Yep, it's a 5 ohm resistor in parallel.? The circuit on the web has two 10 ohm
resistors in parallel.
I'm thinking of going with a RF voltmeter instead of the scope.? I get some
'jitter' on the max voltage reading on the Rigol of about 5% or so and it
is irritating.
I'm here to share.
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On 4/22/25 06:20, Michael Maiorana via groups.io wrote:
Hi Chuck,
That's an interesting circuit. It's hard to tell from your picture, but do you have two 51 ohm resistors in parallel to ground on the "CAL" pin? Or is that a 5 ohm resistor in parallel with 51 ohms?
Since these two signals are 180 degrees out-of-phase, I wonder if you could put some sort of summing amplifier there, so you can just adjust the frequency until the LED goes out? Saves the need to break out the O-scope.
Thanks for sharing
73
Mike M.? KU4QO
On Mon, Apr 21, 2025 at 11:48?PM chuck adams via groups.io <> <chuck.adams.phd@...> wrote:
Steve, AA7U, pointed the following circuit out to me and I just
had to build one.? Didn't take too long and it seems to work
nicely.? <> Photo of my
build attached.
I have some calibration to do to make sure the I_C current is
10mA.? You're going to need one of these if the 1,000x2N3904s
I'm getting work out.? I've checked out 1,000x2N4401s @ 294MHz
and I'll give you pointers as soon as the final verdict is in.
Less than $20 USD for each batch and the vendor has 50,000,000 in
stock, so at $0.01 or so each that is quite an investment in
inventory.? The f_t above is subject to fine tuning on the
fixture is just below the 300MHz min in the spec sheet.
This is important as I finalize the ADC-40 transceiver BOM.
I found BF245B's for $0.025 each and should have them by
the end of the week.? With help from DeepSeek, we have
results better than what you would get with the 2N3819,
MPF102 or J310 jfets.? Film at 11.
That's end of my budget limit I set, but I have enough
for a lifetime.
So, get the paypal account ready and I'll help you spend
your money, if the measurements pan out.? With 2,000+
transistors, I'll not be building anything with an IC
in it unless it's in a kit.? :-)
Looking for others that have checked transistors thoroughly.
Open to new and improved ideas.
FYI
--
chuck adams, aa7fo
QRP WAS 17m started Apr 2, 2025
WAS-17 QRP --> TX,FL,SC,GA,OK,AR,KS,AL,AZ,MN
? ? ? ? ? ? ? ? PA,CA,CO,WI,NE,ID,IL,NC,NY,AL
? ? ? ? ? ? ? ? MA,OH
DXCC? ? ? ? ? ?W,VE,JA,PY,ZL
--
chuck adams, aa7fo
QRP WAS 17m started Apr 2, 2025
WAS-17 QRP --> TX,FL,SC,GA,OK,AR,KS,AL,AZ,MN
PA,CA,CO,WI,NE,ID,IL,NC,NY,AL
MA,OH
DXCC W,VE,JA,PY,ZL
