[Hammarlund] HQ-110...rats...

[Kenneth G. Gordon]

On 9 Jul 2011 at 8:50, David Langley wrote:

> Well I haven't had drift problems with my HQ-110 but hear about this
> from others like your self.

I have heard of drift from most Hammarlunds which use the 6C4 or 
equivalent as an HFO. Many don't drift, however.

My HQ-110 didn't have this problem shortly after I "restored" it. It 
popped up some time later.

> Might be something other than the 6C4,

Agreed, but I have always felt that a simple triode HFO was a problem 
waiting to happen. Other oscillator circuits are inherently more 
stable; the so-called ECO, for one.

> such as line voltage variations,

not the problem here,

> resistor or capacitor changes with
> heat.

perhaps, here, but unlikely: it happened too quickly

> If a tube change doesn't solve the problem, I'd suspect something
> else before I change tube sockets etc.

Yes. While I certainly agree with you, and while I intend to, FIRST, 
substitute tubes, I also want to play a bit with the circuit to see 
if I can reduce both the instability AND the necessity for using 
"perfect" tubes to get that stability in the HFO. 

I would like to make the circuit less "touchy" and more reliable in 
that regard. I think it is really unnecessary to need especially good 
tubes to make the circuit work properly. To me, that requirement 
proves a poor design. 

Any really good circuit should be as independent of the quality of 
the active device as possible.

> Just an idea. Let us know what
> you do find that cures the problem. Dave -W5QWX

Oh, I will, Dave, thanks.

The main reason I enjoy forums like this is that it gives me an 
opportunity to share ideas and experiences with other like-minded 
curious individuals.

By the way, the instability that suddenly showed up in my HQ-110 
manifests itself, primarily, in really SEVERE pulling by even 
moderately strong received signals, yet voltage checks show no 
significant voltage changes with signal input. 

The regulator is regulating just fine too.

At this point, although I am only "somewhat" suspicious of the 6C4 
HFO, I am VERY suspicious of one or both of the 6BE6s. I hate, loathe 
and despise pentagrid mixers, especially self-excited ones. 

In fact, in this case, I am MOST suspicious of the "first converter": 
the 6BE6 mixer which is also a crystal oscillator.

Mine is the first version.

Ken W7EKB