25% drop is only worth a few dB's. With, say an overall path loss something like 80 dB for example, having few dB difference doesn't figure much at all. There's more variation going on due to multipath reception. In a decent radio link, the AGC will accomodate variations in RX signal strength.I don't get why you say that. 2:1 VSWR is like a 25% reduction in power if I recall correctly.
Isn't this exactly the identical same behaviour you will get from almost any Antenna?<..> you can't use a dummy load that only works at one frequency and has to be adjusted to make it work at all.
With series-cap, it's still a series-tuned circuit, and ends up as resistive impedance. (@ the freq of interest)<..> wirewound resistors are massive value inductors at 100MHz.
Admittedly, getting a home-made dummy load to work at 600 MHz (Analogue TV transmitter) was tricky. I used a single light bulb & ceramic ('behive') trimmer in series.wirewound resistors at 100 Mhz?
Everybody knows what VK200 is, but nobody has a proper data sheet. I guess I'll have to assume it's 550 ohms resistive.
I haven't been able to find the base characteristics of the 2N3866.
you mean a 47ohm at the emitter?U2 is just not biased right at all, it'll probably run hot too. You need to have a at least a low value resistor between U2's E & B. Start with 47 Ohm.
what does "link out" mean? i don't know that phrasal verb.. english isn't my native language..Temporarily link out L3 and disconnect L4 from U2 C. The resistor R3 wants to be this 'broad-band dummy load' the conversation was about earlier. You definately can't use a bulb here (not unless working with a lower frequency).
i'm getting confused where do you want me to move the C4?Move trimmer C4 to across U2's e-b resistor. It's your choice whether you want to use 'L', or 'Pi' matching. Pi is more versatile. There needs to be a little bit more work here. In meantime for inspiration look at the example schematic that was posted earlier.
indeed it's a ferrite with 6 holes...but what makes you think it is sold without the wire?the VK200 is actually just the ferrite core with 6 holes in it. what the actual inductance is depends on how many turns you put through it. i've even seen (with very small wire) 75 to 300 ohm baluns wound on these little cores,
I agree 5% is fine, obviously there's nothing wrong with using 1% if it's all you've got to hand but it is a bit overkill.1% tolerance resistors aren't neccesary, 5% tolerance parts are usually used. use metal film or carbon film resistors.
That's right, you wind your own choke.companies like Ferroxcube make the ferrite cores and sell them. that's why every time the VK200 was mentioned in data sheets and app notes, the wire gauge and number of turns was also described.
is this a compliment? i'm greek...I didn't realise that english is not your native tongue. What is your native tongue?
i want to get rid the variable capacitors so it's a bless if they aren't needed that much.I've changed the matching network into a 'pi' matching network. What you ought to do is use roughly calculated values here. Otherwise you often find that a tuning capacitor is not enough pF's.
you mean the usual 10% resistors are fine?The old carbon composition ones (e.g. 10%) are blocks of carbon.
I don't think I've seen 1% carbon film, most carbon film is 5%.Carbon film resistors (e.g. 1% types) are somewhat inductive. It's because there is a spiral etched into the carbon film. The old carbon composition ones (e.g. 10%) are blocks of carbon.
Yes 10% will probably be fine but I think you've missed his point about the type of resistors used. 10% resistors aren't that common nowadays.whiz115 said:you mean the usual 10% resistors are fine?