vacume caps

[markus_jlrb]

@vk4ffab,

nice work.

I have get my vac. caps ten year ago and payed more the 100 Euro for each of the at that time.
This kind of caps getting more expensive over time and becoming rear.

vy73
Markus

[vk4ffab]

@vk4ffab,

nice work.

I have get my vac. caps ten year ago and payed more the 100 Euro for each of the at that time.
This kind of caps getting more expensive over time and becoming rear.

vy73
Markus

How do you go operating with the loop antenna inside your house Marcus. I have never been in such an antenna restricted place where I have had to get creative to get on air. So how do you get on?

[radiolistener]

DUDE please stop with your endless strawmen arguments showing that you are an internet expert. Go learn to read and understand things.

Dude, I'm not expert, but I have diploma that I learned electronics in college and university and have ham amateur license. I know antenna design theory and electrodynamics. And I have experience in building and using different antennas, include experiments with magnetic loop antennas which I used for transmission. My main interest is DSP design for DDC/DUC radio, but I know hardware part as well, include antenna modelling/simulation and impedance matching things pretty well.

So, I'm not sure, what I should learn and understand exactly in your opinion?

Even if you use usual antenna tuner, using C0G 2 kV capacitors is not the best choice, because they are going pretty hot during 100W transmission and it leads to self-untune.

But if you're dealing with high Q antenna, it has pretty high voltage and current, so cheap SMD ceramic capacitors with 2 kV rating is not suitable here, because they have relatively high loss (for high Q context) and not enough voltage rating.

We are not talking about high Q antenna's we are not talking about magnetic loop antennas. The op has a very low Q doublet and an L match. That is the context of everything that has been posted by everyone in this thread other than you.

Dude, I don't see anything in this thread that topic starter wrote about low Q doublet. That's your guess.

But topic starter is worried about efficiency, because he mentioned it and it means that he is focused on high Q.
This kind of interest is actual for magnetic loop and other high Q antennas.
That's why I wrote about magnetic loop.

No need to suspect anything. Just read his post:

The context is for use in an l match atu.

it appears that this quote a little bit confused me, because topic starter wrote "L" as "l" and I read it as "I". So I decided that he is talking about his own match atu in general.

But even for L-match it depends. As I remember my experiments with long wire, I got air variable capacitor breakdown across 3 mm air gap between capacitor plates with feeding just 10 W power and it happen on a classic L-match circuit... So it depends on impedance you're trying to match, Q factor of antenna and Q factor of antenna tuner components. In some cases 2 kV capactior rating will be not enough.


I should say that I'm using cheap SMD ceramic 2 kV capacitors in my 100W antenna tuner, but I'm very not satisfied with them. Because they are heating and it leads to untune. I want to replace it with silver mica but currently there is a war, and my purchase abilities are limited.

[markus_jlrb]

@vk4ffab,

I'm using a QRP TRX and the M-Loop creates only magnetic field radiation
in the near field which is not strong absorbed by the brick walls of my house.

Due to the M-Loop effectivity (5% to 50% depending of the sw band) and the
low power < 10W the connections are restricted to Europe.

I have three different diameters of the loop (0.8m, 1.2m and 1.8m) which
covers more or less 80 - 10 m operation.

When you use a coupling loop that could be shifted along the vertical diameter
as well which could be twisted outside the main plain of the main loop you
will get a tuning range of 1:5

vy73
Markus

 

[TimFox]

One last hint about capacitor choice for transmitting circuits:
In a resonant coupling network, the circulating ("tank") current is considerably higher than the actual current into the load.
That's the relevant parameter to calculate to ensure your capacitor(s) have sufficient current rating and to estimate the loss.

[markus_jlrb]

@TimFox, vk4ffab

beside the capacity loss, the mechanical/electrical connection between cap. and ind.
is most important, as the high cap current is only possible if the connection is done
properly. Every milli-Ohm counts and decrease the loop efficiency dramatically if exist.

That's the reason why my loop has gold plated connectors and the construction allow
high mechanical pressure between the L and C connection area.

As my loop is portable I was not able to construct the connection as a permanent one
by welding like  vk4ffab.

vy73
Markus

[vk4ffab]

@vk4ffab,


Due to the M-Loop effectivity (5% to 50% depending of the sw band) and the
low power < 10W the connections are restricted to Europe.

vy73
Markus

There are lots of countries in Europe LOL. With the cycle peaking, 10m should see you DX to everywhere even with QRP. My antenna is not that great on 10m, but I still manage some DX. My main bands are 40, 20 and 15m.

[Andy Chee]

Dude, I don't see anything in this thread that topic starter wrote about low Q doublet. That's your guess.

It’s not a guess. Just read the other posts made by the topic starter:

Fwiw my lashup franken doublet is working fine,the atu l match started off with a 1000pf wide spaced air variable,This was ok matching 80+40m but had a min c that was too high,i removed plates untill it was circa 300pf,This works well >40m too 10m,for 40+80m i have 1400 of silver mica caps switched in paralell with the variable,i just thought the vacume cap would alow better efficeincy+ tuning over the fixed silver mica?.The antenna is used mostly for interG nvis contacts,getting on 80m living in a small flat in a concervation area was difficult!.

[coppercone2]

but we can still answer the question in general because of the first post being general and it actually makes the thread better if the more specific question has been answered because its more information

[vk4ffab]

DUDE please stop with your endless strawmen arguments showing that you are an internet expert. Go learn to read and understand things.

So, I'm not sure, what I should learn and understand exactly in your opinion?

Reading and comprehension of what is written. Yeah your technical knowledge is superior to mine, heck lots of people in this thread can make that claim. But I am the only one who asked the OP for clarification of exactly what he was asking rather than assume, because i am not an expert and I am not a mind reader and I do not have all the answers. Reading and comprehension mean sometimes you have to ask questions to better understand what is actually being asked.

The context is for use in an l match atu.

Fwiw my lashup franken doublet is working fine,the atu l match started off with a 1000pf wide spaced air variable,This was ok matching 80+40m but had a min c that was too high,i removed plates untill it was circa 300pf,This works well >40m too 10m,for 40+80m i have 1400 of silver mica caps switched in paralell with the variable,i just thought the vacume cap would alow better efficeincy+ tuning over the fixed silver mica?.The antenna is used mostly for interG nvis contacts,getting on 80m living in a small flat in a concervation area was difficult!.

Now the OP's question was rather open ended, but he clarified things even before you started posting about magnetic loops. My comments were in the context of the above 2 posts. That the OP was building an L match and he had a doublet. Even if you had read the first of those comments, Post 4, before you made Post 5, you would have understood the context of the thread. Again reading and comprehension. Do you use L match tuners in magnetic loop antenna? Not that I am aware of, but they do use a capacitor, not a fixed capacitor as the OP was talking about but a variable one. What is being asked by the OP can be derived from the context of the thread and thus the context of the answers being given.

If you had read and understood the thread, you might have commented in a way that helped the op rather than looking for something wrong on the internet.

[Andy Chee]

but we can still answer the question in general because of the first post being general and it actually makes the thread better if the more specific question has been answered because its more information

The problem is that a specific answer may be irrelevant to the original poster’s query, in this case the irrelevant answer was magnetic loops.

Many n00b’s have been lambasted for not providing enough detail in their questions. The Beginners thread description even instructs beginners to provide as much detail as they can, in order to assist contributors to give an accurate and relevant response.

[p.larner]

what bw do you get with your loop on 80m markus?,wide enough for ssb or just data?.

[coppercone2]

but we can still answer the question in general because of the first post being general and it actually makes the thread better if the more specific question has been answered because its more information

The problem is that a specific answer may be irrelevant to the original poster’s query, in this case the irrelevant answer was magnetic loops.

Many n00b’s have been lambasted for not providing enough detail in their questions. The Beginners thread description even instructs beginners to provide as much detail as they can, in order to assist contributors to give an accurate and relevant response.

a thread where people just post to a general topic can be more interesting and long lived then a specific solution to a engineering problem. I mean what are we doing fighting for the front page like its the paper? If your interested in this stuff you end up reading the whole thread three times anyway to see if there is anything new you can use. Not to mention the broader question has a higher chance of giving an alternative approach to something that is just as good or better because its not confined within someones existing engineering dogma related to very specific parts etc. clearly the OP posted a general question indicating that he is willing to read general responses .

Just because he posted after the OP to answer someones questions with specifics does not mean we should totally ignore the opening post.

[vk4ffab]

but we can still answer the question in general because of the first post being general and it actually makes the thread better if the more specific question has been answered because its more information

The problem is that a specific answer may be irrelevant to the original poster’s query, in this case the irrelevant answer was magnetic loops.

Many n00b’s have been lambasted for not providing enough detail in their questions. The Beginners thread description even instructs beginners to provide as much detail as they can, in order to assist contributors to give an accurate and relevant response.

a thread where people just post to a general topic can be more interesting and long lived then a specific solution to a engineering problem. I mean what are we doing fighting for the front page like its the paper? If your interested in this stuff you end up reading the whole thread three times anyway to see if there is anything new you can use. Not to mention the broader question has a higher chance of giving an alternative approach to something that is just as good or better because its not confined within someones existing engineering dogma related to very specific parts etc. clearly the OP posted a general question indicating that he is willing to read general responses .

Just because he posted after the OP to answer someones questions with specifics does not mean we should totally ignore the opening post.

A long time ago, on a forum far far away, back when I was a total noob, I asked what I would consider to be a very simple question about diodes. Being a simple question, you would kind of expect that in the first couple of posts there would be a simple answer. But no. Two internet experts turned that simple question into a 10 page epic thread of them arguing about who was right using 1n4001 and 1n4007. My question never got answered, but we got 10 pages of performance on essentially the same diode.

Of course turning this thread into a debate about magnetic loop antenna might be more entertaining, it might even be a better antenna solution given the OP's space situation and sure it gives everyone the opportunity to show how wonderful and technical they are, but what it does not do is answer the very simple question about capacitors.

I guess it depends on what school we come from, for me its more about understanding what the actual question is and answering it as best I can rather than every thread being a performance where I can show others how smart I am. And for the OP his questions, while sometimes lacking in detail are mostly very utilitarian in that they seek an answer rather than a discussion of opinions.

Actually to the part of your quote in bold, I think that is exactly what should be done until the OP has been given an answer he is satisfied with. This thread is not all about us, its about the OP learning something and gaining better understanding of things. Answering questions that have not been posed especially when the OP has clarified what information he desires is rather poor form indeed and helps no one.

[coppercone2]

the thread is about us too we are not getting paid it should optimally be mutually beneficial. this is not a likely outcome for many threads but it is what makes us actually go to the forum, because good intention wears out fast (its a portion of why people post but not the whole story).

If it gets too out of hand the Op can ask for people to refocus. Part of starting a discussion is managing it, some effort is required... applies in real life too. On a 10 page dumpster fire the mods could step in.

[vk4ffab]

the thread is about us too we are not getting paid it should optimally be mutually beneficial. this is not a likely outcome for many threads but it is what makes us actually go to the forum, because good intention wears out fast (its a portion of why people post but not the whole story).

If it gets too out of hand the Op can ask for people to refocus. Part of starting a discussion is managing it, some effort is required... applies in real life too. On a 10 page dumpster fire the mods could step in.

I am more from the Pink school of philosophy, this threads not here for your entertainment. You are right, we are not getting paid, so that gives us the right to follow your friend Miranda and the Fifth and shut the hell up, we are not compelled to do anything. We get to choose what threads we comment in, who we reply to and if we even offer our help at all, because threads are not about us at all, they are about the person who posted them.

The quid pro quo if one exists at all is that you get to read what others have posted and maybe learn something along the way. Its not that you get to interject with flame bait and thread derails because of your importance to this forum. Your contributions to this thread could all be deleted and the OP will still have his answers, such is the level of irrelevance you are to this thread.

I am sure you think you are important, but the thread would stand without you. I think that is evidence enough disprove your comment about this thread being about you.