Anyone know of any 1w exciters that don't sprog like fuck and don't cost over £100 ?
Iv tried the jpl995 ones but they are crap and don't amplify well. (I'm sure someone will probably say they will take down planes lol)

Don't even mind vfo as long as it's stable..

Why don't you build something yourself? If you can get the TDA1057 and a cheap PIC, you just need four cheap transistors, and you've got a 1 Watt PLL. If you need cookery instructions, I'll put them on here.

Hi Albert, instructions on how to build a 1w pll would be great. I build a lot of X band stuff at work so hopefully I can build it.
Thanks

Right.

The simplest is an "at frequency" exciter - the oscillator runs at the same frequency as the output. If you're going to do that, the exciter has to go into its own screening box, to prevent RF feedback which will cause wild instability. The big advantage is that there are no other frequencies involved, so there's not much to filter out, and there's no frequency multiplier stage that will require careful adjustment.

It's also sensible to separate the RF bits from the PLL digital bits with grounded screening.

Stephen at NRG used a half-frequency pair of oscillators, cross-coupled, so that they would "current rob" each other and automatically generate the second harmonic of the oscillators - inherent doubling, if you like. There were two advantages - a more stable oscillator (because of the lower frequency) and lower frequency samples for the PLL circuit, which used ICs with a maximum input frequency of 70 MHz. Stephen insisted on using standard ICs - no special PLL or PIC - but we're not so constrained these days. The big disadvantages were the ½f and 1½f breakthrough, which was more difficult to filter.

The simple "Pira" 1057 PLL is well known and easy to replicate. It uses a cheap (£1) PIC and a 4MHz crystal (20p). The oscillator and amplifier strip can be designed for no adjustments - no expensive trimmers and nothing to wrongly adjust!

I'll put some details up here later.

OldskoolPirate wrote:Anyone know of any 1w exciters that don't sprog like fuck and don't cost over £100 ?

Tugicom 1w units nearly meet that price point (pre-Brexit!) and have a good reputation:

http://www.tugicom.com/tx180.html

Having said that, mine produces quite a high second harmonic - not sure if that is a fault with my unit or design issue.

Tugicom don't seem to be big on harmonic filtering - their 800W pallet has 2nd harmonic only 15.4dBc - this means that the filter after this board will be dissipating a lot of heat!

Looking at their little TX180 exciter - the output filtering is pretty crude and there's no proper screening, so it will generate a lot of crap.

Yeh need some drawings and parts list. Would boxing up a jpl995 board do anything to stable it ?

Probably not. Those things look really nasty. Perhaps not quite "Pantek" or "Josty" nasty, but pretty bad!

Here you go: This is the 5 Watt board I used for many years. It was a good power level to drive big power FETs up to about a kilowatt. It was also clean enough to be used as a standalone 5 Watt rig.

It might be too complicated for some folks - I'll put something simpler up later - but this is a tried and tested no-tweak exciter:

So is that a 5w without pll ? How stable is it without ?

@Albert H possible to have a layout for the output stage to see how much can give at wideband
thanks

OldskoolPirate wrote:So is that a 5w without pll ? How stable is it without ?

Look at the labels to the external connections - it connects to a PLL. You can't really use it without. It has a control input to turn the drive off, which can come from the "locked" output of the PLL, so there's no output until the oscillator is correctly stabilised.

It needs to be built on a double-sided PCB, and the PLL should be screened from the RF part. The 2N4427 is running at about 500mW output, so is fairly cool, but it requires a small heatsink. The 2SC1971 must be bolted to a reasonable size heatsink to get rid of about 3 Watts of heat. I usually build these in small, low-profile Hammond diecast boxes, and use the box as the heatsink. The external power and modulation connections go through feedthrough capacitors, and the RF output is through an SMA connector.

No take-off for the PLL is shown, because it will differ according to the PLL devices used. I've tapped (through a low value capacitor) off the drain of the oscillator FET, and I've inductively coupled to the oscillator coil (works really well with the 5511).

There are three PLL circuits that I've used with these:

The simplest are the PLL IC & PIC solution - either with a pre-programmed 12F629, which is fixed frequency, or with a 16F84 or 16F628 for switched frequency selection. I've used several PLL ICs - the easiest to use are the TSA5511 or the TDA1057.

I've also used PLLs built from discrete logic ICs. These have the advantage that the parts are available anywhere in the world, from regular component suppliers, but the disadvantage that they're more complicated and physically bigger (and probably slightly more expensive). The discrete logic version gives the best spectral purity and is capable of very accurate and reliable locked / unlocked detection. I even use a phase comparator built from separate gates (rather than the integrated 4046 solution) since this approach gives more predictable and more reliable results.

The ferrites used in the exciter are important. They prevent the RF signals being coupled on to the supply rails and prevent RF feedback problems that would lead to instability. The output filter must be screened from everything else. If the construction is done following proper RF methods, the results are exceptionally good, and certainly clean enough for standalone 5W transmitter use, or as a drive for a big FET stage.

radium98 wrote:@Albert H possible to have a layout for the output stage to see how much can give at wideband
thanks

It's substantially flat from 85 - 110 MHz (to within 1.2dB) and will give a minimum of 5 Watts at the top end, and a bit more lower down. It was originally designed for the NRG PLL Pro IV which Stephen and I had begun to work on shortly before his death.

Albert H wrote:Here you go: This is the 5 Watt board I used for many years. It was a good power level to drive big power FETs up to about a kilowatt. It was also clean enough to be used as a standalone 5 Watt rig.

It might be too complicated for some folks - I'll put something simpler up later - but this is a tried and tested no-tweak exciter:

5W Exciter.jpeg

Albert what size are coils, I will make this. Thanks in advanced

Banus_radio wrote:

Albert H wrote:Here you go: This is the 5 Watt board I used for many years. It was a good power level to drive big power FETs up to about a kilowatt. It was also clean enough to be used as a standalone 5 Watt rig.

It might be too complicated for some folks - I'll put something simpler up later - but this is a tried and tested no-tweak exciter:

5W Exciter.jpeg

Albert what size are coils, I will make this. Thanks in advanced

Probably 1/4" or about 6.35mm. It's common for people to wind coils around something that is always lying on their bench, a trimming tool!

in my case its my bench drill chuck key hehe

All coils were 6mm diameter. LB made a run of the original boards with 7.2mm diameter coils (he used a screwdriver that was "about" the right size). Slight stretching and compression of the coils got them working just like the originals.

The turn spacing is the wire diameter - I used 18swg throughout, and just stretch the coils until the spacing looks right. They're surprisingly uncritical.

The PLL take-off point is either a 2-turn coil at the earthy end of the VCO coil or a 33p capacitor from the drain of the FET - according to the PLL IC you're using. I used to make the VCO coil 8 turns, with a grounded tap 2 turns up, and the source tap a further turn up - the PLL would then be fed from the "extra" 2 turns at the ground end of the coil. This worked really well with the TSA5511 PLL. If you're using the old 1057, the 33p capacitor is the way to do it.

LB did a run of boards with the PLL components on the bottom of the board, screened from the top RF components by the groundplane. This worked well with surface-mounted ICs. In this case, he pushed a 2-turn coil into the upper end of the VCO coil, and took one end through the board and soldered the other to the groundplane. These boards were a complete PITA to build, but very small when completed because he used mostly SM components. They used a PIC to control the 5511 and this had to be programmed with the required frequency through an RS232 port - you plugged the programming lead on to a pin header next to the PIC. It was a one-time deal - you couldn't change the frequency without de-soldering and replacing the PIC, running the right firmware.

The SM versions were very small, and we built a couple of 19" cases with eight exciters in each! These were fed composite baseband from dedicated FM receivers in the same rack. They were then used to repeat FM broadcasts into a Leaky Feeder down an underground railway network in Eastern Europe, giving FM coverage throughout.

layout ?I'll put something simpler up later

so are diecast aluminum boxes ok then? I was looking at ebay said they wheren't geniune proper aluminum, guess I was thinking they might just have a coating or something.

Nice work Mr Albert! I like it!
Mr northeast, i believe 'Diecast' refers to the process in which they are produced? They offer great shielding for RF, the only downside i know of is that they are not solderable unlike tin enclosures!
Albert, what is the sensitivity of your audio input?