No, it is not difficult at all. As you write the measurement system, it does not have to be strip-shaped, because it is large for that. I have no idea how to calculate this ratio of incident to reflected without prock .... With manual calibration, as in cheap reflectometers, it's cool, but the same must be done ... With prock, it is easy to calculate even a lot of ready-made items in the network ... We can have sad surprises with prock. Usually they sprinkle raisins all over the receiver. In my home made, I fought against it. Of course, it can be fought. From my radio I have 10W and in the lower bands around 80m almost 20W and to be honest it is impossible to hit. I have 3 dipoles and 2 deltas for it, it happened several times that I forgot to switch the fit to the end of course. I was surprised only when I felt the paint from the radio housing For power transistors in the ends it is good to use mica spacers and ceramic sleeves because plastics melt and that's the end
Well, this is not an SWR measurement, there is only one measuring line. I haven't read this guy's description of what he was doing yet. But I suspect that only the reflected is measured ?? The method of limiting the voltage in front of this 5v voltage stabilizer is debatable to say the least This is an ordinary detector and DC amplifier ..... It probably works to some degree. AAAAAAAAAAA and the topic of the 6.8V diode returns, there is also in this guy's diagram . Although in his case, this stabilizer powered by a voltage of less than 5V can actually get a breakthrough hehehehe Instead lm7805 could already give lm317 and work in the divider ....
Added over time I wonder .... I use an antenna box for radio. Such a security, probably, would make tuning terribly difficult ??
After a while, such a trifle. This protection regulates, lowers the current of the transistors in the PA. It's supposed to lower the power and protect it .... It's a rather bad idea. The current should remain unchanged and the power reduction should take place somewhere at the beginning ... Such a tip may even start working in class C and better not to think how it will start pouring into the ether ... On the output it would have triangles and squares like in this song hehehe
For such a system, I would rather suggest adding a buzzer to the diode only as part of information ...
Once, I also had a problem with these transistors (originals). A good and cheap solution is to fit a Grant power amp. Lest I was talking crap. I found Grant's schamt in the book "service diagrams" then there was still a problem with the net. It turns out that these are quite similar radios. The final stage in the Grant was on a different transistor (price around PLN 5). All you had to do was swap the collector with the emitter (but I don't remember exactly anymore).
As usual, no one mentioned the importance of stabilizing the operating parameters of such a mosfet. I see that my colleague the author had a pale idea about it, because I think he changed the layout from scratch. I would like to remind you that in the transients from saturation to opening, the switching transistor can be so unstable that apart from the method of LC cooling or shielding, it even depends on the serial number or the manufacturer. And apart from the transformer in the final stage, wound bifilarly, which is one of the PA protection against uncontrolled excitation, I see here a minimal creative invention of the author of the project who, when deciding to publish it, should at least inform that the system is devoid of thermal control of work (as in the original) or even the drain-gate protection circuit which would return the 180 ° phase directly to the input of the final stage directly from the output. The fact that a colleague gives a link to a proven mosfet is of little importance because the source will expire after some time and identical transistors will end anyway. If FM modulation was dominant in PL on CB, it would not be so important because it is class C. If the AM modulator was a modulation transformer, it would not be so important because it is also class C. But my friend probably forgot that in Jackson in AM, the work rate of PA is in the middle. Therefore, please give me a guarantee that the system will be stable or will not cause problems, as is often the case in home-made constructions. Please have a look at the www.sp-hm.pl forum where it is explained extensively, or at the first one [url=http://www.sp-qrp.pl/modules.php?name=Content&pa=showpage&pid=40] >>>> Link
The Jackson power stage is a linear amplifier and the use of a switching mosfet (and this is the IRF) is an average idea at 28MHz. Yes, the transceiver will deliver power, but the signal will be of terrible quality. This applies not only to harmonics (these are screened on the low-pass filter), but also to signals close to the transmitted signal. To show what the effects may be, I will provide a comparison of the two measurement results. The first is the power level where there is an obvious design error or there are problems with the BIAS:
And this is what it should look like (Yaesu FT1000Mk5):
Let me mention that originally President Jackson does not belong to a device with a "clean" transmitter (hardly any CB is "clean"). So if you replace the transistor with an IRF, which you drive badly (and you matched the circuits correctly?), You will get the same effects as in the first photo and it will de facto break the transmitter. There is one more important problem there. The circuit on the previous page actually has a wrong gate polarity that will cause nasty interference. I have to search, only found good elaboration on improving efficiency, the problem of IMD is also described there. Here is another study very good in my opinion.
This Jackson MUST be measured on the analyzer. Because you probably made a noise generator. So what is such an IRF suitable for? For power amplifier class C or D (telegraphy, FM, RTTY). That's where it works great.
It is me with the problematic PA in Jackson, I will go a little further and explain how difficult it is to track failures resulting from the fact that the radio is simply worn out after so many years and you should expect miracles there [url=https://www.elektroda.pl/rtvforum/topic1934612.html] >>Link>Link
The problem with the schema deficiency is that the MOS-FET it works linearly in a narrow range of gate polarization. * 4.674 gate polarization [V] +/- 1.2% * stabilized voltage 5.1 - 5.6 [V] and to the voltage divider the above key conditions were not met in the system. The point linearity is floating.
MOS-FET transistors, unlike Bipolar ones, work with voltage. voltage should not exceed in total Ugs 10 (15 *) [V]
Hello Something on the net weakly under the password "FQP13N06L PA" Can you expand the topic ?? The author's biggest mistake was that he did not check what he did in any way. The power measurement in this case would rather suggest that it was not the power at 27MHz, but some foreign oscillations lower. Probably the useful power was a few watts .... Well, at 27MHz it's not the IRF520 when it's 510
On the occasion of the experiment, you can swap FQP13N10 and IRF520N, the IRF520N should be given more power. The FQP10N10 in place of the current IRF520N will reduce the signal from the control stage less.
Added after 25 [minutes]:
buddy pawlik722, except that the power consumption jumped up slightly, the radio works one hundred percent correctly. As for the question about the difference in the schema, compare yourself with the original schema.
Hello HEHEHEHE Freddy "Rank # 3 on Google" is a PA schematic ?? Because somehow I can't see And so I ask and I ask what this version is better than IRF510 if it is recommended so? Because we are already talking about 510 from the first posts in the topic ... I don't jerk, I just want to know because for weeks I do PA on IRF510 maybe 520 at 14 and 21MHz .... It's worth trying those FQP13N06 ?? Somehow they aren't as widely available as 510 ....