On 12/1/2013 2:42 PM, amdx wrote:
On 12/1/2013 11:48 AM, Irv Finkleman wrote:
Before too much theorizing takes place, why not try just placing it in a
convenient location in the house -- you might be pleasantly surprised.
If that doesn't work, then, and only then, it becomes a technical
problem.

Irv VE6BP


That's good advice, except I have three different audio inputs that all
land where I now have the transmitter.
Besides, we like technical problems! :-)

After my last response to Jeff when I measured the output voltage, I
just realized I can check the loss through the LPF. Hot dog! Can't
wait to get home.
Mikek

Don't fool yourself. A 10x probe has maybe 10pF capacitance. What is
that reactance at 100MHz? About maybe 160 ohms? How will that affect
your measurement?

As far as an upside down vertical is concerned, you should get the free
copy of EZNEC and study what it is that you want to achieve. The ground
characteristics and the height above it is what determines the so-called
angle of max radiation. Height alone is sufficient to lower the angle.
For example, a perfectly conducting earth has an angle of maximum
radiation of zero degrees. Think about it.

On 12/1/2013 5:17 PM, John S wrote:
On 12/1/2013 2:42 PM, amdx wrote:
On 12/1/2013 11:48 AM, Irv Finkleman wrote:
Before too much theorizing takes place, why not try just placing it in a
convenient location in the house -- you might be pleasantly surprised.
If that doesn't work, then, and only then, it becomes a technical
problem.

Irv VE6BP


That's good advice, except I have three different audio inputs that all
land where I now have the transmitter.
Besides, we like technical problems! :-)

After my last response to Jeff when I measured the output voltage, I
just realized I can check the loss through the LPF. Hot dog! Can't
wait to get home.
Mikek

Don't fool yourself. A 10x probe has maybe 10pF capacitance. What is
that reactance at 100MHz? About maybe 160 ohms? How will that affect
your measurement?


I don't know.

I put a T on the scope with 50 ohms on one side and the transmitter
driving the other side. The scope is 15pf/1Meg input impedance.


Two of the measurements I made a
50 ohms or antenna and with 110Mhz LPF and without LPF.
Transmitter at 87.5Mhz


50 ohm 7.33Vpp
l
Transmitter---LPF---l
l
scope


50 ohm 7.13Vpp
l
Transmitter---------l
l
scope

I don't know how the 15pf affects this measurement.
But I don't see much loss in my LPF.

Rubber Ducky 8.45Vpp
l
Transmitter---LPF---l
l
scope


Rubber Ducky 8.45Vpp
l
Transmitter---------l
l
scope

I checked this twice, I have digital voltage display on the scope.
So no loss at transmit frequency. I don't know how that works, I'll be
checking for radiation soon!

Is there anyway to compensate for the 15pf, could I put an equivalent
inductance in the scope input circuit? (for this frequency only)

I have two 3db attenuators, when I put those between the transmitter
and the LPF and the LPF and the Load (antenna/50 ohms) I get slightly
less loss with the 50 ohm load and slightly more loss with the antenna.


What say you?
Thanks, Mikek

PS.
I want to check the attenuation of the LPF at 175 Mhz and 262.5. I just
threw away a QST that had an article with a 220Mhz osc. I'll retrieve
that tomorrow.

On 12/1/2013 7:17 PM, amdx wrote:
On 12/1/2013 5:17 PM, John S wrote:
On 12/1/2013 2:42 PM, amdx wrote:
On 12/1/2013 11:48 AM, Irv Finkleman wrote:
Before too much theorizing takes place, why not try just placing it
in a
convenient location in the house -- you might be pleasantly surprised.
If that doesn't work, then, and only then, it becomes a technical
problem.

Irv VE6BP


That's good advice, except I have three different audio inputs that all
land where I now have the transmitter.
Besides, we like technical problems! :-)

After my last response to Jeff when I measured the output voltage, I
just realized I can check the loss through the LPF. Hot dog! Can't
wait to get home.
Mikek

Don't fool yourself. A 10x probe has maybe 10pF capacitance. What is
that reactance at 100MHz? About maybe 160 ohms? How will that affect
your measurement?


I don't know.

If you can't calculate or reason out the answer, then you need a teacher
better than I.