160, 80 and 40 meter class D exciter
M0VRF:
I've got single band class E 20W designs for each band and can't see any design covering all 3 bands with a single Tx? Surely the only way to do that is to use the old way and use a linear?
Re the 500W version, this is something I'm working on but wont be giving any boards away only built and tested units at some cost. Not sure what you're expecting to pay but I offered some KW PWM modulators on here a while ago and got offers of $30 including postage so not sure what to expect??? They'll be SMT which most folk on here don't seem to like but has been the norm for 30+ years!
8 x C3M CREE SiC FETs and either the W1VD type or something akin to Steve's original design. Got PCBs for both on order, so some experimenting to do!
I've got a 4 FET 100W design I've been selling for years and have lots of PCBs for those which I would be happy to sell at a 'reasonable' price, again they're SMT but can build up.
Not a fan of VFOs so the 100W has 64 (or 16/32) channels , the 20W I mentioned earlier are either single channel with a pre programmed Cardinal CPP oscillator or uses a programmable AD9833 DDS via a USB adapter to any in band frequency.
Products are aimed at broadcasting rather than Ham use and used as backup TXs by AM stations + a few in AUS on 5MHz.
You could however bypass my Freq gen and just drive from your vfo? The 20W versions would be ideal as I modulate them to 100W+ pep so if you just want 25W drivers just use 3 separate TXs.
Just PM if you want any circuit details/pics etc..
That's it...
vk3alk:
Hi Don..
To make a 3 bander is quite simple and easy to do but you just have to know a few things…..
To keep it short for reliability and simplicity the best TX modules to use are H Bridge design….
On 160M and 80M its very easy to make a dual bander as at those frequencies these modules act as switch only and resonances are a long way away…..
40M is a little more difficult due to the lack of squarewaves....
To overcome this you use the gate capacitance of the FETs and add a bit of inductance to assist the driver in developing enough voltage swing...
On my posting of a 40M transmitter you can see things although now the output transformer is different….…
This TX works on 160M 80M and 40M without any extra components added during band switching ….
Have tested the transmitter on all bands to 300 watts only which is the limit of my bench test power supply …… efficiencies are well into the 90% region….
Of cause the choice of FET is critical to all this .... since this semiconductor business has happened they are not being manufactured for another 18 months…..
Wayne
steve_qix:
You could probably use a single IXDD614 driver IC looking into the primary of a transformer. They work very well at 16VDC, and 16V at 3 amps is 48 watts input. Even if the driver is 50% efficient (which it is not - it's better than that on 40 meters) it would probably do the job just fine.
Easy enough to try it out.... and simpler than designing and building (and debugging) a discrete component driver.
Just a thought.........
Steve
vk3alk:
Actually resonating the input enables the IXDD to loath along...
On 40M in single band mode you only need appox 9 volts on the IXDD at 450mA ....
You just have to be mindful about the resonant point...
Its a low Q circuit and even with a Q of 5 ( not sure what it is really ) with 10 volt applied to the IXDD that would give 50 volts on the Gates of the FETs blowing them up....
You have to use maths to work it out and go from there....
In reality you will never find resonance you just have to get close to it indicated by rising gate voltage....
Wayne
ua3ral:
возбудитель класса D 160 метров max9700
модулятор tpa3122