|
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
|
Could you post the circuit??? It looks very interesting,? very interesting.? ?Doug
|
The link in the first paragraph will get you the schematic.? Also the web page
gives details on how to make the measurements.
I'm using a MingHe MHS-5200A signal generator good to 25MHz with output
from 5.0V down to less than 50mV, but the signal gets ugly at the low
output voltage.
Scope is a Rigol DS1054 50MHz 4 channel scope with 1GSample rate.
FYI
toggle quoted message
Show quoted text
On 4/21/25 20:52, Doug Hendricks via groups.io wrote: Could you post the circuit??? It looks very interesting, very interesting.? ?Doug
--
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
|
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 <chuck.adams.phd= [email protected]> 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
|
i have a peak transistor tester, which gives me f_t but that little tester looks like a fun project and i have roughly a zillion 2N3904s, 2N2222s, etc that i could run through it, so build it i will.?
?
cheers
bill
|
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.
toggle quoted message
Show quoted text
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
|
It's a clever circuit alright, and I guess I'll have to give it a shot too. Some years back I was discussing how to measure Ft with Glen Weinweber.? I think he got a little further along than I did.???
More recently I thought I'd just try a plain vanilla amplifier and compare the responses of different transistors. It wouldn't tell me the Ft, but it would show me how a 2N2222 compares with a 2N5179, for instance, or how an unmarked?or house marked transistor compared to known types. I avoided reactances to keep it clean, except for the unavoidable coupling and bypass capacitors, and I also biased for?10 mA. The idea was to use the nanoVNA as the source and the detector.? It worked OK, I guess.
But this Wenzel circuit seems a lot cooler.? I assume when one port isn't being used, you'd put a 50 ohm terminator on it???
I can see using the nanoVNA again. The measurement at the CAL port should be flat, so you could just look at it once and record the dB value, then go to the OUT port and find the? frequency where the response curve has that value.
73
Nick, WA5BDU
On Tue, Apr 22, 2025 at 10:20?AM chuck adams via <chuck.adams.phd= [email protected]> wrote: 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.
On 4/22/25 06:20, Michael Maiorana via 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
> <> <chuck.adams.phd=[email protected]> 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
|
bill K7WXW
Nick Kennedy