Andrew VK3BFA wrote:

Needs a little cleaning up. Note the careful placement of the grid coil
at right angles to the final and with the Masonite panel between for
good shielding.

ERK! - looks like a 6146 PA, rather than an 807. And, congrats at the
attempt

I thought the "Masonite shielding" would suffice for a smiley.

That was my first attempt at a wooden chassis and it became obvious why
metal is better and I abandoned it a few weeks ago.

It started out xtal controlled but then I got the bug to add a VFO which
is the crap on the left. The 807 turned into an 866 so I substituted
the 6146 till I got another 807. The missing meter was a hamfest
special that bounced so much it was useless and then crapped out completely.

It is now all neatly mounted on a home made aluminum chassis and
unfortunately looks a lot better than it works.

I will take a for real pic tomorrow. That one was just too good not to
share.

And whats with the 3 big wire wound resistors? - screen supply to the
PA - what a potential source of stray coupling. A 1 watt resistor is
usually sufficient, you wont need the string of 10 watt ones....

One of the plans I was working for called for 25W. Seems like a
misprint because it does not even get warm. The 10K in the VR150 leg
gets hotter than hell and probably should be 25W. I burned my finger
just checking it.

And the anode tuning is about 100 yards from the tube! - can you get
it any closer?

If you look closely, you can see the 807 socket between the 6146 and the
cap. The 6146 is where the other 6ag7 is supposed to be.

And keep going - its worth the effort -

It's been a challenge. I made a simpler version of this as a kid and am
sort of re-living my childhood. It's like a Mr Wizzard Science project
for me.

I am now plagued with real test equipment and can't play "ignorance is
bliss".

js

--
PHOTO OF THE WEEK: http://schmidling.com/pow.htm
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On May 25, 2:31 pm, Jack Schmidling wrote:

I thought the "Masonite shielding" would suffice for a smiley.

It did - I just didn't want to spend the next 3 weeks figuring out how
to put one in.....(bloody computers)

And thanks for the explanation - I didn't see the 807 socket, and
didn't know there was a VR150(was it?) in there as well. And the
extraneous tuning stuff to the left, well, now I know its for a VFO.
(Gee, voltage regulation - thats getting fancy - yes, the dropper
resistors do run stinking hot, don't they....)

Strangely enough, theres a fault in human design in that the nerve
endings that detect heat are a lot bloody slower than everything else
- by the time we figure out its too hot, the damage is done....

And must admit to wallowing in nostalgia - mine attempts were
similar, and probably oscillated all over the place as well - BUT
without virtually any test gear, (or knowledge) it didn't seem to
matter - there was no one to complain anyway, the bands were virtually
empty except for other manic experimenters, TV was black and white,
and broadcast was AM. Nothing else to get into - and the bands were
harmonically related so we we're QRM other hams anyway....2m was the
outer frontier anyway, there was NOTHING used above that....

How about a photo of the latest metal attempt? - remember, if it looks
nice and neat, it doesn't really matter if it don't work too good....

I have things here I am not game to connect to the spectrum analyser -
don't want my dreams shattered toooo quickly....
but getting back, more and more, into the older stuff - partly fading
eyesight (I cant see u-mini smd ic's) and besides, theres something
comforting about the warm glow of valves in a dark room, the crash of
static from the other side of the world, the thrill of hearing someone
on air from an exotic National Geographic land...the reasons we got
into amateur radio in the first place..

The bands here at the moment are a total write off everywhere - 80m is
S9 noise, the rest not much better. QRM, QRN wall to wall. So, I sit
here and type on a keyboard, I guess its still "hamming" after a
fashion...



That was my first attempt at a wooden chassis and it became obvious why
metal is better and I abandoned it a few weeks ago.

Yep. Tubes with gain killed wooden chassis.....

It started out xtal controlled but then I got the bug to add a VFO which
is the crap on the left. The 807 turned into an 866 so I substituted
the 6146 till I got another 807. The missing meter was a hamfest
special that bounced so much it was useless and then crapped out completely.

Hah! - silly man - NOW you have to get the VFO stable, as well as all
the other problems. And as for 807's - I think about 90% of the people
reading this will have some sitting around, just waiting for the
"magic moment" of inspiration. Good On Ya Jack - your doing it - good
luck!

And the magics still there, even after 30 plus years of
experimenting........cant be killed by the internet, store bought
gear, mobile phones - all those glittering toys that didn't even
exist exist when we started out.....

And I got boxes of hamfest meters that are probably crappy too -
haven't tried to use them yet, so don't know. Finally built myself a
rough tube tester a few weeks ago (I had to, trying to find working
tubes for a VERY elderly Yaesu FTDX400)


It's been a challenge. I made a simpler version of this as a kid and am
sort of re-living my childhood. It's like a Mr Wizzard Science project
for me.

I am now plagued with real test equipment and can't play "ignorance is
bliss".

Yep. Its a real PITA that - we cant delude ourselves our home brew
QRM generators are not what they are.....still, its an excuse to use
some time creatively.......



73 de VK3BFA Andrew.

Andrew VK3BFA wrote:

and
didn't know there was a VR150(was it?)

That was before I added it. Strangely, it works about as well without it.

How about a photo of the latest metal attempt? - remember, if it looks
nice and neat, it doesn't really matter if it don't work too good....

I just posted one to http://schmidling.com/807b.jpg

Unfortunately, it now looks better than it works.

Hah! - silly man - NOW you have to get the VFO stable, as well as all
the other problems.

I faded out of ham radio because it was boring me to death once I "moved
up" to a rice box. My born-again career keeps me interested because
hardly anything works very well.

I finally gave up on keying the oscillator because of chirp but now it
drifts so badly, I still can't use it.

It's an interesting problem though that sort of defies my analytical skills.

When I turn on the osc, it drifts up several hundred cycles in a few
seconds and stops. I can find no voltage changing like that, I moved
all the hot stuff out just to test that and I am stumped. It seems like
it is in the tube itself.

I am now keying the grid bias of the osc and there is no chirp but it
does that several second climb that would be frowned upon.

Long term stability is another problem but in the noise at this point.

Do you or anyone happen to have a couple of 1000 pf zero TC caps? I am
using cheapo ceramics and they are not so good. Blowing on them through
a straw has a rather profound effect on the freq.

Interestingly, if I hook it up to a Variac, I don't get 200 hz change
until I get below 75VAC. This is rather amazing to me and points to a
temp rather than voltage problem.

BTW, this started out as an exciter for the 8000 rig but I have since
gotten the bug to make a CW rig out of it. Again, the rice box is too
perfect in that mode also for my interest.

js

--
PHOTO OF THE WEEK: http://schmidling.com/pow.htm
Astronomy, Beer, Cheese, Fiber,Gems, Sausage,Silver http://schmidling.com

On May 27, 2:02 am, Jack Schmidling wrote:


I just posted one tohttp://schmidling.com/807b.jpg

Unfortunately, it now looks better than it works.

And it LOOKS very nice...why no shielding around the vfo assembly? -
the sudden temp druft is possibly something suddenly stabilizing as it
warms up - BTW - polystyrene caps are a better substitute for disc
ceramics, especially old ones...


I faded out of ham radio because it was boring me to death once I "moved
up" to a rice box. My born-again career keeps me interested because
hardly anything works very well.

Good one- their the things that provide real satisfaction, the sort
that cant be bought...

good luck- keep us posted on progress.....

73 de vk3bfa Andrew

Jack,

New chassis looks great, well done.

It looks like you have a white wire (Anode HT maybe) going to a meter
then through the chassis. This will need some serious de-coupling
(feed through cap) as it enters the chassis otherwise it is going to
radiate in the lower chassis which won't help with the stability
issues. A 'T filter' would be good here, 1mH above deck, a 10nF
feedthrough cap and 1mH below deck.

As Andrew mentions, you also have 'below deck' electronics 'above
deck' in the form of the VFO. This is going to need very tight
screening to avoid feedback and stability issues.

What frequency are you running this unit at - 14MHz ??

Any chance of some higher res photos looking from above the chassis
and from below ?

Regards,

Mark
On May 27, 7:49 pm, Andrew VK3BFA wrote:
On May 27, 2:02 am, Jack Schmidling wrote:

I just posted one tohttp://schmidling.com/807b.jpg

Unfortunately, it now looks better than it works.

And it LOOKS very nice...why no shielding around the vfo assembly? -
the sudden temp druft is possibly something suddenly stabilizing as it
warms up - BTW - polystyrene caps are a better substitute for disc
ceramics, especially old ones...

I faded out of ham radio because it was boring me to death once I "moved
up" to a rice box. My born-again career keeps me interested because
hardly anything works very well.

Good one- their the things that provide real satisfaction, the sort
that cant be bought...

good luck- keep us posted on progress.....

73 de vk3bfa Andrew