Ham Radio

Beko 2-meter Linear Amplifier

I have a solid-state Beko linear amplifier for 750 watts at 144 MHz. This has a built-in power supply that requires 220 vac and up to 5 amps max. How can this be used for portable ops? Where does the power come from?

At the time of writing (2015-06-06), I've successfully tested the power wiring. However, the Beko amp has an an internal fault in the antenna path.

Overview

  • Honda EU2000i Generator Pair
  • 110-to-220 step-up transformer
  • 220v extension cord
  • Beko 750 watt SSPA
  • Yaesu FT-897D

Estimated Power Budget

Here's a simple estimate of the expected maximum current requirements:

  • Assume Beko's rf output power is 750 watts
  • Assume Beko's efficiency is 0.5, so the input power is 1500 watts
  • Assume 1500 watts at 220vac, so the input current is 6.8 amps (the Beko's fuse is 6.3 amps)
  • Assume transformer's step-up ratio is 1:2, so the input current is 13.6 amps
  • Assume transformer's efficiency is 0.85, so its input current is actually 16 amps at 120 vac
  • Assume 16 amps at 120 vac, so the generator power required is 1920 watts

Therefore a single 2 KW generator will probably not have a comfortable safety margin. The load should be easily handled by a 4 kilowatt generator pair.

What about connector ratings? Note that standard 110 v 3-pin line connectors are stamped with a 10-amp rating.

Note the Honda generator's recepticals have "20A 125V rating", but the generator's inverter has 13.3A average current rating. This is significantly less than the estimated 16A requirement.

Honda EU2000i Generator Pair

Tilt over trailer hitch adapter

Since I usually travel and setup alone, the top requirements are size and weight. In addition, I really want low acoustic noise.

I examined several alternatives. However, all the various choices were too too heavy, too expensive, and took up too much valuable truck space.

Source: New cost at local Honda small-engine dealer was $2199 total.

I found a pair on Craigslist for $1400 including connecting cables.

Line Noise Filter

Initial tests had no problems with rf noise, without using a line filter. I can always add this later, if needed.

Later: There were no problems with rf noise.

110-to-220 Step-up Transformer

My linear amplifiers require 220 vac, but these Honda generators only produce 110, even when connected together. A step-up transformer is needed.

The transformer should be located near to the generators, so the extension cord will carry lower current at higher voltage. This will reduce the I2R losses. That is, resistive heating (I2R losses) mean that 2x voltage yields 0.5x current, which means 1/4 of the resistive energy loss.

My transformer is a Simran SMVS-3000 with meter, fuse, voltage regulator and stabilizer, rated for 3 Kva. This is a cheap Chinese device but I'm hopeful.

No Load Power Measurements made with "Kill A Watt P3" on wall outlet:

  • Input 119.7 vac yields Output = 217 vac
  • 110v Current = 0.43 amps
  • 110v Power = 38 watts
  • 100v Power factor = 0.74

Loaded with Beko amp plugged in, turned on, standby:

  • 110v Current = 0.64
  • 110v Power = 65 watts
  • 110v Power factor = 0.84

Loaded with Beko amp plugged in, turned on, not standby:

  • 110v Current = 0.64 (no change)
  • 110v Power = 65 watts (no change)
  • 110v Power factor = 0.84 (no change)

Source: Craigslist for $80 or Amazon for $95.

220v Extension Cord

Hitch tee-bar adapter

I bought a 50-foot yellow extension cord of 12-gauge 3-wire design.

I cut off the ends and connected NEMA L4-20P locking connectors. The current rating is overkill but I standardized on L4-20P throughout all my generator and 220v devices.

Since I have two linear amplifiers, there are two receptacles on the equipment end.

Source: Home Depot and many other hardware stores sell extension cords. This one was $65. Each NEMA L4-20P locking connector was about $19 each.

Beko 750 watt SSPA

Beko HLV-750 solid state 2m amplifier

Beko 750 watt SSPA s/n 051010

Frequency range: 144 - 146 MHz
Input power: 20 watts
Output power: 800 watts
1 dB compression point: 780 watts
Harmonics: -60 dB
Spurious: -70 dB
Return loss: 20 dB
Max SWR: 1 : 1.8
Supply voltage: 100 - 260 vac, 50/60 Hz
Temperature: -10 to 30° C
Dimensions: 300 x 168 x 470 mm
Weight: 13 kb

Conclusion

Barry's truck with generators and transformer at Road's End State Park

Outstanding. My first usage was in the 2015 ARRL June VHF Contest. The whole system ran superbly, it was trouble-free, and all the various parts worked smoothly and without complaint, and I received good signal reports. Nothing seemed to be loaded heavily or working hard.

SSB: The pair of generators didn't seem to notice the 750-watt SSB load. I could run this Beko with a single generator on voice.

CW: I could notice the pair of generators would throttle up slightly in response to CW keying. If I shut off one generator, it was working noticeably hard to respond to CW, but it would keep up and the amplifier was satisfied with the power source. Personally, I felt more comfortable using both generators together when operating CW.

 

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