J-P,
The TX was hissing furiuosly this morning while on the
wire aerial just before it was switched off. Thank-you
for the reports.
The TX will be off tonight.
73 & MNI TNX
Joe
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