Re: Strange happenings!

Peter Russell <peter.russell@...>
 

I'm not sure who's design of bridge you are using, but your placement of the 50 ohm resistor seems a bit strange - it's also seriously loading the dc output.

Have a look at this one - I know it works, 'cos I use it!

http://www.nd6t.com/bitx/RF%20Monitor.htm

I'm sure Don won't mind me pointing to his site - he's probably lurking around here somewhere just watching!

Have fun.

Peter G8FWY

On 05/02/2019 17:57, barry halterman wrote:
I have explored this further and put in a larger toroid, FT50-43 from recommendations from the group.
 When I leave the toroid in line, with no connection to the secondary winding, I find that all third harmonics are cut in half! Which is interesting and for my setup puts the rig way below the -43dbc threshold by 6-8db. ( I am just on the threshold without the toroid. )
However connecting the secondary winding to the rf detector and ground throws a monkey wrench into the whole mess. Second order, third order harmonics go up drastically on all bands.
I changed the diode to make sure it wasn't causing the problem and that made no difference.
This is just a simple, no connection way to measure output power.
I would really like if someone with a good SA could duplicate this and get back to me.
Thanks.
K3BO
On Tue, Feb 5, 2019, 4:15 AM Peter Russell <peter.russell@... <mailto:peter.russell@...> wrote:
I'm probably going to get shot down in flames for this, but is it
possible that the ferrite core is saturating?
Peter G8FWY
On 04/02/2019 21:13, barry halterman wrote:
> Hopefully some could shed some light here.
> I intended to put in a power meter in my ubitx, so I installed a
FT37-43
> toroidal core at the rf output
> Connector (ran the center coax conductor though the core) with 3
turns
> for the secondary winding. One end of the winding was grounded
the other
> end to a diode to a capacitor and 47 ohm resistor, in parallel, to
> ground. Upon key down in CW mode I measured around 3.4 volts
which was
> about 11 watts out into my dummy load....So far so good!
> This is where it gets interesting! With my SA the harmonics on
all bands
> went from marginal to very poor. I pulled the toroidal core off
the coax
> and the harmonics went back to marginal, where I started from.
Why would
> a toroidal core at the output cause such a degrading of the
harmonics?
> Even the second harmonic was there with the toroidal core, and
not with
> the core removed.
> Puzzling, very puzzling!
> Thanks
> Barry
> K3BO
>
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