开云体育

Fahnstock clips

On Mar 12, 2023, at 22:16, Mike C. <mg@...> wrote:

You mean one like this:



Small Fahnestock Clip


Fahnestock clip top viewFahnestock clip top viewFahnestock clip top view

Mike C. Sand Mtn GA

On 3/12/2023 8:25 PM, Don Rolph wrote:
Fahnstock clips

<0ojagx1xcOR9wcDo.png>

I have lived in Florida for 20+ years....... believe me they are ALLIGATOR CLIPS if I ever saw one !

John
KK4ITX

Visit:www.zaarc.org. ?

On Mar 12, 2023, at 22:16, Mike C.<mg@...> wrote:

You mean one like this:



Small Fahnestock Clip


Fahnestock clip top viewFahnestock clip top viewFahnestock clip top view

Mike C. Sand Mtn GA

On 3/12/2023 8:25 PM, Don Rolph wrote:
Fahnstock clips

<0ojagx1xcOR9wcDo.png>

On Mar 12, 2023, at 23:24, Sam Reaves <sam.reaves@...> wrote:

I knew a fellow named Dave Fahnestock whose grandfather or greatgrandfather
was the owner of Fahnestock Electric who IIRC owned the patent on those
clips.

Sam Reaves
ARS W3OHM
Owner / Moderator of:
LeCroy Owners Group on Groups.io
Sencore Owners Group on Groups.io
Sprint Layout Group on Groups.io
Pulsonix EDA Group on Groups.io
LPKF Owners Group on Groups.io
Electronics and Mechanical Hardware Design Engineering Manager
Staff Scientist Andritz Rolls Global Research Center (RETIRED)

Bryan,

Those power supply ferrites are useful for low frequency power or choke applications but are not that useful for HF balun, unun or transformer applications. The unknown ferrites I find useful are those split ferrites placed on cables for RFI attenuation. Most are designed for VHF attenuation and are similar to the Fair-Rite 43 mix.

There is no standard color code. The colors are probably unique to the manufacturer.

Mike N2MS

On 03/11/2023 4:25 PM Bryan Curl <bc3910@...> wrote:

Thanks all. I just wasnt sure, for a thru cal where to place the Open Short and Load bits. Its pretty straight forward for using just S11 for reflected measurements.

Mike that's a great idea for identifying ferrites! I tore some out of an old PC power supply that were green, blue and black but have no idea what they are. Colors may or may not be an indication.

Thanks again everyone.
Bryan

Once you get above a few MHz. you have to be careful when measuring
capacitors, inductors and baluns if you want meaningful results.
Stray inductance and capacitance can make a big difference and you can
get resonance effects that are due to parasitics and not the component
itself. Attached is one example where a few pF of stray capacitance
from using an alligator clip test jig made an inductor look like it
was resonant when this was not the case. Another shows how the value
of a capacitor measurement is affected by an alligator clip test jig.
Comparisons were made to a fixed jig using properly spaced SOL with 50 ohm SMD.

39.336826 N 78.982287 W

Remember K1YSD, wish he was still around.

Mike C. Sand Mtn GA 1600 angles

34.831648, -85.567676

On 3/13/2023 1:26 PM, Lester Veenstra via groups.io wrote:

39.336826 N 78.982287 W

I remember him! I probably have all those 73 issues still around. He wrote
a lot of great humorous articles.

Zack W9SZ

On Mon, Mar 13, 2023 at 2:18?PM Mike C.<mg@...> wrote:

Remember K1YSD, wish he was still around.

Mike C. Sand Mtn GA 1600 angles

34.831648, -85.567676

On 3/13/2023 1:26 PM, Lester Veenstra via groups.io wrote:

39.336826 N 78.982287 W

There is an archive of 73 Magazine here:



That site has many other radio related books and magazines.

Wow, since we have a full listing I wonder if K1YSD is among the findings?

Mike C. Sand Mtn GA

On 3/14/2023 8:00 AM, Mike M wrote:

There is an archive of 73 Magazine here:



That site has many other radio related books and magazines.

On Mon, Mar 20, 2023 at 10:55 AM, Steve Johnson wrote:

@Roger, when building the simple test jig you pictured above, what are the best type of resistors to use for the LOAD plate? I think some types are to be avoided, but can’t recall which.

I used some 50 ohm thin film 0805 SMD resistors in my parts pin. Thin film resistors are able to achieve much lower tolerances, have lower noise, lower parasitic inductance, and lower capacitance compared to thick film devices. 50 ohm is not a common value so use two 100 ohms in parallel and "cherry pick" them with an accurate DMM. You want the parallel value to be as close to 50 ohms as possible in order to get more accurate measurements of low and high impedance DUTS. Using a NanoVNA-H4 I can measure a 1000 ohm SMD resistor to within 5% and this is good considering that the reflection coefficient is very close to 1.

Couple more questions on that jig:

1. Should the coax be as short as possible?

In my tests I have not found the cable length matters that much for measurements under 60 MHz. I have used 40 cM and 10 cm and both worked OK.

2. For the open plate, you must necessarily have a “backer board” to
attach the two copper pieces to. It appears you screwed the backer to the
copper. Do you think a glue could be used without impacting the measurement?

I am not sure what you mean. My test loads are made using double sided FR4 PCB stock with conductive copper tape used to connect both sides and solder used to make sure the foil has good contact on both sides. Make sure the slit in the middle (on both sides) is the same width on all boards and is as wide as possible while still having enough copper left to solder the 0805 resistor. In my next version I will layout a PCB board with plenty of stitch through vias and there will not be a slit on the load and open but V's like this > < to reduce the capacitance for the open.

3. To take measurements using both VNA ports, do you just use a second set of
these on the S21 port?

I do not use this jig for S21 measurements. I use another type of jig with female SMA connectors on each end


Roger