What it takes to make broadcast modulation

[KD6VXI]

I have been playing with power monitoring here on the island.  At 60 to 65 cents a kilowatt, it's really an eye opener.

Currently have a Hermes SDR and an 1 x 8 MRF455 amp. Making 350 watts pep / 65 watts of carrier.

Receiving, my house is at appx 1.4kw of load.  220V single phase.

TX at carrier (65 watts) is  1880 watts.  440 watts of input  to make 65 watts of carrier.

Full pep, 330ish watts pep on a 2 tone dsb am signal, full carrier and 125 pct POS peaks.  2330 watts.

This is using a switching supply to power everything, all mrf455 but I do have this amp biased pretty hard, almost a full volt of dc on the base, key down no signal.  It's about 1.2 volts.

So, 480 watts to make a 65 watt carrier, 500 watts to make 330 pep.   Maybe 180 watts of avg power.  I don't have a Bird unpacked and the Palstar PM5k / Texas digital watter doesn't do 2 tone avg very well.

The AMM SD1 shows 99 pct neg peaks and 125 to 130 pct POS peaks.

I have pics to verify.

Just thought I'd show how inefficient AM broadcast can be when using solid state to amplify it.

--Shane
WP2ASS / ex KD6VXI

[KD6VXI]

Really makes me hesitant to throw the 3cx3000 in line.  REALLY makes me realize the 4x15 will never be used lol.

Unless, somehow, I can get AC power from work.   I have megawatt on tap!


--Shane
WP2ASS / ex KD6VXI

[Tom WA3KLR]

Hi Shane,
sorry to hear your electricity is so expensive. Personal solar arrays must be very popular there. Power here in southeastern Pennsylvania, I pay about 14.1 cents per kWhr plus $15.77 per month customer charge.

I assume you are running a linear amplifier. If you are going to run AM a lot you need a Class E PA with pulse width modulator; that's the highest overall efficiency system, should cut the input power down to a fourth.

[KD6VXI]

Yes, old amplifier I built back in high school.

My class E and associated stuff just got here Thursday.  I moved to the island 3 years ago and put everything in storage.  A year ago hired movers and my family moved down.

Movers left my entire storage unit!  Don't trust World Movers in Virginia or Orange County, CA!!!

So, I bought a truck and trailer last month, emptied my storage unit and brought it cross country to the port in Miami.  That was mine and my wife vacation this year.  Was really awesome as she'd not been out of California really before and we got to surprise her parents and then my son in school.

Anyway, yes, class E is the way and hopefully I'll have mine up soon!  And yup, solar is the way to go.  Soon as the house closes, I'll be putting some on.

--Shane
WP2ASS / ex KD6VXI