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What do you think about the new 5W booster amplifier?
Posted: Fri Nov 01, 2002 4:23 pm
by pcs
What do you think about our new 5W booster amplifier?
I only relate to Tangible Hardware
Posted: Mon Nov 18, 2002 10:06 pm
by StormiNorm
Looks ok to me,but i am the kind of person who does not like to speculate on any piece of hardware.
Norm B
Posted: Sun Oct 26, 2003 2:39 am
by pcs
How would you guys feel about adding a 10-15W booster to the product portfolio? Perhaps with a potentiometer that enables full adjustment from 0W to 10W?
Posted: Thu Dec 04, 2003 10:28 pm
by Yoda
Wack out a nice 40watt booster in both ready built and also kit form. I really do think that they might sell - if the price is right.
People that want to transmit around their neighbourhood would only choose 1-2w, if anyone wants to transmit further than that they would probably want to go as far as possible, therefore they would want more power. Now I do understand that 10-15w would go further than their neighbourhood, but if ya was kicking out 40w and had a nice big knob to vary the output, then its totally down to the user. There are loads of bits of schematics/construction notes on the internet (most of them dont make much sense unless your a real good electronic engineer), there are not so much about 5-15w boosters....therefore I feel that 40 watt boosters are more popular than little ones.
If you make one in kit form too, without the box and all the nice bits then it will keep the price down. One thing I have noticed in my many years for playing with transitters etc. is that people that play with pirate stations don't have £100's to be spending on boosters, expensive antennas etc.
And finally, and I am also sorry to say it, but I do think that your EL 525 10-20w booster is expensive - Ok, it has good specs, better than some other makes, no names mentioned, but it does seem a bit on the pricy side, when if you are able to construct one yourself for less than 1/4 the price if you shop about for the bits. And I know what you are going to say now....homebrew boosters splatter the signal and the harmonics are wild, but people that run pirate stations dont really care much about things like that as long as they are not causing any interference with surrounding equipment. So, I really do think you should give it a bit of thought.
Please feel free to put me back in my place if you feel nesessary 
Posted: Thu Dec 04, 2003 11:46 pm
by Sir Nigel
PCS does sell a 50w tx. But I think that after you get to higher wattages, you don't really have companies selling them as kits. Please correct me if I'm wrong.
Posted: Fri Dec 05, 2003 12:50 am
by Yoda
Hi Sir Nigel,
I'm not sure about PCS selling a 50w booster. I have looked at their web site in detail and have not come across one (the most powerful i have found on their site is 20w), but they do have schematics for a sort of universal booster that basically you put in the transistor of your choice (from a table of compatibles (check the schematics section)) maybe PCS themselves can clarify this..??..
I do agree about companys not selling kits for above 40w or so, I have not found any so far, but some do sell kits for upto 40w. What I was refering to was there are lots of schematics about for boosters of about 40w on the internet just like the one on PCS's website, but not a lot of them supply them as kit form, they just supply them as a whole complete package ready built and tested etc.
Another thing I have found from my research on the net is that a lot (even some modern ones) use valves. Constructing a valve booster is not something for the faint hearted as they use high voltages and are probably not recomended for the novice constructer, and also from what I know (and please dont take this as gospel), but valve amps require a mains voltage to power them. Some pirate stations like mobility so they dont get caught by the authorities and therefore mainly use a voltage of around 12v.
Please don't take what I say as definate as I am not totally sure, its just the feel that I get form all the research I have done on the net - and I have done a lot, but still i could be wrong, but I try my best.........
Posted: Fri Dec 05, 2003 4:59 am
by Sir Nigel
Posted: Fri Dec 05, 2003 9:39 am
by Yoda
I have seen the transmitter, but it runs on 230v so therefore would not be good for mobile use.
Posted: Fri Dec 05, 2003 9:43 am
by R_QRP
For a 5-15 watt transmitter, the IRF510 is a pretty good choice.
Its Drain-source breakdown voltage is 100V which gives a reasonable amount of headroom. (on mod peaks the supply voltage will be 24V , assuming a 12V powersource. The RF voltage on the FET will be something more than 2 times that, say peak voltage of 60-70 Volts.
The input capcitance of the IRF510 is quite low (Ciss ~= 150PF) which makes it easy(er) to drive than larger mosfets with higher gate capacitance.
Why not try to get more out of the IRF510? The problem is Rds - the on Resistance, which is 0.4 ohms for the IRF510. The output impedance seen by the FET is roughly V*V/2P where V is DC supply voltage and P = power out.
If P = 10 and V=12 then the output impedance is about 12*12/2*10 = 7.2 Ohms
If P = 20 and V=12 then the output impedance is about 12*12/2*20 = 3.6 Ohms
As the value of Rds gets larger relative to the output impedance the efficciency drops and you stat producing more heat and less RF.
At the small end of the scale, you could try MTP3055Es. They are tested at 7 Mhz, but they are gate capacitance is about 3 times that of the IRF510, and thier breakdown voltage is rated at 60 Watts. If you can drive them you may be able to get more out than an IRF510, assuming you adjust the output network ...
73s de R_QRP
Posted: Fri Dec 05, 2003 10:51 am
by pcs
Not for FM
Posted: Fri Dec 05, 2003 11:05 am
by R_QRP
May be for comming LPAM projects !?
73s de R_QRP