PDM Board/Parts Kits

[DMOD]

Does anyone know if the PM system works on AMFONE?

I need to commuicate with Steve Qix regarding an order.

Thanks

Phil

[kf1z]

Yes, it works....

But, he may not have it set to send him an email when he gets a PM...?

I would just email him if I were you....

cloutier@radioassociates.com

Bruce
kf1z

[DMOD]

Thanks Bruce,

I will be using a slightly different set of PDM switchers and RF switching transistors so I decided to use the PDM kit and modify it slightly.

I think I will take the standard 5.7 kHz filter and narrow it to 4.5 kHz.

Thanks

Phil

[DMOD]

Well, I received a failure notice saying it was rejected.

Phil

[kf1z]

That's weird...

That is the addy I use for him all the time....

you could try

cloutier@piesky.com

[kf1z]

Hi Phil,

Just curious what your going to use for FETs... and why?

Not that others won't work as good, but the IRFP260n is readily available at low cost, as are the FQA11N90 (both are less that $3.00 each)

Shouldn't have to modify much to accomodate other devices.

Just curious, that's all !


And, on the anti-aliasing filter, you probably already found the 5khz filter values here:
http://classeradio.com/easy_e_pwm_alternate_filters.pdf

just in case you didn't

[DMOD]

Yep, I sent messages there too after an initial contact through AMFONE PM system.

I sent the Paypal payment to ebaysteve@piesky.com.

I just want to make sure he received and acknowledged payment since the debit from the bank account is posted.

I will be using a collection of parts from IXYS such as DEIC420's, DE275-201N25A, DE275X2-102N06A, IXFH12N100F, etc.

I used these on a project (contract job) back in the summer and had a number of extra parts.

Thanks, I have the schematics for all anti-aliasing filters.

I wanted the PDM boards and components so that I could concentrate on the RF deck and Tuning deck. It willl certainly be an experiment with these parts since they're not part of the Reptoire of standard components you guys usually use.

[kf1z]

Ok Phil, I see...

Well the DEIC420 we used to use for drivers, and it worked well for 160/75 meters for up to 5 fqa11n90 each.

We've been using the ixdd414 drivers now, because they are so much cheaper, even though you need more of them....


By the way.... if you want to make the modulator simple, with no modification...( so you can work on the amplifier) I have IRFP260, and the IXYS diodes (DSEI30-06) and some other odds and ends, if you want to make a trade on some of those other IXYS parts (if you have "spares")

The DEIC420, and IXFH12N100F should make a dandy amplifier, without much fooling about from our usual design. No difference at all really.
The only experimentation would be layout, but that's just wide busses between mosfets/drivers.

Although, if you have any of the DE275 packages that have a high enough voltage rating (over 600volts) the DEIC420/ DE275 package "one on one" is a beautiful matchup, those packages are made to go together in RF service.

Anyhow, sounds like fun...... !

[DMOD]

Hi Bruce,

I have the PWM board up and runnig.

Without audio input, the PDM generator chip is running at 174 kHz with negative pulses of 0.25 us in width.

When audio is applied, the pulse widths change as would be expected. And 5v and 12V pulses can be selected.

Right now I am running the audio from my Heathkit Tube audio generator in the unbalanced mode, and audio looks good. I haven't swept the audio section with the anti-aliasing filter yet, but will shortly.

Of course, the Feedfoward voltage from the main PS has not been connected as yet.

I have the PDM driver completed except for the IRFZP260N fets. I would like to trade two IXYS DE150-501N04A for 5 IRFP260N's, if you have them and thnk it's a fair trade.

Cell is 319-270-1853

Question:

What is the average current one observes with and without audio for a completed rig with 5 PDM fets and 8 RF fets? And what voltages do you see at the output of the PDM two-section filter for quiescent conditions and 100% modulation?

Thanks

Phil - AC0OB

[kf1z]

Hi Phil,

Oh good, progress is being made!

I'll call, or email you on the trade...
I do have some IRFP260N.


You probably realize that with 5 IRFP260N in the output section, you'll be able to run about 1200 watts carrier, and modulate 150% + ?
Each mosfet/damper diode "pair" is good for 250watts carrier.
There is no need to populate that whole board, unless you need to have that much available power.


The current and voltage you see at the output of the filter, will, of course, depend on your DC supply voltage (no greater than 130vdc, if your following Steve's design with transzorbs etc..).
And the power output you intend to operate...

My output filter for the PWM was designed for a 5 ohm load, and I generally opperate my rig at 40 volts, 8 amps at carrier. (slightly under 300 watts RF output)
I use analog meters, so they basically do not change under modulation.. the current meters do wiggle a little under very heavy modulation (150% )

I'd have to say that for 100% modulation, those values are the average.
If you go above 100% (positive) modulation, it stands to reason your average voltage would be slightly higher. but you'd have to be looking at a scope to see it.


Don't know if that answers the questions or not!

Bruce

[DMOD]

Thanks Bruce,

Right, I realize the current and voltage are going to change with modulation and that analog meter's ballistics are slow. I figured if anyone had done some monitoring of I, V, you would be the one.

I wanted to know for comparison purposes so when my RF deck is completed, I can make comparisons.

As you know I will be using the IXYS DE275X2-102N06A mosfets driven by DEIC420s for the RF deck.

Talk to you later.

Thanks

Phil - AC0OB

[DMOD]

Bruce,

I corrected my phone number above. I apologize for that.

For the RF deck, I will use these bad boys:

http://www.ixysrf.com/pdf/switch_mode/d ... 02n06a.pdf

Each mosfet will be connected in an "each-device-parallel" configuration to give > 10A switching current @100C and will be the half-side switch for each leg
of the push-pull output circuit.

A DEIC420 driver will drive each device's Ciss 3600pF gate cap.

I plan on using a PS that has the capability to have a number voltages; say 35, 70, 111VDC for three or more tune/power settings. My BIL has given me a hefty power transformer with multiple secondaries.

Thanks

Phil - AC0OB

[kf1z]

Yes Phil...
I called the number you had origionally wrote... got no answer, but did get a call later in the day, wondering why I had called... oh well...

Ok on all... remember if you use the 111v tap on that transformer....

Is tha AFTER rectification/filtering..? I assume so, because you stated "DC"..

If so, you'll end up running a 40 volt carrier... that's ok...

And with 111vdc you'll see about 388 to 445 volts peak on the drains of the RF FETs.
So plenty of safety margin there.


So on those FETs... your going to parrallel the 2 fets in each package, and then use 4 of those on each module?

Or one of those in each module, giving you a total of 4 devices, in 2 packages...?

Anyhow...
I sent you a PM earlier , after I tried to call...

email is easier anyhow

kf1z@hughes.net

[DMOD]

I got a message but no text.

RE: PDM PCB - I will probably start off with two 260N devices but make accomodations for more devices on the heat sink strip for higher powers later on.

RF Deck: The two mosfets in each device module will be paralled to get the higher current in the on-state. The spec is 16 Amps at 25C or about 12 amps at 100C.

Each device module will then switch either T1 or T2.

Speaking of which, where do guys obtain your FB-43-1020 cores?

The voltages mentioned are the transformer RMS open circuit secondary voltages times 1.25.

I should be able to get 35, 70, and 95 volts VDC under load for starters. The Vds voltages should be about 3.86 X each of those, respectively.

For more powa, I may later try and obtain one of those toroidal power transformers. I prefer toroids, but hey, can't look a gift horse in the mouth!


Thanks

Phil - AC0OB

[kf1z]

Ok Phil,

If your Hv DC supply will only be 95vdc then (when the time comes) you will want to only run about 35v at carrier..

3.5 x the DC input is a good place for the peak Vdc at the drains to be And that will be determined for the most part, by the value of Shunt C.


The SB-43-1020 cores come from CWSBytemark

Here:

http://www.cwsbytemark.com/index.php?ma ... 06_219_234