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Re: cheap aliexpress LC100a = $13 paperweight?

 

Doug how long are your test leads? Really long leads can mess up the readings even if zeroed out.
Re: cheap aliexpress LC100a = $13 paperweight?

 

Let us know how it goes.? I bought one too but "maybe luckily" can't find it.? I think I only paid $10.00 with free shipping.
Jim WB4ILP?

On Wed, Apr 23, 2025, 6:36 PM Doug W via <dougwilner=[email protected]> wrote:
Just to add to the fun, here's a picture with the screen removed.
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Re: Mighty Mike Transmitter

 

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I don't see the feedback path to cause the crystal to oscillate.? If Q2 is supposed to be a Colpitts oscillator, it is not correct and missing the feedback capacitors from base to emitter and emitter to ground.? If you remove C1 and replace it with a 220 pF capacitor, and add a 100 pF capacitor from the base to the emitter it will probably oscillate.? You might have to experiment with the size of R3 to set the drive output of the Q2 circuit.

Hope this helps,

Jim, K8IQY

On 4/23/2025 6:25 PM, Steve Z via groups.io wrote:

I've begun building this transmitter (Manhattan style) but cannot get the oscillator to oscillate. Has anyone built this before? I also put the oscillator into LTSpice and did not see oscillation. Does anyone know if this will work?
Re: Mighty Mike Transmitter

 

Yeah, I was thinking that it needed those "Collpits" caps.
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Re: Mighty Mike Transmitter

 

Mike,
? I think there should be 2 caps in series from the base to ground with the midpoint tied to the emitter.? Also, remove the .01uF cap from emitter to ground.? I'll research the values for the 2 cpas, but off the top of my head I want to say 330pF each
Bob? WB0POQ


On Wed, Apr 23, 2025 at 5:25?PM Steve Z via <zabarnick=[email protected]> wrote:
I've begun building this transmitter (Manhattan style) but cannot get the oscillator to oscillate. Has anyone built this before? I also put the oscillator into LTSpice and did not see oscillation. Does anyone know if this will work?
Re: cheap aliexpress LC100a = $13 paperweight?

 

Just to add to the fun, here's a picture with the screen removed.
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Mighty Mike Transmitter

 

I've begun building this transmitter (Manhattan style) but cannot get the oscillator to oscillate. Has anyone built this before? I also put the oscillator into LTSpice and did not see oscillation. Does anyone know if this will work?
Re: cheap aliexpress LC100a = $13 paperweight?

 

¿ªÔÆÌåÓý

Yup, you're right! I can't even go by the 5% tolerance values I gave! Sorry, looks like this LC100A meter may indeed be defective.

Steve

On 4/23/2025 2:58 PM, Doug Hendricks via groups.io wrote:

Steve the LC100A meter is reading the cap at 292.9pF, which is not within 5% tolerance.? ?That info is from the picture.? ?Doug Hendricks?
Re: cheap aliexpress LC100a = $13 paperweight?

 

Steve the LC100A meter is reading the cap at 292.9pF, which is not within 5% tolerance.? ?That info is from the picture.? ?Doug Hendricks?
Re: cheap aliexpress LC100a = $13 paperweight?

 

Thank you everyone for the great ideas.? If nothing else you have convinced me to keep this and figure it out.? Unfortunately it will most likely sit on that shelf until I have more bench time in the fall or winter.? I went on a small aliexpress spending spree figuring 1/2 of what I got would be project starters and not instantly usable things.
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Doug thank you for that link.? I did read in a few other places about replacing L1 but nothing I read had enough detail about what to replace it with.? I took a closer look and I highly suspect it is indeed the pot metal donut they subbed for a proper core.
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Steve very good points.? A real test needs to be my first real first step.
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Curt thank you for the reminder that this should be a simple problem.
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I appreciate the help.
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--
¡ì97.313?? Transmitter power standards.
(a) An amateur station must use the minimum transmitter power necessary to carry out the desired communications.
Re: cheap aliexpress LC100a = $13 paperweight?

 

Doug W
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Not much in these things but an oscillator, a frequency counter and some easy math.?
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I mentioned a simple instrument that makes an L or C measurement, and renders answer in Morse code. It does close enough to 1% marked capacitor values. By analogy, it should be as accurate on RF inductors. So take some more data and see if there is a consistent plus or minus bias. The accuracy here is the precision of its crystal oscillator and its reference inductance and capacitance.?
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The device I used was kitted by George Heron and companions at njqrp. For Atlanticon one year we got this kit for paying our registration. We had to assemble it Manhattan style, they even updated its firmware at the conference. For Not many dollars we got the kit, printed proceedings, laminated badge. Enough door prizes that everyone got one. One year George managed to provide everyone a box lunch. I just ran across my 4 atlanticon badges. LC meter is still QRV.?
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Curt
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Re: cheap aliexpress LC100a = $13 paperweight?

 

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Hi Doug,

The problem is you don't know what your test capacitor's value really is. You say the cap is 5%, so that could make it 313.5 to 346.5 pF,? and both meters read? the cap within that 5%. Perhaps find your 1% caps and try the comparison test again.

73,

Steve AA7U

On 4/23/2025 10:39 AM, Doug W via groups.io wrote:

I bought a no name LC100a on aliexpress figuring it was worth the risk as they offered free returns.? Unless I am really missing something, it looks like I will be taking them up on the free return.? I understand my testing method is awful.? 5% caps using one cheap device to compare to another cheap device should make most cringe but the Kaiweets meter is usually good.? Those are 330pf caps.? I have some 1% ones I should dig out but at this point I doubt it will matter.? I did run and save all the self calibration routines several times.? This is my fault for expecting anything better for $13 from a seller called Pure Pure Grocery Store but sometimes it is fun to roll the dice.? Fun fact, the price is already up $5 from 2 weeks ago.? Does anyone with one of these devices know of a trick I might be missing or as I suspect is this just more garbage made with floor sweepings?
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Re: cheap aliexpress LC100a = $13 paperweight?

 

Try this
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It is very interesting and I think you are a perfect candidate for his process.? Please let me know how you get along.
cheap aliexpress LC100a = $13 paperweight?

 

I bought a no name LC100a on aliexpress figuring it was worth the risk as they offered free returns.? Unless I am really missing something, it looks like I will be taking them up on the free return.? I understand my testing method is awful.? 5% caps using one cheap device to compare to another cheap device should make most cringe but the Kaiweets meter is usually good.? Those are 330pf caps.? I have some 1% ones I should dig out but at this point I doubt it will matter.? I did run and save all the self calibration routines several times.? This is my fault for expecting anything better for $13 from a seller called Pure Pure Grocery Store but sometimes it is fun to roll the dice.? Fun fact, the price is already up $5 from 2 weeks ago.? Does anyone with one of these devices know of a trick I might be missing or as I suspect is this just more garbage made with floor sweepings?
?
Re: LT Spice Alternatives

 

I must have missed your initial post. I don¡¯t want to dismiss your feelings about LTSpice, but in my experience it is one of the easier Spice flavors. I may have to put this into perspective, my first interactions with computers were via cards, and even though my first version of Spice did not read from a card reader, it still required perfectly formed card input and produced long listings of ASCII output.?

Spend some time with it and go through some tutorials. I cannot promise that you will like it, but you should be able to use it.?

This is a class I did for our local club:
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Hope this helps,
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Karl Heinz - K5KHK?
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Re: L/C Meter Test

 

On Mon, Apr 21, 2025, at 9:54 PM, chuck adams via groups.io wrote:
Steve R. sent me some mica caps rated at +-1% for use as
pseudo-standard for capacitance checks.? Thanks Steve.
I'm sending him some transistors for his effort.

Here is a comparison between his measurements using a
DE-5000, which seems to be popular and mine arrives
I am getting a PeakAtlas LCR45 meter tomorrow because between that and the DE-5000, it was less costly.. I will have to get some +/- 1% caps and measure though.

--
Ramakrishnan VU2JXN
Re: SolderSmoke DC Receiver Challenge

 

Dave - I gotta say, getting a "neat-looking build" compliment from you made my day.? Thanks!? :)? ?The variable caps came from a stash of Tektronix parts that I accidently acquired when I bought this cabinet from a craiglist seller:
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I planned to use it for storing small parts and tools. I was quite surprised to find that it was already filled?with parts, even more so to realize that this set of rolling drawers was from Tektronix, from the days when the company had a shop that custom built stuff like this for its engineers, down to the cardboard boxes of different sizes that neatly nestled together in the drawers, like this:
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The fellow who sold it to me just wanted it out of his storage shed, so I got the whole thing for a hundred fifty bucks, which I was willing to pay for the cabinet, let alone the drawers of semiconductors, capacitors, nixie tubes, connectors, and assorted hardware it was stuffed with.? It was definitely the premier find from my days of haunting swapfests/craiglist/garagesales, looking for parts from the 70s, 80s, and 90s.??
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Cheers Bill K7WXW
Re: Building a PTO VFO

 

IF you want a more interesting mechanism see
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Its a kit of board that duplicates a lipstick mechanism.
That eliminates the screw moving in and out of the panel
and results in a simple rotating knob.
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There are other ways to do that as well.
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Allison
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Re: Source for 88 millihenry inductors?

 

Rewind old inductors! Over the years, before being displaced by LEDs, I had been collecting defunct CFLs. One immortal component is their EE-core choke (ballast) in series with the tube. At least in 220Vac units, their value is a couple mH.?
Take for example a 2.5mH unit. To get 88mH you need root(88/2.5) = 5.93x turns of wire with 1 / root(5.93) = 1 / 2.44 diameter. In practice, if you see plenty free unwound area in the core's window, new wire can be somewhat thicker.?
Most of the times these cores have an engraved air gap, the center branch is a little shorter, you will find no paper spacer.
Of course, the high needed turns count will require quite patience, and some form of winding gadget. And a supply for used enamelled wire that maybe is waiting to be discovered in your trash department.
Other supply for EE cores are PC power supplies: look for the driver, standby, and current-limiting transformers. Also, horizontal driver transformers and EMI mains filters in CRT TVs and monitors.
I think cores from most LED lamps are not practical: being open cores, that is with a very large air gap, they will need prohibitely many turns.
An idea to get the core halves separated is to boil the coil, or even place the core on boiling oil. Do not atempt to separate the halves applying force, you will probably break them.
Daniel Perez LW1ECP


Libre de virus.
Re: Active Mixer

 

other actie mixers used for DCRX over the last 50 years include:
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Dual gate mosfets (BF998)
Simulated dual gate mosfet using a pair of cascade wired J310s
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SIngle ended mixer using J310
Single ended mixer using any bipolar suitable for RF. 2n3904
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Single balanced mixer using bipolar part such as 2n3904
Single balanced mixer using Jfets such as J310, mpf102
Single balanced mixer using Ca3028 (very popular).
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And Gilbert cell MC1496? Oldie but goodie.
And of course SA612
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All of them are covered in EMRFD.
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All have been used and some work better than others
or have more resistance ot SW breakthrough.??
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The upside of ca3028 or any of the active single balanced
or double balanced (gilbert cell) mixers is they have gain
where DBM (passive diode) has loss from 6-10db.?
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one yabut is that all of those have different needs for
VFO injection so what would be good for DBM must be
too much or too little.
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Allison
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